MEfflCAL 


Gift  of 
Wallace  I,   Terry,   M.D 


DR.   CARPENTER'S  PHYSIOLOGICAL  WORKS. 


A  MANUAL,  OR  ELEMENTS  OF  PHYSIOLOGY, 
INCLUDING  PHYSIOLOGICAL  ANATOMY, 

.  FOR  THE  USE  OF  THE  MEDICAL  STUDENT. 

With  one  Hundred  and  Eighty  Illustrations.    In  one  octavo  volume  of  566  pages.    Elegantly 
printed  to  match  his  "Principles  of  Human  Physiology." 


A  POPULAR  TREATISE  ON  VEGETABLE  PHYSIOLOGY. 

r 
With  numerous  Illustrations  on  Wood.    In  one  neat  duodecimo  volume. 


(Preparing) 

PRINCIPLES  OF  GENERAL  AND  COMPARATIVE 
PHYSIOLOGY, 

INTENDED  AS  AN  INTRODUCTION  TO  THE  STUDY  OF  HUMAN  PHYSIOLOGY,  AND 
AS  A  GUIDE  TO  THE  PHILOSOPHICAL  PURSUIT  OF  NATURAL  HISTORY. 

With  numerous  Illustrations  on  Wood.    From  the  Third  London  Edition. 


(Preparing) 

PRINCIPLES    OF    ANIMAL    PHYSIOLOGY. 

With  about  Three  Hundred  beautiful  Illustrations  on  Wood. 


LEA    AND    BLANCHARD. 


PRINCIPLES 


OF 


HUMAN    PHYSIOLOGY, 

WITH  THEIR  CHIEF  APPLICATIONS  TO  PATHOLOGY,  HYGIENE,  AND 
FORENSIC  MEDICINE. 


BY 


WILLIAM  B.^CARPENTER,  M.D.,  F.R.S., 

FULLEEIAN  PROFESSOR  OF  PHYSIOLOGY  IN  THE  ROYAL  INSTITUTION  OF  GREAT  BRITAIN,  CORRESPONDING 
MEMBER  OF  THE  AMERICAN  PHILOSOPHICAL  SOCIETY,  AND  OF  THE 

NATIONAL  INSTITUTE  OF  THE  UNITED  STATES  J 

LECTURER  ON  PHYSIOLOGY  AT  THE  LONDON  HOSPITAL  MEDICAL  SCHOOL, 
ETC.  ETC. 


American,  from  tjje  last  2-ontion 

WITH  NOTES  AND  ADDITIONS, 

• 

BY 

MEREDITH  CLYMER,   M.D., 

CONSULTING  PHYSICIAN  TO  THE  PHILADELPHIA  HOSPITAL; 

LATE  PROFESSOR  OF  THE  PRINCIPLES  AND  PRACTICE  OF  MEDICINE,  AND  CLINICAL  MEDICINE,  IN  THE 

FRANKLIN  MEDICAL  COLLEGE,  PHILADELPHIA  J  FELLOW  OF  THE 

COLLEGE  OF  PHYSICIANS,  ETC.  ETC.  ETC. 


THREE  HUNDRED  AND  SEVENTEEN  WOOD-CUT  AND  OTHER  ILLUSTRATIONS. 


PHILADELPHIA: 
LEA    AND,  BLANCHARD. 

1847. 


Entered  according  to  Act  of  Congress,  in  the  year  1845,  by 

LEA   AND    BLANCHARD, 
in  the  Office  of  the  Clerk  of  the  District  Court  for  the  Eastern  District  of  Pennsylvania. 


PHILADELPHIA  : 
T.  K.  AND  P.  G.  COLLIN^  PRINTERS. 


TO 

WILLIAM  PULTENEY  ALISON, 

M.D.,  F.R.S.E.,  &c.&c. 

PROFESSOR  OF  THE  PRACTICE  OF  MEDICINE  OF  THE  UNIVERSITY  OF  EDINBURGH. 


MY  DEAR  SIR, 

I  take  the  liberty  of  inscribing  the  following  Work  to  you,  as  an  ex- 
pression of  my  grateful  remembrance  of  the  value  of  your  instructions, 
of  my  respect  for  those  intellectual  faculties  which  render  you  pre-emi- 
nent amongst  the  Medical  Philosophers  of  our  time,  and  of  my  admira- 
tion for  those  moral  excellencies  which  call  forth  the  warm  regard  of  all 
who  are  acquainted  with  your  character. 

In  many  parts  of  this  Treatise,  you  will  find  that  doctrines,  which  you 
have  long  upheld  in  opposition  to  almost  the  whole  Physiological  world, 
are  defended  with  such  resources  as  I  could  command;  and  that,  in 
many  instances,  such  convincing  evidence  of  their  truth  has  been  afforded 
by  recent  observations,  that  further  opposition  to  them  would  now  seem 
vain.  And  if  I  have  presumed  to  differ  from  you  on  some  points,  it  has 
been  in  the  spirit  of  that  independence  which  you  have  uniformly  encou- 
raged in  your  pupils;  yet  with  a  distrust  of  my  own  judgment,  wherever 
it  came  into  collision  with  yours. 

That  you  may  long  be  spared  to  be  the  ornament  of  your  University, 
and  the  honour  of  your  City,  is  the  earnest  wish  of, 

Dear  Sir, 

Your  obliged  Pupil, 

WILLIAM  B.  CARPENTER. 


EDITOR'S   PREFACE. 


THE  character  of  the  present  Work  is  too  well  known  and  established 
to  need  any  commendation.  Within  a  period  of  four  years,  it  has  passed 
through  three  editions  both  in  this  country  and  Great  Britain.  It  will 
be  seen,  upon  referring  to  the  Author's  Preface,  that  the  present  edition 
has  been  essentially  modified  and  improved ;  and,  besides  attentive  re- 
vision, has  undergone  material  alteration  in  the  arrangement. 

Many  of  the  Notes  of  the  American  Editor  to  former  editions  have 
been  incorporated  by  the  Author  in  the  text  of  the  present ;  others  remain ; 
whilst  such  additions  have  been  made,  as  the  progress  of  the  science 
required. 

By  the  liberality  of  the  Publishers,  the  Editor  has  been  enabled  to  add 
numerous  additional  illustrations ;  which,  accompanied  by  copious  refer- 
ences, will,  he  trusts,  be  found  to  enhance  the  value  of  this  edition,  and. 
to  peculiarly  adapt  it  to  the  Student  of  Physiology.  There  are  one 
hundred  and  fifteen  more  wood-cuts  in  this  than  in  the  third  English 
edition,  and  one  hundred  and  one  more  than  in  the  last  American. 

The  new  matter  added  by  the  American  Editor  is  in  smaller  type,  and 
is  distinguished  thus  [ — M.  C.]  The  new  cuts  are  included  between 
brackets  [  ].  M.  C. 

230.  Spruce  Street,  Philadelphia, 
September,  1847. 


PREFACE 


TO 


THE    TRIED    LONDON    EDITION. 


THE  Author  gladly  avails  himself  of  the  opportunity  afforded  him  by 
the  call  for  a  Third  Edition  of  the  following  work,  to  express  his  grateful 
acknowledgments  for  the  kind  reception  it  has  experienced,  both  in  this 
country  and  in  the  United  States.  The  rapid  sale  of  two  large  impres- 
sions on  each  side  of  the  Atlantic,  has  been  the  most  satisfactory  proof  that 
he  had  not  been  in  error  when  he  supposed  that  an  opening  existed  for 
an  additional  Treatise  on  Physiology,  notwithstanding  the  large  number 
of  those  already  before  the  public;  and  that  he  has  not  been  altogether 
unsuccessful  in  supplying  the  deficiency. 

The  present  Edition  has  not  only  undergone  a  very  careful  revision ; 
but  has  in  many  parts  received  large  additions,  and  has  been  in  many 
others  entirely  remodelled.  By  an  increase  in  the  size  of  the  page,  and  in 
the  proportion  of  small  type,  the  quantity  of  matter  has  been  augmented 
by  an  amount  equivalent  to  the  addition  of  fully  a  hundred  pages.  A 
considerable  number  of  new  wood  engravings,  of  first  rate  execution, 
have  also  been  introduced.  Many  of  these  are  from  original  drawings 
by  Mr.  Leonard. 

Among  the  principal  additions  will  be  found  a  Chapter  on  the  Varie- 
ties of  the  Human  Race ;  intended  to  convey  to  those,  who  have  not 
time  or  opportunity  to  peruse  Dr.  Prichard's  elaborate  treatises,  a  general 
view  of  his  arguments  and  conclusions.  The  account  of  the  Primary 
Tissues,  also,  which  was  formerly  included  in  the  Chapter  on  Nutrition, 
has  been  extended  in  a  degree  commensurate  with  the  Author's  estimate 
of  its  importance,  and  has  been  made  to  form  a  distinct  Chapter  nearer 
the  commencement  of  the  work.  Other  additions  and  changes,  which 
constitute,  when  taken  collectively,  no  inconsiderable  proportion  of  the 
entire  Treatise,  are  scattered  through  the  volume.  The  materials  of 
these  have  been  drawn  from  the  numerous  contributions  to  Physiological 
Science,  which  have  been  made  within  the  last  two  years,  and  from 


X  PREFACE. 

among  which  the  Author  has  endeavoured  to  select  the  most  import- 
ant and  the  most  stable  ; — not  rashly  introducing  changes  inconsistent 
with  usually-received  views ; — nor,  on  the  other  hand,  showing  an  un- 
willingness to  reject  the  statements  of  those  who  have  taken  much  pains 
to  arrive  at  accurate  conclusions.  He  trusts  that  he  may  be  found  to 
have  generally  exercised  a  sound  discretion,  both  as  to  what  he  has 
admitted,  and  what  he  has  rejected;  and  that  his  work  will  appear  to 
exhibit  on  the  whole,  a  faithful  reflection  of  the  present  aspect  of  Phy- 
siological Science.  He  cannot  venture  to  expect,  however,  that  he  has 
succeeded  in  every  instance,  so  that  each  of  his  readers  will  be  in  con- 
stant agreement  with  him ;  since  it  is  impossible  that  they  should  all 
survey  the  subject  from  the  same  point  of  view. 

Many,  however,  of  the  additions  and  alterations  scattered  through  the 
work,  are  the  result  of  the  Author's  own  investigations.  He  has  par- 
ticularly directed  his  attention  to  the  settlement  of  points,  which  ap- 
peared to  him  to  be  left  doubtful  by  others ;  and  hence  will  sometimes  be 
found  to  have  expressed  his  views  with  a  degree  of  confidence,  which 
the  evidence  adduced  by  them  may  scarcely  appear  to  warrant. 

The  Author  feels  called  upon  to  express  his  particular  obligations  to 
the  valuable  Reports  on  the  Progress  of  Anatomy  and  Physiology,  con- 
tributed by  Mr.  Paget,  to  the  British  and  Foreign  Medical  Review ;  and 
also  to  those  contained  in  the  Half- Yearly  Abstract,  edited  by  Dr.  Rank- 
ing. He  has  made  a  point,  however,  of  consulting  the  original  sources 
of  information  referred  to  in  these  Reports,  in  every  instance  in  which 
he  could  gain  access  to  them.  He  has  derived  much  assistance,  also, 
from  Dr.  Day:s  Reports  on  the  Progress  of  Chemistry,  published  in  the 
second  of  the  works  just  named ;  as  well  as  from  the  translation  of 
Simon's  Animal  Chemistry,  edited  by  the  same  gentleman. 

He  would  be  doing  injustice  to  his  own  feelings,  if  he  did  not  specially 
refer  to  the  admirable  "Anatomical  and  Pathological  Observations"  of 
Messrs.  Goodsir,  as  one  of  the  most  valuable  contributions  to  Physiolo- 
gical Science  which  has  been  made  since  the  date  of  his  former  Edition. 

The  subjoined  Extracts  from  the  First  Edition  will  explain  the  plan 
and  scope  of  his  Treatise  to  those  who  may  now  examine  it  for  the  first 
time. 

Stoke  Newington, 

October,  1846. 


FROM  THE 

PREFACE 

TO 

THE    FIKST    EDITION. 


THE  composition  of  such  a  Treatise  as  the  following  was  a  part  of  the 
original  plan  of  the  Author  when  he  first  came  before  the  Public  as  a 
writer  on  Physiology.  Being  desirous,  however,  of  making  his  first  essay 
in  the  path  which  had  been  previously  the  most  incompletely  explored, 
he  deemed  it  better  to  await  the  verdict  upon  this  before  proceeding 
further;  and  he  was  not  without  hope,  that  some  Writer,  more  fully  com- 
petent to  the  task,  might  in  the  meantime  take  up  the  subject  of  Human 
Physiology  in  such  a  way  as  to  leave  nothing  for  the  Student  to  desire. 
This,  however,  has  not  been  accomplished.  The  previously  existing 
Treatises  upon  it,  which  have  been  every  year  becoming  more  antiquated, 
have  not  been  replaced  by  any  works,  that  can  be  considered  as  at  the 
same  time  sufficiently  elevated  in  their  character,  to  represent  the  present 
condition  of  Physiological  Science, — sufficiently  compendious  in  their 
bulk  for  the  limited  time  at  the  disposal  of  most  Students, — and  suffi- 
ciently practical  in  their  tendency  to  lead  their  readers  to  the  useful 
applications  of  the  facts  and  principles  they  place  before  them.  This  is 
not  the  opinion  of  the  Author  alone,  but  that  of  numerous  experienced 
Teachers  throughout  the  country;  and  he  has  been  led  to  regard  the 
present  as  a  good  time  for  carrying  his  purpose  into  execution. 

The  plan  and  objects  of  his  Treatise  may  be  gathered  from  the  pre- 
ceding statement  of  the  reasons  which  have  occasioned  its  production. 
In  this,  as  in  his  previous  work,  it  has  been  his  object  to  place  the 
Reader  in  the  possession  of  the  highest  principles,  that  can  be  regarded 
as  firmly  established,  in  each  department  of  the  Science;  and  to  explain 
and  illustrate  these,  by  the  introduction  of  as  many  important  lacts  as 
could  be  included  within  moderate  limits.  In  every  instance,  he  has 
endeavoured  to  make  his  statements  clear  and  precise  without  being 
formal  or  dogmatical;  and  definite  enough  to  admit  of  practical  applica- 


Xll  PREFACE. 


tion  without  appearing  to  be  unimprovable  by  further  inquiry.  Physiology 
is  essentially  a  science  of  progress ;  and  it  must  happen  that  much  of 
v  kit  is  sirow  regarded  as  established  truth,  will  need  great  modification 
to  be  brought  into  accordance  with  the  results  of  new  inquiries.  It  is 
very  desirable,  therefore,  that  the  Student  should  not  be  made  to  think 
so  confidently  of  his  acquirements,  as  to  be  indisposed  to  receive  new 
information,  even  though  it  should  tend  to  diminish  their  value. 

The  present  Treatise  is  to  be  regarded  as  complete  in  itself,  and  as 
quite  independent  of  the  Author's  "  Principles  of  General  and  Compara- 
tive Physiology."  That  it  may  be  so  he  has  inserted  an  introductory 
chapter  on  the  "Place  of  Man  in  the  Scale  of  Being,"  and  numerous 
references  to  the  Comparative  Physiology  of  the  lower  Animals.  Still 
he  does  not  hesitate  to  express  the  opinion  that,  the  greater  the  amount 
of  the  Student's  previous  general  knowledge  of  the  Science,  the  better 
will  he  be  prepared  to  enter  upon  any  department  of  it,  especially  that 
peculiarly  complex  and  difficult  branch,  the  Physiology  of  Man.  On 
every  topic,  it  has  been  the  author's  aim  to  present  the  latest  and  most 
satisfactory  information  within  his  reach ;  and  he  believes  that  the  Volume 
contains  much  that  will  be  new  to  the  Physiologist,  whose  reading  has 
not  been  tolerably  extensive.  Its  materials  have  been  but  little  derived 
from  other  Systematic  Treatises  on  the  subject ;  and  it  will  not  be  found 
to  bear,  as  a  whole,  any  considerable  resemblance  to  those  already  Before 
the  public.  The  author  has  rather  endeavoured  to  bring  together  the 
valuable  facts  and  principles,  scattered  through  the  best  of  the  numerous 
Monographs,  that  have  been  recently  published  on  special  divisions  of 
Physiology  and  Medicine ;  and  to  reduce  these  disjecta  membra  to  that 
systematic  form,  which  they  can  only  be  rightly  made  to  assume,  when 
brought  into  relation  with  each  other,  and  shown  to  be  subservient  to 
principles  of  still  higher  generality.  In  regard  to  this,  as  to  his  former 
Treatise,  the  Author  believes  that  he  may  claim  a  somewhat  higher 
character  than  that  of  the  mere  Compiler ;  and  that  even  the  well-read 
Physiologist  will  find  in  it  many  facts  and  deductions,  which  have  not 
been  previously  brought  before  him  in  the  same  form. 

In  apportioning  the  amount  of  space  to  be  devoted  to  each  division  of 
the  subject,  the  Author  has  had  in  view  its  practical  relations,  much 
more  than  its  merely  scientific  interest;  and  he  has  on  this  account 
bestowed  a  much  larger  share  on  the  organs  of  Animal  life  than  some 
may  think  just  when  compared  with  the  narrow  limits  within  which  other 
important  topics  are  discussed.  But  he  has  endeavoured  to  keep  always 
in  view,  that  he  is  writing  for  the  guidance  of  the  Student  who  is  to  be- 
come a  Practitioner,  rather  than  for  him  who  makes  the  pursuit  of  Science 
his  professed  object;  and  that  much  that  is  of  the  highest  interest  to  the 


PREFACE.  Xlll 

latter  is  comparatively  valueless  to  the  former.  Hence  "many  topics  of 
great  scientific  interest  are  entirely  passed  over;  and  it  is  hoped  that 
such  omissions  will  not  be  accounted  as  faults  in  the  estimation  of  those, 
who  dread  lest  the  attention  of  the  Student  should  be  too  much  drawn  off 
by  the  seducing  novelties  of  Science,  from  his  less  attractive,  but  more 
important  objects. 

For  a  large  part  of  his  illustrations,  the  Author  is  indebted  to  the 
valuable  and  beautiful  Icones  Physiologicse  of  Prof.  Wagner.  He  has 
indicated  the  sources  of  all  which  are  not  original. 

In  conclusion,  the  Author  would  repeat  what  he  has  already  had  oc- 
casion to  state ; — that  in  a  work  involving  many  details,  it  is  not  to  be 
expected  that  no  error  should  have  crept  in ;  but  that  he  has  endeavoured 
to  secure  correctness,  by  relying  only  upon  such  authorities  as  appeared 
to  him  competent,  and  by  comparing  their  statements  with  such  general 
principles  as  he  considers  well  established.  For  the  truth  of  those 
principles,  he  holds  himself  responsible ;  for  the  correctness  of  the  details, 
he  must  appeal  to  those  from  whom  they  are  derived,  and  to  whom  he 
has  generally  referred.  He  hopes  that  he  will  not  be  found  unwilling  to 
modify  either,  when  they  have  been  proved  to  be  erroneous ;  nor  indis- 
posed to  profit  by  criticism,  when  administered  in  a  friendly  spirit. 

Bristol,  Feb.  1,  1842, 


TABLE  OF  CONTENTS 


•;       INTRODUCTION. 

i  PAGE 

NATURE  AND  OBJECTS  OF  PHYSIOLOGICAL  SCIENCE  -        :  (  »•  38 

CHAPTER  I. 

OX  THE  PLACE  OF  MAN  IN  THE  SCALE  OF  BEING. 

1.  Distinction  between  Animals  and  Plants               -             -             -             -  39 

,  2.  General  sub-divisions  of  the  Animal  Kingdom    -            -            -            -  41 

3.  General  characters  of  Radiata      ...  -42 

4.  General  characters  of  Mollusca    -  45 

5.  General  characters  of  Articulata  -             -            -             -     .        -             -  -48 

6.  General  characters  of  Vertebrata                           -  -         50 

7.  General  characters  of  Fishes        -            -            -            -'-            -  -        54 

8.  General  characters  of  Reptiles     -            -            •            •            •  55 

9.  General  characters  of  Birds          -            -            -             -                          i.-  •••        58 

10.  General  characters  of  Mammalia              ....           ,v.  •  ^  .         62 

11.  Chief  sub-divisions  of  Mammalia            ...  -        65 

12.  Characteristics  of  Man     -                                                  -  -        67 

CHAPTER  II. 

OF  THE  MUTUAL  RELATIONS  OF  THE  DIFFERENT  BRANCHES  OF  THE  HUMAN 

FAMILY. 

1.  General  Considerations    ---.----76 

2.  On  the  Discrimination  of  Species             -  •-     -   77 

3.  On  the  possible  Extent  of  Variation  within  the  limits  of  Species  ',  -  '      79 

4.  On  the  Extremes  of  Variation  among  the  Races  of  Men              -            -  -        81 

5.  On  the  value  of  ^Physiological  and  Psychological  peculiarities  as  specific  distinc- 

tions    -            -            -                        -                     -.  -  •*•        -            -  82 

6.  On  the  Comparative  Peculiarities  of  the  different  Races  of  Mankind       -  -        83 

7.  Of  the  Principal  Branches  of  the  Human  Family            -  -91 

CHAPTER  III. 

OF  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 

1.  On  Organized  Structures  in  General         ......        99 

2.  On  the  Original  Components  of  the  Animal  Fabric                                    •  •      102 

3.  Of  the  Elementary  Parts  of  Organized  Tissues; — Cells,  Membrane,  and  Fibre  •      108 

4.  Of  the  Simple  Fibrous  Tissues     •            -  "         -           -           ...  -      120 


XVI  CONTENTS. 

PAGE 

5.  Of  simple  Cells,  floating  in  the  Animal  Fluids   -                                                   -  124 

6.  Of  Cells  developed  upon  Free  Surfaces                -                                                     -  137 

7.  Of  the  Compound  Membrano-Fibrous  Tissues    -                                        -  147 

8.  Of  Simple  Isolated  Cells,  forming  Solid  Tissues  by  their  aggregation     -            -  150 

9.  Of  Tissues  consolidated  by  Earthy  deposit. — Bones  and  Teeth  -  -161 

10.  Of  Simple  Tubular  Tissues. — Capillary  Blood-vessels     -                                      -  188 

11.  Of  Compound  Tubular  Tissues. — Muscle  and  Nerve      -                                      J  192 

CHAPTER  IV. 

GENERAL  VIEW  OF  THE  FUNCTIONS. 

1.  Of  Vital  Actions,  and  their  mutual  dependence                                                      -  216 

2.  Functions  of  Vegetative  Life      -                                                                             -  224 

3.  Functions  of  Animal  Life                                                                                         -  232 

CHAPTER  V. 

FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

1.  General  Summary    v  236 

2.  Comparative  Anatomy  and  Physiology  of  the  Nervous  System  in  Invertebrata  247 

3.  Nervous  System  of  Vertebrata    -                                      ....  265 

4.  Functions  of  the  Spinal  Cord  and  its  Nerves. — Reflex  Action    -            -            -  285 

Respiratory  Movements               ...                         -  292 
Deglutition  and  Defecation          -            -            *            -            -297 

Movements  of  the  Genital  Organs           -            -                         -  305 

Protecting  Agency  of  the  Spinal  Cord     -                                      -  305 

Movements  of  Locomotion          -                         ...  307 

Influence  on  Muscular  Tension  -----  307 

Pathological  Phenomena                            -  ,                                   -  308 
Nerves  of  the  Spinal  System       -            -            -            -            -310 

5.  Of  the  Sensory  Ganglia  and  their  Functions. — Consensual  Movements  -             -  326 

Emotional  Actions           ....--  335 

Nerves  connected  with  the  Sensory  Ganglia       ...  339 

Consensual  Movements  of  the  Eye         -                         -            •  344 

6.  Functions  of  the  Cerebellum       -                                                                             -  349 

7.  Functions  of  the  Cerebrum          -                                      -                         -  357 

8.  General  Recapitulation,  and  Pathological  Applications  -                                      -  376 

CHAPTER  VI. 

OF  SENSATION,  AND  THE  ORGANS  OF  THE  SENSES. 

1.  Of  Sensation  in  General                                        -            -                         -  385 

2.  Sense  of  Touch                                                                  '•  395 

3.  Sense  of  Taste                                                                    ....  399 

4.  Sense  of  Smell                                                                                 -                         -  404 

5.  Sense  of  Vision               -                                                   -                         -  407 

6.  Sense  of  Hearing            -                         -                         -            -            -            -  422 

CHAPTER  VII. 

OF  MUSCULAR  CONTRACTILITY. 

1.  Of  Contractility  in  General         -           -           -  .        -           -                  :     -  438 


CONTENTS.  XVli 

PAGE 

2.  Of  Muscular  Irritability  -  ....        439 

3.  Of  Muscular  Tonicity     -             -             -            -             -  -             -            -.449 

4.  Energy  and  Rapidity  of  Muscular  Contraction   -  -         452 

CHAPTER  VIII. 

OF  THE  VOICE  AND  SPEECH. 

1.  The  Larynx,  and  its  Actions                    r  «."                                 455 

2.  Of  Articulate  Sounds       -  -        464 

CHAPTER  IX. 

INFLUENCE  OF  THE  NERVOUS  SYSTEM  ON  THE  ORGANIC  FUNCTIONS.         470 

CHAPTER  X. 

OF  FOOD  AND  THE  DIGESTIVE  PROCESS. 

1.  Sources  of  the  Demand  for  Aliment. — Hunger  and  Thirst  -                          -         477 

2.  Nature  and  Destination  of  the  Food  of  Animals  -            -         483 

3.  Of  the  Passage  of  Food  along  the  Alimentary  Canal      -  '   •         492 

Mastication 'and  Deglutition         -  -                      494 

Action  of  the  Stomach     -                          -  -         496 

Action  of  the  Intestinal  Tube      -  -         501 

Act  of  Defecation  -         502 

4.  Nature  of  Chymification  and  Chylification  -         503 

CHAPTER  XI. 

OF  ABSORPTION  AND  SANGUIFICATION. 

1.  Absorption  from  the  Digestive  Cavity     -  -                      509 

2.  Absorption  from  the  Body  in  general      -             -             -  -             -512 

3.  Of  the  Elaboration  of  the  Nutrient  Materials      -             -  -517 

4.  Composition  and  Properties  of  the  Chyle  and  Lymph    -  -         523 

5.  Physical  and  Vital  Properties  of  the  Blood         -  527 

6.  Pathological  Changes  in  the  Blood  -         535 

CHAPTER  XII. 

OF  THE  CIRCULATION  OF  BLOOD. 

1.  Of  the.  Circulation  in  General     -  ,- j       540 

2.  Action  of  the  Heart        -                                                  '  -  •»         546 

3.  Movement  of  the  Blood  in  the  Arteries  and  Capillaries  -                          -         556 

4.  Of  the  Venous  Circulation  >         566 

5.  Peculiarities  of  the  Circulation  in  different  Parts             -  -            -             -.    ~   568 


CHAPTER  XIII. 

OF  RESPIRATION. 

1.  Nature  of  the  Function ;  and  Provisions  for  its  Performance 

2.  Effects  of  Respiration  on  the  Air 

2* 


XV111  CONTENTS. 

PAGE 

3.  Effects  of  Respiration  on  the  Blood        -  -                                 586 

Exhalation  and  Absorption  by  the  Lungs  ...         589 

4.  Effects  of  Suspension  of  the  Respiratory  Process  ....         591 

CHAPTER  XIV. 

OF  NUTRITION. 

1.  General  Considerations. — Selective  Power  of  Individual  Parts  -  -         593 

2.  Varying  Activity  of  the  Nutritive  Processes       -  -            -            -            -         596 

Reparative  Operations         -            -  •            •         T   "•   -        "         *^ 

3.  Abnormal  Forms  of  the  Nutritive  Process          -     .  -         ...» .  "        -         604 

4.  Varying  Duration  of  Different  Parts  of  the  Organism  -                         •            •         609 

5.  Of  Death,  or  Cessation  of  Nutrition        -  •                                 612 

CHAPTER  XV. 

OF  SECRETION. 

1.  Of  Secretion  in  General  -         614 

2.  The  Liver. — Secretion  of  Bile     -                         •  618 

3.  The  Kidneys.— Secretion  of  Urine  -        632 

4.  Mammary  Gland. — Secretion  of  Milk     -  -         647 

5.  Salivary  Glands  and  Pancreas    -  ...         655 

6.  Lachrymal  Gland  -         657 

7.  The  Testis.— Spermatic  Fluid    -  -         657 

8.  Cutaneous  and  Mucous  Follicles                           -  661 

CHAPTER  XVI. 

GENERAL  REVIEW  OF  THE  NUTRITIVE  PROCESSES. ANIMAL  HEAT. 

1.  Review  of  the  Nutritive  Processes,  with  Practical  Ajtplications  -            -         671 

2.  Animal  Heat       -            -  -        676 

CHAPTER  XVII. 

OF  REPRODUCTION. 

1.  General  Character  of  the  Function                       -  -                         -        687 

2.  Action  of  the  Male          -  689 

3.  Action  of  the  Female     -  -         692 

4.  Development  of  the  Embryo       -  -                                                713 


APPENDIX. 

I.  ON  PHRENOLOGY  ...  .         731 

II.  ON  ARTIFICIAL  SOMNAMBULISM  AND  MESMERISM  -  -        733 


* 


.TLATLl 


EXPLANATION  OF  PLATES. 


PLATE   I. 

The  first  16  Figures  in  this  Plate  are  from  Dr.  Barry's  Embryological  Researches  in  the 
Philosophical  Transactions  for  1837,  1839  and  1840. 

FIG. 

1.  A  very  early  stage  of  the  formation  of  the  Ovum;  the  vesicles,  the  largest  of  which 

measures  only  1-1 12 5th  of  an  inch,  are  seen  in  the  midst  of  dark  granules  or 
globules  (§  906). 

2.  A  stage  somewhat  more  advanced ;  the  vesicles  are  surrounded  by  envelopes  of  smaller 

vesicles,  amongst  which  the  granules  are  still  seen  (§  906). 

3.  .A  still  later  stage ;  a  central  vesicle  a,  is  seen,  with  a  spot,  6,  upon  its  walls,  and  sur- 

rounded with  numerous  granules  ;  this  has  now  evidently  become  the  Germinal 
Vesicle  (§  906). 

4.  Ovisacs  from  Human  Ovum,  1-2 00th  of  an  inch  and  upwards,  in  diameter;  the  largest 

exhibits  the  Germinal  Vesicle,  a,  very  distinctly  (§  906). 

5.  Ovisac  from  Cat,  showing  its  contents  when  near  maturity ;  a,  ovisac ;  6,  its  contained 

granules;  c,zona  pellucida;  d,  granules  of  the  yolk;  e,  germinal  vesicle ;/,  germinal 
spot;  magnified  440  diameters  (§  905). 

6.  Ovum  of  Rabbit  at  the  periphery  of  the  Graafian  follicle,  with  part  of  the  membrana 

granulosa  removed;  g,g,  membrana  granulosa;  ov,  ovulum;  r,  retinacula  (§§  906, 
912). 

7.  Ovum  with  its  tunica  granulosa  and  retinacula,  removed  from  the  Graafian  follicle ;  a, 

germinal  vesicle;  6,  germinal  spot;  c,  zona  pellucida;  d,  globules  of  the  yolk;  r,r, 
retinacula;  f,g,  tunica  granulosa  (§  906). 

8.  Graafian  follicle  discharging  its  Ovum,  ou,  to  which  the  tunica  granulosa,  tg,  and  retina- 

cula, r,  r,  remain  attached  (§  912). 

9.  Ovarium  Ovum  in  preparation  for  fecundation:  a,  germinal  spot  beginning  to  resolve  it- 

self into  cells  at  its  margin;  6,  germinal  vesicle;  c,  elliptical  cells  in  the  place  of 
the  yolk ;  d,  zona  pellucida.  100  Diameters  (§§  915,  916.) 

10.  Ovum  nearly  ready  for  fecundation :  a,  germinal  spot  more  fully  developed  into  cells,  of 

which  concentric  layers  occupy  the  germinal  vesicle  b  ;  c,  elliptical  discs  or  cells ; 
rf,  zona  pellucida;  e,  outer  layer  of  cells  of  yolk  (§§  130,  915,  916). 

11.  Fecundated  Ovum  of  nine  hours;  the  germinal  vesicle,  having  returned  to  the  centre  of 

the  ovum,  is  concealed  by  the  large  elliptical  discs,  which  fill  the  cavity  of  the 
zona  pellucida  (§  916). 

12.  Plan  of  one  of  these  discs  or  cells:  its  nucleus,  a,  has  developed  itself  into  concentric 

rings  of  cells:  and  in^the  most  fully  developed  of  these,  the  nucleus,  b,  is  seen  to 
be  commencing  the  same  kind  of  evolution.  In  the  centre  of  the  original  nucleus, 
a  pellucid  spot,  the  nucleolus  of  Sch  wann  and  Schleiden,  is  observed  (§§  130,  916). 


XX  EXPLANATION  OF  PLATES. 

Fie. 

13.  Ovum  from  the  Uterus,  measuring  about  1-6 8th  of  an  inch  in  diameter:  a,  pair  of  cells 

now  occupying  the  greater  part  of  the  germinal  vesicle  6;  c,  zona  pellucida ;  d, 
chorion,  a  new  envelope,  separated  from  the  last  by  the  fluid  it  has  absorbed 
(§§  130,  917). 

14.  Ovum,  of  which  the  essential  part,  a,  the  pair  of  cells  occupying  the  germinal  vesicle, 

has  advanced  farther  than  in  the  last  case;  the  other  contents  of  the  germinal 
vesicle  have  undergone  liquefaction.  The  chorion  is  here  incipient;  and  the  re- 
mains of  the  cells  of  which  tit  is  composed  are  seen  at  cho  (§§  130,  918). 

15.  More  advanced  ovum;  the  cavity  of  the  germinal  vesicle  filled  with  cells,  a,  that  have 

originated  in  the  two  represented  in  the  last  figure;  these  cells  have  nuclei,  6, 
which  are  undergoing  a  corresponding  process  of  evolution  into  secondary  cells;  c 
and  d  as  in  Fig.  13  (§§  130,  935). 

16.  Ovum  in  a  state  rather  more  advanced;  a,  central  cell  of  the  germinal  mass,  now  come 

to  the  surface,  and  showing  the  nucleus  b  with  a  pellucid  centre,  from  which  most 
of  the  embryonic  structures  are  developed ;  c,  cavity  in  the  germinal  mass,  caused 
by  the  approach  of  its  peripheral  cells  to  the  enclosing  membrane,  d  (§§  935,  936). 

17.  Formation  of  the  Membrana  Decidua;    a,  a,  a,  interfollicular  substance  of  the  mucous 

membrane  of  the  uterus ;  6,  cavities  of  the  follicles ;  c,  uterine  vessels  prolonged 
into  the  decidua  and  forming  loops.  After  Baer  (§  919). 

18.  Human  Spermatozoa;  a,  seminal  granules.     After  Wagner  (§  902). 

19.  Cyst  of  evolution.     After  Wagner  (§  902).  .      , 

20.  Capsular  bundle  of  Spermatozoa,  just  previous  to   their  separation.     After  Wagner 

(§902). 

21.  Globules  from  the  Chyle;  a,  ordinary  globules;   6,  a  globule  (cytoblast  ?)  surrounding 

itself  with  an  envelope  (a  forming  cell?);  c.  minute  molecules  of  chyle;  d,  a 
colourless  corpuscle  from  the  blood.  After  Wagner  (§§  692,  693). 

22.  Particles  of  Blood  undergoing  multiplication:  a,  b,  cyd, e,  successive  stages.     After  Barry 

(S  148). 

23.  Extremity  of  one  of  the  tufts  of  fostal  vessels  forming  the  Placenta;  this  includes  (like 

a  branchial  tuft)  an  artery  and  vein.     After  Reid  (§  922). 

24.  Plan  of  the  structure  of  the  Placenta,  according  to  Dr.  J.  Reid's  view  of  it ;  a,  a,  portion 

of  substance  of  uterus ;  6,  i,  6,  6,  section  of  uterine  sinuses,  some  of  them  opening 
on  the  inner  surface  into  the  cavity  of  the  placenta;  c,  curling  artery  of  uterus ;  d,  rf, 
ramifications  of  fetal  vessels,  some  of  them  sending  down  prolonged  tufts  which 
dip  into  the  uterine  sinuses  (§  923). 


PLATE  II. 

25.  Uterine  Ovum  of  Rabbit,  showing  the  Area  Pellucida,  with  the  annular  nucleus  of  the 

embryonic  cell  (Fig.  14,  6)  now  elongated.  In  the  clear  space  enclosed  by  this  is  a 
well-marked  dark  groove,  occupying  the  position  in  which  the  nervous  centres  are 
subsequently  to  be  developed.  The  cephalic  extremity  of  this  is  already  rounded 
and  the  caudal  extremity  pointed.  After  Bischoff  (§  937). 

26.  More  advanced  ovum,  showing  the  incipient  formation  of  the  Vertebral  column;  and 

the  dilatation  of  the  primitive  groove  at  its  anterior  extremity.  After  BischorT 
(§  937). 


PLATE  Z. 


Fit  27 


EXPLANATION  OF  PLATES.  XXI 

PIff. 

27.  More  advanced  embryo,  seen  on  its  ventral  side,  and  showing  the  first  development  of 
the  Circulating  apparatus.  Around  the  Vascular  Area  is  shown  the  terminal  sinus, 
o,  a,  a.  The  blood  returns  from  this  by  two  superior  branches,  6,  6,  and  two  infe- 
rior, c,  c,  of  the  omphalo-meseraic  veins,  to  the  heart,  <?;  which  is,  at  this  period,  a 
tube  curved  on  itself,  and  presenting  the  first  indication  of  a  division  into  cavities. 
The  two  aortic  trunks  appear,  in  the  abdominal  region,  as  the  inferior  vertebral 
arteries,  e,  c;  from  which  are  given  off  the  omphalo-meseraic  arteries,  /,/,  which 
form  a  network  that  distributes  the  blood  over  the  vascular  area.  In  the  cephalic 
region  are  seen  the  anterior  cerebral  vesicles,  with  the  two  ocular  vesicles,  g.  After 
Bischoff(§938). 


LIST  OF  WOOD-ENGRAVINGS. 


FIG.  PAGE 

1.  Structure  of  the  Star-fish,  after  Tiedemann         -  43 

2.  External  aspect  of  Aplysia,  after  Rang 

3.  Structure  of  Aplysia,  after  Cuvier  47 

4.  Section  of  Cockchafer,  after  Strauss-Durckheim  -  50 

5.  Comparative  view  of  base  of  Skull  of  Man,  and  of  Orang-Outan,  after  Owen  -  68 

6.  Comparative  view  of  the  Skeletons  of  Man  aud  the  Orang,  after  Owen  71 

7.  Views  of  Prognathous  Skull,  after  Prichard        •>  86 

8.  Views  of  Pyramidal  Skull,  after  Prichard  87 

9.  View  of  Oval  Skull,  after  Prichard 

10.  Fibrous  structure  of  Exudation-membrane,  after  Gerber  -  107 

11.  Fibrous  membrane  from  the  Egg-shell      -  -  -  107 

12.  Simple  Isolated  Cells,  containing  reproductive  Molecules  -  110 

13.  Cells  of  Zygnema,  showing  spiral  arrangement  of  nuclear  particles,  after  Hassall  110 

14.  Cells  of  Pelargonium,  showing  stellate  prolongations  of  nuclei  -  -  -  111 

15.  Haematococcus  binalis,  in  various  stages  of  development,  after  Hassall  -  -  111 

16.  Coccochloris  cystifera,  in  various  stages  of  development,  after  Hassall  -  -  111 

17.  Haematococcus  sanguineus,  in  various  stages  of  development,  after  Hassall        -  112 

18.  Nostoc  macrosporum,  in  two  states,  after  Hassall 

19.  Section  of  branchial  Cartilage  of  young  Tadpole,  after  Schwann 

20.  Endogenous  cell-growth  in  cells  of  a  meliceritous  tumor,  after  Goodsir  - 

21.  Colorless  cells  with  active  molecules  and  fibres  of  fibrine,  after  Addison  -  118 

22.  Arrangement  of  Fibres  in  Areolar  Tissue 

23.  White  Fibrous  Tissue,  from  Ligament    - 

24.  Yellow  Fibrous  tissue,  from  Ligamentum  nuchse  of  Calf  -  122 

25.  Elements  of  Areolar  Tissue,  after  Todd  and  Bowman    - 

26.  Development  of  Areolar  Tissue,  after  Schwann  •  122 

27.  Red  Corpuscles  of  Human  Blood,  after  Donne  -  -  124 

28.  Red  Corpuscles  of  Frog's  Blood,  after  Wagner    -  -  125 

29.  Production  of  Red  Corpuscles  in  Chick,  after  Wagner     -  -  -  -  129 

30.  Small  Venous  Trunk,  from  web  of  Frog's  foot,  after  Wagner      - 

31..  Vertical  Section  of  Epidermis,  after  Wilson        -  -         137 

32.  Choroid  Epithelium,  with  pigment  cells,  after  Todd  and  Bowman          -  -         139 

33.  Cells  of  Pigmentum  Nigrum 

34.  Section  of  the  nail  and  its  matrix,  after  Todd  and  Bowman       -  -         140 

35.  Hairs  of  Sable  and  Musk-Deer   -  -         141 

36.  Hair  and  hair  follicles  seen  in  section,  after  Todd  and  Bowman  -  -         141 

37.  Structure  of  Human  Hair,  after  Wilson  -  -  -  -         142 

38.  Pavement-Epithelium-cells  •         144 

39.  Ciliated  Epithelium 

40.  Examples  of  Cilia,  after  Todd  and  Bowman      -  -  145 

41.  Secreting  Follicles  from  the  Liver  of  Crab  •         146 

42.  Capillary  Network  of  Skin,  after  Berres 

43.  Capillary  Network  of  Intestinal  Villi,  after  Berres 

44.  Capillary  Network  of  Mucous  Membrane,  after  Berres  - 

45.  Diagram  of  the  Structure  of  Mucous  Membrane,  after  Todd 

46.  Extremity  of  Intestinal  Villi,  after  Goodsir 

47.  Secreting  Cells  of  Human  Liver,  after  Bowman 

48.  Shape  of  Fat  Vesicles  in  close  pressure,  after  Todd  and  Bowman 

49.  Cells  of  Adipose  Tissue  ... 

50.  Blood  Vessels  of  Fat,  after  Todd  and  Bowman  - 


XXIV  LIST  OF  WOOD-ENGRAVINGS. 

"«•                                                                             •  PAG* 

51.  Fat  Vesicles  from  an  emaciated  subject,  after  Todd  and  Bowman        -  -  154 

52.  Section  of  Branchial  Cartilage  of  Tadpole,  after  Schwann        -             -  155 
v  53.  Section  of  Fibro-Cartilage                                    -                         -  -  155 

54.  Ampullary  Loops  of  Vessels  of  Cartilage,  after  Toynbee                     —  -  1 57 

55.  Nutrient  Vessels  of  Cartilage,  after  Toynbee      .....  157 

56.  Nutrient  vessels  of  the  Cornea,  after  Toynbee  -  -  •  -158 

57.  Vertical  section  of  Sclerotica  arid  Cornea,  after  Todd  and  Bowman      -  -  158 

58.  Tubes  of  the  Cornea  of  an  Ox,  injected,  after  Todd  and  Bowman        -  -  159 

59.  Calcified  Areolar  Structure  from  shell  of  Echinus         -             -             -  -  161 

60.  Cellular  Membrane  from  Shell  of  Pinna            -            -             -             -  -  161 

61.  Section  of  Bone                                        ......  J62 

62.  Transverse  section  of  a  long  Bone,  after  Todd  and  Bowman    -  -  163 

63.  Transverse  section  of  a  Tibia,  after  Tomes      -  -.163 

64.  Lacunae  of  Osseous  Substance  -  163 

65.  Haversian  canals  in  a  long  Bone,  after  Todd  and  Bowman       -  164 

66.  Section  of  Cartilage  at  Seat  of  Ossification,  after  Wilson  -  168 

67.  Vertical  section  of  Cartilage,  after  Todd  and  Bowman  -  168 

68.  Scapula  of  a  Foetus,  showing  the  process  of  ossification,  after  Tomes  -  -  170 

69.  Longitudinal  section  of  an  Incisor  and  Molar  Tooth     -  174 

70.  Vertical  section  of  an  adult  Bicuspid    -  174 

71.  Vertical  Section  of  an  imperfectly  developed  Incisor                -  -  174 

72.  Hexagonal  terminations  of  Fibres  of  Enamel,  after  Retzius     -  -  174 

73.  Fibres  of  Enamel  viewed  sideways,  after  Retzius        -  -  175 

74.  Vertical  section  of  Bicuspid  highly  magnified  -                           -  -  175 

75.  Most  interior  portion  of  Main  Tubes  of  Dental  Bone   -  175 

76.  Ramifications  of  the  Main  Tubes  of  Dental  Bone        -  -  175 

77.  Transverse  section  of  Crown  of  Bicuspid,  highly  magnified     -  -176 

78.  Position  of  the  Main  Tubes  near  the  Root  of  Bicuspid  -  176 

79.  Sections  of  a  Human  Incisor,  highly  magnified,  after  Todd  and  Bowman  -  176 

80.  Transverse  sections  of  Tubules  of  Dentine,  after  Todd  and  Bowman   -  -  177 

81.  Oblique  Section  of  Dentine,  after  Owen  -  177 

82.  Vessels  of  Dental  Papilla,  after  Berres  -  180 

83.  Diagram  of  development  of  Dentine,  after  Owen         -                          -  -  180 

84.  Inner  surface  of  cap  of  dentine,  after  Owen    -  -  181 

85.  Formation  of  Enamel,  after  Owen        -  182 

86.  Formation  of  the  Cementum,  after  Owen         -  -  182 

87.  First  stage  of  Formation  of  Teeth,  after  Goodsir                        -  -  183 

88.  Diagram  illustrating  subsequent  stages  of  formation  of  Teeth,  after  Goodsir    -  183 

89.  Do.                                 do.                                 do.                    after  Goodsir     -  184 

90.  Capillary  network  in  Frog's  foot,  after  Wagner 

91.  Capillary  vessels  from  pia  mater,  after  Henle  -  -  190 

92.  Formation  of  capillaries  in  germinal  membrane,  after  Wagner              -  -  191 

93.  Fasciculus  of  fibres  of  Voluntary  Muscle,  after  Baly    -  -  193 

94.  Portion  of  Human  Muscular  Fibre,  separating  into  disks,  after  Bowman  -  193 

95.  Cleavage  of  Striped  Elementary  Fibres            -  -  194 

96.  Muscular  Fibre  broken  across,  showing  Myolemma,  after  Bowman      -  -  194 

97.  Transverse  Section  of  Muscular  Fibres  of  Teal,  after  Bowman  -  196 

98.  Fragment  of  Muscular  Fibre  from  Heart  of  Ox,  after  Bowman  -  197 

99.  Structure  of  ultimate  fibrillae  of  striated  Muscular  Fibre  -  197 

100.  Muscular  fibre  of  Dytiscus,  contracted  in  the  centre,  after  Bowman      -  -  198 

101.  Muscular  fibre  of  Skate,  in  different  stages  of  contraction,  after  Bowman  -  199 

102.  Attachment  of  Tendon  to  Muscular  Fibre  in  Skate,  after  Bowman       -  -  200 

103.  Non-striated  Muscular  Fibre,  after  Bowman     -                                        -  200 

104.  Do.  showing  nodosities,  after  Wilson      • 

105.  Muscular  Fibres  from  Fcetus,  after  Bowman    ...  202 

106.  Do.  treated  with  tartaric  acid,  after  Wilson 

107.  Capillary  network  of  Muscles,  after  Berres 

108.  Terminating  loops  of  Nerves  in  Muscles,  after  Burdach  -  204 

109.  Structure  of  Sympathetic  Ganglion,  after  Valentin        -             -  -  205 

110.  Diagram  of  Tubular  Fibre  of  a  Spinal  Nerve,  after  Todd  and  Bowman 

111.  Structure  of  Nerve-tubes,  after  Wagner 

112.  Primitive  fibres  and  ganglionic  globules  of  human  brain,  after  Purkinje  -  208 

113.  Nerve-vesicles  from  the  Gasserian  ganglion,  after  Todd  and  Bowman  -  209 

1 14.  Caudate  nerve-vesicles  from  the  cerebellum  and  cord,  after  Todd  and  Bowman  2 10 


LIST  OF  WOOD-ENGRAVINGS.  XXV 


FIG. 

115.  View  of  piece  of  Otic  ganglion  of  sheep,  after  Valentin                                     -  210 

116.  Two  views  of  the  vesicular  and  fibrous  matter  of  the  cerebellum,  after  Todd 

and  Bowman  -  -  -  -  -  -  -  -211 

117.  Vesicular  and  fibrous  matter  in  the  Gasserian  ganglion,  after  Todd  and  Bowman  211 

118.  Primitive  Fibres  and  ganglionic  globules,  after  Wagner  -  -211 

119.  Distribution  of  tactile  nerves  in  skin,  after  Gerber         -             -             -             -  212 

120.  Terminal  loops  of  nerve  in  the  pulp  of  a  tooth,  after  Valentin                           -  213 

121.  Capillary  network  of  nervous  centres,  after  Berres        -  214 

122.  Capillary  loops  in  skin  of  finger,  after  Berres    -                                                      -  214 

123.  Stages  of  the  development  of  nerve,  after  Schwann      -                                       -  215 

124.  Nervous  system  of  Solen,  after  Blanchard,        ...                          -  251 

125.  Nervous  system  of  Aplysia,  after  Cuvier           -                                                    -  ,  254 

126.  Nervous  system  of  larva  of  Sphinx  ligustri,  after  Newport       -             -             -  256 

127.  Portion  of  ganglionic  tract  of  Polydesmus,  after  Newport          -                           -  257 

128.  Parts  of  Nervous  System  of  Articulata,  after  Newport                                        -  259 

129.  Stomato-gastric  system  of  Gryllotalpa  vulgaris,  after  Brandt      ...  261 

130.  A  View  of  the  Great  Sympathetic  Nerve          -  267 

131.  Roots  of  a  dorsal  Spinal  Nerve,  after  Todd  and  Bowman          -                          -  268 

132.  Nervous  centres  in  Frog,  after  Leuret   ...                           -  270 

133.  Transverse  sections  of  Spinal  Cord  at  different  points,  after  Solly         -  •  .          -  271 

134.  Structure  of  the  Spinal  Cord,  after  Stilling         -  272 

135.  Connection  of  nerve-roots  with  the  Spinal  Cord,  after  Stilling  -  272 

136.  A  posterior  superior  view  of  the  Pons  Varolii,  Cerebellum,  &c.                           -  '  275 

137.  An  anterior  view  of  the  Medulla  Oblongata,  after  Todd  and  Bowman              -  275 

138.  A  posterior  view  of  the  Medulla  Oblongata,  after  Todd  and  Bowman               -  275 

139.  Transverse  section  of  the  Medulla  Oblongata,  after  Stilling      -             -             -  276 

140.  Course  of  the  Motor  tract,  after  Sir  C.  Bell        -                           -             -             -  277 

141.  Course  of  the  Sensory  tract,  after  Sir  C.  Bell     .....  278 

142.  Analytical  diagram  of  the  Encephalon,  after  Mayo       ....  279 

143.  Brains  of  Fox-shark,  Cod,  and  Pike,  after  Leuret                                       -             -  281 
.144.  Human  Embryo  of  6th  week,  showing  rudiments  of  Brain,  after  Wagner        -  282 

145.  Brain  of  Turtle,  after  Solly       -             -             -             -             -             -             -  283 

146.  Brain  of  Buzzard,  after  Leuret               -                          -            -             -             -  283 

147.  Brain  of  Human  Embryo  at  12th  week,  after  Tiedemann  ~    -             -             -  284 

148.  Brain  of  Squirrel  laid  open,  after  Solly              -                                                    -  284 

149.  Upper  and  under  surface  of  Brain  of  Rabbit,  after  Leuret         -                           -  285 
,150.  Diagram  of  the  distribution  of  the  Fifth  Pair    -  311 

151.  A  view  of  the  distribution  of  the  Trifacial  nerves         -             -             -             -  312 

152.  A  view  of  the  Third,  Fourth,  and  Sixth  Pairs  of  nerves                        -  313 

153.  Diagram  of  the  distribution  of  the  Seventh  Pair            -             -             -  314 

154.  Diagram  of  the  distribution  of  the  Eighth  Pair             -             -            -  315 

155.  A  view  of  the  distribution  of  the  Glosso-Pharyngeal,  Pneumogastric  and  Spinal 

Accessory  Nerves,  or  Eighth  Pair  -                                                                 -  316 

156.  A  view  of  the  course  and  distribution  of  the  Hypoglossal,  or  Ninth  Pair          -  324 

157.  Base  of  the  Cerebrum  and  Cerebellum  with  their  nerves         -             -             -  327 

158.  A  view  of  the  Optic  nerve  and  the  origins  of  seven  other  pairs           -             -  340 

159.  Plan  of  the  optic  tracts  and  nerves,  after  Todd  and  Bowman  -                           -  342 

160.  Course  of  Fibres  in  the  Chiasma,  after  Todd  and  Bowman      -                          -  342 

161.  Origin  and  distribution  of  the  Portio  Mollis  of  the  Seventh  Pair,  or  Auditory 

Nerve         ...                         .....  343 

162.  Capillary  network  at  margin  of  lips,  after  Berres                       -                          -  396 

163.  Dorsal  surface  of  the  Tongue,  from  Soemmerring          -             -                          -  399 

164.  Simple  papillae  near  the  base  of  the  tongue,  after  Todd  and  Bowman  -             -  400 

165.  Vertical  section  of  one  of  the.circumvallate  papillae,  after  Todd  and  Bowman  400 

166.  Compound  and  simple  papillae  of  Foramen  Ccecum,  after  Todd  and  Bowman  400 

167.  Capillary  network  of  fungiform  papilla  of  tongue,  after  Berres                           -  401 

168.  Fungiform  papilla  with  its  simple  papillae  and  vessels,  after  Todd  and  Bowman  401 

169.  Forms  of  the  conical  or  filiform  papillae,  after  Todd  and  Bowman         -            -  401 

170.  \  A'  ^ecti°n  °f  f^°;m  and  fu,ngiform  PaPill£e     I  after  Todd  and  Bowman     -  402 
£  B.  Structure  of  filiform  papillae                            5 

171.  Nerves  of  the  papillae  of  the  tongue,  after  Todd  and  Bowman 

172.  Distribution  of  Olfactory  nerve  on  Septum  Nasi            ...            -  405 

173.  Longitudinal  section  of  globe  of  the  eye                                     •                         -  40* 

174.  Horizontal  section  of  the  eyeball 

3 


XXVI  LIST  OF  WOOD-ENGRAVINGS. 

FIG.  PAGE 

175.  Outer  surface  of  retina  of  Frog,  after  Treviranus          -                          -             -  412 

176.  Capillary  network  of  retina,  after  Berres                        -                                        -  412 

177.  A  portion  of  the  retina  of  an  Infant,  magnified                                                      -  412 
178.-  Vertical  section  of  the  Human  retina  and.  Hyaloid  membrane,  after  Todd  and 

Bowman     -                           -                                        ....  413 

179.  Membrane  of  Jacob,  after  Jacob                         -             -             -  413 

180.  General  section  of  the  Ear,  after  Scarpa           .....  433 

181.  Diagram  of  the  Inner  wall  of  Tympanum,  after  Todd  and  Bowman    -             -  424 

182.  Axis  of  Cochlea  and  Lamina  Spiralis    -  -  -  -  -  -425 

183.  Cochlea  of  a  new-born  Infant,  after  Arnold       -             -             -             -             -  425 

184.  Section  of  the  Cochlea,  after  Breschet  -                          ....  426 

185.  Papillae  of  Auditory  nerve  on  spiral  lamina  of  cochlea  of  young  mouse           •  426 

186.  Auditory  nerve  taken  out  of  the  cochlea                         -  426 

187.  Magnified  view  of  the  Lamina  Spiralis                                                                   -  427 

188.  Plexiform  arrangement  of  cochlear  nerves,  after  Todd  and  Bowman  -             -  427 

189.  Soft  parts  of  the  Vestibule        -                                                                -  428 

190.  Ampulla  of  the  External  Semicircular  Membranous  Canal       -  428 
-191.  Labyrinth  laid  open,  after  Breschet       -                           -                                        -  433 

192.  Labyrinth  of  the  Left  Side        -                                                   ...  434 

193.  Left  Ear  in  its  natural  state       -             -                                     -s  -  435 

194.  Anterior  view  of  the  External  Ear,  Meatus  Auditorius,  &c.      -             -             -  435 

195.  External  and  Sectional  views  of  the  Larynx,  after  Willis          -                          -  456 

196.  Bird's-eye  view  of  Larynx  from  above,  after  Willis      -                                        -  457 

197.  Diagram  of  the  direction  of  the  muscular  forces  of  the  Larynx,  after  Willis     -  458 

198.  Artificial  Glottis,  after  Willis     .......  461 

199.  View  of  the  Organs  of  Digestion  in  their  whole  length                          -             -  493 

200.  Muscles  of  the  Tongue,  Palate,  Larynx  and  Pharynx  -                                        -  495 

201.  Front  view  of  the  Stomach  distended  -                          -             -             -  499 

202.  Interior  of  the  Stomach              ...                           .                          .  499 

203.  Interior  of  the  Stomach  and  Duodenum             -                                                   -  500 

204.  Commencement  of  Lacteal  in  Villus.  after  Krause                                    -             -  510 


205.  Vessels  of  Intestinal  Villus  of  Hare,  after  Dollinger 

206.  Do.  Do.  of  Man,  after  Krause 

207.  Diagram  of  Lymphatic  Gland,  after  Goodsir 

208.  Portion  of  intra-glandular  Lymphatic,  after  Goodsir 


.      -•  -        511 

511 
517 
517 

209.  Section  showing  the  anatomy  of  the  Thymus  gland,  after  Cooper 

210.  Microscopic  appearance  of  Inflammatory  Blood,  after  Addison  -         534 

211.  Web  of  Frog's  foot,  slightly  magnified,  after  Wagner,   -  -         541 

212.  The  anatomy  of  the  Heart        -  -  551 

213.  Hsemadynamometer  of  Poisseuille         -  -  -        ,     -  -         555 

214.  Gill-tuft  of  Doris,  after  Alder  and  Hancock       - 

215.  Lung  of  Triton,  slightly  magnified,  after  Wagner 

216.  Portion  of  the  same  more  highly  magnified,  after  Wagner 

217.  Capillary  Circulation  in  lung  of  living  Triton,  after  Wagner     - 

218.  The  Larynx,  Trachea  and  Bronchia      .... 

219.  Bronchia  and  Blood-vessels  of  the  Lungs  -  -  -  -  -         577 

220.  Development  of  Lungs,  after  Rathke     - 

221.  Arrangement  of  Capillaries  in  Human  Lung    - 

222.  Mammary  Gland  of  Ornithorrhyncus,  after  Miiller       -  -         616 

223.  Exterior  of  lobule  of  liver  of  Squilla,  after  Miiller        -  -         619 

224.  Interior  of      do.  do.  do. 

225.  Inferior  Surface  of  the  Liver     -  -  -         620 
22G.  Three  Coats  of  the  Gall  Bladder                        ...            -  -         620 

227.  Gall  bladder  distended,  with  vessels  injected    - 

228.  Nucleated  Cells  of  Parenchyma  of  Liver  -         621 

229.  Lobules  of  Liver,  with  branches  of  Hepatic  vein,  after  Kiernan  -         622 

230.  Horizontal  section  of  lobules,  showing  arrangement  of  their  blood-vessels,  after 

Kiernan      -  -  .....         622 

231.  Horizontal  section  of  lobules,  showing  arrangement  of  their  bile-ducts,  after 

Kiernan      -----  ...         622 

232.  Nucleated  Cells  forming  Parenchyma  of  Liver,  after  Bowman  -  -         624 

233.  Origin  of  Liver  in  Chick,  after  Miiller  - 

234.  Lobules  in  a  state  of  Anemia,  after  Kiernan     ...  625 

235.  Do.     in  first  stage  of  hepatic- venous  congestion,  after  Kiernan         -  -         625 


LIST  OF  WOOD-ENGRAVINGS.  XXV11 

PIG.  PAGE 

236.  Lobules  in  second  stage  of  hepatic-venous  congestion,  after  Kiernan    -            -  625 

237.  Do.     in  a  state  of  portal-venous  congestion,  after  Kiernan    -                          -  625 

238.  Hepatic  cells  loaded  with  Fat,  after  Bowman                                                        -  627 

239.  Right  Kidney,  with  Renal  Capsule        -                           -  632 

240.  Section  of  Kidney  after  Wilson              -  632 

241.  Half  a  Kidney,  divided  vertically                       -                                      -             -  633 

242.  Kidney  divided  vertically,  with  Arteries  injected                        -                          -  633 

243.  Section  of  Kidney,  after  Wagner                                      -                          -            -  634 

244.  Portion  of  Tubuius  Uriniferus,  after  Wagner     -                         -                          -  634 

245.  Section  of  a  Pyramid  of  Malpighi          -  635 

246.  Magnified  view  of  small  portion  of  the  Kidney,  after  Wagner              -  636 

247.  Structure  of  Malpighian  Body,  after  Bowman   -            -            -             .             .  637 

248.  Diagram  of  Circulation  in  the  Kidney,  after  Bowman  -            -     "        -             -  637 

249.  Corpora  Wolffiana,  after  Muller              -                                                   «            -  637 

250.  Mammary  Gland           -                                       *            .     •                     -             -  647 
25.1.  Vertical  section  of  Mammary  Gland      -  647 

252.  Distribution  of  Milk-ducts  in  Mammary  Gland,  after  Sir  A.  Cooper      -            -  648 

253.  Termination  of  portion  of  milk-duct  in  a  cluster- of  follicles,  after  Sir  A.  Cooper  648 

254.  Mammary  follicles,  with  contained  cells,  after  Lebert  -  -    .     648 

255.  Lobule  of  Parotid  Gland,  after  Wagner                            -             -                           -  656 

256.  Capillary  Network  of  Glandular  follicles,  after-Berres  -                                       -  656 

257.  Rudimentary  Pancreas  of  Cod,  after  Muller      ....                        .  656 

258.  The  Testicle  injected  with  Mercury      -            -                                                    -  658 

259.  Minute  structure  of  the  Testis               -             -         .    *             -        .    -            -  658 

260.  Human  Testis,  injected  with  Mercury,  after  Lauth       -  -  -  —       659 

261.  Diagram  of  the  structure  of  the  same    -             -           v-                                       -  659 

262.  Sudoriferous  Gland,  after  Wagner          -  -  -    -     661 

263.  Layer  of  Sweat-glands  of  the  Axilla,  after  Todd  and  Bowman              -             -  662 

264.  Sweat-gland  and  its  blood-vessels,  after  Todd  and  Bowman      -                          -  ^662 

265.  Cuticular  portion  of  a  Sweat-duct  of  the  Heel,  after  Todd  and  Bowman           -  662 

266.  Three  views  of  Sebaceous  glands  and  hair-follicles,  after  Todd  and  Bowman  •  664 

267.  Cutaneous  glands  of  external  Meatus  Auditorius,  after  Wagner             •            •  665 

268.  Cutaneous  follicles  of  the  Axilla,  after  Homer               -                                       -  665 

269.  Gastric  glands  in  Human  Stomach,  after  Wagner                       ...  666 
27Q.  Horizontal  section  of  a  Stomach-cell  and  tubes,  after  Todd  and  Bowman          -  666 

271.  Vertical  sections  of  mucous  membrane  of  Stomach,  after  Todd  and  Bowman  -  667 

272.  Entrances  to  secreting  follicles,  after  Boyd         -  667 

273.  Stomach-cells  and  Epithelium,  after  Todd  and  Bowman                                      -  667 

274.  Villi  and  follicles  of  Lieberkiihn  on  surface  of  Ileum                                          -  668 

275.  One  of  the  Glandulse  solitaries  of  Peyer,  after  Boehm                              -        :     -  668 

276.  Mucous  coat  of  Small  Intestine,  as  altered  in  Fever,  after  Boehm         -            -  668 

277.  Glands  of  Peyer  on  Small  Intestine       -                          ...                          .  669 

278.  Conglomerate  gland  of  Brunner,  after  Boehm    -                                                    -  669 

279.  Patch  of  agminated  Peyer ian  glands,  after  Boehm        .-                                       -  670 

280.  Extremity  of  Placental  Villus,  after  Goodsir     -  •                                                .  705 

281.  External  membrane  and  cells  of  Placental  villus,  after  Goodsir             -             -  705 

282.  Diagram  of  the  arrangement  of  the  Placental  Decidua,  after  Goodsir  -            -  706 

283.  Plan  of  early  Uterine  Ovum,  after  Wagner       -                          ...  715 

284.  Diagram  of  Ovum,  showing  formation  of  digestive  cavity  and  of  amnion,  after 

Wagner       -                                       ...                          .  715 

285.  Do.  do.     still  more  advanced,  the  allantois  beginning  to  appear,  after 

Wagner       -             -                                       -             -            -            -  717 

286.  Diagram  of  Ovum  in  the  second  month,  showing  incipient  formation  of  Pla- 

centa, after  Wagner  -  -  -  -  -  -  -    v     717 

287.  Section  of  Uterus,  showing  ovum,  membranes,  &c.,  at  the  time  of  formation  of 

Placeifta,  after  Wagner        -            -             -            -             -            -   .         -  718 

288.  Diagram  illustrating  the  Fcetal  Circulation         -  -  -  ,721 

289.  Curve  representing  the  relative  Viability  of  Human  Male  and  Female  at  dif- 

ferent ages,  after  Quetelet  -                                                  -                        -  727 
290     Do.            do.                do.          Heights  and  Weights  of  the  Human  Male 

and  Female  at  different  ages,  after  Quetelet            -            -            •            -  728 

ALSO, 
Two  Lithographic  Plates,  with  27  figures. 


INTRODUCTION.-' 


THE  object  of  the  science  of  Physiology  is  to  bring  together,  in  a  sys- 
tematic form,  the  phenomena  which  normally  present  themselves  during  the 
existence  of  living  beings ;  and  to  classify  and  compare  these,  in  such  a  man- 
ner as  to  deduce  from  them  the  general  laws  or  principles,  according  to  which 
they  take  place. 

The  term  Law  having  been  frequently  applied  to  physical  and  physiological 
phenomena,  in  a  manner  very  different  from  that  which  sound  philosophy 
sanctions,  it  is  desirable  to  explain  the  acceptation  (believed  by  the  author  to 
be  the  only  legitimate  one)  in  which  it  is  here  employed.  The  so-called 
Laws  of  Nature  are  nothing  else  than  general  expressions  of  the  conditions, 
under  which  certain  assemblages  of  phenomena  occur ;  so  far  as  those  con- 
ditions are  known  to  us.  Thus  the  law  of  Gravitation,  in  General  Physics 
(the'  most  universal  in  its  action  of  any  with  which  we  are  acquainted),  is 
nothing  else  than  a  simple  expression  of  the  fact,  that,  under  all  circum- 
stances, two  masses  of  matter  will  attract  each  other  with  forces  directly  pro- 
portional to  their  respective  bulks,  and  inversely  as  their  distances.  So,  again, 
the  law  of  Cell-growth,  which  seems  to  hold  the  same  rank  in  Physiology 
with  that  of  Gravitation  in  Physics,  embodies  these  two  general  facts, — that 
all  organised  beings  originate  in  cells, — and  that  the  various  functions  of  life 
are  carried  on,  even  in  the  adult  condition,  by  the  continued  growth  and  de- 
velopment of  cells. 

In  no  case  can  natural  phenomena  be  correctly  said  to  be  governed  by 
laws ;  since  the  laws  themselves  are  nothing  else  than  manifestations  of  the 
Will  of  the  governing  Power.  But  they  may  be  properly  said  to  take  place 
according  to  certain  laws  ;  these  laws  being  framed  by  Man  as  expressions 
or  descriptions  of  the  slight  glimpses  he  possesses,  of  the  plan  according  to 
which  the  Creator  sees  fit  to  operate  in  the  natural  world.  Thus  understood, 
the  use  of  the  term  Law  can  be  in  no  way  supposed  to  imply,  that  the  Deity 
stands  in  any  other  relation  to  the  phenomena  of  the  Universe  than  as  their 
direct  and  constantly-operating  Cause. 

In  order  to  determine  the  true  laws,  t r  most  general  principles,  of  Phy- 
siological Science,  a  very  extensive  comparison  is  requisite.  Principles,  which 
might  seem  of  paramount  importance  in  regard  to  one  group  of  living  beings, 
are  often  found,  on  a  more  general  review,  to  be  quite  subordinate.  For 
example,  the  predominance  of  the  Nervous  System  in  the  higher  classes  of 
Animals,  and  its  evidently  close  connection  with  many  of  the  functions  of 
life,  has  led  several  Physiologists  to  the  opinion,  that  its  influence  is  essential 
to  the  performance  of  the  functions  of  Nutrition,  Secretion,  &c. ;  but,  on 
turning  our  attention  to  the  Vegetable  kingdom,  in  which  nothing  analogous 
to  a  nervous  system  can  be  proved  to  exist,  we  find  these  functions  going  on 
with  even  greater  activity  than  in  animals.  It  is  clear,  therefore,  they  may 
be  performed  without  it ;  and,  on  a  closer  examination  of  the  phenomena 
4 


38  INTRODUCTION. 

presented  by  Animals,  it  is  seen  that  these  may  be  explained  better,  on  the 
principle  that  the  nervous  system  has  a  powerful  influence  on  such  actions, 
than  on  the  idea  that  it  affords  a  condition  essential  to  them.  Recent  inquiries 
have  shown  that  the  agents  immediately  concerned  in  these  operations  are  of 
the  same  nature  in  both  kingdoms ;  the  separation  of  the  nutrient  materials 
from  the  circulating  fluids,  or  the  elimination  of  substances  which  are  to  be 
withdrawn  from  it,  being  performed  in  the  animal,  as  in  the  plant,  by  ce//s,  in 
the  manner  to  be  explained  hereafter. — This  is  only  one  out  of  many  in- 
stances, which  it  would  be  easy  to  adduce,  in  proof  of  the  necessity  of  bring- 
ing together  all  the  phenomena  of  the  same  kind,  in  whatever  class  of  living 
beings  they  may  be  presented,  before  we  attempt  to  erect  any  general  princi- 
ples in  Physiology. 

The  object  of  the  present  treatise,  however,  is  not  to  follow  out  such  an 
investigation ;  but  to  show  the  detailed  application  of  the  principles  of  which 
Physiological  science  may  now  be  said  to  consist,  to  the  phenomena  exhibited 
by  the  Human  being  during  the  continuance  of  health  or  normal  life.  These 
phenomena,  when  they  occur  in  a  disturbed  or  irregular  manner,  constitute 
disease  or  abnormal  life;  and  become  the  subjects  of  the  science  of  Pathology. 
It  is  impossible  to  draw  a  precise  line  of  demarcation,  between  the  states  of 
health  and  disease ;  since  many  variations  may  occur,  which  do  not  pass  the 
limits  of  what  must  be  called  in  some  individuals  the  normal  state,  but  which 
must  be  regarded  as  decidedly  abnormal  actions  in  others.  The  sciences  of 
Physiology  and  Pathology,  therefore,  are  very  closely  related  to  each  other; 
and  neither  can  be  pursued  with  the  highest  prospect  of  success,  except  in 
connection  with  the  other. 

Equally  close  is  the  relation  between  Hygiene, — or  the  art  of  preserving 
the  body  in  health,  which  is  founded  on  the  science  of  Physiology, — and 
Therapeutics,  which  is  the  art  of  curing  disease,  founded  upon  the  science  of 
Pathology.  In  proportion  as  the  science  of  Physiology  is  perfected,  will  the 
simplicity  and  certainty  of  its  practical  applications  increase ;  and  although 
we  may  not  anticipate  a  return  of  patriarchal  longevity,  yet  the  experience  of 
the  last  century  has  amply  shown,  that  every  general  increase  of  attention  to 
its  simple  and  universally-acknowledged  truths  is  attended  with  a  prolonga- 
tion of  life,  and  contributes  to  that  not  less  important  object,  its  emancipation 
from  disease.  In  like  manner,  with  every  advance  in  Pathological  science, 
will  the  art  of  Therapeutics  lose  its  merely  empirical  character,  and  become 
more  and  more  rational;  that  is,  the  rules  laid  down  for  the  treatment  of 
disease  will  be  less  and  less  founded  upon  the  results  of  a  limited  experience 
as  to  the  efficacy  of  particular  remedies  in  removing  certain  abnormal  phe- 
nomena ;  and  will  have  reference  more  and  more  to  the  nature  of  the  morbid 
action,  which  is  indicated  by  the  symptoms.  Thus,  when  the  urine  presents 
a  particular  sediment,  our  inquiries  are  directed,  not  so  much  to  the  condition 
of  the  kidney  itself,  as  to  the  constitutional  state  which  causes  an  undue 
amount  of  the  substance  in  questio^  to  be  carried  off  by  the  urinary  excre- 
tion, or  which  prevents  it  from  being  (as  usual)  dissolved  in  the  fluid. 

In  proportion  as  our  treatment  of  disease  thus  loses  its  empirical  character, 
and  is  founded  on  scientific  principles,  must  it  increase  in  perfection  and  suc- 
cess ;  and  in  like  proportion  will  the  Medical  Profession  acquire  that  dignity 
to  which  the  nobility  of  its  objects  entitles  it,  and  that  general  estimation 
\vhich  will  result  from  the  enlightened  pursuit  of  them. 


39 


CHAPTER  I. 

ON  THE  PLACE  OF  MAN  IN  THE  SCALE  OF  BEING. 

1.  Distinction  between  Animals  and  Plants. 

1.  IN  entering  upon  the  general  survey  of  the  Animal  Kingdom,  which  it 
is  desirable  to  take  before  we  consider  in  detail  any  particular  member  of  it, 
the  question  naturally  arises, — how  is  the  Animal  distinguished  from  the 
Vegetable  ?  There  is  no  difficulty  in  replying  to  this,  if  we  keep  in  view 
merely  the  higher  tribes  of  each  division ;  no  one,  for  example,  would  be  in 
any  danger  of  confounding  a  Whale  with  a  Palm,  or  an  Elephant  with  an 
Oak.  It  is  when  we  descend  to  the  opposite  extremity  of  the  scale,  that  we 
encounter  the  greatest  difficulty ;  from  the  circumstance  that  the  distinguish- 
ing characters  of  each  kingdom  disappear,  one  after  another,  until  we  are 
reduced  to  those  which  seem  common  to  both.  So  completely  is  this  the 
case,  that  there  are  many  tribes  which  cannot,  in  the  present  state  of  our 
knowledge,  be  referred  with  certainty  to  either  one  division  or  the  other.  We 
are  accustomed  to  think  of  Animals  as  beings,  which  not  only  grow  and 
reproduce  themselves,  but  which  also  possess  the  power  of  spontaneously 
moving  from  place  to  place,  and  which  are  conscious  of  impressions  made 
upon  them :  and  we  usually  regard  Plants  as  beings  which  are  entirely  des- 
titute of  sensibility  and  of  the  power  of  spontaneous  motion, — going  through 
all  their  processes  of  growth,  reproduction  and  decay,  alike  unconscious  of 
pleasure  and  of  pain,  and  devoid  of  all  power  of  voluntarily  changing  their 
condition.  Such  a  definition  is  probably  the  most  correct  that  we  can  employ  ; 
but  great  difficulties  lie  in  the  way  of  its  application.  There  are  many  tribes 
which  possess  a  general  structure  more  allied  to  that  of  beings  known  to  be 
Animals,  than  to  that  of  any  Plants ;  and  which  yet  present  no  decided  indi- 
cations, either  of  sensibility  or  of  voluntary  power.  Such  is  the  Sponge, 
the  fabric  of  which  closely  corresponds  with  that  of  many  Alcyonian  Polypes, 
whose  animality  is  undoubted;  whilst  there  are  no  known  Vegetables  to 
which  it  presents  any  near  resemblance :  and  yet  neither  observation  nor 
experiment  has  ever  succeeded  in  proving  that  the  Sponge  feels  or  spontane- 
ously moves.  On  the  other  hand,  many  Vegetables  perform  evident  move- 
ments, which,  at  first  sight,  appear  to  be  spontaneous,  as  if  they  indicated 
sensibility  on  the  part  of  the  being  that  executes  them.  Such  movements, 
however,  can  in  some  instances  (as  in  that  of  the  Sensitive-Plant,  or  of  the 
Venus's  Fly-trap),  be  referred  to  a  sort  of  mechanism,  the  action  of  which 
does  not  involve  sensibility,  and  which  may  be  compared  with  the  many 
movements  (such  as  that  of  the  heart)  that  are  constantly  taking  place  in  the 
bodies  of  the  highest  animals,  without  their  consciousness ;  and  in  other  cases 
(as  in  the  Oscillatoriss)  they  are  so  rhythmical,  as  to  impress  the  observer 
with  the  idea  that  they  are  rather  the  result  of  some  physical,  than  of  any 
mental,  influence.  In  this  respect  they  correspond  with  the  motions  of  the 
constantly-vibrating  cilia;  which  cover  the  surface  of  the  mucous  membranes 
of  Animals ;  and  which  have  been  recently  detected  in  the  reproductive  par- 
ticles of  certain  among  the  lower  tribes  of  aquatic  Plants. 


40  ON  THE  PLACE  OF  MAN  IN  THE  SCALE  OF  BEING. 

2.  However  difficult  it  may  be  for  us,  owing  to  our  imperfect  knowledge, 
to  draw  the  line  in  individual  cases,  it  cannot  be  doubted  that  a  boundary  does 
exist ;  and,  in  general,  a  very  simple  mark  will  suffice  to  establish  the  dis- 
tinction.    This  mark  is  the  presence  or  absence  of  a  Stomach,  or  internal 
cavity  for  the  reception  of  food.     The  possession  of  a  stomach  cannot  be  re- 
garded, however,  as  in  itself  an  essential  distinction  between  the  two  kingdoms 
(as  some  have  represented  it) ;  for  its  presence  is  merely  a  result,  so  to  speak, 
of  the  nature  of  the  food  of  Animals,  and  of  the  mode  in  which  it  is  obtained. 
Vegetables  are  dependent  for  their  support,  upon  those  materials  only,  which 
they  obtain  from  the  surrounding  elements  ;  carbonic  acid,  water  and  ammonia, 
duly  supplied  to  them,  with  a  small  quantity  of  certain  mineral  ingredients, 
affording  all  the  conditions  they  require  for  the  production  of  the  most  mas- 
sive fabrics,  and  the  greatest  variety  of  secretions.     But  these  same  elements, 
if  supplied  to  Animals,  could  not  be  converted  by  them  into  the  materials  of 
organized  structures;  for  they  can  only  employ  them  as  food,  after  they  have 
been  united  into  certain  peculiar  organic  compounds  ;  and  Animals  are  con- 
sequently dependent,  either  directly  or  indirectly,  upon  the  Vegetable  kingdom 
for  their  means  of  support.     Now  they  cannot  incorporate  any  alimentary 
substance  into  their  own  tissues,  untilit  has  been  reduced  to  the  fluid  form; 
hence  they  need  the  means  of  effecting  this  reduction,  which  are  supplied  by 
the  stomach.     Again,  they  cannot  be  always  in  immediate  relation  with  their 
food  ;  they  have  to  go  in  search  of  it,  and  need  a  store-room  in  which  it  may 
be  deposited  during  the  intervals  ;  this  purpose  also  is  supplied  by  the  stomach. 
It  is  evident,  moreover,  that  the  powers  of  voluntary  locomotion  and  sensa- 
tion, which  Animals  enjoy,  are  connected  with  the  peculiar  nature  of  the  food 
they  require ;  for  if  they  were  fixed  in  the  ground,  like  Plants,  they  would 
not  be  able  to  obtain  that  which  they  require  for  their  support.     It  is  true  that 
there  are  some,  which  seem  almost  rooted  to  one  spot;  but  these  have  the 
power  of  bringing  their  food  within  their  reach,  though  they  cannot  go  in 
search  of  it.     Such  is  the  case  with  many  Polypes,  which  use  their  outspread 
tentacula  for  this  purpose ;  and  with  the  lower  Mollusca,  which  can  create 
currents  by  means  of  ciliary  action. 

3.  A  distinction  might  probably  be  erected,  between  the  Animal  and  Vege- 
table kingdoms,  upon  the  mode  in  which  the  first  development  of  the  germ 
takes  place.     The  seed  of  the  Plant,  at  the  time  of  fertilisation,  principally 
consists  of  a  store  of  nourishment  prepared  by  the  parent  for  the  supply  of 
the  germ,  which  is  introduced  into  the  midst  of  it.     The  same  may  be  said  of 
the  egg  of  the  Animal.     In  both  instances,  the  first  development  of  the  germ 
is  into  a  membranous  expansion,  which  absorbs  the  alimentary  materials  with 
which  it  is  in  contact;  and  it  prepares  these  by  assimilation,  for  the  nourish- 
ment of  the  embryonic  structure,  the  most  important  parts  of  which — the 
only  permanent  parts  in  the  higher  classes  of  Animals  and  in  Phanerogamic 
Plants — are  in  its  centre.     Now  in  Plants,  this  membranous  expansion  (the 
single  or  double  cotyledon)  absorbs  by  its  outer  surface,  which  is  applied  to 
the  albumen  of  the  seed,  and  takes  it  more  or  less  completely  into  its  own 
substance.     In  Animals,  this  expansion  is  developed  in  such  a  manner,  that 
it  surrounds  the  albumen,  inclosing  it  in  a  sac,  of  which  the  inner  surface 
only  is  concerned  in  absorption.     This  sac  is,  then,  the  temporary  stomach 
of  the  embryonic  structure ;  it  becomes  the  permanent  stomach  of  the  Radi- 
ata ;  but  in  the  higher  classes,  only  a  portion  of  it  is  retained  in  the  fabric  of 
the  adult, — the  remainder  being  cast  off,  like  the  cotyledon  of  Plants,  as  soon 
as  it  has  performed  its  function.     Thus,  then,  the  first  nisus  of  Animal  de- 
velopment is  towards  the  formation  of  a  stomach,  for  the  internal  reception 
and  digestion  of  food ;  whilst  the  first  processes  of  Vegetable  evolution  tend 
to  the  production  of  a  leaf-like  membrane,  which,  like  the  permanent  frond  of 


GENERAL  SUBDIVISIONS  OF  THE  ANIMAL  KINGDOM.  41 

the  lower  classes  of  Plants,  absorbs  nourishment  by  its  expanded  surface 
only. 

4.  Some  Physiologists  have  asserted  that  the  nature  of  the  respiratory  pro- 
cess affords  a  ground  of  distinction  between  Animals  and  Plants; — oxygen 
being  absorbed,  and  carbonic  acid  evolved,  by  the  former, — and  a  converse 
change  being  effected  in  the  surrounding  air  by  the  latter.     It  is  not  correct, 
however,  to  designate  this  converse  change  as  a  consequence  of  the  respiratory 
process  ;  for  in  Plants,  as  in  Animals,  there  is  a  continual  absorption  of  oxygen 
and  evolution  of  carbonic  acid,  which  constitute  the  true  function  of  respira- 
tion; but  the  effects  of  this  change  are  masked  (as  it  were),  in  Plants,  by 
those  of  the  fixation  of  carbon  from  the  atmosphere,  which  only  takes  place 
under  the  influence  of  sun-light,  and  which  is  much  more  analogous  to  the 
digestion  of  Animals.     The  most  valid  distinction,  in  doubtful  cases,  seems 
likely  to  be  founded  on  the  chemical  constitution  of  the  tissues  themselves. 
In  the  plant,  the  whole  of  the  organized  structure,  when  freed  from  the  pro- 
ducts of  secretion  which  are  deposited  in  it,  (many  of  these  containing  the 
same  proportion  of  nitrogen  as  exists  in  animal  flesh,)  is  found  to  have  the 
same  composition  with  starch ;  being  formed  of  oxygen,  hydrogen,  and  car- 
bon only.     In  the  animal,  on  the  other  hand,  the  organised  tissues  all  contain 
azote  -as  part  of  their  proper  substance ;  non-azotised  compounds,  such  as 
fatty  matter,  being  merely  deposited  in  these,  as  products  of  secretion.     Hence 
if  the  chemical  composition  of  the  organised  tissues  themselves  can  be  cor- 
rectly determined,  the  Vegetable  or  Animal  nature  of  a  doubtful  body  may  be 
ascertained.     By  this  test,  the  long-disputed  question  of  the  nature  of  the 
true  Corallines  has  been  set  at  rest ;  their  tissue,  when  freed  from  the  lime  de- 
posited in  it,  being  found  to  have  the  composition  of  that  of  Plants :  and  upon 
evidence  of  the  same  kind,  (the  presence  of  starch  in  their  interior,)  a  large 
number  of  tribes,  which  have  been  described  by  Ehrenberg  as  Animalcules, 
are  now  generally  referred  to  the  Vegetable  kingdom. 

2.   General  Subdivisions  of  the  Animal  Kingdom. 

5.  The  animal  kingdom  was  formerly  divided  into  two  primary  groups, — the 
Vertebratedand.  the  Invertebrated ;  the  former  comprising  those  which  are  dis- 
tinguished by  the  possession  of  a  jointed  spinal  column,  consisting  of  a  num- 
ber of  internal  bones,  termed  vertebrae  ;  and  the  latter  including  all  those  ani- 
mals which  are  destitute  of  this   support.      It  was  pointed  out  by  Cuvier, 
however,  that  among  the  Invertebrata  there  are  three  types  of  organization, 
as  distinct  from  each  other  as  any  of  them  are  from  the  Vertebrate ;  and  he 
accordingly  distributed  the  whole  under  four  primary  divisions  or  sub-king- 
doms :  of  these,  the  VERTEBRATA  rank  highest ;  next,  the  ARTICULATA  and 
the  MOLLTISCA,  which  may  be  said  to  form  two  parallel  series,  both  of  them 
inferior  in  degree  of  organization  to  the  Vertebrata,  but  superior  to  the  lowest 
group ;  and  lastly,  the  RADIATA,  which  include  those  animals  that  border  most 
closely,  both  in  external  aspect,  and  in  general  character,  upon  the  Vegetable 
kingdom.     The  members  of  these  groups  are  readily  separated  from  each 
other  by  the  structure  of  their  skeletons,  or  organs  of  support  and  protection ; 
as  well  as  by  many  other  characters.    In  the  Vertebrata,  the  skeleton  consists 
of  a  number  of  internal  jointed  bones,  which  are  clothed  by  the  muscles  that 
are  attached  to  them  and  move  them ;  these  bones   are  traversed  by  blood- 
vessels, and  are  to  be  regarded  as  in  all  respects  analogous  to  the  other  living 
tissues  of  the  body.     In  the  Articulata,  the  soft  parts  are  supported  by  a  hard 
external  envelope,  which  is  of  corresponding  form  on  the  two  sides  of  the 
median  line,  and  which  is  divided  into  several  pieces,  jointed  or  articulated 
together  by  a  membrane,  in  such  a  manner  as  still  to  allow  of  free  motion ; 

4* 


42  ON  THE  PLACE  OF  MAN  IN  THE  SCALE  OF  BEING. 

and  the  muscles,  which  are  numerous  and  complex,  are  attached  to  the  inte- 
rior of  these.  In  the  Mollusca,  the  whole  body  is  quite  soft ;  and  many  spe- 
cies exist,  in  which  it  has  no  external  protection ;  in  a  large  proportion  of  the 
group,  however,  the  surface  has  the  power  of  producing  shelly  matter,  so  as 
to  form  a  protective  habitation,  within  which  the  animal  can  withdraw  its 
body,  but  which  does  not  exhibit  any  very  definite  type  of  form.  In  the 
Radiata,  all  the  parts  are  arranged  in  a  circular  manner,  the  mouth  being  in 
the  centre;  some  of  them  are  protected  by  firmly-jointed  external  skeletons, 
like  those  of  the  Articulata  ;  whilst  others  deposit  calcareous  matter  in  the  cen- 
tre of  their  soft  fleshy  structures,  as  if  sketching  out  the  internal  skeleton  of 
the  Vertebrata.  The  skeletons  of  most  of  the  Invertebrata  differ,  however, 
from  those  of  Vertebrate  animals,  in  this  important  character, — that  they  are 
not  permeated  by  vessels,  and  are  formed  only  by  superficial  deposition. 
Hence  they  are  termed  extra-vascular  :  and  it  is  an  obvious  result  of  an  ar- 
rangement of  this  kind,  that  parts  once  formed  are  never  changed,  except  by 
the  ordinary  processes  of  decay,  and  that  they  can  only  be  extended  by  addi- 
tion to  their  exterior ;  whilst  in  Vertebrata,  the  bones  are  subject  to  alterations 
of  any  kind,  whether  of  removal  or  addition,  throughout  their  entire  substance. 
It  is  not  correct  to  regard  them,  however,  as  mere  exudations,  or  as  being  des- 
titute of  vitality  ;  since  they  consist,  in  all  instances,  of  a  regularly-organized 
tissue,  in  which  the  mineral  matter,  where  such  exists,  is  deposited ;  and  in 
several  cases  they  are  traversed  by  tubes,  which  seem  to  convey  a  fluid  de- 
stined for  their  nutrition,  if  not  actual  blood.  Fabrics  of  this  kind  are  on  the 
same  footing  with  the  dentine  and  enamel  of  the  teeth  of  Vertebrata  (§§  209, 
210);  to  which  they  sometimes  bear  a  very  strong  resemblance. — A  more 
detailed  account  of  the  general  structure  of  these  sub-kingdoms  will  now  be 
given,  beginning  with  the  lowest. 

3.  General  characters  of  Radiata. 

6.  The  RADIATA  possess  many  points  of  affinity  with  the  Vegetable  king- 
dom ;  and  of  these,  the  circular  arrangement  of  their  parts  is  one  of  the  most 
evident.  Many  species  of  Sea-Anemone,  for  instance,  present  an  appearance 
so  much  resembling  that  of  various  composite  blossoms,  as  to  have  been  com- 
monly termed  Animal-flowers, — a  designation  to  which  they  further  seem 
entitled,  from  the  small  amount  of  sensibility  they  manifest,  and  the  evident 
influence  of  light  upon  their  opening  and  closing.  But  it  is  in  the  tendency  to 
the  production  of  compound  fabrics, — each  containing  a  number  of  individu- 
als, wrhich  have  the  power  of  existing  independently,  but  which  are  to  a  cer- 
tain degree  connected  with  one  another, — that  we  recognise  the  greatest  aifinity 
in  structure,  between  this  group  and  the  Vegetable  kingdom.  Every  tree  is 
made  up  of  a  large  number  of  buds,  which  are  composed  of  leaves  arranged 
round  a  common  axis ;  each  bud  has  the  power  of  preserving  its  own  life, 
and  of  reproducing  the  original  structure,  when  removed  from  the  parent  stem, 
if  placed  in  circumstances  favourable  to  its  growth  ;  and  yet  all  are  connected 
in  the  growing  tree,  by  a  system  of  vessels,  which  forms  a  communication 
between  them.  This  is  precisely  the  nature  of  the  structures  formed  by  the 
animals  of  that  class,  which  may  be  regarded  as  the  most  characteristic  of  the 
Radiate  group.  Every  mass  of  Coral  is  the  skeleton  of  a  compound  animal, 
consisting  of  a  number  of  polypes,  connected  together  by  a  soft  flesh,  in  which 
vessels  are  channelled  out ;  these  polypes  are  capable  of  existing  separately, 
since  each  one,  when  removed  from  the  rest,  can  in  time  produce  a  massive 
compound  fabric,  like  that  of  its  parent ;  but  they  all  contribute  to  the  main- 
tenance of  the  composite  structure,  so  long  as  they  are  in  connection  with  it. 
In  some  instances  the  skeleton  is  stony,  and  is  formed  by  the  deposition  of 


GENERAL  CHARACTERS  OF  RADIATA. 


43 


calcareous  matter — either  in  the  centre  of  each  fleshy  column,  so  as  to  form  a 
solid  stem, — or  on  its  exterior,  so  as  to  form  a  tube.  In  other  cases  it  is  horny ; 
and  then  it  may  be  a  flexible  axis,  or  a  delicate  tube.  Both  the  stony  and 
horny  Corals  frequently  possess  the  form  of  plants  or  trees:  and  as  their 
skeletons  are  often  found  with  no  obvious  traces  of  the  animals  to  which  they 
belonged,  they  have  been  accounted  Vegetable  growths.  There  is  not  the 
least  doubt,  however,  as  to  the  Animal  origin  of  the  greater  part  of  these  plant- 
like  structures. 

7.  The  affinity  between  the  lowest  Radiata  and  Plants,  in  regard  to  the 
vital  phenomena  they  exhibit,  is  still  more  close  than  that  manifested  by  their 
structure.  Although,  in  the  higher  groups,  movements  may  be  constantly 
witnessed,  which  evidently  indicate  consciousness  and  voluntary  power,  this 
is  far  from  being  the  case  in  the  lower.  There  are  many  tribes,  whose  recep- 
tion of  food,  growth,  and  reproduction,  are  not  known  to  be  accompanied  by 
any  phenomena  which  distinctly  indicate  their  animal  character.  The  most 
violent  lacerations  produce  no  signs  of  sensibility  ;  and  the  movements  occa- 
sionally exhibited  by  them  have  not  so  much  of  a  spontaneous  aspect  as 
those  which  are  performed  by  many  plants.  This  is  the  case,  for  example, 
with  the  Sponge  tribe ;  and  also  with  a  number  of  microscopic  species.  So 

Fig.  1. 


Asterias  aurantiaca,  with  the  upper  side  of  the  hard  envelope  removed  ;  a,  central  stomach ;  b,  coeca 
upon  its  upper  surface,  probably  answering  to  the  liver;  c,c,  coecal  prolongations  of  stomach  into  ray  a; 
c',  c',  the  same  empty  ;  rf,  the  same  opened  ;  e,  under  surface,  showing  vesicles  of  feet ;/,  vesicles  con- 
tracted, showing  skeleton  between  them. 


44  ON  THE  PLACE  OF  MAN  IN  THE  SCALE  OF  BEING. 

doubtful  is  the  nature  of  these  beings,  that  their  Animal  or  Vegetable  charac- 
ter is  rather  to  be  decided  by  their  affinity  with  species  known  to  belong  to 
one  or  the  other  kingdom,  and  by  the  chemical  composition  of  their  tissues, 
than  in  any  other  way. 

8.  It  is  very  different,  however,  in  regard  to  the  higher  Radiata.     Even 
among  the  Zoophytes  (as  the  plant-like  animals  just  alluded    to  are  com- 
monly termed),  there    are  some   species  which   are  unattached   during  the 
whole  period  of  their  lives,  and  which  have  a  power  of  voluntarily  moving 
from  place  to  place,  such  as  is  never  possessed  by  plants.     And  in  the  high- 
est class,  the   Echinodermata,  including  the  Star-fish,  Sea   Urchin,  &c.,  we 
meet  with  a  considerable  degree  of  complexity  of  structure,  and  a  correspond- 
ing variety  of  actions.     Still,  except  in  those  species  which  connect  this  group 
with  others,  the  same  character  of  radial  or  circular  symmetry  is  maintained 
throughout ;  and  in  no  animal  is  it  more  remarkable  than  in  the  common  Star- 
fish.    It  is  exhibited   alike  in  its   internal  conformation  and  in  its  external 
aspect.     The  mouth,  placed  in  the  centre  of  the  disk,  leads  to  a  stomach 
which  occupies  the  greatest  part  of  the  cavity  of  the  body ;  and  this  sends 
prolongations  into  the  arms,  which  are  exactly  alike  in  form,  and  which  oc- 
cupy a  precisely  similar  position  in  every  one.     Each  arm  is  furnished,  on  its 
under  side,  with  a  curious  apparatus  for  locomotion,  consisting  of  a  series  of 
short  elastic  tubes,  which  are  prolonged  through  apertures  in  the  hard  enve- 
lope, from  a  series  of  vesicles  placed  along  the  floor  (as  it  may  be  termed)  of 
the  ray.     The  system  of  vessels   for  absorbing  nutriment  and  conveying  it 
through  the  system,  is  also  disposed  upon  the  same  plan;  and  the  same  may 
be  said  of  the   nervous  system,  and  of  the  only  organs  of  special  sensation 
which  this  animal  appears  to  possess — the  rudimentary  eyes,  of  which  'one  is 
found  at  the  extremity  of  each  ray. 

9.  Amongst  other  results  of  the  repetition  of  similar  organs,  so  remarkable 
in  the  Radiated  group,  is  this, — that  one  or  more  of  them  may  be  removed  with- 
out permanent  injury  to  the  whole  structure,  and  may  even  develope  them- 
selves into  an  entire  fabric.    Thus  in  the  Star-fish,  instances  are  known  of  the 
loss  of  one,  two,  three,  and  even  four  rays,  which  have  been  gradually  repro- 
duced ;  the  whole  process  appearing  to  be  attended  with  little  inconvenience 
to  the  animal.     In  some  species  of  isolated  Polypifera,  such  as  the  common 
Sea- Anemone,  and  Hydra  (Fresh-water  Polype),  this  power  of  reproduction 
is  much  greater.     The  Hydra  may  be  cut  into  a  large  number  of  pieces  (it  is 
said  as  many  as  40)  of  which  every  one  shall  be  capable  of  developing  itself 
in  time  into  a  perfect  polype.     The  Sea-Anemone,  when  divided  either  trans- 
versely or  vertically,  still  lives ;  and  each  half  produces  the  other,  so  as  to  re- 
form the  perfect  animal.     This  is  another  character  which  shows  the  affinity 
of  the  Radiata  to  the  Vegetable  kingdom  ;  and  there  is  yet  another,  derived 
from  their  mode  of  reproduction.     In  many  Polypifera,  we  observe  a  propa- 
gation by  buds,  in  all  respects   conformable  to  that  which  plants  effect,  and 
quite  different  from  the  regular  multiplication  by  distinct  germs.     This  gem- 
miparous  reproduction,  as  it  is  called,  takes  place,  not  only  in  the  compound 
Polypifera,  whose  plant-like  structures   are  extended  by  it,  but  also  in  some 
isolated -species,  such  as  the  Hydra ;  from  the  body  of  which  one  or  more  young 
polypes  bud  forth  at  the  same  time  ;  and  these  buds  may  themselves  put  forth 
another  generation,  previously  to   their  separation  from  their  parent.     This 
kind  of  reproduction  is  not  seen  anywhere  else  in  the  whole  Animal  kingdom, 
except  in  a  few  of  the  lowest  Mollusca  and  Articulata,  which  border  most 
closely  on  the  Radiata. 

10.  In  the  lowest  animals  of  this  group,  such  as  the  simplest  forms  of  Po- 
lypes, we  find  the  whole  body  to  consist  of  nothing  else  than  a  stomach,  fur- 


GENERAL  CHARACTERS  OF  MOLLUSCA.  45 

nished  with  tentacula  for  drawing  food  to  its  orifice.*  The  nutrient  materials 
are  imbibed  by  the  walls  of  the  stomach,  and  are  transmitted  by  them  to  the 
tentacula,  without  any  regular  circulation  ;  and  the  exposure  of  the  whole  of 
the  soft  surface  of  the  body  to  the  surrounding  liquid,  affords  all  the  aeration 
which  is  requisite.  In  the  Medusae,  or  Jelly-fish,  we  often  find  the  stomach 
extending  itself  into  a  ramified  system  of  tubes,  which  convey  its  consents  to 
the  thin  border  of  the  umbrella-shaped  disk,  for  more  effectual  aeration ;  but 
there  is  still  no  separate  circulating  system,  except  in  a  few  instances.  In  the 
class  of  Echinodermata,  however,  which  includes  the  highest  forms  of  Ra- 
diated animals  (such  as  the  Asterias  or  Star-fish,  Echinus  or  Sea-Urchin,  and 
Holothuria  or  Sea-Cucumber),  we  find  the  digestive  cavity  restricted  within 
much  narrower  limits  ;  and  there  is  here  a  distinct  system  of  vessels,  adapted 
to  absorb  the  nutrient  fluid  from  the  digestive  cavity,  and  to  convey  it  to  the 
remoter  parts  of  the  system  for  their  nutrition,  as  well  as  to  effect  its  aeration, 
by  exposing  it  to  the  influence  of  the  air  contained  in  the  surrounding  liquid, 
in  organs  especially  adapted  for  that  purpose. 

4.   General  characters  of  Mollusca. 

11.  The  range  of  Animal  forms  comprehended  in  the  Sub-Kingdom  MOL- 
LUSCA is  so  great,  that  it  would  be  difficult  to  include  them   in  any  positive 
definition  which  should  be  applicable  to  all.     They  present  few  traces  of  the 
circular  disposition  of  organs  around  the  mouth,  which  is  characteristic  of  the 
Radiated  classes ;   and  we   seldom   meet  with   any  marked   approach   to  the 
elongation  of  the  body, — still  seldomer  with  any  indication  of  that  division 
into  segments, — which  are  the  chief  peculiarities  of  the  Articulata.     It  is  by 
the   absence  of  these,  and  of  any  trace  of  the  Vertebrated  structure,  that  the 
Mollusca  are  most  readily  defined.     The  variety  of  form  which  they  present, 
is  less  surprising,  when  it  is  considered  that  the  bulk  of  their  bodies  is  almost 
entirely  made  up  by  organs  of  nutrition  ;  the  organs  of  sensation  and  locomo- 
tion, which  they  possess,  being  chiefly  subservient  to  the  supply  of  these. 
We  find,  in  the  lowest  tribes  of  this  group,  living  beings  which  are  fixed  to 
one   spot  during  all  but  the  earliest  period  of  their  lives ;  and  which  scarcely 
possess  within  themselves  so  much  power  of  movement,  as  that  enjoyed  by 
the  individual  Polypes  in  a  compound  polypidom ;  and  yet  these  exhibit  a 
complex  and  powerful  digestive  apparatus,  a  regular  circulation  of  blood,  and 
an  active  respiration.     We  never  find,  throughout  the  whole  Animal  kingdom, 
that  the  apparatus  of  organic  life  is  arranged  on  any  definite  plan  of  its  own ; 
its  confirmation  being  adapted  to  the  type  which  predominates  in  the  struc- 
ture of  each  group,  and  which  is   principally  manifested  in  the  disposition  of 
the  locomotive  organs.     Thus,  the   stomach  of  the   Star-fish  is  circular,  and 
sends  a  prolongation  into  each  ray ;  whilst  the  digestive  cavity  of  the  Articu- 
lata is   prolonged  into  a  tube.     In   the  Mollusca,  there   is   no  such  definite 
type,  the  apparatus  of  nutrition  having  the  predominance  over  that  of  loco- 
motion ;  and  the  form  of  the  body  is,  therefore,  extremely  variable.     The  re- 
lative places,  even  of  the  most  important  organs  (such  as  the  gills),  are  found 
to  undergo  complete  changes,  as  we  pass  from  one  tribe  to  another ;  although 
their  general  structure  is  but  little  altered. 

12.  The  lower  Mollusca  may  be  characterised  as  consisting  merely  of  a 

*  It  is  usual  to  speak  of  the  orifice  of  the  stomach,  in  the  Polypes,  as  the  mouth ;  and  to 
regard  the  tentacula  as  prolonged  lips.  It  appears  to  the  author  much  more  reasonable,  how- 
ever, to  consider  this  aperture  as  the  cardiac  orifice  of  the  stomach ;  and  to  regard  the  tenta- 
cula in  the  light  of  pharyngeal  constrictors,  their  office  being  to  grasp  the  food  and  convey  it 
to  the  stomach.  This  view  is  borne  out  by  the  conformation  of  the  superadded  parts  in  the 
Ciliobrachiate  Polypes  and  Ascidian  Molluscs. 


46  ON  THE  PLACE  OF  MAN  IN  THE  SCALE  OF  BEING. 

bag  of  viscera ;  they  have  not  even  any  prominence  for  the  mouth,  nor  any 
organs  of  special  sense,  such  as  would  distinguish  a  head;  and  they  are 
entirely  Destitute  of  symmetry, — the  radiated  arrangements  of  parts  seen  in 
Zoophytes  being  absent,  as  well  as  the  bi-lateral  correspondence  which  is 
characteristic  of  the  higher  sub-kingdoms.  In  the  more  elevated  Mollusca, 
however,  which  possess  not  merely  sensitive  tentacula,  but  eyes  and  even  or- 
gans of  smell  and  hearing,  we  find  these  disposed  in  a  symmetrical  manner  ; 
so  that  the  head,  which  is  the  part  concerned  peculiarly  in  animal  life,  does 
present  a  bi-lateral  equality  of  parts,  even  when  the  remainder  of  the  body 
wants  it.  Further,  in  the  more  active  among  the  higher  classes,  we  find  this 
bi-lateral  symmetry  showing  itself  in  the  exterior  of  the  whole  body ;  evi- 
dently bearing  a  pretty  close  relation  to  its  degree  of  locomotive  power.  It 
is  most  evident  and  complete  in  the  Cephalopoda  (Cuttle-fish  tribe);  many 
of  which  are  adapted  to  lead  the  life  of  Fishes,  and  resemble  them  in  the 
general  form  of  the  body,  as  also  in  the  structure  of  many  of  the  individual 
organs.  It  is  also  manifested  in  many  of  the  shell-less  Gasteropoda,  such  as 
the  Slug,  or  the  Jjplysia  (Sea-Hare) ;  as  will  be  seen  by  the  accompanying 
representation  of  a  species  of  the  latter.  But  this  symmetry  does  not  extend 

Fig.  2. 


Aplysia  depilans;  a,  branchisB  or  gills. 

to  the  arrangement  of  the  internal  organs  ;  and  appears  to  be  only  designed  to 
adapt  the  body  for  more  convenient  locomotion. 

13.  As  a  group,  however,  the  Mollusca  are  to  be  characterised  rather  by 
the  absence,  than  by  the  possession,  of  any  definite  form;  and  there  is  a 
corresponding  absence  of  any  regular  organs  of  support,  by  which  such  a 
form  could  be  maintained.  The  name  they  have  received  designates  them 
as  soft  animals ;  and  this  they  are  pre-eminently,  as  every  one  knows,  who 
has  taken  a  Slug  between  his  fingers.  The  shell,  where  it  exists,  is  to  be 
regarded  rather  in  the  light  of  an  appendage,  designed  for  the  mere  protec- 
tion of  the  body,  and  deriving  its  shape  from  the  latter,  than  as  a  skeleton, 
giving  attachment  to  muscles,  and  regulating  the  form  of  the  whole  structure. 
It  is  in  no  instance  a  fixed  point  for  the  muscles  of  locomotion  ;  and  it  is  only, 
indeed,  where  the  body  is  uncovered  by  a  shell,  or  where  a  locomotive  organ 
may  be  projected  beyond  it,  that  any  active  movements  can  be  executed. 
This  locomotive  organ, — ihefoot,  as  it  is  commonly  termed — is  nothing  else 
than  a  fleshy  mass,  formed  by  the  increased  development  of  the  muscular 
portion  of  one  part  of  the  general  envelope  of  the  body,  termed  the  mantle, 
in  which  the  visceral  mass  is  loosely  included.  The  inantle,  is  not  essen- 
tially different  from  the  skin  of  other  animals ;  but  it  is  usually  thicker,  pos- 
sessing a  considerable  amount  of  muscular  fibre  interwoven  with  it,  and  its 


GENERAL  CHARACTERS  OF  MOLLUSCA. 


47 


surface  having  frequently  a  glandular  character.  This  general  muscular 
envelope  is  the  only  locomotive  organ  possessed  by  a  large  portion  of  the 
Mollusca ;  but  its  contractile  properties  are  usually  greatest  at  some  particular 
spot,  where  it  is  thickened  into  a  sort  of  disk,  by  the  alternate  contraction 
and  extension  of  which  the  animal  can  slowly  propel  itself;  this  is  well  seen, 
by  causing  a  Snail  or  Slug  to  crawl  over  a  piece  of  glass,  so  that  the  under 
surface  of  the  disk  may  be  seen  whilst  it  is  in  operation.  The  general  cha- 
racter of  their  locomotion,  however,  is  well  expressed  by  the  term  sluggish; 
and  there  are  scarcely  any  among  the  typical  Mollusca,  whose  activity  is  such 
as  to  demand  for  them  any  higher  appellation. 

14.  The  general  development   of  their  organs  of  Nutrition,  however,  is 

Fig.  3. 


Aplysia  cut  open,  showing  the  viscera ;  a,  the  upper  part  of  oesophagus ;  6,  penis ;  c,  c,  salivary  glands  ', 
dj  superior  or  cephalic  ganglion ;  e,  e,  inferior  or  subresophageal  ganglia;  f,  termination  of  oasophagus ; 
.§-,  g,  first  stomach ;  A,  third  stomach ;  i,  second  stomach ;  &,  intestine  ;  I,  I,  I,  liver ;  m,  posterior  ganglion  ; 
n,  aorta;  o,  hepatic  artery;  p,  ventricle  of  heart;  ?,  auricle;  r,  a,  branchiae ;  t,  testia;  w,  lower  part  of 
intestine  5  v,  ovary ;  tc,  anus. 


48  ON  THE  PLACE  OF  MAN  IN  THE  SCALE  OF  BEING. 

much  higher  than  is  met  with  among  the  Articulata ;  and,  in  proportion  to 
that  of  the  organs  of  Locomotion,  it  is  much  greater  than  will  be  elsewhere 
observed  throughout  the  Animal  kingdom.  The  justice  of  this  statement  will 
be  made  evident  by  a  slight  examination  of  the  preceding  figure,  in  which 
the  interior  structure  of  the  rfplysia,  showing  the  general  character  of  that 
of  the  group,  is  displayed.  The  only  distinct  set  of  muscles,  possessed  by 
this  animal,  is  that  connected  with  the  mouth ;  which  it  is  able  to  push  for- 
wards or  to  draw  back,  and  which  possesses  considerable  powers  of  mastica- 
tion, and  is  furnished  with  large  salivary  glands.  The  nervous  centres  (of 
which  more  will  be  said  hereafter)  are  seen  to  be  principally  disposed  around 
the  oesophagus.  The  whole  digestive  apparatus  is  observed  to  be  very  com- 
plex and  highly  developed ;  the  liver  alone  occupying  a  considerable  part  of 
the  cavity.  The  heart  has  distinct  muscular  walls,  and  is  divided  into  a 
separate  auricle  and  ventricle ;  and  a  large  respiratory  organ  is  developed  for 
the  aeration  of  the  blood.  The  position  of  the  gills,  which  are  external  to 
the  cavity,  but  which  are  concealed  in  part  by  a  fold  of  the  mantle,  and  in 
part  by  the  rudimentary  shell,  is  seen  at  a,  Fig.  2.  The  generative  apparatus, 
also,  is  highly  developed.  Yet  with  all  this  complex  organization,  the  loco- 
motive power  of  the  animal  is  not  much  greater  than  that  of  the  Slug;  no 
other  means  being  provided  for  the  purpose  than  the  contractility  of  the  gene- 
ral envelope,  which  is  greatest  in  the  thickened  portion  on  the  under  side  of 
the  body. 

15.  The  blood  of  the  Mollusca  is  white,  and  the  number  of  corpuscles  in 
it  is  small.     Their  temperature  is  low,  being  seldom  more  than  one  or  two 
degrees  above  that  of  the  surrounding  medium ;  but  many  of  them  are  capa- 
ble of  being  subjected  to  extreme  variations  of  heat  and  cold,  without  their 
vitality  being  thereby  destroyed.    Their  respiration  is  for  the  most  part  aquatic ; 
and  is  performed  by  means  of  gills,  over  which  a  current  of  water  is   con- 
stantly being  propelled,  by  the  vibration  of  the  cilia  that  cover  their  surface. 
Many  of  them  are  dependent  on  the  same  current  for  their  supplies  of  food ; 
part  of  the  water  so  introduced  being  taken  into  the  stomach  ;  and  a  part 
flowing  over  the  respiratory  surface.      The   higher  tribes,  however,  go  in 
search  of  their  food,  and  have  instruments  of  mastication  for  reducing  it;  but 
in  these,  as  in  the  former,  the  anal  orifice  of  the  intestine  opens  into  the 
passage  through  which  the  current  that  has  passed  over  the  respiratory  organs 
finds  egress ;  so  that  the  faecal  matter  from  the  former,  and  the  fluid  that  has 
served  the  purpose  of  the  latter,  are  discharged   together.     Although  very 
voracious  when  supplies  of  food  come  in  their  way,  most  of  the  Mollusca  are 
capable   of  fasting  for  long  intervals,  where  none  offer  themselves, — a  fact 
which  is  readily  explained  by  that  general  inertness  of  their  vital  processes, 
which  has  been  stated  to  be  characteristic  of  the  group. 

5.   General  characters  of  Articulata. 

16.  The  members  of  the  sub-kingdom,  ARTICULATA,  are  distinguished,  for 
the  most  part,  by  characters  which  are  exactly  opposed  to  those  just  enume- 
rated.    Their  characteristic  form  is  easily  defined  ;  and  in  no  instance  is  there 
any  wide  departure  from  it.  The  body  is  more  or  less  elongated,  and  presents 
throughout  a  most  exact  bi-lateral  symmetry.     It  is  completely  inclosed  in  an 
integument  of  greater  density  than  the  rest  of  the  structure,  which  is  divided 
into  distinct  rings  or  segments ;  these,  being  held  together  by  a  flexible  mem- 
brane, allow  considerable  freedom  of  motion,  whilst  they  firmly  protect  the 
soft  parts,  and  afford  attachment  to  numerous  muscles.    It  is  in  the  Centipede, 
and  other  such  animals,  that  this  division  into  segments  is  most  distinctly  and 
regularly  marked.     In  the  lower  Articulata,  such  as  the  Leech  and  the  Earth- 


GENERAL  CHARACTERS  OF  ARTICULATA.  49 

worm,  the  integument  is  altogether  so  soft,  that  the  intervals  of  the  articulations 
are  not  very  distinct  from  the  rings  themselves ;  and  in  the  highest  Crusta- 
cea and  Arachnida,  the  segments  are  so  closely  united  together,  as  to  be  in 
some  instances  scarcely  recognizable.  In  the  former,  the  movements  of  the 
body  are  entirely  effected  by  its  own  flexion  ;  whilst  in  the  latter,  they  are 
committed  to  members  developed  for  that  special  purpose.  These  members 
also  have  an  articulated  external  skeleton.  The  bulk  of  the  body  in  the  Ar- 
ticulata  is  made  up  of  the  muscles,  by  which  the  several  segments  and  theyr 
various  appendages  are  put  in  motion  ;  these  muscles  have  their  fixed  points 
on  the  interior  of  the  hard  envelope,  just  as  they  are  attached  in  Vertebrated 
animals  to  the  exterior  of  the  bones  ;  and  they  form  a  system  of  great  com- 
plexity. 

17.  The  development  of  the  organs  of  nutrition  in  Articulata,  would  seem 
to  be  altogether  subservient  to  that  of  the  Locomotive  apparatus, — their  func- 
tion being  chiefly  to  supply  the  nerves  and  muscles  with  the  aliment  necessary 
to  maintain  their  vigour.     The  power  of  the  muscles  is  so  great  in  proportion 
to  the  size  of  the  animals,  that  in  energy  and  rapidity  of  movement,  some  of 
the  Articulated  tribes  surpass  all  other  beings.     Their  movements  are  directed 
by  organs  of  sensation,  which,  although  not  developed  on  so  high  a  plan  as 
those  of  some  Mollusca,  are  evidently  very  acute  in  their  powers.     There  are 
very  few  instances  of  Articulated  animals  being  in  any  way  restrained  as  to 
freedom  of  locomotion ;  and  these  are  found  in  a  single  group,  the  Cirrhopoda 
or  Barnacle  tribe,  which  connects  this  sub-kingdom  with  the  last.     In  general, 
they  roam  freely  abroad  in  search  of  food,  and  are  supplied  with  prehensile 
organs  for  capturing  their  prey,  and  with  a  complex  masticating  apparatus  for 
reducing  it.     Their  actions  are  evidently  directed  almost  solely  by  instinctive 
propensities,  which  are  adapted  to  meet  every  ordinary  contingency,  being  of 
similar  character  in  each  individual  of  the  same   species,  and  presenting  but 
little  appearance  of  ever  being  modified  by  intelligence.     Hence  these  animals 
seem  like  machines,  contrived  to  execute  a  certain  set  of  operations ;  many  of 
them  producing  immediate  results,  which  even  Man,  by  the  highest  efforts  of 
his  reason,  has  found  it  difficult  to  attain. 

18.  All  the   Articulata,  save   a   few  of  the  very  lowest  species,  possess  a 
distinct  head  at  one  end  of  the  body,  furnished  with  organs  of  special  sensa- 
tion, and  with  lateral  jaws  for  the  prehension  and  reduction  of  food  ;  and  their 
movements,  being  principally  guided  by  the  special  senses,  take  place  in  this 
direction.     The  bi-laterai   symmetry  of  the  body  is  not  confined  to  its  exte- 
rior ;  for  it  prevails  most  completely  in  the  whole  muscular  apparatus  ;  and 
even  the  organs  of  nutrition  present  more  distinct  traces  of  it  than  are  to  be 
seen  elsewhere.     The  compact  heart  of  the   Mollusca,  for  instance,  is  here 
replaced  by  a  long  tube,  the  dorsal  vessel,  placed  on  the  median  line ;  and  the 
respiratory  organs,  which  are  usually  diffused  through  the  whole  system,  are 
uniform  on  the  two  sides.     Even  the  intestinal  canal  partakes  of  this  symme- 
try ;  in  some  species  it  runs  straight  from  end  to  end  of  the  body ;  and  even 
where  it  is   otherwise  disposed,  its  appendages  are  nearly  equal  on  the  two 
sides.     The  respiration  of  this  group  is  for  the  most  part  aerial ;  and  the  ap- 
paratus for  the  purpose  consists  of  a  series  of  chambers  or  tubes,  which  are 
dispersed  or  extended  through  the  whole  body,  and  which  are  expanded  at 
certain  points,  in  insects  possessing  considerable  powers  of  flight,  into  large 
air-sacs.     By  this  means,  the  air,  the  blood,  and  the  tissue  to  be  nourished, 
are  all  brought  into  contact  at  the  same  points  ;  and  a  much  less  vigorous  cir- 
culation is  required  than  would   otherwise  be  needed  ;  whilst,  at  the  same 
time,  the  specific  gravity  of  the  body  is  diminished,  and  flight  thereby  rendered 
more  easy.     The  whole  apparatus  of  nutrition  is  comprised  within  a  compa- 
ratively small  part  of  the  body ;  and  the  bulk  of  the  organs  which  compose 

o 


50  OX  THE  PLACE  OF  MAN  IN  THE  SCALE  OF  BEING. 

it,  is  never  at  all  comparable  with  that  which  we  ordinarily  find  in  the  Mol- 
lusca. Thus,  the  liver,  which  in  the  Oyster  forms  a  large  part  of  the  whole 
substance,  is  often  scarcely  recognizable  as  such  in  the  Insect;  and  the  intes- 
tinal tube  seldom  makes  many  convolutions  in  its  course  from  one  extremity 
to  the  other.  The  blood  is  usually  white,  as  in  the  other  Invertebrated  classes  : 
but  it  contains  a  larger  number  of  corpuscles  than  are  seen  in  that  of  most  of 
the  Mollusca.  The  temperature  varies  to  a  certain  degree  with  that  of  the 
atmosphere  ;  but  many  Insects  have  the  power  of  generating  a  large  amount  of 
independent  heat,  which  is  strictly  proportionable  to  the  quantity  of  oxygen 
converted  by  them  into  carbonic  acid  in  the  respiratory  process.  All  the  ac- 
tions of  the  Articulata  are  performed  with  great  energy ;  and,  at  the  time  of 
the  most  rapid  increase  of  the  body,  the  demand  for  food  is  so  great,  that  a 
short  suspension  of  the  supply  of  aliment  is  fatal.  Many  of  them  are  capa- 
ble, however,  of  being  submitted  to  the  influence  of  very  extreme  temperatures, 
with  little  permanent  injury. 

19.  The  adjoining  figure,  which  displays  the  muscular  apparatus  of  the 
interior  of  the  body  of  a  Cock-chafer,  will  give  an  idea  of  its  complexity  and 
variety,  and  of  the  large  portion  of  the  trunk  which  is  occupied  by  it ;  and 
will  also  show  the  division  of  the  skeleton  into  segments,  the  number  of 
which  in  Insects  is  limited  to  thirteen.  These  are  nearly  equal  and  similar 
to  each  other  in  the  Larva  ;  but,  in  the  perfect  Insect,  the  three  behind  the 
head  are  united  into  the  thorax,  to  which  the  legs  and  wings  are  attached; 
and  the  remainder  form  the  abdomen,  which  has  little  concern  in  locomotion. 


Section  of  the  trunk  of  Melolontha  vulgaris,  (after  Strauss-Durckheim.)  showing  the  complexity  of  the 
Muscular  system.  The  first  segment  of  the  thorax  (2)  is  chiefly  occupied  by  the  muscles  of  the  head, 
and  by  those  of  the  first  pair  of  legs  The  second  and  third  segments  (3  and  4)  contain  the  very  large 
muscles  of  the  wings,  and  those  of  the  other  two  pairs  of  legs.  The  chief  muscles  of  ihe  abdomen  ara 
the  long  dorsal  and  abdominal  recti,  which  move  the  several  segments  one  upon  the  other. 

6.   General  characters  of  Vertebrata. 

20.  In  none  of  the  three  preceding  divisions  of  the  Animal  kingdom,  does 
the  Nervous  System  attain  such  a  degree  of  development,  as  to  give  it  that 
predominance  in  the  whole  fabric  which  it  evidently  possesses  in  VERTE- 
BRATA. In  the  Radiata  and  Mollusca,  its  functions  are  obviously  restricted  to 
the  maintenance  of  the  nutritive  operations ;  and  to  the  guidance  of  the  ani- 
mal, by  means  of  its  sensory  endowments,  in  the  choice  of  food,  as  well  as 
(in  some  instances)  in  the  search  for  an  individual  of  the  opposite  sex:  in  the 


GENERAL  CHARACTERS  OF  VERTEBRATA.  51 

Articulata,  its  purpose  appears  similar,  but  is  carried  into  effect  in  a  different 
manner,  the  locomotive  organs  being  the  parts  chiefly  supplied  by  it.  In  the 
Vertebrata,  on  the  other  hand,  the  development  of  all  the  other  organs  appears 
to  be  subordinate  to  that  of  the  Nervous  System  ;  their  object  being  solely  to 
give  to  it  the  means  of  the  exercise  of  its  powers.  This  statement  is  not,  of 
course,  as  applicable  to  the  lower  Vertebrata,  as  it  is  to  the  higher  ;  but  it  is 
intended  to  express  the  general  character  of  the  group.  The  predominance 
of  the  nervous  system  is  manifested,  not  only  in  the  increased  size  of  its  cen- 
tres, but  also  in  the  special  provision  which  we  here  find,  for  the  protection 
of  these  from  injury.  In  the  Invertebrated  classes,  wherever  the  nervous  sys- 
tem is  inclosed  in  any  protective  envelope,  that  envelope  serves  equally  for 
the  protection  of  the  whole  body.  This  is  the  case,  for  example,  in  regard 
to  the  spiny  integument  of  the  Star-fish,  the  shell  of  the  Mollusca,  and  the 
firm  jointed  rings  of  the  Insect.  The  only  exceptions  occur  in  a  few  tribes, 
in  which  the  nervous  system  is  much  concentrated ;  and  in  which  the  general 
organization  approaches  that  of  the  Vertebrata.*  In  Vertebrated  animals,  we 
find  that  the  skeleton  essentially  consists  of  a  series  of  parts,  which  are  de- 
stined to  inclose  the  nervous  centres,  and  to  give  attachment  on  their  exterior 
to  the  muscles  by  which  the  body  is  moved  ;  hence  it  may  be  termed  the 
neuro-skeleton  ;  in  contradistinction  to  the  dermo- skeleton,  which  envelopes 
the  whole  body  in  many  Invertebrata,  being  formed  on  the  basis  of  their  in- 
tegument. The  tissues,  bone  and  cartilage,  of  which  the  former  is  composed, 
are  more  closely  connected  with  the  vascular  system,  than  are  the  hard  parts 
of  Invertebrata  ;  and  are  consequently  more  capable  of  undergoing  interstitial 
change. 

21.  In  considering  the  essential  character  of  the  skeleton  of  Vertebrata,  we 
should  look  at  its  simplest  forms, — those  in  which  it  has  the  least  number  of 
superadded  parts.     We  find  these  in  the  Serpent  tribe,  among  Reptiles,  and 
in  the  Eel  and  its  allies  among  Fish.     If  we  examine  their  skeletons,  we  per- 
ceive that  the  Spinal   Column,  with   the  Cranium  at  its  anterior  extremity, 
constitutes  the  essential  part  of  the  verteb rated  frame-work  ;  and  that  the  de- 
velopment of  members   is   secondary  to   this.     The  Spinal  Column  usually 
consists  of  a  number  of  distinct  bones,  the  Vertebrae  ;  each  of  which  is  per- 
forated by  a  large  aperture,  in  such  a  manner  that,  when  the  whole  is  united, 
a  continuous  tube  is  formed  for  the  lodgment  of  the  spinal  cord.     The  Cra- 
nium, which  it  bears  at  its  upper  end,  is  in  reality  formed  of  the  same  elements 
as  the  vertebrae,  instead  of  differing  from  them  completely  in  structure,  as  we 
might  be  led  to  suppose  by  examination  of  its  most  developed  forms  only. 
The  object  of  this  enlargement  is  to   inclose   the   brain,  or   mass  of  cephalic 
ganglia,  which  attains  a  greatly-increased  size  in  the  Vertebrata;  and  also  to 
afford  support  and  protection  to  the  organs  of  special   sense,  which  are  far 
more  highly  developed  among  them  than  they  are  in  the  lower  classes.     The 
true  nature  of  the  cranium  is  best  seen  in  those  animals,  in  which  the  brain 
bears  but  a  small  proportion  to  the   spinal   cord,  such  as  the  lower  Reptiles 
and  Fishes ;  and  an  examination  of  its  structure  in  these  satisfactorily  proves 
the  reality  of  this  view,  which  is  further  borne  out  by  the  history  of  its  de- 
velopment, and  of  that  of  its  contained  parts,  in  the  higher  Vertebrata. 

22.  The  Vertebral  column  at  its  opposite  extremity,  is  usually  contracted 
instead  of  being  dilated, — forming  a   tail,  or  a  rudiment  of  one,  from  which 
the  nervous  centres  are  entirely  withdrawn  ;  the  development  of  the  tail  is 

*  Thus,  in  the  highest  Crustacea,  there  is  an  -internal  projection  from  the  shell,  on  each 
side  of  the  median  line,  which  forms  a  sort  of  arch  inclosing  the  ventral  cord ;  and  in  the 
naked  Cephalopoda,  the  nervous  centres  are  supported,  and  in  part  protected,  by  cartilagi- 
nous plates,  which  are  evidently  the  rudiments  of  the  internal  skeleton  of  the  Vertebrata. 


52  ON  THE  PLACE  OF  MAN  IN  THE  SCALE  OF  BEING. 

commonly  seen  to  be  in  an  inverse  proportion  to  that  of  the  cranium.  To 
this  column,  the  ribs  and  extremities  are  merely  appendages,  which  we  find 
more  or  less  developed  in  the  various  tribes,  and  often  entirely  absent ;  whilst 
t.he  vertebral  column  is  never  wanting,  although  reduced  in  some  species  to  a 
very  rudimentary  state.  It  is  interesting  to  compare  its  various  conditions, 
with  those  which  have  been  noticed  in  the  external  skeleton  of  the  Articulata. 
In  the  lowest  animals  of  the  group,  locomotion  is  principally  or  even  entirely 
performed  by  flexion  of  the  body  itself;  and  here,  as  in  the  worm  tribe,  we 
find  the  skeleton  extremely  flexible,  the  whole  being  comparatively  soft,  and 
its  divisions  indistinct.  This  is  the  case,  for  example,  in  the  Lamprey  and 
other  Cyclostome  fishes  :  in  which  there  is  no  distinct  division  into  vertebrae, 
the  spinal  column  scarcely  possessing  even  the  density  of  cartilage.  In  pro- 
portion, however,  as  distinct  members  are  developed,  and  the  power  of  loco- 
motion is  committed  to  them,  we  find  the  firmness  of  the  spinal  column  in- 
creasing, and  its  flexibility  diminishing  ;  and  in  Birds, — in  which,  as  in  In- 
sects, the  movements  of  the  body  through  the  air  are  effected  by  muscles  that 
must  have  very  firm  points  of  support, — the  vertebral  column  is  much  conso- 
lidated by  the  union  of  its  different  parts,  so  as  to  form  a  solid  frame-work. 
A.S  a  general  rule,  then,  the  mobility  of  the  extremities,  and  the  firmness  of 
the  vertebral  column,  vary  in  a  like  proportion.  The  number  of  these  ex- 
tremities in  Vertebrata  never  exceeds  four  ;  and  two  of  them  are  not  unfre- 
quently  absent.  The  power  of  locomotion  is  not  developed  to  nearly  the 
same  proportional  extent,  as  in  the  Articulata ;  the  swiftest  bird,  for  example, 
not  passing  through  nearly  so  many  times  its  own  length  in  the  same  period, 
as  a  large  proportion  of  the  Insect  tribes  :  but  it  is  far  greater  than  that,  which 
is  characteristic  of  the  Mollusca  ;  and  there  is  no  species  that  is  fixed  to  one 
spot,  without  the  power  of  changing  its  place.  On  the  other  hand,  the  high- 
est Mollusca  approach  them  very  nearly  in  the  development  of  organs  of  spe- 
cial sense,  of  which  Vertebrata  almost  invariably  possess  all  four  kinds — sight, 
hearing,  smell,  and  taste. 

23.  The  perfection  of  the  Articulate  structure  has  been  shown  to  consist 
in  the  development  of  those  powers  which  enable  the  animal  to  perform 
actions  denoting  the  highest  instinctive  faculties.  That  of  the  Vertebrata 
evidently  tends  to  remove  the  animal  from  the  dominion  of  undiscerning, 
uncontrollable,  instinct;  and  to  place  all  its  operations  under  the  dominion  of 
an  intelligent  will.  We  no  longer  witness  in  these  operations  that  uniformity, 
which  has  been  mentioned  as  so  remarkable  a  characteristic  of  instinctive 
actions.  There  is  evidently,  among  the  higher  Vertebrata  especially,  a  power 
of  choice  and  of  determination,  guided  by  a  perception  of  the  nature  of  the 
object  to  be  attained,  and  of  the  means  to  be  employed,  constituting  the 
simplest  form  of  the  reasoning  faculty  ;  and  the  amount  of  this  bears  so  close 
a  relation  with  the  development  of  the  cerebrum,  that  it  is  scarcely  possible  to 
regard  the  two  as  unconnected.  In  Man,  whose  cerebrum  is  far  larger  in  pro- 
portion to  his  size,  as  well  as  more  complex  in  its  structure,  than  that  of  any  other 
animal,  the  reasoning  faculties  attain  the  highest  perfection  that  we  know  to 
be  anywhere  manifested  by  them  in  connection  with  a  material  instrument ; 
the  instinctive  propensities  are  placed  under  their  subjection;  and  all  his  acts, 
excepting  those  immediately  required  for  the  maintenance  of  his  organic  func- 
tions, are  put  under  their  control.  It  is  to  Man,  therefore,  that  what  was  just 
now  stated,  of  the  predominance  of  the  nervous  system  in  Vertebrata,  parti- 
cularly applies  ;  but  the  same  may  be  noticed,  though  in  a  less  striking  degree, 
throughout  the  group.  Not  only  is -the  influence  of  the  nervous  system  to  be 
traced,  in  the  sensible  movements  which  they  perform ;  but  also  in  various 
modifications  of  the  organic  functions,  which  take  place  under  the  influence 
of  particular  states  of  mind,  and  the  occurrence  of  which  there  is  no  reason 


GENERAL  CHARACTERS  OF  VERTEBRATA.  53 

to  suspect  in  the  lower  tribes  of  animals.  These  are  even  much  more  strik- 
ing in  Man,  than  in  the  lower  Vertebrata;  indeed  the  comparative  slightness 
of  the  influence  of  the  mind  upon  the  body,  is  one  of  the  causes  which  ren- 
der the  lower  Mammalia  more  able  than  Man  is  to  recover  from  the  effects 
of  severe  injuries.  The  Mollusca  seem  to  grow  like  plants ;  their  massive 
organs  increasing  by  their  own  separate  vitality,  and  being  but  little  depend- 
ent upon  each  other.  Even  the  act  of  respiration,  which  is  in  most  animals 
performed  by  a  series  of  distinct  muscular  contractions,  is  there  principally 
effected  through  the  medium  of  the  cilia  which  clothe  the  respiratory  surface. 
But  in  the  Vertebrata,  the  nervous  system  possesses  a  distinct  and  independ- 
ent rank ;  its  offices  are  those  which  more  particularly  constitute  the  active 
life  of  the  animal ;  the  organic  functions  have  for  their  chief  object,  the  main- 
tenance of  the  nervous  and  muscular  apparatus  in  the  condition  requisite  for 
their  activity ;  and  in  consequence,  all  these  different  kinds  of  apparatus  are 
so  interwoven  together,  that  their  mutual  dependence  is  very  close. 

24.  The  foregoing  remarks  will  be  found  to  have  an  important  bearing  on 
the  details  subsequently  to  be  given  respecting  the  functions  of  the  Nervous 
system  in  Man ;  and  it  is  desirable  to  set  out  with  clear  ideas  on  this  subject, 
since  there  is  no  department  of  Physiology,  regarding  which  more  error  is 
prevalent.     There  is  no  valid  reason  for  believing  that  the  Organic  functions 
in  Animals,  any  more  than  the  corresponding  changes  in  Plants,  are  depend- 
ent on  the  nervous  system  for  their  performance ;  but  common  observation 
shows,  that  they  are  much  influenced  by  it  in  the  higher  animals ;  and  from 
such  a  comparison  as  that  which  has  been  just  now  briefly  made,  it  would 
appear  that,  the  higher  the  general  development  of  the  nervous  system,  the 
closer  is  their  relation  with  it. 

25.  This  general  character  of  the  Vertebrata  harmonises  well  with  what 
may  be  observed,  on  a  cursory  glance  at  the  structure  of  their  bodies,  as  to 
the  proportion  between  the  organs  of  Nutritive  and  those  of  Animal  life.    The 
former,  contained  in  the  cavities  of  the  trunk,  are  highly  developed ;  but,  as  in 
the  Mollusca,  they  are  for  the  most  part  unsymmetrically  disposed.     Of  the 
latter,  the  nervous  system  and  organs  of  the  senses  occupy  the  head ;  whilst 
the  muscles  of  locomotion  are  principally  connected  with  the  extremities : 
both  are  symmetrical,  as  in  the  Articulata;  but,  whilst  that  part  of  the  nerv- 
ous centres,  which  is  the  instrument  of  reason,  is  very  largely  developed,  the 
portion  which  is  specially  destined  to  locomotion,  together  with  the  muscular 
system  itself,  bears  much  the  same  proportion  to  the  whole  bulk  of  the  body, 
as  it  does  in  the  Articulated  series.     Hence  we  observe  that  the  Vertebrata 
unite  the  unsymmetrical  apparatus  of  nutrition,  characteristic  of  the  Mollusca, 
with  the  symmetrical  system  of  nerves  and  muscles  of  locomotion,  which  is 
the  prominent  characteristic  of  the  Articulata;  both,  however,  being  rendered 
subordinate  to  the  great  purpose  to  be  attained  in  their  fabric, — the  develop- 
ment of  an  organ,  through  which  intelligence  peculiarly  manifests  itself.     For 
the  operations  of  this,  a  degree  of  general  perfection  is  required,  which  is 
not  met  with  elsewhere.     The  higher  Vertebrata  have  a  power  of  constantly 
keeping  the  temperature  of  the  body  up  to  a  point,  which  it  can  only  attain 
occasionally,  and  under  peculiar  circumstances,  in  the  Articulata,  and  which 
it  never  reaches  in  the  Mollusca.     This  involves  an  energetic  performance  of 
the  functions  of  respiration  and  circulation  ;  and  these  again  require  consider- 
able activity  of  digestion.     All  the  Vertebrata  have  red  blood,  which  is  pro- 
pelled through  the  system  by  a  distinct  muscular  heart;  and  the  number  of 
red  corpuscles,  which  any  given  amount  of  the  fluid  contains,  bears  a  nearly 
constant  proportion  to  the  ordinary  temperature  of  the  'animal.     They  are 
further  distinguished  from  Articulata  by  a  character  which  seems  of  little  im- 
portance, but  which  is  very  constant  in  each  group.     Whilst  the  mouth  of  the 

5* 


54  ON  THE  PLACE  OF  MAN  IN  THE  SCALE  OF  BEING. 

latter  is  furnished  with  two  or  three  pairs  of  jaws  which  open  sideways,  that 
of  the  former  has  never  more  than  one  pair  of  jaws,  which  are  placed  one 
above  or  before  the  other;  and  these  jaws  are  usually  armed  with  teeth,  which 
are  very  analogous  in  their  structure  to  bone. 

7.   General  characters  of  Fishes. 

26.  The  Vertebrata  are  subdivided  into  classes,  principally  according  to 
their  mode  of  performing  the  functions  of  respiration  and  reproduction.  Thus, 
FISHES  are  at  once  separated  from  all  other  groups,  by  the  circumstances  of 
their  being  adapted,  like  the  aquatic  Invertebrata,  to  aerate  their  blood  by 
gills ;  and  being  hence  enabled  to  inhabit  water  during  their  whole  lives, 
without  the  necessity  of  coming  to  the  surface  to  breathe.  The  low  amount 
of  their  respiration  prevents  their  bodies  from  ever  attaining  a  temperature 
much  above  that  of  the  surrounding  medium ;  hence  they  are  spoken  of  as 
cold-blooded.  Further,  they  are  oviparous  ;  an  ovum  or  egg  being  deposited 
by  the  parent,  from  which,  in  due  time,  the  young  makes  its.  way ;  or  if,  as 
sometimes  happens,  the  ovum  is  retained  within  the  body  of  the  parent  until 
it  is  hatched,  the  young  animal,  though  produced  alive,  is  not  subsequently 
dependent  upon  its  parent  for  support.  In  many  respects,  the  organization 
of  Fishes  is  not  much  advanced  beyond  that  of  the  higher  Mollusca.  Their 
respiratory  apparatus  has  the  same  character;  and  the  organs  by  which  the 
blood  is  depurated  of  its  superfluous  azote,  rather  correspond  with  the  tem- 
porary Corpora  Wolffiana  of  higher  animals,  than  with  their  true  Kidneys 
(CHAP.  XV.  3).  The  vertebral  column  itself  is  often  very  imperfectly  deve- 
loped ;  in  a  large  proportion  of  the  group,  the  skeleton  is  cartilaginous  only  ; 
and  in  the  lowest  species,  it  does  not  even  manifest  a  trace  of  division  into 
vertebra.  Living  habitually  in  an  element,  which  is  nearly  of  the  same  speci- 
fic gravity  with  their  own  bodies,  Fishes  have  no  weight  to  support,  and  have 
only  to  propel  themselves  through  the  water.  Accordingly  we  find  their 
structure  adapted  rather  for  great  freedom  of  motion,  than  for  firmness  and 
solidity ;  and  as  progressive  motion  is  chiefly  effected  by  the  lateral  action  of 
the  spine,  the  vertebrae  are  so  united,  as  to  move  very  readily  upon  one  ano- 
ther. Instead  of  being  articulated  together  by  surfaces  nearly  flat,  as  in 
Mammalia,  or  by  ball-and-socket  joints,  as  in  Serpents,  they  have  both  their 
surfaces  concave  :  and  these  glide  over  a  bag  of  fluid  (the  representative  of  the 
intervertebral  substance  in  the  higher  animals),  which  is  interposed  between 
each  pair.  The  tail  is  flattened  vertically  ;  so  as,  by  its  lateral  stroke,  to  pro- 
pel the  Fish  through  the  water.  By  this  character,  true  Fishes  are  distin- 
guished from  those  aquatic  Mammalia,  which  are  adapted  to  inhabit  their 
element,  and  which  commonly  receive  the  same  designation ;  for  the  latter, 
being  air-breathing  Animals,  are  obliged  to  come  frequently  to  the  surface  to 
respire ;  and  their  tail  is  flattened  horizontally,  to  enable  them  to  do  this  with 
facility.  The  lateral  surface  of  the  body  of  Fish  is  further  extended  above,  by 
the  projection  of  the  dorsal  fin,  which  is  supported  on  the  spinous  processes  of 
the  vertebra? ;  and  below,  by  the  abdominal  fin,  which  also  is  placed  on  the 
median  line ;  these  will,  of  course,  increase  the  power  of  the  lateral  stroke  of 
the  body,  and  can  only  be  moved  with  the  spine.  The  pectoral  and  ventral 
fins,  on  the  other  hand, — the  former  of  which  answer  to  the  superior  extre- 
mities, and  the  latter  to  the  inferior  extremities,  of  Man, — serve,  by  their  in- 
dependent movements,  rather  as  steering  than  as  propelling  organs ;  and  they 
also  assist  in  raising  and  depressing  the  animal  through  the  water.  The 
scales  with  which  the  bodies  of  all  Fishes  are  covered,  are  frequently  of  a 
bony  hardness,  and  sometimes  form  a  firmly-jointed  casing,  in  which  the 
trunk  is  completely  inclosed ;  this  is  especially  the  case,  when  the  internal 


GENERAL  CHARACTERS  OF  REPTILES.  55 

skeleton  is  imperfectly  developed  ;   so  that  here  we  have  an  approach  to  the 
character  of  the  Invertebrata. 

27.  The  swimming-bladder,  as  it  is  commonly  termed,  of  the  Fish,  is  not 
an  organ  sui  generis  ;  but  is  ascertained,  by  comparison  with  the  pulmonary 
sacs  of  the  lower  Reptiles,  to  be  a  rudimentary  lung.     It  does   not,  however, 
give  any  assistance  in  the  aeration  of  the   blood,  except  in   a  few  instances ; 
but  seems  to  be  in  general  subservient  to  the  elevation  and  depression  of  the 
body  in  its  element.     The  heart  of  the  Fish  is  extremely  simple  in  its  con- 
struction, containing  two  cavities  only;  and  the  course  of  the  circulation  is 
equally  simple.     The  blood  which  returns  from  the  body  in  a  venous  condi- 
tion, is  received  into  the  single  auricle  or  recipient  cavity ;   and  from   this  it 
passes  into  the  ventricle  or  propellent  cavity.     The  latter  forces  it  into  a  large 
trunk,  which  subdivides   into  branches   that  are  distributed  to  the  branchial 
arches  on  each  side ;   and  in   these  it  undergoes   aeration.     Being  collected 
from  the  gills  by  returning  vessels,  the  blood,  now  become  arterial  in  its  cha- 
racter, is  transmitted  to  the  large  systemic  trunk,  the  aorta,  by  which  it  is  dis- 
tributed through  the  system, — returning  again  to  the  heart,  when  it  has  passed 
through   the  organs  and  tissues  of  the  body.     Hence   it  is   evident  that  the 
whole  of  the  blood  passes  through  the  gills,  before  it  goes  a  second  time  to  the 
system ;  by  which  the  imperfection  of  the  aerating  process  itself  is  in  some 
degree   compensated.     There  is   a  special  provision,  too,  for  renewing  by 
muscular  power  the  stratum  of  water  in  contact  with  the  gills  ;  continual  cur- 
rents being  sent  over  them  from  the  pharynx,  with  which  their  cavity  com- 
municates.    It  is  worth  noticing,  that  whilst,  in  the  Osseous  Fishes,  there  is 
a  single  large  external-gill  opening  on  either  side,  with  a  valve-like  opercu- 
lum  or  gill-cover,  there  are,  in  the  Cartilaginous  Fishes,  several  slits  on  each 
side  of  the  neck,  one  corresponding  with  each  branchial  arch.     Similar  aper- 
tures in  the  neck  may  be  seen  in  the  embryo  of  Man  and  of  other  Mammalia, 
as  well  as  of  Birds  and  Reptiles,  at  the  time  that  the  circulation  is  in  the  con- 
dition of  that  of  the  Fish, — the  heart  possessing  only  two  cavities,  and  the 
blood  being  first  propelled  through  a  series  of  branchial  arches. 

.     8.   General  characters  of  Reptiles. 

28.  The   class  of  REPTILES   is  oviparous   and  cold-blooded,  like  that  of 
Fishes ;   but  the   animals  belonging  to  it  are  formed   to  breathe  air,  and  to 
inhabit  the  surface  of  the  earth, — the   few  which   are  adapted  to  make  the 
water  their  dwelling,  being  obliged  to  come  to  the  surface  to  breathe.     Al- 
though they  breathe  air,  however,  their  respiration  is  not  usually  so  energetic 
as  that  of  Fishes,  and  their  general  activity  is  much  less.     The  mechanism 
for  the  inflation  of  their  lungs  is  very  imperfect.     Being  destitute  of  a  dia- 
phragm, they  are  obliged  to  force  air  into  the  chest,  by  a  process  resembling 
deglutition  or  swallowing;  so  that,  strange  as  it  may  seem,  a  Reptile  may  be 
suffocated  by  holding  its  mouth  open.     The  heart  possesses  three  cavities, 
one  of  which  receives  the  blood  from  the  lungs,  and  another  from  the  general 
system ;  the  arterial  and  the  venous  blood,  contained  in  these  two  auricles 
respectively,  are  transmitted  to  the  third  or  propelling  cavity,  the  ventricle, 
where  they  are  mixed ;   and  the  half-arterialised  fluid  is  then  transmitted  to 
the  system  at  large,  a  part  being  sent  to  the  lungs.     Thus  only  a  portion  of 
the  blood  expelled  from  the  heart  is  exposed  to  the  influence  of  the  air ;  and 
that  which  is   transmitted  to  the   body  is  very  imperfectly  arterialised.     In 
some  of  the  higher  Reptiles,  as  the  Crocodile,  the  ventricle  is  double,  as  in 
the  superior  Vertebrata ;  and  the  course  of  the  circulation  is  so  arranged,  that 
pure  arterial  blood  shall  go  to  the  head,  where  it  is  most  required,  whilst  a 
mixed  fluid  is  sent  to  the  rest  of  the 'body.     This  plan  exactly  corresponds 


56  ON  THE  PLACE  OF  MAN  IN  THE  SCALE  OF  BEING. 

with  the  one,  which  is  adopted  in  the  circulation  of  the  Human  foetus,  from 
the  time  of  the  formation  of  the  four  cavities  in  its  heart,  and  of  the  perma- 
nent system  of  vessels,  up  to  the  period  of  birth.  The  imperfect  arterialisa- 
tion  of  the  blood  in  Reptiles,  causes  a  great  degree  of  general  inertness  in 
their  functions.  Their  motions  are  principally  confined  to  crawling  and 
swimming ;  their  general  habits  are  sluggish,  and  their  sensations  are  obtuse ; 
and  their  nutritive  functions  are  very  slowly  performed.  Hence  they  can 
exist  for  a  long  time,  with  a  very  feeble  exercise  of  these  functions,  under 
circumstances  that  would  be  fatal  to  animals,  in  which  they  are  performed 
with  greater  activity.  In  cold  and  temperate  climes,  they  pass  the  whole 
winter  in  a  state  of  torpidity ;  and  at  other  seasons,  they  may  be  kept  during 
a  long  time  from  their  due  supplies  of  food  and  air,  without  appearing  to  suf- 
fer much  inconvenience. 

29.  In  regard  to  the  structure  of  their  skeleton,  and  the  external  form  of 
the  body,  there  is  a  considerable  variation  among  the  several  orders  of  Reptiles. 
Thus,  Tortoises,  Lizards,  and  Serpents,  differ  from  each  other  so  widely, 
that  a  common  observer  would   separate  them  completely ;  and  yet  they  not 
only  agree  in  all  the  foregoing  characters,  but  pass  into  one  another  by  links 
of  transition  so  gradual,  that  it  is  even  difficult  to  classify  them.     They  differ, 
however,  more  in  the  configuration  of  the  accessory  parts,  than  in  the  struc- 
ture of  the  essential  portion  of  the  skeleton, — the, spinal  column.     This  is 
characterised  by  the  ball-and-socket  articulation  of  the  vertebrae,  each  vertebra 
having  one  surface  convex  and  the  other  concave, — a  structure  which  is  more 
strongly  marked  in  Serpents,  whose  movements  are  performed  chiefly  by  the 
flexion  of  the  spinal  column  itself,  than  it  is  in  the  other  tribes.     The  chief 
characteristic  of  the  Tortoise  tribe,  is  the  shell  or  case  in  which  the  body  is 
contained.     The  upper  arch  of  this  shell,  termed  the  carapace,  is  formed  by 
a  bony  expansion  from  the  edges  of  the  ribs,  which  is  covered  by  a  set  of 
horny  plates,  that  are  to  be  regarded  (like  smaller  scales)  as  epidermic  appen- 
dages.    The  under  portion,  termed  the  plastron,  is  composed  of  the  sternum, 
which  is  in  like  manner  extended  laterally.     In  the  Land-tortoises,  this  usu- 
ally forms  a  complete  floor ;  but  in  the  aquatic  species,  a  part  is  commonly 
absent,  the  interval  being  filled  up  by  cartilage  and  membrane.     The  skeleton 
of  the  Lizards  is  formed  more  upon  the  general  plan  of  that  of  Mammalia, 
but  may  be  readily  distinguished  from  it.     The  sternum  is  usually  prolonged 
over  the  front  of  the  abdomen,  and  the  ribs  are  continued  through  a  much 
larger  part  of  the  spinal  column ;   of  these   abdominal  ribs,  the  white  lines 
across  the  recti  muscles  in  the  higher  Vertebrata,  are  evidently  the  rudiments. 
In  the  higher  Lizards,  the  power  of  locomotion  is  almost  entirely  delegated 
to  the  extremities  ;  but  in  the  less  typical  species,  the  body  and  tail  are  much 
prolonged,  so  as  to  present  a  serpentiform  aspect ;  and  first  one  pair  of  feet, 
and  then  the  other,  disappear,  until  the  form  is  altogether  that  of  the  Serpent. 
Even   in    Serpents,  however,  rudiments  of  extremities   are  frequently  to  be 
found ;   but  their  mode  of  progression  is  very  different,  and  these  rudiments 
are  of  no  assistance  to  them.     The  most  remarkable  feature  in  the  Serpent's 
skeleton,  besides  the  absence  of  legs,  and  the  large  number  of  ribs  and  verte- 
brae, is  the  deficiency  of  a  sternum ;  through  the  absence  of  this,  the  extremi- 
ties of  the  ribs  are   free,  and  they  become  in  fact  the  fixed  points,  on  which 
the  animal  crawls,  when  advancing  slowly  forwards,  in  a  manner  which  bears 
a  strong  resemblance  to  the  progression  of  the  Centipede. 

30.  Although  the  configuration  of  the  cranium  varies  much  in  the  different 
orders  of  Reptiles,  yet  there  is  a  remarkable  agreement  in  certain  general  cha- 
racters, and  in  the  general  degree  of  development.     It  consists  of  a  much 
larger  number  of  parts,  than  are  to  be  found  in  the  cranium  of  adult  Birds  or 
Mammalia ;  each  principal  bone  being  subdivided,  as  it  were,  into  smaller  ones. 


GENERAL  CHARACTERS  OF  REPTILES.  57 

This  condition  exactly  corresponds  with  that,  which  may  be  observed  during 
the  process  of  ossification  in  higher  Vertebrata ;  for  each  of  the  larger  bones 
of  the  cranium  is  formed  from  several  centres  of  ossification  ;  so  that,  if  the 
cranium  of  a  foetus  or  young  infant  be  macerated,  it  will  fall  into  a  number  of 
pieces  nearly  corresponding  with  those  of  the  Reptile's  skull.  The  different 
orders  of  Reptiles  have  a  close  agreement  in  various  other  points  ;  especially 
in  the  degree  of  development  of  their  several  organs  of  nutrition.  Thus,  in 
all  of  them,  the  lungs,  though  commonly  of  large  size,  are  so  little  subdivided, 
as  really  to  expose  but  a  small  extent  of  surface.  The  glandular  structures, 
too,  are  formed  upon  a  much  more  simple  type,  than  is  characteristic  of  the 
warm-blooded  Vertebrata.  They  all  agree,  moreover,  in  having  the  body 
covered  with  scales ;  which,  though  generally  small,  are  sometimes  large  flat- 
tened plates. 

31.  Between  Fishes  and  true  Reptiles,  there  is  a  group  that  remarkably 
combines  the  characters  of  both ;  being  composed  of  animals  which  come 
forth  from  the  egg  in  the  condition  of  Fishes,  but  which  afterwards  attain  a 
form  and  structure  closely  corresponding  with  that  of  true  Reptiles.  This 
group,  consisting  of  the  Frog  and  its  allies,  is  sometimes  associated  as  an  or- 
der (Batrachia)  of  the  class  of  Reptiles  ;  though  it  should  probably  take  rank 
as  a  distinct  class,  the  AMPHIBIA.  The  Tadpole  or  larva  of  the  Frog  is  in 
every  essential  respect  a  Fish.  Its  respiration  and  circulation,  its  digestion 
and  nutrition,  its  locomotion  and  sensation,  are  entirely  accordant  with  those 
of  Fishes.  The  body  is  destitute  of  members  for  progression,  but  is  propelled 
through  the  water  by  the  lateral  undulations  of  the  spinal  column,  which  is 
articulated  in  the  same  manner  as  that  of  Fishes.  At  a  certain  period,  a  me- 
tamorphosis commences  in  which  almost  every  organ  in  the  body  undergoes 
an  essential  change.  Lungs  are  developed,  which  take  the  place  (in  regard 
to  their  function)  of  the  gills  ;  and  the  latter  are  atrophied.  The  auricle  of 
the  heart  is  divided  into  two ;  and  the  circulation  is  performed  on  the  plan  of 
that  of  the  true  Reptile.  Two  pairs  of  members  are  usually  formed,  to  which, 
when  they  are  fully  developed,  the  power  of  progression  is  committed, — the 
tail  disappearing ;  in  some  species,  however,  the  tail  remains,  and  the  extre- 
mities are  small.  The  digestive  system  undergoes  a  remarkable  alteration  ; 
the  intestinal  canal,  which  was  previously  of  enormous  length  in  proportion 
to  the  body,  being  now  considerably  shortened,  in  accordance  with  the  differ- 
ent kind  of  food  on  which  the  animal  has  to  subsist.  The  mode  of  articu- 
lation of  the  spinal  column  also,  undergoes  a  change,  which  brings  it  to  the 
type  of  that  of  Reptiles.  The  most  obvious  point  of  difference  in  external 
characters,  between  the  higher  Amphibia  and  true  Reptiles,  is  the  absence  of 
scales  or  plates  on  the  skin  of  the  former.  In  this  manner,  the  common  Sala- 
mander or  Water-Newt  may  be  recognised  as  belonging  to  the  Batrachia 
though  its  form  would  otherwise  lead  us  to  place  it  among  the  Lizards ;  and 
the  Ccecilia,  which  has  the  form  of  the  Serpent,  is  in  like  manner  known  to 
be  really  allied  to  the  Frog.  An  acquaintance  with  the  history  of  these  ani- 
mals confirms  such  an  arrangement,  by  showing  that  the  Salamander  and  the 
Co3cilia  undergo  a  metamorphosis  ;  breathing  by  gills,  and  having  the  general 
structure  of  Fishes,  in  the  early  part  of  their  lives. 

32.  Besides  those  animals,  however,  which  attain  the  condition  of  perfect 
Reptiles,  this  group  contains  several,  whose  development  is  arrested,  as  it 
were,  in  an  intermediate  or  transition  state  ;  their  adult  form  presenting  a  re- 
markable mixture  of  the  characters  of  the  two  classes,  which  they  thus  con- 
nect. This  is  the  case  in  the  Proteus,  Siren,  and  other  less  known  species, 
which  retain  their  gills  through  the  whole  of  their  lives,  whilst  their  lungs  are 
at  the  same  time  developed ;  so  that,  as  they  can  respire  in  either  air  or  wa- 
ter, they  are  the  only  true  amphibious  animals.  In  their  general  organization, 


58  ON  THE  PLACE  OF  MAN  IN  THE  SCALE  OF  BEING. 

they  correspond  with  the  Tadpole  of  the  Frog  at  an  advanced  period  of  its 
metamorphosis  ;  and  it  is  a  most  interesting  fact  (which  has  been  established 
by  the  experiments  of  Dr.  W.  F.  Edwards)  that,  if  Tadpoles  be  kept  in  such 
a  manner,  as  to  be  amply  supplied  with  food,  and  exposed  to  a  constantly- 
renewed  current  of  water,  but  be  secluded  from  light  and  from  the  direct  in- 
fluence of  the  solar  heat,  they  will  continue  to  grow  as  Tadpoles  ;  their  me- 
tamorphosis being  checked.  The  metamorphosis  of  the  Batrachia  closely 
corresponds  with  that  of  Insects  ;  the  young  animal,  in  each  case,  at  the  time 
of  its  emersion  from  the  egg,  having  a  resemblance,  in  all  essential  particulars, 
to  a  class  below  that  to  which  it  is  ultimately  to  belong.  This  kind  of  meta- 
morphosis is  by  no  means  confined  to  them,  however ;  for  the  gradual  exten- 
sion of  our  knowledge  of  the  early  history  of  the  different  tribes  of  animals, 
is  constantly  bringing  to  light  new  facts  of  the  same  kind.  The  Polypes  and 
lower  Mollusca,  for  instance,  come  forth  from  the  egg,  and  swim  about  for 
some  time,  in  a  condition  which  can  scarcely  be  termed  animal;  for  there  is 
not  even  a  mouth  leading  to  a  digestive  cavity  ;  nor  are  there  any  other  or- 
gans of  locomotion  than  the  cilia,  the  action  of  which  is  involuntary.  And, 
in  tracing  the  development  of  the  Human  embryo,  we  shall  find  that  it  under- 
goes a  series  of  progressive  changes  equally  remarkable; — the  principal  differ- 
ence being,  that  these  changes  are  not  so  arranged  in  harmony  with  each 
other,  as  to  cause  the  embryo  to  present,  at  any  one  time,  the  combination  of 
characters  which  belong  to  the  Fish,  Reptile,  &c.,  or  to  enable  it  to  sustain  an 
independent  existence. 

9.   General  characters  of  Birds. 

33.  From  Reptiles  to  BIRDS,  the  transition  would  seem  rather  abrupt ;  since 
the  latter  class  is,  in  almost  every  respect,  the  opposite  of  the  former.     Never- 
theless, it  would  seem  to   have   been  effected  by  the  now-extinct  Pterodac- 
tylus,  which  combined,  in  a  most  remarkable  degree,  the  characters  of  the 
two  groups.     Birds  are,  like  Fishes  and  Reptiles,  oviparous  Vertebrata  ;  but 
they  differ  essentially  from  both,  in  being  warm-blooded,  and  in  affording  as- 
sistance by  their  own  heat  in  the  development  of  the  ovum.    Birds  correspond 
with  Mammalia,  in  possessing  a  heart  with  four  cavities,  and  a  complete  dou- 
ble circulation  ;  by  which  the  whole  of  the  blood  that  has  circulated  through 
the  body,  is  exposed  to  the  influence  of  the  air  before  being  again  transmitted 
to  the  system.     This  high  amount  of  oxygenation  of  the  blood  is  accompa- 
nied by  great  activity  and  energy  of  all  the  organic  functions,  acuteness  of  the 
senses,  and  rapid  and  powerful  locomotion ;  as  well  as  by  the  evolution  of  a 
degree  of  heat,  superior  to  that  which  we  ordinarily  meet  with  among  the 
Mammalia.    The  temperature  of  Birds  ranges  from  about  104°  to  112°.    The 
lowest  is  in  the  aquatic  species,  whose  general  activity  is  much  less  than  that 
of  the  tribes  which  spend  most  of  their  time  in  the  air ;  the  highest  is  among 
those  distinguished  for  the  rapidity  and  energy  of  their  flight,  such  as  the 
Swallow. 

34.  Birds  have  been  denominated,  and  not  inappropriately,  the  Insects  of 
the  Vertebrated  series;  as  in  the  animals  of  that  class,  we  find  the  whole 
structure  peculiarly  adapted  to  motion,  not  in  water,  nor  upon  solid  ground, 
but  in  the  elastic  and  yielding  air.     It  is  impossible  to  conceive  any  more 
beautiful  series  of  adaptations  of  structure  to  conditions  of  existence,  than 
that  which  is  exhibited  in  the  conformation  of  the  Bird,  with  reference  to  its 
intended  mode  of  life.     In  order  to  adapt  the  Vertebrated  animal  to  its  aerial 
residence,  its  body  must  be  rendered  of  as  low  specific  gravity  as  possible. 
It  is  further  necessary  that  the  surface  should  be  capable  of  being  greatly  ex- 
tended ;  and  this  by  some  kind  of  appendage  that  should  be  extremely  light, 


GENERAL  CHARACTERS  OF  BIRDS.  59 

and  at  the  same  time  possessed  of  considerable  resistance.  The  degree  of 
muscular  power  required  for  support  and  propulsion  in  the  air,  involves  the 
necessity  of  a  very  high  amount  of  respiration  (§  275),  for  which  it  has  been 
seen  that  an  express  provision  exists  in  Insects;  and  as  the  general  activity 
of  the  vital  processes  depends  greatly  upon  the  high  temperature,  which  this 
energetic  respiration  keeps  up,  a  provision  is  required  for  keeping  in  this  heat, 
and  not  allowing  it  to  be  carried  away  by  the  atmosphere,  through  which  the 
Bird  is  rapidly  flying. 

35.  The  first  and  third  of  these  objects, — the  lightening  of  the  body,  and 
the  extension  of  the  respiratory  surface, — are  beautifully  fulfilled  in  a  mode, 
which  will  be  found  to  correspond  with  the  plan  adopted  for  the  same  purpose 
in  Insects.     The  air  which  enters  the  body,  is  not  restricted  to  a  single  pair 
of  air-sacs  or  lungs  placed  near  the  throat;  but  is  transmitted  from  the  true 
lungs,  to  a  series  of  large  air-cells,  disposed  in  the  abdomen  and  in  various 
other  parts  of  the  body.     Even  the  interior  of  the  bones  is  made  subservient 
to  the  same  purpose ;  being  hollow,  and  lined  with  a  delicate  membrane,  over 
which  the  blood-vessels  are  minutely  distributed.     In  this  manner,  the  respi- 
ratory surface  is  greatly  extended;  whilst,  by  the  large  quantity  of  air  intro- 
duced into  the  mass,  its  specific  gravity  is  diminished.     The  subservience  of 
the  cavities  in  the  bones  to  the  respiratory  function,  is  curiously  shown  by 
the  fact,  which  has  been  ascertained  both  accidentally  and  by  a  designed  ex- 
periment, that,  if  the  trachea  of  a  Bird  be  tied,  and  an  aperture  be  made  in 
one  of  the  long  bones,  it  will  respire  through  this. 

36.  The  other  two  objects, — the  extension  of  the  surface,  and  the  retention 
of  the  heat  within  the  body, — are  also  accomplished  in  combination,  by  a  most 
beautiful   and  refined  contrivance,  the   covering  of  feathers.     Like  hair  or 
scales,  feathers   are  to  be  regarded  as  appendages  to  the  Cutis;  the  stem  is 
formed  from  it  by  an  apparatus,  which  may  be   likened  to  a  hair-bulb  on  a 
very  large  scale  ;  but  there  are  some  additional  parts  for  the  production  of  the 
laminae,  which  form  the  vane  of  the  feather,  and  which  are  joined  to  the  stem 
during  its  development.     These  laminae,  when  perfectly  formed,  are  connected 
by  minute  barbs  at  their  edges,  which  hook  into  one  another,  and  thus  give 
the  necessary  means  of  resistance  to  the  air.     The  substance  of  which  feathers 
consists,  is  a  very  bad  conductor  of  heat ;  and  when  they  are  lying  one  over 
the  other,  small  quantities  of  air  are  included,  which  still  further  obstruct  its 
transmission  by  their  non-conducting  power.     Thus  the  two  chief  objects  are 
fulfilled; — power  of  resistance  and  slow-conducting  properties  being  obtained, 
in  combination  with  lightness  and  elasticity.     At  the  two  extremes  of  the 
class,  however,  we  meet  with  remarkable  modifications  in  the  typical  structure 
of  feathers.     In   the  Penguin,  those   which  cover  the  surface  of  the  wings 
have  a  strong  resemblance  to  scales  ;  and  the  wings  are  not  employed  to  raise 
this  Bird  in  the  air,  but  only  to  propel  it  through  water  (as  fins  would  do)  by 
their  action  on  the  liquid.     On  the  other  hand,  in  the  Ostrich  tribe,  the  laminae 
of  the  feathers  are  separated  from  each  other,  so  as  no  longer  to  form  a  con- 
tinuous surface ;  the  feathers  more  resembling  branching  hairs.     Here  the 
wings  are  almost  or  completely  absent;  the  birds  of  this  tribe  being  constantly 
upon  the  ground,  propelling  themselves   by  running,   and   approaching  the 
Mammalia  in  many  points  of  their  conformation. 

37.  The  bony  frame-work  of  Birds  presents  many  remarkable  adaptations 
to  the  same  purposes.     In  the  first  place  it  is  to  be  remarked,  that  the  faculty 
of  locomotion  is  here  entirely  delegated  to  the  extremities;  and  that  the  skele- 
ton of  the  trunk  must  be  consolidated,  in  proportion  to  the  power  with  which 
they  are   to  be  endowed,  in   order  to  afford  their  muscles  a  firm  attachment 
(§  22).     Just   as   the  segments   of  the  external  skeleton  of  the  Articulata, 
therefore,  are  consolidated  in  Insects,  do  we  find  that  the  vertebral  column 


60  ON  THE  PLACE  OF  MAN  IN  THE  SCALE  OF  BEING. 

and  its  appendages  are  firmly  knit  together,  in  the  upper  part  of  the  trunk  of 
Birds.  The  vertebra?  are  closely  united  to  each  other;  and  the  ribs  are  con- 
nected with  the  sternum  by  bony  prolongations  of  the  latter,  instead  of  by 
cartilages.  This  union  is  so  arranged,  that  the  state  of  expansion  is  natural 
to  the  thorax,  whilst  that  of  contraction  is  forced.  The  diaphragm  is  absent 
among  birds,  as  among  Reptiles  ;  except  in  a  few  species,  which  most  nearly 
approach  the  Mammalia.  But  its  deficiency  is  compensated  by  this  contriv- 
ance, which  keeps  the  lungs  and  air-sacs  always  full, — except  when  the  Bird 
by  a  muscular  effort,  expels  the  air  from  them,  in  order  that  they  may  be  re- 
filled by  a  fresh  supply.  By  this  means,  also,  the  specific  gravity  of  the  body  is 
more  constantly  kept  down,  than  it  could  have  been,  if  the  lungs  had  been 
subjected  to  the  constantly-alternating  contractions  and  expansions,  which  they 
perform  in  Mammalia.  It  is  worthy  of  remark,  that  the  air  which  enters  the 
bones  and  the  air-sacs,  passes  through  the  lungs,  both  on  its  entrance  and 
return ;  so  as  to  yield  to  their  capillaries  all  the  oxygen  which  they  can  take 
from  it,  and  of  which  the  blood  that  it  has  elsewhere  met  with  has  not  de- 
prived it.  It  is  only  in  the  lungs,  that  it  meets  with  purely  venous  blood ;  for 
they  alone  receive  the  branches  of  the  pulmonary  artery ;  the  vessels  which 
are  distributed  upon  the  respiratory  surface  of  the  air-sacs  and  bones,  being 
a  part  of  the  systematic  circulating  apparatus.  Hence  we  may  regard  this 
curious  provision,  as  being  partly  designed  for  the  aeration  of  the  blood  in  its 
course  through  the  system  (this,  it  will  be  remembered,  being  the  sole  mode 
in  which  the  function  is  performed  in  Insects),  and  partly  for  supplying  the 
lungs  with  air,  as  from  a  reservoir,  during  the  violent  actions  of  flight. 

38.  The  articulation  of  the  anterior  extremity  with  the  trunk  exhibits  a 
peculiar  provision  for  strength  and  power,  which  we  find  in  no  other  Verte- 
brata.  The  two  clavicles  are  united  together  on  the  central  line,  forming  the 
furcula  or  merry-thought ;  and  the  use  of  this  is  to  keep  the  shoulders  apart, 
notwithstanding  the  opposing  force  exerted  by  the  pectoral  muscles  in  the 
action  of  flight.  It  is  generally  firm,  and  its  angle  open,  in  proportion  to  the 
power  of  the  wings.  Besides  this  bone,  there  is  another  connecting  the 
sternum  with  the  scapula  on  each  side  ;  this  is  the  coracoid  bone,  which  in 
Man  and  most  other  Mammalia  is  scarcely  developed,  being  merely  a  short  pro- 
cess which  does  not  reach  the  sternum.  The  sternum  of  Birds  usually  ex- 
hibits a  very  remarkale  development  on  the  median  line  ;  an  elevated  keel  or 
ridge  being  seen  on  it,  which  serves  for  the  attachment  of  the  powerful  mus- 
cles that  depress  the  wings.  In  the  great  development  of  the  sternum,  Birds 
have  some  analogy  with  the  Turtle  tribe  :  which  they  also  resemble  in  the 
deficiency  of  teeth,  and  in  the  development  of  a  horny  covering  to  the  jaws: 
but  in  these,  the  lateral  elements  of  the  sternum  are  the  parts  most  developed; 
whilst  in  Birds  it  is  the  central  portion  which  exhibits  the  peculiarity.  From 
the  depth  of  the  keel  of  the  sternum,  a  judgment  may  be  formed  of  the  thick- 
ness of  the  pectoral  muscles,  and  thence  of  the  powers  of  flight ;  in  the  Os- 
trich tribe,  where  the  wings  are  not  sufficiently  developed  to  raise  the  bird 
off  the  ground,  the  sternum  is  quite  flat,  as  in  the  Mammalia.  The  want  of 
flexibility  in  the  trunk  is  counterbalanced  by  the  length  and  flexibility  of  the 
neck ;  the  number  of  cervical  vertebra?  is  very  considerable,  varying  from  12 
to  23, — the  highest  number  being  present  in  the  Swan  tribe.  They  are  so 
articulated  that  the  head  can  be  turned  completely  round,  or  moved  in  any 
direction.  The  anterior  extremities  of  Birds  being  solely  adapted  to  sustain 
them  in  flight,  the  posterior  are  necessarily  modified  for  their  support  on  the 
ground.  They  are  usually  placed  rather  far  back ;  but  the  spine  has  a  posi- 
tion more  inclined  than  horizontal,  so  that  the  weight  may  not  be  altogether 
thrown  forwards.  The  trunk  is  supported  on  the  thighs  by  powerful  muscles; 
and  there  is  another  series,  which  passes  from  the  lower  part  of  the  spine 


GENERAL  CHARACTERS  OF  BIRDS.  61 

continuously  to  the  toes,  turning  over  the  knee  and  heel,  in  such  a  manner 
that  the  flexion  of  these  joints  shall  tighten  the  tendons  ;  by  this  contrivance, 
the  simple  weight  of  the  body  flexes  the  toes ;  and  Birds  are  thus  enabled  to 
maintain  their  position,  by  grasping  their  perch,  during  sleep,  without  any 
active  muscular  effort. 

39.  Not  only  do  Birds  resemble    Insects  in  their  general  structure  and 
mode  of  life,  but  also  in  the  peculiar  development  of  the  instinctive  powers. 
Under  the  direction  of  these,  the  place  for  their  nests  appears  to  be  selected  ; 
their  materials  collected  ;  the  nest  themselves  built,  and  the  young  reared  in 
them  ;  the  migrations  are  performed  ;  and  many  curious  stratagems  are  em- 
ployed to  obtain  food.     It  is  sufficient  to  indicate  these  in  general  terms ; 
since  it  is  well  known  that  the  habits  of  Birds  have  peculiarities  restricted  to 
each  species  ;  and  that  in  all  the   individuals   of  each  species ;  they  are  as 
precisely  alike  as  their  circumstances  will  admit.    Nevertheless,  there  are  ob- 
served in  Birds  a  degree  and  kind  of  adaptation  to  varying  conditions,  which 
Insects  do  not  possess,  and  which  display  an  amount  of  intelligence  far  su- 
perior to  what  is  found  in  that  class  (§  17).    This  is  evinced  also  in  their  edu- 
cability ;   for   no  animal  can  be  taught  to  perform   actions   which  are   not 
natural  to  it,  unless  it  possesses  in  a  considerable  degree  the  powers  of  memory 
and  association,  at  least,  if  not  some  of  the  higher  mental  faculties,  such  as 
the  power  of  perceiving  and  comparing  the  relations  of  ideas.     Moreover, 
in  the  domesticability  of  many  tribes  of  Birds,  we  see  this  educability  com- 
bined with  a  degree  of  that  higher  form  of  attachment  to   Man,  which  is  so 
strikingly  exhibited  by  certain  species  of  Mammalia.     The   development  of 
the  senses  of  Birds  varies  in  different  tribes,  according  to  the  mode  in  which 
they  are  adapted  to  obtain  their  prey.     The  sight  is  almost  always  extremely 
acute,  and  is  their  chief  means  of  seeking  food  ;  and  where  this  would  be  of 
comparatively  little  service,  as  in  the  nocturnal  rapacious  birds,  it  is  compen- 
sated by  a  much  higher  development  of  the  faculty  of  hearing,  than  is  com- 
mon amongst  other  tribes.      The   senses   of  smell,  taste,  and   touch,  do  not 
seem  to  be  usually  very  acute  in  Birds  ;  but  there   are  particular  tribes,  in 
which  each  of  these  is  more  developed  than  in  the  rest. 

40.  As  might  be  expected  from  the  analogy  of  Birds  with  Insects,  the  de- 
velopment of  their  organs  of  nutrition  (excepting  that  of  the  respiratory  organs) 
is  much  less  striking  than  is  that  of  the  locomotive  apparatus.     The  whole 
cavity   of  the   trunk,  especially  in  Birds  distinguished  for  their  powers  of 
flight,  is  small  in  comparison  with  that  of  the  body ;  but  what  is  wanting  in 
the  size  of  the  organs,  is  made  up  in  their  energy  of  function.     Hence  the 
demand  for  food  is  more  active  in  them  than  in  any  other  class  of  animals. 
It  is  interesting  to  observe,  that  there  is  more  bi-lateral  symmetry  in  the 
arrangement  of  the  viscera,  than  we  usually  find  in  the  class  above.     This  is 
evidently  connected  with  their  active  locomotive  powers  ;  as  it  is  obviously 
necessary,  that  the  two  sides  of  the  body  should  be  balanced  with  perfect 
equality,  and  that  their  energy  should  be  exactly  correspondent.     The  lungs 
and  air-sacs  are  precisely  similar  in  size  and  situation  on  the  two  sides ;  con- 
sequently the  heart  is  placed  on  the  median  line  ;  and  the  mode  of  origin, 
from  the  aorta,  of  the  trunks  supplying  the  head  and  upper  extremities,  is 
alike  on  the  two  sides.     The  liver,  also,  is  less  asymmetrical  than  we  usually 
find  it  in  the  Mammalia. 

41.  It  has  been  remarked,  that  the  assistance  afforded  by  the  parent,  in 
the  development  of  the  young,  is  greater  in  Birds   than  in  the  lower  Verte- 
brata ;  but  is  less  than  in  Mammalia.    Whilst  Reptiles  and  Fishes  show  little 
or  no  concern  for  their  eggs  after  they  have  deposited  them,  Birds  sedulously 
tend  them,  affording  them  not  only  protection  but  warmth,  by  means  of  their 
powerful  heat-producing  apparatus.     The  yolk-bag  of  the   Bird's  egg  is  so 

6 


62  ON  THE  PLACE  OF  MAN  IN  THE  SCALE  OF  BEING. 

suspended  in  the  midst  of  the  white  albumen,  that,  when  the  egg  is  laid  upon 
its  side,  it  will  always  rise  to  the  highest  part  of  it;  and  the  relative  weight 
of  the  several  parts  is  further  adjusted  in  such  a  manner,  that  the  cicatricula 
or  germ-spot  shall  always  be  at  the  point  nearest  the  shell,  so  as  to  come  into 
the  closest  proximity  with  the  source  of  heat,  and  also  to  be  in  the  most  im- 
mediate relation  with  the  surrounding  air.  There  are  some  Birds,  inhabiting 
the  equatorial  region,  which  do  not  always  incubate  their  eggs,  trusting  to  the 
solar  heat  for  their  maturation.  It  is  said  that  the  Ostriches  of  the  intertro- 
pical  deserts  are  content  with  covering  their  eggs  with  a  thin  layer  of  sand, 
so  as  to  admit  the  action  of  the  sun  by  day,  and  to  keep  them  warm  at  night ; 
but  that  those  living  under  a  less  constantly  elevated  temperature,  sit  upon 
their  eggs — if  not  constantly,  at  any  rate  when  the  solar  heat  is  not  sufficient. 
This  statement  has  been  disputed ;  but  its  truth  seems  to  be  confirmed  by  a 
curious  observation  made  by  Mr.  Knight,  that  a  Fly-catcher,  which  built  for 
several  years  in  one  of  his  hot-houses,  sat  upon  its  eggs  when  the  temperature 
was  belo\v  72°,  but  left  them  when  it  rose  above  that  standard.  Certain  Birds 
inhabiting  New  Holland,  deposit  their  eggs  in  a  sort  of  hot-bed,  composed  of 
decaying  vegetable  matter ;  a  number  associating  together  for  the  construction 
of  this  artificial  incubating  apparatus,  although  they  live  separately  at  other 
times.  The  degree  of  assistance  afforded  by  the  parent  Birds  to  their  young, 
after  their  emersion  from  the  shell,  varies  much  in  different  tribes  ;  in  general 
it  may  be  remarked,  however,  that  it  is  most  prolonged  in  those  which  ulti- 
mately attain  the  highest  development,  and  especially  in  those  whose  intelli- 
gence becomes  the  greatest.  Thus  the  Chicken  and  the  D.uckling,  when  just 
hatched,  are  able  to  shift  for  themselves ;  but  among  the  Raptorial  and  Inses- 
sorial  Birds,  which  rank  far  higher  in  the  scale,  the  young  is  for  a  long  time  de- 
pendent upon  the  parent  for  food  ;  and  in  the  Parrot  tribe,  which  unquestion- 
ably surpasses  all  others  in  intelligence,  the  parent  not  only  supplies  its  young 
with  food  which  it  has  obtained  for  them,  but  partly  nourishes  them  by  a 
milky  secretion  from  the  interior  of  the  craw ;  impregnating  with  this  the 
aliment  which  it  swallows,  and  which  it  afterwards  disgorges  for  its  offspring. 

10.   General  characters  of  Mammalia. 

42.  The  MAMMALIA  are  universally  regarded  as  the  highest  group  in  the 
Animal  kingdom ;  not  only  from  being  that  to  which  Man  belongs  (so  far,  at 
least,  as  his  bodily  structure  is  concerned),  but  also  as  possessing  the  most 
complex  organization,  adapted  to  perform  the  greatest  number  and  variety  of 
actions,  and  to  execute  these  with  the  greatest  intelligence.     The  contrast  is 
here  extremely  strong  between  the   reasoning  and  the  instinctive  powers ; 
even  when  we  put  Man  out  of  view.     When  we  compare,  for  example,  the 
sagacity  of  a  Dog,  Monkey,  or  Elephant,  and  the  great  variety  of  circum- 
stances in  which  they  will  display  an  intelligent  adaptation  of  means  to  ends, 
with  the  limited  operations  of  Insects,  over  which  the  judgment  and  will  seem 
to  have  no  control,  we  cannot  help  being  struck  with  the  difference.     The 
former  are  educable  in  the   highest  degree  next  to  Man ;   the  latter  could  not 
be  made  to  change  their  habits,  in  any  essential  degree,  by  the  most  prolonged 
course  of  discipline.     Man  is  actuated,  like  the  lower  animals,  by  instinctive 
propensities,  which  have  an  immediate  bearing  on  his  corporeal  wants ;  whilst 
they  have,  like  him,  the  power  of  adapting  their  actions  to  gain  certain  ends, 
of  which  they  are  conscious.     A  Dog  or  an  Elephant  may  show  more  real 
wisdom,  in  controlling  for  a  time  its  instinctive  propensities,  from  the  desire 
to  accomplish   some  particular  object,  than  is  displayed  by  many  Men,  who 
give  free  scope  to  the  exercise  of  their  sensual  passions,  although  warned  by 
their  reason  of  the  injurious  consequences  of  such  indulgence. 


GENERAL  CHARACTERS  OF  MAMMALIA.  63 

43.  This  high  development  of  the  intelligence  in  Mammalia,  is  evidently 
connected  with  the  greatly-prolonged  connection  between  the  parent  and  the 
offspring,  which  we  find  to  be  a  characteristic  of  this  class.     Mammalia  are, 
like  Birds,  warm-blooded  Vertebrata,  possessing  a  complete  double   circula- 
tion ;  and  some  of  them  are  adapted  to  lead  the  life  of  Birds,  passing  a  large 
part  of  their  time  in  darting  through  the  air  on  wings,  in  pursuit  of  Insect 
prey.     But  they  differ  from  Birds  in  this  essential   particular,  that  they  are 
not  oviparous,  but  viviparous ;   producing  their  young   alive, — that  is,  in   a 
condition  in  which  they  can  perform  spontaneous  movements,  and  can  appro- 
priate nourishment  supplied  to  them  from  without.     But  they  are  not  distin- 
guished from  all   other  animals  by  this  character  alone ;  for  there  are  some 
species  among  Reptiles,  Fishes,  and  even  Insects,  which  produce  their  young 
alive, — the   egg  being  retained  within  the   oviduct  and  hatched  there.     The 
real  distinction  lies  partly  in  that,  which  the  name  of  the  class  imports, — the 
subsequent  nourishment  of  the   young  by  suckling ;   and  partly  in  the  mode 
in  which  the  embryo  is  nourished  before  its  birth.     In  Mammels,  the  yolk- 
bag  is  very  small  in  proportion  to  its  size  in  Birds ;  and  the  contents  of  the 
ovum,  instead  of  furnishing  (as  in  that  class)  the  materials  necessary  for  the 
development  of  the  young  animal,  up  to  the  time  when  it  can  ingest  food  for 
itself,  only  serve  for  the   earliest  set  of  changes  in  which  this  process  con- 
sists.    In  the  latter  stages  of  the  evolution  of  the  embryo,  it  is  supplied  with 
nutriment  directly  imbibed  from  its  parent.     This  is   at  first  accomplished 
by  means  of  a  series  of  root-like  tufts,  which  are  prolonged  from  the  surface 
of  the  ovum,  and  insinuate  themselves  among  the  maternal  vessels,  without, 
however,  uniting  with  them.     These   tufts  absorb,  from  the  maternal  fluid, 
the  ingredients  necessary  for  the  support  of  the  embryo ;   and  also  convey 
back  to  the  parent  its  effete  particles,  which  are  received  back  into  her  blood, 
and  are  then  cast  out  of  her  system,  by  the  process  of  secretion,  respiration, 
&c. 

44.  The  Mammalia  may  be  divided  into  two  sub-classes  ;  in  one  of  which 
the  structure  just  described  is  the  greatest  advance  ever  made,  in   the  appa- 
ratus by  which  the  foetus  is  nourished  ;  whilst  in  the  other  a  more  concen- 
trated form  is  subsequently  assumed  by  it.    The  ovuni  of  the  latter  is  delayed 
for  a  longer  period,  in  a  cavity  formed  by  the  union  of  the  two  oviducts, 
termed  the  uterus;  which  can  be  scarcely  said  to  be  developed  in  the  Marsu- 
pialia  and  Monotremata,  the  two  orders  constituting  the  first  sub-class.     The 
vascular  tufts  proceeding  from  the  chorion  become  especially  developed  at  one 
point,  and  the  vessels  of  the  uterus  are  extremely  enlarged  in  a  corresponding 
situation ;  the  tufts  dip  down,  as  it  were,  into  a  chamber  formed  by  an  exten- 
sion of  the  inner  lining  of  these  vessels,  and  serve  the  combined  purpose  of 
the  roots  of  plants  and  of  the  branchiae  of  aquatic  animals, — absorbing  from 
the  maternal  blood  the  materials  required  for  the  nourishment  of  the  embryo, 
and  aerating  the  blood  of  the  foetus,  by  exposing  it  to  the  influence  of  that  of 
the  parent.     The  peculiar  organ  thus  formed  is  termed  the  placenta;  and  the 
two  sub-classes  of  the  Mammalia  have   thence  received  the  appellations  of 
placental  and  non-placental.     The  animals  belonging  to  the  latter  present 
many  points  of  affinity  to  Birds,  in  the  structure  of  their  internal  organs. 
That  of  the  brain  is  very  nearly  allied  in  these  two  groups ;  and  their  amount 
of  intelligence  seems,  as  far  as  can  be  determined,  to  bear  a  close  correspond- 
ence.    The  Ornithorhyncus  in  particular,  has  so  many  marks  of  alliance  to 
oviparous  animals,  and  its  osteology,  as  well  as  in  its  horny  bill  and  in  less 
important  particulars,  that  Naturalists   have  much  debated  whether  it  could 
really  be  termed  a  Mammiferous  animal.     No  positive  evidence  has  yet  been 
obtained  that  its  young  are  born  alive ;  but  on  the  other  hand,  there  is  a  strong 
reason  to  believe  that  they  come  into  the  world  uninclosed  in  the  ovum,  al- 


64  ON  THE  PLACE  OF  MAN  IN  THE  SCALE  OF  BEING. 

though  in  a  very  imperfect  condition.  Moreover,  it  has  been  satisfactorily 
ascertained  that  the  young  are  nourished,  for  some  time  after  their  birth,  by 
a  mammary  secretion,  which  the  organization  of  their  mouth  at  that  period 
enables  them  to  obtain  from  the  parent.  In  the  Marsupialia,  there  is  a 
remarkable  compensation  for  the  abrupt  termination  of  the  period  of  uterine 
gestation, — the  young  being  received  into  a  pouch  or  marsupium,  within  which 
the  nipple  is  situated  ;  this  is  extremely  prolonged,  and  the  mouth  of  the  foetus 
(for  so  the  being  must  still  be  regarded)  is  adapted  to  receive  and  hold  on  by 
it;  so  that  the  little  creature,  which  looks  at  first  more  like  an  earth-worm 
than  a  Mammiferous  animal,  is  thus  suspended  within  the  protective  pouch, 
until  its  development  is  so  far  advanced,  that  it  can  shift  for  itself  in  the  same 
degree  as  other  new-born  animals  can  do. 

45.  The  period  of  gestation  in  the  higher  sub-class  of  Mammalia,  is  usually 
prolonged,  until  the  foetus  is  able,  on  its   entrance  into  the  world,  to  execute 
regular  movements ;   some  of  these  being  merely  indicative  of  its  desire  for 
food,  and  others  evidently  designed  for  the  acquirement  of  it.    In  many  species, 
the  young  animal  seems  to  be  from  the  first  in  the  full  possession  of  its  senses, 
and  has  considerable  power  of  active  locomotion ;  in  general,  however,  it  is 
very  dependent  upon  its  parent ;  only  being  able  to  obtain  food  when  this  is 
placed  within  its  immediate  grasp.     Such  is  the  case  with  the  Human  infant, 
which  is  closely  dependent  upon  its  parent,  during  a  larger  proportion  of  its 
existence,  than  is  the  young  of  any  other  animal.     Here  again,  therefore,  we 
perceive  the   application  of  the  general  law,  that,  the  higher  the   grade  of 
development  a  being  is  ultimately  to  assume,  the  more  does  it  require  to  be 
assisted  during  the  early  stages  of  its  progress.     In  the  case  of  Man,  the  pro- 
longation of  this  period  has  a  most  important  and  evident  influence  upon  the 
social  condition  of  the  race;  being,  in  fact,  one  of  the  chief  means,  by  which 
the  solitary  are  bound  together  in  families. 

46.  The  class  Mammalia,  taken  as  a  whole,  is  not  characterized  so  much 
by  the  possession  of  any  one  particular  faculty, — like  that  which  has  been 
seen  in  Birds, — as  by  the  perfect  combination  of  the  different  powers,  which 
renders  the  animals  belonging  to  it  susceptible  of  a  much  greater  variety  of 
actions,  than  any  others  can  perform.     There  are  none  that  can  compete  with 
Birds  in  acuteness  of  sight ;  but  there  are  few  that  do  not  possess  the  senses 
of  smell,  taste,  and  touch  in  a  more  elevated  degree.     There  are  none  which 
can  rival  Birds  in  rapidity  of  locomotion  ;  but  there  are  few  which  cannot  per- 
form several  kinds  of  progression.     Several  of  their  movements  require   a 
considerable  amount  of  flexibility  in  the  spine ;  hence  the  vertebral  column, 
and  the  bony  framework  of  the  trunk,  are  never  so  much  consolidated  as  they 
are  in  Birds.     On  the  other  hand,  the  neck  is  much  less  movable ;  it  never 
consists  of  more  than  seven  vertebrae,  and  these  are  always  present ;  so  that 
they  are  sometimes  of  great  length,  as  in  the  Giraffe,  and  sometimes   ex- 
tremely short,  as  in  the  Whale,  which  seems  to  have  no  neck  at  all.     In  the 
greatest  number  of  Mammalia,  the  body  is  supported  upon  all  the  four  extre- 
mities, as  in  Reptiles  ;  being  adapted  for  progression  along  the  surface  of  the 
earth.     There  are  some  species,  however,  in  which  the  typical  structure  has 
undergone  a  metamorphosis,  by  which  it  is  made  to  resemble  that  of  a  Bird ; 
whilst  in  others  it  is  modified,  so  as  to  conform  to  the  character  of  the  Fish. 
In  the  Bats,  the  power  of  motion  is  almost  entirely  delegated  to  the  wings, 
which  are  composed  of  skin,  stretched  over  a  bony  framework  formed  of  the 
widely-extended  hand ;  and  the  sternum  has  a  projecting  keel  for  the  attach- 
ment of  the  pectoral  muscles,  as  in  Birds.    And  in  the  Whale  tribe,  the  power 
of  locomotion  is   almost  completely  taken  from  the  extremities,  and  given 
back  to  the  trunk,  as  in  Fishes  ;  for  the  posterior  extremities  are  entirely  ab- 
sent, and  the  anterior  serve  only  for  guidance :  there  is  this  important  differ- 


CHIEF  SUB-DIVISIONS  OF  MAMMALIA.  65 

ence,  however,  that  the  tail,  which  is  flattened  vertically  in  Fishes,  is  flattened 
horizontally  in  the  Cetacea,  which  require  the  power  of  frequently  coming  to 
the  surface  to  breathe. 

47.  The  inferior  energy  of  muscular  movement  in  the  Mammalia,  is  ac- 
companied by  an  inferior  amount  of  respiration ;  the  type  of  the  respiratory 
apparatus,  however,  is  higher  than  in  Birds,  a  large  extent  of  surface  being 
comprised  within  a  smaller  space.     The  lungs  are  confined  to  the  cavity  of 
the  thorax ;  and  there  is  a  provision  for  the  regular  renewal  of  the  air  received 
into  them,  by  the  action  of  the  diaphragm,  which  here  completely  separates 
that  cavity  from  the  abdomen.     The  diminished  amount  of  respiration,  again, 
involves  the  production  of  a  lower  degree  of  animal  heat ;  so  that  the  tempe- 
rature of  this  class  seldom  rises  above  104°.     There  is,  therefore,  less  need 
of  means  for  effectually  confining  the  caloric, — especially,  too,  as  their  greater 
average  size  causes  their  radiating  surface  to  be  much  less,  in  proportion  to 
their  bulk,  than   is  that  of  Birds ;  and  accordingly,  we  find  them  provided 
only  with  a  covering  of  hair  or  fur,  which  is  much  less  warm  than  that  of 
feathers,  and  which  is  thin  and  scanty  in  Mammals  inhabiting  tropical  climates. 
The  chief  exception  to  the  last  rule  is  in  the  case  of  the  Sloths  and  of  some 
Monkeys,  which  inhabit  situations  exposed  to  the  most  powerful  rays  of  the 
sun,  and  which  are  covered  with  a  long  but  thin  and  coarse  hair ;  the  purpose 
of  this  is  evidently  the  protection  of  their  skin  from  the  external  heat.     The 
inferior  energy  of  the  respiration  and  circulation,  involves  a  diminished  activity 
of  the  other  functions  of  nutrition,  as  compared  with  those  of  Birds ;  and  the 
demand  for  food  appears  to  be  somewhat  less  constant.  Their  various  organs, 
however,  are  developed  upon  a  higher  plan ;  as  we  have  already  observed  in 
regard  to  those  of  respiration. 

11.  Chief  Sub-divisions  of  Mammalia. 

48.  In  sub-dividing  the  truly  Viviparous  division  of  the  class,  so  as  to  sepa- 
rate Man  from  the  tribes  with  which  he  is  associated  in  it,  we  may  be  advan- 
tageously guided,  in  the  first  place,  by  the  conformation  of  the  extremities ; 
since  upon  the  perfection  of  the  organs  of  touch,  will  depend  much  of  the 
address  of  an  animal  in  executing  the  actions  to  which  it  is  prompted  by  its 
intelligence.     The  degree  of  this  perfection  is  estimated  by  the  number  and 
mobility  of  the  fingers,  and  by  the  degree  in  which  their  extremities  are  en- 
veloped by  the  nail,  claw,  or  hoof,  that  terminates  them.     When  the  fingers 
are  partly  absent,  or  are  consolidated  together,  and  a  hoof  envelopes  all  that 
portion  which  touches  the  ground,  it  is  obvious  that  the  sensibility  must  be 
blunted,  whilst,  at  the  same  time,  the  member  becomes  incapacitated  for  pre- 
hension.    The  opposite  extreme  is  where  (as  in  Man)  a  thin  nail  covers  only 
one  side  of  the  extremity  of  the  finger,  leaving  the  other  possessed  of  all  its 
delicacy ; — where  several  such  fingers  exist,  of  which  one  can  be  opposed  to 
the  rest,  so  as  to  render  prehension  more  perfect,  and  to  perform  a  great  va- 
riety of  actions  : — and  where  the  plane  of  the  whole  hand  can  be  turned  in 
any  position,  by  the  nature  of  its  attachment  to  the  fore-arm.     Between  these 
there  are  many  intermediate  gradations.     By  these  characters,  the  viviparous 
Mammalia  may  be  divided  into  the  Unguiculated,  which  have  separate  fin- 
gers, terminated  by  distinct  nails  or  claws  ;  and  the  Ungulated,  in  which  the 
fingers  are  more  or  less  consolidated,  and  inclosed  at  their  extremity  in  a  hard 
hoof.     Hoofed  animals  are  necessarily  Herbivorous,  inasmuch  as  the  con- 
formation of  their  feet  precludes  the  possibility  of  their  seizing  a  living  prey; 
and  they  have   flat-crowned  grinding  teeth   for  triturating  their  food, 
summits  of  these  teeth  are  usually  not  covered  by  a  smooth  coat  of  enamel, 
but  present  a  series  of  elevations*  and  depressions ;  these  are  occasioned  by 

6* 


66  ON  THE  PLACE  OF  MAN  IN  THE  SCALE  OF  BEING. 

the  peculiar  structure  of  the  teeth,  which  consist  of  alternating  plates  of  ena- 
mel, ivory  or  dentine,  and  cementum  or  crusta  petrosa, — substances  of  three 
different  degrees  of  hardness  ;  and,  as  the  softer  portions  will  of  course  wear 
down  first,  the  harder  remain  as  projecting  ridges.  In  order  to  give  effect  to 
these,  there  is  usually  a  considerable  power  of  lateral  motion  possessed  by 
the  lower  jaw  ;  so  that  a  regular  grinding  action  may  be  performed,  which  is 
favourable  to  the  complete  reduction  of  the  tough  vegetable  substances  that 
serve  as  their  food. 

49.  Animals  with  Unguiculated  fingers  are  capable  of  more  variety  in  the  cha- 
racter of  their  food.  In  some  it  is  almost  exclusively  vegetable,  as  in  the  Roden- 
tia ;  and  here  the  power  of  prehension  possessed  by  the  extremities  is  small, 
the  fore-arm  not  being  so  constructed  as  to  be  capable  of  the  motions  of  pro- 
nation  and  supination.     In  this  order,  the  mouth  is  remarkably  adapted  for 
grinding  down  hard  vegetable  substances  ;  the  molar  teeth  being  furnished  with 
transverse  ridges  of  enamel;  and  the  jaws  having  a  powerful  movement  back- 
wards and  forwards.*  In  other  orders,  again,  there  is  an  almost  exclusive  adap- 
tation to  animal  food.     The  toes  are  furnished  with  long  and  sharp  claws  ; 
and  the  fore-feet  may  be  placed  in  a  variety  of  positions,  by  the  rotation  of 
the  two  bones  composing  the  lower  part  of  the  leg.     The  grinding  teeth  are 
very  narrow,  and  are  formed  with  sharp  points  and  edges,  so  as  to  be  adapted 
for  dividing  animal  flesh  ;  these  are  firmly  set  in  short  strong  jaws,  which  are 
fitted  together  like  the  blades  of  a  pair  of  scissors,  having  no  action  but  a 
vertical  one  ;  and  the  constant  friction  of  the  edges  of  the  molar  teeth  against 
each  other,  keeps  them  sharp.!     In  the  Carnivorous  group,  too,  we  find  the 
greatest  development  of  the  canine  teeth,  which  are  commonly  absent  or  but 
slightly  developed  among  herbivorous  quadrupeds ;  these  are  instruments  of 
great  power,  serving  both  for  the  first  attack  of  their  prey,  and  for  subse- 
quently tearing  it  in  pieces.   It  is  evident  that  the  whole  structure  of  the  body 
must  undergo  modification,  in  conformity  with  the  nature  of  the  food.     The 
simple  stomach  and  intestinal  canal  of  the  Carnivorous  animal,  adapted  only 
to  the  digestion  of  aliment  consisting  of  materials  similar  to  those  of  its  own 
body,  would  be  totally  useless  to  an  animal  prevented  by  its  general  organi- 
zation from  obtaining  any  other  than  vegetable  food ;  and,  on  the  other  hand, 
the  teeth  and  hoofs  of  the  Herbivorous   quadruped  would  be  of  little  assist- 
ance to  an  animal,  whose  instincts  and  general  conformation  adapted  it  for  the 
pursuit  of  animal  prey.     It  will  be  presently  seen  that,  in  regard  to  his  or- 
ganization, Man  holds  an  intermediate  place  between  the  purely  Herbivorous 
and  the  purely  Carnivorous  tribes ;  being  capable  of  subsisting  exclusively 
upon  either  kind  of  diet,  but  being  obviously  intended  by  Nature  to  employ 
both  in  combination. 

50.  The  classification  of  the  Mammalia  by  Linnaeus,  although  not  strictly 
natural,  affords  us  the  readiest  means  of  separating  Man,  zoologically,  from  all 
other  animals.     He  arranged  under  his  order  Primates,  all  the  unguiculated 
Mammalia  which  have  four  incisor  teeth  and  two  canines  in  each  jaw;  and 
thus  Man,  with  the  Monkeys  and  the  Bats,  was  distinguished  from  the  re- 

*  The  action  of  trituration  is  chiefly  performed  by  the  external  pteregoid  muscles.  When 
these  are  in  operation  together,  they  draw  the  whole  of  the  lower  jaw  forwards,  so  as  to 
make  the  lower  teeth  project  beyond  the  upper;  and  the  jaw  being  drawn  back  again  by 
the  digastric  muscles,  a  rapid  alternate  movement  may  be  thus  effected,  such  as  is  seen  in  the 
Rodentia.  When  only  the  muscle  of  one  side  acts,  the  condyle  of  that  side  is  thrown  for- 
wards ;  and  by  the  alternating  operation  of  the  two,  aided  by  other  muscles,  that  rotatory 
motion  is  given  which  we  see  especially  in  Ruminating  Quadrupeds. 

f  In  Carnivorous  animals,  the  muscles  which  elevate  the  lower  jaw  attain  a  very  high 
degree  of  development.  This  is  very  remarkably  seen  in  the  internal  pteregoid,  which  in 
Man  is  of  subordinate  size  and  importance,  but  which  is  a  very  powerful  muscle  in  the  Lion, 
Tiger,  &c. 


CHARACTERISTICS  OF  MAN.  67 

mainder  of  those  Quadrupeds  which  have  separate  fingers  with  distinct  nails 
or  claws.  This  group  is  now  sub-divided  into  three  orders,  corresponding 
with  the  Linnaean  genera,  Homo,  Simla,  and  Vespertilio.  The  last  of  these 
orders,  named  Cheiroptera,  consists  of  the  Bat  tribe,  which  is  easily  separated 
from  all  others  by  the  peculiar  conformation  of  the  anterior  extremities,  from 
which  its  name  is  derived.  The  second,  termed  Quadrumana,  comprehends 
the  Apes,  Monkeys,  and  Baboons,  which  exhibit  a  regular  series ;  the  highest 
approaching  Man  in  general  conformation ;  and  the  lowest  having  much  more 
of  the  general  organization  of  the  inferior  carnivorous  quadrupeds.  They  are 
distinguished  from  other  viviparous  Mammalia,  by  possessing  an  opposable 
thumb  on  all  four  extremities  (whence  they  are  termed  four-handed), — a  cha- 
racter which  is  only  found  elsewhere  in  the  Opossums.  Although  some  of 
the  higher  members  of  this  group  are  capable  of  maintaining  the  erect  posi- 
tion without  difficulty  for  some  time,  even  whilst  walking,  it  is  certainly  not 
that  which  is  natural  to  them.  The  posterior  extremity, — being  formed  on 
the  plan  of  a  hand,  for  prehension  rather  than  for  direct  support, — is  destitute 
of  the  heel,  which  is  characteristic  of  Man ;  and  although  Apes  can  climb 
trees  with  facility,  they  cannot  plant  the  foot  firmly  on  the  ground,  so  as  to 
resist  attempts  to  overthrow  them;  since  the  foot  rests  rather  upon  the  outer 
side  than  upon  its  sole,  and  the  narrowness  of  the  pelvis  is  unfavourable  to  an 
equilibrium.  There  are  many  points  of  striking  resemblance  to  Man,  how- 
ever, in  the  details  of  the  conformation  of  the  Quadrumana,  especially  among 
the  most  elevated  species ;  the  order  being  distinguished  by  the  same  charac- 
ters from  most  others.  The  structure  of  their  alimentary  canal  differs  ex- 
tremely little  from  his.  The  eyes  are  directed  forwards,  when  the  trunk  is 
erect;  and  the  orbit  is  completely  separated  from  the  temporal  fossae,  by  a 
bony  partition.  The  mammaa  are  situated  on  the  thorax  ;  and  the  penis  is 
pendent.  The  coitus,  however,  is  reverse,  as  in  the  lower  Mammalia.  The 
form  of  the  brain  in  the  higher  species  corresponds  with  that  of  Man  in  this 
remarkable  character, — that  it  is  divided  into  three  lobes,  of  which  the  poste- 
rior is  prolonged  backwards  so  as  to  cover  the  cerebellum  ;  this  is  not  the  case 
in  the  highest  of  the  other  Mammalia. 

12.   Characteristics  of  Man. 

51.  We  shall  now  review,  somewhat  in  detail,  the  distinctive  characters 
that  separate  Man  from  those  animals  which  present  the  nearest  approach  to 
him  in  general  structure  and  aspect.  These  may  be  advantageously  classified 
according  to  their  obvious  purposes ;  and  the  first  series  we  shall  notice  con- 
sists of  those  by  which  Man  is  peculiarly  adapted  to  the  erect  attitude.  On 
examining  his  cranium  we  remark  that  the  condyles,  by  which  it  is  articulated 
with  the  spinal  column,  are  so  placed  that  a  perpendicular  dropped  from  the 
centre  of  gravity  of  the  head  would  nearly  fall  between  them,  so  as  to  be 
within  the  base  on  which  it  rests.  The  foramen  magnum  is  not  placed  in  the 
centre  of  the  base  of  the  skull,  but  just  behind  it;  in  order  to  compensate  for 
the  greater  specific  gravity  of  the  posterior  part  of  the  head,  which  is  entirely 
filled  with  solid  matter,  whilst  the  anterior  part  contains  many  cavities.  There 
is,  indeed,  a  little  over-compensation,  which  gives  a  slight  preponderance  to 
the  front  of  the  head;  so  that  it  drops  forwards  and  downwards  when  all  the 
muscles  are  relaxed.  But  the  muscles  which  are  attached  to  the  back  of  the 
head  are  far  larger  and  more  numerous  than  those  in  front  of  the  condyles ; 
so  that  they  are  evidently  intended  to  counteract  this  disposition;  and  we 
find,  accordingly,  that  we  can  keep  up  the  head  for  the  whole  day,  with  so 
slight  and  involuntary  an  effort  that  no  fatigue  is  produced  by  it.  Moreover, 
the  surfaces  of  the  condyles  have  a  horizontal  direction  when  the  head  is 


68  ON  THE  PLACE  OF  MAN  IN  THE  SCALE  OF  BEING. 

upright ;  and  thus  the  weight  of  the  skull  is  laid  vertically  by  them  upon  the 
top  of  the  vertebral  column.  If  these  arrangements  be  compared  with  the 
position  and  direction  of  the  occipital  condyles  in  other  Mammalia,  it  will 
be  found  that  these  are  placed  in  the  latter  much  nearer  to  the  back  of  the 
head,  and  that  their  plane  is  more  oblique.  Thus,  whilst  the  foramen  mag- 
num is  situated,  in  Man,  just  behind  the  centre  of  the  base  of  the  skull,  it  is 
found  in  the  Chimpanzee  and  Orang  Outan  to  occupy  the  middle  of  the 
posterior  third  ;  and,  as  we  descend  through  the  scale  of  Mammalia,  we  ob- 
serve that  it  gradually  approaches  the  back  of  the  skull,  and  at  last  comes 
nearly  into  the  line  of  its  longest  diameter,  as  we  see  in  the  Horse.  The 
obliquity  of  the  condyles  differs  in  a  similar  degree.  In  all  Mammalia  except 
Man  their  plane  is  oblique ;  so  that,  even  if  the  head  were  equally  balanced 
upon  them,  the  force  of  gravity  would  tend  to  carry  it  forwards  and  down- 
wards. In  Man,  the  angle  which  they  make  with  the  horizontal  is  very 
small ;  in  the  Orang  Outan  it  is  as  much  as  37°;  and  in  the  Horse  their 
plane  is  vertical,  making  the  angle  90°.  If,  therefore,  the  natural  posture  of 
Man  were  horizontal,  he  would  in  this  respect  be  circumstanced  like  the 
Horse ;  for  the  plane  of  his  condyles,  which  is  nearly  horizontal  in  the  erect 
position,  would  then  be  vertical:  and  the  head,  instead  of  being  nearly 
balanced  in  the  erect  position,  would  hang  at  the  end  of  the  neck,  so  that  its 
whole  weight  would  have  to  be  supported  by  some  external  and  constantly- 
acting  power.  But  for  this  there  is  neither  in  the  skeleton,  nor  in  the  muscu- 
lar system  of  Man,  any  adequate  provision.  In,  other  Mammalia  the  head  is 
maintained  in  such  a  position  by  a  strong  and  thick  ligament  (the  ligamentum 
nuchas),  which  passes  from  the  spines  of  the  cervical  and  dorsal  vertebra?  to 
the  most  prominent  part  of  the  occiput ;  but  of  this  there  is  scarcely  any 

Fig.  5. 


View  of  the  base  of  skull  of  Man,  compared  with  that  of  the  Orang  Outan. 

trace  in  Man.     In  the  horizontal  position,  therefore,  he  would  have  the  heavi- 
est head,  with  the  least  power  of  supporting  it. 

52.  The  position  of  the  face  immediately  beneath  the  brain,  so  that  its 
front  is  nearly  in  the  same  plane  as  the  forehead,  is  peculiarly  characteristic 
of  Man;  for  the  crania  of  the  Chimpanzee  and  Orang,  which  approach 
nearest  to  that  of  Man,  are  entirely  posterior  to,  and  not  above,  the  face.  It 
should  be  remarked  that  in  the  young  Ape  there  is  a  much  greater  resem- 
blance to  Man  in  this  respect  than  there  is  in  the  adult.  For  at  the  time  of 
the  second  dentition  the  muzzle  of  the  Ape  undergoes  a  great  elongation,  so 


CHARACTERISTICS  OF  MAN.  69 

that  it  projects  much  more  beyond  the  forehead ;  this  is  seen  in  Fig.  5.  The 
whole  cast  of  the  features  is  altered  at  the  same  time,  so  that  it  approaches 
much  more  to  that  of  the  lower  Quadrumana  than  would  be  supposed  from 
observation  of  the  young  animal  only.*  This  increased  projection  of  the 
muzzle  is  an  evidence  of  want  of  perfect  adaptation  to  the  erect  posture : 
whilst  the  absence  of  it  in  Man  shows  that  no  other  position  is  natural  to  him. 
Supposing  that,  with  a  head  formed  as  at  present,  he  were  to  move  on  all 
fours,  so  that  his^face  would  be  brought  into  a  plane  parallel  with  the  ground, 
— as  painful  an  effort  would  be  required  to  examine  with  the  eyes  an  object 
placed  in  front  of  the  body,  as  is  now  necessary  to  keep  the  eyes  fixed  on 
the  zenith ;  the  nose  would  be  unable  to  perceive  any  other  odours  than  those 
which  proceeded  from  the  earth  or  from  the  body  itself;  and  the  mouth  could 
not  touch  the  ground  without  bringing  the  forehead  and  chin  also  into  contact 
with  it.  The  oblique  position  of  the  condyles  in  the  Quadrumana  enables 
them,  without  much  difficulty,  to  adapt  the  inclination  of  their  heads  to  the 
horizontal  or  to  the  erect  position  of  the  body;  but  the  natural  position,  in 
the  highest  among  them,  is  unquestionably  one  in  which  the  spinal  column  is 
inclined,  tfre  body  being  partially  thrown  forwards,  so  as  to  rest  upon  the 
anterior  extremities ;  and  in  this  position  the  face  is  directed  forwards  without 
any  effort,  owing  to  the  mode  in  which  the  head  is.  articulated  with  the  spine. 
53.  The  vertebral  column  in  Man,  though  not  absolutely  straight,  has  its 
curves  so  arranged,  that,  when  the  body  is  in  an  erect  posture,  a  vertical  line 
from  its  summit  would  fall  exactly  on  the  centre  of  its  base.  It  increases 
considerably  in  size  in  the  lumbar  region,  so  as  to  be  altogether  somewhat 
pyramidal  in  form.  The  lumbar  portion,  in  the  Chimpanzee  and  Orang,  is 
not  of  the  same  proportional  strength;  and  contains  but  four  vertebrae  instead 
of  five.  The  processes  for  the  attachment  of  the  muscles  of  the  back  to  this 
part,  are  peculiarly  large  and  strong  in  Man ;  and  this  arrangement  is  obviously 
adapted  to  overcome  the  tendency,  which  the  weight  of  the  viscera  in  front 
of  the  column  would  have,  to  draw  it  forwards  and  downwards.  On  the 
other  hand,  the  spinous  processes  of  the  cervical  and  dorsal  vertebrae,  which x 
are  in  other  Mammalia  large  and  strong,  for  the  attachment  of  the  ligamentum 
nuchae  to  support  the  head,  have  in  Man  but  little  prominence,  his  head  being 
nearly  balanced  on  the  top  of  the  column.  The  base  of  the  human  vertebral 
column  is  placed  on  a  sacrum  of  greater  proportional  breadth,  than  that  of 
any  other  animal;  this  sacrum  is  fixed  between  two  widely  expanded  ilia; 
and  the  whole  pelvis  is  thus  peculiarly  broad.  In  this  manner,  the  femoral 
articulations  are  thrown  very  far  apart,  so  as  to  give  a  wide  basis  of  support; 
and  by  the  oblique  direction  of  the  whole  pelvis,  the  weight  of  the  body  is 
transmitted  almost  vertically,  from  the  top  of  the  sacrum  to  the  upper  part  of 
the  thigh  bones.  The  pelvis  of  every  other  species  of  the  class  is  very  dif- 
ferently constructed  ;  as  will  be  seen  in  the  adjoining  Figure  (6),  in  which  the 
skeleton  of  the  Orang  is  placed  in  proximity  with  that  of  Man.  It  is  much 
longer  and  narrower,  having  a  far  smaller  space  between  the  iliac  bones  and 
the  lowest  ribs ;  the  sacrum  is  lengthened  and  reduced  in  width ;  the  alae  of 
the  ilia  are  much  less  expanded ;  and  the  whole  pelvis  is  brought  nearly  into 
a  line  with  the  vertebral  column.  The  position  of  the  human  femur,  in  which 
it  is  most  securely  fixed  in  its  deep  aoetabulum,  is  that  which  it  has  when 
supporting  the  body  in  the  erect  attitude.  In  the  Chimpanzee  and  Orang,  its 
analogous  position  is  at  an  oblique  angle  to  the  long  axis  of  the  pelvis,  with 
the  body  supported  obliquely  in  front  of  it;  in  many  Mammalia,  as  in  the 

*  None  but  young  specimens  of  the  Chimpanzee  and  Orang  Outan  have  ever  been 
brought  alive  to  this  country ;  and  they  have  never  survived  the  period  of  their  second 
dentition. 


70  ON  THE  PLACE  OF  MAN  IN  THE  SCALE  OF  BEING. 

Elephant,  it  forms  nearly  a  right  angle ;  and  in  several  others,  as  the  Horse, 
Ox,  &c.,  it  forms  an  acute  angle  with  the  axis  of  the  pelvis  and  spinal  column. 

54.  The  lower  extremities  of  Man  are  remarkable  for  their  length ;  which 
is  proportionally  greater  than  that  which  we  find  in  any  other  Mammalia, 
except  the  Kangaroo  tribe.     It  is  evident  that  there  could  be  no  greater  ob- 
stacle to  his  prorgession  in  the  horizontal  posture,  than  this  length  of  what 
would  then  be  his  hind  legs.     Either  Man  would  be  obliged  to  rest  on  his 
knees,  with  his  thighs  so  bent  towards  the  trunk,  that  the  attempt  to  advance 
them  would  be  inconvenient,  his  legs  and  feet  being  entirely  useless ;  or  he 
must  elevate  his  trunk  upon  the  extremities  of  his  toes,  throwing  his  head 
downwards,  and  exerting  himself  violently  at  every  attempt  to  bring  forward 
the  thighs  by  a  rotatory  motion  at  the  hip-joint.     In  either  case,  the  only  use- 
ful joint  would  be  that  at  the  hip;  and  the  legs  would  be  scarcely  superior  to 
wooden  or  other  rigid  supports.     The  chief  difference  in  their  proportional 
length,  between  Man  and  the  semi-erect  Apes,  is  seen  in  the  thigh ;  and  from 
the  comparative  shortness  of  his  arms,  his  hands  only  reach  the  middle  of  the 
thighs ;  whilst  in  the  Chimpanzee  they  hang  on  a  level  with  the  knees,  and 
in  the  Orang  they  descend  to  the  ancles.     The  human  femur  is  distinguished 
by  its  form  and  position  as  well  as  by  its  length.     The  obliquity  and  length 
of  its  neck  still  further  increase  the  breadth  of  the  hips ;  whilst  they  cause 
the  lower  extremities  of  these  bones  to  be  somewhat  obliquely  directed  towards 
each  other,  so  that  the  knees  are  brought  more  into  ike  line  of  the  axis  of  the 
body.     This  position  is  obviously  of  great  use  in  walking,  when  the  whole 
weight  has  to  be  alternately  supported  on  each  limb ;  for  if  the  knees  had 
been  further  apart,  the  whole  body  must  have  been  swung  from  side  to  side 
at  each  step,  so  as  to  bring  the  centre  of  gravity  over  the  top  of  each  tibia ; 
and,  as  a  matter  of  fact,  it  is  noticed  that  the  walk  of  women,  in  whom  the 
pelvis  is  broader  and  the  knees  more  separated,  is  less  steady  than  that  of 
men. 

55.  There  is  a  very  marked  contrast  between  the  knee-joint  of  Man,  and 
that  even  of  the  highest  Apes.     In  the  former,  the  opposed  extremities  of  the 
femur  and  the  tibia  are  expanded,  so  as  to  present  a  very  broad  articulating 
surface;  and  the  internal  condyle  of  the  femur  is  lengthened,  so  that  the  two 
are  in  the  same  horizontal  plane,  in  the  usual  oblique  position  of  the  femur. 
In  this  manner,  the  whole  weight  of  the  body,  in  its  erect  posture,  falls  verti- 
cally on  the  top  of  the  tibia,  when  the  joint  is  in  the  firmest  position  in  which 
it  can  be  placed:  and  a  comparison  of  the  knee-joint  of  the  Orang  with  that 
of  Man,  will  make  it  at  once  evident,  that  the  former  is  not  intended  to  serve 
as  more  than  a  partial  support.     The  weight  of  the  body  is  transmitted  through 
the  tibia,  to  the  upper  convex  surface  of  the  astragalus,  and  thence  to  the  other 
bones  of  the  foot.     The  Human  foot  is,  in  proportion  to  the  size  of  the  whole 
body,  larger,  broader,  and  stronger,  than  that  of  any  other  Mammal  save  the 
Kangaroo.     The  sole  of  the  foot  is  concave,  so  that  the  weight  of  the  body 
falls  on  the  summit  of  an  arch,  of  which  the  os  calcis  and  the  metatarsal  bones 
form  the  two  points  of  support.     This  arched  form  of  the  foot,  and  the  na- 
tural contact  of  the  os  calcis  with  the  ground,  are  peculiar  to  Man  alone.     All 
the  Apes  have  the  os  calcis  small,  straight,  and  more  or  less  raised  from  the 
ground;   which  they  touch  when  starrtling  erect,  with  the  outer  side  only  of  the 
foot :  whilst  in  animals  more  remote  from  Man,  the  os  calcis  is  brought  still 
more  into  the  line  of  the  tibia ;  and  the  foot  being  more  elongated  and  nar- 
rowed, only  the   extremities  of  the  toes  come  in  contact  with  the  ground. 
Hence  Man  is  the  only  species  of  Mammal,  which  can  stand  upon  one  leg. — 
If  we  look  at  the  structure  of  the  upper  extremity  of  Man,  we  observe  simi- 
lar proofs  that  it  is  not  intended  as  an  organ  of  support;  being  destitute  of  all 
these  adaptations ;  and  having  a  conformation  obviously  designed  for  other 


CHARACTERISTICS   OF  MAN. 


71 


Fig.  6. 


Comparative  view  of  the  Skeleton  of  Man  and  that  of  the  Orang  Outan. 


72  ON  THE  PLACE  OF  MAN  IN  THE  SCALE  OF  BEING. 

purposes,  which  could  not  be  possibly  answered,  if  it  were  not  completely 
relieved  from  the  necessity  of  bearing  the  weight  of  the  body.  This  peculiar 
conformation  will  be  subsequently  considered. 

56.  The  other  parts  of  the  Human  body  concerned  in  locomotion  are 
exactly  adapted  to  the  peculiar  construction  of  the  skeleton.  The  tibia  is 
kept  erect  upon  the  foot  by  the  very  powerful  muscles  which  are  attached  to 
the  heel  and  form  the  calf  of  the  leg, — a  prominence  observed  in  no  other 
animal  in  nearly  the  same  degree.  The  flexor  longus  pollicis  pedis,  which  is 
attached  in  the  Chimpanzee  and  Orang  to  the  three  middle  toes,  proceeds  in' 
man  exclusively  to  the  great  toe,  on  which  the  weight  of  the  body  is  often 
supported.  The  extensors  of  the  leg  upon  the  thigh  are  much  more  power- 
ful than  the  flexors,  an  arrangement  seen  in  no  other  animal.  The  glutaBi,  by 
which  the  pelvis  is  kept  erect  upon  the  thigh,  are  of  far  greater  size  than  is 
elsewhere  seen.  The  superior  power  of  the  muscles  tending  to  draw  the 
head  and  spine  backwards,  has  been  already  referred  to.  In  the  general  form 
of  the  trunk,  there  is  a  considerable  difference  between  Man  and  most  other 
Mammalia.  His  chest  is  large,  but  is  flattened  in  front,  and  expanded  late- 
rally, so  that  its  transverse  diameter  is  greater  than  its  antero-posterior  ; — a 
peculiarity  in  which  only  the  most  Man-like  monkeys  partake.  His  sternum 
is  short  and  broad  ;  and  there  is  a  considerable  distance  between  the  lower 
ribs  and  the  ilia,  in  consequence  of  the  small  number  of  ribs,  and  the  length 
of  the  lumbar  portion  of  the  vertebral  column.  The  viscera  in  this  space, 
which  in  the  horizontal  position  would  be  but  insufficiently  held  up  by  the 
abdominal  muscles,  are,  in  the  erect  attitude,  securely  supported  by  the  ex- 
panded pelvis. — From  all  these  facts,  it  is  an  indisputable  conclusion,  that  the 
erect  attitude  and  biped  progression  are  natural  to  Man  ;  and  we  must  regard 
as  in  great  degree  fabulous,  all  those  histories  of  supposed  wild  men,  who,  it 
has  been  said,  were  found  in  woods,  dumb,  hairy,  and  crawling  on  all-fours. 
The  most  elaborate  investigation*  of  the  structure  of  the  anthropoid  Apes, 
and  the  fullest  acquaintance  with  their  habits,  concur  in  proving,  that  their 
movements  are  not  easy  or  agile,  unless  they  employ  all  their  limbs  for  the 
support  of  their  bodies. 

57.  The  name  Bimana  is  the  most  appropriate  that  could  be  found,  for  an 
order  constituted  by  the  Human  species  only  ;  since  Man  alone  is  two-handed. 
"  That,"  says  Cuvier,  "  which  constitutes  the  hand,  properly  so  called,  is  the 
faculty  of  opposing  the  thumb  to  the  other  fingers,  so  as  to  seize  the  most 
minute  objects, — a  faculty  which  is  carried  to  its  highest  degree  of  perfec- 
tion in  Man,  in  whom  the  whole  anterior  extremity  is  free,  and  can  be  em- 
ployed in  prehension."  Some  naturalists  refuse  the  term  hand  to  the  extremi- 
ties of  the  monkey  tribe,  preferring  to  call  them  graspers  ;  for  it  is  certainly 
true,  that,  although  usually  possessing  an  opposable  thumb,  they  are  destitute 
of  the  power  of  performing  many  of  those  actions  which  we  regard  as  most 
characteristic  of  the  hand.  Such  actions  are  chiefly  dependent  on  the  size 
and  power  of  the  thumb  ;  which  is  much  more  developed  in  Man  than  it  is 
even  in  the  highest  Apes.  The  thumb  of  the  Human  hand  can  be  brought 
into  exact  opposition  to  the  extremities  of  all  the  fingers,  whether  singly  or 
in  combination ;  whilst  in  those  Quadrumana  which  most  nearly  approach 
Man,  the  thumb  is  so  short  and  weak,  and  the  fingers  so  long  and  slender, 
that  their  tips  can  scarcely  be  brought  into  opposition,  and  can  never  be  op- 
posed in  near  contact  with  each  other,  with  any  degree  of  force.  Hence, 
although  admirably  adapted  for  clinging  round  bodies  of  a  certain  size,  such 
as  the  small  branches  of  trees,  &c.,  the  extremities  of  the  Quadrumana  can 

*  See  especially  Mr.  Owen's  paper  on  the  Chimpanzee  and  the  Orang  Outan  in  the  Zoolo- 
gical Transactions,  vol.  i. 


CHARACTERISTICS  OF  MAN.  73 

neither  seize  very  minute  objects  with  such  precision,  nor  support  large  ones 
with  such  firmness,  as  are  essential  to  the  dexterous  performance  of  a  variety 
of  operations  for  which  the  hand  of  Man  is  admirably  adapted.  Hence 
the  possession  of  "  four  hands"  is  not,  as  might  be  supposed,  a  character 
which  raises  the  animals  that  exhibit  it  above  two-handed  Man ;  for  none  of 
these  four  hands  are  adapted  to  the  same  variety  of  actions  of  prehension  of 
which  his  are  capable  ;  and  all  of  them  are  in  some  degree  required  for  sup- 
port. In  this  respect  their  character  approaches  much  nearer  to  that  of  the 
extremities  of  the  lower  Mammalia  ;  and  there  are  several  among  them  in 
which,  the  opposable  power  of  the.  thumb  being  deficient,  there  is  no  very 
marked  distinction  between  the  so-called  hand,  and  the  foot  of  some  Carni- 
vora.  There  is  much  truth,  then,  in  Sir  C.  Bell's  remark,  that  "  We  ought 
to  define  the  hand  as  belonging  exclusively  to  Man."  There  is  in  him,  what 
we  observe  in  none  of  the  Mammalia  that  approach  him  in  other  respects, 
a  complete  distinction  in  the  functional  character  of  the  anterior  and  posterior 
extremities ;  the  former  being  adapted  for  prehension  alone,  and  the  latter  for 
support  alone.  Thus  each  function  is  performed  with  a  much  higher  degree 
of  perfection  than  it  can  be  where  two  such  opposite  purposes  have  to  be 
united.  The  arm  of  the  Ape  has  as  wide  a  range  of  motion  as  in  Man,  so 
far  as  its  articulations  are  concerned ;  but  it  is  only  when  the  animal  is  in  the 
erect  attitude,  that  its  arm  can  have  free  play.  Thus  the  structure  of  the 
whole  frame  must  conform  to  that  of  the  hand,  and  must  act  with  reference 
to  it.  But  it  cannot  be  said  with  truth  (as  some  have  maintained)  that  Man 
owes  his  superiority  to  his  hand  alone  ;  for  without  the  directing  mind,  the 
hand  would  be  comparatively  valueless.  His  elevated  position  is  due  to  his 
mind  and  its  instruments  conjointly ;  for  if  destitute  of  either,  mankind  would 
be  speedily  extinguished  altogether,  or  reduced  to  a  very  subordinate  grade  of 
existence. 

58.  Thus,  then,  although  the  order  Bimana  cannot  be  separated  from  the 
order  Quadrumana  by  any  single  obvious  structural  distinction,  like  that  which 
characterises  the  Cetacea  or  the  Cheiroptera,  it  is  really  as  far  removed  by 
the  minuter,  but  not  less  important,  modifications  which  have  been  detailed. 
A  few  other  distinctive  characters  will  now  be  noticed.  With  one  exception 
(the  fossil  genus  Anoplotherium,  which  is  allied  to  the  Tapir  tribe),  Man  is 
distinguished  from  all  other  animals,  by  the  equality  in  the  length  of  all  his 
teeth,  and  by  the  equally  close  approximation  of  them  all  in  each  jaw.  Even 
the  anthropoid'Apes  have  the  canine  teeth  longer  than  the  others,  and  an  in- 
terval in  the  line  of  teeth  in  each  side  of  the  jaw,  to  receive  the  canine  teeth 
of  the  opposite  jaw.  This  is  more  evident  in  the  adult  than  in  the  young 
animal.  The  vertical  position  of  the  Human  teeth,  on  which  one  of  the  most 
characteristic  features  of  the  Human  face — the  prominent  chin — depends,  is 
also  quite  peculiar ;  and  is  intimately  connected  both  with  his  erect  attitude, 
and  with  the  perfection  of  the  hands,  by  which  the  food  is  divided  and  con- 
veyed to  the  mouth.  He  has  no  occasion  for  that  protrusion  of  the  muzzle 
and  lips,  which,  in  animals  that  seize  their  food  with  the  mouth  only,  is  re- 
quired to  prevent  the  face  from  coming  into  general  contact  with  it. — The 
absence  of  any  weapons  of  offence,  and  of  direct  means  of  defence,  are 
remarkable  characteristics  of  Man,  and  distinguish  him  from  other  animals. 
On  those  to  whom  Nature  has  denied  weapons  of  attack,  she  has  bestowed 
the  means  either  of  passive  defence,  of  concealment,  or  of  flight.  Yet  Man, 
by  his  superior  reason,  has  not  only  been  enabled  to  resist  the  attacks  of  other 
animals,  but  even  to  bring  them  under  subjection  to  himself.  His  intellect 
can  scarcely  suggest  the  mechanism,  which  his  hands  cannot  frame ;  and  he 
has  devised  and  constructed  arms  more  powerful  than  those  which  any  other 
creature  wields,  and  defences  so  secure  as  to  defy  the  assaults  of  all  but  his 
7 


74  ON  THE  PLACE  OF  MAN  IN  THE  SCALE  OF  BEING. 

fellow-men. — We  find,  on  comparing  the  brain  of  Man  with  that  of  the  lower 
Mammalia,  that,  as  might  have  been  anticipated,  its  proportional  dimensions 
are  much  greater,  and  its  structure  more  complex.  The  former  part  of  this 
statement  is  easily  verified  by  an  examination  of  the  cranium  alone,  comparing 
the  size  of  its  cavity  with  that  of  the  face.  The  amount  of  the  facial  angle, 
taken  after  the  manner  of  Camper,  affords  a  tolerably  correct  indication  of  the 
relative  sizes  of  these  parts.  In  Man,  the  facial  angle  is,  in  the  average  of 
Europeans,  80°;  in  Negroes,  it  is  about  70°.  In  the  adult  Chimpanzee  (which 
approaches  in  this  respect  nearest  to  Man),  the  facial  angle  is  only  35° ;  and 
in  the  Orang,  it  is  no  more  than  30°.  In  other  animals  it  is  still  less,  except 
when  it  is  increased  by  the  prominence  of  large  frontal  sinuses,  or  by  the 
comparative  shortness  of  the  jaws.  In  regard  to  the  structure  of  the  brain,  we 
shall  here  only  remark  generally,  that  the  Encephalon  of  Man  far  exceeds  that 
of  the  highest  Quadrumana,  in  the  size  of  the  cerebral  hemispheres,  in  the 
complexity  and  development  of  its  internal  parts,  and  in  the  depth  and  num- 
ber of  its  convolutions^. 

59.  Man  cannot  be  regarded  as  distinguished  from  other  Mammalia,  how- 
ever, either  by  acuteness  of  sensibility,  or  by  muscular  power.     His  swiftness 
in  running,  and  agility  in  leaping,  are  inferior  to  that  of  other  animals  of  his 
size, — the   full-grown  Orang  for  example.     The  smallness  of  his  face,  com- 
pared with  that  of  the  cranium,  shows  that  the  portion  of  the  nervous  system 
distributed  to  the  organs  of  sense,  is  less  developed  in  him  than  it  is  in  most 
other  animals ;  and  the  small  proportional  size  of  the  ganglionic  centres,  with 
which  these  organs  are  immediately  connected,  is   another  indication  of  the 
same  fact.     Accordingly,  he  is  surpassed  by  many  in  acuteness  of  sensibility 
to  light,  sound,  &c. ;   but  he   stands  pre-eminent  in  the  power  of  comparing 
sensations,  and  of  drawing  conclusions  from  them.    Moreover,  although  none 
of  his  senses  are  very  acute  in  his   natural  state,  they  are  all  moderately  so, 
which  is  not  the  case  in  other  animals  ;  and  they  are  capable  (as  is  ajso  his 
swiftness  of  foot)  of  being  much  improved  by  practice,  especially  when  cir- 
cumstances strongly  call  for  their  exercise.     This  power  of  adaptation  to  va- 
rieties in  external  conditions,  which  makes  him  to  a  great  extent  independent 
of  them,  is  manifested  in  other  features  of  his   structure  and  economy.     He 
is  capable  of  sustaining  the  lowest,  as  well  as  the  highest,  extremes  of  tempe- 
rature and  of  atmospheric  pressure.     In  the  former  of  these  particulars,  he  is 
strikingly  contrasted  with  the  anthropoid  Apes,  such  as  the  Chimpanzee,  which 
is  restricted  to  a  few  of  the  hottest  parts  of  Africa,  and  the  Orang-Outan, 
which  is  only  found  in  Borneo  and  Sumatra :  these  cannot  be  kept  alive  in 
temperate  climates,  without  the  assistance  of  artificial  heat ;   and  even  when 
this  is  afforded,  they  speedily  become  diseased  and  die.    His  diet  is  naturally 
of  a  mixed  kind  ;  but  he  can  support  himself  in  health  and  strength,  on  either 
animal  or  vegetable   food  exclusively.     It  is  by  the  demands  which  his  pecu- 
liar condition  makes  upon  the  exercise  of  his  ingenuity,  that  his  mental 
powers  are  first  called  into   active  operation;  but,  when  once  aroused,  their 
development  has  no   assignable   limit.     The  slow  growth  of  Man,  and  the 
length  of  time  during  which  he  remains  in  a  state  of  dependence  upon  his 
parents,  have  been  already  mentioned  as  peculiarities,  by  which  he  is  distin- 
guished from  all  other  animals.     He  is  unable  to  seek  his  own  food,  during 
at  least  the  three  first  years   of  his  life  ;  and  he   does  not  attain  to  his  full 
stature,  until  he  is  more  than  twenty  years  of  age.     In  proportion  to  his  size, 
too,  the  whole  sum  of  his  life  is  greater  than  that  of  other  Mammalia.     The 
greatest  age  of  the  Horse,  for  example,  which  is  an  animal  of  much  superior 
bulk,  is  between  thirty  and  forty  years.    That  of  the  Orang,  which,  when  full 
grown,  surpasses  Man  in  stature,  is  about  the  same,  so  far  as  it  can  be  ascer- 
tained.    The  age  to  which  the  life  of  Man  is   frequently  prolonged,  is  well 


GENERAL  CONSIDERATIONS.  75 

known  to  be  above  a  hundred  years ;  and  instances  of  such  longevity  are  to  be 
found  in  all  nations. 

60.  Still,  however  widely  Man  may  be  distinguished  from  other  animals, 
by  these  and  other  peculiarities  of  his  structure  and  economy,  he  is  yet  more 
distinguished  by  those  mental  endowments,  and    the  habitudes  of  life  and 
action  thence  resulting,  which  must  be  regarded  as  the  essential  characteris- 
tics of  humanity.     In  the  highest  among  brutes,  the  mere  instinctive  propen- 
sities (as  already  defined,  §§  17,  23),  are  the  frequent  springs  of  action;  and 
although  the   intelligent  will  is  called  into   exercise  to  a  certain  extent,  the 
character  never  rises  beyond  that  of  the  child.     In  fact,  the  correspondence 
between  the  psychical  endowments  of  the  Chimpanzee,  and  those  of  the 
Human  infant  before  it  begins  to  speak,  is  very  close.     In  Man,  however,  the 
instinctive  propensities  only  manifest  themselves  strongly,  whilst  the  intellect 
is  undeveloped ;  and  nearly  all  the  actions  of  adult  life  are  performed  under 
the  direction  of  the  intelligent  will.     From  the  intelligence  of  Man  results  his 
mental  improvability ;  and  his  improved  condition  impresses  itself  upon  his 
organization.     This  capability  of  improvement  in  the  bodily  as  well  as  the 
mental  constitution  of  Man,  is   the  cause  of  the.  comforts  now  enjoyed  by 
civilised  races,  and  of  the  means  which  they  possess  of  still  further  elevation. 
In  the  processes  by  which  these  are  attained,  we  observe  a  remarkable  differ- 
ence between  the  character  of  Man,  and  that  of  other  animals.     The  arts  of 
which  these  last  are  capable,  are  limited,  and  peculiar  to  each  species  ;  and 
there  seems  to  be  no  general  power  of  adapting  these  to  any  great  variety  of 
purposes,  or  of  profiting  by  the  experience  of  others.     Where   a  particular 
adaptation  of  means  to  ends,  of  actions  to  circumstances,  is  made  by  an  indi- 
vidual (as  is  frequently  the  case,  when  some  amount  of  intelligence  or  ration- 
ality exists),  the  rest  do  not  seem  to  profit  by  it;  so  that  there  is  no  proof 
that  any  species  or  race  among  the  lower  animals  ever  makes  a  voluntary 
advance  towards  an  improvement  or  alteration  in  its  condition.     That  modifi- 
cations in  structure  and  instincts  may  be  induced  by  circumstances,  in  some 
of  the  most  improvable  species,  such   as  the  Dog,  has  been  shown  by  abun- 
dant evidence ;  and  these  modifications,  if  connected  with  the  original  habits 
and  instincts  of  the  species,  maybe  hereditarily  transmitted.     There  is  ample 
proof  that  the  same  is  the  case,  in  regard  both  to  the  corporeal  structure  and 
the  psychical  endowments  of  Man.     Under  the  influence  of  education,  phy- 
sical and  mental,  continued  through  successive  generations,  the  capabilities  of 
his  whole  nature,  and  especially  those  of  his  brain,  are  called  out;  so  that  the 
general  character  of  the  race  is  greatly  improved.     On  the  other  hand,  under 
the  influence  of  a  degraded  condition,  there  is  an  equally  certain  retrogression; 
so  that,  to  bring  up  the  New  Holland  Savage,  or  the  African  Bushman,  to  the 
level  of  the  European,  would  probably  require  centuries  of  civilisation.     One 
of  the  most  important  aids  to  the  use  and  development  of  the  human  mind,  is 
the  power  of  producing  articulate  sounds,  or  language ;  of  which,  as  far  as 
we  know,  Man  is  the  only  animal  in  possession.     There  is  no  doubt,  that 
many  other  species  have  certain  powers  of  communication  between  individu- 
als ;  but  these  are  probably  very  limited,  and  of  a  kind  very  different  from  a 
verbal  language. 

61.  Although,  as  we  have  stated,  there  is  nothing  in  Man's  present  condi- 
tion, which  removes  him  from  the  pale  of  the  Animal  kingdom,  and  although 
his  reasoning  powers  differ  rather  in  degree  than  in  kind  from  those  of  the 
inferior  animals,  he  seems  distinguished  by  one  innate  tendency ;  to  which 
we  have  no  reason  to  suppose  that  anything  analogous  elsewhere  exists  ;  and 
which  we  might  term  an  instinct,  were  it  not  that  this  designation  is  generally 
applied  to   propensities  of  a  much   lower    character.     The   tendency  here 
referred  to,  is  that  which  seems  universal  in  Man,  to  believe  in  some  unseen 


76  MUTUAL  RELATIONS  OF  THE  HUMAN  FAMILY. 

Existence.  This  may  take  various  forms,  but  is  never  .entirely  absent  from 
any  race  or  nation,  although  (like  other  innate  tendencies)  it  may  be  defective 
in  individuals.  Attempts  have  been  made  by  some  travellers  to  prove,  that 
particular  nations  are  destitute  of  it ;  but  such  assertions  have  been  based 
only  upon  a  limited  acquaintance  with  their  habits  of  thought,  and  with  their 
outward  observances.  For  there  are  probably  none,  that  do  not  possess  the 
idea  of  some  invisible  Power  external  to  themselves  ;  whose  favour  they  seek, 
and  whose  anger  they  deprecate,  by  sacrifice  and  other  religious  observances. 
It  requires  a  higher  mental  cultivation  than  is  always  to  be  met  with,  to  con- 
ceive of  this  Power  as  having  a  Spiritual  existence;  but  wherever  the  idea 
of  spirituality  can  be  defined,  it  seems  connected  with  it.  The  vulgar  readi- 
ness to  believe  in  demons,  ghosts,  &c.,  is  only  an  irregular  or  depraved 
manifestation  of  the  same  tendency.  Closely  connected  with  it,  is  the  desire 
to  share  in  this  spiritual  existence  ;  which  has  been  implanted  by  the  Creator 
in  the  mind  of  Man  ;  and  which,  developed  as  it  is  by  the  mental  cultivation 
that  is  almost  necessary  for  the  formation  of  the  idea,  has  been  regarded  by 
philosophers  in  all  ages,  as  one  of  the  chief  natural  arguments  for  the  im- 
mortality of  the  soul.  By  this  Immortal  Soul,  the  existence  of  which  is  thus 
guessed  by  Man,  but  of  whose  presence  within  him  he  derives  the  strongest 
assurance  from  Revelation,  Man  is  connected  with  beings  of  a  higher  order, 
amongst  whom  Intelligence  exists,  unrestrained  in  its  exercise  by  the  imper- 
fections of  that  corporeal  mechanism,  through  which  it  here  operates ;  and  to 
this  state, — a  state  of  more  intimate  communion  of  mind  with  mind,  and  of 
creatures  with  their  Creator, — he  is  encouraged  to  aspire,  as  the  reward  of 
his  improvement  of  the  talents  here  committed  to  his  charge. 


CHAPTER    II. 

OF  THE  MUTUAL  RELATIONS  OF  THE  DIFFERENT  BRANCHES  OF  THE  HUMAN 

FAMILY. 

1.   General  Considerations. 

62.  AMONGST  the  various  tribes  of  Men,  which  people  the  surface  of  the 
globe,  and  which  are  separated  from  all  other  animals  by  the  foregoing  cha- 
racters, there  are  differences  of  a  very  striking  and  important  nature.     They 
are   distinguishable  from  each  other,  not  merely  by  their  language,  dress, 
manners  and  customs,  religious  belief,  and  other  acquired  peculiarities,  but  in 
the  physical  conformation  of  their  bodies ;  and  the  difference  lies,  not  merely 
in  the  colour  of  the  skin,  the  nature  of  the   hair,  the  form   of  the  soft  parts 
(such  as  the  nose,  lips,  &c.,)  but  in  the  shape  of  the  skull,  and  of  other  parts 
of  the  bony  skeleton,  which  might  be  supposed  to  be  less  liable  to  variation. 
It  is  a  question  of  great  scientific  interest,  as  well  as  one  that  considerably 
affects  the  mode  in  which  we  treat  the  races  that  differ  from  our  own, — whe- 
ther they  are  all  of  one  species,  that  is,  descended  from   the   same  or  from 
similar  parentage, — or  whether  they  are  to  be  regarded  as  distinct  species, 
the  first  parents  of  the  several  races  having  had  the  same  differences  among 
themselves,  as  those  now  exhibited  by  their  descendants. 

63.  It  has  been  a  favourite  idea,  among  those  who  wished  to   excuse   the 
horrors  of  slavery,  or  the  extirpation  of  savage   tribes,  that  the  races  thus 


ON  THE  DISCRIMINATION  OF  SPECIES.  77 

treated  might  be  considered  as  inferior  species,  incapable  of  being  raised  by 
any  treatment  to  our  own  elevation;  and  as  thus  falling  legitimately  under  the 
domination  of  the  superior  races,  just  as  the  lower  animals  have  been  placed 
by  the  Creator  in  subservience  to  Man.  This  doctrine,  which  has  had  its 
origin  in  the  desire  to  justify  as  expedient  what  could  not  be  defended  as 
morally  right,  finds  no  support  from  scientific  inquiries  conducted  in  an  en- 
larged spirit.  In  order  to  arrive  at  a  just  conclusion  on  the  subject,  it  is  ne- 
cessary to  take  a  very  extensive  survey  of  the  evidence  furnished  by  a  number 
of  different  lines  of  inquiry.  Thus,  in  the  first  place,  it  is  right  to  investigate 
what  are  the  discriminating  structural  marks,  by  which  species  are  distin- 
guished among  the  lower  tribes  of  animals. — Secondly,  it  should  be  ascer- 
tained to  what  extent  variation  may  proceed  among  races,  which  are  histori- 
cally known  to  have  a  common  parentage  ;  and  what  are  the  circumstances 
which  most  favour  such  variations. — Thirdly,  the  .extreme  variations,  which 
present  themselves  among  the  different  races  of  men,  should  be  compared 
with  those  which  occur  among  tribes  of  animals  known  to  be  of  the  same 
parentage;  and  it  should  be  questioned,  at  the  same  time,  whether  the  cir- 
cumstances which  favour  the  production  of  varieties  in  the  latter  case,  are  in 
operation  in  the  former. — Fourthly,  where  it  is  impossible  to  trace  back  dis- 
tinct races  to  their  origin,  it  is. to  be  inquired  how  far  agreement  in  physiolo- 
gical and  psychological  peculiarities  may  be  regarded  as  indicating  specific 
identity,  even  where  a  considerable  difference  exists  in  bodily  conformation ; 
and  this  test,  if  it  can  be  determined  on,  has  to  be  applied  to  Man.  Fifthly, 
it  must  be  attempted,  by  a  detailed  examination  of  the  varieties  of  the  human 
race  themselves,  to  ascertain  whether  their  differences  in  conformation  are 
constant;  or  whether  there  are  not  occasional  manifestations,  in  each  race,  of 
a  tendency  to  assume  the  characters  of  others ;  so  as  to  prevent  a  definite  line 
being  drawn  between  the  several  tribes,  which  together  make  up  the  (sup- 
posed) distinct  species.* 

2.  On  the  Discrimination  of  Species. 

64.  Theirs/  of  the  foregoing  questions  is  a  fertile  source  of  perplexity  to 
the  Naturalist ;  owing  to  the  tendency  that  exists  in  certain  races  of  Plants 
and  Animals,  to  exhibit  variations  of  form  much  greater  than  those  which 
are  relied  upon  in  other  instances  as   characterizing  distinct  species.     In  our 
ignorance  as  to  the  history  of  the  origin  of  the  greater  part  of  the  dissimilar 
forms  or  races  of  organized   beings,  with  which  the  globe  is  peopled,  we  are 
accustomed  to  regard  two  races  of  Plants  or  animals  as  of  the  same  species, — 
that  is,  as  Having  had  the   same  or  similar  progenitors, — when  they  are  not 
distinguished  from  one  another  by  any  peculiarities,  but  such  as  the  one  may 
be  supposed  to  have  gained,  or  the  other  to  have   lost,  by  the  influence  of 
external  circumstances  during  a  long  period  of  time.     On  the  other  hand,  two 
races  are  regarded  as  constituting  distinct  species,'— that  is,  are  believed  to 
have  descended  from  dissimilar  parents, — when  a  constant  well-marked  dif- 
ference exists  between  them,  such  as  exhibits  no  tendency  to  variation  in  the 
individuals  of  either  race  fleeing  equally  characteristic  of  every  one),  and  is 
not  affected  by  the  lapse  of  time  or  by  change  in  external  conditions. 

65.  Thus,  if  we  compare  together  the  different  breeds   of  Dogs,  we  find 

*  This  investigation  has  been  most  elaborately,  and  in  the  Author's  opinion  most  suc- 
cessfully, worked  out  by  Dr.  Prichard,  in  his  profound  and  philosophical  Treatise  on  the 
Physical  History  of  Man.  The  sketch  of  the  argument  given  above  does  little  more  than 
exhibit  the  conclusions  at  which  he  has  arrived ;  and  for  the  grounds  on  which  these  are 
based,  reference  .must  be  made  to  that  work,  or  to  the  abridgment  of  it  published  by  Dr. 
Prichard,  under  the  title  of  the  Natural  History  of  Man. 

7* 


78  MUTUAL  RELATIONS  OF  THE  HUMAN  FAMILY. 

that,  although  they  are  distinguished  by  very  marked  peculiarities,  yet  that 
these  peculiarities  are  by  no  means  constant.  There  is  historical  evidence  of 
the  great  change,  which  may  take  place  in  their  conformation  and  habits, 
under  the  influence  of  a  change  in  their  external  circumstances  ;  in  the  case, 
for  example,  of  the  blood-hounds,  introduced  into  the  West  Indies  by  the 
Spaniards,  which  have  now  degenerated  into  a  wild  race  of  very  different 
form,  and  have  lost  all  the  distinctive  characters  of  the  breed.  And  there  is 
not  that  close  agreement  in  the  distinctive  characters  of  the  several  breeds, 
among  the  individuals  respectively  composing  them,  which  is  requisite  for  the 
establishment  of  a  definite  specific  distinction ;  the  characters  being  shaded 
off,  as  it  were  in  individuals,  so  as  to  cause  a  near  approximation  between  the 
less  decided  forms  of  the  different  races. — On  the  other  hand,  in  spite  of  the 
varieties  of  conformation  exhibited  by  the  several  races  of  Dog,  (which  even 
affect  the  number  of  vertebrae  in  the  tail,  as  well  as  the  shape  and  proportions 
of  the  bones,  we  never  see  any  which  present  so  strong  a  resemblance  to  the 
Fox,  as  to  be  at  all  in  danger  of  being  mistaken  for  that  animal ;  and  they 
may  always  be  distinguished  by  this  obvious  character, — that  the  pupil  of  the 
eye  of  the  Dog  is  always  round,  whilst  that  of  the  Fox  is  oval  when  con- 
tracted. This  difference  may  appear  a  very  trifling  one,  in  comparison  with 
the  important  variations  presented  in  the  structure  of  the  different  breeds  of 
Dogs  ;  but  it  is  constant ;  and  it  may  therefore  be  assumed  to  have  existed 
in  the  progenitors  of  each  race,  as  it  exists  at  present  in  all  their  descendants. 

66.  There  are  many  instances  of  an  opposite  character,  in  which  the  tend- 
ency to  variation  is  extremely  small ;  and  in  which  the  Naturalist  feels  jus- 
tified in  assuming  a  specific  difference,  from  variations  in    size  or  colour, 
which  in  themselves  are  very  trifling,  but  which  are  important  in  classifica- 
tion, because  they  are  constant.     Thus,  among  the  several  species  of  the 
genus  Felis  (or  Cat  tribe),  there  is  scarcely  any  perceptible  osteological  varia- 
tion, except  in  point  of  size ;  so  that  even  Cuvier  was  unable  to  find  out  a 
positive  means  of  distinguishing  the  skull  of  the  Lion  from  that  of  the  Tiger; 
and  the  skeleton  of  a  Wild  Cat  is  a  reduced  copy  of  that  of  the  largest  Felines. 
There  are  certain  species,  which  are  distinguished  by  no  other  external  indi- 
cations, than  the  markings  upon  their  skins ; — characters,  which  are  in  other 
cases  subject  to  extreme  uncertainty;  but  which  are  here  so  constant,  as  to 
present  scarcely  the  slightest  variation  amongst  the  individuals  of  each  race. 
Thus,  if  a  certain  patch  or  stripe  be  repeated  from  generation  to  generation,  in 
a  wild  feline  race,  the  Naturalist  is  inclined  to  regard  this  as  a  sufficient  proof 
of  the  specific  difference  of  that  race  from  another  which  is  differently  marked. 
The  Domestic  Cat  is  the  only  one  of  the  group,  which  is  liable  to  any  con- 
siderable variation ;  and  in  this  species,  as  every  one  knows,  the  markings 
characteristic  of  the  several  breeds  or  races  are  not  thus  constantly  repeated, 
and  therefore  cannot  be  indicative  of  original  difference.     Now  it  is  precisely 
in  this  species  that  we  should  look  for  such  variations ;  since  it  is  the  only 
one  which  can  be  domesticated;  and  the  capability  of  domestication  implies 
a  power  in  the  original  constitution  of  the  animal,  to  adapt  itself  to  a  change 
of  circumstances,  and  thus  to  exhibit  various  departures  from  its  original  type. 

67.  This  striking  contrast,  between  variable  and  invariable  groups  of  ani- 
mals nearly  allied  to  each  other,  is  found  through  the  whole  kingdom  ;  every 
division  of  it  appearing  to  contain  some  species,  which  do  not  change  their 
forms  or  other  characteristics  under  any  circumstances,  but  which  cease  to 
exist  if  a  change  takes  place  in  their  conditions,  incompatible  with  the  regular 
performance  of  their  functions ;  whilst  it  also  includes  others,  in  whose  phy- 
sical and  psychical  constitutions  there  is  such  a  susceptibility  of  modification, 
that  new  forms  and  new  instincts  may  arise,  adapted  to  a  great  variety  of 
external  conditions,  and  thus  new  and  very  different  races  may  be  originated. 


EXTENT  OF  VARIATION  IN  RACES  OF  THE  SAME  SPECIES.  79 

Thus,  the  Feline  races,  with  a  few  exceptions,  are  fitted  to  maintain  life  only 
in  tropical  climates,  and  very  speedily  die  in  colder  countries  (unless  kept 
warm  by  artificial  means),  in  consequence  of  their  deficiency  of  heat-pro- 
ducing power,  and  the  want  of  a  close  downy  fur  adapted  to  retain  the  caloric 
generated  in  their  bodies.  On  the  other  hand,  the  Dog  is  enabled  to  accom- 
pany Man,  in  the  coldest  as  well  as  the  hottest  regions  of  the  globe ;  his 
power  of  generating  heat  being  capable  of  variation,  in  accordance  with  the 
external  temperature ;  and  his  entire  organization  undergoing  modifications, 
which  adapt  it  to  the  change  in  the  conditions  of  its  existence.  It  appears, 
then,  that  it  is  quite  impossible  to  fix  upon  any  difference  of  structural  pecu- 
liarities, as  indications  of  the  distinctness  of  species ;  until  it  has  been  ascer- 
tained by  observation,  whether  they  are  constant  and  invariable, — the  races 
neither  exhibiting  any  tendency  to  change  in  successive  generations, — nor 
showing  any  disposition  to  mutual  approximation,  by  the  occasional  modifi- 
cation of  the  distinctive  characters  in  the  individuals  composing  them. 

3.  On  the  possible  Extent  of  Variation  within  the  Limits  of  Species. 

68.  We  now  come  to  the  second  point  of  our  inquiry, — namely,  the 
amount  of  variation  which  may  take  place  in  races,  historically  known  to 
have  had  a  common  parentage.  There  is  considerable  difficulty  in  obtaining 
the  most  complete  evidence  upon  this  subject;  owing  to  the  want  of  accurate 
observation  in  the  more  remote  historical  periods,  when  it  is  probable  that 
most  of  the  varieties  or  breeds  of  our  domesticated  animals  were  first  origi- 
nated. Still  there  is  an  adequate  amount  of  proof,  that  these  races  may 
undergo  very  considerable  modifications,  in  the  course  of  a  few  generations  ; 
and  that  new  races  or  breeds,  distinguished  by  marked  peculiarities,  may 
originate  even  at  the  present  time.  Our  most  satisfactory  information  is  de- 
rived from  the  changes,  which  have  taken  place  in  the  races  of  domesticated 
animals,  introduced  into  the  West  Indies  and  South  America,  by  the  Span- 
iards, three  centuries  since.  Many  of  these  races  have  multiplied  exceed- 
ingly, on  a  soil  and  under  a  climate  congenial  to  their  nature ;  and  several  of 
them  have  run  wild  in  the  vast  forests  of  America,  and  have  lost  all  the  most 
obvious  appearances  of  domestication.  The  wild  tribes  are  found  to  differ 
physically  from  the  domesticated  breeds,  from  which  they  are  known  to  have 
originated  ;  and  there  is  good  reason  to  regard  this  change,  as  a  partial  restora- 
tion of  the  primitive  characteristics  of  the  wild  stocks,  from  which  the  tamed 
animals  originally  descended.  Thus  we  find  that  the  Hog,  where  it  has  re- 
turned to  its  wild  state,  nearly  resembles  the  Wild  Boar,  which  has  never 
been  in  a  state  of  domestication.  The  colour  loses  the  variety  found  in  the 
domestic  breeds ;  the  Wild  Hogs  of  the  American  forests  being  uniformly 
black.  The  thin  covering  of  hair  and  scattered  bristles  is  replaced  by  a  thick 
fur,  often  somewhat  crisp  ;  beneath  which  is  found,  in  those  which  inhabit 
the  colder  regions,  a  species  of  wool.  The  head,  too,  becomes  much  larger 
in  these  wild  races,  as  in  the  original  Boar;  and  the  differences  in  the  conform- 
ation of  the  cranium,  between  these  and  the  domesticated  breeds,  are  fully 
equal  to  anything  that  is  seen  in  the  human  race. — The  variations  which  pre- 
sent themselves  in  other  races  of  domesticated  animals  introduced  into  South 
America  at  the  same  period, — such  as  the  horse,  ass,  ox,  sheep,  goat,  dog, 
cat,  and  gallinaceous  birds, — are  not  less  striking.— Still  more  remarkable 
variations  are  seen  in  certain  domesticated  breeds,  which  must  without  doubt 
have  sprung  from  the  same  stock  with  the  ordinary  ones,  although  their  origin 
cannot  be  traced  historically ;  thus,  in  some  localities  we  find  swine  with 
solid  hoofs ;  in  others,  the  hoof  is  cleft  into  five  parts ;  and  in  others,  again, 
the  toes  are  developed  to  a  monstrous  length. 


80  MUTUAL  RELATIONS  OF  THE  HUMAN  FAMILY. 

69.  Although  the  numerous  examples  furnished  by  the  Vegetable  Kingdom 
may  seem  to  have  but  a  remote  bearing  on  the  question,  it  would  still  be 
wrong  to  pass  them  by  without  notice ;  since  the  general  principles  already 
noticed  are  recognized  by  Botanists,  as  serving  for  the  discrimination  or  iden- 
tification of  species   of  Plants ;  to  which  they  apply  equally  with  Animals. 
We  have  abundant  evidence,  in  the  case  of  our  cultivated  fruits  and  flowers, 
of  the  origination  of  new  and  well-marked  varieties  from  stocks  originally  the 
same ;  the  differences  between  these  races  being  such,  as  would  undoubtedly 
have  led  to  their  being  ranked  as  distinct  species,  if  their  common  parentage 
were  not  known.    Thus,  of  the  numerous  widely-different  varieties  of  Apple, 
Pear,  Strawberry,  Plum,  &c.,  many  have  been  produced  in  our  own  time  ; 
and  there  is  no  doubt,  that  all  the  forms  of  each  fruit  are  descended  from 
wild  stocks,  extremely  unlike  any  one  of  them.     So  the  Cowslip,  Primrose, 
Oxslip,  and  Polyanthus,  which  were  formerly  regarded  as  constituting  at  least 
two  distinct  species,  have  been  shown  to  be  all  producible  from  the  seeds  of 
one  parent.    And  a  single  plant  of  the  Orchideous  tribe  has  borne  flowers  and 
pseudo-bulbs,  which  were  formerly  considered  as  characteristic  of  three  dis- 
tinct genera. 

70.  Of  the  origination  of  entirely  new  races  of  animals,  distinguished  by 
physical  peculiarities,  and  disposed  to  become  permanent  under  circumstances 
favourable  to  their  perpetuation,  we  have  frequent  examples  at  the  present 
time.     It  is  not  uncommon  to  meet  with  individuals  among  our  domesticated 
animals,  which  differ  from  others  of  their  kind,  in   some  marked  feature  of 
their  conformation.     If  this  be  of  a  nature  which  impairs  the  value  of  the 
animal,  care  is  taken  that  it  shall  not  propagate  its  race ;  but,  on  the  other 
hand,  if  it  afford  a  prospect  of  utility,  the  skill  of  the  breeder  is  employed  to 
perpetuate  it.     One  of  the  most  remarkable  examples  of  this  kind,  is  to  be 
Sound  in  the  origin  of  the  Ancon  or  Otter  breed  of  Sheep,  now  common  in 
New  England.     In  the   year  1791,  one  of  the  ewes  on  the  farm  of  Seth 
Wright,  in  the  State  of  Massachusetts,  produced  a  male  lamb,  remarkable  for 
the  singular  length  of  its  body,  the  shortness  of  its  limbs,  and  the  crookedness 
of  its  fore-legs.     This  physical  conformation,  incapacitating  the  animal  from 
leaping  fences,  appeared  to  the  farmers  around  so  desirable,  that  they  wished 
it  continued.     Wright  consequently  determined  on  breeding  from  this  ram  ; 
but  the  first  year  he  obtained  only  two  with  the  same  peculiarities.     In  the 
following  years,  he  obtained  greater  numbers ;  and  when  they  became  capable 
of  breeding  with  one  another,  the  new  race  became  permanent,— the  offspring 
invariably  having  the  JLncon  conformation,  when  both  the  parents  belonged 
to  that  breed.     In  the  Human  race,  it  is  not  uncommon  to  find  particular 
families  distinguished  by  the  possession  of  six  fingers  on  each  hand,  and  six 
toes  on  each  foot.     If  such  were  to  intermarry  exclusively  with  one  another, 
there  can  be  no  reasonable  doubt  that  the  children  would  invariably  exhibit 
the  same  peculiarity;  and  the  six-fingered  race,  which  now  tends,  whenever 
it  is  originated,  to  merge  in  the  more  general  form,  would  then  become  per- 
manent.   When  it  is  remembered  that  the  influence  of  a  scanty  population,  in 
the  early  ages  of  the  world,  would  have  been  precisely  the  same  as  that  which 
is  now  exercised  by  the  breeders  of  animals,  we  can  understand  why  the  va- 
rieties, which  then  arose,  should  have  had  a  much  greater  tendency  to  become 
permanent,  than  most  of  those  which  now  present  themselves.    At  the  present 
time,  any  peculiarity  which  may  occasionally  arise,  speedily  merges  by  inter- 
mixture with  the  mass,  and  returns  to  the  common  standard;  but  when  popu- 
lation was  scanty,  any  peculiarities  existing  in  one  family  would  be  perpetuated, 
by  the  intermixture  of  its  members,  rendered  necessary  by  their  isolation  from 
others ;  and  thus  a  new  race  would  originate. 

71.  For  the  cause  of  these  occasional  variations  from  the  common  type, 


ON  THE  VALUE  OF  SPECIFIC  DISTINCTIONS.  81 

we  must  look  in  part  to  the  original  constitution  of  the  species,  and  in  part 
to  the  influence  of  external  conditions.  As  already  mentioned,  there  is  a 
marked  difference  among  various  species  of  animals  (even  those  nearly  allied, 
such  as  the  Domestic  Cat  and  the  Tiger),  in  regard  to  their  respective  capa- 
cities for  variation.  And  among  the  peculiarities  of  conformation  which  oc- 
casionally present  themselves  in  the  Human  and  other  most  variable  species, 
there  are  several,  which  cannot  be  in  any  way  attributed  to  the  modifying 
influence  of  external  conditions; — such,  for  example,  as  the  development  of 
additional  fingers  or  toes,  the  alteration  in  the  number  of  the  vertebrae  in  the 
tail,  the  unusual  consolidation  or  separation  of  the  toes,  &c.  But  it  cannot 
be  doubted,  when  the  known  history  of  the  domesticated  races  is  fairly  con- 
sidered, that  a  change  of  external  circumstances  is  capable  of  exerting  a  very 
decided  influence  upon  the  physical  form,  upon  the  habits  and  instincts,  and 
upon  various  functions  of  life.  The  variations  thus  induced,  extend  to  con- 
siderable modifications  in  the  external  aspect,  such  as  the  colour,  the  texture, 
and  the  thickness  of  the  external  covering ;  to  the  structure  of  limbs,  and  the 
proportional  size  of  parts ;  to  the  relative  development  of  the  organs  of  the 
senses  and  of  the  psychical  powers,  involving  changes  in  the  form  of  the  cra- 
nium ;  and  to  acquired  propensities,  which,  within  certain  limits  (depending,  it 
would  appear,  on  their  connection  with  the  natural  habits  of  the  species),  may 
become  hereditary. 

4.  On  the  Extremes  of  Variation  among  the  Races  of  Men. 

72.  We  have  now  to  inquire,  in  the  third  place,  how  far   the  same  influ- 
ences might  be  expected  to  operate  in  the  Human  race ;  and  whether  the  ex- 
treme varieties,  which  we  enconuter   among  Mankind,  are  really  greater  than 
those,  which  we  meet  with  in  the  races  of  domesticated  animals,  known  to 
have  had  a  common  ancestry.     It  must  be  admitted  by  every  one,  that  both 
of  the  conditions  just  noticed  as  favouring  the  origination  of  peculiarities,  ope- 
rate to  their  fullest  extent  in  Man.     There  is  no  other  species  of  animals,  in 
which  an  equal  tendency  to  variation  exists.     The  different  individuals  of  the 
same  breed  of  Dogs,  for  example,  resemble  each  other  far  more  closely  in 
physical  and  mental  characters,  than  the  individual  men  of  one  nation ;  and 
there  is  no  species  of  animals,  which  possesses  an  equal  power  of  maintain- 
ing life  in  the  remote  extremes  of  climate,  atmospheric  pressure,  &c.,  which 
are  encountered  at  different  parts  of  the  earth's  surface,  and  at  different  ele- 
vations above  it.     Again,  we  should  expect  to  find  these  varieties  in  external 
circumstances,  together  with   the    change  of  habits  induced  by  civilization 
(which  is  far  greater  than  any  change  effected  by  domestication  in  the  condi- 
tion of  the  lower  animals),  producing  still  more  important  alterations  in  the 
physical  form  and  constitution  of  the  Human  body,  than  those  effected  in 
brutes  by  a  minor  degree  of  alteration.     And  it  may  be  reasonably  antici- 
pated, that,  as  just  now  explained,  there  would  be  a  greater  tendency  to  the 
perpetuation  of  these  varieties,  in   other  words,  to  the  origination  of  distinct 
races,  during  the  earlier  ages  of  the  history  of  the  race,  than  at  the  present 
time,  when,  in  fact,  by  the  increasing  admixture   of  races  which  have  long 
been  isolated,  there  is  a  tendency  to  the  fusion  of  all  these  varieties,  and  to  a 
return  to  a  common  type.     Now,  when  the  extreme  varieties  which  are  pre- 
sented by  the  different  races  of  Man  are  carefully  compared  together,  it  is 
found  that  their  differences  are  all  of  the  same  kind  as  those,  which  present 
themselves  among  the  breeds   of  domesticated  animals ;    and  do  not  by  any 
means  exceed  them  (perhaps  not  even  equalling  them  in  degree.     This  will 
be  shown  in  detail  hereafter. 

73.  It  appears,  then,  that  the  analogical  argument  derived  from  the  pheno- 


82  MUTUAL  RELATIONS  OF  THE  HUMAN  FAMILY. 

mena  presented  by  the  domesticated  species  among  the  lower  animals,  is  de- 
cidedly in  favour  of  the  specific  unity  of  the  Human  race ;  the  differences 
which  have  sprung  up,  in  course  of  time,  amongst  the  inhabitants  of  different 
parts  of  the  world,  being  such  as  we  have  a  fair  right  to  attribute — according  to 
the  recognized  principles  of  Zoology — to  the  modifying  influence  of  external 
conditions,  acting  upon  a  constitution  peculiarly  disposed  to  yield  to  it. 

5.   On  the  Value  of  Physiological  and  Psychological  Peculiarities,  as 
Specific  Distinctions. 

74.  We  have  now  to  inquire,  in  the  fourth  place,  what  other  arguments  ill 
favour  of  this  position  may  be  drawn  from  agreement  or  difference  in  Physi- 
ological and  Psychological  peculiarities.     A  comparison  of  the  physiological 
history  of  two  races,  is  often  found  to  afford  a  better  criterion  of  their  specific 
difference   or  identity,  than   the   comparison  of  their  structural  characters. 
Now,  in  every  important  point  of  physiological  history,  there  is  a  wonderful 
agreement  amongst  the  different  races  of  Men  ;  the  variations  not  being  greater 
than  are  those  with  which  we  meet  among  the  different  individuals  of  any 
one  race.     Thus,  we  not  only  find  the  average  duration  of  life  to  be  every- 
where the  same,  (making  allowance  for  circumstances  which  are  likely  to  in- 
duce disease),  but  the  various  epochs  of  life  have  a  close  correspondence, — 
such  as  the  times  of  the  first  and  second  dentition,  the  period  of  puberty,  the 
duration  of  pregnancy,  the  intervals  of  the   catamenia,  and   the  time  of  their 
final  cessation.     And  the  different  races  of  Man  are  all  subject  to  the  same 
diseases,  both   sporadic,  contagious,  and  epidemic ;  whilst  there   are  no  two 
really-distinct  species  among  the  lower  animals,  which  have  more  than  a  very 
slight  conformity  in  this  respect. 

75.  The  most  important  physiological  test  of  specific  unity  or  diversity,  is 
derived  from  the  phenomena  attending  the  Reproductive  process.     It  is  well 
known  that,  in  Plants,  the  stigma  of  the  flower  of  one  species  may  be  fertil- 
ized with  the  pollen  of  an  allied  species ;  and  that,  from  the  seeds  produced, 
plants   of  an   intermediate  character  may  be  raised.     These  hybrid  plants, 
however,  will  not  perpetuate  the  new  race  ;  for,  although  they  may  ripen  their 
seed  for  one  or  two  generations,  they  will  not  continue  to  reproduce  them- 
selves beyond  the  third  or  fourth.     But,  if  the  intervention  of  one  of  the  pa- 
rent species  be  employed, — its  stigma  being  fertilized  by  the*pollen  of  the 
hybrid,  or  vice  versa, — a  mixed  race  may  be  kept  up  for  some  time  longer  ; 
but  it  will  then  have  a  manifest  tendency  to  return  to  the  form  of  the  parent 
whose  intervention  has  been  employed.     Where,  on  the  other  hand,  the  pa- 
rents themselves  were   only  varieties,  the  hybrid  forms  but  another  variety, 
and  its  powers  of  reproduction  are  rather  increased  than  diminished ;  so  that 
it  may  continue  to  propogate  its  own  race,  or  may  be  used  for  the  production 
of  other  varieties,  almost  ad  infinitum.     In  this  way,  many  beautiful  new 
varieties  of  garden  flowers  have  been  obtained  ;  especially  among  such  species 
as   have   a  natural  tendency  to  change  their  aspect.     Amongst  Animals,  the 
limits  of  hybridity  are  much  more  narrow,  since  the  hybrid  is  totally  unable 
to  continue  its  race  with  one  of  its  own  kind  ;*  and  although  it  may  be  fertile 
with  one  of  its  parent  species,  the  progeny  will  of  course  approach  in  cha- 
racter to  the  pure  breed,  and  the  race  will  ultimately  merge  into  it.     On  the 
other  hand,  in  Animals,  as  among  Plants,  the  mixed  offsprings  originating  from 
different  races  within  the  limits  of  the  same  species,  generally  exceed  in  vi- 

*  One  or  two  instances  have  been  stated  to  occur,  in  which  a  Mule  has  produced  offspring 
from  union  with  a  similar  animal;  but  this  is  certainly  the  extreme  limit,  since  no  one  has 
ever  maintained  that  the  race  can  be  continued  further  than  the  second  generation,  without 
admixture  with  one  of  the  parent  species. 


DISTINCTIVE  PECULIARITIES  OF  THE  RACES  OF  MAN.  83 

gour,  and  in  the  tendency  to  multiply,  the  parent  races  from  which  they  are 
produced,  so  as  to  gain  ground  upon  the  older  varieties,  and  gradually  to  su- 
persede them.  In  this  manner,  by  the  crossing  of  the  breeds  of  our  domes- 
ticated animals,  many  new  and  superior  varieties  have  been  produced.  The 
general  principle  is,  then,  that  beings  of  distinct  species,  or  descendants  from 
stocks  originally  different,  cannot  produce  a  mixed  race,  which  shall  possess 
the  capability  of  perpetuating  itself;  whilst  the  union  of  varieties  has  a  tend- 
ency to  produce  a  race  superior  in  energy  and  fertility  to  its  parents. 

76.  The  application  of  this  principle  (if  it  be  admitted  as  such)  to  the  Hu- 
man races,  leaves  no  doubt  with  respect  to  their  specific  unity ;  for,  as  is  well 
known,  not  only  do  all  the  races  of  Men  breed  freely  with  each  other,  but  the 
mixed  race  is  generally  superior  in  physical  development,  and  in  tendency  to 
rapid  multiplication,  to  either  of  the  parent  stocks  ;  so  that  there  is  much  rea- 
son to  believe  that,  in  many  countries,  the  mixed  race  between  the  Aborigines 
and  European  colonizers  will  ultimately  become  the  dominant  power  in  the 
community.     This  is  especially  the  case  in  India  and  South  America. 

77.  Not  less  conclusive  is  the   result  of  the   test,  furnished  by  agreement 
or  difference  in  psychological  characters.    Among  the  lower  animals,  we  find 
every  species  characterised   by  the   possession  of  instincts  and  propensities 
peculiar  to  itself;  and  these  instincts  often  differ  remarkably  in  species,  which 
present  the  closest  structural  alliance.     On   the   other  hand,  in  the  several 
varieties   of  domesticated  animals,  notwithstanding  their  strongly-marked  di- 
versities of  physical  structure,  we  may  recognize  instincts  which  are  fun- 
damentally the  same,  although  they  have  been  modified  by  the  continued 
influence  of  Man,  and  by  the  new  circumstances  in  which  the  animals  are 
placed.     Now  from  an  impartial  survey  of  the  psychological  characters  of  the 
different  races  of  Men,  so  far  as  our  present  knowledge  extends,  the  follow- 
ing conclusion  may  be  drawn.     "  We  contemplate,  among  all  the  diversified 
tribes,  who  are  endowed  whh  reason  and  speech,  the   same  internal  feelings, 
appetencies,  and  aversions;  the  same  inward  convictions,  the  same  sentiments 
of  subjection  to  invisible   powers,  and   (more  or  less  fully  developed)  of  ac- 
countableness  or  responsibility  to  unseen   avengers  of  wrong  and   agents  of 
retributive  justice,  from  whose  tribunal  men  cannot  even  by  death  escape. 
We  find  everywhere  the  same  susceptibility,  though  not  always  in  the  same 
degree  of  forwardness  or  ripeness  of  improvement,  of  admitting  the  cultiva- 
tion of  those  universal  endowments,  of  opening  the  eyes  of  the  mind  to  the 
more  clear  and  luminous   views   which  Christianity  unfolds,  of  becoming 
moulded  to  the  institutions  of  religion  and  of  civilised  life  :  in  a  word,  the 
same  inward  and  mental  nature  is  to  be  recognized  in  all  the  races  of  men.* 

6.   On  the  Comparative  Peculiarities  of  the  Different  Races  of  Mankind. 

78.  We  have  now  to  inquire, fifthly  and  lastly,  whether  it  is  possible,  after 
a  detailed  and  careful  examination  of  the  ensemble  of  the   characters  of  the 
different  races  of  Men,  to  make  any  division  of  them  into   distinct  groups, 
capable  of  being  defined  by  such  constant  and  well-marked  features,  as  shall 
entitle  them  to  be  regarded  in  the  light  of  distinct  species.     The  general  re- 
sults, only,  of  this  inquiry,  can  here  be  given  ;  and   this   in  a  very  summary 
manner.     They  will  be  almost  entirely  drawn  from  the  profound   and  labo- 
rious investigations  of  Dr.  Prichard. 

79.  The  characters  which  are  most  relied  on  for  the  discrimination  of  the 
several  races  of  Mankind,  are  the  colour  of  the  skin,  the  nature  of  the  hair, 
and  the  conformation  of  the  skull  and  other  parts  of  the  skeleton.     The  Co- 

*  Pilchard's  Natural  History  of  Man,  p.  546. 


84  MUTUAL  RELATIONS  OF  THE  HUMAN  FAMILY. 

lour  of  the  skin  exists  in  the  epidermis  only;  and  it  depends  upon  the  ad- 
mixture of  certain  peculiar  cells,  termed  pigment-cells,  with  the  ordinary 
epidermic  cells.  These  pigment-cells,  as  will  be  shown  hereafter  (§  163),  are 
distinguished  by  their  power  of  generating  or  secreting  colouring-matter  of 
various  hues  ;  and  all  the  varied  shades  of  colour,  presented  by  the  different 
races  of  men,  are  due  to  the  relative  amount  of  these  cells,  and  to  the  parti- 
cular tint  of  the  pigment  which  they  form.  It  would  be  easy,  by  selecting 
well-marked  specimens  of  each  race,  to  make  it  appear  that  colour  affords 
sufficient  distinctive  marks  for  their  separation :  thus,  for  example,  the  fair 
and  ruddy  Saxon,  the  jet-black  Negro,  the  olive  Mongolian,  and  the  copper- 
coloured  North  American,  would  seem  positively  separated  from  each  other 
by  this  character,  propagated,  as  it  seems  to  be,  with  little  or  no  perceptible 
change,  from  generation  to  generation.  But  although  such  might  appear  to 
be  the  clear  and  obvious  result  of  a  comparison  of  this  kind,  yet  a  more  pro- 
found and  comprehensive  survey  tends  to  break  down  the  barrier  that  would 
be  thus  established.  For,  on  tracing  this  character  through  the  entire  family 
of  Man,  we  find  the  isolated  specimens  just  noticed  to  be  connected  by  such 
a  series  of  links,  and  the  transition  from  one  to  the  other  to  be  so  very  gradual 
that  it  is  impossible  to  say  where  the  line  is  to  be  drawn.  There  is  nothing 
here,  then,  which  at  all  approaches  to  the  fixed  and  definite  marks,  which  have 
been  noticed  as  serving — though  equally  trivial  in  themselves — to  establish 
specific  distinctions  among  other  tribes  of  animals. 

80.  But  further,  there  is  abundant  evidence  that  these  distinctions  are  far 
from  being  constantly  maintained,  even  in  any  one  race.     For  among  all  the 
principal  subdivisions,  albinoism,  or  the  absence  of  pigment-cells,  occasion- 
ally presents  itself;  so  that  the  fair  skin  of  the  European  may  present  itself 
in  the  offspring  of  the  Negro  or  of  the  Red  Man.     On  the  other  hand,  in- 
stances are  by  no  means  rare,  of  the  unusual  development  of  pigment-cells 
in  individuals  of  the  fair-skinned  races  ;  so;  that  parts  of  the  body  are  of  a 
dark  red  or  brown  hue,  or  are  even  quite   black.     Such  modifications  may 
seem  of  little  importance  to  the  argument;  since  they  are   confined  to  indi- 
viduals, and  may  be  put  aside  as  accidental.     But  there  is  ample  evidence, 
that  analogous  changes  may  take  place  in  the  course  of  time,  which  tend  to 
produce  a  great  variety  of  shades  of  colour,  in  the  descendants  of  any  one 
stock.     Thus,  in  the  great  Indo-Atlantic  family,  which  may  be  unquestion- 
ably regarded  as  having  had  a  common  origin,  we  find  races  with  fair  com- 
plexion, yellow  hair,  and  blue  eyes, — others  presenting  the  xanthous  or  olive 
hue,— and  others  decidedly  black.     A  similar  diversity  may  be  see,n  among 
the  American  races,  which  are  equally  referrible  to  one  common  stock  ;  and 
it  exists  to  nearly  the  same  extent  among  the  African  nations,  which  are  simi- 
larly related  to  each  other.     It  may  be  freely  admitted  that,  among  European 
colonists  settled  in  hot  climates,  such  changes  do  not  present  themselves  within 
a  few  generations  ;  but  in  many  well-known  instances  of  earlier  colonization 
they  are  very  clearly  manifested.     Thus  the  wide  dispersion  of  the  Jewish 
nation,  and  their  remarkable  isolation  (maintained  by  their  religious  observ- 
ances) from  the  people  among  whom  they  live,  render  them  peculiarly  appro- 
priate subjects  for  such  observations ;  and  we  accordingly  find,  that  the  bru- 
nette complexion  and  dark  hair,  which  are  usually  regarded  as  characteristic 
of  the  race,  are  frequently  superseded,  in  the   Jews  of  Northern  Europe,  by 
red  or  brown  hair  and  fair  complexion ;  whilst  the  Jews  who  settled  in  India 
some  centuries  ago,  have  become  as  dark  as  the  Hindoos  around  them. 

81.  The  relation  of  the  complexions  of  the  different  races  of  Men  to  the 
climates  they  respectively  inhabit,  is  clearly  established  by  an  extended  com- 
parative survey  of  both.     From   such  a  survey  the   conclusion  is  inevitable, 
that  the  intertropical  region  of  the  earth  is  the  principal  seat  of  the  black  races 


DISTINCTIVE  PECULIARITIES  OF  THE  RACES  OF  MAN.  85 

of  Men  ;  whilst  the  region  remote  from  the  tropics  is  that  of  the  white  races  ; 
and  that  the  climates  approaching  the  tropics  are  generally  inhabited  by  na- 
tions, which  are  of  an  intermediate  complexion.  To  this  observation  it  may 
be  added,  that  high  mountains,  and  countries  of  great  elevation,  are  generally 
inhabited  by  people  of  a  lighter  colour,  than  are  those  of  which  the  level  is 
low,  such  as  swampy  or  sandy  plains  upon  the  sea-coast.  These  distinc- 
tions are  particularly  well  seen  in  Africa,  where  the  tropics  almost  exactly 
mark  out  the  limits  of  the  black  complexion  of  the  inhabitants  ;  and  where 
the  deepest  hue  is  to  be  seen  among  the  Negroes  of  the  Guinea  Coast,  whose 
residence  unites  both  the  conditions  just  mentioned. 

82.  The  nature  of  the  Hair  is,  perhaps,  one  of  the  most  permanent  charac- 
teristics of  different  races.     In  regard  to  its  colour,  the  same  statements  apply, 
as  those  just  made  with  respect  to  the  colour  of  the  skin;  the  variety  of  hue 
being  given  by  pigment-cells,  which  may  be  more  or  less  developed  under 
different  circumstances.     But  it  has  been  thought  that  its  texture  afforded  a 
more  valid  ground  of  distinction ;  and  it  is  commonly  said  that  the  substance 
which  grows  on  the  head  of  the  African  races,  and  of  some  other  dark-colour- 
ed tribes  (chiefly  inhabiting  tropical  climates),  is  wool,  and  not  hair.     This, 
however,  is  altogether  a  mistake :  for  microscopic  examination  clearly  de- 
monstrates, that  the  hair  of  the  Negro  has  exactly  the  same  structure  with 
that  of  the  European ;  and  that  it  does  not  bear  any  resemblance  to  wool,  save 
in  its  crispness  and  tendency  to  curl.     Moreover,  even  this  character  is  far 
from  being  a  constant  one ;  for,  whilst  Europeans  are  not  unfrequently  to  be 
met  with,  whose  hair  is  as  crisp  as  that  of  the  Negro,  there  is  a  great  variety 
amongst  the  Negro  races  themselves,  which  present  every  gradation  from  a 
completely  crisp  (or  what  is  termed  woolly)  hair,  to  merely  curled  or  even 
flowing  locks.     A  similar  observation  holds  good  in  regard  to  the  natives  of 
the  islands  of  the  great  Southern  Ocean,  where  some  individuals  possess  crisp 
hair,  whilst  others,  of  the  same  race,  have  it  merely  curled.    It  is  evident,  then, 
that  no  characters  can  be  drawn  from  the  colour  or  texture  of  the  hair  in  Man, 
sufficiently  fixed  and  definite  to  serve  for  the  distinction  of  races:  and  this 
view  is  borne  out  by  the  evident  influence  of  climate,  in  producing  changes 
in  the  hairy  covering  of  almost  every  race  of  domestic  animals ; — the  change 
often  manifesting  itself  in  the  very  individuals  that  are  transported  from  one 
country  to  another,  and  showing  itself  yet  more  distinctly  in  succeeding  gene- 
rations. 

83.  It  has  been  supposed,  that  varieties  in  the  configuration  of  the  Skeleton 
would  afford  characters  for  the  separation  of  the  Human  races,  more,  fixed 
and  definite  than  these  derived  from  differences  in  the  form,  colour,  and  tex- 
ture of  the  soft  parts  which  clothe  it.     And   attention  has  been  particularly 
directed  to  the  skull  and  the  pelvis,  as  affording  such  characters.     It  has  been 
generally  laid  down   as  a  fundamental  principle,  that  all  those  notions  which 
are  found  to  resemble  each  other  in  the  shape  of  their  heads,  must  needs  be 
more  nearly  related  to  each  other,  than  they  are  to  tribes  of  Men  who  differ 
from  them  in  this  particular.     But  if  this  principle  be  rigorously  carried  out, 
it  will  tend  to  bring  together  races,  which   inhabit  parts  of  the  globe  very  re- 
mote from  each  other,  and  which  have  no  other  mark  of  affinity  whatever : 
whilst,  on  the  other  hand,  it  will  often   tend  to   separate  races,  which  every 
other  character  would  lead  us  to  bring  together.     It  is  to  be  remembered, 
moreover,  that  the  varieties  in  the  conformation  of  the  skeleton,  presented  by 
the  breeds  of  domesticated  animals,  are  at  least  equal  to  those  which  are  ma- 
nifested in  the  conformation  and  colour  of  their  soft  parts ;  and  we  might  rea- 
sonably expect,  therefore,  to  meet  with  similar  variations  among  the  Human 
races.     It  is  probable,  however,  that  climate  has  not  so  much  influence  in 
producing  such  changes  in  the  configuration  of  the  body,  as  is  exerted  by  the 

8 


86 


MUTUAL  RELATIONS  OF  THE  HUMAN  FAMILY. 


peculiar  habits  and  mode  of  life  of  the  different  races ;  and  Dr.  Prichard  has 
pointed  out  a  very  remarkable  relation  of  this  kind,  in  regard  to  the  three 
principal  types  of  form  presented  by  the  skull. 

84.  Among  the  rudest  tribes  of  Men,  hunters  and  savage  inhabitants  of  fo- 
rests, dependent  for  their  supply  of  food  on  the  accidental  produce  of  the  soil 
or  on  the  chase, — among  whom  are  the  most  degraded  of  the  African  nations, 
and  the  Australian  savages, — a  form  of  head  is  prevalent,  which  is  most  aptly 
distinguished  by  the  term  prognathous,  indicating  a  prolongation  or  forward- 
Fig.  7. 


Profile  and  basal  views  of  the  prognathous  skull  of  a  Negro. 

extension  of  the  jaws.  This  character  is  most  strongly  marked  in  the  Ne- 
groes of  the  Gold  Coast,  whose  skulls  are  usually  so  formed,  as  to  give  the 
idea  of  lateral  compression.  The  temporal  muscles  have  a  great  extent,  rising 
high  on  the  parietal  bones  ;  the  cheek-bones  project  forward,  and  not  out- 
ward ;  the  upper  jaw  is  lengthened  and  projects  forwards,  giving  a  similar 
projection  to  the  alveolar  ridge  and  to  the  teeth;  and  the  lower  jaw  has 
somewhat  of  the  same  oblique  projection,  so  that  the  upper  and  lower  incisor 
teeth  are  set  at  an  obtuse  angle  to  each  other,  instead  of  being  nearly  in  pa- 
rallel planes,  as  in  the  European.  From  the  shape  of  the  upper  jaw  alone, 
would  result  a  marked  diminution  in  the  facial  angle,  measured  according  to 
the  method  of  Camper;  but  this  diminution  is  far  from  being  sufficient  to  ap- 
proximate the  Ethiopian  races  to  the  higher  Apes,  as  some  have  supposed  it 
to  be.  For,  whilst  the  average  facial  angle  of  the  European  may  be  stated  at 
80°,  and  that  of  the  Negro  at  70°,  that  of  the  adult  Chimpanzee  is  only  35°, 
and  that  of  the  adult  Orang  only  30°.*  Independently  of  the  diminution  of 
the  facial  angle,  resulting  from  the  projection  of  the  upper  jaw,  it  is  quite  cer- 
tain that,  in  the  typical  prognathous  skull,  there  is  a  want  of  elevation  of  the 
forehead ;  but  it  does  not  appear  that  there  is  a  corresponding  diminution  in 
the  capacity  of  the  cranial  cavity,  the  retreating  form  of  the  forehead  being 
partly  due  to  the  general  elongation  of  the  skull  in  the  antero-posterior  direc- 
tion. Nor  is  it  true,  as  stated  by  some,  that  the  position  of  the  foramen  mag- 
num in  the  Negro  is  decidedly  behind  that,  which  it  holds  in  the  European, 
— in  this  respect  approaching  that  of  the  Apes  (§  51) :  since,  if  due  allowance 

*  The  different  statements  made  by  some  writers,  who  have  estimated  the  facial  angle  of 
the  higher  Apes  at  from  60°  to  64°,  are  due  to  the  measurements  having  been  made  upon 
young  skulls;  the  projection  of  the  jaws,  in  these  animals,  undergoing  an  extraordinary  in- 
crease at  the  time  of  the  second  dentition. 


DISTINCTIVE  PECULIARITIES  OF  THE  RACES  OF  MAN. 


87 


be  made  for  the  projection  of  the  upper  jaw,  this  aperture  is  found  to  have 
the  same  position  in  the  prognathous  skull  as  in  the  oval  one,  namely,  ex- 
actly behind  the  transverse  line  bisecting  the  antero-posterior  diameter  of  the 
base  of  the  cranium.  The  prognathous  skull  is  further  remarkable  for  the 
large  development  of  the  parts  connected  with  the  organs  of  sense,  especially 
those  of  smell  and  hearing.  The  aperture  of  the  nostrils  is  very  wide  ;  and 
the  internal  space  allowed  for  the  expansion  of  the  Schneiderian  membrane, 
and  for  the  distribution  of  the  olfactory  nerve,  is  much  larger  than  in  most 
European  heads.  The  posterior  openings  of  the  nasal  cavity  are  not  less  re- 
markable for  their  width  than  the  anterior.  The  external  auditory  meatus  is 
also  peculiarly  wide  and  spacious ;  and  the  orbital  cavities  have  been  thought 
to  be  of  more  than  ordinary  capacity, — but  this  last  is  by  no  means  a  constant 
character. 

85.  A  second  shape  of  the  head,  very  different  from  the  preceding,  belongs 

Fig  8. 


Front  and  basal  views  of  the  pyamidal  skull  of  an  Esquimaux. 

principally  to  the  nomadic  races,  who  wander  with  their  herds  and  flocks 
over  vast  plains ;  and  to  the  tribes  who  creep  along  the  shores  of  the  Icy  Sea, 
and  live  partly  by  fishing,  and  in  part  on  the  flesh  of  their  reindeer.  This 
form,  designated  by  Dr.  Prichard  as  the  pyramidal,  is  typically  exhibited  by 
various  nations  of  Northern  and  Central  Asia ;  and  is  seen  in  an  exaggerated 
degree,  in  the  Esquimaux.  Its  most  striking  character  is  the  lateral  or  out- 
ward projection  of  the  zygoma,  which  is  due  to  the  form  of  the  malar  bones. 
These  do  not  project  forwards  and  downwards  under  the  eyes,  as  in  the  pro- 
gnathous skull ;  but  take  a  direction  laterally  or  outwards,  forming,  with  the 
zygomatic  process  of  the  temporal  bone,  a  large  rounded  sweep  or  segment 
of  a  circle.  From  this,  in  connection  with  the  narrowness  of  the  forehead, 
it  results,  that  lines  drawn  from  the  zygomatic  arches,  touching  the  temples  on 
either  side,  instead  of  being  parallel  (as  in  Europeans),  meet  over  the  forehead, 
so  as  to  form  with  the  basis  a  triangular  figure.  The  upper  part  of  the  face 
being  remarkably  flat,  the  nose  also  being  flat,  and  the  nasal  bones,  as  well  as 
the  space  between  the  eyebrows,  being  nearly  on  the  same  plane  with  the 
cheek-bones,  the  triangular  space  bounded  by  these  lines  may  be  compared  to 
one  of  the  faces  of  a  pyramid.  The  orbits  are  large  and  deep ;  and  the  pecu- 
liar conformation  of  the  bones  which  surround  it,  gives  to  the  aperture  of  the 
lids  an  appearance  of  obliquity, — the  inner  angle  seeming  to  be  directed 
downwards.  The  whole  face,  instead  of  presenting  an  oval  form,  as  in  most 
Europeans  and  Africans,  is  of  a  lozenge-shape.  The  greater  relative  develop- 


88 


MUTUAL  RELATIONS  OE  THE  HUMAN  FAMILY. 


Fig.  9. 


Oval  skull  of  a  European. 


merit  of  the  zygomatic  bones,  and  of  the  bones  of  the  face  altogether,  when 
compared  with  the  capacity  of  the  cranium,  indicates  in  the  pyramidal  skull 
a  more"  ample  extension  of  the  organs  subservient  to  sensation ;  the  same 
effect  being  thus  produced  by  lateral  expansion,  as  by  the  forward  extension 
of  the  facial  bones  in  the  prognathous  skulls. 

86.  The  most  civilized  races, — those  which  live  by  agriculture  and  the  arts 
of  cultivated  life,— all  the  most  intellectually-improved  nations  of  Europe  and 
Asia,  have  a  shape  of  the  head,  which  differs  from  both  the  preceding  forms, 

and  which  may  be  termed  oval  or 
elliptical.  This  at  once  approves  it- 
self as  a  more  symmetrical  form ;  no 
part  having  an  excessive  prominence; 
whilst  on  the  other  hand,  there  is  no- 
where an  appearance  of  undue  flat- 
tening or  compression.  The  head  is 
altogether  of  a  rounder  shape  than  in 
other  varieties;  and  the  forehead  is 
more  expanded ;  while  the  maxillary 
bones  and  the  zygomatic  arches  are 
so  formed,  as  to  give  the  face  an  oval 
shape,  nearly  on  a  plane  with  the 
forehead  and  cheek-bones,  and  not 
projecting  towards  the  lower  part. 
Owing  to  the  more  perpendicular  di- 
rection of  the  alveolar  processes,  the 
front  teeth  are  fixed  in  planes,  which 
are  nearly  or  quite  parallel  to  each  other.  The  principal  features  in 
this  form  of  cranium  are  thus  of  a  negative  character ;  the  chief  positive  dis- 
tinction is  the  large  development  of  the  cranial  cavity,  and  especially  the  full- 
ness and  elevation  of  the  forehead,  in  proportion  to  the  size  of  the  face  ;-— 
indicating  the  predominance  of  the  intellectual  powers  over  those  merely 
instinctive  propensities,  which  are  more  directly  connected  with  sensations. 
Among  European  nations,  the  Greeks  have  probably  displayed  the  greatest 
symmetry  and  perfection  in  the  form  of  the  head;  but  various  departures 
may  be  traced,  towards  the  preceding  forms,  when  we  compare  the  crania  of 
different  races,  and  even  of  individuals,  belonging  to  the  same  stock, — some 
approaching  the  pyramidal  form  of  the  Northern  Asiatics,  whilst  others  ap- 
proximate to  the  prognathous  type  of  the  Negro. 

87.  The  influence  of  habits  of  life,  continued  from  generation  to  generation, 
upon  the  form  of  the  head,  is  remarkably  evinced  by  the  transition  from  one 
type   to   another,  which  may  be  observed  in  nations  that  have  undergone  a 
change  in  their  manners,  and  customs,  and  have  made  an  advance  in  civiliza- 
tion.    Thus,  to  mention  but  one  instance,  the  Turks  at  present  inhabiting  the 
Ottoman  and  Persian  empires,  are  undoubtedly,  descended  from  the  same  stock 
with  the  nomadic  races,  which  are  still  spread  through  Central  Asia.     The 
former,  however,  having  conquered  the  -countries  which   they  now  inhabit, 
eight  centuries  since,  have  gradually  settled  down  to  the  fixed  and  regular  ha- 
bits of  the  Indo-European  race,  and  have  made  corresponding  advances  in 
civilization ;  whilst  the  latter  have  continued  their  wandering  mode  of  life, 
•and  can  scarcely  be  said  to  have  made  any  decided  advance  during  the  same 
interval.     Now,  the  long-since   civilized  Turks  have  undergone  a  complete 
transformation  into  the  likeness  of  Europeans  ;  whilst  their  nomadic  relatives 
retain  the  pyramidal  configuration  of  the  skull  in  a  very  marked  degree.  Some 
have  attributed  this  change  in  the  physical  structure  of  the  Turkish  race,  to 
the  introduction  of  Circassian  slaves  into  the  harems  of  the  Turks ;  but  this 


DISTINCTIVE  PECULIARITIES  OF  THE  RACES  OF  MAN.  89 

could  only  affect  the  opulent  and  powerful  amongst  the  race ;  and  the  great 
mass  of  the  Turkish  population  have  always  intermarried  among  themselves. 
The  difference  of  religion  and  manners  must  have  kept  them  separate  from 
those  Greeks  whom  they  subdued  in  the  new  Ottoman  countries ;  and  in  Per- 
sia, the  Tajiks,  or  real  Persians,  still  remain  quite  distinct  from  their  Turkish 
rulers,  belonging  to  a  different  sect  among  the  Mussulmans,  and  commonly 
living  apart  from  them.  In  like  manner,  even  the  Negro  head  and  face  may 
become  assimilated  to  the  European,  by  long  subjection  to  similar  influences; 
thus,  in  some  of  our  older  West  Indian  Colonies,  it  is  not  uncommon  to  meet 
with  Negroes, — the  descendants  of  those  first  introduced  there, — who  exhibit 
a  very  European  physiognomy ;  and  it  has  even  been  asserted  that  a  Negro 
belonging  to  the  Dutch  portion  of  Guiana,  may  be  distinguished  from  another 
belonging  to  the  British  settlements,  by  the  similarity  of  his  features  and  ex- 
pression to  those  which  peculiarly  characterize  his  masters.  The  effect  could 
not  be  here  produced  by  the  intermixture  of  bloods,  since  this  would  be  made 
apparent  by  alteration  of  colour. 

88.  Next  to  the  characters  derived  from  the  form  of  the  head,  those  which 
are  founded  upon  the  form  of  the  pelvis  seem  entitled  to  rank.     These  have 
been   particularly  examined  by  Professors  Vrolik  and  Weber.     The  former 
concluded  from  his  examinations  of  this  part  of  the  skeleton,  that  the  pelvis 
of  the  Negress,  and  still  more  that  of  the  female  Hottentot,  approximates  to 
that  of  the  Simiae  in  its   general  configuration  ;  especially  in  its  length  and 
narrowness, — the  iliac  bones  having  a  more  vertical  position,  so  that  the  ante- 
rior spines  approach  one  another  much  more  closely  than  they  do  in  the  Euro- 
pean ;  and  the  sacrum  also  being  longer  and  narrower.     On  the   other  hand, 
Prof.  Weber  concludes,  from  a  more  comprehensive  survey,  that  no  particular 
figure  is  a  permanent  characteristic  of  any  one  race.     He  groups  the  principal 
varieties  which  he  has  met  with,  according  to  the  form  of  the  upper  opening, 
— whether  oval,  round,  four-sided,  or  wedge-shaped.     The  first  of  these  is 
most  frequent  in  the  European  races  ;  the  second,  among  the  American  races  ; 
the  third,  most  common  among  the  Mongolian  nations,  corresponds  remarka- 
bly with  the 'form  of  their  heads;  whilst  the  last  chiefly  occurs  among  the 
races   of  Africa,  and  is  in  like  manner  conformable   with  the  oblong  com- 
pressed form  usually  presented  by  their  cranium.     But  though  there  are  par- 
ticular shapes  which  are  most  prevalent  in  each  race,  yet  there  are  numerous 
individual  deviations ;  of  such  a  nature,  that  every  variety  of  form  presents 
itself  occasionally  in  any  given  race. 

89.  Other  variations  have  been  observed  by  anatomists,  in  the  relative  length 
of  the  bones,  and  in  the  shape  of  the  limbs,  between  the  different  races  of 
Man ;  but  these  also  seem  to  have  reference  to  the  degree  of  civilization,  and 
to  the  regularity  of  the  supply  of  wholesome  nutriment.     It  is  generally  to 
b«  observed,  that  the  races  least  improved  by  civilization,  like  the  uncultivated 
breeds  of  animals,  have  slender,  lean,  and  elongated  limbs ;  this  may  be  es- 
pecially remarked  in  the  natives  of  Australia.     In  nearly  all  the  less  civilized 
races  of  Men,  the  limbs  are  more  crooked  and  badly  formed  than  the  average 
of  those  of  Europeans;  and   this  is  particularly  the  case  in  the  Negro,  the 
bones  of  whose  legs  bow  outwards,  and  whose  feet  are  remarkably  flat.     It 
has  been  generally  believed,  that  the  length  of  the  forearm  in  the  Negro  is  so 
much  greater  than  in  the  European,  as  to  constitute   a  real  character  of  ap- 
proximation to  the  Apes.     The  difference,  however,  is  in  reality  extremely 
slight ;  and  is  not  at  all  comparable  with  that  which  exists  between  the  most 
uncultivated  races  of  Men  and  the  highest  Apes  (§  54).     And  in  regard  to  all 
the  peculiarities  here  alluded  to,  it  is  to  be  observed,  that  they  can   only  be 
discovered  by  the  comparison  of  large  numbers  of  one  race  with  correspond- 
ing numbers  of  another ;  for  individuals  are  found  in  every  tribe,  possessing 


90  MUTUAL  RELATIONS  OF  THE  HUMAN  FAMILY. 

the  characters  which  distinguish  the  majority  of  the  other  race.  Any  such 
peculiarities,  therefore,  are  totally  useless  as  the  foundation  of  specific  charac- 
ters ;  being  simply  variations  from  the  ordinary  type,  resulting  from  causes 
which  might  affect  the  entire  race,  as  well  as  individuals. 

90.  The  connection  between  the  general  form  of  the  body,  on  the  one  hand, 
and  the  degree  of  civilization  (involving  the  regular  supply  of  nutriment)  on 
the  other,  is  made  apparent,  not  merely  by  the  improvement  which  we  per- 
ceive in  the  form,  development,  and  vigour  of  the  frame,  as  we  advance  from 
the  lowest  to  the  most  cultivated  of  the  Human  races  ;  but  also  by  the  degra- 
dation which  is  occasionally  to  be  met  with  in  particular  groups  of  the  higher 
tribes,  which  have  been  subjected  for  several  generations  to  the  influence  of 
depressing  causes.     Of  this  class  of  facts,  the  following  is  a  very  interesting 
example  : — "  On  the  plantation  of  Ulster,  and  afterwards  on  the  successes  of 
the  British  against  the  rebels  of  1641  and  1689,  great  multitudes  of  the  na- 
tive Irish  were  driven  from  Armagh  and  the  south  of  Down,  into  the  moun- 
tainous tract  extending  from  the  barony  of  Flews  eastward  to  the  sea : — on 
the  other  side  of  the  kingdom,  the  same  race  were  expelled  into  Leitrim,  Sligo 
and  Mayo.     Here  they  have  been  almost  ever  since,  exposed  to  the  worst 
effects  of  hunger  and  ignorance,  the  two  great  brutalizers  of  the  human  race. 
The  descendants  of  these  exiles  are  still  readily  distinguishable  from   their 
kindred  in  Meath,  and  in  other  districts  where  they  are  not  in  a  state  of  phy- 
sical degradation  ;  being  remarkable  for  open  projecting  mouths,  with  prominent 
teeth  and  exposed  gums ;  their  advancing  cheek-bones  and  depressed  noses 
bearing  barbarism  on  their  very  front.     In  Sligo  and  northern  Mayo,  the  con- 
sequences of  two  centuries  of  degradation  and  hardship  exhibit  themselves  in 
the  whole  physical  condition  of  the  people ;  affecting  not  only  the  features, 
but  the  frame,  and  giving  such  an  example  of  human  deterioration  from  known 
causes,  as   almost  compensates,  by  its  value   to   future  ages,  for  the  suffering 
and  debasement  which  past  generations  have  endured  in  perfecting  its  appall- 
ing lesson.     Five  feet  two  inches   upon  an  average,  pot-bellied,  bow-legged, 
abortively-featured,  their  clothing  a  wisp  of  rags, — these  spectres  of  a  people, 
that  were  once  well-grown,  able-bodied,  and  comely,  stalk  abroad  into  the  day- 
light of  civilization,  the  annual  apparitions  of  Irish  ugliness  and  Irish  want. 
In  other  parts  of  the  island,  where  the  population  has  never  undergone  the 
influence  of  the  same  causes  of  physical  degradation,  it  is  well  known  that 
the   same  race  furnishes  the  most  perfect  specimens  of  human  beauty  and 
vigour,  both  mental  and  bodily."* 

91.  From  the  foregoing  survey  of  the  phenomena,  bearing  upon  the  ques- 
tion of  the  specific  unity  or  diversity  of  the  Human  races,   the  following 
conclusions  may  be  drawn  : — 

I.  That  the  physical  constitution  of  Man  is  peculiarly  disposed,  like  that 
of  the  domesticated  animals,  to  undergo  variations;  some  of  which  can  be 
traced  to  the  influence  of  external  causes ;  whilst  others  are  not  so  explicable, 
and  must  be  termed  spontaneous. 

II.  That  the  extreme  variations  which  present  themselves,  between  the 
races  apparently  the  most  removed  from  one  another,  are  not  greater  in  degree 
than  those  which  exist  between  the  different  breeds  of  domesticated  animals, 
which  are  known  to  have  descended  from  a  common  stock;  and  that  they 
are  of  the  same  kind  with  the  variations  which  present  themselves  in  any 
one  race  of  Mankind, — the  difference  of  degree  being  clearly  attributable,  in 
the  majority  of  cases,  to  the  respective  conditions  under  which  each  race 
exists. 

III.  That  none  of  the  variations,  which  have   been  pointed  out  as  existing 

*  See  Dublin  University  Magazine,  No.  XL VIII. 


PRINCIPAL  BRANCHES  OF  THE  HUMAN  FAMILY.  91 

between  the  different  races  of  mankind,  have  the  least  claim  to  be  regarded 
as  valid  specific  distinctions ;  being  entirely  destitute  of  that  fixity,  which  is 
requisite  to  entitle  them  to  such  a  rank;  and  exhibiting,  in  certain  groups  of 
each  race,  a  tendency  to  pass  into  the  characters  of  some  other. 

IV..  That,  in  the  absence  of  any  valid  specific  distinctions,  we  are  required, 
by  the  universally-received  principles  of  zoological  science,  to  regard  all  the 
races  of  Mankind  as  belonging  to  the  same  species,  or  (in  other  words)  as 
having  had  either  an  identical  or  similar  parentage ;  and  that  this  conclusion 
is  supported  by  the  positive  evidence,  afforded  by  the  agreement  of  all  the 
races  in  the  physiological  and  psychological  characters,  that  most  distinguish 
them  from  other  species,  and  especially  by  the  ready  propagation  of  mixed 
breeds  or  hybrid  races. 

7.  Principal  Branches  of  the  Human  Family. 

92.  The  above  conclusions  are  found  to  be  in  entire  accordance  with  those 
derived  from  an  examination  of  the  relative  affinities  of  the  different  races  of 
Men  at  present  existing ;  as  far  as  these  are  deducible  from  the  analogies  of  their 
language,  from  their  correspondence  in  peculiar  habits  and  observances,  and  from 
traditional  or  other  evidence  in  regard  to  their  original  sources.  For  it  appears, 
from  such  investigations,  that  very  great  difference  in  colour,  texture  of  the  hair, 
form  of  the  skull,  and  other  important  physical  characters,  exist  among  nations, 
which  may  be  referred  with  great  confidence  to  a  common  source ;  whilst  on 
the  other  hand,  we  find  traits  of  physical  resemblance,  in  tribes  which  exist 
under  corresponding  circumstances  in  remote  parts  of  the  world,  and  which 
seem  to  have  nothing  else  in  common.  It  has  been  attempted  by  Blumenbach 
and  Cuvier  to  arrange  the  different  races  of  Men  under  five  principal  varie- 
ties; the  Caucasian,  Mongolian,  Ethiopian,  Malay,  and  American.  But,  for 
the  reason  just  given,  it  is  impossible  to  establish  any  constant  distinguishing 
characters,  which  shall  serve  to  mark  these  clearly  ouj; ;  and  it  moreover  ap- 
pears that  several  additional  groups  must  be  created,  for  the  reception  of  tribes, 
that  differ  as  much  from  the  preceding  as  these  do  from  each  other.  In  the 
following  brief  enumeration,  the  views  of  Dr.  Prichard  will  be  adopted. 

93.  The  Caucasian  variety  of  Blumenbach  and  Cuvier  was  so  named  from  the 
idea,  that  the  Caucasian  range  of  mountains  might  be  regarded  as  the  centre 
or  focus  of  the  races  belonging  to  it;  and  that  the  Caucasian  people  present 
the  typical  conformation  of  the  variety  in  the  most  perfect  degree.  Neither 
of  these  ideas  are  correct,  however;  and  some  other  designation  might  very 
properly  be  substituted  for  that  which  conveys  them.  In  this  variety  are  pre- 
sented all  the  characters  of  highest  physical  perfection  of  the  race,  such  as 
were,  perhaps,  most  pre-eminently  combined  among  the  Ancient  Greeks;  as 
well  as  those  of  intellectual  and  moral  elevation.  No  uniformity  exists,  how- 
ever, as  to  colour;  for  this  character  presents  every  intermediate  gradation, 
from  the  fair  and  florid  hue  of  the  Northern  Europeans,  to  the  jet  black  of 
many  tribes  in  North  Africa  and  Hindustan.  The  hair  is  generally  long  and 
flexible ;  but  departures  from  the  ordinary  type  present  themselves  in  this 
respect,  also,  both  among  individuals  and  among  whole  tribes.  Although 
there  is  general  agreement  in  these  characters  among  the  nations  of  South- 
western Asia,  Northern  Africa,  and  nearly  the  whole  of  Europe,  yet  we  are 
required  by  the  evidence  of  ancient  history,  as  well  as  by  the  characters  de- 
rived from  language,  to  separate  these  nations  into  two  groups ;  which  appeared 
to  have  been  distinct  from  each  other  at  the  earliest  JSriod  of  which  we  have 
any  traces  ;  and  which  we  must  regard,  therefore,  as  alike  entitled  to  rank  as 
primary  branches  of  the  human  family.  These  are  the  Syro-Arabian,  and  the 
Indo-European  groups  of  nations. 


92  MUTUAL  RELATIONS  OF  THE  HUMAN  FAMILY. 

94.  The  Syro-Jlrabian  nations,  distinguished  from  all  others  by  their  very 
peculiar  idiom,  originally  inhabited  the  region  of  Asia  intermediate  between 
the  countries  of  the  Indo-European  and  of  the  Egyptian  races  ;  having  as  its 
centre  the  region  watered  by  the  great  rivers  of  Mesopotamia.     Several  of  the 
nations  originally  constituting  this  group  have  become  extinct,  or  nearly  so ; 
and  the  Arabs,  which  originally  formed  but  one  subdivision  of  it,  have  now 
become  the   dominant  race,  not  only  throughout  the  ancient  domain  of  the 
Syro-Arabian  nations,  but  also  in  Northern  Africa.     In  the  opinion  of  Baron 
Larrey,  who  had  ample  opportunities  for  observation,  the  skulls  of  the  Arabian 
race  furnish,  at  present,  the  most  complete  type  of  the  human  head;  and  he 
considered  the  remainder  of  the  physical  frame  as  equally  distinguished  by 
its  superiority  to  that  of  other  races  of  men.     The  different  tribes  of  Arabs 
present  very  great  diversities  of  colour,  which  are  generally  found  to  coincide 
•with  variations  in  climate.     Thus  the  Shegya  Arabs,  and  others  living  on  the 
low  countries  bordering  on  the  Nile,  are  of  a  dark-brown  or  even  black  hue ; 
but  even  when  quite  jetty,  they  are  distinguished  from  the  Negro  races  by 
the  brightness  of  their  complexions,  by  the  length  and  straightness  of  their 
hair,  and  by  the  regularity  of  their  features.     The  same  may  be  said  of  the 
wandering  Arabs  of  Northern  Africa ;  but  the  influence  of  climate  and  cir- 
cumstances is  still  more  strongly  marked  in  some  of  the  tribes  long  settled  in 
that  region,  whose  descent  may  be  traced  to  a  distinct  branch  of  the  Syro- 
Arabian  stock,  namely,  the  Berber,  to  which  belong  the  Kabyles  of  Algiers 
and  Tunis,  the  Tuaryks  of  Sahara,  and  the  Guanches  or  ancient  population 
of  the  Canary  Isles.     Amongst  these   tribes,  whose  affinity  is  indisputably 
traceable  through  their  very  remarkable  language,  every  gradation   may  be 
seen,  from  the  intense  blackness  of  the  Negro  skin,  to  the  more  swarthy  hue 
of  the  inhabitants  of  the  South  of  Europe.     It  is  remarkable  that  some  of  the 
Tuaryk  inhabitants  of  particular  Oases  in  the  great  desert,  who  are  almost  as 
insulated  from    communication  with  other  races   as   are  the  inhabitants  of 
islands  in  a  wide  ocean,  have  hair  and  features   that  approach  those  of  the 
Negroes ;  although  they  speak  the  Berber  language  with   such  purity,  as  to 
forbid  the  idea  of  the  introduction  of  these  characters  by  an  intermixture  of 
races.     The  Jews,  who  are  the  only  remnants  now  existing  of  the  once  pow- 
erful Phoenician  tribe,  and  who  are  now  dispersed  through  nearly  every  coun- 
try on  the   face  of  the  earth,  present  a  similar  diversity ;  having  gradually 
assimilated  in  physical  characters  to  the  nations  among  which  they  have  so 
long  resided  (§  80). 

95.  The   affinity  of  the   Indo-European   nations,  now  spread  from  the 
mouth  of  the  Ganges   to  the  British  Islands  and  the  Northern  extremity  of 
Scandinavia,  is  in  like  manner  proved  by  the  cognate  character  of  their  lan- 
guages ;  in  spite  of  the  differences  in  colour  and  other  traits,  which  present 
themselves  among  the  inhabitants  of  that  vast  tract.     The  type  of  physical 
configuration,  however,  is  the  same ;  and  the  differences  of  colour  are  such, 
as   may  readily  be   traced  to   external  agencies.     Thus  among  the  Hindoo 
races  we  find  that  the  distinction  of  castes  (perpetuating  the  same  mode  of  life 
in  particular  families  from  generation  to  generation),  the  marked  differences 
of  climate  (as  between  the  mountainous  regions  of  Kashmir  and  Kafiristan, 
and  the  plains  bordering  the  great  rivers  of  India),  and  other  circumstances, 
are  accompanied,  as  in  the  case  of  the  Arabian  race,  with  diversities  in  phy- 
sical conformation,  which  are  now  established  as  belonging  to  different  sections 
of  the  people.     In  majjjf  instances,  the  origin  of  these  varieties  can  be  clearly 
traced  by  historical  evidence,  as  well  as  by  affinities  of  language  and  con- 
formation ;  and  it  cannot  be  questioned,  that  Hindoos  as  black  as  Negroes, 
others  of  a  copper-colour,  others  little  darker  than  the  inhabitants  of  Southern 
Europe,  and  others  of  fair  complexion  with  blue  eyes  and  auburn  or  even  red 


PRINCIPAL  BRANCHES  OF  THE  HUMAN  FAMILY.  93 

hair,  have  all  had  a  common  parentage;  some  having  become  darker,  and 
others  lighter  than  their  ancestors,  generally  in  accordance  with  changes  in 
their  residence  and  habits.  This  group  seems  to  have  been  early  divisible 
into  two  primary  branches  ;  the  northern  or  Median;  and  the  southern  or 
Indian.  Between  the  original  languages  of  these  races,  a  marked  resem- 
blance can  be  traced ;  and  the  traditions  of  both  races  point  to  contiguous 
regions  as  their  original  seat, — the  earliest  records  of  the  Persians  indicating 
that  they  migrated  westwards  from  a  spot  in  the  ancient  Bactria,  not  far  from 
Balkh,  to  the  westward  of  the  Indus ;  whilst  the  traditions  of  the  Brahmans 
refer  the  origin  of  the  Hindoos  to  the  north-western  part  of  the  country  lying 
between  the  Himalaya  and  the  Vindhya  mountains,  whence  they  afterwards 
moved  eastwards  and  southwards  into  the  Peninsula.  Both  these  races  ap- 
pear to  have  migrated  in  a  north-westerly  direction,  at  a  period  long  preceding 
our  earliest  knowledge  of  European  history  ;  for  the  European  languages  pre- 
sent indications  of  affinity  to  the  ancient  languages  of  both  Medians  and 
Indians.  The  classical  languages  of  Greece  and  Italy  appear  more  referrible 
to  the  Sanskrit  or  ancient  Indian,  than  to  the  Zend  or  ancient  Median ;  whilst, 
on  the  other  hand,  the  Germanic  languages  would  seem  to  have  originated 
rather  in  the  latter.  Of  all  the  extant  European  dialects,  the  Lettish  and 
Lithuanian  approach  most  nearly  to  the  ancient  type. 

a.  It  may  be  well  to  notice  here,  the  nature  of  the  evidence  on  which  statements  of  this 
kind  are  grounded.     The  extensive  and  profound  inquiries  which  have  been  in  progress 
for  many  years,  have  enabled  Philologists  to  distinguish,  usually  with  little  difficulty,  between 
the  intermixture  of  languages,  which  may  arise  from  the  intercourse  of  any  two  nations  that 
happen  to  be  connected  by  local  proximity,  commercial  intercourse,  &c.;  and  that  funda- 
mental correspondence,  which  indicates  original  affinity.     The  latter  is  to  be  sought  rather 
in  the  analogies  of  grammatical  structure,  and  in  the  laws  of  combination,  or  the  mechanism 
of  speech,  than  in  the  vocabulary;  and  it  sometimes  happens  that  a  relationship  may  thus 
be  traced  between  languages,  which  have  scarcely  a  single  word  in  common.     The  most 
satisfactory  evidence,  however,  is  derived  from  resemblance  in  those  parts  of  the  vocabu- 
lary, which  serve  to  represent  the  ideas  of  a  people  in  the  most  simple  state  of  existence ; — 
such  as  terms  expressive  of  family  relations;  names  for  the  most  striking  objects  of  the  visi- 
ble universe;  terms  distinguishing  different  parts  of  the  body;  nouns  of  number,  up  to  5,  10, 
or  20  ;  verbs  descriptive  of  the  most  common  sensations  and  bodily  acts,  such  as  seeing, 
hearing,  eating,  drinking,  and  sleeping.     As  no  nation  was  ever  found  destitute  of  similar 
expressions ;  and  as  we  know  by  the  observation  of  facts,  in  addition  to  abstract  probability, 
that  tribes  however  rude,  do  not  exchange  their  own  stock  of  primitive  words  for  those  of  a 
foreign  idiom ;  it  may  be  inferred  that  dialects,  which  correspond  in  those  parts  of  their 
vocabulary,  were  originally  one  speech,  or  the  language  of  one  people. 

b.  It  has  been  fully  demonstrated,  tha,t  both  these  indications  of  affinity  or  family  relation- 
ship exist  between  the  languages  of  the  several  races,  from  which  the  great  mass  of  the  popu- 
lation of  Europe  is  derived;  and,  further,  that  this  affinity  not  only  unites  them  with  each 
other,  but  connects  them  all  with  the  common  Eastern  stock. 

96.  The  second  primary  division  of  the  human  family,  according  to  the 
usual  arrangement,  is  that  commonly  termed  Mongolian.  The  real  Mon- 
goles,  however,  constitute  but  a  single  and  not  very  considerable  member  of 
the  group  of  nations  associated  under  this  designation ;  which  is,  therefore, 
by  no  means  an  appropriate  one.  The  original  seat  of  these  races  appears 
to  have  been  the  great  central  elevated  plain  of  Asia,  in  which  all  the  great 
rivers  of  that  continent  have  their  sources,  whatever  may  be  their  subsequent 
direction.  Taken  as  a  whole,  this  division  of  the  human  family  is  charac- 
terized by  the  pyramidal  form  of  the  skull,  and  by  a  xanthous  or  olive  com- 
plexion; but  these  characters  are  only  exhibited,  in  a  prominent  degree,  in 
the  more  typical  members  of  the  group,  and  may  become  so  greatly  modified 
as  to  cease  altogether  to  be  recognizable.  This  has  been  remarkably  the  case 
with  regard  to  the  Turkish  people,  now  so  extensively  distributed.  All  the 
most  learned  writers  on  Asiatic  history  are  agreed  in  opinion,  that  the  Turkish 


94  MUTUAL  RELATIONS  OF  THE  HUMAN  FAMILY. 

races  are  of  one  common  stock ;  although  at  present  they  vary  in  physical 
characters,  to  such  a  degree  that,  in  some,  the  original  type  has  been  alto- 
gether changed.  Those  which  still  inhabit  the  ancient  abodes  of  the  race, 
and  preserve  their  pastoral  nomadic  life,  present  the  physiognomy  and  gene- 
ral characteristics  which  appear  to  have  belonged  to  the  original  Turkomans ; 
and  these  are  decidedly  referrible  to  the  so-called  Mongolian  type.  Before 
the  Mohammedan  era,  however,  the  Western  Turks  or  Osmanlis  had  adopted 
more  settled  habits,  and  had  made  considerable  progress  in  civilization ;  and 
their  adoption  of  the  religion  of  Islam  incited  them  to  still  wider  extension, 
and  developed  that  spirit  of  conquest,  which,  during  the  middle  ages,  dis- 
played itself  with  such  remarkable  vigour.  The  branches  of  the  race,  which, 
from  their  long  settlement  in  Europe,  have  made  the  greatest  progress  in 
civilization,  now  exhibit  in  all  essential  particulars  the  physical  characters  of 
the  European  model;  and  these  are  particularly  apparent  in  the  conformation 
of  the  skull. — In  like  manner  we  find  that  the  Ugorian  division,  which  mi- 
grated towards  the  northwest  at  a  very  early  period,  planted  a  colony  in 
Europe,  which  still  tenants  the  Northern  Baltic  countries,  forming  the  races 
of  Fins  and  Lappes.  In  the  time  of  Tacitus,  the  Fins  were  as  savage  as  the 
Lappes ;  but  the  former,  during  the  succeeding  ages,  became  so  far  civilized, 
as  to  exchange  a  nomadic  life  for  one  of  agricultural  pursuits,  and  have  gra- 
dually assimilated  with  the  surrounding  people ;  whilst  the  Lappes,  like  the 
Siberian  tribes  of  the  same  race,  have  ever  since  continued  to  be  barbarous 
nomades,  and  have  undergone  no  elevation  in  physical  characters.  The  same 
division  gave  origin  to  the  Magyars  or  Hungarians ;  a  warlike  and  energetic 
people,  unlike  their  kindred  in  the  North ;  in  whom  a  long  abode  in  the  centre 
of  Europe  has,  in  like  manner,  developed  the  more  elevated  characters,  phy- 
sical and  mental,  of  the  European  nations.  The  nations  inhabiting  the  south- 
eastern portion  of  Asia,  also,  appear  to  have  had  their  origin  in  the  Mongolian 
or  Central  Asiatic  stock;  although  their  features  and  form  of  skull  by  no 
means  exhibit  its  characteristic  marks,  but  present  such  departures  from  it  as 
are  elsewhere  observable  in  races  that  are  making  advances  in  civilization. 
Even  the  great  peninsula  of  Hindostan  appears  to  have  been  peopled,  long 
previously  to  the  settlement  of  the  present  Hindoo  race,  by  tribes  of  the 
Central  Asiatic  stock,  so  distinguished  by  its  migratory  propensities;  and 
remains  of  these  aborigines  are  still  found  in  the  hilly  parts  of  Northern 
India,  in  the  Dekhan,  and  in  Ceylon,  constituting  numerous  tribes,  which  are 
now  for  the  most  part  isolated  from  each  other,  and  which  exhibit  very  dif- 
ferent degrees  of  civilization. 

97.  According  to  the  usual  mode  of  dividing  the  Human  family,  the  Ethi- 
opian or  Negro  stock  is  made  to  include  all  the  nations  of  Africa,  to  the 
southward  of  the  Atlas  range.  But  there  is  good  reason  for  separating  the 
Hottentots  and  Bushmen  as  a  distinct  race ;  and  for  restricting  the  designation 
of  Negroes  to  the  nations  inhabiting  the  region  southward  of  the  Great  Desert, 
as  far  as  the  Hottentot  country, — the  inhabitants  of  the  oases  of  the  desert 
itself  being  mostly,  as  already  pointed  out,  of  Syro-Arabian  origin,  although 
assimilating  closely  to  the  Negro  race  in  physical  characters.  The  nations 
thus  in  geographical  proximity  with  each  other,  are  found  to  have  sufficient 
affinities  of  language,  to  justify  the  belief  in  their  common  origin ;  and  they 
all  present,  in  a  more  or  less  evident  degree,  the  physical  peculiarities  of  the 
Negro  race.  But  these  are  far  from  constituting  a  sufficient  ground  for  regard- 
ing the  African  nations  as  a  distinct  race,  separated  from  all  other  families  of 
men  by  a  broad  and  definite  line  of  demarcation.  Our  idea  of  the  Negro 
character  is  principally  founded  upon  that  division  of  the  people  which  in- 
habits the  low  countries  of  the  Western  part  of  Central  Africa,  and  in  which 
the  Negro  peculiarities  are  most  strongly  marked.  There  are  very  few  nations 


PRINCIPAL  BRANCHES  OF  THE  HUMAN  FAMILY.  95 

which  present  in  a  high  degree  all  the  characters  that  are  commonly  regarded 
as  typical  of  the  Negro;  these  being  generally  distributed  among  different 
nations  in  various  ways;  and  being  combined,  in  each  instance,  with  more 
or  fewer  of  the  characters  belonging  to  the  European  or  Asiatic.  Thus  the 
race  of  Jolofs  near  the  Senegal,  and  the  Guber  in  the  interior  of  Sudan,  have 
woolly  hair  and  deep  black  complexions,  but  fine  forms  and  regular  features 
of  a  European  cast;  and  nearly  the  same  may  be  said  of  the  darkest  of  the 
Kafirs  of  Southern  Africa.  The  Bechuna  Kafirs  present  a  still  nearer  ap- 
proach to  the  European  type ;  the  complexion  being  of  a  light  brown,  the 
hair  often  not  woolly  but  merely  curled,  or  even  in  long  flowing  ringlets,  and 
the  figure  and  features  having  much  of  the  European  character.  The  nations 
of  the  northeast  of  Africa,  also,  present  similar  departures  Jfrom  the  typical 
characters  of  the  Negro. 

98.  There  is  no  group  which  presents  a  more  constant  correspondence 
between  external  conditions  and  physical  conformation,  than  that  composed 
of  the    African  nations.     As  we  find  the  complexion  becoming  gradually 
darker,  in  passing  from  northern  to  southern  Europe,  thence  to  North  Africa, 
thence  to  the  borders  of  the  Great  Desert,  and  thence  to  the  intertropical  re- 
gion where   alone  the  dullest  black  is  to  be  met  with, — so  do  we  find,  on 
passing  southwards  from  this,  that  the  hue  becomes  gradually  lighter  in  pro- 
portion as  we  proceed  further  from  the  equator,  until  we  meet  with  races 
of  comparatively  fair  complexions   among  the   nations   of  Southern   Africa. 
Even  in  the  intertropical  region,  high  elevations  of  the  surface  have  the  same 
effect,  as  we  have  seen  them  produce  elsewhere,  in  lightening  the  complexion. 
Thus,  the  high  parts  of  Senegambia,  where  the  temperature  is  moderate  and 
even  cool  at  times,  are  inhabited  by  Fulahs  of  a  light  copper  colour;  whilst 
the  nations  inhabiting  the  lower  regions  around  them,  are  of  true  Negro  Mack- 
ness;  and  nearly  on  the  same  parallel,  but  at  the  opposite  side  of  Africa,  are 
the  high  planes  of  Enarea  and  Kaffa,  where  the  inhabitants  aye  said  to  be 
fairer  than  the  natives  of  Southern  Europe.     Again,  those  races  which  have 
the  Negro  character  in  an  exaggerated  degree,  and  which  may  be  said  to  ap- 
proach to  deformity  in  persons, — the  ugliest  blacks,  with  depressed  forehead, 
flat  noses,  and  crooked  legs, — are  in  most  instances  inhabitants  of  low  coun- 
tries,  often  of  swampy  tracts  near  the  sea-coast,  where  many  of  them  have 
scarcely  any  other  means  of  subsistence  than  shell-fish  and  the  accidental  gifts 
of  the  sea.     Such  tribes  are  uniformly  in  the  lowest  stage  of  society,  being 
either  ferocious  savages,  or  stupid,  sensual,  and  indolent.     Such  are  most  of 
the  tribes  along  the  Slave  Coast.     On  the  other  hand,  wherever  we  hear  of 
a  Negro  state,  the  inhabitants  of  which  have  attained  any  considerable  degree 
of  improvement  in  their  social  condition,  we  constantly  find  that  their  phy- 
sical characters  deviate  considerably  from  the  strongly-marked  or  exaggerated 
type  of  the  Negro.     Such  are  the  Ashanti,  the  Sulima,  and  the  Dahomans  of 
Western  Africa;  also  the  Guber  of  Central  Sudan,  among  which  a  consider- 
able degree  of  civilization  has  long  existed,  which  are  perhaps  the  finest  race 
of  genuine  Negroes  on  the  whole  continent,  and  which  present  in  their  lan- 
guage distinct  traces  of  original  relationship  to  the  Syro-Arabian  nations,  not 
to  be  accounted  for  by  any  subsequent  intermixture  of  races. 

99.  The  highest  civilisation,  and  the  greatest  improvement  in  physical 
characters,  are  to  be  found  in  those  nations,  which  have  adopted  the  Moham- 
medan religion;  this  was  introduced,  three  or  four  centuries  since,  into  the 
eastern  portion  of  Central  Africa;  and  it  appears  that  the  same  people,  which 
were  then  existing  in  the  savage  condition  still  exhibited  by  the  pagan  nations 
further  south,  have  now  adopted  many  of  the  arts  and  institutions  of  civilized 
society,  subjecting  themselves  to  governments,  practising  agriculture,  and 
dwelling  in  towns  of  considerable  extent,  many  of  which  contain  10,000,  and 


96  MUTUAL  RELATIONS  OF  THE  HUMAN  FAMILY. 

some  even  30,000  inhabitants;  a  circumstance  which  implies  a  consider- 
able advancement  in  industry,  and  in  the  resources  of  subsistence.  This  last 
fact  affords  most  striking  evidence  of  the  improvability  of  the  Negro  races  ; 
and,  taken  in  connexion  with  the  many  instances  that  have  presented  them- 
selves, of  the  advance  of  individuals,  under  favourable  circumstances,  to  at 
least  the  average  degree  of  mental  development  among  the  European  nations, 
it  affords  clear  proof  that  the  line  of  demarcation,  which  has  been  supposed 
to  separate  them  intellectually  and  morally  from  the  races  that  have  attained 
the  greatest  elevation,  has  no  more  real  existence  than  that,  which  has  been 
supposed  to  be  justified  by  a  difference  in  physical  characters,  and  of  which 
the  fallacy  has  been  demonstrated. 

100.  The  Bushmen  or  Bojesmen  of  South  Africa  are  generally  regarded 
as  presenting  the  most  degraded  and  miserable  condition,  of  which  the  human 
race  is   capable:  and  they  have   been  supposed  to  present  resemblances  in 
physical  characters  to  the  higher  Quadrumana.     Yet  there  is  distinct  evidence, 
that  this  degraded  race  is  but  a  branch  or  subdivision  of  the  once  extensive 
nation  of  Hottentots;  and  that  its  present  condition  is  in  great  part  due  to  the 
hardships,  to  which  it  has  been  subjected  in  consequence  of  European  colo- 
nization.    This  race  differs  from  all  other  South  African  nations,  both  in  lan- 
guage and  in  physical  conformation.    The  language  cannot  be  shown  to  possess 
affinities  with  those  of  any  other  stock;  but  in  bodily  structure  there  is  a  re- 
markable admixture  of  the  characters  of  the  Mongolian  with  those  of  the  Ne- 
gro.    Thus  the  face  presents  the  very  wide  and  high  cheek-bones,  with  the 
oblique  eyes  and  flat  nose,  of  the  Northern  Asiatics ;  at  the  same  time  that,  in 
the  somewhat  prominent  muzzle  and  thick  lips,  it  resembles  the  countenance 
of  the  Negro.     The  complexion  is  of  a  tawny  buff  or  fawn  colour,  like  that 
of  the  Negroes  diluted  with  the  olive  of  the  Mongoles.     The  hair  is  woolly 
like  that  of  the  Negroes,  but  it  grows  in  small  tufts,  scattered  over  the  surface 
of  the  scalp,  instead  of  covering  it  uniformly,  resembling  in  its  comparative 
scantiness  that  of  the  Northern  Asiatics.     It  is  most  interesting  to  observe  this 
remarkable  resemblance  in  physical  characters,  between  the  Hottentots  and 
the  Mongolian  races ;  in  connexion  with  the  similarity  that  exists  between  the 
circumstances  under  which  they  respectively  live.     No  two  countries  can  be 
more  similar,  than  the  vast  steppes  of  Central  Asia,  and  the  karroos  of  South- 
ern Africa.     And  the   inhabitants  of  each  were  nomadic  races,  wandering 
through  deserts  remarkable  for  the  wide  expansion  of  their  surface,  their  scanty 
herbage,  and  the  dryness  of  their  atmosphere,  and  feeding  upon  the  milk  and 
flesh  of  their  horses  and  cattle.     Of  the  original  pastoral  Hottentots,  however, 
very  few  now  remain.     They  have  been  gradually  driven,  by  the  encroach- 
ments of  European  colonists  and  by  internal  wars  with  each  other,  to  seek 
refuge  among  the  inaccessible  rocks  and  deserts  of  the  interior ;  and  they  have 
thus  been  converted  from  a  mild  unenterprising  race  of  shepherds,  into  wander- 
ing hordes  of  fierce,  suspicious,  and  vindictive  savages,  treated  as  wild  beasts 
by  their  fellow-men,  until  they  become  really  assimilated  to  wild  beasts  in  their 
habits  and  dispositions.     This  transformation  has  taken  place  under  the  ob- 
servation of  eye-witnesses,  in  the  Koranas,  a  tribe  of  Hottentots  well  known 
to  have  been  previously  the  most  advanced  in  all  the  improvements  which 
belong  to  pastoral  life.     Having  been  plundered  by  their  neighbours  and  driven 
out  into  the  wilderness  to  subsist  upon  fruits,  they  have  adopted  the  habits  of 
the  Bushmen,  and  have  become  assimilated  in  every  essential  particular  to 
that  miserable  tribe. 

101.  The  American  nations,  taken  collectively,  form  a  group  which  ap- 
pears to  have  existed  as  a  separate  family  of  nations  from  a  very  early  period 
in  the  world's  history.     They  do  not  form,  however,  so  distinct  a  variety,  in 
regard  to  physical  characters,  as  some  anatomists  have  endeavoured  to  prove ; 


PRINCIPAL  BRANCHES  OF  THE  HUMAN  FAMILY.  97 

for,  although  certain  peculiarities  have  been  stated  to  exist  in  the  skulls  of  the 
aboriginal  Americans,  yet  it  is  found,  on  a  more  extensive  examination,  that 
these  peculiarities  are  very  limited  in  their  extent,— the  several  nations  spread 
over  this  vast  continent  differing  from  each  other  in  physical  peculiarities,  as 
much  as  they  do  from  those  of  the  Old  World,  so  that  no  typical  form  can  be 
made  out  among  them.  In  regard  to  complexion,  again,  it  may  be  remarked, 
that  although  the  native  Americans  have  been  commonly  characterized  as 
"  red  men,"  they  are  by  no  means  invariably  of  a  red  or  coppery  hue,  some 
being  as  fair  as  many  European  nations,  others  being  yellow  or  brown,  and 
others  nearly,  if  not  quite,  as  black  as  the  Negroes  of  Africa ;  whilst,  on  the 
other  hand,  there  are  tribes  equally  red,  and  perhaps  more  deserving  that  epi- 
thet in  Africa  and  Polynesia. — In  spite  of  all  this  diversity  of  conformation, 
it  is  believed  that  the  structure  of  their  languages  affords  a  decided  and 
clearly-marked  evidence  of  relationship  between  them.  The  words,  and  even 
the  roots,  may  differ  entirely  in  the  different  groups  of  American  nations ; 
but  there  is  a  remarkable  similarity  in  grammatical  construction  amongst  them 
all,  which  is  of  a  kind  not  only  to  demonstrate  their  mutual  affinity,  but  to 
separate  them  completely  from  all  known  languages  of  the  old  continent. 
Notwithstanding  also  their  diversities  in  mode  of  life,  there  are  peculiarities 
of  mental  character,  as  well  as  a  number  of  ideas  and  customs  derived  from 
tradition,  which  seem  to  be  common  to  them  all,  and  which  for  the  most  part 
indicate  a  former  elevation  in  the  scale  of  civilization,  that  has  left  its  traces 
among  them  even  in  their  present  degraded  condition,  and  that  still  distin- 
guishes them  from  the  sensual,  volatile,  and  almost  animalized  savages,  that 
are  to  be  met  with  in  many  parts  of  the  Old  Continent. — The  Esquimaux 
constitute  an  exception  to  all  general  accounts  of  the  physical  characters  of 
the  American  nations ;  for  in  the  configuration  of  their  skulls,  in  their  com- 
plexion, and  in  their  general  physiognomy,  they  conform  to  the  Mongolian 
type,  even  presenting  it  in  an  exaggerated  degree.  Their  wide  extension 
along  the  whole  northern  coast  of  America,  and  the  near  proximity  of  this 
coast  to  Kamschatka,  certainly  lend  weight  to  the  idea,  that  they  derive  their 
origin  from  the  Northern  Asiatic  stock ;  but,  on  the  other  hand,  they  have  a 
marked  affinity,  in  regard  to  language,  to  the  other  American  nations.  The 
Athapascan  Indians,  various  tribes  of  which  inhabit  the  country  south  of  the 
Esquimaux  country,  seem  intermediate  in  physical  characters,  as  they  are  in 
geographical  position,  between  the  Esquimaux  and  the  ordinary  Americans. 
They  have  a  tradition  which  seems  to  indicate,  that  they  are  derived  from  the 
North-Eastern  Asiatics,  with  whom  they  have  many  points  of  accordance  in 
dress  and  manners. 

102.  It  now  remains  for  us  to  notice  the  Oceanic  races,  which  inhabit  the 
vast  series  of  islands  scattered  through  the  great  ocean,  that  stretches  from 
Madagascar  to  Easter  Island.  There  is  no  part  of  the  world,  which  affords  a 
greater  variety  of  local  conditions  than  this,  or  which  more  evidently  exhibits 
the  effects  of  physical  agencies  on  the  organization  of  the  human  body. 
Moreover,  it  affords  a  case  for  the  recognition  of  affinities  by  means  of  lan- 
guage, that  possesses  unusual  stability ;  since  the  insulated  position  of  the 
various  tribes,  that  people  the  remote  spots  of  this  extensive  tract,  prevents 
them  from  exercising  that  influence  upon  each  others'  forms  of  speech,  which 
is  to  be  observed  in  the  case  of  nations  united  by  local  proximity  or  by  fre- 
quent intercourse.  Tried  by  this  test,  it  is  found  that  the  different  groups  of 
people,  inhabiting  the  greater  part  of  these  insular  tracts,  are  more  nearly  con- 
nected together,  although  so  widely  scattered,  and  so  diverse  in  physical 
characters,  than  most  of  the  families  of  men,  occupying  continuous  tracts  of 
land  on  the  great  continents  of  the  globe.  The  inhabitants  of  Oceanica  seem 
divisible  into  three  groups,  which  are  probably  to  be  regarded  as  having  con- 
9 


98  MUTUAL  RELATIONS  OF  THE  HUMAN  FAMILY. 

stituted  distinct  races  from  a  very  early  period ;  these  are  the  Malayo-Poly- 
nesian  race,  the  Pelagian  Negroes  (commonly  termed  Papuas),  and  the  Alforas 
or  Alfourous. 

103.  The  Malay ^-Polynesian  group  is  by  far  the  most  extensive  of  the 
three,  and  comprehends  the  inhabitants  of  the  greater  part  of  the  Indian  and 
Polynesian  Archipelagoes,  with  the  peninsula  of  Malacca  (which  is  the  cen- 
tre of  the  Malays  proper),  and  the  inhabitants  of  Madagascar.     These  are  all 
closely  united  by  affinities  of  language.     The  proper  Malays  bear  a  strong 
general  resemblance  to  the  Mongolian  races,  and  this  resemblance  is  shared, 
in  a  greater  or  less  degree,  by  most  of  the  inhabitants  of  the  Indian  Archi- 
pelago.    They  are  of  a  darker  complexion,  as  might  be  expected  from  their 
proximity  to  the  equator ;  but  in  this  complexion,  yellow  is  still  a  large  in- 
gredient.    The    Polynesian  branch   of    the   group  presents    a  much  wider 
diversity ;  and  if  it  were  not  for  the  community  of  language,  it  might  be 
thought  to  consist  of  several  races,  as  distinct  from  each  other  as  from  the 
Malayan  branch.     Thus   the   Tahitians  and  Marquesans  are  tall  and  well- 
made;  their  figures  combine  grace  and  vigour:  their  skulls  are  usually  re- 
markably symmetrical ;  and  their  physiognomy  presents  much  of  the  Euro- 
pean cast,  with  a  very  slight  admixture  of  the  features  of  the  Negro.     The 
complexion,  especially  in  the  females  of  the  higher  classes,  who  are  sheltered 
from  the  wind  and  sun,  is  of  a  clear  olive  or  brunette,  such  as  is  common 
among  the  natives  of  Central  and  Southern  Europe;  and  the  hair,  though 
generally  black,  is  sometimes  brown  or  auburn,  or  even  red  or  flaxen.  Among 
other  tribes,  as  the  New  Zealanders,  and  the  Tonga,  and  Friendly  Islanders, 
there  are  greater  diversities  of  conformation  and  hue ;  some  being  finely  pro- 
portioned and  vigorous,  others  comparatively  small  and  feeble ;  some  being 
of  a  copper-brown  colour,  others  nearly  black,  others  olive,  and  others  almost 
white.     In  fact,  if  we  once  admit  a  strongly-marked  difference  in  complexion, 
features,  hair,  and  general  configuration,  as  establishing  a  claim  to  original 
distinctness  of  origin,  we  must  admit  the  application  of  this    hypothesis  to 
almost  every  group  of  islands  in  the  Pacific ; — an  idea  of  which  the  essential 
community  of  language  seems  to  afford  a  sufficient  refutation.     Among  the 
inhabitants  of  Madagascar,  too,  all  of  which  speak  dialects  of  the  same  lan- 
guage, some  bear  a  strong  resemblance  to  the  Malayan  type,  whilst  others 
present  approaches  to  that  of  the  Negro. 

104.  The  Pelagian-Negro  races  must  be  regarded  as  a  group  altogether 
distinct  from  the  preceding ;  having  a  marked  diversity  of  language ;  and 
presenting  more  decidedly  than  any  of  the  Malay o-Polynesians,  the  characters 
of  the  Negro  type.     They  form  the  predominating  population  of  New  Bri- 
tain, New  Ireland,  the  Louisiade  and  Solomon  Isles,  of  several  of  the  New 
Hebrides,  and  of  New  Caledonia;  and  they  seem  to  extend  westwards  into 
the  mountainous  interior  of  the  Malayan  Peninsula,  and  into  the  Andaman 
Islands,  in  the  Bay  of  Bengal.     The  Tasmanians,  or  aborigines  of  Van  Die- 
man's  Land,  which   are  now  almost  completely  exterminated,  undoubtedly 
belonged  to  this  group.     Very  little  is  known  of  them,  except  through  the 
reports  of  the  people  of  Malayo-Polynesian  race  inhabiting  the  same  islands  ; 
but  it  appears  that,  generally  speaking,  they  have  a  very  inferior  physical  de- 
velopment, and  lead  a  savage  and  degraded  life.    There  is  considerable  diversity 
of  physical  characters  among  them  ;  some  approximating  closely  in  hair,  com- 
plexion, and  features,  to   the   Guinea-Coast  Negroes  ;  whilst  others  are  of 
yellower  tint,  straight  hair,  and  better  general  development.     The  Papuans, 
who  inhabit  the  northern  coast  of  New-Guinea,  and  some  adjacent  islands, 
and  who  are  remarkable  for  their  large  bushy  masses  of  half-woolly  hair,  have 
been  supposed  to  constitute  a  distinct  race  ;  but  there  is  little  doubt  that  they 
are  of  hybrid  descent,  between  the  Malays  and  the  Pelagian  Negroes. 


ON  ORGANIZED  STRUCTURES  IN  GENERAL.  99 

105.  Still  less  is  known  of  the  Mfourous,  or  JLlforian  race,  which  are 
considered  by  some  to  be  the  earliest  inhabitants  of  the  greater  part  of  the 
Malayan  Archipelago,  and  to  have  been  supplanted  by  the  more  powerful  peo- 
ple of  the  two  preceding  races,  who  have  either  extirpated  them  altogether, 
or  have  driven  them  from  the  coasts  into  the  mountainous  and  desert  parts  of 
the  interior.  They  are  yet  to  be  found  in  the  central  parts  of  the  Moluccas 
and  Philippines ;  and  they  seem  to  occupy  most  of  the  interior  and  southern 
portion  of  New  Guinea,  where  they  are  termed  Endamenes.  They  are  of 
very  dark  complexion ;  but  their  hair,  though  black  and  thick,  is  lank.  They 
have  a  peculiar  repulsive  physiognomy ;  the  nose  is  flattened,  so  as  to  give 
the  nostrils  an  almost  transverse  position;  the  cheek-bones  project;  the  eyes 
are  large,  the  teeth  prominent,  the  lips  thick,  and  the  mouth  wide.  The  limbs 
are  long,  slender  and  misshapen.  From  the  close  resemblance  in  physical 
characters,  between  the  Endamenes  of  New  Guinea,  and  the  aborigines  of 
New  Holland,  and  from  the  proximity  between  the  adjacent  coasts  of  these 
two  large  islands,  it  may  be  surmised  that  the  latter  belong  to  the  Alforian 
race;  but  too  little  is  known  of  the  language  of  either,  to  give  this  inference 
a  sufficient  stability.  In  the  degradation  of  their  condition  and  manner  of  life 
the  savages  of  New  Holland  fully  equal  the  Bushmen  of  South  Africa  ;  and 
it  is  scarcely  possible  to  imagine  human  beings,  existing  in  a  condition  more 
nearly  resembling  that  of  brutes.  But  there  is  reason  to  believe,  that  the 
tribes  in  closest  contact  with  European  settlers  are  more  miserable  and  savage 
than  those  of  the  interior ;  and  even  with  respect  to  these,  increasing  acquaint- 
ance with  their  language,  and  a  consequent  improved  insight  into  their  modes 
of  thought,  tend  to  raise  the  very  low  estimate  which  had  been  formed  and 
long  maintained,  in  regard  to  their  extreme  mental  degradation.  The  latest 
and  most  authentic  statements  enable  us  to  recognize  among  them  the  same 
principles  of  a  moral  and  intellectual  nature,  which,  in  more  cultivated  tribes, 
constitute  the  highest  endowments  of  humanity,  and  thus  to  show  that  they 
are  not  separated,  by  any  impassable  barrier,  from  the  most  civilized  and  cul- 
tivated nations  of  the  globe. 


CHAPTER     III. 

OF    THE    ELEMENTARY    PARTS    OF    THE    HUMAN    FABRIC. 

1.  On  Organized  Structures  in  General. 

106.  THE  Human  body,  in  common  with  the  bodies  of  all  the  higher  Ani- 
mals, is  composed  of  an  immense  number  of  parts,  whose  structure  and 
whose  actions  are  alike  dissimilar  ;  but  which  are  yet  so  arranged,  as  to  make 
up  a  fabric  distinguished  by  its  perfect  adaptation  to  a  great  variety  of  pur- 
poses, whilst  their  actions,  though  in  a  great  degree  independent  of  each  other, 
concur  in  effecting  one  common  object, — the  maintenance  of  the  integrity  of 
the  entire  organism.  'In  the  lowest  and  simplest  forms  of  living  being,  such 
as  we  meet  with  among  the  humblest  Cellular  Plants,  we  find  a  single  cell 
making  up  the  whole  fabric.  This  cell  grows  from  its  germ,  absorbs  and  as- 
similates nutriment,  converts  a  part  of  this  into  the  substance  of  its  own  cell- 
wall,  secretes  another  portion  into  its  cavity,  and  produces  from  a  third  the 
reproductive  germs  that  are  to  continue  the  race ;  and  having  reached  its  own 


100  OF  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 

term  of  life,  and  completed  the  preparation  of  these  germs,  it  bursts  and  sets 
them  free, — every  one  of  these  being  capable,  in  its  turn,  of  going  through 
the  same  set  of  operations.  In  the  highest  forms  of  Vegetable  life,  we  find 
but  a  multiplication  of  similar  cells ;  amongst  which  these  operations  are  dis- 
tributed, as  it  were,  by  a  division  of  labour;  so  that,  by  the  concurrent  labours 
of  all,  a  more  complete  and  permanent  effect  may  be  produced.  If  we  ana- 
lyze the  structure  of  a  forest  tree,  for  example,  we  find  that  all  the  soft  and 
growing  parts  are  composed  of  similar  cells ;  whose  office  it  is,  to  absorb  and 
prepare  the  nutriment,  which  is  afterwards  to  be  applied  to  the  extension  of 
the  solid  internal  skeleton  of  the  trunk  and  branches.  This  latter  part  is  not 
concerned  in  the  functions  of  vegetation,  in  any  other  way  than  as  supporting 
and  connecting  the  different  groups  of  cells,  which  form  the  operative  part  of 
the  fabric;  and  it  is  composed  of  two  forms  of  tissue, — woody-fibre,  and  vas- 
cular tissue, — each  of  which  may  be  regarded  as  originating  in  the  metamor- 
phosis of  cells  (§  120). 

107.  At  the  extremities  of  the  roots  of  all  the  more  perfect  Plants,  we  find 
a  set  of  soft  cells,  making  up  those  succulent  bodies  which  are  known  as  the 
spongioles  ;  these  are  specially  destined  to  perform  the  Absorption  of  nutri- 
tious fluid.  This  fluid,  being  conveyed  by  the  vessels  of  the  stem  and  branches 
to  the  leaves,  is  there  subjected  to  the  action  of  the  cells  which  make  up  the 
parenchyma  of  those  organs.     The  crude  watery  ascending  sap  is  thus  con- 
verted, by  a  variety  of  chemical   and  vital  operations,  into  the  thick  glutin- 
ous latex;  which,  like  the  blood  of  animals,  contains  the  materials  for  the 
production  of  new  tissue,  and  also  the  elements  of  the  various   secretions. 
This  process  of  conversion  includes  the  Exhalation  of  superfluous  liquid; 
and  also  that  interchange  of  gaseous  ingredients  between  the  sap  and  the  air, 
which  may  be  termed  Aeration  ;  but  it  involves,  beside  these  obvious  chemi- 
cal alterations,  a  new  molecular  arrangement  of  the  particles  of  the  sap,  by 
which  a  variety  of  new  products  are  generated, — some  of  them  possessing 
such  a  tendency  to  pass  into  the  form  of  solid  organized  tissue,  as  to  present 
a  sort  of  sketch  of  this,  by  a  process  of  coagulation,  when  withdrawn  from 
the  living  vessels.     To   this  peculiar  converting  process,  which  is  such  an 
important  step  towards  the  production  of  perfect  living  tissue  from  the  crude 
aliments,  the  term  Assimilation  is  applied.     As  the  elaborated  sap  or  latex 
descends  in  its   proper  vessels  through  the  stem,  it  yields  up  to  the  growing 
parts  the  nutrient  materials  they  respectively  require.     These  growing  parts 
may  be   either  the  ordinary  tissues,  of  which  the  chief  part  of  the  fabric  is 
composed,  and  which  are  destined  to  a  comparative  permanency  of  duration ; 
and  in  the  growth  and  extension  of  these,  the  process  of  Nutrition  is  com- 
monly regarded  as  consisting.     On  the  other  hand,  certain  groups  of  cells 
have  for  their  office  the  separation  of  peculiar  products  from  the  sap,  such  as 
oil  (fixed  or  essential),  starch,  resin,  &c. ;  which  they  store  up   against  the 
time  when  they  may  be  demanded  ;  and  these  are  said  to  perform  the  act  of 
Secretion.     In  both  cases,  however,  the  act  is  essentially  the  same  ;  for  the 
process  of  Secretion,  like  that  of  Nutrition,  consists  in  the  growth  of  a  cellular 
tissue,  and  the  difference  consists  only  in  the  destination  of  the  contents  of  the 
cells  ;  which,  in  the  one  case,  are  adapted  merely  to  give  firmness  and  solidity 
to  their  walls ;  whilst,  in  the  other,  they  are  set  apart  for  some  other  purpose, 
to  be  given  up  again  when  required. 

108.  It  is  very  important  to  remark,  in  regard  to  all  the  cells  thus  actively 
concerned  in  the  Vegetative  functions,  by  which  the  development  and  exten- 
sion of  the  permanent  fabric  is  provided  for,  that  they  have  but  a  very  transi- 
tory life  as  individuals.    The  Absorbent  cells  at  the  extremities  of  the  rootlets 
are  continually  being  renewed  ;  some  of  the  old  ones   dying  and  decaying 
away,  whilst  others  are  converted  into  the  solid  texture  of  the  root,  and  thus 


ON  ORGANIZED  STRUCTURES  IN  GENERAL.  101 

contribute  to  its  progressive  elongation.  Of  the  transitory  duration  of  the 
Assimilating  cells,  we  have  an  obvious  proof  in  the  "fall  of  the  leaf;"  which 
takes  place  at  intervals  (alike  in  evergreen  and  deciduous  species),  to  be  fol- 
lowed by  the  production  of  a  new  set  of  cells,  having  similar  functions.  And 
the  Secreting  cells  have  usually  a  like  transitory  duration;  being  destined  to 
give  up  their  contents  by  the  rupture  or  liquefaction  of  their  walls,  whenever 
called  upon  to  do  so,  by  the  demand  set  up  in  the  growing  parts  of  their 
neighbourhood,  for  the  peculiar  products  they  have  set  apart. 

109.  Not  only  are  the  proper  organic  functions  of  all  Plants  thus  dependent 
upon  the  agency  of  cells  ;  but  their  Reproduction  is  likewise.     In  the  lowest 
tribes  of  the  Cryptogamia,  where  each  cell  is  an  independent  individual,  every 
one  has  the  power  of  preparing  within  itself  the  reproductive  germs,  from 
which  new  generations  may  arise.     In  the  higher  tribes,  on  the  other  hand, 
the  general  principle  of  the  division  of  labour,  which  separates  the  absorbing, 
assimilating  and  secreting  cells,  involves  also  the  setting  apart  of  a  distinct  set 
of  cells  for  the  preparation  of  the  reproductive  germs  ;  these  cells  are  known 
in  the  Cryptogamia  as  spores,  and  in  the  Phanerogamia  as  pollen-grains.    In 
the  higher  Plants  we  find  a  complex  apparatus  superadded  ;  for  the  purpose 
of  aiding  the  early  development  of  these  germs,  by  supplying  them  with  nu- 
triment previously  elaborated   by  the  parent;  yet  still  this  operation  is  of  a 
purely  accessory  kind,  and  the  essential  part  of  the  process  remains  the  same. 

110.  Now  we  shall  find  that,  although  the  fabric  of  Animals  appears  to  be 
formed  on  a  plan  entirely  different  from  that  of  Plants,  and  although  the  ob- 
jects to  be  attained  are  so   dissimilar,  there  is  a  much  greater  accordance 
amongst  their  elementary  parts,  than  might  have  been  anticipated.  The  starting- 
point  of  both  is  the  same  ;  for  the  embryo  of  the  Animal,  up  to  a  certain  grade 
of  its  development,  consists,  like  that  of  the  Plant,  of  nothing  else  than  an  aggre- 
gation of  cells  (Plate  I.,  Fig.  15).  And  amongst  the  lowest  tribes  of  animals,  as 
well  as  among  certain  of  the  highest  tribes  that  retain  many  embryonic  peculi- 
arities, even  in  the  adult  condition,  (such  as  the  curious  Amphioxus  or  Lancelot,) 
we  find  a  great  proportion  of  the  complete  fabric  to  be  possessed  of  a  similar 
constitution.     In  most  of  the  higher  animals,  however,  we  find  that  a  large 
proportion  of  the  fabric  consists  of  tissues  in  which  no  distinct  trace  of  a  cel- 
lular origin  is  apparent ;  and  it  has  been  only  since  improved  powers  of  ob- 
servation have  been  brought  to  bear  upon  their  analysis,  and  more  especially 
since  they  have  been  examined,  not  only  in  their  complete  state,  but  in  the 
course  of  their  development,  that  they  have  been  reduced  to  the  same  category 
with  the  tissues  of  Plants  and  of  the  lower  Animals.     Other  tissues,  which 
are  peculiar  to  Animals,  cannot  be  referred  to  the  same  origin ;  but  these  will 
be  found  to  have  a  grade  of  organization  even  lower  than  that  of  simple  iso- 
lated cells,  and  to  be  referrible  to  the  solidification  of  the  plastic  or  organizable 
fluid  prepared  by  the  assimilating  cells,  and  set  free  by  their  rupture.     We 
shall  find,  however,  that  (as  in  Plants)  all  the  tissues  most  actively  concerned 
in  the  Vital  operations,  retain  their  original  cellular  form ;  and  we  shall  be 
able  to  refer  to  distinct  groups  of  cells  in  the  bodies  of  Animals,  not  merely 
the  functions  of  Absorption,  Assimilation,  Respiration,  Secretion,  and  Repro- 
duction, which  are  common  to  them  with  Plants,  but  also  those  of  Muscular 
(Contraction,  and  Nervous  Action,  which  they  alone  perform.     Before  procee^^ 
ing  to  this  investigation,  however,  it  will  be  desirable  to  examine  into  the  na- 
ture of  the  original  components  at  the  expense  of  which  the  Animal  fabric 
is  built  up.  Our  knowledge  of  these  is  principally  derived  from  the  researches 
which  have  been  made  into  their  character  in  Man  and  the  higher  Animals; 
but  there  can  be  little  doubt  that  they  are  common,  with  trifling  modifications, 
perhaps,  to  the  entire  kingdom. 

9* 


102  ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 

2.  On  the  Original  Components  of  the  Animal  Fabric. 

111.  Putting  aside,  for  the  present,  the  inorganic  or  mineral  matters  which 
enter  into  the  composition  of  the  Animal  body,  and  which  are  left  in  the  form 
of  an  ash,  when  the  organic  compounds  are  decomposed  and  dissipated  by 
heat,  we  shall  confine  our  attention  to  the  peculiar  characters  of  the  latter. 
As  already  stated  (§  4),  the  organized  tissues  of  Plants  are  found,  when  en- 
tirely freed  from  the  contents  of  their  cells,  to  have  a  very  uniform  composi- 
tion; being  entirely  made  up  of  Carbon  united  with  the  elements  of  Water  in 
a  very  simple  proportion, — that  of  8  of  the  former  to  7  of  each  of  the  latter; 
and  this  simplicity  in  their  chemical  character  partly  accounts  for  their  com- 
parative durability.  There  are  various  compounds  found  iii  the  cells  of  Plants, 
and  elaborated  by  them  for  the  purpose  of  affording  food  to  Animals,  which 
do  not  undergo  organization,  so  long  as  they  are  contained  in  the  Vegetable 
fabric;   but  these  very  products,  when  transferred  to  the  bodies  of  Animals, 
form  the  components  of  their  solid  tissues.  These  substances  are  distinguished 
by  the  presence  of  Azote  or  Nitrogen,  in  considerable  amount;  and  also  by  the 
large  number  of  atoms  of  the  four  components,  which  are  united  in  each  of 
them, — giving  them  a  much  more  complex  composition,  and  a  much  greater 
tendency  to  decay,  this  being  brought  about  by  the  disposition  of  the  compo- 
nents to  enter  into  new  compounds  of  a  simpler  and  more  permanent  nature. 
A  considerable  variety  of  such  substances  exists  in  the  different  parts  of  the 
Human  body  ;  but  the  nature  and  composition  of  these  may  be  belter  studied, 
when  their  structure  and  actions  are  being  described;  and  at  present  we  shall 
confine  ourselves  to  the  fundamental  or  original  components,  of  which  all  the 
others  may  be  regarded  as  modifications. 

112.  When  we  examine  the  Egg  of  an  Oviparous  animal,  we  find  that, 
putting  aside  the  fatty  matter  of  the  yolk  (which  is  destined,  not  to  be  con- 
verted into  tissue,  but  to  be  stored  up  in  cells),  the  sole  organic  constituent  is 
that  which  is  known  to  Chemists  as  Albumen.     By  the  wonderful  processes 
of  chemical  and  vital  transformation,  which  take  place  during  the  period  of 
incubation,  and  which  are  effected  by  the  germ-cell  and  its  descendants,  this 
Albumen  is  metamorphosed  into  nerve,  muscle,  tendon,  ligament,  membrane, 
areolar  tissue,  horny  substance,  feathers,  the  organic  basis  of  bone,  &c.     The 
same  metamorphosis  is  continually  taking  place  in  the  adult  animal;  for  every 
substance  of  similar  composition,  that  is  employed  as  food,  is  reduced  to  the 
form  of  Albumen  in  the  digestive  process;   so  that  this  becomes  the  essential 
constituent  of  whatever  fluid  is  absorbed  for  the  nutrition  of  the  tissues.     It 
is  true  that  Gelatine,  taken  in  as  food,  may  be  absorbed  and  carried  into  the 
current  of  the  circulation  ;  but  there  is  little   doubt,  that  it  is   incapable  of 
being  applied  to  the  reconstruction  of  any  but  the  gelatinous  tissues  ;  and  in 
these  it  exists  in  the  very  lowest  form  of  organization,  if  organization  it  can 
be  called.     Moreover,  as  it  is  clear,  from  what  has  been  just  stated,  that  the 
gelatinous  tissues  may  be  formed  at  the  expense  of  Albumen,  we  are  justified 
in  regarding  the  latter  substance  as  the  common  pabulum  for  all.    Hence  Albu- 
men seems  to  hold  very  much  the  same  position  in  the  Animal  economy,  with 
Gum  in  the  Vegetable. 

^113.  The  properties  of  Albumen  may  be  studied  in  the  White  of  Egg,  or 
in  the  Serum  of  Blood ;  from  both  of  which  situations  it  may  be  obtained  in 
a  pure  state  by  very  simple  means.  In  the  Animal  Fluids  it  exists  in  a  so- 
luble state ;  and  even  when  it  has  been  dried  (at  a  temperature  of  126°),  it 
is  readily  dissolved  again  in  water,  forming  a  glairy,  colourless,  and  nearly 
tasteless  fluid.  In  this  condition  it  is  always  combined  with  a  small  quan- 
tity of  free  soda;  to  the  separation  of  which  (whether  by  the  agency  of  heat 
or  acids),  its  coagulation  is  thought  by  many  Chemists  to  be  due.  On  this 


COMPONENTS  OF  THE  ANIMAL  FABRIC.— ALBUMEN. 


103 


view,  pure  Albumen  is  not  soluble  in  water ;  its  solution  being  only  accom- 
plished by  union  with  an  alkali.— When  dissolved  in  water,  it  coagulates 
at  158°;  a  very  dilute  solution,  however,  does  not  become  turbid  until  it  is 
boiled.  When  the  coagulation  of  Albumen  takes  place  rapidly,  a  coherent 
mass  is  formed,  which  shows  no  trace  whatever  of  organization ;  but,  when 
the  process  is  more  gradual,  minute  granules  present  themselves,  which  do 
not,  however,  exhibit  any  tendency  towards  a  higher  form  of  structure.  It  is 
thrown  down  from  its  solution,  in  a  coagulated  state,  by  Alcohol,  Creosote, 
and  by  most  Acids  (particularly  nitric)  with  the  exception  of  the  acetic. 
These  precipitates  are  definite  compounds  of  the  Acids  with  the  Albumen, 
which  here  acts  the  part  of  a  base.  On  the  other  hand,  coagulated  Albumen 
dissolves  in  caustic  Alkalies,  and  neutralizes  them  ;  so  that  it  must  here  act 
as  an  acid.  A  solution  of  Albumen  in  water  is  precipitated  by  acetate  of  lead, 
and  by  many  other  metallic  solutions:  and  insoluble  compounds  are  formed, 
of  which  one — the  albuminate  of  the  chloride  of  mercury — is  of  much  interest, 
as  being  that  which  is  produced  by  the  mixture  of  a  solution  of  albumen  with 
one  of  corrosive  sublimate.  Albumen,  both  in  its  soluble  and  insoluble  state, 
always  contains  a  small  amount  of  Sulphur,  which  blackens  metallic  silver ; 
and  also  a  minute  quantity  of  Phosphorus.  Soluble  albumen  dissolves  Phos- 
phate of  Lime ;  and  about  two  per  cent,  of  this  salt  may  be  separated  from  it 
in  its  coagulated  state. 

114.  So  long  as  Albumen  remains  in  the  state  regarded  by  Chemists  as 
characteristic  of  it,  no  tendency  to  become  organized  can  be  discerned  in  it ; 
but  subsequently  to  its  introduction  into  the  living  Animal  body,  it  undergoes 
a  transformation  into  a  compound,  termed  Fibrine,  which  is  distinguished  from 
it  by  new  and  peculiar  properties.  It  appears  from  the  analyses  of  Mulder 
and  Scherer,  that  there  is  no  essential  difference  in  the  ultimate  composition 
of  these  two  substances ;  the  relative  proportions  of  the  constituents  of  each 
being,  according  to  them,  as  follow: — 


MULDER. 


SCHERER. 


Albumen.    Fibrine.       Albumen.      Fibrine. 


Carbon    . 

Hydrogen 

Nitrogen 

Oxygen 

Phosphorus 

Sulphur 


54-84 

7-09 

15-83 

21-23 

•33 

•68 


54-56 

6-90 

15-72 

22-13 

•33 

•36 


53-850 

6-983 

15-673 

23-494 


53-671 

6-878 

15-763 

23-688 


100-00      100-00 


100-000       100-000 


The  wide  difference  in  their  properties  must  be  referred,  on  this  view,  solely 
to  a  change  in  the  molecular  arrangement  of  their  ultimate  particles.  Accord- 
ing to  Dumas,  however,  there  is  a  marked  difference  in  composition,  between 
Fibrine  and  the  various  forms  of  Albumen; — the  former  having  less  Carbon, 
and  more  Nitrogen,  than  the  latter.  The  following  are  the  results  of  his 
analyses : — 


Carbon 

Hydrogen 

Nitrogen 

Oxygen 

Sulphur 

Phosphorus 


ALBUMEN. 

,  A 

From  serum.  From  eggs. 
.     53-32  53-37 

7-29  7-10 

15-70  15-77 


23-69 


23-76 


FIBRINE. 


52-78 

6-96 

16-78 

23-48 


100-00 


100-00 


100-00 


104  ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 

It  is  not,  perhaps,  of  any  great  moment  whether  this  difference  has  a  real 
existence  or  not;  for  the  conversion  of  Albumen  into  Fibrine  is  unquestion- 
ably a  process  much  more  of  vital  than  of  chemical  transformation.  We 
shall  presently  see,  that  Fibrine  may  be  regarded  as  Albumen,  in  which  the 
process  of  Organization  has  begun ;  its  molecules  being  ready  to  assume  the 
peculiar  arrangement  that  is  so  designated  :  this  arrangement  takes  place 
most  completely,  when  the  fibrinous  mass  is  in  contact  with  a  living  tissue, 
and  is  therefore  to  a  certain  degree  under  its  influence.  Fibrine,  like  Albu- 
men,, may  exist  in  a  soluble  or  in  a  coagulated  state ;  its  soluble  form  only 
occurs,  however,  in  certain  living  animal  fluids, — the  Chyle,  Lymph,  and 
Blood; — and  it  seems  to  be  the  intermediate  condition  between  the  soluble  al- 
bumen, and  the  solid  organized  substances  which  are  formed  from  it.  When 
withdrawn  from  the  blood-vessels,  the  Blood  soon  coagulates,  as  do  also  the 
Chyle  and  Lymph,  when  they  contain  sufficient  fibrine;  and  this  coagulation 
is  entirely  due  to  a  change  in  the  condition  of  the  Fibrine,  the  particles  of 
which  have  a  tendency  to  aggregation  in  a  definite  manner.  The  Fibrine  may 
be  obtained  in  a  separate  form,  by  stirring  fresh-drawn  blood  with  a  stick,  to 
which  it  adheres  in  threads ;  these  contain  some  fatty  matter,  which  is  to  be 
washed  out  with  alcohol.  In  this  condition  it  possesses  the  softness  and  elas- 
ticity which  characterize  the  flesh  of  animals ;  and  contains  about  three-fourths 
of  its  weight  of  water.  It  may  be  deprived  of  this  water  in  dry  air,  and  then 
becomes  a  hard  and  brittle  substance  ;  but,  like  flesh,  it  imbibes  water  again 
when  moistened,  and  recovers  its  original  softness  and  elasticity.  When 
burned,  it  always  leaves,  like  albumen,  a  portion  of  phosphate  of  lime.  Fi- 
brine is  insoluble  in  alcohol  and  ether,  and  also,  under  ordinary  circumstances, 
in  water;  but  when  long  boiled  in  water,  especially  underpressure,  its  nature 
is  altered,  and  it  becomes  soluble.  This  change,  which  may  be  effected  also 
in  coagulated  Albumen,  is  attributed  by  Mulder  to  the  oxidation  of  the  Pro- 
teine,  which  is  its  principal  constituent  (§  116,  a).  When  Fibrine  is  treated 
with  strong  acetic  acid,  it  imbibes  the  acid,  and  swells  up  into  a  transparent 
colourless  jelly,  which  is  soluble  in  hot  water;  this  solution  is  precipitated  by 
the  addition  of  another  acid. 

115.  Fibrine,  like  Albumen,  unites  with  acids  as  a  base,  forming  definite 
compounds ;  and  with  bases  as  an  acid.     Its  correspondence  with  Albumen 
is  further  indicated  by  the  fact  (first  stated  by  M.  Denis),  that  it  may  be  en- 
tirely dissolved  in  a  solution  of  nitrate  of  potash;  and  that  this  solution  is 
coagulated  by  heat,  and  greatly  resembles  a  solution  of  Albumen.     This  is 
only  true,  however,  Of  the  ordinary  Fibrine  of  venous  blood;  for  that  which 
is  obtained  from  arterial  blood  or  from  the  buffy  coat,  or  which  has  been  ex- 
posed for  some  time  to  the  air,  is  not  thus  soluble.     This  is  an  important  and 
interesting  circumstance.     The  difference  appears  to  depend  upon  the  larger 
quantity  of  oxygen  contained  in  the  latter;  for  a  solution  of  Venous  Fibrine  in 
nitre,  contained  in  a  deep  cylindrical  jar,  allows  a  precipitate  in  fine  flocks  to  fall 
gradually,  provided  the  air  have  access  to  the  surface,  but  not  if  it  be  prevented 
from  coming  in  contact  with  the  fluid ;  this  precipitate  is  insoluble  in  the  solution 
of  nitre,  and  possesses  the  properties  of  'arterial  fibrine.     Hence  it  may  be 
inferred,  that  the  Fibrine  of  Venous  blood  most  nearly  resembles  Albumen ; 
whilst  that  of  Arterial  blood,  and  of  the  Buffy  coat,  contains  more  oxygen, 
and  is  more  highly  animalized. — When  decomposition  commences  in  a  coagu- 
lum  of  .Fibrine  withdrawn  from  the  body  (and  even  in  the  greatly-debilitated 
living  body,  in  which  the  Fibrine  appears  to  be  imperfectly  formed),  a  granu- 
lar mode  of  aggregation  is  evident  in  the  particles  of  the  mass, — thus  showing 
its  affinity  to  Albumen,  when  its  peculiar  vital  characters  have  departed,  or 
are  possessed  by  it  in  an  inferior  degree. 

116.  The  close  chemical  relation  existing  between  Albumen  and  Fibrine 


PROTEINE,  AND  ITS  TRANSFORMATIONS.  105 

is  further  shown  by  the  fact,  that  from  both  of  them  (as  well  as  from  various 
substances  used  as  food,  which  are  furnished  by  the  Vegetable  kingdom,  §  111) 
an  identical  substance  may  be  obtained  by  a  simple  process.  If  boiled  al- 
bumen be  dissolved  in  a  weak  solution  of  caustic  alkali,  and  the  liquid  be 
neutralized  by  an  acid,  a  precipitate  falls  down  in  grayish-white  flocks ;  this, 
being  collected  and  washed,  is  gelatinous,  of  a  grayish  colour,  and  semi-trans- 
parent; and,  when  dried,  it  is  yellowish,  hard,  easily  pulverized,  tasteless,  in- 
soluble in  water  and  alcohol,  and  decomposed  by  heat  without  fusing.  This 
substance  has  been  termed  Proteine^  from  an  idea  that  it  is  the  fundamental 
proximate  principle  of  which  Albumen,  Fibrine,  &c.,  are  modifications.  It 
contains  the  same  proportions  of  Carbon,  Hydrogen,  Nitrogen  and  Oxygen,  with 
Albumen  and  Fibrine  ;  but  it  has  been  commonly  regarded  as  destitute  of  their 
Sulphur  and  Phosphorus;  .the  most  recent  investigations  of  Liebig,  however, 
render  it  doubtful  whether  this  is  the  case.  According  to  Mulder  (its  dis- 
coverer), its  composition  may  be  represented  by  the  formula  40  C,  31  H,  5  N, 
12  O ;  whilst  by  Liebig  it  is  represented  by  the  formula  48  C,  36  H,  6  N,  14  O. 
Either  of  these  correctly  represents  the  relative  proportions  of  tlie  elements, 
as  deduced  from  analysis ;  but  the  formula  of  Mulder  is  asserted  by  him  to 
represent  more  accurately  the  combining  equivalent  of  the  entire  substance, 
as  deduced  from  the  compounds  it  forms  with  others. 

a.  According  to  Mulder,  Proteine  unites  with  Oxygen  in  definite  proportions,  so  as  to  form 
a  binoxide  and  a  tritoxide.     These  are  both  produced  when  Fibrine  is  boiled  in  water  for 
some  time;  the  latter  being  then  found  in  solution,  whilst  the  former  remains  insoluble. 
The  tritoxide  may  also  be  formed  by  boiling  Albumen  for  some  time  in  water,  when  it  is  in 
like  manner  taken  up  in  solution ;  but  the  insoluble  residue  is  still  albumen.     It  is  further 
attainable  by  decomposing  the  chlorite  of  proteine  with  ammonia.     In  its  properties  it  some- 
what resembles  Gelatine,  and  has  been  mistaken  for  that  substance.     There  is  reason  to 
think  that  this  compound  really  exists  as  such  in  the  blood;  a  small  quantity  of  it  being 
formed  every  time  that  the  blood  passes  through  the  lungs,  and  given  out  again  when  it 
returns  to  the  system ;  and  a  much  larger  quantity  being  generated  during  the  inflammatory 
process,  so  that  it  may  be  easily  obtained  from  the  buffy  coat  by  boiling.     It  is  also  said  to 
be  contained  in  pus.     The  binoxide  is  quite  insoluble  in  water,  but  dissolves  in  dilute  acids. 
It  may  be  obtained  by  dissolving  Hair  in  potash,  adding  a  little  acid  to  throw  down  the 
proteine,  and  then  adding  a  large  excess  of  acid,  which  precipitates  the  binoxide.     Accord- 
ing to  Mulder,  this  compound  also  is  produced  in  small  quantity  at  every  respiration;  and  it 
enters  into  the  normal  composition  of  several  of  the  animal  tissues. — These  views,  however, 
must  still  be  received  with  some  hesitation.     They  are  liable  to  the  fundamental  objection, 
advanced  against  them  by  Liebig;  that  the  binoxide  and  tritoxide,  like  proteine  itself,  contain 
the  sulphur  of  albumen  and  fibrine.     Still,  the  production  of  new  and  peculiar  compounds, 
by  the  processes  indicated,  is  an  important  fact  which  cannot  be  overthrown ;  whatever 
may  prove  to  be  the  case  in  regard  to  the  ultimate  composition  of  these  substances. 

b.  One  of  the  most  characteristic  and  important  properties  of  Proteine,  is  the  facility  with 
which  it  undergoes  decomposition,  when  acted  on  by  other  chemical  substances,  especially 
by  alkalies.     If  a  proteine-compound  be  brought  into  contact  with  an  alkali,  ammonia  is  im- 
mediately disengaged ;  indeed  the  alkaline  solution  can  hardly  be  made  weak  enough  to 
prevent  the  disengagement  of  ammonia.     This  is  a  property,  which  must  be  continually 
acting  in  the  living  body ;  since  the  blood  has  a  decidedly  alkaline  reaction.     If  either  albu- 
men, or  any  other  proteine  compound,  be  boiled  with  potash,  it  is  completely  decomposed; 
not,  however,  being  resolved  at  once  into  its  ultimate  constituents,  or  altogether  into  simple 
combinations  of  them;  but  in  great  part  into  three  other  organic  compounds, — Leucin,  Protid, 
and  Erythroprotid.     Leucin  is  a  crystalline  substance,  which  forms  colourless  scales,  destitute 
of  taste  and  odour;  it  is  soluble  in  water  and  alcohol,  and  sublimes  unchanged.     It  consists 
of  12  Carbon,  12  Hydrogen,  1  Nitrogen,  and  4  Oxygen.     There  is  not  at  present  any  evi- 
dence, that  it  is  produced  in  the  living  body;  but  considerable  interest  attaches  to  it  from  the 
fact,  that  it  may  be  procured  from  Gelatine,  as  well  as  from  Proteine;  a  near  relationship 
between  these  two  substances  being  thus  indicated.     The  other  two  compounds,  Protid  and 
Erythroprotid,  are  uncrystalline  substances ;  the  former  of  a  straw-yellow,  the  latter  of  a  red- 
dish-brown colour ;  they  belong  to  the  class  of  bodies  which  were  formerly  included  under 
the  vague  general  term  of  extractive  matter;  and  they  bear  a  strong  resemblance  to  Gelatine, 
not  only  in  their  solubility  in  water,  but  also  in  their  chemical  composition,  as  is  shown  by 
the  following  comparison  of  their  formulae : — 


106  ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 

C.  H.         yr.        O. 

Protid     . 13  914 

Erythroprotid     . 13  8        .1         5 

Gelatine          .                  13  10         2         5 

Besides  these  substances  and  Ammonia,  Formic  and  Carbonic  Acids  are  produced  by  the 
decomposition  of  Proteine  with  potash ;  the  acids  unite  with  the  potash,  whilst  the  ammonia 
is  set  free. 

117.  It  is  very  important,  however,  to  bear  in  mind,  that  however  close 
may  be  the  chemical  approximation  between  Albumen  and  Fibrine,  there  is  a 
wide  difference  between  them,  as  regards  their  relations  to  living  organized 
structures :  and  this  difference  is  one  of  which  chemistry  takes  no  cogni- 
zance. To  use  a  rather  homely  illustration,  the  relation  between  Albumen, 
Fibrine,  and  Organized  Tissue  is  somewhat  of  the  .same  nature  as  that  which 
exists  between  the  raw  cotton,  the  spun  yarn,  and  the  woven  fabric.  Albu- 
men shows  no  tendency  to  coagulate,  except  under  the  influence  of  purely 
chemical  agents,  and  its  coagulum  is  entirely  destitute  of  structure,  being  a 
mere  homogeneous  aggregation  of  particles.  On  the  other  hand,  Fibrine 
exhibits  a  constant  tendency  to  pass  into  the  form  of  a  solid  tissue ;  and  it 
seems  only  restrained  from  doing  so  by  certain  influences,  whose  nature  is 
not  understood,  to  which  it  is  subjected  whilst  contained  in  the  vessels  of  the 
living  body.  The  conversion  of  Albumen  into  Fibrine,  therefore,  is  the  first 
great  step  in  the  process  of  Nutrition,  by  which  the  materials  supplied  by  the 
food  are  made  to  form  part  of  the  living  tissues  of  the  body  ;  and  it  is  the  one 
to  which  the  term  Assimilation  may  be  most  appropriately  applied.  As 
already  mentioned,  Albumen  is  always  the  starting-point;  since  the  fibrinous 
elements  of  organized  tissues  are  reduced,  by  the  solvent  power  of  the  gas- 
tric fluid,  to  the  same  form  with  the  unorganized  coagulum  of  the  albumen  of 
the  egg.  The  first  appearance  of  Fibrine  is  in  the  Chyle,  or  fluid  of  the 
Lacteals  ;  and  when  this  is  examined  in  the  neighbourhood  of  the  part  where 
it  has  been  absorbed,  the  traces  of  Fibrine  which  it  presents  are  very  slight. 
As  the  Chyle  flows  along  the  lacteals,  however,  the  proportion  of  Fibrine  in- 
creases ;  and  it  reaches  its  maximum  at  the  point  where  the  Chyle  is  de- 
livered into  the  current  of  the  circulating  Blood.  The  proportion  of  Fibrine 
in  the  Blood,  as  indicated  by  the  firmness  of  the  coagulum  which  it  forms,  is 
much  greater  than  that  contained  in  the  Chyle,  notwithstanding  that  there  is 
a  constant  withdrawal  of  this  element  for  the  purpose  of  nutrition.  And  in 
certain  disordered  states  of  the  system,  in  which  the  formative  powers  of  the 
Blood  are  so  exalted,  as  to  produce  a  tendency  to  the  formation  of  tissue  in 
abnormal  situations,  the  proportion  of  Fibrine  is  found  to  be  increased  to 
twice,  thrice,  or  even  four  times  its  usual  amount.  And  even  where  there  is 
no  such  general  increase,  a  local  increase  is  made  evident  in  the  large  pro- 
portion of  fibrine,  which  exists  in  the  exudations  poured  forth  for  the  repara- 
tion of  injuries ;  these  exudations,  when  possessed  of  a  high  formative  pro- 
perty (that  is,  a  readiness  to  produce  an  organized  tissue),  are  said  to  be 
composed  of  plastic,  or  coagulable  lymph;  but  this  is  nothing  more  than  the 
Liquor  Sanguinis,  or  fluid  portion  of  the  Blood,,  holding  in  solution  an  unu- 
sual quantity  of  Fibrine.  It  is  evident,  from  these  facts,  that  some  peculiar 
agency  must  exist  within  the  vessels,  by  which  the  elaboration  of  the  Fibrine 
from  the  Albumen  is  effected ;  and  we  shall  hereafter  endeavour  to  bring 
together  certain  facts,  which  seem  to  indicate  its  nature. 

J18.  The  tissue  that  is  produced  by  the  apposition  of  the  particles  of 
Fibrine,  when  left  to  themselves,  and  solely  influenced  by  their  own  mutual 
attraction,  is  of  a  very  simple  character,  being  composed  of  fibres  interlaced 
with  each  other  in  various  directions.  This  arrangement  can  be  seen  in  the 
ordinary  Crassamentum,  or  clot  of  healthy  Blood,  by  examining  thin  slices 


FIBRILLATION  OF  COAGULATED  FIBRINE. 


107 


Fig.  10. 


under  the  microscope ;  especially  after  the  clot  has  been  hardened  by  boiling. 
A  number  of  fibres,  more  or  less  distinct,  may  be  seen  to  cross  one  another ; 
forming  by  their  interlacement  a  tolerably  regular  network,  in  the  meshes  of 
which  the  red  corpuscles  are  entangled.  This  fact  was  known  to  Haller ; 
but  it  has  been  generally  overlooked  by  subsequent  Physiologists,  until  atten- 
tion was  drawn  to  it  by  the  inquiries  of  Messrs.  Addison,  Gulliver,  and 
others.  It  is  in  the  Buffy  Coat,  however,  that  the  fibrous  arrangement  is  best 
seen;  on  account,  as  it  would  appear,  of  the  stronger  attraction  which  the 
particles  of  fibrine  have  for  one  another,  when  its  vitality  has  been  raised  by 
the  increased  elaboration  to  which  it  has  been  subjected.  That  there  are  va- 
rieties of  plasticity  in  the  substance,  which,  on  account  of  its  power  of  spon- 
taneously coagulating,  we  must  still  c$\\  fibrine,  appears  from  this  fact  among 
others, — that,  in  tuberculous  subjects, 
the  quantity  of  fibrine  in  the  blood  is 
higher  than  usual  (Andral  and  Gavarret), 
although  its  plasticity  is  certainly  below 
par.  It  is  as  easy  to  understand,  that 
its  plasticity  may  be  increased,  as  that  it 
may  be  diminished;  and  this  either  in 
the  general  mass  of  the  blood,  or  in  a 
local  deposit.  In  fact,  the  adhesions 
which  are  formed  by  the  consolidation 
of  coagulable  lymph, — or  in  other  words, 
of  the  fluid  portion  of  the  blood,  whose 
plasticity  has  been  heightened  by  the 
vital  actions  that  take  place  within  the 
capillaries  of  the  part  on  which  it  has 
been  effused, — often  acquire  very  con- 
siderable firmness,  before  any  vessels 
have  penetrated  them ;  and  this  firmness  must  depend  upon  that  mutual 
attraction  of  the  particles  for  one  another,  which  in  aplastic  deposits  is  alto- 
gether wanting,  and  which  in  cacoplastic  deposits  is  deficient. — A  very  inte- 
resting example  of  a  structure  entirely  composed  of  matted  fibres,  and  evi- 
dently originating  in  the  simple  consolidation  of  Fibrine,  is  found  in  the 
membrane  adherent  to  the  interior  of  the  Egg-shell  (Membrana  putaminis) ; 
and  also  in  that  which  forms  the  basis  of  the  Egg- 
shell itself.  Between  the  two,  there  is  no  essen- 
tial difference  ;  as  may  be  seen  by  examining  "  an 
egg  without  shell,"  as  it  is  commonly  termed,  (or 
rather  one  in  which  the  shell-membrane  has  been 
unconsolidated  by  the  deposition  of  calcareous 
matter) ;  or  by  treating  the  egg-shell  with  dilute 
acid,  so  as  to  remove  the  particles  of  carbonate  of 
lime,  which  are  deposited  in  the  interstices  of  the 
network.  The  place  of  the  shell  is  then  found  to 
be  occupied  by  a  membrane  of  considerable  firm- 
ness, closely  resembling  that  which  lines  the  shell 
and  surrounds  the  albumen  of  the  egg,  but  thicker 
and  more  spongy.  After  maceration  for  a  few 
days,  either  of  these  membranes  may  be  separated 
into  a  number  of  laminae,  each  of  which  (if  suffi- 
ciently thin)  will  show  a  beautiful  arrangement  of  reticulated  fibres.  It  is 
impossible  to  refuse  to  such  a  structure  the  designation  of  an  organized  tis- 
sue, although  it  contains  no  vessels,  and  must  be  formed  by  the  simple  con- 
solidation of  Fibrine,  poured  out  from  the  lining  membrane  of  the  oviduct  of 


Fibrous  structure  of  inflammatory  exudation 
from  peritoneum. 


Fig.  11. 


Fibrous  membrane  from 
Egg-shell. 


108  ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 

the  bird.  It  is  probably  in  the  same  manner,  that  the  Chorion  of  the  Mam- 
miferous  animal  originates ;  since  this  is  a  new  envelope,  formed  around  the 
ovum,  during  its  passage  along  the  Fallopian  tube.  In  the  latter,  for  an  ulte- 
rior purpose,  vessels  are  afterwards  developed,  by  extension  from  the  con- 
tained ovum ;  and  by  the  nutrition  they  supply,  its  size  is  increased,  and 
changes  take  place  in  its  texture.  But  in  the  Egg-membrane  of  the  Bird, 
there  is  no  need  of  vessels ;  because  no  subsequent  change  in  its  texture  is 
required,  and  its  duration  is  sufficient  for  the  purpose  it  has  to  answer. 

119.  The  completeness  of  the  transformation  of  Fibrine  into  simple  Fi- 
brous Tissue,  appears  to  depend  upon  two  circumstances  in  particular  ; — the 
perfect  elaboration  of  the  Fibrine  itself;  and  the  vitality  of  the  surface  upon 
which  the  concretion  takes  place.     When  the  Fibrine  is  highly  elaborated,  it 
will  coagulate  in  the  form  of  a  definite  network  of  minute  fibrillae,  even  upon 
a  dead  surface,  as  a  slip  of  glass  ;  this  is  the  case,  for  instance,  with  the  Fi- 
brine of  the  buffy  coat  of  the  Blood,  or  with  that  of  the  Liquor  Sanguinis 
(coagulable  lymph)  poured  out  for  the  reparation  of  an  injured  part.     But  in 
the  ordinary  Fibrine  of  the  blood,  the  fibrillation  is  less  distinct  when  the  con- 
cretion takes  place  upon  a  dead  surface.     When  it  occurs  in  contact  with  a 
living  surface,  however,  the  coagulation  takes  place  more  gradually;  and  it 
seems  as  if  the  particles,  having  more  time  to  arrange  themselves,  become  ag- 
gregated into  more  definite  forms,  so  that  a  more  regular  tissue  is  produced — 
just  as  crystals  are  most  perfectly  formed  when  the  crystalline  action  takes 
place  slowly.     It  was  formerly  imagined  that  the  Muscular  tissue  is  the  only 
one  produced  at  the  expense  of  the  Fibrine  of  the  blood  ;  the  other  tissues 
being  formed  from  its  Albumen.    This,  however,  is  unquestionably  erroneous. 
There  is  no  proof  whatever  that  Albumen,  as  long  as  it  remains  in  that  con- 
dition, ever  becomes  organized ;  whilst,  on  the  other  hand,  there  is  abundant 
evidence,  that  the  plasticity  of  any  fluid  deposit — that  is,  its  capability  of  be- 
ing metamorphosed  into  organized  tissue- — is  in  direct  relation  with  the  quan- 
tity of  Fibrine  which  it  contains.     Thus  the  Liquor  Sanguinis,  or  Coagulable 
Lymph,  thrown  out  for  the  reparation  of  injuries,  contains  a  large  amount  of 
Fibrine ;  and  this  substance  is  converted,  not  at  first  into  muscular  fibre,  but 
(whatever  may  be  the.  tissue  to  be  ultimately  produced  in  its  place)  into  a 
fibrous  network,  which  fills  up  the  breach  and  holds  together  the  surrounding 
structure.     This  may  be  regarded  as  a  simple  form  of  areolar  tissue  ;  which 
gradually  becomes  more  perfectly  organized  by  the  extension  of  vessels  and 
nerves  into  its  substance  ;  and  in  which  other  forms  of  tissue  may  subse- 
quently make  their  appearance.     This  process  will  be  more  particularly  de- 
scribed hereafter ;  it  is  at  present  noticed  here  as  an  illustration  of  the  general 
fact,  thatjibrine  is  to  be  regarded  as  the  plastic  element  of  the  nutritive  fluids. 

3.   Of  the  Elementary  Parts  of  Organized  Tissues; — Cells,  Membrane, 

and  Fibre. 

120.  The  cells,  which  have  been  spoken  of  as  making  up  the  chief  part  of 
the  Vegetable  Organism,  are  minute  closed  sacs;  whose  walls  are  composed 
in  the  first  instance  of  a  delicate  membrane,  frequently  strengthened,  at  a 
period  long  subsequent  to  their  first  formation,  by  some  internal  deposit.     The 
form  of  these  cells  is  extremly  variable  ;  and  depends  chiefly  upon  the  degree 
and  direction  of  the  pressure,  to  which  they  may  have  been  subjected  at  the 
period  of  their  origin,  and  subsequently  to  it.     Sometimes  they  are  spheroidal ; 
sometimes  cubical  or  prismatic ;  sometimes  cylindrical ;  and  sometimes  very 
much  prolonged.    These  cells  may  undergo  various  transformations. — One  of 
the  most  common,  is  the  conversion  of  several  into  a  continuous  tube  or  Duct. 
This  is  principally  seen  in  the  vessels,  through  which  the  sap  ascends  the  stem  ; 


DEVELOPMENT  AND  METAMORPHOSES  OF  CELLS.  109 

these  appear  to  have  been  formed  by  the  breaking-down  of  the  transverse 
partitions,  between  a  regular  series  of  cylindrical  cells  laid  end  to  end ;  and 
the  remains  of  such  partitions  may  frequently  be  seen  in  them.  The  ducts 
which  convey  the  ascending  sap,  do  not  inosculate  with  each  other ;  their 
purpose  being  merely  to  carry  it  direct  to  the  leaves  ;  but  the  vessels,  through 
which  the  descending  or  elaborated  sap  flows,  are  of  very  different  character; 
for  their  purpose  is  to  distribute  the  nutritious  fluid  through  the  tissues; 
and  they  anastomose  very  freely,  just  as  do  the  capillaries  of  Animals.  The 
network  which  they  form,  however,  can  be  as  clearly  traced  to  an  origin  in  cells, 
whose  cavities  were  originally  distinct,  as  can  the  bundles  of  straight  non- 
communicating  ducts. — Another  important  transformation  of  the  original  cells, 
is  that  by  which  the  Woody  Fibres,  which  compose  nearly  all  the  fibrous 
textures  of  Vegetables,  are  produced.  These  fibres  are  still  cells,  but  their  form  is 
very  much  elongated  ;  they  have  a  fusiform  or  spindle  shape,  being  tubes  drawn 
to  a  point  at  each  end ;  at  first  they  are  quite  pervious,  like  ordinary  cells ; 
but  in  the  older  wood,  their  cavity  is  filled  up  by  interior  deposit. 

121.  Such  deposits  may  take  place  in  cells  of  the  ordinary  form  ;  and  they 
present  many  variations  in  their  character,  which  give  corresponding  peculi- 
arities to  the  cells  which  contain  them.    In  many  instances,  they  consist  merely  of 
concentric  layers,  one  within  the  other,  each  layer  completely  lining  the  one 
which  preceded  it ;  and  the  cavity  of  the  cells  being  thus  gradually  but  uni- 
formly contracted  in  every  dimension.     In  other  cases,  certain  points  of  the 
original  external  cell-membrane  are  left  uncovered  by  the  secondary  deposits  ; 
and  thus,  the  same  vacuities  being  left  in  the  successive  layers,  passages  are 
formed,  which  stretch  out  from  the  central  cavity  to  certain  spots  of  the  peri- 
phery of  the  cell.     Cells  of  this  character  are  found  in  certain  parts  of  plants, 
which  are  required  to  possess   unusual  firmness,  without  losing  the  power  of 
transmitting  fluid,  the  former  endowment  being  conferred  by  the  secondary 
deposits;  whilst  the  latter  is  retained  by  the  peculiar  system  of  passages  just 
described, — the  thin  or  uncovered  parts  of  the  wall  of  one  cell  being  in  contact 
with  corresponding  spots  on  the  walls  of  adjacent  cells,  as  we  see  in  the  tissue 
of  the  stones  of  fruit,  the  central  gritty  matter  of  the  pear,  &c. — Lastly,  the 
new  deposit  may  present  the  form  of  a  more  or  less  regular  spiral  fibre,  winding 
within  the  cell  from  end  to  end ;  and  this  may  present  itself  alike  in  cells  of 
the  ordinary  shapes,  or  in  fusiform  cells  (constituting  the  proper  spiral  ves- 
sels), or  in  cells  that  have  coalesced  into  continuous  tubes  or  ducts.     The 
spiral  may  break  up  into  rings  or  irregular  pieces ;  and  these  may  be  united 
again  by  additional  deposits  of  a  still  more  irregular  character,  so  as  completely 
to  obscure  their  original  spiral  form.    This  spiral  fibre  is  very  completely  gene- 
rated, in  some  instances,  when  the  cell-wall  itself  has  not  acquired  any  greater 
tenacity  than  that  of  mucus,  very  easily  dissolved  ;  which  (as  we  shall  presently 
see)  is  a  stage  in  the  production  of  cells  in  general.     Such  spiral  fibres  spring 
out  from  the  external  coats  of  many  seeds,  when  they  are  moistened  with 
fluids. 

122.  So  far  as  is  yet  known,  all  Cells  originate  in  germs,  that  have  been  pre- 
pared by  some  previously-existing  cell;  and  these  germs  may  either  be  de- 
veloped within  the  parent-cell,  or  may  be  set  free  by  its  rupture,  and  may  be 
developed  quite  independently.     The  latter  case,  being  the  simplest,  will  be 
first  considered ;  we  have  numerous  examples  of  it  among  the  lower  Cellular 
Plants.     In  the  first  place,  the  germ,  from  which   the  cell  originates,  is  a  mi- 
nute granule,  only  to  be  seen  with  a  good  microscope,  and  apparently  quite 
homogeneous.     It  has  the  power  of  drawing  to  itself  the  nutrient  elements 
around,  and  of  combining  these  into  the  proximate  principles,  that  may  serve 
as  the  materials  for  its  development.     By  the  incorporation  of  these  with  its 
own  substance,  it  gradually  increases  in  size,  and  a  distinction  becomes  ap- 

10 


110 


ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 


parent,  between  its  transparent  exterior  and  its  coloured  interior.  Thus  we 
have  the  first  indications  of  the  cell-wall,  and  the  cavity.  As  the  enlarge- 
ment proceeds,  the  distinction  becomes  more  obvious  ;  the  cell-wall  is  seen  to 
be  of  extreme  tenuity,  perfectly  transparent,  and  apparently  homogeneous  in 
its  texture  ;  whilst  the  contents  of  the  cavity  are  distinguished  by  their  colour, 
which  (in  the  species  here  alluded  to)  is  commonly  either  green  or  bright  red. 
At  first  they,  too,  seem  to  be  homogeneous ;  but  a  finely-granular  appearance 
is  then  preceptible  amongst  them ;  and  a  change  gradually  takes  place,  which 


Fig.  12. 


Simple  isolated  cells  con- 
taining productive  mole- 
cules. 


seems  to  consist  in  the  aggregation  of  the  minuter 
molecules  into  granules  of  more  distinguishable  size  and 
form.  These  granules,  which  are  the  germs  of  new 
cells,  seem  to  be  at  first  attached  to  the  inner  wall  of  the 
parent-cell ;  afterwards  they  separate  from  it,  and  move 
about  in  its  cavity ;  and  at  a  later  period,  the  parent- 
cell  bursts  and  sets  them  free.  Now  this  is  the  ter- 
mination of  the  life  of  the  parent-cell ;  but  the  com- 
mencement of  the  life  of  a  new  generation :  since  every 
one  of  these  germs  may  develope  itself  into  a  cell,  after 
precisely  the  foregoing  manner  ;  and  will  then,  in  turn, 
propagate  its  kind  by  a  similar  process. 

123.  The  development  of  new  cells  within  the  pa- 
rent,— or  what  may  be  termed  the  endogenous  mode 
of  cell-growth, — takes  place  in  many  instances  on  a  plan  which  differs  in  no 
respect  from  the  preceding,  except  that  the  parent-cell  does  not  rupture.  The 
granules  it  contains  derive  their  nutriment  from  the  surrounding  fluid,  which 
is  included  within  the  cell ;  by  their  progressive  increase  in  size,  they  gradu- 
ally fill  up  the  whole  cavity  of  the  parent-cell ;  and  by  a  further  increase,  they 
distend  its  wall,  which  becomes  thinner  and  thinner,  and  at  last  ceases  to  be 
visible  around  the  newly-formed  cluster.  » 

124.  In  other  instances,  however,  we  find  that  the  development  of  new 
,.,.  cells  proceeds,  not  from  granules  scattered  through  the  whole 

interior  of  the  cell,  but  from  a  determinate  spot  or  nucleus, 
which  is  seen  upon  its  wall.  This  nucleus  is  frequently  formed 
very  early,  by  the  aggregation  of  molecules  around  the  original 
granule  or  cell-germ,  even  previously  to  the  first  appearance  of 
the  distinct  cell-membrane ;  and  by  Schleiden,  who  first  ob- 
served this  process,  it  was  thought  that  the  body  thus  produced 
was  essential  to  the  development  of  the  new  cell,  whence  he 
gave  it  the  name  of  cytoblast.  It  appears,  however,  from  more 
extended  inquiries,  that  this  is  not  the  case ;  and  that  the  nu- 
cleus is  rather  concerned  with  the  subsequent  operations  which 
the  cell  performs,  than  with  its  original  development.  Fre- 
quently the  nucleus  does  not  make  its  appearance,  until  the  cell 
itself  has  been  completely  formed.  It  is  chiefly  in  the  higher 
tribes  of  Plants,  that  we  find  these  nucleated  cells ;  the  nucleus 
in  the  cells  of  the  lower  Cryptogamia  being  usually  more  or 
less  expanded  or  diffused  (as  it  were),  through  the  entire  cavity. 
The  destination  of  the  several  forms  of  cells  which  make  up 
the  complex  structure  of'  the  higher  plants,  is  very  different ; 
and  their  office  seems  in  great  measure  to  depend  upon  the 
peculiar  powers  of  the  nucleus.  In  some  instances,  this  body 
seems  to  be  the  centre  which  attracts  new  deposits ;  even  the 
Ceils  of  zygne-  spiral  filament  being  probably  formed  by  its  agency.  We 
ma,  showing  spiral  have,  in  some  of  the  lowest  Cellular  Plants,  a  curious  fore-sha- 
arrangementof  the  dowmg  Of  the  spiral  vessels  of  the  most  perfect ;  the  green 

nuclear  panicles. 


DEVELOPMENT  AND  MULTIPLICATION  OF  CELLS. 


Ill 


Fig.  14. 


particles  (or  diffused  nucleus  ?)  of  the  cells,  in  the  genus  Zygnema,  presentin 
a  regular  spiral  arrangement  at  one  period  of  their  growth  (Fig.  13).  An 
in  other  instances,  as  in  the  cells  of  the  petal  of 
the  common  Geranium  (Pelargonium},  we  find 
the  nucleus  sending  out  curious  stellate  or  radi- 
ating prolongations  (Fig.  14.)  These  facts  are 
of  much  interest,  as  illustrating  some  of  the  more 
obscure  changes  which  are  believed  to  take  place 
in  animal  tissues. 

125.  But  the  nucleus  may  also  be  the  source 
from  which  the  new  cells  arise,  thai  are  devel- 
oped within  the  cavity  of  the  parent.  Several  vari- 
eties in  the  mode  in  which  this  process  takes  place, 
are  presented  to  our  observation  in  the  simplest  of 
the  Cellular  Plants,  belonging  to  the  group  of  the 
Fresh-water  Algae  ;  the  growth  of  which  may  be 
studied  with  peculiar  facility.  In  some  of  these 
the  cell  is  destitute  of  a  nucleus,  but  is  filled  with 
a  very  finely-divided  granular  matter,  the  en- 
dochrome;  and  the  process  of  cell-multiplication 
is  effected  by  the  subdivision  of  this  matter  into 
two  distinct  masses,  around  each  of  which  a  pellucid  cell-membrane  subse- 
quently makes  its  appearance,  thus  forming  two  new  cells  within  the  parent. 
By  a  repetition  of  the  same  process,  each  of  these  new  cells  may  again  pro- 
duce two  new  ones ;  and  thus  the  multiplication  may  be  rapidly  effected. 

Fig.  16. 


Cells  from  the  petal  of  Pelargonium 
showing  stellate  prolongations  of  the 
nuclei. 


Htmatococcusbinalis,  in  various  stages  of  devel. 
opment ;  o,  a,  simple  rounded  cells ;  6,  elongated 
cell,  the  endochrome  preparing  to  divide  ;  c,  c,  cells 
in  which  the  division  has  taken  place ;  d,  large  pa- 
rent cell,  in  which  the  process  has  been  repeated 
a  second  time,  so  as  to  form  a  cluster  of  four  se- 
condary cells,  such  as  is  often  seen  in  Cartilage. 


CoceoMoris  cystifera,  showing  various  stages  of 
development: — a, simple  globular  cells, surround- 
ed by  a  well-defined  mucous  envelope  ;  6,  elon- 
gated cell  about  to  divide  ;  c,  cell  doubled  by  di- 
vision, both  the  new  cells  still  enclosed  in  original 
mucous  envelope  ;  d,  further  stage  of  the  same 
process,,  one  of  the  secondary  cells  having  again 
divided,  whilst  the  other  has  not  yet  undergone 
this  change,  but  is  about  to  do  so ;  e,  group  of 
cells  formed  by  the  same  process,  and  still  re- 
tained within  the  original  mucous  envelope. 


This  form  of  cell-development  is  best  seen  in  some  of  the  simplest  Algae, 
which  consist  of  isolated  cells,  and  in  which  the  individuals  composing  the 
successive  generations  are  quite  independent  of  one  another  ;  and  we  have  a 
good  illustration  of  it  in  the  Hematococcus  binalis,  whose  various  stages  of 
cell-multiplication  are  shown  in  Fig.  15.  In  many  other  instances,  the  cells 
of  successive  generations,  without  losing  their  individuality,  are  held  together 


112  ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 

by  a  consistent  mucous  envelope  ;  so  that  we  may  find  two,  three,  four,  or  a 
larger  number,  clustered  together  within  a  well-defined  investment,  which  has 
tenacity  enough  to  prevent  them  from  separating.  Of  this  we  have  a  good 
example  in  Coccochloris  cystifera  (Fig.  16) ;  and  a  yet  more  remarkable  one 
in  Hematococcus  sanguineus  (Fig.  17).  The  cells  forming  such  masses  of 
vegetation  may  be  likened  to  those  of  Cartilage,  which  are  similarly  enveloped 
by  an  intercellular  substance,  and  which  present  the  same  binary  method  of 
multiplication  (§  129).  In  the  Confervas  we  find  the  cells,  which  are  succes- 
sively produced  in  this  manner,  remaining  in  connection  with  each  other,  so 
as  to  form  articulated  filaments.  The  terminal  cell  of  each  filament  is  con- 
tinually undergoing  subdivision  in  the  manner  just  described,  and  thus  the 
filament  is  elongated  ;  whilst  other  cells  produce  regular  reproductive  granules, 
which  are  set  free  by  an  opening  that  forms  in  the  cell-wall,  and  which  devel- 
ope  themselves  into  new  individuals  without  any  further  aid  from  the  parent 
structure,  in  the  manner  already  described.  The  difference  between  these 
two  modes  of  propagation  seems  to  have  reference  to  the  age  and  degree  of 
development  of  the  cell ;  the  binary  division  being  characteristic  of  cells  which 
are  in  a  growing  state,  and  being  destined  to  extend  the  original  structure; 
whilst  the  formation  and' emission  of  a  number  of  reproductive  granules  is  the 
function  of  the  mature  cell,  and  is  destined  to  give  origin  to  new  individuals. 
These  processes  are  analogous  in  the  higher  plants,  the  first  to  the  develop- 
ment of  leaf-buds,  the  second  to  the  production  of  seeds.  In  the  Nostoc  we 
find  the  moniliform  filaments,  which  are  composed  of  a  linear  series  of  cells, 
invested  by  dense  gelatinous  sheaths  of  definite  extent,  looking  almost  like 

Fig.  17. 


Hematococcus  sanguineus  in  various  stages  of  development ,— a,  a  single  cell,  enclosed  in  its  mucous 
envelope  ;  6,  c,  clusters  formed  by  division  of  parent-cell ;  d,  more  numerous  cluster,  its  component  cells 
in  various  stages  of  division  ;  «,  large  mass  of  young  cells,  formed  by  continuance  of  the  same  process. 
and  enclosed  within  common  gelatinous  envelope. 

large  parent-cells  (Fig.  18,  B)  ;  and  the  extension  of  the  filaments  may  so  dis- 
tend their  sheaths  as  to  give  them  the  appearance  of  capacious  globular  cells 
(Fig.  18,  A).  There  is  reason  to  believe  that  the  long  convoluted  filaments 
then  separate  into  a  cluster  of  shorter  ones,  each  having  its  own  share  of  the 
mucous  envelope. 

126.  The  history  of  the  Animal  cell,  in  its  simplest  form,  is  precisely  that 
of  the  Vegetable  cell  of  the  lowest  kind.     It  lives  for  itself  and  by  itself,  and 


DEVELOPMENT  AND  MULTIPLICATION  OF  CELLS. 


113 


is  dependent  upon  nothingjbut  a  due  supply  of  nutriment  and  a  proper  tem- 
perature for  the  continuance  of  its  growth,  and  for  the  due  performance  of  its 
functions,  until  its  term  of  life  is  expired.     It  originates  from  a  reproductive 
granule,  previously  formed  by  some  other  cell ;  this  granule  attracts  to  itself, 
assimilates,  and  organizes,  the  particles  of  the  nutrient  fluid  in  its  neighbour- 
hood ;   and  converts  some  of  them  into  the  substance  of  the  cell-wall,  whilst 
it  draws  others  into  the  cavity  of  the  cell.     In  this  manner  the  cell  gradually 
increases  in  size ;  and  whilst  it  is 
itself  approaching  the  term  of  its 
life,  it  usually  makes  preparation 
for  its  renewal,  by  the   develop- 
ment of  reproductive  granules  in 
its  interior  ;   which  may  become 
the  germs  of  new  cells,  when  set 
free  from  the  cavity  of  the  parent, 
by  the  rupture   of  its  cell-wall. — 
There  is  an  important  difference, 
however,  in   the  endowments    of 
the   Animal   and   Vegetable    cell. 
The  latter  can  in  general  obtain 
its  nutriment,  and  the  materials  for 
its  secretion,  by  itself  combining 
inorganic    elements    into    organic 
compounds.     The    former,    how- 
ever, is   totally  destitute   of   this 
power  ;  it  can  produce  no  organic 
compound,    and   we  have    yet  to 
learn  how  far  its   power  of  con- 
verting one  compound   into    an- 
other  may  extend ;  its   chief  en- 
dowment seems   to  be  that  of  at- 
tracting or  drawing  to  itself  some 
of  the  various  substances,  which 
are  contained  in  the  nutritive  fluid 
in  relation  with  it.     This  fluid,  as 
we  shall  hereafter  see,  is  a  mixture 
of  a  great  number  of  components  ; 
and  different  sets  of  cells   appear 
destined  severally  to  appropriate 
these,  just  as  the  different  cells  of 
a   parti-coloured  flower  have  the 
power  of  drawing   to  themselves 
the  element  of  their  several  colour- 
ing matters.     As  far  as  it  is  yet 
known,  however,  the  composition 
of  the  cell-wall  is  everywhere  the 
same,  being  that  of  Proteine.     It 
is  in  the  nature  of  the  contents  of 
the  cell  (as  among  the  cells  of  Plants),  that  the  greatest  diversity  exists  ;  and 
we  shall  find  that  the  purposes  of  the  different  groups  of  cells,  in  the  general 
economy  of  the  Animal,  depend  upon  the  nature  of  the  products  they  secrete, 
and  upon  the  length  of  time  during  which  these  products  are  retained  by  them. 
127.  Of  the  general  account  just  given,  the   development  of  certain  cells, 
which  float  in  the  Chyle,  Lymph,  and  Blood,  may  be  adduced  as  an  exam- 
ple ;  these,  which  are  known  as  the  Chyle  arid  Lymph  corpuscles,  and  as  the 

10* 


Nostoc  macrosporum:—A,  a  long  convoluted  filament, 
composed  of  linear  series  of  minute  cells,  enclosed  in 
general  mucous  envelope ;  B,  group  of  shorter  fila- 
ments, each  with  its  own  gelatinous  envelope,  pro- 
bably formed  by  the  division  of  the  preceding. 


114 


ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 


Colourless  corpuscles  of  the  Blood,  have  no  single  nucleus,  but  contain  seve- 
ral scattered  particles,  each  of  which  seems  to  be  a  reproductive  granule ;  and 
they  emit  these  by  the  bursting  or  liquefaction  of  their  wall, — a  change  which 
may  be  effected  in  them  at  any  time,  by  the  application  of  chemical  reagents. 
The  granules  thus  set  free  appear  to  float  in  the  current  of  fluid,  and  to  be  in 
their  turn  developed  into  cells  at  the  expense  of  the  materials  it  affords.  The 
exudations  of  the  plastic  or  organizable  matter  of  the  blood,  which  are  thrown 
out  upon  inflamed  or  wounded  surfaces,  appear  to  contain  some  of  these  gra- 
nules ;  for  similar  cells  are  speedily  developed  in  these  exudations,  giving  rise, 
in  their  turn,  to  new  generations,  when  their  own  term  of  life  is  ended. 

128.  In  general,  however,  we  find  the  cells  of  Animal  tissues  furnished  with 
a  nucleus;  and  this  may  be  formed,  as  in  Plants,  either  at  an  early  stage  of 
the  development  of  the  cell,  by  the  aggregation  of  minute  molecules  around 
the  original  granular  germ  (which  germ  seems  to  be  the  nucleolus  of  some 
authors) ;  or  after  the  cell  has  attained  its  full  size.  The  nucleus,  where  it 
exists,  appears  to  be  the  chief  instrument  in  the  functions  of  the  cell;  the 
cell-membrane  probably  having  little  else,  than  the  mechanical  office  of 
bounding  or  limiting  the  contents  of  the  cell.  In  some  cells  the  function  is 
restricted  to  the  attraction  of  certain  constituents,  by  which  the  cavity  of  the 
cell  is  filled.  These  constituents  may  be  of  a  nature  to  give  solidity  and 
permanence  to  the  texture ;  thus,  the  cells  of  the  Epidermis  are  strengthened 
by  a  deposit  of  horny  matter,  those  of  Shell  by  the  deposit  of  carbonate  of 
lime;  those  of  Bones  and  Teeth  by  a  mixture  of  mineral  and  earthy  matter, 
&c.  Or  they  may  be  of  a  fluid  nature,  readily  passing  into  decomposition, 
and  destined  to  be  retained  only  for  a  short  time ;  being  given  up  again  by 
the  rupture  or  liquefaction  of  the  cell-wall,  as  in  the  case  with  the  cells  of 
Glandular  structures  in  general.  Now  such  cells  do  not  usually  reproduce 
themselves,  but  successive  crops  of  them  are  generated  as  fast  as  required 
from  other  sources;  and  the  function  of  their  nuclei  appears  to  be  limited  to 
their  chemical  agency  upon  the  materials  which  they  select.  It  would  seem, 

in  fact,  as  if  the  direction  of  the  nisus 

Fig.  19-  or  power  of  the  cell  to  this  object, 

prevented  the  exercise  of  its  repro- 
ductive powers  ;  and  where  we  find 
these  last  most  strongly  manifested, 
it  is  usually  observable  that  the  cell 
performs  little  or  no  other  duty. 

129.  In  the  endogenous  develop- 
ment of  Animal  cells,  the  nucleus 
seems  always  to  perform  an  important 
part,  where  it  has  a  distinct  existence. 
In  many  cases,  the  multiplication  can 
be  clearly  perceived  to  take  place,  by 
the  division  of  the  nucleus  into  two 
or  more  portions ;  each  part  giving 
origin  to  a  new  cell.  This  seems  to 
be  the  case,  for  example,  in  the  ordi- 
nary production  of  Cartilage-cells ;  for 
on  examining  sections  of  cartilage  that 
is  undergoing  rapid  extension,  we  find 
groups  of  cells,  in  all  respects  corre- 
sponding with  those  of  the  simple 
cellular  plants,  which  can  be  seen  to 
increase  in  the  same  way.  Thus  in 
Fig.  19,  which  represents  a  section  of  one  of  the  branchial  cartilages  of  the 


Section  of  branchial  Cartilage  of  young  Tadpole  ; 
a,  b,  c,  intercellular  substance ;  d,  single  nucleus;  e, 
nucleus  dividing  into  two ;  d',  e',  two  nuclei  in  one 
cell,  formed  by  division  of  single  nucleus;/,  second- 
ary cell,  forming  around  nucleus  g;  h,  two  nuclei 
within  single  secondary  cell ;  i,  three  secondary 
cells,  within  one  primary  cell. 


DEVELOPMENT  AND  METAMORPHOSES  OF  CELLS. 


115 


Fig.  20. 


Tadpole,  we  observe,  within  the  large  parent-cells  that  are  held  together  by 
intercellular  substance,  «,  b,  c,  secondary  cells  in  various  stages  of  develop- 
ment: at  d,  the  nucleus  is  single  ;  at  e  it  is  dividing  into  two  ;  in  the  adjoining 
cell,  the  division  into  two  nuclei,  d'  and  e',  is  complete ;  at  h,  two  such  nuclei 
are  inclosed  within  a  common  cell-membrane ;  at  i,  we  see  three  new  cells 
(one  of  them  elongated,  and  itself  probably  about  to  subdivide)  within  the 
parent ;  and  in  each  of  the  two  groups  at  the  top  and  bottom  of  the  figure, 
we  have  four  small  cells,  now  separated  by  partitions  of  intercellular  sub- 
stance, but  having  manifestly  originated  from  one  parent  cell.  (See  also  Fig. 
43.) 

130.  In  other  cases,  the  granular  nucleus  subdivides  into  a  greater  number 
of  parts,  so  as  to  give  origin  to  a  cluster  of  young  cells,  which  may  completely 
fill  the  parent-cell ;  various  stages  of 
this  process    are   seen   in  Fig.  20. 
This  process  seems  to  be  adopted, 
where  rapid  multiplication  is  need- 
ed, and  where  the  new  or  secondary 
cells  are  not  destined  to  possess  any 
great   duration.      The   same  nuclei 
or  "germinal  centres,"  continually 
drawing    new    materials    from    the 
blood,  may  thus  develope  many  suc- 
cessive crops  of  new  cells,  when  an 
opening  in  the  wall  of  the  parent- 
cell  permits  them  to  be  discharged 
as  fast  as  they  are  formed ;  and  this 
we  shall  find  to  be  the  way  in  which 
the  cells  of  the  secreting  structures 
are  developed  within  the  glandular 
follicles.    According  to  Dr.  Barry,  it 
is  not  uncommon  for  several  annuli 
of  young  cells  to  be  generated  from 
the  periphery  of  the  nucleus,  and  to 
attain  a  certain  degree  of  develop- 
ment within  the  parent  cell,  the  first- 
formed  being  the  largest,  as  shown 
in  Plate  I.,  Fig.  10,  «,  b;  some  of 
these,  moreover,  having  distinct  nu- 
clei of  their  own,  from  which  a  third 
generation  is  being  developed  on  the 
same  plan  (Fig.  12,6);  and  yet  for  all  these  to  disappear  by  liquefaction, 
leaving  the  cavity  of  the  parent-cell  unoccupied,  except  by  a  pair  of  cells  ori- 
ginating in  the  central  part  of  the  nucleus  (Fig.  13).     If  this  account  be  cor- 
rect, it  is  probable  that  these  temporary  cells  perform  the  office  of  preparing 
the  contents  of  the  parent-cell  for  the  nutrition  of  the   offspring  which  is  to 
succeed  it ;  and  each  of  these  twin  cells,  in  its  turn,  going  through  the  same 
series  of  changes  (Fig.  14),  gives  origin  to   a  new  pair;   the   continuance  of 
which  process  generates  a  cluster.    This  is  the  mode,  according  to  Dr.  Barry, 
in  which  the  first  cells  of  the  embryo  are  developed  into  the  "  mulberry  mass" 
(Fig.  15),  by  whose  subsequent  development  and  metamorphoses,  the  tissues 
and  organs  of  the  fetus  are  progressively  evolved. 

131.  Notwithstanding  the  numerous  varieties  that  exist,  in  the  particular 
modes  in  which  the  cells  are  developed,  it  seems  to  be  well  established  as  a 
simple  general  principle,  that  all  cells  take  their  origin  in  germs  prepared  by 
a  previously-existing  cell;  and  that  these  germs  may  be  developed,  either 


Endogenous  cell-growth  in  cells  of  a  meliceritous 
tumour;  a,  cells  presenting  nuclei  in  various  stages 
of  development  into  a  new  generation;  &,  parent- 
cell  filled  with  a  new  generation  of  young  cells, 
which  have  originated  from  the  granules  of  the  nu- 
cleus. 


116          ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 

within  the  parent-cell,  or  when  set  free  by  its  rupture.  The  difference  ob- 
servable in  the  several  cases  that  have  been  enumerated,  and  in  others  that 
might  be  mentioned,  seems  to  have  reference  chiefly  to  the  degree  of  prepara- 
tion that  is  effected  in  the  nutriment  with  which  the  young  cells  are  supplied; 
— some  drawing  it  directly  from  the  blood ;  whilst  others  receive  it  through 
the  medium  of  the  parent-cell,  which  probably  exerts  a  certain  degree  of  pre- 
paring influence  upon  it; — and  others,  again,  requiring  a  further  preparation 
to  be  effected,  by  the  elaborating  or  assimilating  influence  of  a  group  of  tem- 
porary cells,  expressly  developed  for  this  purpose. 

132.  We  shall  find,  as  we  proceed,  that  all  the  tissues  most  actively  con- 
cerned in  the   maintenance  of  the  Vital  functions  of  the  Human  body, — both 
those  of  a  Vegetative  nature,  and  those   which  are  peculiarly  Animal,  are 
composed  of  Cells  which   have  undergone  no  considerable  metamorphosis, 
and  of  which  one  generation  is  produced  after  another  with  a  rapidity  that  is 
proportioned  to  the  activity  of  the  function.     But  there  are  other  structures 
of  an  accessory  character,  in  which  a  departure  from  the  original  type  is  to 
be  traced,  sometimes  so  complete,  as  to  prevent  their  real  nature  from  being 
understood,  except  by  a  very  careful  scrutiny  into  their  history.     This  depart- 
ure is  the  result  of  various  kinds  of  metamorphosis  of  the  cells  and  of  their 
nuclei ;  of  which  the  following  are  the  principal.     The  cells,  originally  sphe- 
roidal, oval,  or  polygonal,  may  become  elongated  to   such  a  degree,  as  to  as- 
sume the  spindle  or  fusiform  shape ;  thus  resembling  woody  fibres.     They 
may  at  the  same  time  lose   their  nuclei ;  and  their  cavities  may  be  occupied 
by  internal   deposits,  so  that  they  may  be  mistaken  for  solid   fibres.     Such 
fusiform  cells  are  often  found  in  exudation-membranes. — Again,  the  cells  may 
shoot  out  prolongations,  either  in  a  radiating  manner,  so  that  they  assume  a 
stellate  form  ;  or  in  no  definite  direction,  so  that  their  shape  becomes  altogether 
irregular.     Such  forms  are  seen   amongst  the  pigment-cells  of  the  Batrachia 
and  Fishes,  and  among  the  vesicles  of  the  gray  matter  of  the  nervous  system. 
Further,  the  original  boundaries  of  the  cells  may  be  altogether  lost,  by  their 
coalescence  with  each  other.     This   is  the  case  with  many  membranes  that 
seem  to  have  originated  in  a  layer  of  flat  cells  ;  the  situation  of  which  is  rather 
to  be  traced  by  their  nuclei,  than  by  their  former  boundaries,  which  have  alto- 
gether disappeared.     It  is  often  the  case,  too,  with  the  horny  cells,  of  which 
the  nails,  hoof,  &c.,  are  made  up  ;  and  still  more  with  the  cells  of  shell,  bone, 
tooth,  &c.,  which  have  been  consolidated  by  the  deposition  of  a  calcifying 
deposit. — Lastly,  the  character  of  the  original  cell  may  be  completely  altered 
by  a  solution  in  the  continuity  of  its  wall,  in  one  or  more  spots,  so  that  its 
cavity  is  laid  open,  and  coalesces  with  some  other.     In  this  manner,  by  the 
disappearance  of   the    partitions   between    cells   laid  in    apposition,  end  to 
end,  may  be  formed  a  tube ;  and  this  tube  may  coalesce  with  others,  in  like 
manner,  so   as   to   form  a  capillary  network  for  the  circulation  of  the  blood. 
Or  the  tube  may  form  a  simple  straight  fibre  ;  and  the  nuclei  of  its  component 
cells  may  give  origin  to  a  new  deposit,  either  in  an  amorphous  condition,  as 
in  the  fibrous  portion  of  nervous  tissue,  or  in  the  form  of  an  aggregation  of 
new  cells,  as  in  the  most  perfect  kind  of  muscular  fibre.     In  these  cases,  also, 
the  original  composition  of  the  tubes  may  be  frequently  traced  by  the  nuclei 
that  remain  in  their  interior.     In  the  follicles  of  glands,  the  solution  of  con- 
tinuity takes  place  at  one  point  only,  which  establishes  a  communication  be- 
tween the  cavity  of  the  parent-cell,  and  some  canal  by  which  its  contents  may 
be  discharged  ;  and  the  nucleus  situated  at  the  blind  or  closed  extremity  of  the 
follicle,  may  then  continue  to  form  successive  generations  of  secondary  cells, 
which  are  discharged  by  this  outlet. 

133.  The  metamorphoses  of  the  nucleus  are  not  less   important,  though 
not  as  numerous.    In  some  instances  we  find  it  sending  out  radiating  prolonga- 


FIBROUS  TISSUES. BASEMENT  MEMBRANE.  117 

tions,  so  that  it  assumes  a  stellate  form,  like  that  of  the  cells  of  the  Geranium- 
petal  ;  this  seems  to  be  the  case  in  regard  to  the  nuclei  of  the  Bone-cells. — 
In  other  instances  it  appears  to  resolve  itself  into  a  fasciculus  of  fibres  ;  and 
this  is  stated  by  Henle  to  be  the  origin  of  the  yellow  fibrous  tissue. — Further, 
it  may  separate  into  a  number  of  distinct  fibres,  each  composed  (like  those  of 
the  Nostoc,  Fig.  18,)  of  a  linear  aggregation  of  granules;  it  seems  to  be  in 
this  manner,  that  the  tubuli  of  the  Dental  structure  are  formed. — Lastly,  it 
may  disperse  itself  still  more  completely  into  its  component  granules ;  by  the 
reunion  of  which,  certain  peculiar  vibrating  filaments  (the  so-called  Sperma- 
tozoa) may  be  formed,  possessing  motor  powers  analogous  to  those  of  the 
Oscillatoriae  and  other  corresponding  filamentous  products  of  humble  Crypto- 
gamic  vegetation,  but  destined  to  perform  most  important  offices  in  the  func- 
tion of  Reproduction. 

134.  We  have  seen  that,  in  the  Vegetable  structure,  the  component  cells, 
tubes,  woody  fibres  (or  elongated  cells),  &c.,  are  held  together  by  simple  ad- 
hesion ;  a  gummy  intercellular  substance,  which  answers  the  purpose  of  a 
cement,  being  often  interposed,  sometimes  in  considerable  quantity.     But  in 
the  Animal  body,  of  which  the  several  parts  are  destined  to  move  with  greater 
or  less  freedom  upon  one  another,  the  aggregations  of  cells  that  make  up  its 
chief  part,  either  in  their  original  or  in  their  metamorphic  form,  could  not  be 
held  together  in  their  constantly-varying  relative  positions,  without  some  in- 
tervening substance  of  an  altogether  different  character.     It  must  be  capable 
of  resisting  tension  with  considerable  firmness   and  elasticity  ;  it  must  admit 
free  movement  of  the  several  parts  upon  one  another  ;  and  it  must  still  hold 
them  sufficiently  close  together  to  resist  any  injurious  strain  upon  the  deli- 
cate vessels,  nerves,  &c.,  which  pass  from  one  to  another,  as  well  as  to  pre- 
vent any  permanent  displacement.     Now  all  these  offices  are  performed  in  a 
remarkably  complete  degree,  by  the  Areolar  Tissue  (§  138);  the  reason  of 
whose  restriction  to  the  Animal  kingdom  is  thus  evident.     And  as  necessity 
arises,  in  certain  parts,  for  tissues  which  shall  exercise  a  still  greater  power 
of  resistance  to  tension,  and  which  shall  thus  communicate  motion  (as  in  the 
case  of  Tendons),  or  shall  bind  together  organs  that  require  to  be  united  (as 
in  the  case  of  Ligaments  and  Fibrous  Membranes),  so  do  we  find  peculiar 
tissues  developed  that  shall  serve  these  purposes  in  the  most  effectual  manner. 
Hence  these  tissues  also,  although  not  endowed  with  any  properties  that  are 
peculiarly  animal,  are  nevertheless  restricted  to  the  Animal  Kingdom, — as 
completely  as   are  the   Muscular  and  Nervous  Tissues,  which  make  up  the 
essential  parts  of  the  apparatus  of  Animal  Life. 

135.  That  all  the  Animal  tissues  are  in  the  first  instance  developed  from 
Cells,  was  the  doctrine  put  forth  by  Schwann,  who  first  attempted  to  gene- 
ralize on  this  subject.     By  subsequent  research,  however,  it  has  been  shown 
that  this  statement  was  too  hasty ;  and  that,  although  many  tissues  retain  their 
origin  cellular  type,  through  the  whole  of  life,  and  many  more  are  evidently 
generated  from  Cells  and  are  subsequently  metamorphosed,  there  are  some, 
in  which  no  other  cell-agency  can  be  traced,  than  that  concerned  in  the  pre- 
paration of  the  plastic  material. — This  would  appear  to  be  the  case,  in  certain 
forms  of  the  very  delicate  structureless  lamella  of  membrane,  now  known 
under  the  name  of  Basement  or  Primary  Membrane,  which  is  found  beneath 
the  Epidermis  or  Epithelium,  on  all  the  free  surfaces  of  the  body.     In  many 
specimens  of  this  membrane,  no  vestige  of  cell-structure  can  be  seen ;  and  it 
would  rather  appear  to  resemble  that,  of  which  the  walls  of  the  cells  are  them- 
selves constituted.*     In  some  instances,  it  presents  a  somewhat  granular  ap- 

*  See  a  Paper  by  the  Author,  on  the  Microscopic  Structure  of  Shells,  &c.,  in  the  Annals 
of  Natural  History,  Dec.  1843.     The  inner  layer  of  the  Shells  of  Mollusca,  after  treatment 


118 


ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 


pearance ;  and  it  is  then  supposed  by  Henle  to  consist  of  the  coalesced  nuclei 
of  cells,  whose  development  has  been  arrested :  or,  in  other  words,  such 
Basement-Membrane  is  formed  by  the  consolidation  of  a  layer  of  the  plastic 
element,  that  includes  a  large  number  of  the  granules,  which  may  serve  for 
the  development  of  new  cells.  Other  forms  of  the  Basement-Membrane  can 
be  distinctly  seen  to  consist  of  flattened  polygonal  cells,  closely  adherent  by 
their  edges  ;  every  one  having  its  own  granular  nucleus.* — It  seems  to  be  from 
these  granular  germs,  sometimes  scattered  through  the  membrane,  and  in  other 
instances  collected  into  certain  spots,  that  the  cells  of  the  superjacent  Epithe- 
lium or  Epidermis  take  their  origin ;  and  if  this  be  the  case,  we  must  regard 
the  Basement-Membrane  as  a  transitional  rather  than  as  a  permanent  struc- 
ture,— continually  disintegrating,  and  yielding  up  its  contained  cell-germs  on 
its  free  surface,  and  as  constantly  being  renewed  from  the  blood  beneath. 
For  the  epidermic  structures  appear  to  constitute  an  exception  to  the  general 
rule,  that  the  Tissues  reproduce  themselves ;  since  they  are  cast  off,  without 
leaving  their  germs  behind  them  ;  and  the  cells  which  replace  them  must  be 
derived  from  new  germs,  more  directly  supplied  from  the  blood  than  is  else- 
where the  case.  In  the  ease  of  the  other  tissues,  whose  disintegration  takes 
place  inter stitially  (so  to  speak),  it  would  seem  probable  that,  in  the  very 
act  of  the  dissolution  of  the  parent-structure,  the  germs  of  the  new  structures 
destined  to  replace  it  are  set  free ;  as  happens  in  the  reproduction  of  the  sim- 
ple Cellular  Plants. 

136.  It  would  seem  doubtful,  also,  in  regard  to  the  simple  Fibrous  tissues, 
whether  they  are  generated  by  a  metamorphosis  of  Cells,  in  the  same  manner 
as  the  Osseous,  Muscular  and  Nervous ;  or  whether  they  are  not  produced, 
like  the  Basement-Membrane,  by  the  consolidation  of  a  plastic  fluid,  which 
has  been  elaborated  by  cells.  The  latter  view  is  the  one  which  the  Author 
has  been  led  to  regard  as  most  probable,  from  the  results  of  his  own  observa- 
tions, coupled  with  those  of  Messrs.  Addison  and  Gulliver  previously  adverted 
to.  The  Membrane  of  the  Egg-shell,  whose  structure  has  been  already 
described  (§  118),  appears  to  him  to  have  essentially  the  same  character  with 
the  simple  Fibrous  tissues,  which  it  resembles  also  in  its  tenacity  (compare 
Fig.  11  with  Fig.  22) ;  whilst  its  origin  can  scarcely  be  supposed  to  be  different 
from  that  of  the  fibrous  network  in  the  buffy  coat  of  the  Blood,  or  in  the 
bands  formed  by  the  coagulation  of  Lymph  upon  an 
Fig.  21.  inflamed  surface.  The  occasional  vestiges  of  cells, 

which  the  purely  Fibrous  tissues  display  (§  138), 
and  which  have  been  adduced  in  support  of  their 
cellular  origin,  are  not  inconsistent  with  this  view. 
For  in  the  reticulated  structures  just  adverted  to, 
certain  bodies  are  seen,  which  appear  to  be  nuclei 
or  imperfectly-formed  cells  (originating  probably  in 
germs  set  free  by  the  rupture  of  the  colourless  cor- 
puscles of  the  blood),  and  which  closely  correspond 
with  the  nuclear  corpuscles  that  may  be  brought 
into  view  in  the  Fibrous  tissue.  Mr.  Addison's 
observation,  too, — that  the  fibres  formed  in  the 
Liquor  Sanguinis,  and  in  plastic  exudations,  during 
coagulation,  often  seem  to  radiate  from  the  remains 
of  the  white  corpuscles  that  have  ruptured,  or  from 
the  little  aggregations  of  granules  they  contained, — 
gives  the  explanation  of  several  of  the  appearances,  which  have  led  to  the 

with  a  dilute  acid,  yields  specimens  of  Basement-Membrane,  in  a  form  well  adapted  for 
examination. 

*  See  J.  Goodsir,  in  "  Anatomical  and  Pathological  Observations,"  Chap.  I. 


Colourless  cells,  with  ac- 
tive molecules,  and  fibres,  of 
fibrine,  from  Herpes  labialis. 


CLASSIFICATION  OF  HUMAN  ELEMENTARY  TISSUES.  119 

belief  in  the  production  of  the  Areolar  and  other  fibrous  tissues  by  Cell-trans- 
formation.— An  additional  argument  in  favour  of  this  view,  may  be  found  in 
the  appearances  presented  by  the  semi-fibrous  Cartilages.  In  the  Cartilages 
of  the  ribs,  for  instance,  a  more  or  less  distinct  fibrous  appearance  may  often 
be  seen  in  the  intercellular  substance,  which  is  elsewhere  quite  homogene- 
ous ;  this  appearance  is  sometimes  so  faint,  that  it  might  be  considered  as 
an  illusion,  occasioned  by  the  manipulation  to  which  the  section  has  been 
subjected;  but  it  is  often  so  well  defined,  as  to  present  the  aspect  of  true 
fibrous  tissue.  No  indication  of  the  direct  operation  of  cells,  in  the  develop- 
ment of  these  fibres,  has  ever  been  witnessed ;  and  we  can  scarcely  do  other- 
wise than  regard  them  as  produced  by  the  regular  arrangement  and  con- 
solidation of  the  particles  of  the  intercellular  substance,  in  virtue  of  its  own 
inherent  powers. 

137.  The  following  arrangement  of  the  Human  Tissues  will  be  here  adopt- 
ed as  expressing  their  respective  relations  to  the  fundamental  elements  which 
have  been  now  described ;  namely,  simple  Membrane,  fibres,  and  Cells. 

a.  Simple  Membranous  Tissues. — Of  these  there  are  scarcely  any  examples 
in  the  Human  body,  except  in  the  posterior  layer  of  the  cornea  and  thec  cap- 
sule of  the  crystalline  lens.    The  membranous  element  is  largely  found,  how- 
ever, in  the  compound  Membrane-fibrous  tissues. 

b.  Simple  Fibrous  Tissues. — Under  this  head  may  be  classed  the  White 
and  Yellow  Fibrous  Tissues,  and  Areolar  Tissue. 

c.  Simple  Cells  floating  separately  and  freely  in  the  fluids.     Such  are  the 
Corpuscles  of  the  Blood,  Chyle,  and  Lymph. 

d.  Simple  Cells  developed  on  the  free  surfaces  of  the  body.     Such  are  the 
Epidermis  and  Epithelium. 

e.  Compound  Membrano-Fibrous  Tissues,  composed  of  a  layer  of  simple 
membrane,  developing  Cells  on  its  free  surface,  and  united  on  the  other  to  a 
fibrous  or  areolar  structure. — Of  this  kind  are  the  Skin,  the  Mucous  Mem- 
branes, the  Serous  and  Synovial  membranes,  the  lining  membranes  of  the 
Blood-vessels,  &c. 

f.  Simple  Isolated  Cells,  forming  solid  tissues  by  their  aggregation. — Un- 
der this  head  we  may  rank  the  Fat-cells,  the  Vesicles  of  Gray  Nervous  matter,* 
the  Absorbent  cells  at  the  extremities  of  the  Intestinal  villi,  and  the  cellular 
parenchyma  of  the  Spleen  and  similar  bodies ;  the  cells  being  held  together, 
in  all  these  cases,  by  the  blood-vessels  and  areolar  tissue  which  pass  in  amongst 
them.     In  Cartilage,  and  certain  tissues  allied  to  it  in  structure,  the  cells  are 
united  by  intercellular  substance,  which  may  be  quite  homogeneous,  or  may 
have  a  fibrous  character. 

g.  Sclerous  or  Hard  Tissues,  in  which  the  cells  have  been  consolidated  by 
internal  deposit,  and  have  more  or  less  completely  coalesced  with  each  other. — 
Such  is  the  case  with  the  substance  of  Hair,  Nails,  &c.,  which  may  be  more 
properly  ranked  under  the  Epidemic  Tissues  ;  but  the  result  is  most  charac- 
teristically seen  in  Bones  and  Teeth. 

h.  Simple  Tubular  Tissues,  formed  by  the  coalescence  of  the  cavities  of 
cells,  without  secondary  internal  deposit. — The  Capillary  blood-vessels,  and 
probably  also  the  smallest  Lymphatics  and  Lacteals,  seem  to  be  formed  in  this 
manner. 

i.  Compound  Tubular  Tissues ;  in  which,  subsequently  to  the  coalescence 
of  the  original  cells,  a  new  deposit  has  taken  place  within  their  cavities. — In 
the  tubuli  of  the  White  or  Medullary  Nervous  matter,  and  in  those  of  the  least 

*  As  it  is  undesirable  to  separate  from  each  other  the  descriptions  of  the  two  elementary 
forms  of  Nervous  structure,  on  account  of  their  close  functional  connection,  the  gray  or  vesi- 
cular nervous  matter  will  be  described  together  with  the  white  or  tubular,  in  the  last  section 
of  this  chapter. 


120  ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 

perfect  form  of  Muscular  Fibre,  the  secondary  deposit  has  only  a  granular  or 
amorphous  character ;  but  in  the  striated  Muscular  fibre,  it  is  composed  of 
minute  cells. 

As  it  is  not  requisite  here  to  say  anything  further  of  simple  Elementary 
Membrane,  we  shall  at  once  pass  on  to  the  second  group  of  Tissues  ;  one  of 
great  extent  and  importance  in  the  bodies  of  all  the  higher  Animals. 

4.  Of  the  Simple  Fibrous  Tissues. 

138.  A  very  large  proportion  of  the  body,  in  the  higher  Animals,  is  com- 
posed of  a  tissue,  to  which  the  name  of  "  Cellular"  was  formerly  given.  This 
term,  however,  is  so  much  more  applicable  to  those  structures,  which  are 
composed  of  a  congeries  of  distinct  Cells,  and  the  use  of  it  for  both  purposes 
is  likely  to  engender  so  much  confusion,  that  it  is  to  be  wished  that  its  appli- 
cation to  this  purpose  should  be  altogether  discontinued. — The  tissue  in  ques- 
tion, now  generally  designated  the  Areolar,  is  found,  when  examined  under 
the  Microscope,  to  consist  of  a  network  of  minute  fibres  and  bands,  inter- 
woven in  every  direction,  so  as  to  leave  innumerable  interstices,  which  com- 
municate with  each  other.  The  two  kinds 
of  Fibrous  tissue,  which  elsewhere  exist  se- 
parately,— the  white,  and  the  yellow, — may 
be  detected  in  Areolar  tissue ;  as  was  first 
pointed  out  by  Messrs.  Todd  and  Bowman. 
The  White  presents  itself  in  the  form  of 
inelastic  bands  of  variable  size,  the  largest 
1 -500th  of  an  inch  in  breadth,  somewhat 
wavy  in  their  direction,  and  marked  longitu- 
dinally by  numerous  streaks  (Fig.  23);  these 
streaks  are  rather  the  indications  of  a  longi- 
tudinal creasing,  than  a  true  separation  into 
component  fibres ;  for  it  is  impossible  by  any 

ArrangementofFibresin  Areolar  Tissue-      art  tO  tGEr  UP  *e  band  into  filaments  of  a  de- 
Magnified  135  diameters.  terminate  size,  although  it  manifests  a  decided 
tendency  to   tear   lengthways.     Sometimes, 

however,  distinct  fibres  may  be  traced,  whose  diameter  varies  from  about 
l-15,000th  to  l-20,000th  of  an  inch.  The  Yellow  fibrous  element  exists  in 
the  form  of  long,  single,  elastic,  branched  filaments,  with  a  dark  decided  bor- 
der, and  disposed  to  curl  when  not  put  on  the  stretch  (Fig.  24).  These  inter- 
lace with  the  others,  but  appear  to  have  no  continuity  of  substance  with  them. 
They  are  for  the  most  part  between  l-5000th  and  1-10,000  of  an  inch  in 
thickness  ;  but  they  are  often  met  with  both  larger  and  smaller.  The  pro- 
portion of  this  element  varies  greatly  in  different  parts ;  being  greatest  in  those 
situations,  in  which  the  greatest  elasticity  is  required.  Sometimes  we  find 
elastic  fibres  passing  round  the  fasciculi  of  the  white  tissue,  constricting  them 
with  distinct  rings,  or  with  a  continuous  spiral ;  such  are  termed  by  Henle 
nucleus-filaments,  from  his  idea  of  their  origin  (§  133).  This  remarkable 
disposition  of  the  yellow  fibres  is  best  seen  in  the  areolar  tissue,  that  accom- 
panies the  arteries  at  the  base  of  the  brain. — The  effect  of  Acetic  acid  upon 
these  two  elements  is  very  different;  the  white  immediately  swells  up,  and 
becomes  transparent;  whilst  the  yellow  remains  unchanged.  This  agent  fre- 
quently brings  into  view  certain  oval  corpuscles,  which  lie  in  the  midst  of 
the  bands  and  threads,  and  which  sometimes  appear  to  have  delicate  prolonga- 
tions among  them.  These  are  usually  supposed  to  be  the  persistent  nuclei 
of  the  cells,  from  which  the  tissue  was  developed  ;  but,  as  already  pointed 
out,  it  is  doubtful  whether  the  fibres  of  this  tissue  are  ever  formed  by  the  me- 


SIMPLE  FIBROUS  TISSUES; AREOLAR  TISSUE.  121 

tamorphosis  of  cells, — their  origin  being  rather,  it  seems  more  probable,  in  the 
fluid  blastema  (§  136). — The  interstices  of  Areolar  tissue  are  filled  during  life 
with  a  fluid,  which  resembles  a  very  dilute  Serum  of  the  blood ;  it  consists 
chiefly  of  water,  but  contains  a  sensible  quantity  of  common  salt  and  albumen, 
and  (when  concentrated)  a  trace  of  alkali  sufficient  to  affect  test-paper.  The  pre- 
sence of  this  fluid  seems  to  result  from  an  act  of  simple  physical  transudation; 
for  it  has  been  found  that,  when  the  serum  of  the  blood  is  made  to  percolate 
through  thin  animal  membranes,  the  water  charged  with  saline  matter  passes 
through  them  much  more  readily  than  the  albumen,  a  part  of  which  is  kept 
back. 

139.  The  great  use  of  Areolar  tissue  appears  to  be,  to  connect  together 
organs  and  parts  of  organs,  which  require  a  certain  degree  of  motion  upon 
one  another :  and  to  envelope,  fix,  and  protect,  the  blood-vessels,  nerves,  and 
lymphatics  with  which  these  organs  are  to  be  supplied.     It  can  scarcely  be 
said  to  enjoy  any  vital  powers,  and  is  connected  solely  with  physical  actions 
(§  134).     It  is  extensible  in  all  directions,  and  very  elastic,  in  virtue  of  the 
physical  arrangement  of  its   elements ;  and  it  possesses  no  contractility,  be- 
yond that  of  the  vessels  which  are  distributed  through  it.     It  cannot  be  said 
to  be  endowed  with  sensibility ;  for  the  nerves  which  it  contains  seem  to  be 
merely  en  route  to  other  organs,  and  not  to  be  distributed  to  its  own  elements. 
And  its  asserted  powers  of  absorption  and  secretion  appertain  rather  to  the 
walls  of  the  capillary  blood-vessels,  than  to  the  threads  and  bands  of  which 
it  is  composed.     It  is   regenerated  more  readily  than   any  other  tissue,  save 
the  Epithelium;  being  produced,  it  would   appear,  by  the  simple  consolida- 
tion of  the  blastema,  that  is  poured  out  (in  the  form  of  organizable  lymph)  in 
situations  where  there  has  been  a  breach  of  substance.     It  is  also  formed  in 
the  effusions  of  a  similar  fluid,  which  are  deposited  on  the  surfaces1,  or  in 
the  substance,  of  inflamed  tissues. — Areolar  tissue  yields  Gelatine  by  boiling ; 
but  this  is  derived  from  the  White   Fibrous   element  only  ;  the  Yellow  not 
being  affected  by  the  process. 

140.  The  White  Fibrous  tissue   exists  alone  in  Ligaments,  Tendons,  Fi- 
brous Membranes,  Aponeuroses,  &c.  ;   where  it  presents  the  same  characters 
as  those  just  described, — except  that  the  bands  are  less  wavy,  and  frequently 
quite  straight,  so  that  it  is  inextensible.     It  receives  very  few  blood-vessels, 
and  still  fewer  nerves  ;  indeed  it  would  seem  that,  in  many  structures  (as  ten- 
dons), it  is  totally  insensible.     It  seems   entirely  destitute  of  any  vital  pro- 
perty ;  and  its  chemical  nature  is  such,  that  it  needs  very  little  interstitial 
change  to  maintain  its  normal  composition.  If^tried,  it  has  not  the  least  tend- 
ency to    putrefy  ;   and  when  moist,  it  resists   the  putrefactive  process  more 
strongly  than  almost  any  of  the  softer  textures.     The  peculiar  and  important 
property  of  this  tissue,  is  its  capability  of  resisting  extension ;  and  we  find  it 
in  situations,  where  a  firm  resistance  is  to  be  made  to  traction.    If  the  traction 
be  applicable  in  one  direction  only,  as  in  Tendons  and  most  Ligaments,  we 
find  the  bundles  of  fibres  or  bands  arranged  side  by  side  ;  but  if  it  be  exerted  in 
various  directions,  the  fasciculi  cross  one  another,  as  in  Fibrous  Membranes. 
The  reparation  of  this  tissue  is  effected  by  the  interposition  of  a  new  substance, 
every  way  similar  to  the  original,  except  that  it  wants  its  peculiar  glistening 
aspect,  and  is  more  bulky  and  transparent. — The  Yellow  Fibrous  tissue  exists 
separately  in  the  middle  coat  of  the  Arteries,  the  Chordae  Vocales,  the  Liga- 
mentum  Nuchae  (of  quadrupeds)  and  the  Ligamenta  subflava ;  and  it  enters 
largely  into  the  composition  of  some  other  parts.     It  differs  remarkably  from 
the  white,  in  the  possession  of  a  high  degree  of  elasticity ;  so  that  the  tissues, 
which  are  composed  of  it  alone,  are  among  the  most  elastic  of  all  known  sub- 
stances.    It  is,  however,  much  more  brittle   than  the  white  ;  and  its  fibrdfc 
usually  exhibit  a  marked  tendency  to  curl  at  their  broken  ends.     Their  size 

11 


122 


ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 


varies  from  about  1 -4000th,  to  1 -24,000th  of  an  inch ;  in  the  ligamenta  sub- 
flava,  it  is  usually  about   l-7500th.     There  is  less  tendency  to  spontaneous 


Fig.  23. 


Fig.  24. 


White  Fibrous  Tissue,  from  Ligament. 
Magnified  65  diameters. 

[Fig.  25. 


Yellow  Fibrous  Tissue,  from  Ligamentum 
Nuchae  of  Calf.    Magnified  65  diameters. 

[Fig.  26. 


The  two  elements  of  Areolar  tissue,  in  their  natural  rela- 
tions to  one  another;  1,  the  white  fibrous  element,  with 
cell-nuclei,  9,  sparingly  visible  in  it ;  2,  the  yellow  fibrous 
element,  showing  the  branching  or  anastomosing  charac- 
ter of  its  fibrillse ;  3,  fibrillae  of  the  yellow  element,  far 
finer  than  the  rest,  but  having  a  similar  curly  character, 
8,  nucleolated  cell-nuclei,  often  seen  apparently  loose. — 
From  the  areolar  tissue  under  the  pectoral  muscle,  mag- 
nified 320  diameters.] 


Development  of  the  Areolar  tissue, 
(white  fibrous  element;)  4,  nucleated 
cells,  of  a  rounded  form  ;  5,  6,  7,  the 
same,  elongated  in  different  degrees, 
and  branching.  At  7,  the  elongated  ex- 
tremities have  joined  others,  and  are 
already  assuming  a  distinctly  fibrous 
character.  (After  Schwann.)] 


decomposition  in  this  tissue,  than  in  almost  any  other  part  of  the  fabric, — at 
dfeast,  of  its  soft  and  moist  portions ;  it  requires  but  little  renovation,  therefore, 
in  the  living  body  ;  and  is  but  very  sparingly  supplied  with  blood-vessels. 


COMPOSITION  AND  PROPERTIES  OF  GELATINE.  123 

141.  The  composition  of  the  White  fibrous  tissues  is  very  different  from 
that  of  most  others;  for  they  yield  to  boiling  water  the  substance  called 
Gelatine,  which  does  not  seem  capable  of  the  same  degree  of  organization 
with  the  Proteine-compounds.  This  may  be  obtained  by  boiling  portions  of 
Skin,  Areolar  tissue,  Serous  membrane,  Tendon,  Ligament,  &c.,  in  water,  for 
some  time  ;  after  which  the  decoction  is  allowed  to  cool,  when  it  solidifies 
into  a  jelly  of  greater  or  less  thickness.  Some  tissues  dissolve  readily  in  this 
manner,  and  little  residual  substance  is  left ;  this  is  especially  the  case  with 
areolar  tissue,  serous  membranes,  and  (in  a  less  degree)  with  skin.  Others 
require  a  long  boiling  for  the  extraction  of  any  Gelatine  ;  and  even  then  it  is 
obtained  in  but  small  quantity  ;  of  this  kind  are  the  Elastic  fibrous  tissue, 
and  some  forms  of  Cartilage.  A  peculiar  modification  of  this  principle 
exists  in  most  of  the  permanent  cartilages ;  and  has  received  the  name  of 
Chondrine.  Gelatine  is  not  found  in  the  blood,  nor  in  any  of  the  healthy 
fluids  ;  and  some  Chemists  are  of  opinion,  that  it  is  rather  a  product  of  the 
operation  practised  to  separate  it,  than  a  real  constituent  of  the  living  solids. 
This  idea  seems  inconsistent,  however,  with  the  fact,  that  the  gelatinous  tis- 
sues will  exhibit,  without  any  preparation,  the  best  marked  of  the  chemical 
properties  which  are  regarded  as  characteristic  of  Gelatine, — that,  namely,  of 
forming  a  peculiar  insoluble  compound  with  Tannin;  and  the  Tanno-Gelatine, 
which  may  be  obtained  by  precipitating  Gelatine  from  a  solution,  and  that 
which  results  from  the  action  of  Tannin  on  Animal  membrane,  appear  to  be 
precisely  analogous  in  every  respect, — save  in  the  presence  of  structure  in  the 
latter,  which  is  absent  in  the  former.  Moreover,  the  Gelatinous  tissues  are 
found,  when  submitted  to  ultimate  analysis,  to  possess  exactly  the  same  com- 
position with  Gelatine  itself.  Still  it  seems  probable,  that  the  arrangement  of 
the  component  particles  is  in  some  degree  altered  by  the  process  of  boiling ; 
for  it  is  found  that,  the  more  distinct  the  fibrous  structure  of  the  tissue,  the 
less  it  is  affected  by  the  prolonged  action  of  cold  water,  and  the  longer  it  must 
be  boiled,  before  it  is  resolved  into  Gelatine. 

a.  Gelatine  is  very  sparingly  soluble  in  cold  water ;  by  contact  with  which,  however,  it  is 
caused  to  swell  up  and  soften.  It  is  readily  dissolved  by  hot  water  ;  and  forms  so  strong  a 
jelly  on  cooling,  that  1  part  in  100  of  water  becomes  a  consistent  solid.  Its  reaction  with 
Tannic  acid  is  so  distinct,  that  1  part  in  5000  of  water  is  at  once  detected  by  infusion  of 
Galls.  The  following  are  the  results  of  four  analyses  of  Gelatine  by  Scherer  and  Mulder. 

SCHEREB. 


Carbon  .  .  .  50-557  50-774  50-048  50-048 

Hydrogen  .  .     6-903  7-152  6-477  6-643 

Nitrogen  .  .18-790  18-320  18-350  18-388 

Oxygen  .  .  23-750  23-754  25-125  24-921 

The  formula  deduced  by  Mulder  from  this  composition,  and  from  the  combinations  of 
Gelatine  with  Tannic  and  Chlorous  acids,  is  13  C,10  H,2  N,  5  0. — When  Gelatine  is  boiled 
for  some  time,  it  loses  its  power  of  forming  a  jelly  on  cooling ;  and  it  is  stated  by  Mulder, 
that  this  is  due  to  its  union  with  an  additional  amount  of  water,  a  true  Hydrate  of  Gelatine 
being  formed  by  the  combination  of  4  Equiv.  of  Gelatine,  with  1  Equiv.  of  Water.  The 
same  product  is  obtained  by  adding  Ammonia  to  the  Chlorite  of  Gelatine,  and  removing  by 
Alcohol  the  Sal  Ammoniac  thus  formed. 

b.  It  is  not  yet  known  how  Gelatine  is  produced  in  the  Animal  body.  There  cannot  be 
a  doubt  that  it  may  be  elaborated  from  Albumen ;  since  we  find  a  very  large  amount  of  it 
in  the  tissues  of  young  animals,  which  are  entirely  formed  from  albuminous  matter ;  and 
also  in  the  tissues  of  herbivorous  animals,  which  cannot  receive  it  in  their  food,  since  Plants 
yield  no  substance  resembling  Gelatine  in  composition.  It  has  been  suggested  by  Mulder, 
that  Gelatine  may  be  formed  by  the  decomposition  of  Proteine,  which  has  been  already 
mentioned  as  taking  place  from  the  agency  of  weak  alkaline  solutions  (§116  6),  and  which 
must  probably,  therefore,  be  continually  occurring  in  the  Blood.  For,  if  to  each  atom  of  Pro- 
tid  and  Erythroprotid,  we  add  one  of  the  atoms  of  Ammonia  which  are  given  off  in  that 


124  ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 

decomposition,  we  have  compounds,  of  which  the  former  differs  from  Gelatine  only  by  the 
presence  of  two  additional  atoms  of  hydrogen  and  the  deficiency  of  one  of  oxygen,  whilst 
the  only  difference  in  the  latter  consists  in  the  presence  of  one  additional  atom  of  hydrogen. 
Thus  the  ammoniated  Erythroprotid,  when  exposed  to  oxygenation  in  the  lungs,  may  have 
its  one  superfluous  atom  of  hydrogen  carried  off  in  the  form  of  water,  and  will  then  have 
the  composition  of  Gelatine ;  and  the  same  result  will  be  attained  from  the  ammoniated 
Protid,  by  the  addition  of  three  atoms  of  oxygen,  which  will  convert  it  into  Gelatine  with 
two  atoms  of  water.  According  to  this  formula,  the  substances  produced  from  the  decom- 
position of  the  proteine  in  blood,  merely  through  the  action  of  the  alkali  in  the  serum,  and 
the  oxydizing  influence  of  the  atmosphere,  are — carbonic  acid,  water,  gelatinous  'tissue,  and 
leucin.  The  carbonic  acid  passes  off  through  the  lungs  ;  and  the  water,  either  by  the  kid- 
neys, or  by  exhalation  from  the  lungs  or  skin.  The  Gelatine  only  requires  form,  to  become 
Fibrous  tissue.  Leucin,  however,  has  not  yet  been  found  in  the  body ;  and  until  it  shall 
have  been  discovered,  or  the  products  of  its  decomposition  shall  have  been  detected,  any 
such  attempt  to  explain  the  formation  of  Gelatine,  must  be  regarded  as  altogether  theoretical.* 
c.  The  relation  of  Gelatine  to  the  Proteine-compounds  is  further  shown  by  the  fact,  that 
Leucin  may  be  produced  from  the  former,  as  well  as  from  the  latter.  When  Gelatine  is 
boiled,  either  with  alkalies  or  with  dilute  sulphuric  acid,  Leucin  is  formed ;  together  with 
extractive  matters,  and  a  peculiar  sugar  termed  Glycicoll.  This  substance  crystallizes  in  large 
colourless  prisms,  which  have  a  sweet  taste,  and  feel  gritty  between  the  teeth ;  it  is  soluble 
in  4^  parts  of  water,  and  is  taken  up  in  small  quantity  by  Alcohol.  This  fact  is  one  of  much 
interest  in  regard  to  certain  Pathological  relations  of  Gelatine. 

142.  The  Yellow  Fibrous  tissue,  on  the  contrary,  undergoes  scarcely  any 
change  by  long  boiling;  a  very  small  quantity  of  Gelatine  being  alone  yielded 
by  it;  and  this  being  probably  derived  from  the  Areolar  tissue,  by  which  it  is 
penetrated.     It  is  unaffected  by  the  weaker  acids,  and  undergoes  no  solution 
in  the  gastric  fluid ;  and  it  preserves  its  elasticity  for  an  almost  unlimited  pe- 
riod.    According  to  Scherer,  the  yellow  fibrous  tissue  from  the  middle  coat 
of  the  Arteries  consists  of  48  C,  38  H,  6  N,  16  0 ;  which  (taking  Liebig's 
formula  for  Proteine)  may  be  regarded  as  1  Proteine  +  2  Water.     When 
burned,  it  leaves  1*7  per  cent,  of  ash. 

5.   Of  Simple  Cells,  floating  in  the  Minimal  Fluids. 

143.  The  red  colour,  which  is  characteristic  of  the  Blood  of  Vertebrated 
animals,  is  entirely  due  to  the  presence,  in  that  fluid,  of  a  very  large  number  of 
floating  cells,  which  have  the  power  of  forming  a  secretion  in  their  interior, 
that  is  distinguished  by  its  peculiar  chemical  nature,  as  well  as  by  its  hue. 
The  red  Blood-corpuscles  (commonly,  but  erroneously  termed  globules)  are 

flattened  Discs,  which,  in  Man  and  most 

Fig.  27.  of  the   Mammalia,  have  a  distinctly  cir- 

cular outline.  In  the  discs  of  Human 
blood,  when  examined  in  its  natural  con- 
dition, the  sides  are  somewhat  concave ; 
and  there  is  a  bright  spot  in  the  centre, 
which  has  been  regarded  by  many  as  in- 
dicating the  existence  of  a  nucleus ;  though 
it  is  really  nothing  else  than  an  effect  of 
refraction,  and  may  be  exchanged  for  a 
dark  one  by  slightly  altering  the  focus  of 
the  Microscope.  The  form  of  the  disc 

Red  Corpuscles  of  Human  Blood  represent-     jg  much  ^^  fa      yarious  ntfl  . 

ed  at  a,  as  they  are  seen  when  rather  beyond  J  .  J. 

the  focus  of  the  microscope ;  and  at  b  as  they  for  the  membrane  which  COmpOSCS  Its  ex- 
appear  when  within  the  focus.  Magnified  400  tenor  or  cell-well,  is  readily  permeable  by 
diameters.  liquids  ;  so  as  to  admit  a  passage  of  li- 

quid, according   to  the    laws   of  Endos- 
mose,  either  inwards  or  outwards,  as  the  relative  density  of  the  contents  of 

*  See  Mulder's  Chemistry,  p.  326. 


«      SIMPLE  ISOLATED  CELLS;— RED  BLOOD-CORPUSCLES.  125 

the  cell  and  of  the  surrounding  fluids  may  direct.  Thus,  if  the  Red  corpus- 
cles be  treated  with  water,  there  is  a  passage  of  that  liquid  into  the  cell ;  the 
disc  becomes  first  flat,  and  then  double-convex,  so  that  the  central  spot  disap- 
pears ;  and  by  a  continuance  of  the  same  process,  at  last  becomes  globular, 
and  finally  bursts,  the  cell-wall  giving  way,  and  allowing  the  diffusion  of  the 
contents  through  the  surrounding  liquid.  On  the  other  hand,  when  the  Red 
corpuscles  are  treated  with  a  thick  syrup  or  solution  of  albumen,  they  will  be 
more  or  less  completely  emptied,  and  caused  to  assume  a  shrunken  appear- 
ance ;  the  first  effect  of  the  process  being  to  increase  the  concavity,  and  to 
render  the  central  spot  more  distinct.  It  is  probable  that  the  Blood-corpuscles, 
even  whilst  they  are  circulating  in  the  living  vessels,  are  liable  to  alterations 
of  this  kind,  from  variations  in  the  density  of  the  fluid  in  which  they  float ; 
and  that  such  alterations  may  be  constantly  connected  with  certain  disordered 
states  of  the  system.*  We  hence  see  the  necessity,  in  examining  the  Blood 
microscopically,  for  employing  a  fluid  for  its  dilution,  that  shall  be  as  nearly 
'as  possible  of  the  same  character  with  ordinary  liquor  sanguinis.t 

144.  Microscopic  observers  have  been  much  divided  upon  the  question, 
whether  or  not  the  Red  corpuscles  of  the  Blood  of  Man  and  other  Mammalia 
contain  a  nucleus.     There  seems  every  probability  from  analogy,  that  a  nu- 
cleus exists  in  them,  as  it  does  in  the  red  corpuscles  of  all  other  animals ; 
but  it  cannot  be  brought  into  view  by  any  of  the  ordinary  methods,  which 
render  it  distinctly  visible  in  the  oval  blood-discs  of  Oviparous  Vertebrata ; 
and  of  late  the  general  opinion  has  been,  that  nothing  resembling  their  nuclei 
could  be  present  in  the  blood-discs  of  Man  and  Mammalia.     Dr.  G.  O.  Rees 
states,  however,  that,  by  carefully  examining  the  ruptured  cell-walls,  which 
fall  to  the  bottom  of  the  water  when  red   corpuscles  have   been    diffused 
through  it,  he  could  distinguish  appearances  on  them,  that  indicated  the  ex- 
istence of  nuclei ;  although  they  escape  observation  when  within  the  corpus- 
cles themselves,  on  account  of  their  high  refractive  power.     He  describes 
them  as  being  circular  and  flattened,  like  the  Red  corpuscles  themselves  ;  and 
as  about  two-thirds  of  their  diameter. 

145.  In  all  Oviparous  Vertebrata,  without  any  known  exception,  the  red 
corpuscles  are  oval, — the  proportion  between  their  long  and  short  diameters, 
however,  being  much  subject  to  varia- 
tion ;  and  their  nuclei  may  always  be  Fig.  28. 

brought  into  view,  by  treatment  with 
acetic  acid,  when  not  at  first  visible.  In 
the  red  particles  of  the  Frog,  which  are 
far  larger  than  those  of  Man,  a  nucleus 
can  be  observed  to  project  somewhat 
from  the  central  portion  of  the  oval, 
even  during  their  circulation ;  and  it 
is  rendered  extremely  distinct  by  the 
action  of  acetic  acid ;  this  renders  the 
remainder  of  the  particle  extremely  Particles  of  ^  blood;  i,u,  thfeir  flattened 

,  .,   A  *.        .  .  J,      face ;   2,  particle  turned   nearly  edgeways ;    3, 

transparent,  whilst  it  gives  increased     lymph.globule;  4,  blood-corpuscles  altered  by  di- 

Opacity  tO    the  nucleus.  Which    is  then      lute  acetic  acid.    Magnified  500  diameters. 

seen  to  consist  of  a  granular  substance. 

In  the  still  larger  blood-disc  of  the  Proteus  and  Siren,  this  appearance  is  yet 

*  See  Dr.  G.  O.  Rees'  Gulstonian  Lectures,  for  1845. 

t  By  Wagner,  the  filtered  serum  of  frog's  blood  is  recommended  for  this  purpose.  Weak 
solutions  of  salt  or  sugar,  and  urine,  answer  tolerably  well ;  but  Mr.  Gulliver  remarks  that 
all  addition  must  be  avoided,  when  it  is  intended  to  measure  the  corpuscles,  or  to  ascertain 
their  true  forms  ;  as  the  serum  of  one  Mammal  reacts  injuriously  on  the  blood  of  another. 
See  Philos.  Magaz.,  Jan.  and  Feb.  1840. 


126  ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 

more  distinct ;  the  structure  of  the  nucleus  being  so  evident  without  the  addi- 
tion of  acetic  acid,  that  its  granules  can  be  counted.* 

146.  The  form,  of  the  Red  Corpuscles  is  not  unfrequently  seen  to 
change  during  their  circulation ;  but  this  is  generally  in  consequence  of 
pressure:  from  the  effects  of  which,  however,  they  quickly  recover  them- 
selves. In  the  narrow  capillary  vessels,  they  sometimes  become  suddenly 
elongated,  twisted,  or  bent,  through  a  narrowing  of  the  channel ;  and  this 
may  take  place  to  such  a  degree,  as  to  enable  the  disc  to  pass  through  an 
aperture,  which  appears  very  minute  in  proportion  to  its  diameter.  When 
undergoing  spontaneous  decomposition,  the  blood-discs  become  granulated, 
and  sometimes  (as  long  ago  noticed  by  Hewson)  even  mulberry-shaped ;  and 
particles  in  which  these  changes  appear  to  be  commencing,  may  be  found  in 
the  blood  at  all  times.  It  has  been  ascertained  that  bile  and  urea  exert  a  pecu- 
liar solvent  power  on  the  blood-corpuscles ;  and  hence  we  can  understand 
one  of  the  modes  in  which  a  retention  of  these  substances  in  the  circulating 
fluid  (Chap.  XV.,  Sect.  1)  proves  so  injurious. — The  size  of  the  blood-discs 
is  liable  to  considerable  variation,  even  in  the  same  individual ;  some  being 
met  whh  as  much  as  one-third  larger,  whilst  others  are  one-third  smaller,  than 
the  average.  The  diameter  of  the  corpuscles  bears  no  constant  relation  to  the 
size  of  the  animal,  even  within  the  limits  of  the  same  class ;  thus,  although 
those  of  the  Elephant  are  the  largest  among  Mammalia  (as  far  as  is  hitherto 
known),  those  of  the  Mouse  tribe  are  far  from  being  the  smallest,  being  in 
fact  more  than  three  times  the  diameter  of  those  of  the  Musk  Deer.  There 
is,  however,  a  more  uniform  relation  between  the  size  of  the  animal  and  that 
of  its  blood-discs,  when  the  comparison  is  made  within  the  limits  of  the  same 
order.  In  Man,  the  diameter  varies  from  about  1 -4000th  to  1 -2800th  of  an 
inch;  the  average  diameter  is  probably  about  l-3200th. 

a.  The  following  measurements  of  the  blood-discs  of  various  animals  are  chiefly  given 
on  the  authority  of  Mr.  Gulliver. — The  diameter  of  the  corpuscles  in  the  Quadrumana  is 
generally  about  the  same  with  that  of  the  Human  blood-discs ;  there  is,  however,  a  slight 
diminution  among  the  Lemurs,  and  there  is  more  variation  among  them,  than  among  the 
Monkeys.  Among  the  Cheiroptera,  the  diameter  of  the  corpuscles  is  somewhat  less  than  in 
the  preceding  order,  the  average  being  about  l-4300th  of  an  inch.  Passing  to  the  Insecti- 
vora,  we  find  the  blood-discs  of  the  Mole  to  be  still  smaller,  averaging  only  the  l-4747th  of 
an  inch ;  those  of  the  Hedgehog,  however,  are  larger,  being  about  l-4085th.  In  the  corpus- 
cles of  the  different  families  of  the  Carnivora,  there  is  siidi  a  well-marked  diversity  in  the 
size  of  the  corpuscles,  that  the  fact  may  be  used  as  a  help  to  classification.!  In  the  Seals, 

*  As  Professor  Owen's  interesting  account  of  the  blood-discs  of  the  Siren  may  not  be 
generally  accessible  (Penny  Cyclopaedia,  Art.  Siren),  the  leading  facts  in  it  will  be  here 
stated.  This  animal  agrees  with  the  Proteus  and  other  species  in  being  perennibranchiate 
(§  32)  ;  and,  as  in  all  its  congeners  yet  examined,  the  blood-discs  are  of  very  large  dimen- 
sions. They  are  usually  of  an  oval  form,  the  long  diameter  being  nearly  twice  the  short; 
and  the  nucleus  projects  slightly  from  each  of  the  flattened  surfaces.  Considerable  variety 
in  the  form  of  the  disc  presents  itself,  some  of  the  corpuscles  being  much  less  oval  than 
others;  but  the  nuclei^do  not  partake  of  these  variations  in  nearly  the  same  degree.  The 
nucleus  is  clearly  seen  to  consist  of  a  number  of  moderately-bright  spherical  granules,  of 
which  from  20  to  30  could  be  seen  in  one  plane  or  focus,  the  total  number  being  of  course 
much  greater.  When  removed  from  the  capsule,  the  nuclei  are  colourless,  and  the  compo- 
nent granules  have  a  high  refracting  power.  Viewed  in  situ,  they  present  a  tinge  of  colour 
lighter  than  that  of  the  surrounding  fluid,  and  dependent  upon  the  thin  layer  of  that  fluid 
interposed  between  the  nucleus  and  the  capsule.  As  the  fluid  contents  of  the  blood-disc  in 
part  evaporate  during  the  process  of  desiccation,  the  capsule  falls  into  folds  in  the  interspace 
between  the  nucleus  and  the  outer  margin ;  these  folds  generally  take  the  direction  of  straight 
lines,  three  to  seven  in  number,  radiating  from  the  nucleus. 

f  Two  facts  of  much  interest  in  Zoology  have  been  brought  to  light  by  Mr.  Gulliver's 
examination  of  the  diameter  of  the  blood-corpuscles  of  this  tribe.  The  difference  between 
those  of  the  Dog  and  the  Wolf  is  not  greater  than  that  which  exists  among  the  varieties  of 
the  Dog ;  whilst  the  discs  of  the  Fox  are  much  smaller.  The  discs  of  the  Hyaena  are  far 
more  approximate  to  those  of  the  Canidse,  than  they  are  to  those  of  the  Felidoe. 


COMPARATIVE  SIZES  OF  RED  CORPUSCLES  OF  BLOOD.  127 

the  diameter  averages  l-3280th  of  an  inch;  in  the  Dog,  l-3540th ;  in  the  Bear,  about 
1 -3700th;  in  the  Weasel,  l-4200th;  in  the  Cat,  l-4400th ;  and  in  the  Viverrae,  l-5365th.  In 
two  species  only  of  the  Cetacea,  have  the  blood-discs  been  yet  examined ;  the  Dolphin,  in 
which  their  diameter  averages  l-3829th  of  an  inch ;  and  the  great  Rorqual  (the  largest  known 
Mammal),  in  which  they  are  only  l-3100th  of  an  inch,  or  scarcely  larger  than  those  of  Man. 
Among  the  Pachydermata,  the  average  excluding  the  Elephant  (the  diameter  of  whose  blood- 
discs  is  about  l-2745th  of  an  inch),  and  the  Rhinoceros  (in  which  they  are  about  l-3765th), 
may  be  stated  at  about  l-4200th;  and  there  is  less  variation  than  might  have  been  expected, 
from  the  different  size  and  conformation  of  the  several  species  examined.  Among  the  Ru- 
minantia,  the  corpuscles  are  for  the  most  part  smaller  than  in  other  orders ;  and  there  is  more 
relation  between  their  diameter  and  the  size  of  the  animal,  than  is  elsewhere  observable. 
Excluding  the  Camelidae  (which  are  zoologically  intermediate  between  the  Ruminantia  and 
Pachydermata),  we  find  a  range  of  sizes  extending  from  the  l-3777th  to  the  l-12,325th  of 
an  inch ;  the  former  is  the  diameter  in  one  of  the  larger  Deer ;  the  latter  in  the  Musk  Deer, 
which  is  the  smallest  in  the  whole  order.  In  the  Camel  tribe,  the  average  of  the  long  dia- 
meter of  the  corpuscles  is  about  l-3300th  of  an  inch ,  whilst  that  of  the  short  diameter  is 
l-6300th  ;  and  this  is  nowhere  widely  departed  from :  the  length  of  the  discs  is,  therefore, 
not  quite  twice  their  breadth.  Among  the  Rodentia,  the  discs  are  rather  large,  especially 
considering  the  small  size  of  most  of  the  species.  In  the  Capybara,  which  is  the  largest 
animal  of  the  order,  they  average  1-3 190th;  and  in  the  Mouse  family  (the  smallest  of  Mam- 
malia), they  are  as  much  as  1-38 14th.  In  the  Squirrels,  the  diameter  is  rather  less ;  but  in 
scarcely  any  of  the  whole  order  is  it  under  l-4000th.  Among  the  Edentata,  the  Two-toed  Sloth 
has  been  found  to  have  corpuscles  of  the  unusually  large  diameter  of  l-2865th  of  an  inch; 
whilst  in  the  Armadilloes  they  average  about  l-3400th.  In  the  Marsupialia  the  range  is 
nearly  the  same  as  among  the  Rodentia.  .- 

b.  In  BIRDS,  according  to  the  observations  of  Mr.  Gulliver,  the  long  and  short  diameters 
of  the  corpuscles  usually  bear  to  each  other  the  proportion  of  Ijt  or  2,  to  1;  and  this  is  the 
general  relation  among  Oviparous  Vertebrata,  with  the  exception  of  some  of  the  Crocodile 
tribe,  in  which  the  length  is  sometimes  three  times  the  breadth.    The  size  of  the  corpuscles 
of  Birds  has  generally  more  relation  to  that  of  the  species,  than  it  has  in  Mammalia.     No 
instance  has  yet  been  detected,  of  the  occurrence  of  comparatively  small  corpuscles  in  the 
larger  species,  and  of  large  corpuscles  among  smaller  animals,  which  has  been  seen  to  be 
common  among  the  former  class ;  the  blood  of  the  Humming-birds,  however,  has  not  yet 
been  examined.  ;  The  largest  discs  are  found  among  the  Cursores ;  those  of  the  Ostrich  have 
an  average  long  diameter  of  l-1649th  of  an  inch,  and  a  short  diameter  of  l-3000th;  and 
among  the  larger  Raptores,  Grallatores,  and  Natatores,  the  dimensions  are  but  little  inferior. 
The  least  dimensions  hitherto  observed  are  among  the  small  Passerine  birds ;  in  which  the 
corpuscles  have  a  long  diameter  of  about  l-2400th  of  an  inch,  and  a  transverse  diameter  of 
from  l-3800th  to  l-4800th.     Circular  discs  may  be  occasionally  observed  in  some  species, 
agreeing  with  the  others  in  every  particular  but  their  form ;  and  every  gradation  may  be  no- 
ticed between  these  and  the  regular  oval  corpuscles. 

c.  The  large  size  of  the  blood-discs  in  REPTILES,  especially  in  ttatrachia,  and  above  all, 
in  the  Perennibranchiate  species  of  the  latter,  has  been  of  great  service  to  the  Physiologist ; 
by  enabling  him  to  ascertain  many  particulars  regarding  their  structure,  which  could  not 
have  been  otherwise  determined  with  certainty.     Among  other  facilities  which  this  occa- 
sions, is  that  of  procuring  their  separation  from  the  other  constituents  of  the  blood ;  for  they 
are  too  large  to  pass  through   the  pores  of  ordinary  filtering-paper,  and  are  therefore  re- 
tained upon  it,  after  the  liquor  sanguinis  has  flowed  through.    The  blood-discs  of  the  warm- 
blooded Vertebrata  cannot  be  thus  separated.     The  oval  corpuscles  of  the  Frog  have  a  long 
diameter  of  about  1-1 108th,  and  a  transverse  diameter  of  about  l-1800th  of  an  inch;  those 
of  the  Salamander  or  Water-newt  are  still  larger.     The  long  diameter  of  the  corpuscles  of  the 
Proteus  is  stated  by  Wagner  at  l-337th  of  an  inch ;  that  of  the  Siren  is  about  l-435th,  the 
short  diameter  being  about  l-800th  of  an  inch ;  the  extremes  of  variation,  however,  are  very 
wide.     The  long  diameter  of  the  nuclei  is  about  l-1000th  or  1-1 100th,  and  the  short  diame- 
ter about  l-2000th;  hence  it  is  about  three  times  as  long,  and  nearly  twice  as  broad,  as  the 
entire  Human  blood-disc,  thus  having  six  times  its  superficies;  its  thickness  is  about  l-3800th 
of  an  inch. 

d.  The  number  of  FISHES,  in  which  the  diameters  of  the  blood-discs  have  been  examined, 
is  still  inconsiderable.  In  the  common  Perch,  they  average  1-2 100th  by  1-2824  ;  in  the  Carp, 
they  are  l-2142nd  of  an  inch  by  l-3429th;  in  the  Gold-Fish,  though  of  the  same  genus  and 
of  much  smaller  size,  they  are  as  much  as  l-1777th  by  l-2824th;  in  the  Pike,  l-2000th  by 
l-3555th;  and  in  the  Eel,  1-1 745th  by  1 -2842nd.* 

*  A  summary  of  Mr.  Gulliver's  numerous  and  valuable  observations  is  contained  in  the 
Proceedings  of  the  Zoological  Society,  No.  CLII. 


128  ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 

147.  In  speaking  of  the  Chemical  constitution  of  the   Red  Corpuscles  of 
Blood,  it  is  necessary  to  distinguish  the  substance  of  their  walls  and  nuclei 
from  their  fluid  contents.     These  may  be  separated  by  treating  them  with 
water ;  which,  as  already  mentioned,  occasions  the  rupture  of  the  cells,  the 
walls  of  which  sink  to  the  bottom,  whilst  their  contents  are  diffused  through 
the  liquid.     The  substance  obtained  from  the  former  has  been  termed  Globu- 
line;  but  it  does  not  seem  to  differ  in  any  essential  character  from  other  sub- 
stances, that  result  from  the  organization  of  the  proteine-compounds.     The 
compound  which  forms  the  contents  of  the  red    corpuscles,  however,  and 
which  gives  them  their  characteristic  hue,  is  very  different  both  in  its  sensi- 
ble properties,  and  in  its  composition ;  and  has  received  the  designation  of 
Hsematine.     When  separated  from  albuminous  matter,  it  is  of  a  dark-brown 
hue,  and  is   tasteless  and  insoluble  in  water,  alcohol,  and  ether ;  but  it  is  rea- 
dily soluble  in  water  or  alcohol,  that  contains  alkalies  or  acids  ;  whence  it  may 
be  supposed  to  unite  with  these,  like  albumen,  as   an  acid  or  a  base.     In 
composition,  however,  it  differs  considerably  from  that  of  the  proteine-com- 
pounds ;  its  formula  being  44  C,  22  H,  3  N,  6  O,  with  a  single  proportional 
of  iron.     When  burned,  it  yields  a  notable  quantity  of  peroxide  of  iron  ;  and 
one  atom  of  this  is  considered  to  be  present  in  combination  with  each  equiva- 
lent of  the  animal  compound.     The  red  colour  is  not  due,  however,  as  for- 
merly supposed,  to  the  presence  of  this  peroxide  ;  for  M.  Scherer  has  proved, 
that  the  metal  may  be  entirely  dissolved  away  by  the  agency  of  acids,  and 
that  the  animal  matter,  afterwards  boiled  in  alcohol,  colours  the  spirit  intensely 
red.     On  the  other  hand,  the  iron  is  most  certainly  united  firmly  with  the 
constituents  of  the  Haematine,  as  contained  in  the  red  corpuscles ;  for  this  sub- 
stance may  be  digested  in  dilute  sulphuric  or  muriatic  acid  for  several  days, 
without  the  least  diminution  in  the  quantity  of  iron,  the  usual  amount  of  which 
may  be  obtained  by  combustion  from  the  Haematine  that  has  been  subjected 
to  this  treatment.     When  diffused  through  water,  in  the  manner  just  describ- 
ed, the  Haematine  exhibits  the  same  changes  of  colour  under  the  influence  of 
oxygen,  acids,  saline  matter,  &c.,  as  the  Blood  undergoes  in  similar  circum- 
stances. 

148.  The  question  of  the  origin  of  the  red  Blood-corpuscles  is  a  very  inte- 
resting one,  and  cannot  yet  be  regarded  as  completely  determined.    That  they 
are  to  be  regarded  as  nucleated  cells, — conformable  in  general  character  with  the 
isolated  cells,  which  constitute  the  whole  of  the  simplest  Plants  (§  125),  and 
having  each  an  independent  life  of  its  own,  the  duration  of  which  is  limited, 
— there  can  now  be  no  reasonable  doubt.     From  this  we  should  infer  that  they 
have  the  power  of  reproducing  themselves  ;  and  the  recent  observations  of 
Dr.  Barry  and  other  Microscopists  seem  to  confirm  the  statement  long  ago 
made  to  that  effect  by  Leeuwenhoek.     The  first  change  said  to  take  place,  is 
the  appearance  of  delicate  radiating  lines  between  the  nucleus  and  the  peri- 
phery ;  dividing  the  disc  into  several  segments,  usually  six  in  number  (Plate  I., 
Fig.  22.)     The  margin  is  soon  observed  to  become  crenated,  by  indentations 
at  corresponding  points ;  and  these  indentations  become  deeper,  until  a  com- 
plete separation  takes  place,  setting  free  six  young  cells  or  discs  («,  6,  c,  rf,  e), 
which  seem  to  have  been  formed  around  the  margin  of  the  nucleus  of  the  pa- 
rent cell.     Between  the  small  newly-generated  disc,  and  the  full-sized  corpus- 
cle, we  should  expect  to  find  every  intermediate  size  ;  and  this  is  affirmed  by 
these  observers  to  be  the  case. — It  has  been  lately  asserted  by  Dr.  G.  O.  Rees, 
that,  when  examining  a  portion  of  Blood  maintained  at  about  its  natural  tem- 
perature, he  observed  some  of  the  corpuscles  to  assume  an  hour-glass  form, 
by  a  contraction  across  their  middle  ;  and  that,  by  the  increase  of  this  contrac- 
tion, producing  the  complete  division  of  the  corpuscles,  two  unequal-sized* 
circular  bodies  were  eventually  produced  from  each ;  which,  when  treated 


ORIGIN  AND  MULTIPLICATION  OF  RED  CORPUSCLES.  129 

•with  a  strong  saline  solution,  were  emptied  of  their  contents,  like  ordinary 
blood-discs. — It  is  not  at  all  improbable,  that  both  these  methods  of  multi- 
plication may  be  followed ;  and  it  can  scarcely  be  doubted  that,  by  one  or 
both,  a  continual  succession  of  Red  corpuscles  is  kept  up.  That  the  corpus- 
cles may  be  generated  with  great  rapidity  under  peculiar  circumstances,  will 
hereafter  appear  (Chap.  XL,  Sect.  6) ;  and  their  amount  may  undergo  a  rapid 
diminution  also,  without  any  evident  abstraction  of  them  from  the  circulating 
fluid.  This  diminution  seems  to  be  traceable  in  some  instances  to  a  too  low 
specific  gravity  of  the  serum  ;  which  will  cause  the  Red  corpuscles  to  rupture 
by  endosmose,  just  as  when  they  are  treated  with  water. — Appearances  have 
been  seen  by  Wagner,  Gulliver,  and  others,  in  the  blood  of  Batrachia,  which 
might  seem  to  indicate  that  the  Colourless  corpuscles  (§  151)  serve  as  the 
nuclei  of  cells,  which,,  when  fully  developed,  may  become  Red  blood-discs ; 
but  in  the  Mammalia,  it  is  scarcely  possible  to  imagine  that  this  can  occur ; 
since  the  diameter  of  the  colourless  corpuscles  is  very  constant ;  whilst  that 
of  the  Red  blood-discs  is  so  variable,  that  the  former,  though  sometimes  the 
smaller,  are  in  other  instances  far  larger  than  the  latter.  If  it  be  admitted 
that  the  Red  corpuscles  have  the  power  of  reproduction,  like  other  isolated 
cells,  it  does  not  seem  necessary  to  seek  elsewhere  for  the  source  of  their  con- 
stant renewal ;  and  various  facts,  hereafter  to  be  stated,  appear  to  the  Author 
strongly  indicative  of  the  entire  functional  as  well  as  structural  difference, 
between  the  red  and  the  colourless  corpuscles  of  the  blood  of  Vertebrata. 

149.  That  the  Red  blood-discs,  when  first  formed  in  the  embryo,  have  an 
origin  common  to  that  of  all  other  tissues,  cannot  be  doubted.  They  are  pro- 
duced, in  the  embryo  of  the  Bird,  in  the  portion  of  the  germinal  membrane 
which  afterwards  becomes  the  area  vasculosa  ;  this  consists  of  delicate  cells 
very  uniformly  disposed:  and  whilst  capillary  vessels  are  being  formed  by 
the  union  of  the  cavities  of  these,  blood-discs  seem  to  be  developed  from 


Fig.  29. 


0 


Production  of  blood-corpuscles  in  Chick,  on  the  fourth  day  of  incubation  ;  a,  particles  fully  formed; 
6,  particles  in  progress  of  formation;  c,  similar  particles  altered  by  dilute  acetic  acid,  so  as  to  display  their 
nuclei. 

the  granules  or  cell-germs  they  contain.  These  changes  take  place  about  the 
second  or  third  day  of  incubation ;  but  it  is  not  until  some  days  afterwards, 
that  the  discs  assume  their  characteristic  form. 

a.  Mr.  Macleod  gives  the  following  history  of  the  development  of  the  blood-corpuscles 
in  the  Chick.  In  blood  withdrawn  from  the  heart,  on  the  third  day,  and  diluted  with  se- 
rum, or  from  the  germinal  membrane  or  allantois,  and  diluted  with  fluid  albumen, — "  a  num- 
ber of  small  granules  are  seen  floating  about  the  field  :  these  enlarge  and  become  clearer  in 
the  centre ;  this  enlargement  goes  on  very  rapidly,  and  when  they  have  gained  to  about  twice 
their  original  size,  the  central  clear  part  becomes  dull.  This  dullness  slightly  increases,  and 
in  a  short  time  it  is  seen  to  be  distinctly  granular;  whilst  the  borders  are  observed  to  be 
well-defined,  smooth,  and  clearer  than  the  central  part.  The  enlargement  of  these  bodies, 
with  the  granular  appearance  of  their  centre,  seems  not  to  depend  on  the  aggregation  of 
granules  round  a  centre  one,  but  on  a  property  which  they  have  in  themselves  of  enlarging 
and  presenting  that  figure.  During  all  this  time  they  are  quite  spherical  and  of  good  con- 
sistence, as  they  do  not  lose  their  form  by  considerable  pressure.  In  the  second  stage,  the 
central  portion  gradually  becomes  less  opaque,  and  ceases  to  appear  granular,  the  external 


130  ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 

portion  at  the  same  time  separating  in  some  degree  from  the  central  part.  The  blood-cor- 
puscle, in  this  stage  of  development,  has  the  appearance  of  a  slightly  flattened  round  cell, 
formed  of  a  somewhat  delicate  but  elastic  membrane,  with  a  nucleus  in  the  centre.  At  this 
time  a  number  of  these  bodies,  being  close  together  in  the  field,  presents  a  yellowish  colour. 
The  cell  is  disc-like,  rather  concave,  but  the  nucleus  convex.  In  the  third  stage,  one  side  of 
the  corpuscle  gradually  elongates,  giving  it  a  pear-shaped  appearance ;  the  opposite  side  then 
elongates  itself  in  a  similar  manner,  and  to  the  same  degree.  The  concavity  between  the 
nucleus  and  border  disappears,  and  the  whole  becomes  slightly  convex.  The  hue  at  the 
same  time  gradually  becomes  redder."* 

The  corpuscles  are  generally  larger  in  the  embryo  than  in  the  adult,  espe- 
cially soon  after  the  period  of  their  first  formation ;  it  was  remarked  by  M. 
Prevost,  that  in  the  foetal  goat  they  were  at  first  twice  the  size  of  those  of  the 
mother.  Mr.  Gulliver  has  observed,  however,  that  at  a  later  period  of  utero- 
gest^tion  they  are  sometimes  smaller  than  the  average  dimension  of  the  adult; 
but  perhaps  all  such  observations  are  to  be  received  with  hesitation,  owing  to 
the  fact  mentioned  by  him,  that  the  variety  in  the  magnitude  of  the  foetal  cor- 
puscles is  much  greater  than  in  the  full-grown  animal. 

150.  In  regard  to  the  uses  of  the  Red  corpuscles  of  the  Blood,  in  the  Ani- 
mal economy,  it  appears  to  the  Author  that  a  definite  conclusion  may  be  now 
arrived  at.     Their  existence  in  the  circulating  fluid  is  nearly  confined  to*  the 
Vertebrated  classes  ;  the  corpuscles  which  are  seen  in  the  blood  of  the  Inver- 
tebrated,  being  mostly  analogous  rather  to  the  Colourless  corpuscles,  presently 
to  be  described  as  present  in  the  blood  of  the  higher  animals.     Among  the 
lower  Invertebrata,  indeed,  the  Red  corpuscles  seem  to  be  altogether  wanting ; 
and  the  same  may  be  said  of  the  embryos  of  the  highest  animals,  at  an  early 
period  of  their  development ;  as  well  as  of  the  early  state  of  parts  that  are 
being  newly  formed,  at  any  period  of  their  lives.     Hence  the  inference  ap- 
pears highly  probable,  that  they  are  not  essentially  necessary  to  the  produc- 
tion of  the  organizable  elements  of  the  blood,  or  of  the  organized  tissues ;  in 
other  words,  to  the  simple  acts  of  growth  and  nutrition.    The  Red  corpuscles 
are  most  abundant  in  those  classes  among  Vertebrata,  which  maintain   the 
highest  temperature  ;  thus,  they  are  somewhat  more  numerous,  in  proportion 
to  the  whole  bulk  of  the  Blood,  in  Birds  than  in  Mammalia ;  and  far  more  in 
the  latter,  than  in  Reptiles  and  Fishes.     As  it  is  evident  that  they  undergo 
very  important  changes  in  the  pulmonary  and  systemic  capillaries, — their  co- 
lour being  changed  from  purple  to  red  in  the  former,  and  from  red  to  purple 
in  the  latter, — it  seems  highly  probable  that  they  have  as  their  principal  office, 
the  introduction  of  oxygen  into  the  blood  that  circulates  through  the  systemic 
capillaries,  and  the  removal  of  the  carbonic  acid  set  free  there ;  serving,  in 
fact,  as  the  medium  for  bringing  the  tissues  into  relation  with  the  air,  the  in- 
fluence of  which  is  necessary  for  the  maintenance  of  their  vital  activity.    In 
the  Invertebrata  generally,  whose  respiration  is  very  feeble,  this  end  will  be 
sufficiently  answered  by  the  fluid  plasma  of  the  blood  ;  the  alterations  in  which, 
under  the  influence  of  the  air,  have  been  already  noticed  (§§  115, 116  a).  And 
in  Insects, — the  only  class  whose  respiration  is  at  all  active,  we  find  the  air 
directly  conveyed  into  the  tissues  ;  the  circulating  fluid  not  being  employed  as 
its  carrier  (§  18).     We  shall  hereafter  find,  that  the  influence  of  oxygen  upon 
the  Nervous  and  Muscular  systems  is  essential  to  their  vital  activity  ;  and  it 
seems  to  be  by  their  agency  in  bringing  these  into  relation,  that  the  Red  cor- 
puscles possess  that  intimate  connection  with  the  Animal  functions,  which  we 
find  them  to  possess.     The  animals  whose  temperature  is  the  highest,  are 
also  those  whose  senses  are  most  acute,  and  whose  movements  are  most  ener- 
getic :  whilst,  on  the  other  hand,  if  there  be  any  unusual  diminution  in  the 

*  London  and  Edinburgh  Monthly  Journal,  September,  1842. 


COLOURLESS  CORPUSCLES  OF  BLOOD.  131 

proportion  of  Red  corpuscles,  it  is  invariably  accompanied  by  muscular  de- 
bility and  deficient  nervous  power. 

a.  By  Liebig  it  is  supposed,  that  the  iron  in  the  red  corpuscles  is  the  real  agent  in  the 
respiratory  process :  for  if  its  original  state  be  the  protoxide,  it  may  become  the  peroxide 
by  uniting  with  an  additional  atom  of  oxygen,  or  the  protocarbonate  by  the  addition  of  an 
atom  of  carbonic  acid.  The  former  change  is  supposed  by  him  to  take  place  in  the  lungs, 
to  which  the  blood  comes  charged  with  carbonic  acid ;  the  carbonic  acid  is  given  up  by  the 
iron,  and  replaced  by  an  equivalent  of  oxygen  taken  in  from  the  air :  whilst  in  the  syste- 
mic capillaries,  the  converse  change  takes  place, — the  oxygen  being  imparted  to  the  tissues, 
and  being  replaced  by  carbonic  acid  which  is  given  up  by  them  to  be  conveyed  out  of  the 
system.  It  is  stated  by  Liebig  that  there  is  far  more  than  sufficient  iron  in  the  whole  mass 
of  the  blood,  to  convey  in  this  manner  all  the  oxygen  and  carbonic  acid,  which  are  inter- 
changed between  the  pulrrionary  and  systemic  capillaries.  The  speculation  is  certainly  an 
ingenious  one ;  but  it  can  scarcely  be  yet  received  as  a  physiological  fact. 

151.  Besides  the  red  particles  of  the  Blood,  there  are  others  which  possess 
no  colour,  and  which  seem  to  have  a  function  altogether  different ;  these  are 
known  as  the  White  or  Colourless   corpuscles.     Their  existence  has  long 
been  recognized  in  the  blood  of  the  lower  Vertebrata,  where,  from  being  much 
smaller  than  the  red  corpuscles,  they  could  readily  be  distinguished.     But  it 
is  only  of  late, — chiefly  through  the  researches  of  Gulliver,  Addison,*  and 
others,  that  they  have  been  recognized  in  the  blood  of  Man  and  other  Mam- 
malia ;  their  size  being  nearly  the  same  with  that  of  the  red  corpuscles ;  and 
the  general  appearance  of  the  two  (owing  to  the  circular  form  of  the  latter, 
and  the  absence  of  a  proper  nucleus,)  being  less   distinct.     It  is  remarkable 
that,  notwithstanding  the  great  variations  in  the  size  of  the  red  corpuscles  in 
the  different  classes  of  Vertebrata,  the  dimensions  of  the  colourless  corpuscles 
are  extremely  constant  throughout ;  their  diameter  seldom  being  much  greater 
or  less  than  l-3000th  of  an  inch.     This  has  been  observed  even  in  those  ani- 
mals,— the  Musk-deer,  and  the  Proteus, — which  present  the  widest  departure 
from  the  general  standard   in  the  size  of  their  red  corpuscles :  so   that  the 
colourless  corpuscle  is  as  much  as  four  times  the  diameter  of  the  red,  in  one 
instance ;  whilst  it  is  not  one-eighth  of  the  long  diameter  of  the  red,  in  the 
other.     Hence  it  would  seem  very  improbable,  that  the  red  can  never  be  con- 
verted into  the  white,  or  the  white  into  the  red. — The  aspect  of  the  two,  under 
the  Microscope,  is   very  different.     Instead  of  presenting  a  distinct  central 
nucleus,  like  the  red  corpuscles  of  the  Oviparous  Vertebrata, — or  being  en- 
tirely destitute  of  granular  contents,  as  are  those  of  Mammalia  when  unaffected 
by  reagents,  the    colourless    corpuscles  are  studded  with  minute  granules, 
which  may  be  occasionally  seen  in  active  motion  within  them,  and  which  are 
discharged  when  the  corpuscles  are  treated  with  liquor  potassae.     They  pos- 
sess, moreover,  a  higher  refracting  power  than  the  red  corpuscles  ;  and  are 
further  distinguished  from  them,  by  their  greater  firmness,  and  by  the  ab- 
sence of  any  disposition  to  adhere  to  each  other ;  so  that,  when  a  drop  of  recent 
blood  is  placed  between  two  strips  of  glass,  and  these  are  gently  moved  over 
one  another,  the  white  corpuscles  may  be  at  once  recognized  by  their  soli- 
tarirress,  in  the  midst  of  the  rows  and  irregular  masses  formed  by  the  aggre- 
gation of  the  red.     This  is  still  better  seen  in  inflamed  blood  ;  in  which  the 
Red  corpuscles  have  a  peculiar  tendency  to  adhere  to  one  another,  whilst  the 
White  are  present  in  unusual  number. 

152.  The  Colourless  corpuscles  may  be  readily  distinguished  in  the  cir- 
culating Blood,  in  the  capillaries  of  the  Frog's  foot ;  and  it  is  then  observa- 
ble, that  they  occupy  the  exterior  of  the  current,  where  the  motion  of  the  fluid 
is  slow,  whilst  the  red  corpuscles  move  rapidly  through  the  centre  of  the  tube. 

*  Transactions  of  the  Provincial  Medical  Association,  1842  and  1843. 


132 


ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 


Fig.  30. 


A  small  venous  trunk,  a,  from  the  Web  of 
the  Frog's  foot,  magnified  350  Diam  ;  6,  b,  cells 
of  the  pavement-epithelium,  containing  nuclei. 
In  the  space  between  the  current  of  oval  blood- 
corpuscles,  and  the  walls  of  the  vessel,  the  rouud 
transparent  white  corpuscles  are  seen. 


The  Colourless  corpuscles,  indeed,  often  show  a  disposition  to  adhere  to  the 
walls  of  the  vessels ;  which  is  manifestly  increased  on  the  application  of  an 
irritant.  Hence  the  idea  naturally  arises,  that  (to  use  the  words  of  Mr.  Whar- 

ton  Jones)  "  there  is  some  reciprocal  re- 
lation between  the  colourless  corpuscles, 
and  the  parts  outside  the  vessels,  in  the 
process  of  nutrition."  What  that  rela- 
tion is,  we  shall  now  proceed  to  inquire. 
153.  In  regard  to  the  purpose  of  the 
Colourless  corpuscles  in  the  Animal  eco- 
nomy, a  view  has  been  brought  forward 
by  the  Author,*  which  increased  consi- 
deration has  only  served  to  strengthen ; 
and  which  he  advances  here,  with  some 
degree  of  confidence  that  it  will  be  found, 
on  attentive  examination,  warranted  by 
a  large  number  of  physiological  analo- 
gies, though  not  capable  of  being  direct- 
ly proved.  That  it  may  be  rightly  un- 
derstood, a  general  sketch  of  certain 
known  operations  of  cells  in  Plants  and 
Animals  will  be  first  given. — It  is  not 
difficult,  on  taking  a  comprehensive  sur- 
vey of  the  Assimilating  processes,  to 
find  a  number  of  examples,  in  which 
cells  are  developed  in  a  temporary  man- 
ner ;  growing,  arriving  at  maturity,  and 
then  disappearing,  apparently  without  having  performed  any  particular 
function.  In  the  albumen  of  the  Seed,  for  instance,  this  often  takes  place  to 
a  remarkable  extent.  In  the  Yolk  of  the  Egg,  there  is  a  similar  transitory 
development  of  cells,  of  which  several  generations  succeed  each  other,  without 
any  permanent  structure  being  the  result ;  and  we  have  seen  that,  according 
to  Dr.  Barry ,t  a  process  of  the  same  nature  takes  place  within  the  germinal 
vesicle,  and  in  the  primary  embryonic  cells  and  their  descendants  (§  130). 
It  can  scarcely  be  imagined  by  the  well-judging  Physiologist,  that  all  this 
cell-life  comes  into  existence  without  some  decided  purpose ;  and  if  we  can 
assign  to  it  an  object,  the  fulfilment  of  which  is  consistent  with  the  facts  sup- 
plied by  analogy  elsewhere,  this  may  be  reasonably  considered  as  having  a 
fair  claim  to  be  received  as  a  physiological  induction. — In  all  these  instances, 
and  in  many  more  which  might  be  quoted,  the  crude  alimentary  materials  are 
being  prepared  to  undergo  conversion  into  permanent  and  regularly-organized 
structures.  We  have  seen  that  the  very  first  union  of  the  inorganic  elements, 
into  the  simplest  proximate  principles,  is  effected  by  the  cell-life  of  Plants. 
The  change  of  these  principles  into  the  peculiar  compounds,  which  form  the 
characteristic  secretions  of  Plants,  is  another  result  of  their  cell-life.  And 
there  seems  equal  ground  for  the  belief  that  the  change  of  these  proximate 
principles  into  the  peculiar  glutinous  sap,  which  is  found  wherever  a  forma- 
tion of  new  tissue  is  taking  place,  is  equally  dependent  upon  the  agency  of 
cells.  Thus,  the  starchy  fluid,  which  is  contained  in  the  ovule  previously  to 
its  fecundation,  is  probably  not  in  the  state  in  which  it  can  be  immediately 
rendered  subservient  to  the  nutrition  of  the  embryo ;  and  the  development  of 
successive  generations  of  cells,  which  exert  upon  it  their  vitalizing  influence, 

*  Report  on  Cells,  in  British  and  Foreign  Medical  Review,  Jan.  1843. 
j"  Embryo] ogical  Researches.     Third  Series. 


COLOURLESS  CORPUSCLES  OF  BLOOD.  133 

may  be  reasonably  regarded  as  the  means,  by  which  the  requisite  change  is 
effected.  Exactly  the  same  may  be  said  of  the  Albuminous  matter  contained 
in  the  Yolk  .of  the  Egg,  which  is  certainly  not  in  a  condition  in  which  it  can 
be  immediately  applied  to  the  purposes  of  nutrition ;  and  its  conversion  may 
be  regarded  as  commencing  with  the  development  of  transitory  cells  within 
its  own  substance,  and  as  being  completed  by  means  of  the  cells  forming  the 
inner  layer  of  the  germinal  membrane,  by  which  it  is  subsequently  taken  up 
and  introduced  into  the  current  of  blood  flowing  through  the  vascular  area 
(§  149).  A  similar  purpose  is  probably  answered  by  the  transitory  cells  de- 
veloped within  the  germinal  vesicle ;  and  by  those  which  appear  at  a  similar 
period,  in  the  evolution  of  the  descendants  of  the  "  twin  cells"  produced  in 
it. — Many  similar  examples  have  been  elsewhere  adduced. 

a.  There  are  probably  cases,  however,  in  which  cells  are  very  rapidly  called  into  exist- 
ence, without  that  preparatory  elaboration  of  their  nutrient  materials,  which  we  regard  as 
due  to  the  vital  operations  of  a  preceding  generation.  Thus  the  Sovista  giganteum,  a  large 
fungus  of  the  Puff-ball  tribe,  has  been  known  to  increase,  in  a  single  night,  from  a  mere  point 
to  the  size  of  a  huge  gourd,  estimated  to  contain  47,000,000,000  cellules.  In  such  a  case  it 
is  difficult  to  suppose  that  any  but  the  most  rapid  mode  of  generating  cells  ean  have  been  in 
operation ;  and  the  idea  that  these  could  not  have  been  developed  by  any  such  elaborate 
process  as  that  just  alluded  to,  is  borne  out  by  the  fact  of  their  extremely  transitory  charac- 
ter,— the  decay  of  such  a  structure  being  almost  as  rapid  as  its  production.  The  same  may  be 
remarked  of  those  fungous  growths,  in  the  Animal  body,  which  sprout  forth  most  rapidly. 
Hence  the  apparent  exception  assists  in  proving  the  rule. 

154.  We  have  thus  a  class  of  facts,  which  indicates  that  the  conversion  of 
the  Chemical  compound  into  the  organizable  principle — the  aplastic  into  the 
plastic   material— is   effected,  in  the  particular  situations  where  it  is   most 
wanted,  by  the  vital  agency  of  transitory  cell-life ;  that  is,  by  the  production 
of  cells,  which  are  not  themselves  destined  to  form  an  integral  part  of  any 
permanent  structure,  but  which,  after  attaining  a  certain  maturity,  reproduce 
themselves  and  disappear ;  successive  generations  thus  following  one  another, 
until  the  object  is   accomplished,  after  which  they  altogether  vanish.     We 
shall  now  consider  another  class  of  facts,  which  seem  to  indicate  that  a  change 
of  this  kind  is  being  continually  effected  in  the  nutritious  fluids  of  Animals, 
during  their  circulation  through  the  body :  by  Cells,  which  are  either  carried 
about  with  them,  or  which  are  developed  for  the  purpose  in  particular  situa- 
tions, as  in  Plants.     The  former  is  the  nrore  common  occurrence ;  since  the 
conditions,  of  Anirnal  life,  usually  involving  a  general  movement  of  the  body, 
require  also  a  constant  general  reparation  of  its  parts,  and  therefore  an  adapt- 
ation of  the  circulating  fluid  to  the  wants  of  the  whole  fabric. 

155.  It  is  not  in  the  Blood  alone,  that  floating  cells  are  met  with;  for  Cells, 
which  seem  identical  with  the  Colourless  corpuscles  of  the  blood,  are  found 
in  the  Chyle  and  Lymph — fluids  in  which,  as  in  the  Blood,  the  elaboration 
of  plastic  Fibrine  from  unorganizable  Albumen  is  continually  taking  place,  to 
make  up  for  the  constant  withdrawal  of  the  former  substance  by  the  nutrient 
processes.     Hence  there  would  seem  reason  for  attributing  this  important 
function  to  these  floating  cells ;  the  number  of  which  present  in  the  fluids, 
seems  to  bear  a  very  close  relation  with  the  energy  of  the  elaborating  process. 
It  is  a  fact  of  great  physiological  interest  and  importance,  that,  whilst  the 
colourless  corpuscles  are  to  be  met  with  in  the  nutritious'  fluids  of  all  Animals 
which  possess  a  distinct  circulation,  the  red  corpuscles  are  nearly  restricted  to 
the  blood  of  Vertebrata.     This   observation,  which  was  first  put  forth  by 
Wagner,*  has  been  confirmed  by  the  Authos,  who  had  been  previously  struck 
with  the  very  close  analogy  between  the  floating  cells  carried  along  in  the 

*  [Elements  of  Physiology,  translated  by  R.  Willis.] 
12 


134          ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 

current  of  the  circulation  in  some  of  the  very  transparent  aquatic  larvae  (espe- 
cially those  of  the  Culicidae),  and  the  lymph-corpuscles  of  the  Frog.  Now 
it  is  evident  from  this  fact,  that,  as  the  Blood  of  Vertebrata  is  distinguished 
from  their  Chyle  chiefly  by  the  presence  of  red  corpuscles  in  the  former,  and 
by  the  absence  of  those  bodies  in  the  latter,  the  nutritious  fluid  of  Inverte- 
brated  animals  is  rather  analogous  (as  Wagner  has  remarked)  to  the  Chyle 
and  Lymph,  than  to  the  Blood  of  Vertebrata.  Or,  to  put  the  same  idea  in 
another  form,  the  presence  of  the  colourless  corpuscles  in  the  nutritious  fluid 
appears  to  be  the  most  general  fact  in  regard  to  its  character  throughout  the 
whole  Animal  scale;  whilst  the  presence  of  red  corpuscles  in  that  fluid  is 
limited  to  the  Vertebrated  classes  and  the  higher  Invertebrata.  Hence  it 
would  not  be  wrong  to  infer,  that  the  function  of  the  colourless  corpuscles 
must  be  of  a  general  character,  and  intimately  connected  with  the  nutritious 
properties  of  the  circulating  fluid ;  whilst  the  function  of  the  red  corpuscles 
must  be  of  a  limited  character,  being  only  required  in  one  portion  of  the  ani- 
mal kingdom. 

156.  Further,  it  has  been  noticed  by  Mr.  Gulliver,  that  in  the  very  young 
embryo  of  the  Mammalia,  the  white  globules  are  nearly  as  numerous  as  the 
red  particles:  this,  Mr.  Gulliver  has  frequently  observed  in  foetal  deer  of  about 
1|  inch  long.     In  a  still  smaller  foetus,  the  blood  was  pale,  from  the  prepon- 
derance of  the  white  corpuscles.     It  is,  therefore,  a  fact  of  much  interest, 
that,  even  in  the  Mammiferous  embryo,  at  the  period  when  growth  is  most 
rapid,  the  circulating  fluid  has  a  strong  analogy  to  that  of  the  Invertebrata. 
It  then,  too,  bears  in  other  respects  the  most  striking  analogy  to  Chyle;  since 
it  consists  of  the  fluid  elaborated  from  the  organizable  matter  supplied  by  the 
parent,  and  directly  introduced  into  the  current  of  the  circulation.    The  func- 
tion of  the  placental  vessels  may  be  regarded  as  double :  for  they  are  at  the 
same  time  the  channel,  through  which  the  alimentary  materials  supplied  by 
the  parent  are  introduced  into  the  circulating  system  of  the  foetus ;  and  the 
medium  of  aerating  the  fluid,  which  has  traversed  the  foetal  system.     Hence 
the  placenta  may  be  regarded  as  at  once  the  digestive  and  the  respiratory 
apparatus  of  the  foetus ;  and  the  fluid  circulating  through  the  cord,  as  at  once 
chyle  and  blood.     It  is  not  until  the  pulmonary  and  lacteal  vessels  of  the 
embryo  have  commenced  their  independent  operation,  that  the  distinction  be- 
tween the  blood  and  the  chyle  of  the  foetus  becomes  evident;  and  we  should 
expect,  therefore,  to  find  that  the  circulating  fluid,  up  to  the  time  of  birth, 
contains  a  large  proportion  of  white  corpuscles, — which  is  actually  the  case. 
There  is  a  gradual  decrease,  however,  in  their  proportional  number,  from  the 
earlier  to  the  later  stages  of  embryonic  life ;  in  accordance  with  the  diminish- 
ing energy  of  the  formative  processes.     The  recent  observations  of  Mr.  New- 
port upon  the  Blood  of  Insects,*  present  a  remarkable  correspondence  with 
the  foregoing.     He  finds  in  the  circulating  fluid  of  the  Larva,  a  number  of 
" oat-shaped"  corpuscles  or  floating  cells;  which  he  regards  as  analogous  to 
the  Colourless  corpuscles  of  Vertebrata.     These  are  most  numerous  at  the 
period  immediately  preceding  each  change  of  skin;  at  which  time  the  blood 
is  extremely  coagulable,  and  evidently  possesses  the  greatest  formative  power. 
The  smallest  number  are  met  with  soon  after  the  change  of  skin;  when  the 
nutrient  matter  of  the  blood  has  been  exhausted  in  the  production  of  new 
epidermic  tissue.     In  the  Pupa  state,  the  greatest  number  are  found  at  about 
the  third  or  fourth  day  subsequent  to  the  change ;  when  preparations  appear 
to  be  most  actively  going  on,  for  the  development  of  the  new  parts  that  are 
to  appear  in  the  perfect  Insect.    'After  this,  there  is  a  gradual  diminution;  the 
plastic  element  being  progressively  withdrawn  by  the  formative  processes ; 

*  Philosophical  Magazine,  May  1845. 


COLOURLESS  CORPUSCLES  OF  BLOOD.  135 

until,  in  the  perfect  Insect,  very  few  remain.  When  the  wings  are  being 
expanded,  however,  and  are  still  soft,  a  few  oat-shaped  corpuscles  circulate 
through  their  vessels ;  but  as  the  wings  become  consolidated,  these  corpuscles 
appear  to  be  arrested  and  to  break  down  in  the  circulating  passages ;  supply- 
ing, as  Mr.  N.  thinks,  the  nutrient  material  for  the  completion  of  these  struc- 
tures, which  subsequently  undergo  no  change.  In  the  perfect  Insect,  a  differ- 
ent set  of  corpuscles  makes  its  appearance;  which  is  rather  analogous  to  the 
red  corpuscles  of  Vertebrata.  This  last  fact  completely  harmonizes  with  the 
views  already  expressed ;  since  the  formative  processes  are  now  reduced  to 
their  lowest  condition  in  the  Insect;  whilst  the  respiration  attains  its  highest 
grade. 

157.  Even  in  adult  animals,  however,  variations  in  formative  power  may 
be  detected;  which  correspond  with  variations  in  the  number  of  the  Colour- 
less corpuscles.     Thus  it  has  been  observed  by  Wagner,*  that  the  number  of 
these  corpuscles  is  always  remarkably  great,  in  the  blood  of  well-fed  Frogs 
just  caught  in  the  summer  season;  whilst  it  is  very  small  in  those  which  have 
been  long  kept  without  food,  or  which  are  examined  during  the  winter.     In 
the  reparation  of  injuries,  too,  which  is  effected  in  cold-blooded  animals  by  a 
process  of  simple  growth  without  inflammation,  it  would  seem  that  the  Co- 
lourless corpuscles  perform  an  important  part;  as  they  are  observed  in  great 
numbers,  and  in  a  nearly  stationary  condition,  in  the  vessels  surrounding  the 
spot  where  the  new  tissue  is  being  formed;  apparently  having  the  same  action 
as  in  the  first  development  of  parts  altogether  new,  such  as  the  toes  of  the 
larva  of  the  Water-Newt. 

158.  A  remarkable  confirmation  <of  this  view  of  the  connection  between  the 
generation  of  Colourless  corpuscles  in  the  Blood,  and  the  production  of  Fi- 
brine,  is  derived  from  the  phenomena  of  Inflammation.     A  decided  increase 
in  the  normal  proportion  of  Fibrine  in  the  Blood  (from  2£  to  3%  parts  in  1000), 
may  probably  be  looked  upon  as  the  essential  indication  of  the  existence  of 
the  Inflammatory  condition.     That  this  production  of  Fibrine  is  due  to  a  local 
change,  can  scarcely  be  doubted  ;  since  it  is  frequently  observed  to  commence, 
before  any  constitutional  symptoms  manifest  themselves  :  and  it  may  be  re- 
garded, in  fact,  as  one  cause  of  these  symptoms.     Now  the  microscopic  ob- 
servations of  Mr.  Addisont  and  Dr.  Williams,;}:  made  independently  of  each 
other,  have  established  the  important  fact,  that  a  great  accumulation  of  Colour- 
less corpuscles  takes  place  in  the  vessels  of  an  inflamed  part :  this  seems  to 
be  caused  at  first,  by  a  determination  of  those  already  existing  in  the  circu- 
lating fluid,  towards  the   affected   spot;  but  partly  by  an   actual  increase  or 
generation  of  these  bodies,  which  appear  to  have  the  power  of  very  rapidly 
multiplying  themselves.     The  accumulation  of  Colourless  corpuscles  may  be 
easily  seen,  by  applying  irritants  to  the  web  of  a  'Frog's  foot.     Mr.  Addison 
has  noticed  it  in  the  Human  subject,  in  blood  drawn  by  the  prick  of  a  needle 
from  an  inflamed  pimple,  the  base  of  a  boil,  the  skin  in  scarlatina,  &c.     And 
the  Author,  without  any  knowledge  of  these  observations,  had  remarked  a 
very  obvious  difference  between  the  proportions  of  Colourless  corpuscles,  in 
blood  drawn  from  a  wound  in  the  skin  of  a  Frog  immediately  upon  the  in- 
cision being  made,  and  in  that  drawn  a  few  minutes  after ;  and  had  been  led, 
like  the  observers  just  quoted,  to  refer  this  difference  to  a  determination  of 
Colourless  corpuscles  to  a  part  irritated.     The  absolute  increase,  sometimes 
to  a  very  considerable  amount,  in  the  quantity  of  Colourless  corpuscles  in  the 
blood  of  an  inflamed  subject,  has  been  verified  by  Mr.  Gulliver  and  several 

*  [Elements  of  Physiology,  translated  by  R.  Willis.] 

|-  Medical  Gazette,  Dec.  1840;  Jan.  and  March,  1841. 

£  Medical  Gazette,  July,  1841 ;  and  Principles  of  Medicine,  [Am.  Ed.,  by  Dr.  Clymer,  pp. 


136  ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 

other  observers.  These  facts,  therefore,  afford  strong  ground  for  the  belief, 
that  the  production  of  Fibrine  'in  the  blood  is  closely  connected  with  the  de- 
velopment of  the  Colourless  corpuscles ;  and  when  we  consider  them  in  con- 
nection with  the  facts  previously  urged,  there  scarcely  appears  to  be  a  rea- 
sonable doubt  that  the  elaboration  of  Fibrine  is  a  consequence  of  this  form  of 
cell-life,  and  is,  in  fact,  its  express  object. 

159.  This  view  derives  further  confirmation  from  the  following  recent 
experiment  of  Mr.  Addison's.*  "  Provide  six  or  eight  slips  of  glass,  such  as 
are  usually  employed  for  mounting  microscopical  objects ;  and  as  many 
smaller  pieces.  Having  drawn  blood  from  a  person  with  rheumatic  fever, 
or  any  other  inflammatory  disease,  place  a  drop  of  the  colourless  liquor  san- 
guinis,  before  it  fibrillates,  on  each  of  the  large  slips  of  glass ;  cover  one  im- 
mediately with  one  of  the  smaller  slips,  and  the  others  one  after  another  at 
intervals  of  thirty  or  forty  seconds:  then,  on  examining  them  by  the  micro- 
scope, the  first  will  exhibit  colourless  blood-corpuscles  in  various  conditions, 
and  numerous  white  molecules  distributed  through  a  more  or  less  copious 
fibrous  network ;  and  the  last  will  be  a  tough,  coherent,  and  very  elastic 
membrane,  which  cannot  be  broken  to  pieces  nor  resolved  into  smaller  frag- 
ments, however  roughly  or  strongly  the  two  pieces  of  glass  be  made  to  rub 
against  each  other.  This  is  a  '  glaring  instance'  of  a  compact,  tough,  elastic, 
colourless,  and  fibrous  tissue,  forming  from  the  colourless  elements  of  the 
blood ;  and  the  several  stages  of  its  formation  may  be  actually  seen  and 
determined.  Numerous  corpuscles  may  be  observed,  in  all  these  prepara- 
tions, to  have  resolved  themselves,  or  to  have  fallen  down  into  a  number  of 
minute  molecules,  which  are  spread  out  over  a  somewhat  larger  area  than  that 
occupied  by  the  entire  corpuscles ;  and  although  still  retaining  a  more  or  less 
perfectly  circular  outline,  yet  refracting  the  light  at  their  edges,  in  a  manner 
very  different  from  that  in  which  the  corpuscles  themselves  are  seen  to  do. 
It  is  from  these  and  various  other  larger  and  more  irregular  masses  of  mole- 
cules or  disintegrated  corpuscles,  that  the  fibrinous  filaments  shoot  out  on  all 
sides,  as  from  so  many  centres  ;  or  frequently  the  filaments  are  more  copious 
in  two  opposite  directions." 

a.  A  different  view  of  the  cause  of  the  production  of  Fibrine,  however,  has  been  enter- 
tained by  some  eminent  Physiologists ;  and  it  does  not  seem  right  to  allow  the  opinions  of 
Wagner,  Henle,  and  Wharton  Jones  to  pass  without  notice,  even  though  they  appear  to  the 
Author  to  be.  easily  set  aside.  By  these  observers,  the  elaboration  of  Fibrine  has  been  at- 
tributed to  the  red  corpuscles,  and  has  been  regarded  as  one,  at  least,  of  their  special  func- 
tions. Nearly  all  the  arguments,  however,  which  have  led  us  to  assign  this  duty  to  the 
Colourless  corpuscles,  tell  equally  against  the  doctrine  now  under  consideration. — In  the  first 
place,  the  contents  of  the  Red  corpuscles  have  no  resemblance  whatever  to  liquid  Fibrine  j 
but  are  characterized  by  the  presence  of  a  substance  altogether  different:  whilst,  as  shown 
above,  the  Colourless  corpuscles" emit,  on  bursting,  a  fibrillating  matter.  If,  then,  Fibrine  be 
elaborated  by  the  Red  corpuscles,  it  must  be  by  forming  part  of  their  walls :  a  method  alto- 
gether unusual. — Again,  the  entire  absence  of  Red  corpuscles  in  the  blood  of  the  lower 
Invertebrata,  and  in  that  of  the  larva  and  pupa  of  the  Insect,  the  small  proportion  in  which 
they  are  present  in  the  blood  of  any  Invertebrata,  and  their  occurrence  to  any  large  amount 
in  the  blood  of  Vertebrata  only,  seem  to  show  that  they  cannot  be  Concerned  in  a  function 
so  constant  and  essential  as  the  elaboration  of  the  plastic  element.  The  number  of  the  Red 
corpuscles,  as  stated  above,  bears  a  regular  proportion  to  the  amount  of  oxygen  introduced 
into  the  system,  and  thus  to  the  heat  developed,  and  to  the  activity  of  the  Animal  functions  ; 
but  it  does  not  bear  the  same  relation  to  the  activity  of  the  formative  processes^  which  take 
place  most  energetically  in  a  state  of  functional  quiescence. — Further,  although  the  quantity 
of  Fibrine  is  so  remarkably  increased  in  Inflammation,  the  number  of  Red  corpuscles  under- 
goes no  decided  change.  Such  an  augmentation  is  even  compatible  with  a  Chlorotic  state  of 
the  blood ;  the  peculiar  characteristic  of  which  is  a  great  diminution  in  the  proportion  of  Red 
corpuscles.  By  such  alterations,  the  nprmal  proportion  between  the  Fibrine  and  the  Red 
corpuscles,  which  may  be  stated  as  A.  :  B,  may  be  so  much  altered  as  to  become,  in  Inflam- 

*  Transactions  of  the  Provincial  Medical  Association,  1843. 


EPIDERMIC  CELLS. 


137 


Fig.  31. 


mation,  4  A  :  B  ;  or,  in  Chlorosis,  A  :  J  B.  In  Fever,  the  characteristic  alteration  in  the  con* 
dition  of  the  blood,  appears  to  be  an  increase,  in  the  amount  of  Red  corpuscles,  with  a  dimi- 
nution in  the  quantity  of  Fibrine ;  yet  if  a  local  inflammation  should  establish  itself  during 
the  course  of  a  fever,  the  proportion  of  fibrine  will  rise ;  and  this  without  any  change  in  the 
amount  of  corpuscles. — Lastly,  the  effect  of  Loss  of  Blood  has  been  shown  by  Andral's  in- 
vestigations, to  be  a  marked  diminution  in  the  number  of  Red  corpuscles,  with  no  decided 
reduction  in  the  quantity  of  Fibrine,  even  when  this  is  much  above  its  normal  standard;  and 
in  this  condition  of  the  blood,  it  has  been  observed  by  Remak  that  the  Colourless  corpuscles 
are  very  numerous. 

6.   Of  Cells  developed  upon  Free  Surfaces. 

160.  Next  in  independence  to  the  cells  or  corpuscles  floating  in  the  animal 
fluids,  are  those  which  cover  the  free  membranous  surfaces  of  the  body,  and 
which  form  the  Epidermis  and  Epithelium.     Between  these  two  structures 
there  is  no  essential  difference,  either  in  regard  to  their  origin,  their  mode  of 
development,  their  situation,  or  their  individual  history ;  but  there  is  an  im- 
portant difference  in  the  purposes  which  they  respectively  serve  in  the  eco- 
nomy.    They  both  consist  of  cells,  which  are  developed  from  germs  furnished 
by  the  subjacent  membrane,  which  are  nourished  by  its  vessels,  and  which 
are  after  a  time  cast  off  from  its  free  surface  to  be  replaced  by  a  succeeding 
generation  ;  but  the  contents  of  the  cells  vary  in  different  situations,  and  give 
peculiar  characters  to  the  tissue.     The   differences,  however,  are  not  more 
striking  between  the  Epidermis,  or  cellular  covering  of  the  external  surface, 
and  the  Epithelium,  or  cellular  lining  of  the  internal  cavities,  than  those  which 
exist  between  the  different  portions  of  the  Epithelium  itself.     For  although 
the  Epidermis  is  distinguished  by  its  comparatively 

hard,  dry,  horny  character,  whilst  the  Epithelium 
is  soft,  moist,  and  deficient  in  tenacity ;  yet  we  shall 
hereafter  find  that,  as  all  the  Secretions  of  the  body 
are  elaborated  by  the  agency  of  the  cells  of  the 
latter,  there  must  be  as  many  varieties  of  endow- 
ment, in  these  important  bodies,  as  there  are  differ- 
ences in  the  results  of  their  action. 

161.  The  Epidermis, — which  usually  forms   a 
thin  semi-transparent  pellicle,  in  close   apposition 
with  the  surface  of  the  true  Skin,  but  occasionally 
presents  a  great  increase  in  thickness, — consists  of 
a  series  of  flattened  scale-like  cells ;  which,  when 
first  formed,  are  spherical ;  but  which  gradually  dry 
up,  their  nucleus  usually  remaining  visible.     These 
form  several  layers ;  of  which  the  deeper  can  be 
seen  very  distinctly  to  possess  the  cellular  character, 
whilst  the  external  layers  are  scaly ;  and  between 
these,  all  stages  of  transformation  may  be  traced. 
The  outer  layers  are  continually  being  thrown  off 
by  desquamation  ;  and  new  ones  are  as  constantly 
being  formed  below.     They  would  seem  to  origi- 
nate in  germs  supplied  by  the  basement-membrane, 
on  whose  surface  they  make  their  first  appearance; 
and  their  continued  development  takes  place  at  the 
expense  of  nutriment,  which  they  draw  through 
that  membrane,  from  the  subjacent  vessels.     The 
Epidermis    is  not   itself  traversed   by  vessels   or 
nerves ;  but  it  is  pierced  by  the  excretory  ducts  of 
the  sebaceous  and  sweat  glands,  and  also  by  the 
shafts  of  the  hairs ;  being,  however,  at  the  same 

12* 


Vertical  section  of  Epidermis, 
from  palm  of  the  hand ;  a,  outer 
portion,  composed  of  flattened 
scales ;  6,  inner  portion,  consist- 
ing of  nucleated  cells ;  c,  tortu- 
ous perspiratory  tube,  cut  across 
by  the  section  higher  up.  Mag- 
nified 155  diameters. 


138  ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 

time  continuous  with  the  epithelial  linings  of  these.  The  soft  layer  which 
lies  in  immediate  contact  with  the  true  skin,  was  formerly  supposed  to  be  a 
substance  of  distinct  nature,  and  was  described  under  the  name  of  rete  muco- 
sum  ;  it  has  been  proved  by  microscopic  examination,  however,  to  consist  of 
the  same  elements  with  the  ordinary  epidermis,  in  an  early  stage  of  their 
development;  and,  so  far  from  being  the  exclusive  seat  of  the  colour  of  the 
skin,  as  was  formerly  supposed,  it  only  participates  with  the  fully-formed 
epidermis  in  the  possession  of  pigment-cells  (§  163).  The  thickness  of  the 
Epidermis,  and  consequently  the  number  of  layers  of  which  it  is  composed, 
vary  greatly  in  different  parts ;  being  usually  found  to  be  greatest,  where  there 
is  most  pressure  or  friction, — as  on  the  palms  of  the  hands  of  the  labouring 
man,  and  on  the  soles  of  the  feet,  particularly  at  the  heel,  and  the  ball  of  the 
great  toe.  It  would  seem  as  if  the  irritation  of  the  true  skin  produced  an 
augmented  determination  of  blood  to  the  part,  and  consequently  an  increased 
development  of  epidermic  cells.  The  Epidermis  covers  the  whole  exterior  of 
the  body,  not  excepting  the  Cornea  and  the  Conjunctival  membrane;  on  the 
latter,  however,  it  has  more  the  character  of  an  Epithelium.  This  continuity 
is  well  seen  in  the  cast  skin  or  slough  of  the  Snake ;  in  which  the  covering 
of  the  front  of  the  eye  is  found  to  be  as  perfectly  exuviated  as  that  of  any  part 
of  the  body. 

162.  The  Epidermis  appears  solely  destined  for  the  protection  of  the  true 
Skin,  from  the  mechanical  injury  and  the  pain   occasioned  by  the  slightest 
abrasion,  and  from  the  irritating  influence  of  exposure  to  air  and  of  changes 
of  temperature.     We  perceive  the  value  of  this  protection,  when  the  Epider- 
mis has  been  accidentally  removed.     It  is  very  speedily  replaced,  however; 
the  increased  determination  of  blood  to  the  Skin,  which  is  the  consequence  of 
the  irritation,  being  favourable  to  the  rapid  production  of  Epidermic  cells  from 
its  surface.     The  peculiar  character  of  the  tissue  appears  to  depend  upon  the 
property  possessed  by  its  cells,  of  secreting  horny  matter  into  their  cavity  ; 
and  this  process  seems  to  take  place  at  a  period  subsequent  to  the  first  forma- 
tion of  the  cells.     For  if  a  thin  vertical  section  of  the  Epidermis  be  treated 
with  Acetic  acid,  or  with  a  strong  solution  of  Potass,  it  is  found  that  the  inner 
newly-formed  layers  are  dissolved  by  the  re-agent,  whilst  the  outer  or  scaly 
ones  are  unaffected.     Recent  analysis  has  shown,  that  the  dense  Epidermis 
from  the  sole  of  the  foot,  and  the   compact  Horny  matter  of  which  Nails, 
Hoofs,  Horns,  Hair,  and  Wool,  are  composed,  have  the  same  composition; 
the  formula  of  all  of  them  being  48  Carbon,  39  Hydrogen,  7  Nitrogen,  and 
17  Oxygen.     It  is  probable  that,  here  as  elsewhere,  if  we  could  isolate  the 
wall  of  the  cell  from  its  contents,  we  should  find  the  former  to  consist  of  a 
proteine-compound. 

163.  Mingled  with  the  Epidermic  cells,  we  find  others  which  secrete  Co- 
louring-matter instead  of  Horn  ;  these  are  termed  Pigment-cells.     They  are 
not  readily  distinguishable  in  the  Epidermis  of  the  fair  races  of  mankind, 
except  in  certain  parts,  such  as  the  areola  around  the  nipple,  and  in  freckles, 
naevi,  &c.     But  they  are  very  obvious,  on  account  of  their  dark  hue,  in  the 
newer  layers  of  the  Epidermis  of  the  Negro  and  other  coloured  races ;  .and, 
like  true  Epidermic  cells,  they  dry  up  and  become  flattened  scales  in  passing 
towards  the  surface,  thus  constantly  remaining  dispersed  through  its  substance, 
and  giving  it  a  dark  tint  when  it  is  separated  and  held  up  to  the  light.     In  all 
races  of  men,  however,  we  find  the  most  remarkable  development  of  Pigment- 
cells  on  the  inner  surface  of  the  Choroid  coat  of  the  eye :  where  they  form 
several  layers,  known  as  the  Pigmentum  nigrutn.     When  examined  sepa- 
rately, these  are  found  to  have  a  polygonal  form,  and  to  have  a  distinct  nucleus 
in  their  interior.     The  black  colour  is  given  by  the  accumulation,  within  the 
cell,  of  a  number  of  flat,  rounded  or  oval  granules,  measuring  about  1-20, 000th 


PIGMENT-CELLS. 


139 


of  an  inch  in  diameter,  and  a  quarter  as  much  in  thickness ;  these,  when 
separately  viewed,  are  observed  to  be  transparent,  not  black  and  opaque  ;  and 


[Fig.  32. 


Fig.  33. 


B 


A.  Choroid  Epithelium,  with  the  cells  filled  with 
pigment,  except  at  a,  where  the  nuclei  are  visi- 
ble. The  irregularity  of  the  pigment-cells  is  seen. 
b.  Grains  of  pigment. 

B.  Pigment-cells  from  the  substance  of  the  Cho- 
roid.   A  detached  nucleus  is  seen.    Magnified 
320  diameters.] 


Cells  from  Pigmentum  Ni- 
grum;  a,  pigmentary  gra- 
nules concealing  the  nu- 
cleus; fc,  the  nucleus  distinct. 
Magnified  410  diameters. 


they  exhibit  an  active  movement  when  set  free  from  the  cell,  and  even  whilst 
inclosed  within  it. — The  Pigment-cells  are  not  always  of  a  simple  rounded  or 
polygonal  form;  they  sometimes  present  remarkable  stellate  prolongations, 
such  as  those  seen  in  the  skin  of  the  Frog  (Fig.  88) ;  and  occasionally,  the 
cells  being  more  nearly  approximated  to  each  other,  these  prolongations  com- 
municate, so  as  to  form  a  kind  of  network. — The  Chemical  nature  of  the  Black 
pigment  has  not  yet  been  distinctly  ascertained ;  it  has  been  shown,  however, 
to  have  a  very  close  relation  with  that  of  the  Cuttle-fish  ink,  or  Sepia,  which 
derives  its  colour  from  the  pigment-cells  of  the  ink-bag;  and  to  include  a 
larger  proportion  of  carbon  than  most  other  organic  substances, — every  100 
parts  containing  58|  of  that  element. 

164.  It  cannot  be  doubted  that  the  development  of  the  Pigment-cells  of 
the  skin  is  very  much  influenced  by  exposure  to  light ;  and  in  this  respect 
there  is  a  remarkable  correspondence  between  Animals  and  Plants, — the 
coloration  of  the  latter,  as  is  well  known,  being  entirely  due  to  that  agent. 
Thus,  it  is  a  matter  of  familiar  experience,  that  the  influence  of  light  upon 
the  skin  of  many  individuals,  causes  it  to  become  spotted  with  brownfreckles  ; 
these  freckles  being  aggregations  of  brown  pigment-cells,  which  either  owe 
their  development  to  the  stimulus  of  light,  or  are  enabled  by  its  agency  to 
perform  a  decided  chemical  transformation,  which  they  could  not  otherwise 
effect.  In  like  manner,  the  swarthy  hue,  which  many  Europeans  acquire 
beneath  exposure  to  the  sun  in  tropical  climates,  is  due  to  a  development  of 
dark  pigment-cells,  and  to  this  we  usually  find  the  greatest  disposition  in  in- 
dividuals or  races,  that  are  already  of  a  somewhat  dark  complexion.  The 
deep  blackness  of  the  Negro  skin  seems  dependent  upon  nothing  else  than  a 
similar  cause,  operating  through  successive  generations  (§  80).  It  is  well 
known  that  the  new-born  infants  of  the  negro  and  other  dark  races,  do  not  ex- 
hibit nearly  the  same  depth  of  colour  in  their  skins,  as  that  which  they  present 
after  the  lapse  of  a  few  days,  when  light  has  had  time  to  exert  its  influence 
upon  their  surface  ;  and  further,  that  in  those  individuals  who  keep  them- 
selves during  life  most  secluded  from  its  influence,  we  observe  the  lightest 
hue  of  the  epidermis.  Thus  among  the  intertropical  nations,  the  families  of 
Chiefs,  which  are  not  exposed  to  the  sun  in  the  same  degree  with  the  com- 


140 


ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 


[Fig.  34. 


mon  people,  almost  always  present  a  lighter  hue  ;  and  in  some  of  the  islands 
of  the  Polynesian  Archipelago,  bordering  on  the  Equator,  they  are  not  darker 
than  the  inhabitants  of  Southern  Europe. — An  occasional  development  of  dark 
pigment-cells  takes  place  during  pregnancy,  in  some  females  of  the  fair  races ; 
thus  it  is  very  common  to  meet  with  an  extremely  dark  and  broad  areola 
round  the  nipple  of  pregnant  women  ;  and  sometimes  large  patches  of  the 
cutaneous  surface,  on  the  lower  part  of  the  body  especially,  become  almost 
as  dark  as  the  skin  of  a  Negro.- — On  the  other  hand,  individuals  are  occasion- 
ally seen  with  an  entire  deficiency  of  pigment-cells,  or  at  least  of  their  proper 
secretion ;  and  this  not  merely  in  the  skin,  but  in  the  eye ;  such  are  termed 
Albinoes  ;  and  they  are  met  with  alike  among  the  fair,  and  among  the  dark 
races.  The  absence  of  colour  usually  shows  itself  also  in  the  hair ;  which 
is  almost  white. 

165.  The  Nails,  like  Hoof,  Horn,  &c.,  may  be  regarded  as  nothing  more 
than  an  altered  form  of  Epidermis.  When  their  newest  and  softest  portions 
are  examined,  they  are  found  to  consist  of  nucleated  particles,  resembling 
those  of  the  newer  layers  of  Epidermis ;  in  the  more  superficial  laminae, 
however,  no  distinct  structure  can  be  made  out;  but,  when  treated  with  acetic 
acid,  some  traces  of  nuclei  may  be  detected  in  them.  The  Nail  is  produced 
from  the  surface  of  the  true  skin  that  lies  beneath  it,  which  is  folded  into  a 

groove  at  its  root;  this  surface  is  highly  vascular. 
The  increase  in  length  is  effected  by  successive 
additions  at  the  root,  causing  the  whole  nail  to 
shift  onwards  ;  but  as  it  moves,  it  receives  ad- 
ditional layers  from  the  subjacent  skin,  which 
increases  its  thickness.  The  nail  is  continuous 
with  the  true.  Epidermis  at  every  part,  except 
its  free  projecting  edge ;  and  in  the  foetus,  the 
continuity  is  maintained  there  also. 

166.  The  Hair,  as  originally  consisting  of 
Epidermic  cells,  may  be  properly  described 
here  ;  although,  when  fully  formed,  it  departs 
widely  (in  Man  at  least)  from  the  cellular  type. 
It  has  been  imagined  until  recently,  that  the 
Hair,  in  common  with  the  other  Epidermic  tis- 
sues, is  a  mere  product  of  secretion ;  its  mate- 
rial, which  is  chiefly  horny  matter  of  the  same 
composition  with  that  of  the  Epidermis  and  its  appendages,  being  elaborated 
from  the  surface  of  the  pulp  at  its  base.  It  is  not  known,  however,  to  con- 
tain a  distinctly  organized  structure ;  and  to  be  formed  by  the  conversion  of 
a  cellular  mass  at  its  root.  The  Hair  originates  within  a  follicle,  which  is 
formed  by  a  little  depression  of  the  Skin,  and  which  is  lined  by  a  continua- 
tion of  the  Epidermis.  From  the  bottom  of  this  follicle,  there  rises  up  a 
cluster  of  cells,  which  may  be  regarded  as  an  increased  development  of  Epi- 
dermic cells  ;  the  exterior  of  this  cluster,  which  is  the  densest  part,  is  known 
as  the  bulb  ;  whilst  the  softer  interior  is  termed  the  pulp.  The  follicle  itself 
is  extremely  vascular  ;  and  even  the  bulb  is  reddened  by  minute  injection, 
though  no  distinct  vessels  can  be  traced  into  it. — Although  the  Hairs  of  differ- 
ent animals  vary  considerably  in  the  appearances  they  present,  we  may  gene- 
rally distinguish  in  them  two  elementary  parts ; — a  cortical  or  investing  sub- 
stance, of  a  fibrous  horny  texture  ;  and  a  medullary  or  pith-like  substance, 
occupying  the  interior.  The  fullest  development  of  both  substances  is  to  be 
found  in  the  spiny  Hairs  of  the  Hedgehog,  and  in  the  quills  of  the  Porcu- 
pine ;  which  are  but  hairs  on  a  magnified  scale.  The  cortical  substance 
forms  a  dense  horny  tube,  to  which  the  firmness  of  the  structure  seems  chiefly 


Section  of  the  skin  on  the  end  of 
the  finger:— The  cuticle,  and  nail,  n, 
detached  from  the  cutis  and  matrix,  m.} 


STRUCTURE  OF  HAIR. 


141 


due ;  whilst  the  medullary  substance  is  composed  of  an  aggregation  of  very 
large  cells,  which  seem  not  to  possess  any  fluid  contents  in  the  part  of  the 
hair  which  is  completely  formed.  The  structure  of  the  feather  of  Birds  is 
precisely  analogous ;  the  cortical  horny  tube  existing  alone  in  the  quill ;  but 
being  filled  with  a  cellular  medulla  in  the  stem  of  the  feather  itself.  In  the 
hair  of  the  Mouse  and  other  small  Rodents,  we  see  the  horny  tube  crossed 
at  intervals  by  partitions,  which  are  sometimes  complete,  sometimes  only  par- 
tial ;  these  are  the  walls  of  the  single  or  double  line  of  cells,  of  which  the 
medullary  substance  is  made  up.  In  the  Sable,  we  sometimes  meet  with 
hairs,  in  which  the  medulla  is  made  up  of  rounded  cells ;  whilst  the  cortical 
substance  is  composed  of  imbricated  Epidermic  scales  (Fig.  35,  B).  In  some 
instances,  however,  there  is  scarcely  any  medulla  to  be  traced ;  whilst  in 
other  animals,  as  the  Musk-deer  (Fig.  35,  A),  the  entire  hair  seems  to  be  made 
up  of  it. 


Fig.  35. 


[Fig.  36. 


A,  hair  of  Musk-Deer 
consisting  almost  entirely 
of  polygonal  cells;  B,  hair 
of  Sable,  showing  large 
rounded  cells  in  its  inte- 
rior, covered  by  imbrica- 
ted scales,  or  flattened 
cells. 


Bulb  of  a  small  black  hair,  from  the  scrotum,  seen 
in  section,  a.  Basement  membrane  of  the  follicle,  b. 
Layer  of  epidermic  cells  resting  upon  it,  and  becoming- 
more  scaly  as  they  approach  c,  a  layer  of  imbricated 
cells,  forming  the  outer  lamina,  or  cortex,  of  the  hair. 
These  imbricated  cells  are  seen  more  flattened  and 
compressed,  the  higher  they  are  traced  on  the  bulb. 
Within  the  cortex  is  the  proper  substance  of  the  hair, 
consisting  at  the  base,  where  it  rests  on  the  base- 
ment membrane,  of  small  angular  cells  scarcely  larger 
than  their  nuclei.  At  d,  these  cells  are  more  bulky, 
and  the  bulb  consequently  thicker ;  there  is  also  pig- 
ment developed  in  many  of  them  more  or  less  abun- 
dantly. Above  d,  they  assume  a  decidedly  fibrous  cha- 
racter, and  become  condensed,  e.  A  mass  of  cells  in 
the  axis  of  the  hair,  much  loaded  with  pigment] 


167.  In  the  Human  hair,  the  representation  of  the  cortical  sheath  of  the  hair 
of  other  animals  is  found  in  a  thin  transparent  horny  film  ;  which  is  composed 
of  flattened  cells  or  scales,  arranged  in  an  imbricated  manner,  their  edges 
(Fig.  36)  forming  delicate  lines  upon  the  surface  of  the  hair,  which  are  some- 
times transverse,  sometimes  oblique,  and  sometimes  apparently  spiral  (Fig. 
37,  A).  Within  this,  we  find  a  cylinder  of  fibrous  texture  ;  which  forms  the 


142 


ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 


principal  part  of  the  shaft  of  the  hair  ;  whilst  the  centre  is  frequently  more 
distinctly  cellular.  The  constituent  fibres  of  the  shaft  are  marked  out  by 
delicate  longitudinal  striae,  which  may  be  traced  in  vertical  sections  of  the 
hair  (Fig.  37,  B.)  ;  but  they  may  be  still  more  completely  demonstrated  by 
crushing  the  hair,  after  it  has  been  macerated  for  some  time  in  dilute  acid. 
In  dark  hairs,  pigmentary  granules  are  frequently  scattered  between  the  fibres; 
but  they  are  usually  found  in  greater  abundance  in  the  central  cells.  The 
Hair  of  Man  is  commonly  reputed  to  be  tubular ;  but  this  is  seldom  if  ever 
the  case,  as  is  shown  by  microscopical  examination  of  thin  transverse  sec- 
tions (Fig.  37,  c).  The  mistake  has  arisen  from  a  misinterpretation  of  the 
appearance  of  a  dark  band  in  the  interior  of  the  hair,  when  viewed  by  trans- 
mitted light ;  which  is  really  due,  partly  to  the  presence  of  pigmentary  mat- 
ter in  the  central  portion  of  the  shaft,  and  partly  to  the  refraction  of  light  by 
the  cylindrical  surface. — The  chemical  composition  of  Hair,  as  already  stated, 


Structure  of  Human  Hair;  A,  external  surface  of  the  shaft,  showing  the  transverse  striae  and  jagged 
boundary,  caused  by  the  imbrications  of  the  scaly  cortex  ;  B,  longitudinal  section  of  the  shaft,  showing 
the  fibrous  character  of  the  medullary  substance,  and  the  arrangement  of  the  pigmentary  matter;  c, 
transverse  sections,  showing  the  distinction  between  the  cortical  and  medullary  substance,  and  the  cen- 
tral collection  of  pigmentary  matter,  sometimes  found  in  the  latter.  Magnified  310  diameters. 

is  precisely  the  same  with  that  of  the  horny  Epidermis  (§  162).  Its  colour- 
ing matter  seems  related  to  HaBinatine ;  it  is  bleached  by  Chlorine ;  and  its 
hue  appears  to  be  dependent  in  part  upon  the  presence  of  iron,  which  is  found 
in  larger  proportion  in  dark  than  in  light  hair. 

168.  The  real  nature  of  the  different  elements  of  the  Hair  is  ascertained, 
by  examining  them  at  its  base,  where  they  become  continuous  with  those  of 
the  bulb.  It  is  then  seen,  that  the  fibres  of  the  shaft  are  identical  with  the 
cells  of  the  bulb ;  these  undergoing  elongation,  as  they  are  pushed  upwards 
towards  the  mouth  of  the  follicle,  by  the  development  of  additional  cells  be- 
neath ;  and  being  proportionably  diminished  in  diameter.  Hence  the  shaft  of 
the  hair  is  considerably  narrower  than  the  bulb.  The  central  part  of  the  hair 
which  more  distinctly  exhibits  the  cellular  character,  is  derived  from  the  pulp 
or  internal  portion  of  the  bulb ;  whose  constituent  cells  undergo  Tess  change. 
And  the  imbricated  layer  of  cells,  that  forms  its  fibrous  envelope,  may  be  said 
to  be  a  prolongation  of  the  ordinary  Epidermis  over  the  surface  of  the  hair ; 
being  developed  from  the  external  portion  of  the  bulb,  where  it  is  continuous 
with  the  epidermic  lining  of  the  follicle. — Thus  we  see  that  the  whole  tissue 
of  the  Hair  is  derived  from  Epidermic  cells,  developed  in  peculiar  abundance 
from  the  base  of  the  follicle ;  some  of  these  cells,  however,  retaining  their 
original  form  ;  whilst  others  are  transformed  into  fibres,  and  others  converted 
(like  those  of  ordinary  Epidermis)  into  flattened  cells.  They  all  have  the 
power,  however,  of  drawing  horny  matter  into  their  cavities  ;  and  resist  the 


STRUCTURE  OF  HAIR. EPITHELIUM.  143 

solvent  power  of  chemical  re-agents,  except  when  these  are  employed  in  un- 
usual strength. — The  Hair  is  constantly  undergoing  elongation,  by  the  addi- 
tion of  new  substance  at  its  base;  and  the  part  which  has  been  once  fully 
formed,  and  which  has  emerged  from  the  follicle,  usually  undergoes  no  sub- 
sequent alteration.  There  is  evidence,  however,  that  it  may  be  affected  by 
changes  at  its  base,  the  effect  of  which  is  propagated  along  its  whole  extent : 
thus,  it  is  well  known  that  cases  are  not  unfrequent,  in  which,  under  the  in- 
fluence of  strong  mental  emotion,  the  whole  of  the  hair  has  been  turned  to 
gray,  or  even  to  a  silvery  white,  in  the  course  of  a  single  night;  a  change 
which  can  scarcely  be  accounted  for  in  any  other  way  than  by  supposing  that 
a  fluid,  capable  of  chemically  affecting  the  colour,  is  secreted  at  the  base  of 
the  hair,  and  transmitted  by  imbibition  through  the  medullary  substance  to 
the  opposite  extremity.  Another  evidence  of  their  retention  of  a  degree  of 
vitality,  is  found  in  the  fact  of  Hairs  having  a  tendency  to  become  pointed,' 
after  having  been  cut  short  off.  In  the  hairs  of  some  animals  (particularly 
the  whiskers  of  the  Seal  and  other  Carnivora)  the  base  is  hollow,  and  con- 
tains a  true  papilla,  or  elevation  of  the  cutis,  furnished  with  nerves  and  blood- 
vessels ;  this  is  separated  by  a  layer  of  basement-membrane  from  the  proper 
tissue  of  the  Hair.  In  such  cases,  there  is  bleeding  from  the  stumps  of  the 
hairs,  when  they  are  shaved  off  close  to  the  skin.  There  is  an  approach  to 
this  papillary  structure  in  Man;  and  it  may  perhaps  be  an  abnormal  develop- 
ment of  it,  which  occasions  the  hair  to  bleed  in  the  disease  termed  Plica  Po- 
lonica.  The  hair  of  individuals  affected  with  it  is  further  disposed  to  split 
into  fibres,  often  at  a  considerable  distance  from  the  roots,  and  to  exude  a 
glutinous  substance ;  these  two  causes  unite  in  occasioning  that  peculiar  mat- 
ting of  the  hair,  which  has  given  origin  to  the  name  of  the  disease. 

169.  The  layer  of  cells  covering  the  internal  free  surfaces  of  the  body,  is 
known  under  the  name  of  Epithelium.    In  some  instances  it  appears  to  serve 
to  the  subjacent  membranes,  like  the  Epidermis  to  the  Cutis,  merely  as  a  pro- 
tection; whilst  in  other  cases,  as  we  shall  presently  find,  it  answers  purposes 
of  far  greater  importance.     It  has  long  been  known  that  the  epidermic  layer 
might  be  traced  continuously  from  the  lips  to  the  mucous   membrane  of  the 
mouth,  and  thence  down  the  oesophagus   into  the  stomach ;   and  that,  in  the 
strong  muscular  stomach  or  gizzard  of  the  granivorous  birds,  it  becomes  quite 
a  firm  horny  lining.     But  it  has  been  only  since   the  application  of  the  Mi- 
croscope to  this  investigation,  that  a  continuous  layer  of  cells  has  been  traced, 
not  mereTy  along  the  whole   surface  of  the  mucous  membrane  lining  the  ali- 
mentary canal,  but  likewise  along  the  free  surfaces  of  all  other  Mucous  Mem- 
branes, with  their  prolongations  into  follicles  and  glands ;   as  well  as  on  the 
Serous  and  Synovial  membranes,  and  the  lining  membrane  of  the  heart,  blood- 
vessels, and  absorbents. 

170.  The  forms  presented  by  the  Epithelium  cells  are  various.     The  two 
chief,  however,  are  the  tesselated,  forming  the  pavement- epithelium;  and  the 
cylindrical,  forming  the   cylinder-epithelium. — The   Tesselated  Epithelium 
covers  the  serous  and  synovial  membranes,  the  lining  membrane  of  the  blood- 
vessels, and  the  ultimate  follicles  or  tubuli  of  most  glandular  structures  con- 
nected with  the  skin  or  mucous  membranes,  as  also  the  mucous  membranes 
themselves,  where  the  cylinder-epithelium  does  not  exist.     The  cells  compos- 
ing it  are  usually  flattened  and  polygonal  (Fig.  38,  A.)  so  as  to  come  into  con- 
tact with  each  other  at  their  edges,  like  the  pieces  of  a  tesselated  pavement 
(Fig.  30) ;  but  they  sometimes  retain  their  rounded  or  oval  form,  and  are  se- 
parated from  each  other  by  considerable  interstices.   (Fig.  38,  B.)     This  last 
form  seems  to  be  the  commonest,  where  the  cells  are  most  actively  renewed, 
so  that  they  have  not  time  (so  to  speak)  to  be  developed  into  a  continuous 
stratum.     The  number  of  layers  is  commonly  small;  and  sometimes  there  is 


144 


ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 


only  a  single  one. — The  Cylinder-Epithelium  is  very  differently  constituted. 
Its  component  cells  are  cylinders,  which  are  arranged  side  by  side ;  one  extre- 


Fig.  38. 


B. 


Separated  Epithelium  cells,  a,  with 
nuclei,  6,  and  nucleoli,  c,  from  mucous 
membrane  of  mouth. 


Pavement-Epithelium  of 
the  Mucous  Membrane  of  the 
smaller  bronchial  tubes;  a, 
nuclei  with  double  nucleoli. 


mity  of  each  cylinder  resting  upon  the  basement-membrane,  whilst  the  other 
forms  part  of  the  free  surface.  The  perfect  cylindrical  form  is  only  shown, 
however,  when  the  surface  on  which  the  cylinders  rest  is  flat  or  nearly  so. 
When  it  is  convex,  the  lower  ends  or  basements  of  the  cells  are  of  much  smaller 
diameter  than  the  upper  or  free  extremities ;  and  thus  each  has  the  form  of  a 
truncated  cone,  rather  than  of  a  cylinder ;  as  is  well  seen  on  the  cells  covering 
the  villi  of  the  intestinal  canal.  (Fig.  45.)  On  the  other  hand,  where  the  cy- 
linder-epithelium lies  upon  a  concave  surface,  the  free  extremities  of  the  cells 
may  be  smaller  than  those  which  are  attached.  Sometimes  each  cylinder  is 
formed  from  more  than  one  cell,  as  is  shown  by  its  containing  two  or  more 
nuclei ;  although  its  cavity  seems  to  be  continuous  from  end  to  end.  And 
occasionally  the  cylinders  arise  by  stalk-like  prolongations,  from  a  pavement- 
epithelium  beneath.  The  two  forms  of  Epithelium  pass  into  one  another  at 
various  points ;  and  various  transition-forms  are  then  seen, — the  tesselated 
scales  appearing  to  rise  more  and  more  from  the  surface,  until  they  project  as 
long-stalked  cells,  truncated  cones,  or  cylinders.  The  Cylinder-Epithelium 
covers  the  mucous  membrane  of  the  alimentary  canal,  from  the  cardiac  orifice 
downwards  ;  it  is  found  also  in  the  larger  ducts  of  the  glands  which  open  into 
it,  or  upon  the  external  surface — such  as  the  ductus  choledochus,  the  salivary 
ducts,  those  of  the  prostate  and  Cowper's  glands,  the  vas  deferens,  and  urethra. 
In  all  these  situations,  it  comes  into  connection  with  the  Tesselated  Epithe- 
lium, which  usually  lines  the  more  delicate  canals  of  the  glands,  as  well  as 
their  terminal  follicles. 

171.  Both  these  principal  forms  of  Epithelial  cells  are  frequently  observed 
to  be  fringed  at  their  free  margins  with  delicate  filaments,  which  are  termed 
Cilio  ;  [from  cilium,  an  eyelash,]  and  these,  although  of  extreme  minuteness, 
are  organs  of  great  importance  in  the  animal  economy,  through  the  extraordi- 
nary motor  power  with  which  they  are  endowed.  The  form  of  the  Ciliary 

filaments  is  usually  a  little  flattened,  and  ta- 
pering gradually  from  the  base  to  the  point. 
Their  size  is  extremely  variable ;  the  largest 
that  have  been  observed  being  about  l-500th 
of  an  inch  in  length,  and  the  smallest  about 
l-13,000th.  When  in  motion,  each  fila- 
ment appears  to  bend  from  its  root  to  its 
point,  returning  again  to  its  original  state, 
like  the  stalks  of  corn  when  depressed  by 
the  wind ;  and  when  a  number  are  affected 
in  succession  with  this  motion,  the  appear- 
ance of  progressive  waves  following  one 


Fig,  39. 


Vibratile  or  ciliated  Epithelium  ;  a,  nu- 
cleated cells,  resting  on  their  smaller  ex- 
tremities ;  ft,  cilia. 


EPITHELIUM;  CILIARY  MOVEMENT. 


145 


another  is  produced,  as  when  a  corn-field  is  agitated  by  frequent  gusts. 
When  the  Ciliary  motion  is  taking  place  in  full  activity,  however,  nothing 
whatever  can  be  distinguished,  but  the  whirl  of  particles  in  the  surrounding 
fluid ;  and  it  is  only  when  the  rate  of  movement  slackens,  that  the  shape 
and  size  of  the  Cilia,  and  the  manner  in  which  their  stroke  is  made,  can  be 
clearly  seen.  The  motion  of  the  Cilia  is  not  only  quite  independent  (in  all 
the  higher  animals  at  least)  of  the  will  of  the  animal,  but  is  also  independent 
even  of  the  life  of  the  rest  of  the  body ;  being  seen  after  the  death  of  the 
animal ;  and  proceeding  with  perfect  regularity  in  parts  separated  from  the 
body.  The  isolated  epithelium  cells  have  been  seen  to  swim  about  actively 
in  water,  by  the  agency  of  their  cilia,  for  some  hours  after  they  have  been  de- 
tached from  the  mucous  surface  of  the  nose ;  and  the  Ciliary  movement  has 
been  seen  fifteen  days  after  -death  in  the  body  of  a  Tortoise,  in  which  putre- 
faction was  far  advanced.  In  the  gills  of  the  River-Mussel,  which  are  among 
the  best  objects  for  the  study  of  it,  the  movement  endures  with  similar  per- 
tinacity. 

172.  The  purpose  of  this  Ciliary  movement  is  obviously  to  propel  fluids 
over  the  surface  on  which  it  takes  place ;  and  it  is  consequently  limited  in 
the  higher  animals  to  the  internal  surfaces  of  the  body,  and  always  takes 
place  in  the  direction  of  the  outlets,  towards  which  it  aids  in  propelling  the 
various  products  of  secretion.  The  case  is  different,  however,  among  animals 
of  the  lower  classes,  especially  those  inhabiting  the  water.  Thus  the  external 
surface  of  the  gills  of  Fishes,  Tadpoles,  &c.,  is  furnished  with  cilia;  the  con- 
tinual movement  of  which  renews  the  water  in  contact  with  them,  and  thus 
promotes  the  aeration  of  the  blood.  In  the  lower  Mollusca,  and  in  many 
Zoophytes,  which  pass  their  lives  rooted  to  one  spot,  the  motion  of  the  Cilia 
serves  not  merely  to  produce  currents  for  respiration,  but  likewise  to  draw 
into  the  mouth  the  minute  particles  that  serve  as  food.  [Fig.  107,  2,  5.] 
And  in  the  free-moving  Animalcules, 

of  various  kinds,  the  Cilia  are  the  [Fig.  40. 

sole  instruments  which  they  possess, 
not  merely  for  producing  those  cur- 
rents in  the  water,  which  may  bring 
them  the  requisite  supply  of  air  and 
food,  but  also  for  propelling  their 
own  bodies  through  the  liquid  ele- 
ment. This  is  the  case,  too,  with 
many  larger  animals  of  the  class 
Acalepha  (Jelly  fish),  which  move 
through  the  water,  sometimes  with 
great  activity,  by  the  combined  ac- 
tion of  the  vast  numbers  of  cilia,  that 
clothe  the  margins  of  their  external 
surfaces.  In  these  latter  cases,  it 

11  'PI  /^1*l*  in.*-'      ^^t*-miAoov^ij    JLWJ.  y  ttvvvisct    c.',<  in^o,    ouwwuig    k;iUtX     fill      1C  31 

WOuld  seem  as  if  the    Ciliary  move-     and  in  motion;  2,  ciliated  epithelium  particles  from  the 

ment  were  more  under  the  control 
of  the  will  of  the  animal,  than  where 
it  is  concerned  only  in  the  organic 
functions.  In  what  way  the  will 
can  influence  it,  however,  it  does 
not  seem  easy  to  say ;  since  the 
ciliated  epithelium-cells  appear  to  be  perfectly  disconnected  from  the  surface 
on  which  they  lie,  and  cannot,  therefore,  receive  any  direct  influence  from 
their  nerves.  Of  the  cause  of  the  movement  of  the  Cilia  themselves,  no  ac- 
count can  be  given  ;  they  are  usually  far  too  small  to  contain  even  the  minutest 
13 


^xamplesof  Cilia;  l,poriionof  abarofthe  gtllof 
the  sea-mussel,  Mytilus  edulis,  showing  ciha  at  rest 


frog's  mouth;  3,  ciliated  epithelium  particles  from  in- 
ner surface  of  human  membrana  tympani ;  4,  ditto, 
ditto,  from  the  human  bronchial  mucous  membrane  • 
5,  Leucophrys  patula,  a  polygastric  infusory  animal- 
cule; to  show  its  surface  covered  with  cilia,  and  the 
mouth  surrounded  by  them.] 


146  ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 

fibrillae,  of  muscle;  and  we  must  regard  them  as  being,  like  those  fibrillae, 
organs  sui  generis,  having  their  own  peculiar  endowment, — which  is,  in  the 
higher  animals  at  least,  that  of  continuing  in  ceaseless  vibration,  during  the 
whole  term  of  the  life  of  the  cells  to  which  they  are  attached. 

[That  this  movement  is  truly  molecular  and  independent  of  muscular  influence  and  of 
both  the  vascular  and  nervous  systems  has  been  proved  by  experiment.  For,  besides  continu- 
ing to  manifest  itself  in  a  single  particle  for  many  hours  a%r  it  has  been  isolated  from 
the  rest  of  the  system,  a  ciliated  surface  continues  unaffected  in  its  movements  though  the 
supply  of  blood  to  the  subjacent  tissues  be  completely  cut  off.  Neither  do  hydrocyanic 
acid,  opium,  strychnine,  belladonna,  substances  which  affect  powerfully  the  nervous  sys- 
tem, exert  any  influence  on  ciliary  motion ;  this  phenomenon  continuing  in  the  bodies  of 
animals  killed  by  these  poisons.  And  lastly,  shocks  of  electricity  passed  through  the  ciliated 
parts,  even  the  removal  of  the  brain  and  spinal  marrow  in  frogs,  extinguishing  as  it  does 
muscular  motion,  do  not  destroy  the  action  of  cilia. — M.  C.] 

The  length  of  time  during  which  the  Ciliary  movement  continues  after  the 
general  death  of  the  body,  is  much  less  in  the  warm-blooded  than  in  the  cold- 
blooded animals;  and  in  this  respect  it  corresponds  with  the  degree  of  per- 
sistence of  muscular  irritability,  and  of  other  vital  endowments. 

173.  A  layer  of  Ciliated  epithelium,  of  the  Tesselated  form,  is  found  upon 
the  delicate  pia  mater  which  lines  the  cerebral  cavities,  not  even  excepting  the 
infundibulum  and  the  aqueduct  of  Sylvius ;  and  it  is  also  found  in  the  termi- 
nal* ramifications  of  the  bronchial  tubes.     A  Cylindrical  epithelium  furnished 
with  Cilia  is  found  lining  the  nasal  cavities,  the  frontal  sinuses,  the  maxillary 
antra,  the  lachrymal  ducts  and  sac,  the  posterior  surface  of  the  velum  pendu- 
lum palati,  and  fauces,  the  Eustachian  tube,  the  larynx,  trachea,  and  bronchi 
to  their  finest  divisions,  the  upper  portion  of  the  vagina,  the  uterus,  and  the 
Fallopian   tubes.     The  function  of  the   Cilia  in  all  these  cases  appears  to  be 
the  same;  that  of  propelling  the  secretions,  which  would  otherwise  accumu- 
late on  these  membranes,  towards  the  exterior  orifices,  whence   they  may  be 
carried  off.    • 

174.  The  Epithelium-cells,  like  the  scales  of  the  Epidermis,  are  continually 
being  cast  off  and  renewed  from  the  subjacent  surface;  but  the  rapidity  of 
this  renewing  process  varies  according  to  the  particular  function  of  the  part. 
Thus  we  shall  hereafter  find   it  to  be  greater  on  the  Mucous   Membranes, 
which  are  actively  engaged  in  the  introduction  of  nutrient  materials  and  in  the 
separation  of  effete  matter,  than  it  is  on  the  Serous  surfaces,  which  are  com- 
paratively inert.     The  epithelial  cells  that  cover  the  plane  surfaces,  seem  to 
be  developed  from  granular  germs,  scattered  through  the  subjacent  basement 
membrane ;  but  it  is  different  in  regard  to  the  cells  of  the  glandular  follicles, 
which  usually  seem  to  originate  in  a  single  "  germinal  spot,"  composed  of  a 
mass  of  granules,  at  the  blind  extremity  of  the  follicles.     In  fact,  each  of  these 
follicles  may  be  regarded   as   a  parent-cell,  which  was   closed   at  an   earlier 
period  of  its  existence,  and  which,  even  after  it  has  ruptured  and  given  exit 
to   its   contents,  goes  on  forming  a  succession  of  new  generations   from,  its 

nucleus.     The  accompanying  figure  represents 
Fig.  41.  two  follicles  of  the  liver  of  the  common  Crab, 

which  are  seen  to  be  filled  with  secreting  cells  ; 
and  it  is  evident,  from  a  comparison  of  the  sizes 
of  the  cells  at  different  parts,  that  they  originate 
at  the  blind  extremity  of  the  follicle,  where  there 
is  a  germinal  spot ;  and  that,  as  they  recede 
from  that  point  and  approach  the  outlet  of  the 
TWO  follicles  from  the  liver  of  Car-     follicle,  they  gradually  increase  in  size  and  be- 
dnus  nuznas  (Common  Crab),  with     come  filled  with  their  characteristic  secretion ;  be- 
their  contained  secreting  cells.  ing  at  the  same  time  pushed  onwards  towards 


SECRETING  CELLS. SEROUS  AND  SYNOVIAL  MEMBRANES.  147 

the  outlet,  by  the  continual  new  growth  of  cells  at  the  germinal  spot.* — It  is 
by  the  continual  growth  and  exuviation  of  the  cells  which  line  the  glandular 
follicles,  that  the  various  products  of  Secretion  are  separated  from  the  blood ; 
and  it  is  in  cells  occupying  a  similar  position,  that  the  Spermatozoa  or  Repro- 
ductive particles  are  developed  (Plate  I.,  Fig.  18).  In  each  case,  the  growth 
of  the  cell,  and  the  nature  of  its  product,  depend  upon  its  own  peculiar 
vital  properties;  and  it  is  a  curious  fact  that'the  seminal  cells,  in  which  the 
-Spermatozoa  are  formed,  are  ejected  from  the  gland  in  the  Decapod  Crusta- 
ceous  animals,  not  only  before  they  have  burst  and  set  free  the  Spermatozoa, 
but  even  long  before  the  development  of  the  Spermatozoa  in  their  interior  is 
completed, — the  process  being  perfected,  after  the  cells  have  been  deposited 
in  the  generative  passages  of  the  female.t 

7.  Of  the  Compound  Membrano- Fibrous  Tissues. 

175.  Having  now  considered  the  Elementary  components  of  the  Tissues 
of  the  Human  body, — namely,  Membranes,  Fibres,  and  Cells, — we  proceed 
to  notice  certain  structures,  in  which  these  elements  are  united  in   their  sim- 
plest form ;  and,  in  the  first  place,  those  termed  Serous  and  Synovial  Mem- 
branes.    When  examined  with  the  Microscope,  their  free  surface  is  found  to 
be  covered  with  a  single  layer  of  Pavement-Epithelium,  which  lies  on  a  con- 
tinuous sheet  of  Basement-Membrane.     Beneath  this  last  is  a  layer  of  con- 
densed Areolar  tissue,  which  constitutes  the  chief  thickness  of  the  membrane, 
confers  upon  it  its  strength   and  elasticity ;  this  gradually  passes   into   that 
laxer  variety,  by  which   the  membrane  is   attached  to  the   parts  it  lines,  and 
which   is   commonly  known  as  the   subserous   tissue.     The   yellow  fibrous 
element  enters   largely  into  the  composition  of  the  membrane  itself;  and  its 
filaments  interlace  into  a  beautiful  network,  which  confers  upon  it  equal  elas- 
ticity in  every  direction.     The  membrane  is  traversed  by  blood-vessels,  nerves, 
and  lymphatics,  in  varying  proportions.     The  Serous  and   Synovial  mem- 
branes form,  as  is  well  known,  closed  sacs,  which  contain  a  greater  or  less 
proportion  of  fluid.     The  liquid  effused  from  the  Serous  membranes  is  nearly 
the  same  with  the  Serum  of  the  blood;  containing  as  much  as  7  or  8  per  cent. 

.  of  albumen  and  salts ;  and  being  distinctly  alkaline,  from  the  presence  of 
carbonate  or  albuminate  of  soda.  There  is  no  reason  for  regarding  it  in  any 
other  light,  than  as  a  simple  product  of  transudation.  The  fluid  contained 
in  the  Synovial  capsules,  and  in  the  Bursae  Mucosae,  may  be  considered  as 
serum  with  from  6  to  10  per  cent,  of  additional  albumen;  it  shows  an  alka- 
line reaction.^  The  fluid  of  Dropsy  (at  least  in  some  forms  of  this  disease) 
contains  in  addition  urea,  and  cholesterine  suspended  in  fine  plates;  also 
(according  to  Dr.  Kane)  stearine  and  elaine. 

176.  The  general  term  Mucous  Membrane  may  be  applied  to  that  great 
system  of  membranous   expansions,  which  forms  the  external  tegument,  or 
Skin, — the  lining  of  the  internal  cavities  whose  walls  are  continuous  with  it, 
or  Mucous  Membrane  proper,— and  the  prolongations  of  this  into  the  secre- 
ting organs,  forming  the  tubes  and  follicles  of  the  Glands.     These  all  consist, 
as  Mr.   Bowman  has  justly  remarked,§  "of  certain   elements,    which    the 
Anatomist  may  detect  and  discriminate;  some  of  them  being  essential,  others 
appended  or  superadded :  and   the  broad  characteristic  distinctions  between 

*  Goodsir,  in  Anatomical  and  Pathological  Observations,  Chap.  v. 

t  Op.  Cit.  p.  39. 

J  This  is  probably  a  true  secretion,  formed  by  the  agency  of  the  epithelium-cells  that  cover 
certain  delicate  highly-vascular  fringe-like  projections,  which  hang  down  into  the  sy  no  vial 
capsules. 

§  Cyclopedia  of  Anatomy  and  Physiology,  vol.  iii.  p.  485. 


148 


ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 


these  structures,  appreciable  to  ordinary  sense — as  well  as  the  innumerable 
gradations  by  which  they  everywhere  blend  insensibly  with  one  another, — 
are  solely  due  to  various  degrees  and  kinds  of  modification  wrought  in  the 
form,  quantity,  and  properties  of  these  respective  elementary  parts." — The 
Mucous  Membrane  may  be  said,  like  the  Serous,  to  consist  of  three  chief 
parts, — the  epithelium  or  epidermis  covering  its  free  surface, — the  subjacent 
basement-membrane, — and  the  areolar  tissue,  with  its  vessels,  nerves,  &c., 
which  forms  the  thickness  of  the  membrane,  and  connects  it  to  the  adjacent 
parts.  Of  the  Epithelium  and  Epidermis,  a  general  description  has  been 
given  in  the  preceding  Section.  The  Basement-Membrane  may  be  fre- 
quently demonstrated  with  very  little  trouble,  in  the  tubuli  of  the  glands, 
especially  the  kidney ;  which  are  but  very  slightly  adherent,  by  their  exter- 
nal surface,  to  the  surrounding  tissue.  Its  existence  on  the  Skin,  and  on 
many  parts  of  the  proper  Mucous  Membrane,  has  not  yet  been  fully  proved ; 
but  there  can  be  no  reasonable  doubt  of  its  continuity  in  these  situations. — 
These  two  elements  may  be  regarded  as  the  essential  constituents  of  Mucous 
membrane ;  which  is  thus  found  to  be,  strictly  speaking,  extra-vascular.  Its 
difference  from  Serous  Membrane  must  be  considered,  therefore,  as  depend- 
ing rather  upon  its  arrangement,  and  upon  the  peculiar  secretion  of  its  epithe- 
lium-cells, than  upon  any  decided  anatomical  character. 

177'.  The  tissues   appended   to  these  elements,  and  less  essential  to  the 
character  of  Mucous    Membrane,  are  Capillary  Blood-vessels,  Absorbents, 


Distribution  of  Capillaries  at  the  sur- 
face of  the  skin  of  the  ringer. 


Distribution  of  Capillaries  in  the 
Villi  of  the  Intestine. 


Fig.  44. 


Nerves,  and  Areolar  tissue.  The  former  are  almost  everywhere  abundant ; 
in  the  Skin  they  seem  chiefly  destined  to  supply  the  nervous  papillae,  and 
thus  minister  to  its  acute  sensibility  ;  whilst  in  the  Mucous  Membrane 
of  the  Alimentary  canal,  they  seem  more  concerned  in  the  functions  of  Ab- 
sorption and  Secretion  ;  and  in  the  Glandular  organs,  they  supply  the  mate- 
rials for  the  last-named  process.  The  Absorb- 
ents are  most  abundant,  as  Lymphatics,  in  the 
Skin ;  and  as  Lacteals,  in  the  Mucous  Mem- 
brane of  the  first  part  of  the  Intestinal  canal ; 
but  the  Lymphatics  are  also  largely  distributed 
through  some  of  the  Glandular  organs.  The 
Skin  is  the  only  part  of  this  system,  which  is 
largely  supplied  with  Nerves ;  except  the  Con- 
junctival  Membrane,  and  the  Mucous  Mem- 
brane of  the  ]Vose  :  hence  the  sensibility  of  this 
structure  is  usually  low,  although  its  import- 
ance in  the  organic  functions  is  so  great.  The 
Areolar  tissue  of  Mucous  Membranes  usually 
makes- up  the  greatest  part  of  their  thickness  ;  and  is  so  distinct  from  the  sub- 
jacent layers,  as  to  be  readily  separable  from  them.  It  differs  not,  however, 


Distribution  of  Capillaries  around 
follicles  of  Mucous  Membrane. 


STRUCTURE  AND  OFFICES  OF  MUCOUS  MEMBRANE. 


149 


in  any  important  particular,  from  the  same  tissue  elsewhere;  and  the  white 
and  the  yellow  fibrous  elements  may  be  detected  in  it,  in  varying  propor- 
tions, in  different  parts, — the  latter  being  especially  abundant  in  the  Skin  and 
the  Lungs,  which  owe  to  it  their  peculiar  elasticity.  Hence  the  Mucous 
Membranes  for  the  most  part  yield  Gelatine,  on  being  boiled.  There  is  some 
reason  to  believe,  that  the  Skin  also  contains  non-striated  muscular  fibres 
scattered  through  it. — .The  regeneration  of  all  the  forms  of  Mucous  Mem- 
brane, after  loss  of  substance  by  disease  or  injury,  is  very  complete,  and  takes 
place  with  considerable  rapidity. 

178.  The  essential  character  of  the  Mucous  Membranes,  in  regard  alike  to 
their  offices  and  their  arrangement,  is  altogether  different  from  that  of  the 
Serous  and  Synovial  membranes.  For,  whilst  the  latter  form  shut  sacs, 
whose  contents  are  destined  to  undergo  little  change,  the  former  either  cover 
the  external  surface  of  the  body,  or  line  tubes  and  cavities  in  its  interior, 
which  have  free  outward  communications;  and  they  thus  constitute  the  me- 
dium, through  which  all  the  changes  are  effected,  that  take  place  between  the 
living  organism  and  the  external  world.  Thus,  in  the  gastro-intestinal  mucous 
membrane,  we  find  a  provision  for  reducing  the  food,  by  means  of  a  solvent, 
fluid  poured  out  from  its  follicles ;  whilst  the  villi,  or  root-like  filaments, 
which  are  closely  set  upon  the  surface  of  that  same  membrane,  are  specially 
adapted  to  absorb  the  nutrient  materials  thus  reduced  to  the  liquid  state.  This 
same  membrane,  at  its  lower  part,  constitutes  an  outlet  through  which  are  cast 
out,  not  merely  the  indigestible  residuum  of  the  food,  but  also  the  excretions 
from  numerous  minute  glandulse  in  the  intestinal  wall,  which  result  from  the 

Fig.  45. 


Diagram  of  the  structure  of  an  involuted  Mucous  Membrane,  showing  the  continuation  of  its  elements 
in  the  follicles  and  villi ;  F,  F,  two  follicles ;  b.  basement  membrane  ;  c,  submucous  tissue ;  e,  epithelium ; 
r,  vascular  layer ;  n,  nerve ;  v,  villus,  covered  with  epithelium;  v',  villus  whose  epithelium  has  been  shed. 

decomposition  of  the  tissues,  and  which  must  be  separated  and  cast  forth  from 
them  to  prevent  further  decay.  Again,  the  bronchio-pulmonary  mucous  mem- 
brane serves  for  the  introduction  of  oxygen  from  the  air,  and  for  the  exhala- 
tion of  water  and  carbonic  acid.  The  mucous  membranes  prolonged  into  the 

13* 


150  ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 

interior  of  the  various  glands,  are  the  instruments  by  which  their  respective 
products  are  eliminated  from  the  blood.  And  lastly,  the  Skin  is  concerned 
in-  two  great  classes  of  changes;  the  excretion  of  various  matters  from  its 
surface,  and  from  the  glandulae  in  its  substance;  and  the  reception  of  impres- 
sions upon  the  nerves,  with  which  it  is  so  copiously  supplied. 

179.  The  character  of  the  secretions  formed  by  the  Mucous  Membranes, 
is  different  in  almost  every  part;  and  is  dependent,  as  will  be  shown  here- 
after, upon  the  properties  of  the  Epithelium-cells  which  cover  them.     These 
cells,  instead  of  forming  a  comparatively  permanent  stratum,  like  that  which 
covers  the  surface  of  serous  membranes,  are  in  a  state  of  continual  change 
and  renewal;  the  older  layers  falling  off,  whilst  new  ones  are  produced  in 
immediate  contact  with  the  subjacent  membrane, — and  this,  not  merely  on  its 
simple  plane  surfaces,  but  on  its  prolongations,  whether  these  form  the  cover- 
ings of  villi,  or  the  lining  of  follicles.     The  purpose  of  the  cells  which  form 
the  Epidermis,  is  simply  to  protect  the  sensitive  surface  of  the  true  skin;  and 
these  cells  have  the  power  of  drawing  a  horny  matter  into  their  interior.     On 
the  other  hand,  the  Epithelium  cells  of  the  ultimate  tubuli  or  vesicles  of  glands, 
contain  the  substances  which  characterize  the  secretions  of  those  glands.     It 
is  chiefly  on  the  bronchio-pulmonary  and  gastro-intestinal  mucous  membranes, 
that  we  meet  with  the  peculiar  secretion  termed  Mucus;  which  appears  to  be 
expressly  formed  to  shield  them  from  the  irritation  they  would  suffer  through 
the  contact  of  air,  or  of  solids  or  liquids.     This  secretion  is  also  found  on 
the  lining  membrane  of  the  larger  excretory  ducts  of  most  of  the  glands ;  and 
it  is  mixed,  in  greater  or  less  amount,  with  most  of  the  secretions  discharged 
by  them.     It  is  found  also  upon  the  lining  membrane  of  the  gall-bladder, 
and  of  the  urinary  bladder.     When  these  membranes  are  in  a  state  of  unusual 
irritation,  the  amount  of  mucus  which  they  discharge  is  very  considerable; 
but  it  ordinarily  forms  an  extremely  thin  layer.     The  characters  of  Mucus, 
obtained  from  various  sources,  are  by  no  means  invariable.     In  general,  how- 
ever, it  may  be  described  as  a  fluid  pf  peculiar  viscidity,  either  colourless  or 
slightly  yellow,  transparent  or  nearly  so,  incapable  of  mixing  with  water,  and 
sinking  in   it,  except  when  buoyed  up  by  bubbles  entangled  in  its    mass, 
which  is  commonly  the  case  with  the  bronchial  and   nasal  mucus.     This 
fluid  contains  from  4£  to  65  per  cent,  of  solid  matter,  of  which  a  small  part 
consists  of  salts  resembling  those  of  the  blood :  whilst  the  chief  organic  con- 
stituent is  a  substance  termed  Mucin,  to  which  the  characteristic  properties  of 
the  secretion  are  due.     This  appears  to  be  an  albuminous  compound,  altered 
by  the  action  of  an  alkali ;  for  as  Dr.  Babington  has  shown,  any  albuminous 
fluid  may  be  made  to  present  the  peculiar  viscidity  of  mucus,  by  treating  it 
with  liquor  potassae.    '  That  the  mucin  of  Mucus  is  held  in  solution  by  an 
alkali,  appears  from  this,  that  it  is  readily  precipitated  by  acids,  which  neu- 
tralize the  base ;  and  that  a  sort  of  faint  coagulation  may  be  induced  even  by 
water,  which  withdraws  the  base  from  it.     When  Mucus  is  examined  with 
the  Microscope,  it  is  found  to  contain  numerous  epithelium-scales  (or  flattened 
cells) ;    together  with   round   granular  corpuscles,  considerably  larger   than 
those  of  the  blood,  and  closely  resembling  the  nuclei  of  the  epithelium-cells, 
which  are  commonly  termed  mucus-corpuscles.     In  the  more  opaque  mucus, 
discharged  from  membranes  in -a  state  of  irritation  or  inflammation,  these  cor- 
puscles are  present  in  greatly-increased  amount ;  and  cells  are  often  developed 
around  them. 

8.   Of  Simple  Isolated  Cells,  forming  Solid  Tissues  by  their  Aggregation. 

180.  We  now  proceed  to  a  class  of  Cells,  which  are  equally  independent 
of  each  other,  which  begin  and  end  their  lives  as  cells  without  undergoing  any 


PERSISTENT  CELLULAR  PARENCHYMA. PLACENTAL  CELLS.  151 

transformation,  but  which  form  part  of  the  substance  of  tire  fabric,  instead  of 
lying  upon  its  free  surfaces  and  being  continually  cast  off  from  them.  Still 
their  individual  history  is  much  the  same  as  that  of  the  cells  already  noticed  ; 
and  they  differ  chiefly  in  regard  to  the  destination  of  their  products^  There 
are  many  animals,  in  which  such  aggregations  of  cells  make  up  a  much  larger 
part  of  the  fabric,  than  they  do  in  Man ;  and  this  in  consequence  of  their  re- 
taining more  of  the  embryonic  type  of  structure  in  their  adult  condition. 
Thus  in  the  Myxinoid  family  of  Fishes,  there  is  no  true  Vertebral  column ; 
but  its  place  is  supplied  by  a  gelatinous  tube,  termed  the  chorda  dorsalis  ; 
which  consists  of  nucleated  cellular  tissue,  and  which  is  precisely  analogous 
to  the  structure  occupying  the  same  position  in  the  early  embryo  of  higher 
animals.  In  the  Short  Sunfish,  a  corresponding  form  of  tissue  forms  a  thick 
covering  to  the  body,  replacing  the  true  skin.  And  in  the  Lancelot  (a  little 
Fish  which  is  deficient  in  so  many  of  the  characters  of  the  Vertebrated  di- 
vision, that  many  naturalists  have  doubted  its  right  to  a  place  in  the  class),  a 
considerable  portion  of  the  fabric  is  made  up  of  a  like  cellular  parenchyma. 

181.  The  first  group  of  this  class  deserving  a  separate  notice,  is  that  which 
effects  the  introduction  of  aliment  into  the  body ; — of  those  kinds  of  aliment, 
at  least,  which  are  not  received  in  solution  by  any  more  direct  means.  These 
cells  (first  pointed  out  by  Mr.  J.  Goodsir)  form  a  cluster  at  the  extremity  of 
each  of  the  villi  of  the  intestinal  tube ;  the  origin  of  the  lacteal  being  lost  in 
the  midst  of  it.  If  examined  whilst  the  absorbent  process  is  going  on,  they 
are  found  to  be  turgid  with  a  milky  fluid,  which  is  evidently  the  same  with 
that  of  the  lacteals  ;  and  to  have  a  diameter  of  from  1 -2000th  to  1-1 000th  of 
an  inch  (Fig.  46,  A).  In  the  intervals  of  the  digestive  process,  the  extremities 
of  the  villi  are  comparatively  flaccid :  and  instead  of  cells,  they  show  merely 

• 

•      Fig.  46. 


Extremity  of  intestinal  villus;  seen  at  A,  during  absorption,  and  showing  absorbent  cells  and  lacteal 
trunks,  distended  with  chyle  ;  at  B,  during  interval  of  digestion,  showing  peripheral  network  of  lacteals, 
with  granular  germs  of  absorbent  cells,  as  yet  undeveloped,  lying  between  them. 

a  collection  of  granular  germs  (Fig.  46,  b).  These  begin  to  develope  them- 
selves, as  soon  as  the  food  has  been  dissolved  in  the  stomach  and  transmitted 
to  the  intestine  ;  and  their  development  goes  on  so  long  as  they  are  surrounded 
with  nutrient  matter.  The  cells  grow,  select,  absorb,  and  prepare  the  nu- 
tritious matter,  by  making  it  a  part  of  themselves  ;  and,  when  their  work  is 
accomplished,  they  deliver  it  to  the  lacteals  by  their  own  rupture  or  deliques- 
cence,— at  the  same  time,  it  is  probable,  setting  free  the  germs,  from  which  a 
new  generation  maybe  developed,  when  the  next  supply  of  chyle  is  prepared. 
182.  Although  the  mucous  membrane-  of  the  intestinal  tube  is  the  only 
channel,  through  which  insoluble  nutriment  can  be  absorbed  in  the  completely- 
formed  Mammal,  and  the  only  situation,  therefore,  in  which  we  meet  with 
these  absorbent  cells,  there  are  other  situations,  in  which  similar  cells  perform 
analogous  duties  in  the  embryo.  Thus,  the  Chick  derives  it  nutriment,  whilst 
in  the  egg,  from  the  substance  of  the  yolk,  by  absorption  through  the  blood- 
vessels, spread  out  in  the  vascular  layer  of  the  germinal  membrane  that  sur- 
rounds it ;  which  vessels  answer  to  the  blood-vessels  and  lacteals  of  the  per- 


152 


ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 


manent  digestive  •  cavity,  and  are  raised  into  folds  or  villi,  as  the  contents  of 
the  yolk-bag  are  diminished.  Now  the  ends  of  the  vessels  •  are  separated 
from  the  fluid  contents  of  the  yolk-bag  by  a  layer  of  cells,  which  is  filled 
with  matter  of  a  yellow-colour;  and  which  seems  to  have  for  its  office,  to 
select  and  prepare  the  materials  supplied  by  the  yolk,  for  being  received  into 
the  absorbent  vessels.  In  like  manner,  me  embryo  of  the  Mammal  is  nou- 
rished, up  to  the  time  of  its  birth,  through  the  medium  of  its  umbilical  ves- 
sels ;  the  ramifications  of  which  form  tufts,  that  dip  down  (as  it  were)  into 
the  maternal  blood,  and  receive  from  it  the  materials  destined  for  the  nutrition 
of  the  foetus ;  besides  effecting  the  aeration  of  the  blood  of  the  latter,  by 
exposing  it  to  the  more  oxygenated  blood  of  its  mother.  Now  around  the 
capillary  loop  of  the  fetal  tuft  there  is  a  layer  of  cells,  closely  resembling  the 
absorbent  cells  of  the  villi ;  and  these  are  inclosed  in  a  cap  of  basement-mem- 
brane, which  completes  the  fetal  portion  of  the  tuft,  and  renders  it  comparable, 
in  all  essential  respects,  to  the  intestinal  villus.  It  is  again  surrounded,  however, 
by  another  layer  of  membrane  and  of  cells,  belonging  to  the  maternal  sys- 
tem;  the  derivation  of  which  will  be  explained  hereafter  (Chap.  XVII). 

183.  The  cells  which  make  up  the  parenchyma  of  the  Liver  in  the  higher 
animals,  seem   to   be   developed  under  conditions  somewhat  similar.     In  the 
Invertebrata,  the  Liver  is  constructed  upon  the  type  of  the  glands  in  general ; 
its  secreting  cells  being  developed  as  an  epithelium  upon  the  inner  wall  of  the 
hepatic  ducts.     This  does  not  appear  to  be  the  case,  however,  in  Man  and  the 
Mammalia  :  the  substance  of  whose  liver  is  made  up  of  an  aggregation  of 
cells,  which  lie — so  far  as  can   be  ascertained — upon  the 
Fig.  47.  outside  of  the  terminal  ramifications  of  the  hepatic  ducts. 

That  these  cells  are  the  efficient  instruments  in  the  secre- 
ting process,  is  evident  from  the  nature  of  their  contents, 
which  consist  of  biliary  matter  with  oil  globules.  Their 
diameter  is  usually  from  1-1 500th  to  l-200th  of  an  inch  ; 
and  they  generally  contain  a  very  distinct  nucleus.  Their 
connexion  with  the  secreting  process  is  further  marked  by 
the  fact,  that,  in  some  instances  in  which  the  bile  has  not 
been  eliminated,  and  death  has  been  the  result,  Microscopic 
examination  has  proved  that  the  hepatic  cells  were  either 
very  imperfectly  formed  or  were  almost  entirely  deficient. 
Further,  in  cases  of  Fatty  Liver,  the  cells  have  been  found  to  contain  an  un- 
usual amount  of  Adipose  matter. 

184.  The  Fat-cells,  of  which  Adipose  tissue 
is  composed,  also  permanently  exhibit  the  original 
type  of  structure  in  .its  simplest  form.  This  tis- 
sue is  usually  difFuse'd  over  the  whole  body,  filling 
up  interstices,  and  forming  a  kind  of  pad  or 
cushion  for  the  support  of  moveable  parts.  Even 
in  cases  of  great  emaciation,  some  Fat  is  always 
left ;  especially  at  the  base  of  the  heart,  around 
the  origin  of  the  large  vessels ;  in  the  orbit  of  the 
eye  ;  in  the  neighbourhood  of  the  kidney  ;  in  the 
interior  of  the  bones  ;  and  within  the  spinal  ca- 
nal, between  the  periosteum  and  the  dura  mater. 
The  Fat  Cells  are  usually  spherical  or  spheroidal ; 
sometimes,  however,  when  closely  pressed  toge- 
ther without  the  intervention  of  any  intercellular 
substance,  they  become  polyhedral.  The  nucleus 
is  not  always  to  be  distinguished ; — perhaps  in 
consequence  of  its  having  passed  to  the  interior  of 


Secreting  Cells  of 
Human  Liver ;  o,  nu- 
cleus; 6,  nucleus  ;  c, 
oil-particles. 


[Fig.  48. 


Fat  vesicles,  assuming  the  poly- 
hedral form  from  pressure  against 
one  another.  The  capillary  ves- 
sels are  not  represented.— From 
the  omentum  ;  magnified  about  300 
diameters.] 


FAT  CELLS  ;    COMPOSITION  AND  USES  OF  FAT. 


153 


the  cell ;  it  has  been  seen,  however,  in  the  fat-cells  of  the  embryo.     The  dia- 
meter of  the  greater  number  of  fat-cells,  is   between  l-300th  and  l-600th  of 
an  inch  ;  but  larger  and  smaller  sizes  are  frequently  to  be  met  with.     These 
» bodies  frequently  present  themselves  in  an  isolated  condition,  dispersed  among 
the  meshes  of  Areolar  tissue ;  but  when   they  are   aggregated  so  as  to  form 
masses  of  fat,  they  are  first  collected  into  little  lobular  clusters,  each  of  which 
has    a    delicate    membranous    invest- 
ment ;  and  these  are  again  united  into  Fig.  49. 
larger  clusters,  visible  to  the  naked 
eye.     The  aggregation  of  these  often 
forms  masses   of  considerable    size ; 
the  component  parts  being  held  toge- 
ther by  Areolar  tissue,  and  also  by  the 
blood-vessels  which   penetrate   them, 
and  which   ramify   minutely   among 
them,   forming  a    capillary  network, 
not   only  upon   the    surface    of    the 
smallest  lobules,  but  even   (it  would 
appear)  between  their  contained  fat- 
cells.     In  some  forms  of  Adipose  tis- 
sue, such  as  the  marrow  of  bones,  it 

would  seem  that  very  little  areolar  tissue  exists,  or  that  it  is  even  entirely 
absent ;  and  here  the  capillary  plexus  forms  the  principal  bond  of  union  be- 
tween the  fat-cells.  No  lymphatics  have  been  detected  in  Adipose  tissue  ; 
and  it  would  seem  to  be  equally  destitute  of  nerves,  excepting  such  as  are 
passing  through  it  on  their  way  to  other  textures  ; — thus  accounting  for  the 
known  fact  of  its  being  insensible,  except  when  those  trunks  are  injured. 

'  [Fig.  50. 


Cells  of  Adipose  Tissue  ;  magnified  135  diameters. 


Blood-vessels  of  Fat;  1,  minute  flattened  fat-lobule,  in  which  the  vessels  only  are  represented  ;  3,  the 
terminal  artery  ;  4,  the  primitive  vein  ;  5,  the  fat  vesicles  of  one  border  of  the  lobule,  separately  repre- 
sented,—magnified  100  diameters;  2,  planof  the  arrangement  of  the  capillaries  on  the  exterior  of  the 
vesicles, — more  highly  magnified.] 

185.  The  consistency  of  the  substance  contained  in  the  Fat-vesicles,  varies 
in  different  animals,  according  to  the  proportions  of  the  organic  elements,  that 
"enter  into  its  composition.  These  elements  are  known  under  the  names  of 
Stearine,  Margarine,  and  Oleine:  the  two  former,  which  are  solid  when  sepa- 


154 


ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 


[Fig.  51. 


Fat  vesicles  from  an  emacia- 
*ed  subject;  1,  1,  the  cell-mem- 
brane; 2,2,2,  the  solid  portion 
collected  as  a  star-like  mass> 
with  the  elaine  in  connection 
with  it,  but  not  filling  the  cell.] 


rate,  being  dissolved  in  the  latter,  at  the  ordinary 
temperature  of  the  body.  That  the  thick  oil  thus 
formed  does  not  escape  from  the  fat-cells  during 
life,  may  be  attributed  to  the  moistening  of  their 
walls  by  the  aqueous  fluid  circulating  through  the 
vessels.  In  all  fixed  oils,  which  are  fluid  at  com- 
mon temperatures,  a  portion  of  the  solid  constitu- 
ents of  fat  exists  ;  these  may  be  separated  by  ex- 
posure to  cold,  which  congeals  them,  leaving  the 
Oleine  fluid.  All  these  substances  are  regarded 
by  chemists  in  the  light  of  salts  ;  being  compounds 
of  acids — the  Stearic,  Margaric,  and  Oleic — with 
a  common  base,  to  which,  from  its  sweetish  taste, 
the  name  of  Glycerine  has  been  given. 

a.  Stearine  is  the  essential  constituent  of  nearly  all  solid  fats,  and  preponderates  in  propor- 
tion to  their  consistence.  It  exists  largely  in  mutton-suet ;  from  this  it  may  be  obtained  by 
the  action  of  ether,  which  takes  up  all  the  oily  matter.  It  is  crystalline,  like  spermaceti ; 
it  is  not  at  all  greasy  between  the  fingers,  and  melts  at  about  130°.  It  is  insoluble  in  water, 
and  in  cold  alcohol  and  ether;  but  it  dissolves  in  boiling  alcohol  or  ether,  crystallizing  as  it 
cools.  Stearic  acid  (the  substance  of  which  the  stearine  candles  are  composed)  may  be  sepa- 
rated, by  causing  it  to  combine  with  a  stronger  base,  such  as  lime  or  potash,  and  then  setting 
it  free  from  this  by  a  stronger  acid.  It  crystallizes  in  milk-white  needles ;  is  soluble  in  its 
own  weight  of  cold  alcohol,  and  in  all  proportions  at  a  boiling  heat;  and  fuses  at  about  158°. 
Its  acid  powers  are  sufficient  to  decompose  the  alkaline  carbonates. — Margarine  exists  in 
small  quantity,  along  with  Stearine,  with  most  fats ;  but  it  is  the  principal  solid  constituent 
of  Human  fat,  which  in  this  respect  resembles  olive  oil  rather  than  the  other  animal  fats.  It 
corresponds  with  Stearine  in  many  of  its  properties  ;  but  it  is  much  more  soluble  in  alcohol 
and  ether;  and  it  melts  at  116°.  Margaric  acid  closely  resembles  stearic  acid  in  most  of  its 
properties;  but  it  is  more  soluble  in  cold  alcohol;  and  has  a  lower  melting-point,  viz.,  140°, 
or  thereabouts.  It  may  be-  procured  from  stearic  acid,  by  subjecting  the  latter  to  a  dry  dis- 
tillation.— Oleine  exists  in  small  quantity  in  the  various  solid  fats ;  but  it  constitutes  the  great 
mass  of  the  liquid  fixed  oils.  The  tendency  of  these  to  solidification  by  cold,  depends  upon 
the  proportion  of  stearine  or  margarine  they  may  contain  ;  for  oleine  itself  remains  fluid 
at  the  zero  of  Fahrenheit's  thermometer.  It  is  soluble  in  cold  ether,  from  which  it  can  only 
be  separated  by  the  evaporation  of  the  latter.  Oleic  acid  much  resembles  oleine  in  physical 
characters,  being  colourless,  lighter  than  water,  and  not  prone  to  solidify  j  but  it  has  a  dis- 
tinct acid  reaction,  and  a  sharp  taste,  and  is  miscible  with  cold  alcohol  in  all  proportions.— 
Glycerine,  the  base  of  all  the  fatty  acids,  may  be  obtained  from  any  fatty  matter,  by  saponi- 
fying it  with  an  alkaline  base,  by  which  this  compound  is  set  free.  It  cannot  be  obtained 
in  a  solid  form,  but  maybe  brought  to  the  consistence  of  a  thick  syrup.  It  dissolves  in 
water  and  alcohol ;  but  is  insoluble  in  ether.  It  has  a  sweetish  taste,  whence  its  name  is 
derived ;  and  it  is  remarkable  for  its  solvent  powers,  which  are  scarcely  inferior  to  those  of 
water. — The  following  table  shows  the 'atomic  composition. of  the  fatty  acids,  and  of  their 
base. 

Stearic  Acid  ...     .68  Carbon,  66  Hydrogen,  5  Oxygen. 

Margaric  Acid    ...     68  Carbon,  66  Hydrogen,  6  Oxygen. 

Oleic  Acid      .     .     .     .     44  Carbon,  39  Hydrogen,  4  Oxygen. 

Glycerine 6  Carbon,    8  Hydrogen,  6  Oxygen. 

The  following  results  of  the  ultimate  analysis  of  different  kind  of  Fat,  show  the  close 
correspondence  in  their  composition ;  and  at  the  same  time  make  apparent  the  very  large 
proportion  of  carbon  which  they  all  contain. 


Carbon  .  . 
Hydrogen  . 
Oxygen 


Hog's  Lard. 
.     79-098 
.     11-146 
9-756 

100-000 


Mutton  Fat. 

78-996 

11-700 

9-304 

100-000 


Human  Fat. 

79-000 

11-416 

9-584 

100-000 


186.  Besides  the  support,  combined  with  facility,  of  movement,  which  Fat 
affords  to  the  moving  parts  of  the  body,  it  answers  the  important  purpose  of 
assisting  in  the  retention  of  the  animal  temperature,  by  its  non-conducting 
power;  and  the  still  more  important  object,  of  serving  as  a  kind  of  reservoir 
of  combustible  matter  against  the  time  of  need.  Herbivorous  animals,  whose 


STRUCTURE  AND  COMPOSITION  OF  CARTILAGE. 


155 


Fig.  52. 


food  is  scanty  during  the  winter,  usually  exhibit  a  strong  tendency  to  such  an 
accumulation,  during  the  latter  part  of  the  summer,  when  their  food  is  most 
rich  and  abundant ;  and  the  store  thus  laid  up  is  consumed  during  the  winter. 
This  is  particularly  evident  in  the  hybernating  Mammalia,  which  take  little  or 
no  food  during  their  seclusion.  Fat  appears  to  be  deposited,  only  where  there 
is  an  excess,  in  the  alimentary  matter  introduced  into  the  body,  of  non-azo- 
tized  compounds  which  may  be  converted  into  it.  But  the-ingestion  of  a  large 
quantity  of  these  in  the  food,  is  by  no  means  sufficient  for  the  production  of 
Fat ;  for  they  may  not  be  absorbed  into  the  vessels  ;  and,  if  absorbed,  there 
may  be  a  want  of  power  to  generate  Adipose  tissue, — so  that  they  would  ac- 
cumulate injuriously  in  the  blood,  if  not  drawn  off  by  the  Liver.  Hence 
some  persons  never  become  fat,  however  large  the  quantity  of  oily  matter 
ingested  ;  and  it  is  in  such  persons,  that  the  tendency  to  disorder  of  the  Liver 
from  over-work  is  most  readily  manifested  ;  hence  they  are  obliged  to  abstain 
from  the  use  of  fat-producing  articles  of  food. 

187.  In  Cartilage,  also,  the  simple  cellular  structure  is  very  obviously  re- 
tained, and  frequently  exists  alone  ;  although  in  some  forms  of  this  tissue,  it 
is  united  with  the  fibrous,  or  partly 
replaced  by  it.  In  all,  however,  the 
early  stage  of  formation  appears  to 
be  the  same.  The  structure  origi- 
nates in  cells,  analogous  to  those  of 
which  the  rest  of  the  fabric  is  com- 
posed ;  but  between  these  cells,  a 
larger  quantity  than  usual  of  hyaline 
or  intercellular  substance  is  depo- 
sited ;  and  the  amount  of  this  sub- 
stance continues  increasing,  simul- 
taneously with  the  bulk  of  the  cells. 
The  original  cells  are  pushed  far- 
ther and  farther  from  one  another  ; 
but  new  cells  arise  between  them 
from  germs  which  are  contained  in 
the  hyaline  substance.  The  first 
cells  frequently  produce  two  or  more 
young  cells  from  their  nuclei ;  and 
thus  it  is  very  common  to  meet  with 

groups  of  such  cells  or  corpuscles,  consisting  of  two,  three,  or  four. — The 
varieties  in  the  permanent  Cartilages  principally  depend  upon  the  degree  of 


c 

Section  of  the  Branchial  cartilage  of  Tadpole;  af 
group  of  four  cells,  separating  from  each  other;  6, 
pair  of  cells  in'  apposition  ;  c,  c,  nuclei  of  cartilage 
cells  ;  d,  cavity  containing  three  cells. 


organization,  which  subsequently 
takes  place  in  the  intercellular  sub- 
stance. If  a  mass  of  Fibres,  analo- 
gous to  those  of  the  fibrous  mem- 
branes (§  138),  should  originate  in 
it,  the  Cartilage  presents  a  more  or 
less  fibrous  aspect;  in  some  instan- 
ces the  Fibrous  structure  is  deve- 
loped so  much,  at  the  expense  of 
the  Cells,  that  the  latter  disappear 
altogether,  and  the  whole  structure 
becomes  fibrous.  Sometimes  the 
fibres  which  are  developed,  are 
rather  analogous  to  those  of  the 
Elastic  tissue  (§  140) ;  these  are  dis- 
posed around  the  cells,  forming  a 
kind  of  network,  in  the  areolae  of 


Fig.  53. 


Section  of  Fibro-Cartilage  ;  showing  disposition  of 
cartilage  cells,  in  areolae  of  fibrous  tissue. 


1.56  ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 

which  they  lie;  and  this  kind  of  cartilage  may  be  termed  the  elastic  or 
reticular.  The  primitive  cellular  organization  is  for  the  most  part  retained 
in  the  ordinary  articular  cartilages,*  the  cartilaginous  septum  narium,  the  car- 
tilages of  the  alas  and  point  of  the  nose,  the  semilunar  cartilage  of  the  eye- 
lids, the  cartilages  of  the  larynx  (with  the  exception  of  the  epiglottis),  the 
cartilage  of  the  trachea  and  its  branches,  the  cartilages  of  the  ribs  (in  Man) 
and  the  ensiform  cartilage  of  the  sternum  ;  and  it  is  seen  also  in  the  tempo- 
rary cartilages,  or  those  which  are  destined  to  undergo  ossification.  The 
fibrous  structure  is  seen  in  all  those  Cartilages,  which  unite  the  bones  by 
synchondrosis  ;  this  is  the  case  in  the  vertebral  column  and  pelvis,  the 
cartilages  of  which  are  destitute  of  corpuscles,  except  in  and  near  their  cen- 
tres. In  the  lower  Vertebrata,  however,  and  in  the  early  condition  of  the 
higher,  the  fibrous  structure  is  confined  to  the  exterior,  and  the  whole  interior 
is  occupied  by  the  ordinary  cartilaginous  corpuscles.  The  reticular  structure 
is  best  seen  in  the  epiglottis  and  in  the  concha  auris :  in  the  former  of-  these, 
scarcely  any  trace  of  cartilage-cells  remains  ;  in  the  latter,  the  fibrous  net- 
work disappears  by  degrees  towards  the  extremity  of  the  concha,  and  the 
structure  gradually  passes  into  the  cellular  form.t 

a.  The  substance  that  gives  to  the  Cellular  Cartilages  their  peculiar  character,  has  received 
the  designation  of  Chondrine.  It  bears  much  resemblance  to  ordinary  Gelatine,  but  requires 
longer  boiling  in  water  for  its  solution ;  the  solution  fixes  on  cooling,  like  that  of  gelatine ; 
and  when  it  becomes  dry  by  evaporation,  it  has  the  appearance  of  solid  glue.  Chondrine 
is  not  precipitated,  however,  by  tannic  acid;  on  the  other  hand,  it  gives  precipitates  with 
acetic  acid,  alum,  acetate  of  lead,  and  proto-sulphate  of  iron,  which  do  not  disturb  a  solution 
of  Gelatine.  That  the  Chondrine  obtained  by  boiling  Cartilage  is  an  actual  component  of 
that  tissue,  and  is  not  a  product  of  the  operation,  appears  from  the  agreement  between  its 
elementary  composition  and  that  of  cartilage,  when  analyzed  by  combustion.  According  to 
Mulder,  the  proportions  of  the  elements,  as-  deduced  from  the  definite  compound  which 
Chondrine  forms  with  Chlorine,  are  32  C,  26  H,  4N,  14  0,  with  l-10th  of  an  equivalent  of 
Sulphur.  Chondrine  agrees  much  more  nearly  with  the  proteine-compounds,  in  its  element- 
ary composition,  than  does  Gelatine ;  and  may  be  considered  as  a  sort  of  intermediate  stage 
between  the  two.  Chondrine  is  not  obtainable  from  any  of  the  Fibro-cartilages ;  these 
yield  gelatine,  on  boiling,  exactly  similar  to  that  of  the  tendons.  The  Elastic  cartilages, 
after  being  boiled  for  several  days,  yield  a  small  quantity  of  an  extract,  which  does  not  form, 
a  jelly,  but  which  has  the  other  chemical  properties  of  Chondrine.  .The  cartilage  of  Bone, 
before  ossification,  yields  only  Chondrine  ;  after  ossification,  however,  it  affords  only  Gelatine; 
and  it  is  curious  that,  even  when  bony  deposits  take  place  in  the  permanent  cartilages,  the 
ossified  portion  contains  ordinary  Gelatine  in  the  place  of  Chondrine.  Many  of  the  carti- 
lages naturally  contain  a  large  proportion  of  mineral  matter ;  in  the  costal  cartilages,  frac- 
tures in  which  are  generally  repaired  by  osseous  substance,  from  3  to  7  per  cent,  of  ash  is 
left  by  calcination.  This  contains  a  large  proportion  of  the  carbonate  and  sulphate  of  soda, 
together  with  carbonate  of  lime  and  a  small  proportion  of  phosphate ;  as  age  advances,  the 
phosphate  of  lime  predominates,  and  the  soluble  compounds  diminish. 

188.  Cartilage  (at  least  in  its  simplest  form)  is  nourished,  without  coming 
into  direct  relation  with  the  Blood  through  the  medium  of  blood-vessels ;  the 
cellular  Cartilages  not  being  penetrated  by  vessels  in  the  healthy  state;  al- 
though in  certain  diseased  conditions  they  become  distinctly  vascular.  They 
are,  however,  surrounded  by  Blood-vessels ;  which  form  large  ampullae  or 
varicose  dilatations  at  their  edges  or  on  their  surfaces  (Fig.  54) :  and  from 
these  the  Cartilages  derive  their  nourishment  .by  imbibition ;  in  exactly  the 
same  manner  as  the  frond  of  a  Sea-weed  (the  structure  of  which  is  alike  cel- 
lular) draws  into  itself  the  requisite  fluid  from  the  surrounding  medium.  In 
the  thicker  masses  of  cartilaginous  tissue,  however,  such  as  the  cartilages  of 

*  The  articular  cartilages,  at  the  points  where  tendons  are  implanted  into  them,  have  all 
the  characters  of  fibro-cartilage ;  the  fibres  of  the  tendon  being  spread  through  the  intercel- 
lular substance  of  the  cartilage,  for  some  distance,  and  gradually  coalescing  with  it. 

•f  See  Mr.  Toynbee's  Memoir  on  the  Non- Vascular  Tissues,  Phil.  Trans.  1841. 


STRUCTURE  AND  COMPOSITION  OF  CARTILAGE. 


157 


the  ribs,  we  find  canals  excavated  at  wide  distances  from  each  other ;  which 
are  lined  by  a  continuation  of  the  perichondrium  or  investing  membrane  of 
the  cartilage,  and  which  thus  allow 

its  vessels  to  come  into  nearer  prox-  Fig.  54- 

imity  with  parts,  that  would  be  other- 
wise too  far  removed  from  them. 
The  vessels,  however,  nowhere  pass 
from  the  walls  of  these  canals  into 
the  substance  of  the  cartilage.  Si- 
milar vascular  canals  are  found  in  the 
temporary  cartilages,  near  the  points 
where  the  ossifying  process  is  taking 
place ;  this  is  well  seen  in  the  long 
bones,  towards  their  extremities.  At 
an  early  period  of  foetal  life,  there  is 
HO  distinction  between  the  cartilage  that  is  ultimately  to  become  the  Osseous 
Epiphysis,  and*that  which  is  to  remain  as  Articular  Cartilage ;  both  are  alike 
cellular  ;  and  the  vessels  that  supply  them  with  nutrient  materials  penetrate 
no  further  than  their  surfaces.  At  a  subsequent  period,  however,  when  the 
ossification  of  the  epiphysal  cartilage  is  about  to  commence,  vessels  are 
prolonged  into  it ;  and  a  distinct  line  of  demarcation  is  seen  betwixt  the  vas- 
cular portion,  which  is  to  be  converted  into  Bone,  and  the  non-vascular  part, 
which  is  to  remain  as  Cartilage.  At  this  period,  the  Articular  Cartilage  is 

Fig.  55. 


Vessels  between  the  Articular  Cartilage  and  attached 
Synovial  Membrane.    (After  Toynbee.) 


Vessels  situated  between  the  attached  synovial  membrane,  and  the  articular  cartilage,  at  the  point 
where  the  ligamentum  teres  is  inserted  in  the  head  of  the  os  femoris  of  the  human  subject,  between  the 
third  and  fourth  months  of  foetal  life  ;  a,  the  surface  of  the  articular  cartilage  ;  6,  the  vessels  between  the 
articular  cartilage  and  the  synovial  membrane ;  c,  the  surface  to  which  the  ligamentum  teres  was  at- 
tached ;  d,  the  vein  ;  «,  the  artery. 

nourished  by  a  plexus  of  vessels  spread  over  its  free  surface,  beneath  its  sy- 
novial membrane;  as  well  as  by  the  vessels,  with  which  it  comes  in  contact 
at  its  attached  extremity.  Towards  the  period  of  birth,  however,  the  sub-sy- 
novial  vessels  gradually  recede  from  the  surface  of  the  articular  cartilage  ;  and 
at  adult  age  they  have  entirely  left  it,  though  they  still  form  a  band  which 
surrounds  its  margin.  The  Fibrous  cartilages  are  somewhat  vascular ;  but 
the  vessels  do  not  extend  to  the  cellular  portions,  where  such  exist. 

189.  No  vessels  can  be  traced  (according  to  Mr.  Toynbee)  into  the  sub- 
stance of  the  true  Cornea ;  which,  contrary  to  the  statement  of  Miiller,  is  a 
cellular  rather  than  a  fibrous  cartilage.     The  cells  are  not  so  numerous  as  are 
those  of  the  articular  cartilages;  and  they  are  surrounded  by  a  plexus  of  bright 
14 


158 


ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 


Fig.  56.  fibres,  laxly  connected  together,  so  as  to  re- 

semble areolar  tissue.  Two  sets  of  vessels,  a 
superficial  and  a  deep-seated,  surround  the  mar- 
gin of  the  cornea.  The  arteries  of  the  former 
are  prolonged  for  a  short  distance  upon  the 
Conjunctival  membrane,  which  forms  the  outer 
lamina  of  the  cornea ;  but  they  terminate  in 
veins  at  from  a  to  £  a  line  from  its  margin. 
The  deep-seated  vessels  belong  to  the  Cornea 
proper ;  but  they  do  not  enter  it,  the  arteries 
terminating  in  veins  just  where  the  tissue  of 
the  Sclerotic  becomes  continuous  with  that  of 
the  Cornea.  In  diseased  conditions  of  the 
Cornea  (as  of  the  articular  cartilages),  both  sets 
of  vessels  extend  themselves  through  it ;  the 
superficial  not  unfrequently  form  a  dark  band 
of  considerable  breadth  round  its  margin ; 
whilst  the  deep-seated  are  prolonged  into  its 
entire  substance.  Notwithstanding  the  absence 
of  vessels  in  the  healthy  condition  of  this  struc- 
ture, incised  wounds  commonly  heal  very  rea- 
dily, as  is  well  seen  after  the  operation  of  ex- 
traction of  Cataract ;  but  the  foregoing  details 
make  evident  the  importance  of  not  carrying 

the  incision  further  round  than  is  necessary ;  since  the  corneal  tissue  should 
not  be  cut  off  from  the  supply  of  nourishment,  afforded  by  the  vessels  in  its 
immediate  proximity. 

[This  structure  has  been  recently  studied  by  Messrs.  Todd  and  Bowman,  and  is  described 
by  them  with  great  accuracy.  We  subjoin  their  description.  "  The  cornea,  though  a  beau- 
tifully transparent  substance,  and  appearing  at  first  sight  as  homogeneous  as  glass,  is  never- 
theless full  of  elaborate  structure.  It  is  in  fact  composed  of  five  coats  or  layers,  clearly 
distinguishable  from  one  another.  These  are,  from  before  backwards,  the  conjunctival  layer 
of  epithelium,  the  anterior  elastic  lamina,  the  cornea  proper,  the  posterior  elastic  lamina,  and  the 
epithelium  of  the  aqueous  humour,  or  posterior  epithelium.  The  cornea,  when  uninflamed,  con- 
tains no  blood-vessels;  those  of  the  surrounding  parts  running  back  in  loops,  as  they  arrive 
at  its  border. 

On  the  coj-nea  proper,  or  lamellated  cornea,  the  thickness  and  strength  of  the  cornea  mainly 
depend.  It  is  a  peculiar  modification  of  the  white  fibrous  tissue,  continuous  with  that  of  the 
sclerotic.  At  their  line  of  junction  (fig.  57),  the  fibres,  which  in  the  sclerotic  have  been 

Fig.  57. 


Nutrient  Vessels  of  the  cornea.  A, 
superficial  vessels  belonging  to  the 
Conjunctival  membrane,  and  continu- 
ed over  the  margin  of  the  Cornea ;  B, 
vessels  of  the  Sclerotic,  returning  at 
the  margin  of  the  Cornea. 


Vertical  section  of  the  Sclerotic  and  Cornea,  showing  the  continuity  of  their  tissue  between  the  dotted 
lines: — a.  Cornea,  b.  Sclerotic.  In  the  cornea  the  tubular  spaces  are  seen  cut  through,  and  in  the 
sclerotic  the  irregular  areolce.  Cell-nuclei,  as  at  c,  are  seen  scattered  throughout,  rendered  more  plain 
by  acetic  acid.  Magnified  320  diameters.  • 


CORNEA,  AND  CRYSTALLINE  LENS. 


159 


densely  interlaced  in  various  directions,  and  mingled  with  elastic  fibrous  tissue,  flatten  out 
into  a  membranous  form,  so  as  to  follow  in  the  main  the  curvatures  of  the  surfaces  of  the 
cornea,  and  to  constitute  a  series  of  more  than  sixty  lamellae,  intimately  united  to  one  ano- 
ther by  very  numerous  processes  of  similar  structure,  passing  from  one  to  the  other,  and 
making  it  impossible  to  trace  any  one  lamella  over  even  a  small  portion  of  the  cornea.  The 
resulting  areolae,  which  in  the  sclerotic  are  irregular,  and  on  all  sides  open,  are  converted  in 
the  cornea  into  tubular  spaces,  which  have  a  very  singular  arrangement,  hitherto  undescribed. 
They  lie  in  superposed  planes,  the  contiguous  ones  of  the  same  plane  being  for  the  most  part 
parallel,  but  crossing  those  of  the  neighbouring  planes  at  an  angle,  and  seldom  communica- 
ting with  them  (fig.  58).  The  arrangement  and  size  of  these  tubes  can  be  shown  by 

Fig.  58. 


Tubes  of  the  Cornea  Proper,  as  shown  in  the  eye  of  the  Ox  by  mercurial  injection.    Slightly  magnified. 

driving  mercury,  or  coloured  size,  or  air,  into  a  small  puncture  made  in  the  cornea.  They 
may  also  be  shown  under  a  high  power  by  moistening  a  thin  section  of  a  dried  cornea,  and 
opening  it  out  by  needles.  The  tissue  forming  the  parietes  of  these  tubes  is  membranous 
rather  than  fibrous,  though  with  the  best  glasses  a  fibrous  striation  may  be  frequently  seen, 
both  in  the  laminae  separating  the  different  series  of  tubes,  and  in  that  dividing  those  of  the 
same  layer  from  each  other.  By  acetic  acid,  also,  the  structure  swells,  and  displays  corpus- 
cles resembling  those  apparent  in  the  white  fibrous  tissue.  Such  is  the  lamellar  structure  of 
the  cornea,  which  makes  it  so  much  easier  to  thrust  an  instrument  horizontally  than  verti- 
cally into  its  substance.  The  tubes  or  elongated  spaces  of  which  we  have  spoken,  are  not 
distended  with  any  fluid,  but  are  merely  moistened  in  the  same  way  as  the  areolae  of  ordi- 
nary areolar  tissue.  A  perfectly  fresh  and  transparent  cornea  is  rendered  opaque  by  pres- 
sure, but  it  regains  its  brilliance  on  the  removal  of  the  compressing  force.  Some  have  sup- 
posed this  to  result  from  the  expulsion  of  fluid  from  between  its  laminae ;  but  that  the  opa- 
city is  owing  simply  to  a  derangement  of  the  elementary  parts  of  its  structure  is  plain  from 
the  fact,  that  the  same  phenomena  are  exhibited  by  a  section,  however  thin,  immersed  in 
water,  and  deranged  by  stretching.] 

190.  In  connection  with  the  cornea,  it  is  natural  to  allude  to  the  Crystal- 
line lens  and  Vitreous  humour,  which  have  a  structure  essentially  the  same. 
The  structure  of  the  Crystalline  lens  has  long  been  known  to  be  fibrous ;  and 
Sir  D.  Brewster  has  shown,  by  the  aid  of  polarized  light,  the  very  beautiful 
manner  in  which  the  fibres  are  arranged.*  They  are  united  into  laminae,  by 
means  of  numerous  teeth  or  sinuosities  at  their  edges,  which  lock  into  one 
another.  That  these  fibres  originate  in  cells,  has  been  clearly  ascertained  ; 
but  the  nature  of  the  metamorphosis  has  been  differently  stated  by  two  emi- 
nent observers,  Schwann  and  Barry.  By  the  former,  the  fibres  are  considered 
to  be  prolonged  cells :  whilst  the  latter  regards  them  as  rather  formed  upon 
the  plan  of  the  tubes  of  muscular  fibre  (§  235),  several  cells  coalescing  into 
one  ;  in  this  he  is  supported  by  Mr.  Toynbee*  who  states  that  he  has  fre- 
quently seen  the  fibres,  towards  the  margin  of  the  lens,  made  up  of  such  cells. 
After  it  is  fully  formed,  however,  it  is  not  permeated  by  blood-vessels ;  these 
being  confined  to  the  capsule.  During  the  early  part  of  foetal  life,  and  in  in- 
flammatory conditions  of  this  membrane,  both  the  anterior  and  posterior  por- 
tions of  the  capsule  are  distinctly  vascular;  but  at  a  later  period,  according  to 

*  Philosophical  Transactions,  1833. 


160  ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 

Mr.  Toynbee,  the  posterior  half  only  Of  the  capsule  has  vessels  distributed 
over  it  surface ;  and  these  are  derived  from  the  Arteria  centralis  retinae. 
From  optical  experiments  which  have  been  suggested  to  him  by  this  circum- 
stance, he  infers  that  "objects  (radiating  lines  for  instance),  situated  on  the 
anterior  surface  of  the  crystalline  lens,  produce  an  indistinctness  in  the  image 
which  is  formed  upon  the  retina;  whereas,  when  these  lines  exist  upon  the 
posterior  surface  of  the  lens,  the  image  is  clear."  The  substance  of  the  Lens 
contains  about  42  per  cent,  of  animal  matter,  with  58  parts  of  water.  Nearly 
the  whole  of  the  former  may  be  dissolved  in  cold  water  by  trituration ;  the 
solution  is  coagulated  by  heat,  and  forms  a  granular  but  not  coherent  mass; 
alcohol  and  acids  produce  the  same  effect.  Hence  it  appears  that  the  Lens 
chiefly  consists  of  albumen  in  its  soluble  form ;  and  this  may  be  supposed 
to  be  contained  in  the  cavities  of  the  cells,  as  it  is  in  those  of  the  vitreous 
humour.  From  the  latest  analyses,  it  appears  that  the  substance  of  the  lens 
corresponds  most  with  that  modification  of  albumen,  which  forms  the  Glo- 
buline  of  the  blood  (§  147). — In  the  Vitreous  humour,  we  have  an  example 
of  a  very  loose  form  of  cellular  tissue ;  strongly  resembling  that  which  con- 
stitutes the  entire  structure  of  Acalephae  (Jelly-fish).  That  the  cells  com- 
posing it  have  no  open  communication  with  each  other,  is  evident  from  the 
fact  that,  when  the  general  enveloping  membrane  is  punctured  in  several 
places,  it  is  long  before  the  contained  fluid  entirely  drains  away.  This 
fluid  is  analogous  to  that  of  the  Aqueous  humour ;  being  little  else  than  Wa- 
ter, holding  a  small  quantity  of  Albumen  and  Saline  water  in  solution.  From 
Mr.  Toynbee's  inquiries  it  would  appear,  that  the  vessels  which  pass  through 
the  Vitreous  humour  do  not  send  branches  into  its  substance ;  but  that  it  is 
nourished  by  the  vessels,  which  are  minutely  distributed  upon  its  general  en- 
velope. The  Ciliary  processes  of  the  Choroid  membrane  are  almost  entirely 
composed  of  large,  plexiform  vessels,  closely  resembling  those  of  synovial 
membrane  (Fig.  54),  which  allow  a  great  quantity  of  blood  to  circulate  through 
them  ;  and  these  have  probably  an  important  share  in  the  nutrition  of  the  Vi- 
treous body. 

191.  Cartilage  is  perfectly  insensible ;  and  neither  nerves  nor  lymphatics 
can  be  traced  into  its  substance.  Its  functions  are  purely  mechanical ;  the 
consolidation  of  its  texture  by  internal  deposit  renders  it  little  disposed  to 
change  by  spontaneous  decay ;  and  it  is  protected  by  its  toughness  and  elas- 
ticity from  those  injuries,  to  which  softer  or  more  brittle  tissues  are  liable. 
These  very  circumstances,  however,  interfere  with  the  activity  of  its  nutrition. 
Cells  which  are  choked  up  with  interior  deposit  do  not  readily  transmit  fluid : 
it  is  doubtful  whether  any  interstitial  change  can  take  place  in  the  interior  of 
a  permanent  Cartilage  (except  when  it  has  become  vascular  by  disease,  or 
undergoes  ossification),  through  the  whole  of  life;  and  there  seems  ground  to 
believe  that,  when  it  has  been  injured  by  disease  or  accident,  the  loss  of  sub- 
stance is  not  repaired  by  real  cartilaginous  tissue.  In  the  process  of  uleera- 
tion  of  Cartilage  (as  observed  by  Mr.  J.  Goodsir),it  appears  that  the  formation 
of  depressions  on  the  surface  is  due,  not  so  much  to  any  change  originating 
in  the  substance  of  the  cartilage,  as  to  the  eroding  action  of  the  cells  of  the 
false  membrane,  which  is  the  product  of  inflammatory  action  upon  its  surface  ; 
and  it  is  in  this  false  membrane  that  the  new  vessels  are  formed,  which  dip 
down  into  nipple-like  prolongations  of  the  membrane,  entering  corresponding 
hollows  excavated  in  the  cartilage. — On  the  other  hand,  the  softer  tissues  of 
the  Eye  are  capable  of  complete  regeneration.  Every  oculist  is  aware  that 
a  great  loss  of  Vitreous  humour  may  take  place  without  permanent  injury; 
and  it  has  been  found  that  even  the  Crystalline  lens  may  be  completely  rege- 
nerated, after  it  has  been  entirely  removed  by  extraction. 


CALCIFICATION  OF  FIBRES  AND  CELLS. 


161 


Fig.  59. 


9.   Tissues  consolidated  by  Earthy  deposit. — Bones  and  Teeth. 

192.  Both  the  Fibres  and  Cells  of  the  Animal  tissue,  there  is  reason  to  be- 
lieve, may  be  consolidated  by  mineral  deposits  ;  these  being  chemically  united 
with  the  Gelatine  of  the  Fibres ;  or  secreted,  either  alone,  or  in  combination 
with  gelatine,  into  the  cavities  of  the 
Cells,  by  their  own  inherent  powers. 
— We  have  an  example  of  the  form- 
ation of  a  skeleton  by  the  consoli- 
dation of  fibres,  in  the  shell  and 
other  hard  parts  of  the  Echinoder- 
mata ;  the  intimate  structure  of  which, 
as  shown  by  the  Microscope,  strong- 
ly reminds  us  of  Areolar  tissue  that 
might  have  undergone  the  calcifying 
process.  Again,  we  have  an  exam- 
ple of  the  formation  of  a  skeleton 
by  the  deposit  of  mineral  matter  in 
the  cavities  of  cells,  in  the  shells  of 
Mollusca;  in  many  of  which  (espe- 
cially among  the  Bivalves)  the  cellu- 
lar character  is  permanently  shown, 
— a  consistent  membrane  being  left, 
after  the  Carbonate  of  Lime  that  consolidated 
away  by  an  acid.  An  arrange- 
ment precisely  similar,  as  regards 
the  animal  constituent,  is  found 
in  the  Enamel  of  Teeth  (§  215) ; 
the  only  difference  being  in  the 
consolidating  material,  which  is 
chiefly  the  Phosphate  of  Lime, 
a  mineral  far  harder  than  the 


Calcified  Areolar  Structure,  of  which  the  Skele- 
ton of  the  Echinodermata  is  composed ;  from  the 
Spine  of  an  Echinus.  Magnified  150  diameters. 


the  cell  has  been  dissolved 


Fig.  60. 


Cellular  membrane,  left  after  the  removal  of  the  Cal- 
careous matter  from  the  shell  of  Pinna.  Magnified  185 
diameters. 


Carbonate.  It  is  not  always, 
however,  that  the  original  cells 
preserve  their  character  so  dis- 
tinctly; for  it  is  very  commonly 
found,  that  they  have  coalesced 
with  each  other,  in  such  a  man- 
ner as  not  to  be  distinguishable 
in  the  fully-formed  tissue.  We 
also  frequently  observe,  in  the 
skeletons  of  Vertebrata,  that  the 

whole  substance  is  not  consolidated,  but  that  cavities  and  channels  are  left  in 
it ;  which  seem  destined  to  perform  some  office  connected  with  the  interstitial 
changes,  that  continue  to  take  place  in  the  tissues  subsequently  to  their  first 
formation.  It  has  been  already  pointed  out  (§  5),  that  the  internal  bony  ske- 
letons of  Vertebrated  animals  are  destined  to  undergo  a  degree  of  interstitial 
change  (in  order  to  adapt  them  to  the  progressive  growths  of  the  parts  that 
cover  them),  which  is  not  required  in  the  external  envelopes  of  Invertebrated 
animals ;  these  being  capable  of  sufficient  enlargement  by  addition  to  their 
edges  merely ;  or  else  being  periodically  thrown  off,  and  renewed  upon  a 
larger  scale.  It  is  obvious  that,  if  the  whole  substance  be  consolidated  by 
calcareous  deposit,  there  can  be  no  permeation  of  nutritive  fluid  through  it; 
but,  on  the  other  hand,  if  it  be  traversed  by  tubuli,  commencing  from  the  near- 
est vascular  surface ;  or  if  a  series  of  minute  chambers,  connected  by  still 

14* 


162 


ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 


more  minute  passages,  be  excavated  in  its  substance,  it  is  evident  that,  even 
though  blood  cannot  circulate  through  it,  a  nutritive  fluid  drawn  from  the 
blood,  may  be  carried  into  its  minutest  parts.  This  is  the  kind  of  structure 
which  we  find  in  Bone,  and  in  the  principal  substance  of  Teeth.  The  mode 
in  which  it  is  generated,  will  become  the  subject  of  inquiry  hereafter. 

193.  When  examined  with  the  naked  eye,  it  is   seen  that  Bone  possesses 
in  some  degree  a  laminated  texture  :  in  the  long  bones,  the  external  and  in- 

Fig.  61. 


Portion  of  Transverse  Section  of  Human  Clavicle,  showing  the  orifices  of  the  Haversian  canals,  and 
the  concentric  arrangement  of  the  laminae  of  bony  matter,  and  of  the  lacunas,  around  them.  Magnified 
85  diameters. 

ternal  laminae  are  arranged  concentrically  round  the  medullary  canal ;  and  in 
the  flat  bones,  they  are  parallel  to  the  surface.  Towards  the  extremities  of 
the  long  bones,  and  between  the  external  plates  of  the  flat  bones,  are  a  num- 
ber of  cancelli,  or  small  hollows  bounded  by  very  thin  plates  of  bone  ;  these 
communicate  with  the  medullary  canal  where  it  exists ;  having,  like  it,  an 
extremely  vascular  lining  membrane ;  and  their  cavities  being  filled  with  a 
peculiar  adipose  matter.  The  hard  substance  of  the  bone  also  is  traversed  by 
canals,  on  which  the  name  of  Haversian  has  been  bestowed,  after  their  disco- 
verer ;  these  canals  run  for  the  most  part  in  the  direction  of  the  laminee  ;  but 
they  have  many  transverse  communications,  both  with  each  other  and  with 
the  medullary  cavity,  so  that  they  form  a  complete  network,  which  is  lined 
by  a  continuation  of  the  membrane  of  the  latter.  Their  diameter  varies  from 
l-200th  to  1 -2000th  of  an  inch;  the  average  being  probably  about  1-500. 
The  smaller  ones  contain  only  a  single  capillary  vessel ;  but  several  such  ves- 
sels seem  to  exist  in  the  larger  ones,  together  with  adipose  matter.  When  a 
thin  transverse  section  of  a  long  bone  is  made,  and  is  highly  magnified,  it  is 
seen  that  the  bony  matter  of  the  greater  part  of  its  thickness  is  arranged  in 
concentric  circles  round  the  orifices  of  the  canals  ;  these  circles  are  marked 
by  a  series  of  stellated  points ;  and  when  the  latter  are  magnified  still  more 
highly,  it  is  seen  that  they  are  cavities  or  lacunae  of  a  peculiar  form,  which 
seems  characteristic  of  Bone.  They  are  usually  oval  or  lenticular  in  form ; 
and  are  so  placed,  that  one  of  their  largest  surfaces  is  turned  from,  and  the 


STRUCTURE  OF  BONE.  ,  163 

other  towards,  the  Haversian  canal.     Their  long  diameter  is  commonly  from. 
[Fig.  62.  [Fig.  63. 


Transverse  section  of  the  compact  tissue 
of  along  Bone;  showing  1,  the  periosteal 
layer;  2,  the  medullary  layer,  and  the  inter- 
mediate Haversian  systems  of  lamellae,  each 
perforated  by  an  Haversian  canal.  Mag- 
nified about  15  diameters.] 


Transverse  section  of  the  compact  tissue  of  a  Tibia 
from  an  aged  subject,  treated  with  acid  ;  showing  the 
appearance  of  lamellae  surrounding  the  Haversian  ca- 
nals. Portions  of  several  systems  of  lamellae  are  seen. 
The  appearance  of  the  lacunae,  when  their  pores  are 
filled  with  fluid,  is  also  seen,  as  well  as  the  radiation 
from  the  canals  which  then  remain.  From  Mr.  Tomes.] 


1 -2400th  to  1-1 600th  of  an  inch  ;  their  short  diameter  is  about  one-third,  and 
their  thickness  about  one-sixth,  of  their  length. 

a.  It  has  been  lately  shown  by  Mr.  J.  Quekett,  that  there  are  differences  in  the  form  and 
size  of  the  lacunae,  in  the  several  classes  of  animals,  sufficiently  characteristic  to  allow  of  the 
assignment  of  minute  fragments  of  bone,  with  the  aid  of  the  microscope,  to  their  proper  class. 
The  lacunse  of  Reptiles  are  distinguishable  by  their  large  size,  and  long  oval  form;  and  those 
of  Fish,  by  their  angular  form  and  the  fewness  of  the  radiating  canaliculi.  The  osseous 
lacume  of  the  Bird  may  be  distinguished  from  those  of  the  Mammal,  partly  by  their  smaller 
size,  but  chiefly  by  the  remarkable  tortuosity  of  their  canaliculi,  which  wind  backwards  and 
forwards  in  such  a  manner,  as  frequently  to  destroy  the  concentric  lamellar  appearance.  It 
is  interesting  to  remark  further,  that  the  sizes  of  the  lacunse  in  the  four  classes  of  the  Verte- 
b rated  animals,  bear  a  close  relation  to  the  sizes  of  their  blood-corpuscles.  Here,  as  else- 
where, the  dimensions  of  the  ultimate  parts  of  the  tissue  are  tolerably  constant  in  each  group 
of  animals,  and  show  little  variation  in  accordance  with  the  size  of  the  species ;  thus  there 
is  little  or  no  perceptible  difference  in  the  size  of  the  elements  of  the  osseous  tissue  of  the 
enormous  extinct  Iguanodon,  and  of  the  smallest  Lizard  now  inhabiting  the  earth. 


Fig.  64. 


194.  From  all  parts  of  these  cavities, 
but  especially  from  their  two  largest 
surfaces,  proceed  a  large  number  of 
minute  tubuli,  which  traverse  the  sub- 
stance of  the  bone,  and  communicate 
irregularly  with  one  another.  Their 
direction,  however,  possesses  a  certain 
degree  of  determinateness  ;  for  those 
passing  off  from  the  inner  surface  con- 
verge towards  the  Haversian  canal ; 
whilst  those  passing  off  from  the  outer 

c  i-  ,1  j.  ijacunae   01    osseous    ouosiance ;     masrinueu 

surface  diverge   in   the  contrary  direc-     ^  diameters:     central  cuavity .  6>'it8  ramifica. 

tion,  so  as  to  meet  and  inosculate  with     tions. 

those    proceeding   inwards    from    the 

cavities  of  the  next  annulus.     In  this   manner,  a  communication  is  kept  up 

between  the  Haversian  canal,  and  the  most  external  of  its  concentric  lamellae 


Lacunae  of    Osseous    Substance;    magnified 


164 


ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 


Haversian  canals,  seen  on  a 
longitudinal  section  of  the  com- 
pact tissue  of  the  shaft  of  one  of 
the  long  bones:  1,  arterial  canal; 
2,  venous  canal ;  3,  dilatation  of 
another  venous  canal.] 


of  bone.     It  is  not  to  be  imagined,  however,  that  blood  can  be  conveyed  by 
these  tubuli,   their  size  being  far   too  small ;  for 
[Fig.  65.  their  diameter,  at  their  largest  part,  is  estimated  at 

from  1-1 4,000th  to  l-20,000th  of  an  inch,  whilst 
that  of  the  smaller  branches  is  from  l-40,000th  to 
l-60,000th  of  an  inch  ;  so  that  the  blood-corpus- 
cles could  not  possibly  enter  them.  But  it  may  be 
surmised  that  they  draw  fluid  from  the  nearest 
blood-vessels,  and  thus  keep  up  a  sort  of  circulation 
through  the  osseous  substance,  which  may  con- 
tribute to  its  growth,  and  may  keep  it  in  a  state  fit 
for  repairing  itself,  when  injured  by  disease  or  vio- 
lence. The  lacunas,  however,  do  not  seem  to  be 
unoccupied  in  the  living  bone ;  for  each  contains 
(according  to  Mr.  J.  Goodsir)  a  minute  granular 
substance,  which  seems  to  be  identical  with  the 
nucleus  of  the  original  bone-cell,  and  which  pro- 
bably serves  as  a  "  nutritive  centre," — attracting  to 
itself,  through  its  own  system  of  canaliculi,  the 
nutritive  materials  supplied  by  the  blood-vessels  of 
the  nearest  surface,  and  diffusing  these  through  the 
surrounding  substance.* 

195.  Although  a  large  quantity  of  blood  is  sent 
to  Bone,  the  vessels  do  not  penetrate  its  minute 
parts ;  being  confined  to  the  Medullary  cavity, 
and  to  the  Haversian  Canals,  and  Cancelli,  which 
are  prolongations  of  it.  The  substance  of  the  Bone, 
therefore,  is  really  as  non-vascular  as  that  of  Carti- 
lage ;  the  only  difference  being,  that  it  is  channelled  out  by  more  numerous 
inflexions  of  the  external  surface,  and  that  the  vessels  are  thus  brought  into 
nearer  proximity  with  its  several  parts.  The  delicate  osseous  lamella,  which 
form  the  walls  of  the  cancelli,  and  of  the  large  cells  excavated  in  some  of  the 
cranial  bones,  have  a  structure  precisely  analogous  to  that  of  the  cylindrical 
laminae  surrounding  the  Haversian  canals  of  the  long  bones ;  and  derive  their 
nourishment  from  the  vascular  membrane  covering  their  surface,  through  the 
medium  of  a  similar  set  of  lacunas  and  canaliculi.  They  do  not  themselves 
contain  Haversian  canals  or  cancelli ;  because  no  part  of  their  substance  is  far 
removed  from  a  vascular  membrane.  The  cylindrical  rods,  that  make  up  the 
hollow  shaft  of  a  long  bone,  are  connected  together  by  solid  osseous  sub- 
stance, which  is  composed  of  lamellae  running  parallel  to  the  external  surface 
of  the  bone ;  and  these  derive  their  nutriment  either  from  the  periosteum,  or 
from  the  membrane  lining  the  great  central  medullary  cavity ;  according  as 
they  are  nearest  to  one  or  to  the  other. — The  membranous  lining  of  the  canals 
of  Bone  appears  to  be  supplied  with  lymphatics,  and  also  with  nerves ;  but 
with  both  in  a  very  limited  amount.  The  periosteum  seems  to  be  scarcely 
(if  at  all)  sensible  in  the  state  of  health,  although  painfully,  so-when  inflamed  ; 
and  the  same  may  be  said  of  the  membrane  lining  the  Haversian  canals  and 
cancelli.  The  membrane  lining  the  central  medullary  cavity,  however,  is  more 

*  The  lacunae  and  canaliculi  of  Bone  were  formerly  supposed,  on  account  of  the  black 
appearance  th/ey  exhibit  under  the  Microscope,  to  be  filled  with  opaque  matter  5  but  this  ap- 
pearance is  common  to  all  cavities  excavated  in  a  highly-refracting  substance  (being  shown 
by  a  bubble  of  air  in  water),  and  ceases  when  a  very  thin  section  of  Bone  is  examined,  es- 
pecially if  it  have  been  placed  in  Canada  Balsam.  In  the  Bones  of  Mummies,  they  are  found 
to  be  filled  with  a  waxen  material ;  and  in  those  which  have  lain  in  bogs,  they  are  rendered 
peculiarly  distinct  by  the  infiltration  of  some  of  the  surrounding  black  matter :  so  that  their 
power  of  imbibing  liquids  is  clearly  proved. 


STRUCTURE  AND  COMPOSITION  OF  BONE.  165 

sensitive ;  since  unequivocal  signs  of  pain  are  manifested  by  an  animal,  when, 
a  bone  having  been  sawn  across,  a  probe  is  passed  up  the  cavity,  or  an  acrid 
fluid  is  injected  into  it. 

196.  The  ultimate  substance  of  Bone,  lying  between  the  lacunae  and  cana- 
liculi,  appears  to  be  usully  granular ;  the  granules  are  stated  by  Mr.  Tomes* 
to  be  often  distinctly  visible  without  any  artificial  preparation,  in  the  sub- 
stance of  the  delicate  spicula  of  the  cancelli,  when  they  are  viewed  with  a 
high  power ;  and  to  be  made  very  evident  by  prolonged  boiling  in  a  Papin's 
digester.  They  vary  in  diameter  from  1 -6000th  to  1-1 4,000th  of  an  inch  ; 
their  shape  is  oval  or  oblong,  often  angular;  and  they  cohere  firmly  together, 
possibly  by  the  medium  of  some  different  material.  Their  own  substance, 
however,  appears  to  be  perfectly  homogeneous ;  but  it  is  made  up  of  several 
components,  as  appears  from  the  following  statements  regarding  the  chemical 
composition  of  Bone. 

a.  When  the  Calcareous  matter  of  Bone  has  been  dissolved  away  by  the  action  of  an  acid, 
the  Animal  substance  which  remains  is  almost  entirely  dissolved  by  a  short  boiling  in  water; 
yielding  to  it  a  large  quantity  of  Gelatine.  This,  indeed,  may  be  obtained  by  long  boiling 
under  pressure,  from  previously-unaltered  Bone ;  and  the  calcareous  matter  is  then  left  almost 
pure.  The  Lime  of  bones  is,  for  the  most  part,  in  the  state  of  Phosphate,  especially  among 
the  higher  animals;  it  is  curious,  however,  that  in  callus  and  exostosis,  there  is  a  much  larger 
proportion  of  Carbonate  of  lime,  than  in  the  sound  bone ;  in  which  respect  these  formations 
correspond  with  the  bones  of  the  lower  animals ;  but  in  caries,  the  quantity  of  the  carbonate 
is  much  smaller  than  usual.  The  composition  of  the  Phosphate  of  Lime  in  Bones  is  peculiar ; 
8  equiv.  of  the  base  being  united  with  3  of  the  acid.  According  to  Prof.  Graham,  it  is  to  be 
regarded  as  a  compound  of  two  tribasic  phosphates ;  namely,  2  Ca,  O,  H  0,  P  05-f-2  (3  Ca  0, 
P  O5) ;  with  the  addition  of  an  equiv.  of  water,  which  is  driven  off  by  calcination.  The  fol- 
lowing are  the  results  of  some  of  the  most  recent  and  careful  analyses  of  Human  Bone,  by 
Marchand  and  Lehmann:  those  of  the  former  were  made  on  the  compact  substance  of  the 
femur  of  a  man  aged  30 ;  and  those  of  the  latter  on  the  long  bones  of  the  arm  and  leg  of  a 
man  of  40  years  of  age. 

Organic  matter.  MARCHATTD.     LEHMANK. 

Cartilage  insoluble  in  hydrochloric  acid  .         .         .  27-23  } 

Cartilage  soluble  in  hydrochloric  acid      .         .         .         5-02  V      32-56 

Vessels        .  1-01  ) 

Inorganic  matter. 

Phosphate  of  lime 52*26  )      -.^ 

Fluoride  of  calcium         .         .         .         .         .         .         TOO  ( 

Carbonate  of  lime 10'21  9'41 

Phosphate  of  magnesia 1-05  T07 

Soda -92  Ml 

Chloride  of  sodium 0-25  0'38 

Oxide  of  iron  and  manganese,  and  loss  .         .         1-05  -86 


100-00  100-00 

b.  According  to  Dr.  Stark,f  the  relative  proportions  of  cartilaginous  and  earthy  matter,  in 
the  bones  of  different  animals,  in  the  bones  of  the  same  animals  at  different  ages,  and  in  the 
different  bones  of  the  same  body,  never  depart  widely  from  the  preceding  standard;  the 
amount  of  earthy  matter  being  always  found  to  be  just  double  that  of  the  cartilaginous  basis, 
when  the  bones  have  been  carefully  freed  from  oily  matter,  and  completely  dried,  previously 
to  the  analysis.  The  hardness  of  bone,  he  maintains,  does  not  at  all  depend  upon  the  pre- 
sence of  an  unusually  large  proportion  of  earthy  matter;  nor  does  their  increased  flexibility 
and  transparency  indicate  a  deficiency  of  the  mineral  ingredients  ;  for  the  transparent  readily- 
cut  bones  of  fish  contain  the  same  amount  of  earthy  matter,  in  proportion  to  their  gelatinous 
basis,  as  do  the  dense  ivory-like  leg-bones  of  the  deer  or  sheep.  The  same  holds  good  of 
the  bones  even  of  the  so-called  Cartilaginous  Fish.  The  difference  seems  to  depend  upon 
the  molecular  arrangement  of  the  ultimate  particles ;  and  especially,  it  seems  likely,  upon 
the  relative  amount  of  water  which  the  bones  contain. 


*  Todd  and  Bowman's  Physiological  Anatomy,  p.  108,  and  Cyclopaedia  of  Anatomy,  art. 
Osseous  Tissue. 

f  Edinburgh  Med.  and  Surg.  Journal,  April  1845. 


166 


OF  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 


c.  Probably  the  most  exact  and  comprehensive  analyses  yet  made  of  Bone,  are  those  of 
Von  Bibra;*  whose  laborious  investigations  may  be  said  to  have  almost  exhausted  the  sub- 
ject. The  following  table  shows  the  relative  proportions  of  the  principal  ingredients  in  some 
of  the  principal  bones  of  a  woman  aged  25  years. 

Occipital 

Scapula. 
Organic  matter. 
Cartilage 
Fat      . 

Inorganic  matter. 
Phosphate  of  lime  } 

54-75 


Femur. 

29-54 
1-82 


bone. 

29-87 
1-40 


Os  innomi- 
natum.     Vertebra.  Sternum. 


32-90 
1-73 


33-06 
2-37 


38-26 
1-77 


43'44 
2-31 


46-57 
2-00 


with  a  little  fluo-  >  57-42  57-66  54-75  52-91 

ride  of  calcium.    ) 

Carbonate  of  lime         .  8-92  8-75  8'58  8-66 

Phosphate  of  magnesia  1-70  1-69  1-53  1-40 

Soluble  salts         .         .  0-60  0-63  0-51  0-60 


49-72         44-28 


42-63 


8-08 
1-57 
0-60 


8-00 
1-44 
0-53 


100-00       100-00       100-00       100-00       100-00       100-00 

The  analyses  of  the  long  bones  of  the  arm  and  leg  correspond  closely  with  that  of  the 
femur ;  but  we  observe  that  the  proportions  of  ingredients  in  the  more  spongy  bones  are 
widely  different.  It  is  difficult,  however,  to  say  how  far  this  variation  is  due  to  a  difference 
in  the  proportions  of  gelatine  and  earthy  matter,  in  the  actual  osseous  substance ;  or  how  far 
it  may  be  accounted  for  by  the  presence  of  an  increased  proportion  of  membrane,  forming 
the  lining  of  the  cancelli. — The  same  uncertainty  must  attend  the  explanation  of  the  differ- 
ences that  present  themselves  at  different  ages  5  as  shown  in  the  following  table,  which  gives 
the  comparative  analyses  of  the  long  bones  (generally  the  femur)  at  different  ages. 

Foetus         Foetus  Child  Child  Man        Woman 

6  months.    7  months.    2  months.      5  years.      25  years.  62  years. 
Organic  matter. 

Cartilage 40-38         34-18         33-86         31-28         29-70         28-03 

Fat a  trace         0-63  0-82  0-92  1-33  2-15 

Inorganic  matter. 
Phosphate  of  lime  ) 

with  a  little  fluo-  V  .         .     53-46         57-63         57-54         59-96         59-63         63-17 

ride  of  calcium.    ) 

Carbonate  of  lime        .         .         .       3-06  5-86  6-02  5-91  7-33  4-46 

.       2-10  1-10  1-03  1-24  1-32  1-29 

1-00  0-60  0-73  0-69  0-69  0-90 


Phosphate  of  magnesia 
Soluble  salts 


100-00       100-00       100-00       100-00       100-00       100-00 

From  this  it  will  be  seen  that  there  is  a  gradual  diminution  in  the  proportion  of  animal 
matter,  through  life;  and  a  corresponding  increase  in  the  proportion  of  the  earthy  components. 
But  this  is  not  nearly  so  great  as  is  usually  supposed ;  and  the  greater  solidity  of  the  bones 
of  old  persons  is  doubtless  owing  chiefly  to  the  fact,  that  their  cavities  are  progressively  con- 
tracted, by  the  addition  of  new  bony  matter  (§201). 

d.  The  following  comparative  analysis  of  the  bones  of  different  animals,  are  selected  from 
the  very  extensive  series  given  by  Von  Bibra;  which  contains  143  of  Mammalia  (independ- 
ently of  Man),  151  of  Birds,  31  of  Reptiles,  and  23  of  Fishes.  They  were  mostly  made 
upon  the  long  bones ;  except  in  the  case  of  Fishes,  in  which  they  were  made  upon  the  Ver- 
tebrae. 

Sheep.       Horse.        Wolf.      Thrush.      Frog.          Cod.      Salmon. 


Organic  matter. 

Cartilage 

Fat 

Inorganic  matter. 

Phosphate  of  lime  with 
a  little  fluoride  of  cal- 
cium. 

Carbonate  of  lime 

Phosphate  of  magnesia 

Soluble  salts 


29-68 
0-70 


27-99 
3-11 


27-44 
1-45 


28-02 
1-54 


30-19 
5-31 


31-90 
2-34 


21-80 

38-82 


55-94       54-37       57-87       62-65       59-48       57-65       36-84 


12-18  12-00 
1-00  1-83 
0-50  0-70 


11-09 
1-13 
1-02 


6-05 
0-90 
0-84 


2-25 
0-99 
1-78 


4-81 
2-30 
1-00 


1-01 
0-70 
0-83 


100-00     100-00     100-00     100-00     100-00     100-00     100-00 


*  Chemische  Untersuchungen  iiber  die  Knochen  und  Ziihne  des  Menschen,  und  der  Wir. 
belthiere. 


COMPOSITION  AND  DEVELOPMENT  OF  BONE.  167 

It  will  be  observed  that,  in  all  cases,  the  proportion  between  the  cartilaginous  basis  and 
the  earthy  matter  is  very  nearly  the  same ;  being  almost'  exactly  as  1  to  2,  even  where  the 
composition  of  the  bone  is  most  altered,  by  the  presence  of  an  unusual  quantity  of  fatty  mat- 
ter.  Hence  there  is  strong  reason  to  believe,  that  a  definite  chemical  compound  is  formed 
by  the  union  of  the  Gelatine  and  Earthy  salts ;  and  this  corresponds  well  with  the  fact 
already  noticed,  in  regard  to  the  homogeneousness  of  the  ultimate  particles  of  bone. 

197.  The  first  Development  of  Bone  may  take   place  in   the  substance, 
either  of  Membrane,  or  of  Cartilage.*     The  tabular  bones  forming  the  roof 
of  the  cranium  afford  a  good  example  of  the  first,  or  intramembranous  form 
of  Ossification ;  for  their  place  is  but  in  part  pre-occupied  by  cartilage ;  only 
a  membrane  being  elsewhere  interposed  between  the  dura  mater  and  the  in- 
teguments.    This  membrane  is  chiefly  composed  of  fibrous  fasciculi,  corre- 
sponding with  those  of  the  white  fibrous  tissues  ;  but  amongst  these  are  seen 
numerous  cells,  some  about  the  size  of  blood-discs,  but  others  two  or  three 
times  larger,  containing  granular  matter ;  and  a  soft  amorphous  or  faintly- 
granular  matter  is  also  found  interposed  amidst  the  fibres  and  cells.     In  cer- 
tain parts,  the  fibres  predominate  ;  and  in  others,  the  cells.    The  process  of  ossi- 
fication here  seems  at  first  to  consist  in  the  consolidation  of  the  fibres  by  earthy 
matter ;  for  the  first  bony  deposit  consists  of  an  irregular  reticulation,  very  loose 
and  open  towards  its  edges,  and  there  frequently  presenting  itself  in  the  form 
of  distinct  spicula,  which  are  continuous  with  fasciculi  of  fibres  in  the  sur- 
rounding membrane.     The  limits  of  the  calcifying  deposit  may  be  traced  by 
the  opaque  and  granular  character  of  the  parts  affected  by  it,  and  it  gradually 
extends  itself,  involving  more  and  more  of  the  surrounding  membrane,  until  the 
foundation  is  laid  for  the  entire  bone.     Everywhere  the  part  most  recently 
formed  consists  of  a  very  open  reticulation  of  fibro-calcareous  spicula  ;  whilst 
the  older  part  is  rendered  harder  and   more   compact,  by  the  increase  in  the 
number  of  these  spicula,  and  perhaps  also  by  the  calcification  of  the  interve- 
ning cells.     As  the  process  advances,  and  the  plate  of  bone  thickens,  a  series 
of  grooves  or  furrows,  radiating  from  the  ossifying  centre,  are  found  upon  its 
surface  ;  and  these  by  a  further  increase  in  thickness,  occasioned  by  a  deposit 
of  ossific  matter  all  around  them,  are  gradually  converted  into  closed  canals 
(the  Haversian),  which  contain  blood-vessels,  supported  by  processes  of  the 
investing  membrane.    Further  deposits  subsequently  take  place  in  the  interior 
of  these  canals  ;  which  thus  gradually  produce  a  diminution  of  their  calibre, 
and  a  consolidation  of  the  bone ;  and  in  this  manner  its  two  surfaces  acquire 
their  peculiar  density,  whilst  the  intervening  layer  or  diploe  retains  a  charac- 
ter more  resembling  that  of  the  original  osseous  reticulation. — The  mode  in 
which  the  peculiar  lacunae  and  canaliculi  are  formed,  in  the  concentric  layers 
around  the  Haversian  canals,  probably  corresponds  with  that  in  which  they 
are  generated  in  the  intracartilaginous  form  of  ossification,  to  which  we  shall 
next  proceed. 

198.  In  a  very  large  proportion  of  the  skeleton,  the  appearance  of  the  Bones 
is  preceded  by  that  of  Cartilages  ;  which  present  the  same  form,  and  which 
seem  destined  to  afford  a  certain  degree   of  support,  to  the  surrounding  soft 
parts,  until  the  production  of  Bone  has  taken  place.     As  already  mentioned 
(§  187),  the  temporary  cartilages  differ  in  no  essential  particular  from  the  per- 
manent.  They  present  the  same  irregular  scattering  of  cells  through  a  homo- 
geneous intercellular  substance,  and  there  is  the  same  absence  of  any  vascu- 

*  In  recent  times,  the  development  of  Bone  from  Cartilage  has  received  almost  exclusive 
attention ;  but  the  older  opinion,  that  Bone  is  often  developed  in  Membrane,  has  been  lately 
brought  again  into  notice  by  Dr.  Sharpey  (Introduction  to  Fifth  Edition  of  Quain's  Anatomy), 
who  has  demonstrated  its  truth  by  Microscopic  research.  The  statements  in  the  text,  upon 
this  part  of  the  subject,  are  derived  from  Dr.  Sharpey's  observations,  which  the  author  has 
since  confirmed. 


168 


ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 


larity  in  the  Cartilaginous  tissue  itself.  In  all  considerable  masses,  how- 
ever, we  find  a  coarse  network  of  canals,  lined  by  an  extension  of  the  peri- 
chondrium  or  investing  membrane ;  and  these  canals,  which  may  be  regarded 
as  so  many  involutions  of  the  external  surface,  allow  the  vessels  to  come  into 
nearer  relation  with  the  interior  parts  of  the  Cartilaginous  structure,  than 
they  would  otherwise  do.  They  are  especially  developed  at  certain  points, 


Fig.  66. 


[Fig.  67. 


Section  of  Cartilage  at  the  seat  of 
ossification ;  the  clusters  of  cells  are 
arranged  in  columns ;  the  intercellular 
spaces  between  the  columns  being 
l-3250th  of  an  inch  in  breadth.  At  the 
lower  end  of  the  figure,  osseous  fibres 
are  seen  occupying  the  intercellular 
spaces,  at  first  bounding  the  clusters 
laterally,  then  splitting  them  longitudi- 
nally and  encircling  each  separate  cell. 
The  greater  opacity  of  this  portion  is 
due  to  a  threefold  cause;  the  increase  of 
osseous  fibres,  the  opacity  of  the  con- 
tents of  the  cells,  and  the  multiplica- 
tion of  oil-globules. 


Vertical  section  of  Cartilage  near  the  surface  of  ossifi- 
cation; 1,  ordinary  appearance  of  the  temporary  cartilage; 
1',  portion  of  the  same  more  highly  magnified;  2,  the  cells 
beginning  to  assume  the  linear  direction;  2',  portion  more 
magnified;  opposite  3,  the  ossification  is  extending  in  the 
intercellular  spaces,  and  the  rows  of  cells  are  seen  resting 
in  the  cavities  so  formed,  the  nuclei  being  more  separated 
than  above;  3',  portion  of  the  same  more  highly  magnified. 
From  a  new-born  rabbit  which  had  been  preserved  in 
spirit.] 


which  are  to  be  the  centres  of  the  ossifying  process  ;  and  it  is  always  observ- 
able, that  the  vascularity  is  greatest  at  the  zone,  in  which  the  conversion  of 
cartilage  into  bone  is  actually  taking  place.  During  the  extension  of  the  vas- 
cular canals  into  the  Cartilaginous  matrix,  certain  changes  are  taking  place 


OSSIFICATION  OF  CARTILAGE.  169 

in  the  substance  of  the  latter,  which  are  preparatory  to  its  conversion  into 
Bone.  Instead  of  single  isolated  cells,  or  groups  of  two,  three,  or  four,  such 
as  we  have  seen  to  be  characteristic  of  ordinary  Cartilage  (Fig.  52),  we  find, 
as  we  approach  the  centre  or  line  of  ossification,  clusters  made  up  of  a  larger 
number  arranged  in  a  linear  manner ;  which  seem  to  be  formed  by  a  continu- 
ance of  the  same  multiplying  process  as  that  formerly  described  (Fig.  66). 
And  when  we  pass  still  nearer,  we  see  that  these  clusters  are  composed  of  a 
yet  greater  number  of  cells,  which  are  arranged  in  long  rows,  whose  direc- 
tion corresponds  to  the  longitudinal  axis  of  the  bone ;  these  clusters  are  still 
separated  by  intercellular  substance ;  and  it  is  in  this,  that  the  ossific  matter 
is  first  deposited.  If  we  separate  the  cartilaginous  and  the  osseous  substance 
at  this  stage  of  the  process,  we  find  that  the  ends  of  the  rows  of  cartilage- 
cells  are  received  into  deep  narrow  cups  of  bone,  formed  by  the  calcification 
of  the  intercellular  substance  between  them.  Thus  the  Bone  first  formed  in 
the  cartilaginous  matrix,  is  seen  to  consist  of  a  series  of  lamellae  of  a  some- 
what cylindrical  form  ;  inclosing  oblong  areola?,  or  short  tubular  cavities, 
within  which  the  piles  of  cartilage-cells  yet  lie :  and  it  thus  corresponds 
closely  with  the  reticular  structure,  which  first  makes  its  appearance  in  the 
intra-membranous  form  of  the  process. — So  far  it  would  appear  that  the  blood- 
vessels are  not  directly  concerned  in  the  operation;  for  although  they  advance 
to  the  near  neighbourhood  of  the  first  ossific  deposit,  they  do  not  make  their 
way  into  its  substance,  or  even  into  the  intervening  areolae. 

199.  This  state  of  things,  however,  speedily  gives   place  to  another.     On 
examining  the  subjacent  portion,  in  which  the  ossification  has  advanced  further, 
it  is  found  that  the  original  closed  cavities  have  coalesced  to  a  certain  extent 
(probably  by  the  absorption  of  their  walls),  both  laterally  and  longitudinally; 
and  that  they  now  receive  numerous  blood-vessels,  prolonged  into  them  from 
the  previously-ossified  portion.     The  groups  of  cartilage-cells,  which  origi- 
nally occupied  the  cavities,  are  no  longer  seen ;  and  their  place  is  filled  with 
a  blastema,  composed  of  cells,  containing  a  granular  matter,  and  closely  re- 
sembling those  seen  in  the  intra-membranous  ossification,  with  a  few  fibres 
scattered  amongst  them.     It  is  by  a  change  in  this  blastema,  that  the  walls  of 
the  cavities  are  gradually  consolidated;  new  deposits  of  ossific  matter  being 
formed  in  their  interior,  which  occasion  the  gradual  contraction  of  the  cavities, 
and  give  an  increasing  density  to  the  bone.     The  cancellated  structure,  which 
remains  for  a  time  in  the  interior  of  the  long  bones,  and  which  continues  to 
occupy  their  extremities,  represents  the  early  condition  of  the  ossifying  sub- 
stance, with  very  little  change ;  whilst  the  cavities,  which  have  formed  more 
regular  communications  with  each  other,  and  which  have  been  gradually  con- 
tracted by  the  subsequent  deposit  of  concentric  lamella?,  one  within  another, 
form   the   original  Haversian   canals.     Thus  we  see   that  they  all  form  one 
system  in   their  origin ;  as  they  may  be  considered  to  do,  notwithstanding 
the  difference  of  their  form,  in  the  complete  bone. 

200.  The  original  osseous  lamella?,  formed  by  the  consolidation  of  the  car- 
tilaginous substance,  are  entirely  composed  of  granular  matter ;  and  exhibit 
none  of  the  lacuna?  and  canaliculi,  which  are  commonly  regarded  as  charac- 
teristic of  Bone.     These  excavations  present  themselves,  however,  in  all  the 
subsequent  deposits  ;  and  into  the  origin  of  these,  we  have  now  to  inquire. 
According  to  the  views  of  some  Microscopists,  the  cells  of  the  blastema  fill 
themselves  with  ossific  matter,  except  at  the  points  occupied  by  the  nuclei ; 
at  the  same  time,  they  become  flattened  against  the  walls  of  the  canals,  and 
their  nuclei  send  out  radiating  prolongations  ;  so  that,  when  the  calcification 
of  the  cell  has  been  completed,  a  stellate   cavity  is  left  in  the  hard  deposit, 
which  is  occupied  by  the  granular  matter  of  the  nucleus.     The  centre  of  this 
cavity  forms  the  lacuna,  in  which  the  original  granular  matter  may  frequently 

15 


170  ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 

be  found  remaining,  and  presenting  an  appearance  as  if  developed  into  a  cluster 
of  minute  cells;  whilst  its  prolongations  form  the  canaliculi,  from  which  the 
nuclear  matter  seems  afterwards  to  disappear  altogether.  This  view  is  sup- 
ported by  several  considerations ;  amongst  others,  by  the  fact  of  the  existence 
of  such  stellate  nuclei  in  many  Vegetable  cells  (Fig.  14);  and  by  the  corre- 
sponding appearances  witnessed  by  Professor  Owen  in  the  formation  of  the 
Cementum  of  Teeth,  a  structure  identical  with  bone,  and  produced  by  the 
calcification  of  the  capsule  (§  216). — Others,  again,  regard  the  lacunae  and 
their  radiating  prolongations  as  themselves  constituting  cells ;  and  examples 
are  not  wanting  of  similar  forms  in  bodies  known  to  have  this  character,  as 
the  pigment-cells  of  the  skin  of  Batrachia  (Fig.  90,  c). — Dr.  Sharpey,  on  the 
other  hand,  states  as  the  result  of  his  observations,  that  the  concentric  layers 
within  the  Haversian  canals  are  formed  by  a  process  analogous  to  the  intra- 
inembranous  ossification ;  namely,  by  the  calcification  of  successive  layers  of 
fibres,  generated  in  the  blastema,  and  possibly  derived  from  the  granular  cells. 
These  fibres,  being  arranged  in  a  reticular  manner,  may  here  and  there  include 
an  entire  cell  or  cell-nucleus,  the  presence  of  which  may  determine  the  posi- 
tion of  a  lacuna;  whilst  the  canalicula  may  result  from  the  apposition  of  the 
minute  apertures,  existing  between  the  other  reticulations  of  the  decussating 
fibres.  This  view  seems  to  derive  confirmation  from  the  appearances  pre- 
sented by  very  thin  shreds  of  the  gelatinous  matrix,  left  after  the  removal  of 
the  calcareous  matter  by  acid ;  for  these,  according  to  Dr.  S.,  are  plainly  com- 
posed of  transparent  fibres,  resembling  those  of  the  white  fibrous  tissues,  in- 
tersecting one  another  at  acute  angles,  and  forming  a  network,  in  the  meshes 
of  which  are  minute  perforations,  that  are  nothing  else  than  transverse  sections 
of  the  canaliculi. 

201.  In  the  formation  of  a  long  bone,  we  usually  find  one  centre  of  ossifi- 
cation in  the  shaft,  and  one  in  each  of  the  epiphyses ;  in  the  flat  bones,  there 
is  one  in  the  middle  of  the  surface,  and  one  in  each  of  the  principal  processes. 
The  ossification  usually  proceeds  to  a  considerable 
[Fig.  68.  extent,  however,  in  the  main  centre,  before  it  com- 

mences in  the  extremities  or  processes ;  and  these 
remain  distinct  from  the  principal  mass  of  the  bone, 
long  after  this  has  acquired  solidity.  During  the 
spread  of  the  ossifying  process,  the  cartilaginous 
matrix  continues  to  grow,  like  cartilage  in  other 
parts;  but  after  the  bony  deposit  has  pervaded  its 
entire  substance,  in  the  manner  just  described,  a 
change  takes  place  in  the  method  adopted.  The 
osseous  laminae,  that  subdivide  the  whole  texture, 
are  removed  by  absorption  from  the  interior  of  the 
shaft,  so  as  to  leave  the  great  central  medullary 
cavity ;  whilst,  on  the  other  hand,  they  receive  pro- 
gressive additions  in  the  external  portion,  which  is 
Scapula  of  a  Fcetus  at  the  thus  gradually  consolidated  into  the  dense  bone, 
seventh  month ;  showing  the  pro-  that  forms  the  hollow  cylinder  of  the  shaft.  This 
gress  of  ossification.  Natural  consolidation  is  effected  by  the  deposit  of  a  series 

size.  The  light  parts  are  epiphy-  Qf  concentric  lamimfi  one  wilhin  another,  On  the 
ses  as  yet  cartilaginous.- From  ,.  .  „  ,  TT  ' 

the  Museum  of  King's  College,    hning  of  the  Haversian  canals.— The  bone  con- 
London.]  tinues  to  increase  in  diameter,  by  the  formation  of 
new  layers  upon  its  exterior ;  and  Dr.  Sharpey  has 

pointed  out  that  these  layers  are  formed,  not  (as  usually  stated)  in  a  cartila- 
ginous matrix,  but  in  the  substance  of  a  membrane,  consisting  of  fibres  and 
granular  cells,  and  exactly  resembling  that  in  which  the  flat  bones  of  the  roof 
of  the  skull  are  developed.  The  Haversian  canals,  too,  of  these  new  layers 


DEVELOPMENT  AND  GROWTH  OF  BONE.  171 

are  formed  in  the  same  manner  as  those  of  the  tabular  bones  of  the  skull ;  the 
osseous  matter  being  not  only  laid  on  in  strata  parallel  to  the  surface,  but  also 
being  deposited  around  processes  of  the  vascular  membranous  tissue,  which 
extend  obliquely  from  the  surface  into  the  substance  of  the  shaft;  the  canals, 
in  which  these  membranous  processes  lie,  becoming  narrowed  by  the  depo- 
sition of  concentric  osseous  laminae,  and  at  last  remaining  as  the  Haversian 
canals.  Whilst  this  new  deposition  is  taking  place  on  the  exterior  of  the 
shaft,  absorption  of  the  inner  and  older  layers  goes  on :  so  that  the  central 
cavity  is  proportionably  enlarged. — The  increase  of  the  bone  in  length  ap- 
pears due  to  the  growth  of  the  cartilage  between  the  shaft  and  the  epiphyses, 
so  long  as  this  remains  unconsolidated  by  ossific  deposit ;  and  this  state  con- 
tinues, until  the  bone  has  acquired  nearly  its  full  dimensions.  What  further 
increase  it  gains,  seems  chiefly  if  not  entirely  due  to  the  progressive  ossifica- 
tion of  the  articular  cartilage  covering  the  extremities ;  which  progressively 
diminishes  in  thickness  during  the  whole  of  life,  and  which  in  old  age  some- 
times appears  to  have  been  almost  completely  converted  into  bone. 

202.  It  thus   appears  doubtful,  whether  there  be   anything  like   a  proper 
interstitial  growth   in  bone ;   that  is,  whether  the  part,  through  which   the 
ossific  process  has  made  its  way,  is  capable  of  any  further  extension  than  by 
addition  to  its  surface.     By  the  admirable  system  of  prolongations,  however, 
by  which  the  vascular  membrane  is  conveyed  into  its  intimate  substance,  we 
find  this  method  of  superficial  deposit  adapted  to  the  consolidation  of  parts,  at 
first  sketched  out  (as  it  were)  by  a  slight  osseous  reticulation  ;  whilst  by  the 
facility  with  which  the  bony  matter  is  absorbed  in  the  internal  part  of  the  shaft, 
whilst  it  is  being  deposited  upon  its  exterior,  the  same  effect  is  produced,  as 
if  the  whole  cylinder  could  enlarge  uniformly  by  a  proper  interstitial  growth, 
in  the  manner  of  the  softer  tissues. — Much  of  our  information  regarding  the 
mode  in  which  new  bony  matter  is  deposited,  is   derived  from  observations 
made  upon  the  bones  of  animals  that  have  been   fed  with  madder ;   for  this 
colon  ring-matter,  having   a  strong  affinity  for  bone-earth,  tinges  all  those  parts 
which  are   in  close  relation  with  the  vascular  surfaces.     In  very  young  ani- 
mals, a   single  day  serves   to  colour  the   entire   substance  of  the  bones ;   for 
there   is  in   them   no  osseous   matter  far  removed   from   a  vascular  surface. 
At  a  later  period,  however,  the  colouring  matter  is  deposited  less  rapidly  ;  and 
is  found  to  be  confined  to  the  innermost  of  the  concentric  laminaa  of  bone, 
surrounding  each   Haversian   canal,  showing  that  this   is   the  last  formed. 
When  madder  is  given  to  a  growing  animal,  the  external  portion  of  the  bone 
is  first  reddened ;   showing  that   the  new  deposit  takes   place   exclusively  in 
that  situation.     And  if,  when  time  has  been  allowed  for  this  part  to  become 
tinged,  the  administration  of  the  madder  be  discontinued,  and  the  animal  be 
killed  some  weeks  afterwards,  the  red  stratum  is   surrounded  by  a  colourless 
one  of  subsequent  formation ;  whilst  the  colourless  layer  internal  to  the  red 
one,  and  formed  previously  to  it,  is  thinned  by  absorption  from  within.     By 
alternately  administering  and  withholding  the  madder,  a  succession  of  coloured 
and  colourless   cylinders   may  thus  be  formed  in  the   shaft  of  a  long  bone ; 
which  present  themselves  as  concentric  rings  in  its  transverse  section. 

203.  The  nature  of  the  Ossifying   process   receives   some  additional  light 
from  the  abnormal  forms  in  which  it  occasionally  presents  itself  in  Cartilages 
that  are  usually  permanent ;  as  well  as  in  various  softer  tissues,  such  as  the 
coats  of  the  arteries,  fibrous  and  serous  membranes,  muscular  substance,  &c. 
In  these  cases,  the  ossific  deposit  may  often  be  seen  to  take  place,  in  the  first 
instance,  in  the  form  of  distinct  granules,  which  gradually  coalesce  ;  or  in  the 
form  of  spicular  fibres,  to  which  additions  are  progressively  made;  until  a 
solid  mass  is  produced.     This  adventitious  bone,  however,  almost  invariably 
differs  from  true  or  normal  bone,  in  the  want  of  a  regular   Haversian  system 


172  ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 

with  concentric  laminae,  and  in  the  absence  of  the  characteristic  lacunae  and 
canaliculi.  Irregular  cavities,  however,  are  scattered  through  them  ;  which 
may  in  some  degree  answer  the  same  purpose.  The  osseous  plates  not  un- 
frequently  found  in  the  dura  mater,  are  stated  by  Mr.  Tomes  to  possess  a 
structure  more  closely  allied  to  that  of  true  bone  ;  which  may  be  connected 
with  the  fact  that,  in  some  of  the  lower  Mammalia,  certain  parts  of  this  mem- 
brane (the  falx  and  tentorium)  are  normally  ossified. 

204.  The  Regeneration  of  Bone,  after  loss  of  its   substance  by  disease  or 
injury,  is  extremely  complete ;  in  fact,  there  is  no  other  structure  of  so  com- 
plex a  nature,  which  is  capable  of  being  so  thoroughly  repaired.     Much  dis- 
cussion has   taken  place  with  respect  to  the  degree  in  which  the   different 
membranous  structures,  that  surround  bone  and  penetrate  its  substance,  con- 
tribute  to  its   regeneration  ;   but  the   fact  seems   to  be,  that  any  or  all  these 
membranes  may  contribute  to  the  formation  ff  new  bone,  in   proportion  to 
their  vascularity, — the  new  structure,  however,  being  most  readily  produced 
in  continuity  with  the  old.     Thus,  when  a  portion  of  the  shaft  of  the  bone 
is  entirely  removed,  but  the  periosteum   is  left,  the   space  is   filled  up  with 
bony  matter  in  the  course  of  a  few  weeks ;  though,  if  the  periosteum  also  be 
removed,  the   formation  of  new  osseous   matter  will   be  confined  to  a  small 
addition  in  a  conical  form  to  the  two  extremities,  a  large  interspace  being  left 
between  them.     The  production  of  new  bony  tissue,  in  this  experiment,  as 
in  cases  where  the  periosteum  has  been  detached  by  disease  and  remains  alive 
while  the   shaft  dies,  is  in  continuity  with  minute   spicula  of  original  bone, 
which  still  adhere  to  the  membrane;  and  it  is  well  known  that,  in  comminuted 
fractures,  every  portion  of  the   shattered  bone,  that  remains  connected  with 
the  vascular  membranes,  whether  these  be  internal  or  external,  becomes  the 
centre  of  a  new  formation ;  the  loss  of  substance  being  filled  up  the  more  ra- 
pidly, in  proportion  to  the  number  of  such  centres. 

205.  The  most  extensive  reparation  is  seen,  when  the  shaft  of  a  long  bone 
is  destroyed  by  disease.     If  violent  inflammation  occur  in  its  tissue,  the  death 
of  the  fabric  is  frequently  the  consequence  ;  apparently  through  the  blocking- 
up  of  the  canals  with  the  products  of  inflammatory  action,  and  the  consequent 
cessation  of  the  supply  of  nutriment.     It  is  not  often  that  the  whole  thickness 
of  the  bone  becomes  necrosed  at  once  ;  more  commonly  this  result  is  confined 
to  its  outer  or  to  its  inner  layers.     When  this  is  the  case,  the  new  formation 
takes  place  from  the  part  that  remains  sound ;  the  external  layers,  which 
receive  their  vascular  supply  from  the  periosteum,  and  from  the  Haversian 
canals  continued  inwards  from  it,  throwing  out  new  matter  on  their  interior, 
which  is  gradually  converted  into  bone ;  whilst  the  internal  layers,  if  they 
should  be  the  parts  remaining  uninjured,  do  the  same  on  their  exterior,  de- 
riving their  materials  from  the  medullary  membrane,  and  from  its  prolonga- 
tions into  their  Haversian  canals.     But  it  sometimes  happens  that  the  whole 
shaft  suffers  necrosis;  and  as  the  medullary  membrane  and  the  entire  Haver- 
sian system  have  lost  their  vitality,  reparation  can  then  only  take  place  from 
the  splinters  of  bone  which  may  remain  attached  to  the  periosteum,  and  from 
the  living  bone  at  the   two  extremities.     This   is  consequently  a  very  slow 
process  ;  more  especially  as  the  epiphyses,  having  been  originally  formed  as 
distinct  parts  from  the  shaft,  do  not  seem  able  to  contribute  much  to  the  re- 
generation of  the  latter. 

206.  When  the  shaft  of  a  long  bone  has  been  fractured  through,  and  the 
extremities  have  been  brought  evenly  together,  it  is  found  that  the  new  matter 
first  ossified  is  that  which  occupies   the   central  portion  of  the  deposit,  and 
which  thus  connects  the  medullary  cavities  of  the  broken  ends,  forming  a  kind 
of  plug  that  enters  each.     This  was  termed  by  Dupuytren,  by  whom  it  was 
first  distinctly  described,  the  provisional  callus,  and  it  is  usually  formed  in 


REPARATION  OF  BONE.  173 

the  course  of  five  or  six  weeks,  or  less,  in  young  persons.  At  that  period, 
however,  the  contiguous  surfaces  of  the  bone  itself  are  not  cemented  by  bony 
union ;  and  the  formation  of  the  permanent  callus  occupies  some  months  ; 
during  which  the  provisional  callus  is  gradually  absorbed,  and  the  continuity 
of  the  medullary  canal  is  thus  restored,  in  the  manner  in  which  it  was  first 
established.  Mr.  Gulliver  has  remarked  that,  when  the  broken  portions  of 
bone  form  an  angle,  there  is  quite  a  distinct  centre  of  ossification  in  the  new 
matter ;  from  which  that  portion  of  it  is  ossified,  that  lies  between  the  sides 
of  the  angle ;  thus  forming  what  has  been  termed  an  accidental  callus,  and 
giving  support  to  the  two  portions  of  the  shaft,  in  a  situation  which  is  exactly 
that^of  the  greatest  mechanical  advantage.  Though  for  some  time  quite  uncon- 
nected with  the  old  bone,  it  soon  becomes  united  to  the  regular  callus.  This 
instance  proves,  that  continuity  with  previously-formed  bone  is  not  absolutely 
requisite  for  the  production  of  new  osseous  structure;  although  the  process 
is  decidedly  favoured  thereby. 

207.  The  reparation  of  Bone,  after  disease  or  injury,  seems  to  take  place 
upon  a  plan  essentially  the  same  as   that  of  its  first  formation.     A  plastic  or 
organizable  exudation  is  first  poured  out  from  the  neighbouring  blood-vessels  ; 
and  thus  forms  a  sort  of  bed  or  matrix,  in  which  the  subsequent  processes 
take  place.     The  next  stage,  in  young  animals,  is  the  formation  of  a  true  car- 
tilaginous substance,  exactly  resembling  their  temporary  cartilages ;  and  this 
is  gradually  converted  into  bone,  in  the  manner  in  which  those  cartilages  are 
consolidated  in  the  first  instance.     In  older  animals,  however,  the  new  struc- 
ture appears  to  be  rather  of  a  membranous  character;  and  the  ossifying  pro- 
cess would  therefore  correspond  rather  with  that  by  which  the  normal  in- 
crease of  their  bones  is  effected.     Mr.  Tomes  states*  that  he  has  examined 
various  cases  of  fracture  of  the  neck  or  shaft  of  the  femur,  in  which  union 
had  not  been  effected,  in  consequence  of  the  patient's  advanced  age;  and  that 
he  found  in  these  no  intervening  cartilage,  and  but  a  scanty  amount  of  con- 
densed areolar  tissue.     In  this  latter,  traces  of  an  attempt  at  repair  may  be 
generally  found,  in  the  presence  of  osseous  matter  in  granules  or  granular 
masses ;  but  in  these  there  is  no  arrangement  of  tubes  or  bone-cells  of  definite 
character ;  indeed,  such  osseous  masses  are  generally  small,  and  are  deficient 
in  density,  owing  to  the  want  of  union  between  the  individual  granules. 

208.  The  Teeth  are  nearly  allied  to  Bone  in  structure  ;  and  in  some  of  the 
lower  Vertebrata,  there  is  an  actual  continuity  between  the  bone  of  the  jaw, 
and  the  teeth  projecting  from   it,  notwithstanding  that  the  latter  form  part  of 
the  dermal  skeleton,  whilst  the  former  belongs  to  the  neural  or  internal.     In 
Man  and  the  higher  animals,  however,  there  is  an  obvious  difference  in  their 
structure  ;  as  in  their  mode  of  development.     These  subjects  have  lately  re- 
ceived much  attention;  and  the  practical  importance  of  an  acquaintance  with 
them,  renders  it  desirable  that  they  should  be  here  treated  somewhat  fully. — 
The  Teeth  of  Man,  and  of  most  of  the  higher. animals,  are  composed  of  three 
very  different  substances ;  Dentine  (known  as  ivory  in  the  tusk  of  the  Ele- 
phant), Enamel  and  Cementum  or  Crusta  Petrosa.     These  are  disposed  in 
various  methods,  according  to   the  purpose  which  the  Tooth  is  to  serve :  in 
Man,  the  whole  of  the  crown  of  the  tooth  is  covered  with  Enamel ;  its  root  or 
fang  is  covered  with  Cementum;  whilst  the  substance  or  body  of  the  tooth  is 
composed  of  Dentine.     In  the  molar  Teeth  of  many  Herbivorous  animals, 
however,  the  Enamel  and  Cementum  form  vertical  plates,  which   alternate 
with  plates  of  Dentine,  and  present  their  edges  at  the  grinding  surface  of  the 
tooth ;  and  the  unequal  wear  of  these  substances, — the  Enamel  being  the 
hardest,  and  the  Cementum  the  softest, — occasions  this  surface  to  be  always 
kept  rough. 

*  Cyclopaedia  of  Anatomy  and  Physiology,  vol.  iii.,  p.  857. 
15* 


174 


ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABUIC. 

[Fig.  69.  [Fig>  7a 


A  view  of  an  Incisor  and  of  a  Molar  Tooth, 
given  by  a  longitudinal  section,  and  showing 
that  the  enamel  is  striated,  and  that  the  strise 
are  all  turned  to  the  centre;  the  internal 
structure  is  also  seen ;  1,  the  enamel ;  2,  the 
ivory  ;  3,  the  cavitas  pulpi.] 


209.  The  Enamel  is  composed 
an  inch  in  diameter,  arranged  side 

[Fig.  71. 


A  vertical  section  of  an  adult  Bicuspid,  cut  from 
without  inwards— magnified  4  times ;  1, 1,  the  cor- 
tical substance  which  surrounds  the  root  up  to  the 
commencement  of  the  enamel ;  2,  2,  the  ivory  of 
the  tooth,  in  which  are  seen  the  greater  parallel 
curvatures,  as  well  as  the  position  of  the  main 
tubes;  3,  apex  of  the  tooth,  where  the  tubes  are  al- 
most perpendicular ;  4, 4,  the  enamel ;  5,  the  cavity 
of  the  pulp,  in  which  are  seen,  by  means  of  the 
glass,  the  openings  of  the  tubes  of  the  dental  bone.] 

of  solid  prisms  or  fibres,  about  l-5600th  of 
by  side,  and  closely  adherent  to  each  other ; 


[Fig.  72. 


A  vertical  section  of  an  imperfectly  developed  Incisor, 
taken  from  the  follicle  in  which  it  was  enclosed;  this 
section  is  meant  to  show  the  position  of  the  enamel 
fibres,  and  also  that  a  part  of  the  appearances  which  are 
seen  in  this  substance  under  a  less  magnifying  power, 
originate  in  parallel  curvatures  of  the  fibres ;  1, 1,  the 
enamel ;  2,  2,  the  dental  bone,  or  ivory;  3,  3,  the  minute 
indentations  and  points  on  the  surface  of  the  ivory,  on 
which  the  enamel  fibres  rest ;  4,  4,  brown  parallel  fibres; 
5,  parallel  flexions  of  the  fibres  of  the  dental  bone  in  these 
stripes  ] 


A  portion  of  the  surface  of  the  Enamel 
on  which  the  hexagonal  terminations 
of  the  fibres  are  shown — highly  magni- 
fied ;  1,  2,  3,  are  more  strongly  marked 
dark  crooked  crevices, — running  be- 
tween the  rows  of  the  hexagonal 
fibres.] 


STRUCTURE  OF  TEETH;    ENAMEL,  DENTINE, 


175 


their  length  corresponds  with  the  thickness  of  the  layer  which  they  form ; 
and  the  two  surfaces  of  this  layer  present  the  ends  of  the  prisms,  which  are 
usually  more  or  less  regularly  hexagonal.  The  course  of  these  prisms  is 
generally  wavy ;  but  their  curves  are  for  the  most  part  parallel  to  each  other. 
In  the  perfect  state,  the  Enamel  contains  but  an  extremely  minute  quantity  of 
animal  matter ;  but  if  a  young  tooth  be  examined,  it  is  found  that,  after  the 


[Fig.  73. 


[Fig.  74. 


The  Fibres  of  the  Enamel  viewed  sideways  A  small  portion  of  fig.  70  covered  with  turpentine 

under  a  magnifying  power  of  350  times;  1,1,  varnish,  viewed  under  a  magnifying  power  of  350 

the  enamel  fibres  ;  2,  2,  the  transverse  stripes  times;  1.  2,  3,  are  the  tubes  containing  a  powdery, 

upon  them.]  lumpy  substance.  They  are  regular,  and  closely  un- 

•     dulating;  but  the  branches  do  not  appear,  because 
they  are  penetrated  by  the  varnish.] 

calcareous  matter  of  the  tooth  has  been  dissolved  away  by  an  acid,  there  re- 
mains a  set  of  distinct  prismatic  cells,  which  formed  (as  it  were)  the  moulds 
in  which  the  mineral  substance  was  deposited.*  The  Enamel  is  the  least 
constant  of  the  dental  tissues  ;  being  more  frequently  absent  than  present  in 
the  teeth  of  Fishes  ;  being  deficient  in  the  whole  order  of  Serpents ;  and  form- 
ing no  part  of  the  teeth  of  the  Edentate  and  Cetacean  Mammals. 

210.  The  Dentine}  consists  of  a  firm  substance,  in  which  mineral  matter 
largely  predominates,  though  to  a  less  degree  than  in  the  enamel.     It  is  tra- 

[Fig.  75.  [Fig.  76. 


A  view  of  the  most  interior  portion  of  the  main 
tubes  of  the  dental  bone  in  an  incisor  of  a  child 
two  years  old,  close  to  their  commencement  in  the 
cavitas  pulpi,  in  order  to  show  their  first  division.] 


A  view  of  the  external  portion  of  the  tubes  of 
the  same  tooth,  exhibiting  their  more  minute  ra- 
mifications, which,  for  the  most  part,  turn  towards 
the  crown.] 


versed  by  a  vast  number  of  very  fine  cylindrical  branching  wavy  tubuli ;  which 

*  The  Author  has  discovered  a  structure  precisely  resembling  this,  in  the  shells  of  many 
Mollusca.  See  Annals  of  Natural  History,  December,  1 843. 

t  A  structure  exactly  resembling  Dentine  has  been  found  by  the  Author  in  the  shell  of 
the  Crab,  especially  at  the  tips  of  the  claws;  and  a  less  regular  structure  of  the  same  kind 
in  the  shells  of  many  Mollusca.  (Loc.  cit.) 


176 


ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 


commence  at  the  pulp-cavity  (on  whose  wall  their  openings  may  be  seen), 
and  radiate  towards  the  surface.  In  their  course  outwards,  the  tubuli  occa- 
sionally divide  dichotomously  ;  and  they  frequently  give  off  minute  branches, 
which  again  send  off  smaller  ones.  In  some  animals,  these  tubuli  may  be 
traced  at  their  extremities  into  cells  exactly  resembling  the  lacuna?  of  bone; 
and  here  the  Ivory  must  be  considered  as  presenting  a  form  of  transition  into 


[Fig.  77. 


[Fig.  78. 


A  view  of  a  small  portion  of  a  transverse  section  of 
the  crown  of  the  Tooth  seen  in  fig.  70,  viewed  under  a 
magnifying  power  of  350  times  ;  1,  2,  3,  are  the  round 
openings  of  the  tubes,  with  parietes  of  a  peculiar  sub- 
stance ;  4,  5,  6,  are  the  tubes  cut  more  obliquely,  in 
consequence  of  their  more  external  position  ] 


A  view  of  the  position  of  the  same  main 
tubes,  in  a  transverse  section  near  the  root 
of  a  bicuspid,  magnified  5  diameters.  The 
dark  patches  in  this  figure  mark  the  places 
in  which  the  bone  was  especially  white  and 
less  transparent  than  in  the  clear  interme- 
diate tracts.] 


[Fig.  79. 


Sections  of  a  human  incisor,  showing: — 

A.  Junction  of  dentine  and  enamel  near  the  neck  of  the  tooth,    a.  Tubes  of  the  dentine,  dividing  and 
ending  on  b  b,  the  cupped  surface  on  which  the  enamel  rods  vertically  rest.    c.  Free  surface  of  the  ena- 
mel.   The  enamel  rods  are  crossed  by  transverse  lines  and  also  by  oblique  dark  lines. 

B.  Bifurcation  of  the  tubuli  of  the  dentine,  soon  after  their  commencement  on  d  the  surface  of  the  pulp- 
cavity. 

c.  Branching  of  the  tubuli  of  the  fang,  and  their  termination  in  the  small  irregular  lacunae  of  the  "  gra- 
nular layer." 

In  these  longitudinal  views  of  the  tubuli,  their  cavities  only,  and  not  their  walls,  are  visible. 
Magnified  300  diameters.] 


STRUCTURE  OF  TEETH;    ENAMEL,  DENTINE. 


177 


the  substance  next  to  be  described.  The  tubuli,  in  their  radiating  course,  de- 
scribe two,  three,  or  more  curvatures,  appreciable  by  a  low  magnifying  power; 
these  are  termed  by  Prof.  Owen,  the  "  primary  curvatures."  With  a  higher 
power,  the  tubes  are  seen  to  be  bent,  throughout  the  whole  of  their  flexuous 
course,  into  minute  and  equal  oblique  undulations,  of.  which  100  may  be 
counted  within  the  space  of  l-10th  of  an  inch  ;  these  are  the  "  secondary  cur- 
vatures" of  Prof.  Owen.  Both  the  primary  and  the  secondary  curvatures  of 
one  tube  are  usually  parallel  with  those  of  the  contiguous  tubes  ;  and  from 
the  radiating  course  of  the  tubuli,  the  rows  of  curvatures  have  the  appearance 
of  lines  running  parallel  with  the  external  contour  of  the  tooth. — The  dia- 
meter of  the  tubuli  in  their  largest  part  averages  about  1-1 0,000th  of  an  inch  ; 
their  smallest  branches  are  immeasurably  fine.  It  is  impossible  that  they 
can  receive  blood;  but  it  may  be  surmised  that,  like  the  canaliculi  of  bone, 
they  absorb  matter  from  the  vascular  lining  of  the  pulp-cavity,  which  aids  in 
the  nutrition  of  the  tooth.  Although,  when  once  fully  formed,  the  Tooth  un- 
dergoes little  or  no  change,  there  is  evidence  that  it  possesses  a  certain  power 
of  repairing  the  effects  of  disease ; — a  new  layer  of  hard  matter  being  some- 
times thrown  out  on  a  surface,  which  has  been  laid  bare  by  Caries.  It  has 
been  found,  too,  that  the  Dentine  is  sometimes  tinged  by  colouring*  matters 
contained  in  the  blood.  This  is  most  evident,  when  a  young  animal  is  fed 
upon  madder,  during  the  period  of  the  formation  of  the  tooth ;  but  even  in  an 
adult,  some  tinge  will  result  from  a  prolonged  use  of  this  substance ;  and  it 
has  been  noticed  that  the  teeth  of  persons,  who  have  long  suffered  from  Jaun- 


[Fig.  80. 


Fig.  81. 


Transverse  sections  of  tubules  of  dentine, 
showing  their  cavities,  their  walls,  and  the 
intertubular  tissue. 

a.  Ordinary  distance  apart. 

b.  More  crowded. 
e.  Another  view. 

Human  molar.— Magnified  400  diameters.] 


Oblique  section  of  Dentine  of  human 
tooth,  highly  magnified,  showing  the  calci- 
gerous  tubuli,  and  the  outlines  of  the  original 
cells. 


dice,  sometimes  acquire  a  tinge  of  bile.     Attention  has  been  particularly  di- 
rected by  Prof.  Owen,  to  appearances   which  he  regards  as  indicating  the 


178  ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 

boundaries  of  the  original  cells  of  the  dentinal  pulp  (§213)  that  have  not  been 
obliterated  by  the  process  of  calcification.*  These  are  particularly  evident 
in  the  teeth  of  the  Dugong,  and  of  the  extinct  Mylodon;  but  they  occasionally 
present  themselves  in  the  Dentine  of  Man  (Fig.  81). — In  certain  Mammals 
and  Reptiles,  and  in  a  large  number  of  Fishes,  the  Dentine  is  traversed  by 
canals,  which  are  prolonged  into  it  from  the  central  pulp-cavity,  and  which 
are  lined  (like  the  pulp-cavity  itself)  by  a  highly-vascular  membrane ;  and  it 
is  then  distinguished  as  Vascular  Dentine.  These  canals  are  obviously  ana- 
logous to  the  medullary  or  Haversian  canals  of  bone  ;  and  the  tubuli  usually 
radiate  from  them,  rather  than  from  the  central  cavity.  In  some  instances, 
there  is  no  central  cavity  whatever  ;  but  the  whole  tooth  is  traversed  by  an 
irregular  network  of  these  medullary  canals,  which  become  continuous  with 
the  Haversian  canals  of  the  subjacent  bone. — A  substance  still  more  resem- 
bling bone,  but  formed  from  the  dentinal  pulp,  is  found  in  the  interior  of  the 
teeth  of  certain  Reptiles  and  Mammalia,  and  occasionally  in  the  teeth  of 
Man,  especially  at  the  later  periods  of  life.  This  substance  possesses  not 
only  vascular  or  medullary  canals,  but  also  the  stellate  lacunre  and  radiating 
canaliculi  of  true  bone.  It  sometimes  occupies  the  whole  of  the  cavity  of  the 
pulp,  and  is  formed  by  the  ossification  of  its  cellular  parenchyma ;  but  in 
other  cases,  it  forms  merely  a  thin  shell  upon  the  interior  of  the  ordinary 
Dentine. 

211.  The  Cementutn  or  Crusta  Petrosa  corresponds  in  all  essential  parti- 
culars with  Bone ;  possessing  its  characteristic  lacunae ;  and  being  also  tra- 
versed by  vascular  medullary  canals,  wherever  it  occurs  of  sufficient  thickness, 
— as  in  the  exterior  of  the  tooth  of  the  extinct  Megatherium,  and  in  the  thick 
plates  interposed  within  the  islands  of  Enamel  in  the  teQth  of  Ruminants,  Ro- 
dents, &c.     The  varieties  of  microscopic  structure  presented  by  the  Cemen- 
tum  in  different  classes  of  animals,  correspond  with  the  modifications  of  the 
osseous  tissue,  which  exist  in  the  skeletons  of  those  animals   respectively. 
The  Cementum  was   formerly  supposed  to  be  restricted  to  the  compound 
teeth  of  Herbivorous  animals  ;  and  its  presence  in  the  simple  teeth  of  Man 
and  the  Carnivora  can  be  shown  only  by  the  application  of  the  Microscope. 
In  the  latter  it  forms  a  layer,  which  invests  the  fang,  and  which  decreases  in 
thickness  as  it  approaches  the  crown  of  the  tooth ;  at  the  time  of  the  first 
emersion  of  the  tooth,  it  covers  the  crown  with  a  very  thin  lamina  ;  but  this 
is  speedily  worn  away  by  use ;  on  the  other  hand,  its  thickness  around  the 
apex  of  the  fang  often  undergoes  a  subsequent  increase,  especially  when  chro- 
nic inflammation  and  thickening  take  place  in  the  membranous  contents  of  the 
socket.  • 

212.  The  following  are  the  results  of  the  most  recent  Chemical  Analyses 
of  the  component  structures  of  Human  Teeth : — t 

.  Incisors  of  Adult  Man. 

Dentine.         Enamel.  Cementum. 

Organic  matter         .         .         .       28-70  3-59  29-27 

Earthy  matter  .         .  71-30  96-41  70-73 

100-00  100-00  100-00 

The  proportion  of  these  two  components  varies  considerably  in  different  species;  thus  the 
organic  basis  of  the  Elephant's  tusk  forms  as  much  as  43  per  cent,  of  the  whole.  It  would 
seem  even  to  vary  considerably  in  different  individuals  of  the  same  species :  thus  in  the 
molar  teeth  of  one  man,Bibra  found,  the  organic  matter  to  constitute  as  little  as  21  per  cent., 

*  See  Prof.  Owen's  Odontography,  Introduction. 

f  Op.  Cit. ;  and  Bibra's  "  Chemische  Untersnchungen  xiber  die  Knochen  und  Ziihne." 


COMPOSITION  AND  DEVELOPMENT  OF  TEETH.  179 

whilst  in  another  it  was  28. — The  following  analyses  afford  a  more  particular  view  of  the 
components  of  each  substance : — 

Molars  of  Mult  Man. 

Dentine.  Enamel. 

Phosphate  of  Lime,  with  traces  of  fluate  of  lime         .  66-72  89'82 

Carbonate  of  Lime 3-36  437 

Phosphate  of  Magnesia 1 08  1-34 

Other  Salts O83  OSS 

Chondrine           .         .     ,     .     - 27-61  339 

Fat 0-40  020 

lOO'OO  100-00 

Incisors  of  Ox. 

Dentine.  Enamel.  Cement. 
Phosphate  of  Lime,  with  trace  of  fluate 

of  lime 59-57  81-86  58-73 

Carbonate  of  Lime             .         .         .             7-00  9-33                7-22 

Phosphate  of  Magnesia          .         .         .099  1-20               0-99 

Salts 0-91  0-93               0-82 

Chondrine              30-71  6-66  31-31 

Fat '    .            0-82  0-02               0'93 

100-00  100-00  100-00 

213.  The  Dentine  and  its  modifications,  the  Enamel,  and  the  Cementum, 
originate  in  three  distinct  structures ;  which  may  be  termed  respectively,  the 
dentinal-pulp,  the  enamel-pulp,  and  the  capsule  or  cemental-pulp ;  the  whole 
forming  the  "  matrix'*  from  which  the  entire  tooth  is  evolved. — The  Dentinal 
pulp  is  always  the  first-developed  part  of  the  matrix  ;  and  it  makes  its  appear- 
ance in  the  form  of  a  papilla,  budding  out  from  the  free  surface  of  a  fold  or 
groove  of  the  mucous  membrane  of  the  mouth.  This  may  be  converted  into 
dentine,  without  ever  becoming  inclosed  within  .a  capsule;  as  we  see  in  the 
Shark,  whose  dentition  never  advances  beyond  this  papillary  stage.  The 
dentinal  pulp  consists  of  a  mass  of  nucleated  cells,  imbedded  in  a  semi-fluid 
granular  blastema,  and  the  whole  inclosed  in  a  dense  structureless  pellucid 
membrane.  This  substance  is  copiously  supplied  with  blood-vessels,  origin- 
ating in  a  trunk  that  enters  the  base  of  each  papilla;  the  branches  ramify  and 
diverge  in  their  progress  through  the  pulp ;  and  at  last  they  form  a  capillary 
network,  which  terminates  in  loops  near  the  apex  of  the  pulp  (Fig.  82). 
These  vessels  are  accompanied  by  nerves;  which  also  have  looped  termina- 
tions.— The  following  is  the  substance  of  the  account  given  by  Prof.  Owen, 
of  the  conversion  of  the  dentinal  pulp  into  dentine ;  based  upon  his  observa- 
tion of  this  process  as  it  occurs  in  the  foetal  Shark.  The  primary  cells,  which 
are  smallest  at  the  base  of  the  pulp,  and  have  large  simple  sub-granular  nuclei, 
soon  fall  into  linear  series,  directed  towards  the  periphery  of  the  pulp  ;  and 
those  which  are  nearest  to  the  periphery  become  closely  aggregated,  increase 
in  size,  and  present  a  series  of  important  changes  in  their  interior  (Fig.  83,  a). 
A  pellucid  point  appears  in  the  centre  of  the  nucleus  ;  and  the  latter  increases 
in  size,  and  becomes  more  opaque  around  it.  A  division  of  the  nucleus  in 
the  course  of  its  long  axis  is  next  observed  (6) ;  and  in  the  larger  and  more 
elongated  cells,  still  nearer  the  periphery  of  the  pulp,  a  further  subdivision  of 
the  nuclei  is  observed,  in  a  transverse  as  well  as  a  longitudinal  direction  (e*  c), 
the  subdivisions  becoming  elongated,  with  their  long  axes  vertical,  or  nearly 
so,  to  the  surface  of  the  pulp.  The  subdivided  and  elongated  nuclei  become 
attached  by  their  extremities  to  the  corresponding  nuclei  of  the  cells  in  ad- 
vance; and  the  attached  extremities  become  confluent  (</);  so  that  lines  or 


180  ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 

Fig.  82.  Fig.  83. 

f 


OOD 


Vessels  of  Dental  Papilla. 

files  of  nuclear  matter  are  formed,  which 
present  an  unbroken  continuity  from 
one  primary  cell  to  another.  While 
these  changes  are  proceeding,  the  cal- 
careous salts  furnished  by  the  blood 
begin  to  be  accumulated  in  the  interior 
of  the  cells,  and  to  be  aggregated  in  a 
semi-transparent  state  around  the  cen- 
tral granular  part  of  the  elongated  nu- 
clei, which  now  present  the  character 
of  rows  of  minute  secondary  cells ;  and 
the  salts  occupy,  in  a  still  clearer  and 
more  compact  state,  the  cavity  of  the 
primary  cell  not  occupied  by  the  trans- 
formed nuclei.  The  rows  of  minute 
secondary  cells  (which  appear  scarcely 
to  advance  beyond  the  condition  of 
simple  granules)  remain  uncalcified  in 
the  midst  of  the  solid  calcareous  sub- 
stance ;  and  thus  constitute  the  tubuli 
of  the  dentine,  in  which  a  granular  or 
bead-like  aspect  may  generally  be  traced. 

214.  Around  the  tubes,  in  a  transverse  section,  is  a  small  circular  space 
(Fig.  84,  6,)  manifestly  distinct  from  the  intertubular  substance;  and  this  is 
regarded  by  Professor  Owen  as  the  indication  of  a  membrane  surrounding 
the  elongated  and  coalesced  secondary  cells.  The  traces  of  the  original 
boundary  of  the  primary  or  parent-cells  (Fig.  84,  a,  a),  are  generally  lost; 
but,  as  already  remarked  (§210)  they  are  sometimes  preserved  with  suffi- 
cient distinctness  to  be  quite  recognizable.  The  "  primary  curvatures"  ob- 
servable in  the  tubuli  are  due  to  the  arrangement  of  the  original  linear  series 


Diagram  of  development  of  Dentine  ;  a,  end 
of  a  linear  series  of  primary  dentinal  cells;  6, 
cells  with  nuclei  dividing;  c,  subdivision  and 
elongation  of  nuclear  matter;  d,  elongated 
nuclei  uniting  to  form  the  areee  of  dentinal 
tubes;  e,  e,  calcified  cap  of  dentine,  formed  by 
the  mtus-susception  of  the  clear  hardening 
salts  into  the  walls  and  cavities  of  the  cells 
and  intercellular  blastema  i,  e,  and  by  their 
partial  exclusion  from  the  moniliform  nuclear 
tracts/"  f;  g-,  union  of  two  peripheral  nucle- 
olar  or  secondary  cells  with  one  nearer  the 
centre  of  the  pulp. 


DEVELOPMENT  OF  DENTINE. 


181 


•0 
SKI 


m 

Inner  surface  of  portion  of  calcified  dentinal  pulp, 
forming  cap  of  dentine ;  a,  intervals  and  walls  of  pri- 
mary dentinal  cells  ;  6,  walls  of  dentinal  tubes ;  c,  nu- 
clear matter,  establishing  areas  of  dentinal  tubes. 
For  clearer  demonstration,  the  number  of  tubes  iu 
the  area  of  each  cell  is  made  less  than  in  nature. 


of  parent  cells ;  whilst  the  "  se- 
condary curvatures"  are  accounted  for 
by  the  fact,  that  the  elongated  nuclei 
usually  unite  with  each  other  at  ob- 
tuse angles,  and  not  in  perfectly  straight 
lines,  (Fig.  83,  d.) — Thus  we  are  to 
regard  the  Dentine  as  composed  of  the 
original  cells  of  the  pulp,  which  have 
become  consolidated  by  the  calcifying 
process,  in  every  part  save  that  which 
is  occupied  by  the  rows  of  granules 
or  incipient  cells,  developed  from  the 
metamorphosed  nuclei.  The  calca- 
reous matter  appears  to  be  chemically 
united,  as  in  Bone,  with  an  animal 
base;  the  cavity  of  each  cell  being 
pervaded  by  both ;  so  that,  when  the 
whole  of  the  calcareous  matter  is  re- 
moved by  dilute  acid,  a  cartilaginous- 
looking  mass  remains,  which  preserves 
the  form  of  the  tooth.  The  calcifying  process  takes  place  first  on  the  exterior 
of  the  pulp,  and  gradually  extends  inwards  ;  and  the  capillary  blood-vessels  alto- 
gether retreat  from  the  calcifying  portion,  and  form  their  terminal  loops  upon 
the  surface  of  the  part  which  still  remains  unconsolidated.  As  the  calcifica- 
tion extends  inwards,  the  pulp,  of  course,  progressively  decreases ;  fewer 
nuclei  are  formed  in  the  cells  ;  and  these  do  not  acquire  so  large  a  size.  Here 
and  there  it  is  seen,  that  the  inner  extremities  of  two  of  the  granular  tracts, 
in  the  part  last  calcified,  converge,  and  connect  themselves  with  a  single  tract 
in  the  layer  nearer  the  centre  of  the  pulp,  (Fig.  83,  g) ;  in  which  we  see  the 
origin  of  the  bifurcation  of  the  tubuli.  This  bifurcation  becomes  more  fre- 
quent, as  the  calcifying  process  approximates  towards  the  centre  and  base  of 
the  pulp  ;  and  it  is  thus  that  the  main  tubes  are  formed.  In  some  of  the  cells, 
at  and  near  the  central  and  basal  part  of  the  pulp,  the  nucleus  undergoes  no 
division  ;  but  it  merely  elongates,  and  sometimes  becomes  angular  or  radiated, 
— thus  showing  a  form  of  transition  to  the  stellate  nucleus  of  the  bone-cells. 
As  already  stated,  we  occasionally  find  modifications  of  the  dentine  in  this 
situation,  which  closely  resemble  true  bone  in  structure. 

215.  The  Enamel-pulp  is  not  formed  until  after  the  dental  papilla  has 
become  inclosed  in  a  capsule,  by  the  process  to  be  presently  described  (§  217, 
c).  It  differs  from  the  dentinal  pulp,  at  its  first  formation,  in  the  more  fluid 
state  of  its  blastema  ;  and  in  containing  fewer  and  more  minute  cells.  The 
enamel-pulp  is  derived  from  the  free  inner  surface  of  the  capsule ;  of  which 
we  may  regard  its  cells  as  the  epithelium.  The  cells  are  largest  and  most 
numerous  in  that  portion  of  the  pulp  which  most  nearly  approaches  the  den- 
tal papilla ;  and  many  of  them  show  a  nuclear  spot  (Fig.  85,  /«,  h).  In  the 
portion  of  the  enamel-pulp  most  distant  from  the  capsule,  the  cells,  at  first 
spherical,  become  impacted  against  one  another,  and  are  pressed  into  hexago- 
nal or  polygonal  forms  (i,  i) ;  the  fluid  blastema  being  now  almost  excluded  from 
between  them.  In  the  part  in  closest  contiguity  with  the  surface  of  the  den- 
tinal pulp,  the  cells  increase  in  length,  either  by  the  elongation  of  each  indi- 
vidual cell,  or  by  the  coalescence  of  several  (j) ;  the  nuclei  (k)  disappear ;  and 
the  cells,  now  forming  long  prisms  (/),  absorb  into  themselves  calcareous  salts, 
which  henceforth  completely  fill  them,  in  a  clear  and  crystalline  form.  These 
salts  would  not  seem  to  be  united,  as  in  bone  and  dentine,  with  any  organic 
matters;  the  small  quantity  of  this  existing  in  Enamel,  being  probably  em- 


182  ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC, 

Fig.  85.  Fig.  86. 


Formation  of  the  Cementum  ;  m,  primary  cells ;  p,  their 
granular  nuclei;  n,  more  minutely  granular  blastema;  o,  the 
primary  cell  enlarged,  and  receiving  the  hardening  salts  ;  n' ' 
calcined  blastema;  P')P',  stellate  nuclei  of  fully-formed  ce- 
mental  cells. 

ployed  wholly  in  forming  the  walls  of  the  pris- 
matic cells.  The  disappearance  of  the  nucleus, 
previously  to  the  calcification  of  the  cell,  is 
evidently  the  reason  of  the  absence  of  any 
permanent  space  or  tube  in  its  interior  unoccu- 
pied by  mineral  matter.  The  islands  of  Ena- 
mel, which  are  found  in  the  midst  of  the  dentine, 
in  the  compound  teeth  of  Herbivorous  animals, 
are  formed  from  extensions  of  the  same  ena- 
mel-pulp, with  that  which  gives  origin  to  the 
general  envelope  of  the  tooth  (§  217,  c). 

216.  The  "Cemental  pulp,"  or  matrix  of 
the  Crusta  Petrosa,  is  in  fact  nothing  else  than 
the  capsule  itself;  in  which,  at  an  early  period, 
nucleated  cells  are  found,  distributed  in  the 
midst  of  a  granular  blastema,  which  is  copi- 
ously supplied  by  vessels.  The  process  of 
calcification  begins  in  the  portion  nearest  the 
dentine ;  and  consists,  as  elsewhere,  in  the 
absorption  of  calcareous  matter  into  the  cavi- 
ties of  the  cells,  in  the  more  close  aggregation 
of  the  cells  with  each  other,  and  in  the  changes  which  take  place  coincidently 
in  their  nuclei.  These,  which  are  at  first  large  granular  spots  of  a  rounded 
form,  send  out  radiating  prolongations,  which  extend  quite  to  the  borders  of 
the  cell;  and  as  the  calcareous  salts  which  penetrate  the  cell,  are  not  depo- 
sited in  the  space  occupied  by  the  nuclei,  the  stellate  cavities,  or  lacunae  and 
diverging  canaliculi,  are  left,  which  are  so  analogous  to  those  of  bone,  as  to 
serve  to  identify  the  two  tissues.  In  the  cementum,  as  in  Bone  and  Dentine, 
the  consolidating  substance  appears  to  consist  of  mineral  and  organic  matter 
in  a  state  of  chemical  union.  The  boundaries  of  the  original  cells  usually 
disappear  in  this,  as  in  similar  cases  ;  so  that  nothing  remains  in  the  fully- 
formed  cementum,  to  mark  its  cellular  origin,  save  the  stellate  lacuna  which 
represent  the  positions  of  the  formerly-existing  nuclei. 


Formation  of  Enamel ;  h.  primary 
cells  suspended  in  fluid  blastema g; 
t,  the  same  more  fully  developed  and 
become  angular;  ./,  the  same  be- 
coming prismatic ;  fc,  the  nucleus 
disappearing;  J,  the  modified  pris- 
matic cells,  filled  with  calcareous 
salts,  forming  the  spicula  and  fibres 
of  enamel. 


DEVELOPMENT  OF  THE  TEETH. 


183 


217.  As  it  is  of  much  practical  importance  to  understand  the  origin  of  the 
several  kinds  of  Human  Teeth,  and  the  times  of  their  appearance,  some  de- 
tails upon  these  subjects  will  be  given  ;  those  which  relate  to  the  mode  of  de- 
velopment being  principally  derived  from  the  researches  of  Mr.  J.  Goodsir.* 

a.  At  the  sixth  week  of  Foetal  life,  a  deep  narrow  groove  may  be  perceived,  in  the  upper 
jaw  of  the  Human  embryo,  between  the  lip  and  the  rudimentary  palate;  this  is  speedily 
divided  into  two  by  a  ridge,  which  afterwards  becomes  the  external  alveolar  process ;  and 
it  is  in  the  inner  groove,  that  the  germs  of  the  teeth  subsequently  appear.  Hence  this  may 
be  termed  the  primitive  dental  groove.  At  about  the  seventh  week,  an  ovoidal  papilla, 
consisting  of  a  granular  substance,  makes  its  appearance  on  the  floor  of  the  groove,  near 
its  posterior  termination ;  this  papilla  is  the  germ  of  the  Anterior  superior  Milk  Molar 
tooth.  About  the  eighth  week,  a  similar  papilla,  which  is  the  germ  of  the  Canine  tooth, 
arises  in  front  of  this;  and  during  the  ninth  week  the  germs  of  the  Incisors  make  their  ap- 
pearance under  the  same  form.  During  the  tenth  week,  processes  from  the  sides  of  the 
dental  groove,  particularly  the  external  one,  approach  each  other,  and  finally  meet  before 
and  behind  the  papilla  of  the  anterior  Molar ;  so  as  to  inclose  it  in  a  follicle,  through  the 
mouth  of  which  it  may  be  seen.  By  a  similar  process,  the 
other  teeth  are  gradually  inclosed  in  corresponding  follicles. 
The  germ  of  the  Posterior  milk  Molar  also  appears  during 
the  tenth  week,  as  a  small  papilla.  By  the  thirteenth  week, 
the  follicle  of  the  Posterior  Molar  is  completed ;  and  the 
several  papillae  undergo  a  gradual  change  of  form.  Instead 
of  remaining,  as  hitherto,  simple,  rounded,  blunt  masses  of 
granular  matter,  each  of  them  assumes  a  particular  shape ; 
the  Incisors  acquire  in  some  degree  the  form  of  the  future 
teeth ;  the  Canines  become  simple  cones ;  and  the  Molars 
become  cones  flattened  transversely,  somewhat  similar  to 
carnivorous  molars.  During  this  period,  the  papillae  grow 
faster  than  the  follicles ;  so  that  the  former  protrude  from 
the  mouth  of  the  latter.  At  this  time,  the  mouths  of  the 
follicles  undergo  a  change,  consisting  in  the  development  of 
their  edges,  so  as  to  form  Opercula;  which  correspond  in 
some  measure  with  the  shape  of  the  crowns  of  the  future 
teeth.  There  are  two  of  these  opercula  in  the  Incisive  follicles,  three  for  the  Canines,  and 

Fig.  88. 


Fig.  87. 


Upper  jaw  of  human  embryo 
at  6th  week  ;  showing  b,  the  primi- 
tive Dental  Groove,  behind  a,  the 
Lip. 


Diagrams  illustrative  of  the  formation  of  a  Temporary,  and  its  corresponding  Permanent  Tooth,  from 

a  Mucous  Membrane. 

four  or  five  for  the  Molars.     At  the  fourteenth  week,  the  inner  lip  of  the  dental  groove  has 
increased  so  much,  as  to  meet  and  apply  itself  in  a  valvular  manner  to  the  outer  lip  or 


Edin.  Med.  and  Surg.  Journal,  vol.  li. 


184 


ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 


ridge,  which  has  been  also  increasing.  The  follicles  at  this  time  grow  faster  than  the  pa- 
pilla?, so  that  the  latter  recede  into  the  former.  The  primitive  dental  groove  then  contains 
ten  papilla-,  inclosed  in  as  many  follicles;  and  thus  all  necessary  provision  is  made  for  the 
production  of  the  first  set  of  teeth.  (This  series  of  changes  is  represented  in  Fig.  88,  a — g.) 
The  groove  is  now  situated,  however,  on  a  higher  level  than  at  first 5  and  it  has  undergone 
such  a  change  by  the  closure  of  its  edges,  as  to  entitle  it  to  the  distinctive  appellation  of 
secondary  dental  groove.  It  is  in  this  secondary  groove  that  those  structures  originate,  which 
are  destined  for  the  development  of  the  Second  or  Permanent  set  of  Teeth, — of  those  at 
least  which  replace  the  Milk  Teeth.  This  is  accomplished  in  the  following  manner. 

b.  At  about  the  fourteenth  or  fifteenth  week,  a  little  crescentic  depression  may  be  observed, 
immediately  behind  the  inner  Opercula  of  each  of  the  Milk-tooth  follicles.     This  depres- 
sion  gradually  becomes  deeper,  and.  constitutes  what  maybe  termed  a  cavity  of  reserve  ; 
adapted  to  furnish  delicate  mucous  membrane,  for  the  future  formation  of  the  sacs  and  pulps 
of  the  ten   anterior  Permanent  teeth.     These  cavities  of  reserve  are   gradually  separated 
from  the  secondary  dental  groove,  by  the  adhesion  of  their  edges;  and  they  thus  become 
minute  compressed  sacs,  situated  between  the  surface  of  the  gum  and  the  milk-sacs.     They 
gradually  recede,  however,  from  the  surface  of  the  gum,  so  as  to  be  posterior  instead  of  in- 
ferior to  the  milk  sacs;  and  at  last  they  imbed  themselves  in  the  submucous  cellular  tissue, 
which  has  all  along  constituted  the  external  layer  of  the  milk-sac.     The  implantation  of  the 
Permanent  tooth-sacs  in  the  walls  of  the  Temporary  follicles,  gives  to  the  former  the  appear- 
ance of  being  produced,  by  a  gemmiparous  process  from  the  latter.     This  series  of  changes 
is  represented  in  Fig.  88,  g — n. 

c.  We  now  return  to  the  Milk-teeth,  the  papillae  of  which,  from  the  time  that  their  follicles 
close,  become  gradually  moulded  into  their  peculiarly  Human  shape.     The  Molar  pulps  be- 
gin to  be  perforated  by  three  canals,  which,  proceeding  from  the  surface  towards  the  centre, 
gradually  divide  their  primary  bases  into  three  secondary  bases ;  and  these  become  deve- 
loped into  the  fangs  of  the  future  teeth.     Whilst  this  is  going  on,  the  sacs  grow  more  rapidly 
than  the  papilla?,  so  that  there  is  an  intervening  space,  which  is  filled  with  a  gelatinous  gra- 
nular substance — the  enamel  blastema ;  this  closely  applies  itself  to  the  surface  of  the  pa- 
pilla, but  does  not  adhere   to  it.     The  branch  of  the  dental  artery  which  proceeds  to  each 
sac,  ramifies  minutely  in  its  proper  membrane,  but  does  not  send  the  smallest  twig  into  the 
granular  substance.     At  this  period,  the  tubercles  and  apices  of  the  papillas  or  pulps  become 
converted  into  real  dentine  or  tooth-substance,  in  the  manner  already  stated  (§  213)  ;  and  the 
granular  matter  is  absorbed  as  fast  as  this  appears ;  so  that,  when  the  process  of  conversion 
has  reached  the  base  of  the  pulp,  the  interior  of  the  dental  sac  is  left  in  the  villous  and  vas- 
cular condition  of  a  true  Mucous  membrane,  having  upon  it  a  very  thin  layer  of  the  granular 
substance,  or  enamel  pulp,  which  may  be  considered  as  a  sort  of  Epithelium  ;  and  it  is  by 
the  deposition  of  calcareous  matter  in  the  long  prismatic  cells  of  this,  that  the  enamel  is 


00 


Diagrams  illustrative  of  the  formation  of  the  three  Permanent  Molar  teeth,  from  the  non-adherent 
portion  of  the  Dental  Groove. 

formed.  The  opercula,  which  close  the  mouth  of  the  dental  sac,  attain  a  much  greater  de- 
velopment in  the  Molar  teeth  of  Herbivorous  animals;  where  they  dip  down  into  the  midst 
of  the  dentinal  pulp,  and  give  origin  to  insulated  spots  both  of  enamel  and  cementum.  It 
has  been  remarked  by  Mr.  Lintott,  that  the  lines  along  which  the  opercula  meet,  on  the 


DEVELOPMENT  OF  THE  TEETH.  185 

crown  of  the  Human  molar  teeth, — that  is  to  say.  the  groove  which  separates  their  tubercles, 
— is  by  far  the  most  frequent  seat  of  incipient  decay ;  probably  from  its  tissue  having  been 
at  the  first  less  perfectly  formed  than  that  of  the  remainder. 

d.  Whilst  these  changes  are  going  on,  other  important  preparations  are  being  made  for  the 
Permanent  set.     The  general  adhesion  of  the  edges  of  the  Primitive  Dental  Groove,  (§  a) 
does  not  invade  the  portion  which  is  situated  behind  the  Posterior  Milk  follicle ;  this  retains 
its  original  appearance  for  a  fortnight  or  three  weeks  longer,  and  affords  a  nidus  for  the  de- 
velopment of  the  papilla  and  follicle  of  the  Anterior  Permanent  Molar  tooth,  which  is  de- 
veloped in  all  respects  on  the  same  plan  with  the  Milk  teeth.     After  its  follicle  has  closed, 
the  edges  of  the  dental  groove  meet  over  its  mouth ;  but  as  the  walls  of  the  groove  do  not 
adhere,  a  considerable  cavity  is  left  between  the  sac  of  the  tooth  and  the  surface  of  the 
gum.     The  cavity  is  a  reserve  of  delicate  mucous  membrane,  to  afford  materials  for  the 
formation  of  the  Second  Permanent  Molar,  and  of  the  Third  Permanent  Molar,  or  Wisdom- 
tooth.     The  process  just  described  is  represented  in  Fig.  89,  a — c.     It  will  be   convenient 
here  to  continue  the  account  of  the  development  of  these  teeth,  although  it  takes  place  at  a 
much  later  period.     Towards  the  end  of  fretal  life,  the  increase  of  the  bulk  of  the  Milk-tooth 
sacs  takes  place  so  much  more  rapidly  than  the  growth  of  the  jaw,  that  the  sac  of  the  An- 
terior Permanent  Molar  is  forced  backwards  and  upwards,  into  the  maxillary  tuberosity  5 
and  thus  it  not  only  draws  the  surface  of  the  gum  in  the  same  direction,  but  lengthens  out 
the  great  cavity  of  reserve  (Fig.  99,  e?).     During  the  few  months  which  succeed  birth,  how- 
ever, the  jaw  is  greatly  lengthened ;  and  when  the  infant  is  eight  or  nine  months  old,  the 
Anterior  Permanent  Molar  resumes  its  former  position  in  the  posterior  part  of  the  dental 
arch ;  and  the  great  cavity  of  reserve  returns  to  its  original  size  and  situation  (c).     This 
cavity,  however,  soon  begins  to  bulge  out  at  its  posterior  side,  and  projects  itself,  as  a  sac,  into 
the  maxillary  tuberosity  (y)  ;  a  papilla  or  pulp  appears  in  its  fundus ;  and  a  process  of  con- 
traction separates  it  from  the  remainder  of  the  cavity  of  reserve.     Thus  the  formation  of 
the  Second  Permanent  Molar  from  the  first,  takes  place  on  precisely  the  same  plan  with  the 
formation  of  the  Permanent  Bicuspids  from  the  Temporary  Molars.     The  new  sac  at  first 
occupies  the  maxillary  tuberosity  (g)  ;  but  the  lengthening  of  the  jaw  gradually  allows  it  to 
fall  downwards  and  forwards,  into  the  same  line,  and  on  a  level,  with  the  rest  (A).     Before 
it  leaves  the  tuberosity  altogether,  the  posterior  extremity  of  the  remainder  of  the  cavity  of 
reserve  sends  backwards  and  upwards  its  last  offset — the  sac  and  pulp  of  the  Wisdom-tooth 
(i) ;  this  speedily  occupies  the  tuberosity  after  the   second  molar  has  left  it  (j)  ;  and  ulti- 
mately, when  the  jaw  lengthens  for  the  last  time,  at  the  age  of  nineteen  or  twenty,  it  takes 
its  place  at  the  posterior  extremity  of  the  range  of  the  adult  teeth  (&).     Thus,  the  Wisdom- 
teeth  are  the  second  products  of  the  posterior  or  great  cavities  of  reserve ;  and  the  final  effects 
of  development  in  the  secondary  dental  groove.     In  the  Elephant,  in  which  there  is  a  con- 
tinual new  production  of  molar  teeth  at  the  back  of  the  jaw,  it  is  probable  that  from  each 
sac  a  cavity  of  reserve  is  formed,  which  produces  the  succeeding  tooth ;  and  thus  the  only 
essential  difference  between  its  dentition  and  that  of  Man,  consists  in  the  degree  of  continu- 
ance of  this  gemmiparous  process ;  which  ceases  in  Man,  after  being  twice  performed,  but 
is  repeated  in  the  Elephant  until  nearly  the  close  of  its  life. 

e.  We  have  thus  sketched  the  history  of  the  Development  of  the  Teeth,  up  to  the  time 
when  they  prepare  to  make  their  way  through  the  gurn.     The  first  stage  of  this  development 
may  be  termed  the  papillary  •  and  the  second  the  follicular.     The  latter  terminates  when  the 
papillae  are  completely  hidden  by  the  closure  of  the  mouths  of  the  follicles,  and  of  the  groove 
itself.     The  succeeding  stage,  which  has  long  been  known  as  the  saccular,  is  the  one  during 
which  the  whole  formation  of  the  Tooth-substance,  and  of  the  Enamel,  takes  place.     It  is 
during  this  period,  also,  that  the  ossification  of  the  jaw  is  being  effected ;  and  that  the  bony 
sockets  are  formed  for  the  teeth,  by  the  consolidation  of  the  anterior  and  posterior  ridges 
bounding  the  alveolar  groove  (in  which  the  dental  groove  was  originally  imbedded),  and  of 
the  interfollicular  septa,  which  are  produced  by  the  meeting  of  transverse  projections  from 
these  ridges. — The  history  of  development  in  the  Lower  Jaw  is  very  nearly  the  same;  the 
chief  difference  being  in  the  origin  and  situation  of  the  primitive  dental  groove. 

/.  We  have  now  only  to  consider  the  fourth  or  eruptive  stage, — that  in  which  the  Teeth 
make  their  way  through  the  gum.  This  process  chiefly  results  from  the  lengthening  of  the 
fang,  by  the  addition  of  new  bony  matter ;  and  the  crown  of  the  tooth  is  thus  made  to  press 
against  the  closed  mouth  of  the  sac  (Fig.  98,  m).  This  at  last  gives  way,  so  that  the  sac  as- 
sumes its  previous  condition  of  an  open  follicle.  When  the  edge  of  the  tooth  has  once  made 
its  way  through  the  gum,  it  advances  more  rapidly  than  can  well  be  accounted  for  by  the 
usual  rate  of  lengthening  of  its  fang;  and  this  appears  to  be  due  to  the  separation  of  the 
bottom  of  the  sac  from  the  fundus  of  the  alveolus ;  so  that  the  whole  tooth-apparatus  is  car- 
ried nearer  to  the  surface,  leaving  a  space  at  the  bottom  of  the  alveolar  cavity,  in  which  the 
further  lengthening  of  the  root  can  take  place  («).  The  open  portion  of  the  sac  remains  as 
the  narrow  portion  of  the  gum,  which  forms  a  vascular  border  arid  groove  round  the  neck 
of  the  perfected  tooth  (o).  The  deeper  portion  of  the  sac  adheres  to  the  fang  of  the  tooth, 

16* 


186  ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 

and  is  converted  by  ossification  into  the  Cementum  or  Crusta  Petrosa  (§  216).  What  is 
Commonly  denominated  the  Periosteum  of  the  Tooth,  really  belongs  as  much  to  the  Alveolus. 
It  is  connected  with  the  tooth  by  the  submuoous  cellular  tissue,  which  originally  intervened 
between  the  tooth-sac  and  the  walls  of  the  osseous  cavity.  It  appears  from  Mr.  Nasmyth's 
researches,  that  the  inner  layer  of  the  portion  of  the  capsule  which  covered  the  crown  of 
the  tooth,  remains  adherent  to  it;  forming  a  thin  coating  of  Crusta  Petrosa  (most  of  which 
is,  however,  soon  worn  off)  over  the  Enamel. — During  the  period  that  the  Milk-teeth  have 
been  advancing,  along  with  their  sockets,  to  their  perfect  state  and  ultimate  position,  the  Per- 
manent sacs  have  been  receding  in  an  opposite  direction,  and  have  with  their  bony  crypts 
been  enlarging;  and  at  last  they  occupy  a  position  almost  exactly  below  the  former  (n  ando). 
They  still  retain  a  communication  with  the  gum,  however;  the  channel  by  which  they  de- 
scended not  having  completely  closed  up,  arid  the  neck  of  the  sac  being  elongated  into  a 
cord  which  passes  through  this.  The  channels  may  afterwards  serve  as  the  itinera  dentium, 
and  the  cords  as  gubernacula  ;  but  it  is  uncertain  whether  they  really  afford  any  assistance  in 
directing  the  future  rise  of  the  tooth  to  the  surface  ;  the  successive  stages  of  which  are  repre- 
sented in  Fig.  98, p — t.  The  sacs  of  the  permanent  teeth  derive  their  first  vessels  from  the 
gums ;  ultimately  they  receive  their  proper  dental  vessels  from  the  Milk-sacs ;  and,  as  they 
separate  from  the  latter  into  their  own  cells,  the  newly-formed  vessels,  conjoining  into  com- 
mon trunks,  also  retire  into  permanent  dental  canals,  and  gradually  become  the  most  direct 
channels  for  the  blood  transmitted  through  the  jaw. 

g.  The  following  interesting  generalizations  respecting  the  development  of  the  teeth,  result 
from  Mr.  Goodsir's  researches.  1.  The  Milk-teeth  are  formed  on  both  sides  of  either  jaw 
in  three  divisions, — a  Molar,  a  Canine,  and  an  Incisive ;  in  each  of  which,  dentition  pro- 
ceeds in  an  independent  manner.  2.  The  dentition  of  the  whole  arch  proceeds  from 
behind  forwards;  the  Molar  division  commencing  before  the  Canine,  and  the  Canine 
before  the  Incisive.  3.  The  dentition  of  each  of  the  divisions  proceeds  in  a  contrary  direc- 
tion, the  Anterior  Molar  appearing  before  the  Posterior,  the  Central  Incisor  before  the  La- 
teral. 4.  Two  of  the  subordinate  phenomena  of  nutrition  also  obey  this  inverse  law ; — 
the  follicles  closing  by  commencing  at  the  median  line  and  proceeding  backwards  ;  and  the 
dental  groove  disappearing  in  the  same  direction.  5.  Dentition  commences  in  the  Upper 
Jaw,  and  continues  in  advance  during  the  most  important  period  of  its  progress.  The 
development  of  the  Superior  Incisors,  however,  is-  retarded  by  a  peculiar  cause;  so  that  the 
Inferior  Incisors  have  the  priority  in  the  time  of  their  completion  and  appearance.  6.  The 
germs  of  the  Permanent  teeth,  with  the  exception  of  that  of  the  Anterior  Molar,  appear  in  a 
direction  from  the  median  line  backwards.  7.  The  Milk-teeth  originate,  or  are  developed, 
from  mucous  membrane.  8.  The  Permanent  teeth,  also  originating  from  mucous  membrane, 
are  of  independent  origin,  and  have  no  connection  with  the  milk-teeth.  9.  A  tooth-pulp 
and  its  sac  must  be  referred  to  the  same  class  of  organs,  as  the  combined  Papilla  and  Folli- 
cle from  which  a  hair  or  feather  is  developed. 

h.  The  following  is  the  usual  order  and  period  of  appearance,  of  the  several  pairs  of  Milk- 
teeth.  The  Four  Central  Incisors  first  present  themselves,  usually  about  the  seventh  month 
after  birth ;  but  frequently  much  earlier  or  later  :  those  of  the  Lower  Jaw  appear  first. 
The  Lateral  Incisors  next  show  themselves,  those  of  the  Lower  Jaw  coming  through  before 
those  of  the  upper ;  they  usually  make  their  appearance  between  the  seventh  and  tenth  months. 
After  a  short  interval,  the  Anterior  Molars  present  themselves. — generally  soon  after  the 
commencement  of  the  Second  Year  ;  and  these  are  followed  by  the  Canines,  which  usually 
protrude  themselves  between  the  fourteenth  and  twentieth  months.  The  Posterior  Molars  are 
the  last,  and  the  most  uncertain  in  regard  to  their  time  of  appearance ;  this  varying  from 
the  eighteenth  to  the  thirty-sixth  month.  In  regard  to  all  except  the  front  teeth,  there  is  no 
settled  rule  as  to  the  priority  of  appearance  of  those  in  the  Upper  or  Under  Jaw ;  some- 
times one  precedes,  and  sometimes  the  other;  but  in  general  it  may  be  stated,  that,  when- 
ever one  makes  its  appearance,  the  other  cannot  be  far  off.  The  same  holds  good  in  re- 
gard to  the  two  sides,  in  which  development  does  not  always  proceed  exactly  pari  passu. — 
The  period  of  Dentition  is  one  of  considerable  risk  to  the  Infant's  life.  The  pressure  upon 
the  nerves  of  the  gum,  which  necessarily  precedes  the  opening  of  the  sac  and  the  eruption 
of  the  tooth,  is  a  fruitful  source  of  irritation ;  producing  disorder  of  the  whole  system,  espe- 
cially of  the  Digestive  organs,  and  not  unfrequently  giving  origin  to  fatal  Convulsive  affec- 
tions. These  last  have  been  particularly  studied  by  Dr.  M.  Hall,  who  recommends  the  free 
use  of  the  gum-lancet,  as  a  most  important  means  of  prevention  and  cure.  Even  where 
Dentition  proceeds  quite  naturally  and  is  not  itself  a  cause  of  diseased  action,  it  induces  an 
irritable  state  of  the  whole  constitution,  which  aggravates  the  effects  of  other  morbific  causes. 
It  is,  therefore,  of  the  greatest  consequence  that  the  infant  should  be  withdrawn  during  this 
period,  from  all  injurious  influences ;  and  that  no  irregularity  of  diet,  or  deficiency  of  fresh 
air  and  exercise,  should  operate  to  its  disadvantage. 

i.  After  the  lapse  of  a  few  years,  the  further  elongation  of  the  jaw  permits  the  appear- 
ance of  the  First  True  Molar;  which,  as  already  remarked,  is  really  a  Milk-tooth,  so  far  as 
its  formation  is  concerned.  This  commonly  presents  itself  about  the  middle  or  end  of  the 


DEVELOPMENT  OF  THE  TEETH.  187 

Seventh  Year;  sometimes  preceding,  and  sometimes  following,  the  exchange  of  the  Central 
Incisors,  which  takes  place  about  the  same  time.  When  the  Permanent  Teeth  have  so 
much  enlarged,  that  they  can  no  longer  be  contained  within  their  own  alveoli,  they  press 
upon  the  anterior  parietes  of  those  cavities,  and  cause  their  absorption ;  so  that  each  tooth 
is  allowed  to  come  forwards,  in  some  degree,  into  the  lower  part  of  the  socket  of  the  cor- 
responding Temporary  tooth.  The  root  of  the  temporary  tooth  now  begins  to  be  absorbed, 
generally  at  the  part  nearest  its  successor ;  and  this  absorption  proceeds  as  the  new  tooth 
advances,  until  the  root  of  the  Milk-tooth  is  completely  removed:  when  its  crown  falls  off, 
leaving  room  for  the  permanent  tooth  to  supply  its  place  (Fig.  88,  p — £).  This  absorption 
is  usually  regarded  as  due  to  the  pressure  of  the  Permanent  tooth,  but  this  does  not  appear 
to  be  the  case ;  for  it  is  mentioned  by  Mr.  Bell,  that  it  is  not  an  uncommon  occurrence  for 
the  root  of  the  temporary  tooth  to  be  wholly  absorbed,  and  for  the  crown  to  fall  out  spon- 
taneously, long  before  the  succeeding  tooth  has  approached  the  vacant  space.  The  same 
has  been  remarked  by  Mr.  Bell,  of  the  cavity  in  the  jaw  which  is  formed  for  the  reception 
of  the  sac  of  the  Permanent  tooth,  at  the  time  that  it  buds  off  from  that  of  the  milk-tooth  5 
the  excavation  being  often  seen  to  commence  before  the  new  sac  is  formed.  Hence,  although 
the  two  processes,  growth,  and  absorption,  are  usually  contemporaneous  in  each  instance, 
they  are  by  no  means  dependent  on  each  other.  Still  it  would  seem  that  the  existence,  if 
not  the  pressure  of  the  new  Tooth  is  necessary  to  determine  the  absorption  of  the  old  ;  for 
cases  are  not  unfrequent,  in  which  the  Temporary  teeth  retain  their  situation  in  the  mouth, 
with  considerable  firmness,  until  adult  age, — the  corresponding  permanent  ones  not  having 
been  formed. 

k.  In  the  successive  replacement  of  the  Milk-teeth  by  the  Permanent  set,  a  very  regular 
order  is  usually  followed.  The  Middle  Incisors  are  first  shed  and  renewed,  and  then  the 
Lateral  Incisors.  The  Anterior  Milk  Molars  next  follow ;  and  these  are  replaced  by  the  An- 
terior Bicuspid  teeth.  About  a  year  afterwards,  the  Posterior  Milk  Molars  are  shed,  and  are 
replaced  in  like  manner  by  Bicuspid  teeth.  The  Canines  are  the  last  of  the  Milk-teeth  to 
be  exchanged  ;  the  development  of  the  new  ones  not  taking  place  until  the  12th  year.  In 
the  succeeding  year,  the  Second  pair  of  the  True  Molars  appears ;  the  third  pair,  or  denies 
sapientuK,  are  seldom  developed  until  three  or  four  years  subsequently,  and  often  much 
longer.  It  has  been  recently  proposed*  (and,  from  the  evidence  adduced  in  its  favour,  the 
proposition  would  seem  entitled  to  considerable  attention)  to  adopt  the  successive  stages  in 
the  Second  Dentition,  as  standards  for  estimating  the  physical  capabilities  of  Children,  es- 
pecially in  regard  to  those  two  periods  which  the  Factory  Laws  render  it  of  the  greatest 
importance  to  determine,  namely,  the  ages  of  nine  and  thirteen  years.  Previously  to  the  for- 
mer, a  child  is  not  permitted  to  work  at  all ;  and  up  to  the  latter,  it  may  be  only  employed 
during  9  hours  a  day.  The  necessities  or  the  cupidity  of  Parents  are  continually  inducing 
them  to  misrepresent  the  ages  of  their  children;  and  it  has  been  found  desirable,  therefore, 
to  seek  for  some  test,  by  which  the  capability  of  the  Child  may  be  determined,  without  a 
knowledge  of  its  age.  A  standard  of  Height  has  been  adopted  by  the  Legislature  for  this 
purpose;  but  upon  grounds  which,  Physiologically  considered,  are  very  erroneous ;  since,  as  is 
well  known,  the  tallest  children  are  frequently  the  weakliest.  According  to  Mr.  Saunders, 
the  degree  of  advance  of  the  Second  Dentition  may  be  regarded  as  a  much  more  correct 
standard  of  the  degree  of  general  development  of  the  organic  frame,  and  of  its  physical 
powers ;  and  it  appears  from  his  inquiries,  that  it  may  be  relied  on  as  a  guide  to  the  real 
age,  in  a  large  proportion  of  cases ;  whilst  no  serious  or  injurious  mistake  can  ever  arise 
from  its  use.  It  may  happen  that  local  or  constitutional  causes  may  have  slightly  retarded 
the  development  of  the  Teeth  ;  in  which  case  the  age  of  the  individual  would  rather  be 
under-estimated,  and  no  harm  could  ensue :  on  the  other  hand,  instances  of  preiTiature  de- 
velopment of  the  Teeth  very  rarely,  if  ever,  occur  :  so  that  there  is  no  danger  of  imputing 
to  a  Child  a  capability  for  exertion  which  he  does  not  possess,  as  the  test  of  height  is  con- 
tinually doing.  Moreover,  if  such  an  advance  in  Dentition  should  occur,  it  might  probably 
be  regarded  as  indicative  of  a  corresponding  advance  in  the  development  of  the  whole  or- 
ganism ;  so  that  the  real  capability  would  be  such  as  the  teeth  represent  it. 

/.  The  following  is  Mr.  Saunders'  statement  of  the  Ages  at  which  the  Permanent  teeth 
respectively  appear.  The  first  True  Molars  usually  make  their  appearance  towards  the  end 
of  the  7th  year.  Occasionally  one  of  them  protrudes  from  the  gum  at  6,  or  more  frequently 
at  6$  years  of  age ;  but  the  evolution  of  the  whole  of  them  may  be  regarded  as  an  almost 
infallible  sign  of  the  Child's  being  7  years  old.  In  other  instances,  however,  where  the  tooth 
on  one  side  of  the  mouth  is  freely  developed,  it  is  fair  to  reckon  the  two  as  having  emerged 
from  their  capsule  ;  since  the  development  of  the  other  must  be  considered  as  retarded.  This 
rule  only  holds  good,  however,  in  regard  to  teeth  in  the  same  row ;  for  the  development  of 
the  teeth  in  either  jaw  must  not  be  inferred  from  that  of  the  corresponding  teeth  in  the  other. 

*  "The  Teeth  a  Test  of  Age,  considered  with  reference  to  the  Factory  Children."  By 
Edwin  Saunders. 


188          ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 

With  this  understanding,  the  results  of  the  application  of  the  following  table  will  probably 
be  very  near  the  truth. 

Central  Incisors  developed  at         ....         8  years. 
Lateral  Incisors  .         .         .         .         .         .         9    — 

First  Bicuspid  10    — 

Second  Bicuspid 11    — 

Canines 12    to  12^ 

Second  Molars  12^  to     14 

The  following  are  the  results  of  the  application  of  this  test,  in  a  large  number  of  cases 
examined  by  Mr.  Saunders.  Of  708  children  of  nine  years  old,  530  would  have  been  pro- 
nounced by  it  to  be  near  the  completion  of  their  ninth  year ;  having  the  central,  and  either 
three  or  four  lateral,  incisors  fully  developed.  Out  of  the  remaining  178,  it  would  have  in- 
dicated that  126  were  8£  years  old,  as  they  presented  one  or  two  of  the  Lateral  Incisors; 
and  the  52  others  would  have  been  pronounced  8  years  old,  all  having  three  or  four  of  the 
Central  Incisors.  So  that  the  extreme  deviation  is  only  12  months ;  and  this  in  the  incon- 
siderable proportion  (when  compared  with  the  results  obtained  by  other  means)  of  52  in  708, 
or  7^  per  cent.  Again,  out  of  338  children  of  13  years  of  age,  294  might  have  been  pro- 
nounced with  confidence  to  be  of  that  age,  having  the  Canines,  Bicuspid,  and  Second  Molars, 
either  entirely  developed,  or  with  only  the  deficiency  of  one  or  two  of  either  class.  Of  the 
44  others,  36  would  have  been  considered  as  in  their  13th  year,  having  one  of  the  Posterior 
Molars  developed  ;  and  8  as  near  the  completion  of  the  12th,  having  two  of  the  Canines, 
and  one  or  two  of  the  Second  Bicuspid.  In  all  these  instances,  the  error  is  on  the  favourable 
side, — that  is,  on  the  side  on  which  it  is  calculated  to  prevent  injury  to  the  objects  of  the 
inquiry  ;  in  no  instance  did  this  test  cause  a  Child  to  be  estimated  as  older  or  more  fit  for 
labour  than  it  really  was. 

m.  The  value  of  this  test,  as  compared  with  that  of  Height,  is  manifested  by  a  striking  ex- 
ample adduced  by  Mr.  Saunders.  The  height  of  one  lad,  J.  J.,  aged  8  years  and  4  months, 
was  4  feet  and  £  of  an  inch  ;  that  of  another  boy,  aged  8  years  and  7  months,  was  only  3 
feet  7£  inches.  According  to  the  standard  of  height  adopted  by  the  Factory  Commissioners 
(namely,  3  feet  10  inches),  the  taller  lad  would  have  been  judged  fit  for  labour,  whilst  the 
shorter  would  have  been  rejected.  The  Dentition  of  the  latter,  however,  was  further  ad- 
vanced than  that  of  the  former;  for  he  had  two  of  the  Lateral  Incisors,  whilst  the  former 
had  only  the  Central ;  and  the  determination  of  their  relative  physical  powers,  which  would 
have  been  thus  formed,  would  have  been  in  complete  accordance  with  the  truth.  The  elder 
boy,  though  shorter  than  the  other  by  5£  inches,  possessed  a  much  greater  degree  both  of 
corporeal  and  mental  energy,  and  his  pulse  was  strong  and  regular ;  whilst  that  of  the 
younger  lad,  who  was  evidently  growing  too  fast,  was  small  and  frequent. — An  instance 
even  more  striking  has  come  under  the  Author's  own  observation. 

10.  Simple  Tubular  Tissues. 

218.  We  have  seen  that  all  the  Animal  Tissues,  whose  structure  has  been 
yet  considered,  derive  the  materials  of  their  growth  and  renovation  from  the 
nutrient  fluid ;  which  is  brought  into  a  more  or  less  close  relation  with  their 
elementary  parts,  by  means  of  Capillary  blood-vessels.  These  seem  to  have 
a  claim  to  be  regarded  as  among  the  elementary  parts  of  the  fabric;  since  they 
are  formed  quite  independently  of  the  larger  trunks,  and  have  little  in  common 
with  them  in  their  function.  All  those  changes  which  take  place  between 
the  blood  and  the  surrounding  parts,  whether  ministering  to  the  functions  of 
Nutrition,  Secretion,  or  Respiration,  occur  during  its  movement  through  the 
Capillary  vessels:  and  the  function  of  the  larger  trunks  is  merely  to  bring  to 
them  a  constant  supply  of  fresh  blood,  regulated  according  to  the  demand 
created  by  the  actions  to  which  it  is  subservient ;  and  to  remove  the  fluid 
which  has  circulated  through  them.  When  we  examine  into  the  structure  of 
the  Circulating  apparatus  in  Plants  and  in  the  lower  Animals,  we  find  that 
the  canals,  which  convey  the  nutritive  fluid,  are  of  two  kinds  ; — either  simple 
excavations  in  the  solid  tissues  or  unfilled  vacuities  ; — or  tubes  with  definite 
membranous  walls.  The  former  are  known,  in  Plants,  under  the  name  of 
inter-cellular  passages  ;  and,  among  the  lower  tribes  in  particular,  they  have 
a  large  share  in  the  conveyance  of  the  nutritious  fluid  from  one  part  of  the 


STRUCTURE  OF  CAPILLARY  BLOOD-VESSELS. 


189 


structure  to  the  other.  Similar  passages  exist  to  a  great  extent  among  the  In- 
vertebrata ;  the  venous  circulation  in  particular  being  mainly  carried  on  by 
them.  We  have  an  example  of  them,  even  in  Man,  in  the  Sinuses  through 
which  the  venous  blood  is  returned  from  the  Brain  ;  these  sinuses  being  simple 
passages  formed  by  the  folds  of  the  Dura  Mater.  In  the  higher  Plants,  however, 
the  circulation  of  fluid  is  for  the  most  part  carried  on  through  Ducts,  having 
distinct  membranous  parietes ;  and  these  ducts  may  be  either  straight  and 
simple  tubes,  as  are  those  of  the  interior  of  the  stem  through  which  the  sap 
ascends  ;  or  they  may  form  a  network  by  their  mutual  anastomosis,  such  as 
that  by  which  the  sap  descends  through  the  bark  and  newer  wood.  Both  of 
these  forms  of  ducts  appear  to  be  formed  by  the  coalescence  of  cells  ;  the 
straight  cylindrical  ducts  being  formed  from  cells,  arranged  in  a  simple  linear 
manner ;  and  the  network  of  vessels  for  the  descent  of  the  elaborated  sap, 
being  produced  by  the  junction,  at  various  points,  of  cells  of  less  regular  form, 
which  stretch  out  to  meet  each  other. 

219.  In  all  the  higher  Animals, — in  their  adult  condition  at  least, — the 
Capillary  circulation  is  entirely  carried  on  through  tubes  having  distinct  mem- 
branous parietes.  These  tubes  commonly  form  a  minutely-anastomosing  net- 
work ;  into  which  the  blood  is  brought  by  the  ramifications  of  the  arteries  on 
one  side,  and  from  which  it  is  returned  by  the  radicles  of  the  veins  on  the  other. 
The  walls  of  the  tubes  are  composed  of  a  delicate  membrane,  in  which  an 
appearance  of  transverse  striation  (as  if  produced  by  minute  annular  fibres) 
can  sometimes  be  discerned.  The  diameter  of  the  Capillaries  varies  in  dif- 
ferent animals,  in  accordance  with  that  of  their  blood-corpuscles ;  thus  the 

Fig.  90. 


Capillary  circulation  in  a  portion  of  the  web  of  a  Frog's  foot,  magnified  110  diameters ;  1,  trunk  of 
vein ;  2,  2,  its  branches  ;  3,  3,  pigment  cells. 

Capillaries  of  the  Frog  are  of  course  much  larger  than  those  of  Man.  The 
diameter  of  the  latter  appears,  from  the  measurements  of  Weber,  Mu'ller,  and 
others,  to  vary  from  about  the  1 -3700th  to  the  1 -2500th  of  an  inch  ,-  but  as 
they  can  only  be  examined  after  death,  it  is  probable  that  these  statements  are 


190  ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 

not  altogether  exact,  particularly  as  tubes  of  the  smallest  of  the  above  sizes 
would  not  admit  ordinary  blood-corpuscles.  The  dimensions  of  the  individual 
vessels,  indeed,  are  by  no  means  constant ;  as  may  be  seen  by  watching  the 
Circulation  in  any  transparent  part,  for  some  little  time.  Putting  aside  the 
general  changes,  in  diameter,  which  result  from  circumstances  affecting  all  the 
capillaries  of  a  part,  it  may  be  observed  that  a  single  capillary  will  sometimes 
enlarge  or  contract  by  itself  without  any  obvious  cause.  Thus,  the  stream 
of  blood  will  sometimes  be  seen  to  run  into  passages,  which  were  not  before 
perceived ;  and  it  has  hence  been  supposed  that  they  were  new  excavations, 
formed  by  the  retreating  or  removal  of  the  solid  tissue  through  which  it  passes. 
But  a  more  attentive  examination  shows,  that  such  passages  are  real  capilla- 
ries, which  did  not,  at  the  time  of  the  first  observation,  admit  the  stream  of 
blood-corpuscles,  in  consequence  of  the  contraction  of  their  calibre,  or  of  some 
other  local  impediment ;  and  that  they  are  brought  into  view  by  the  simple 
increase  in  their  diameter.  The  compression  of  one  of  the  small  arteries 
will  generally  occasion  an  oscillation  of  the  corpuscles  of  blood  in  the  small- 
est capillaries,  which  will  be  followed  by  the  disappearance  of  some  of  them  ; 
but  when  the  obstruction  is  removed,  the  blood  soon  regains  its  former  velocity 
and  force,  and  flows  exactly  into  the  same  passages  as  before. 

220.  The  opinion  was  long  entertained,  that  there  are  vessels  adapted  to  sup- 
ply the  white  or  colourless  tissues ;  carrying  from  the  arteries  the  Liquor 
Sanguinis,  or  fluid  portion  of  the  blood;  and  leaving  the  Corpuscles  behind, 
through  inability  to  receive  them.  But  such  a  supposition  is  altogether 
groundless.  Some  of  the  white  tissues,  as  Cartilage,  are  altogether  destitute 
of  vessels ;  and  in  others,  the  supply  of  blood  is  so  scanty,  as  not  to  commu- 
nicate to  them  any  decided  hue.  It  is  evident  from  what  has  been  already 
stated,  that  the  idea  that  Nutrition  can  only  be  carried  on  by  means  of  Capil- 
lary vessels,  is  entirely  gratuitous.  There  is  no  essential  difference,  in  fact, 
between  the  nutrition  of  the  non-vascular  tissues,  and  that  of  the  islets  in  the 
midst  of  the  network  of  capillary  vessels,  which  traverses  the  most  vascular. 

Fig.  91. 


Capillary  vessels  from  the  pia  mater ;  o.  calibre  of  the  tube,  partly  occupied  by  oval  nuclei,  alter- 
nately arranged  lengthways,  and  epithelial  in  their  character;  6,  b,  b,  nuclei  projecting  on  the  exterior 
of  the  tube ;  c,  c,  walls,  and  d,  calibre,  of  a  large  branch  ;  /,/,  oval  nuclei,  arranged  transversely.  Mag- 
nified 410  diameters. 


FORMATION  OF  CAPILLARY  BLOOD-VESSELS.  191 

In  both  cases,  the  nutrient  materials  conveyed  by  the  blood  are  absorbed  by 
the  cells  or  other  elementary  parts  of  the  tissue  immediately  adjoining  the 
vessels,  and  are  imparted  by  them  to  others  which  are  further  removed  ;  and 
the  only  variation  which  exists,  is  in  the  amount  of  the  portion  of  tissue  that 
has  to  be  thus  traversed.  There  is  great  variety  in  this  respect,  as  we 
have  seen,  among  the  vascular  tissues  ;  and  we  are  only  required  to  extend 
our  ideas,  from  the  largest  of  the  islets  which  we  find  in  these,  to  the  still 
more  isolated  structures,  of  which  the  non-vascular  tissues  are  composed. 
The  distribution  of  Capillaries  through  the  vascular  tissues,  and  the  character 
of  the  reticulation  which  they  form,  vary  so  greatly  in  the  different  parts  of 
the  fabric,  that  it  is  possible  to  state  with  tolerable  certainty  the  nature  of  the 
part  from  which  any  specimen  has  been  detached, — whether  a  portion  of 
skin,  mucous  membrane,  serous  membrane,  muscle,  nerve,  fat,  areolar  tissue, 
gland,  &c.  But  the  arrangement  of  vessels  peculiar  to  each  evidently  has 
reference  only  to  the  convenience  of  the  distribution  of  blood  among  the 
elementary  parts  of  the  tissue,  and  varies  with  their  form.  It  is  not  possible 
to  imagine  that  it  has  any  other  relation  than  this  to  their  function ;  since,  as 
already  shown,  the  function  of  each  separate  element  of  the  organ,  of  which 
that  of  the  entire  organ  is  the  aggregate,  is  due  to  its  own  inherent  vital 
powers, — the  supply  of  blood  being  only  required  as  furnishing  the  material, 
on  which  these  are  to  be  exercised. 

221.  It  has  been  rendered  highly  probable,  by  the  observations  of  Schwann 
and  other  Physiologists,  that  the  Capillaries  of  Animals  originate  in  cells,  like 
the  straight  and  anastomosing  Ducts  of  Plants.     Bodies  having  the  appear- 
ance of  cell-nuclei  may  frequently  be  seen  in  the  walls  of  the  capillaries  of 
embryos  and  of  tadpoles  ;  and  these  are  too  wide  apart  to  warrant  the  idea,  that 
they  are  the  nuclei  of  epithelial  cells,  such   as  those  which  line  the  larger 
vessels.     Similar  nuclei  may  be  brought  into  view  in  the  capillaries  of  adult 
animals,  by  treating  them  with  acetic  acid  ;  and  they  are  particularly  well 
seen  in  the  Pia  Mater,  which  consists  almost  entirely  of  a  congeries  of  blood- 
vessels (Fig.  91).     The  accompanying  figure  shows  the  contrast  between  the 
long  oval  nuclei  b,  6,  imbedded  at  intervals  in  the  walls  of  the  true  capillaries, 
and  rather  projecting  on  their  exterior ;  and  the  nuclei  of  the  epithelium-cells, 

y, /,  lining  the  interior  of  a  larger  branch,  which  last  are  more  numerous  and 
of  less  regular  form,  and  are  sometimes  placed  transversely  to  the  direction  of 
the  tube. 

222.  The  first  formation  of  the  Capillary  blood-vessels    in  the  vascular 
area  in  the  Bird's  egg,  is  described  by  Schwann  as  being 

affected  entirely  by  the  coalescence  of  cells,  which  send 

off  prolongations  in  various  directions,  in  the  manner  of 

stellate  pigment-cells,  such  as  those  seen  at  c,  c,  Fig.  90. 

By  the  junction  of  these  prolongations,  a  network  of  tubes 

is  formed,  which  is  at  first  very  irregular  in  its  character ; 

the  greatest  diameter  of  the  tubes  being  in  the  situation 

of  the  centres  or  bodies  of  the  original  cells;  whilst  be- 

tween  these,  at  the  points  where  their  prolongations  coa- 

lesced,  they  are  much  contracted.    The  calibre  of  the  ves- 

sels,  however,  gradually  becomes  equalized  (Fig.  92) ;  and 

the  network  becomes  connected  with  the  larger  trunks,  and 

bears  a  part  in  the  general  circulation. — Appearances  indica-       First  appearance  of 

tive  of  a  similar  process,  have  been  seen  in  the  tail  of  very     blood-vessels   in    the 

young  Tadpoles ;  so  that  it  may  probably  be  regarded  as  the     vascular  layer  of  the 

general  method,  by  which  new  capillaries  are  formed  in     germinal  membrane  of 

the  natural  process   of  growth.     Observations   upon   the     ?  Fowl at  the  3fith  hour 

history  of  the  operations,  which  are   performed   for  the     ofincubatkm- 


192  ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 

repair  of  injuries,  lead  to  precisely  the  same  conclusions.  The  first  appear- 
ance of  the  vascular  network  in  the  newly-forming  tissue,  is  in  the  form  of 
transparent  arborescent  streaks  ;  which  push  out  extensions  on  all  sides  ;  these 
encounter  one  another,  and  form  a  complete  series  of  capillary  reticulations, 
some  of  which  come  into  connection  with  the  vessels  of  the  surrounding  parts. 
According  to  the  observations  of  Mr.  Travers,*  isolated  corpuscles  enter  these 
newly-formed  capillaries,  and  perform  an  oscillating  movement  in  them  for 
some  hours,  before  any  series  of  them  passes  into  it ;  so  that  we  cannot  re- 
gard the  new  channel  as  burrowed  out  by  a  string  or  file  of  red  corpuscles, 
pushed  forth  from  the  nearest  capillary  by  vis  a  tergo,  as  some  have  main- 
tained. 

11.  Compound  Tubular  Tissues. 

223.  There  now  remain  to  be  described  two  elements  of  the  Animal  fabric, 
to  which  there  is  scarcely  anything  that  bears  the  least  analogy  in  the  struc- 
ture of  Plants  ; — namely,  the  Muscular  and  Nervous  tissues.     We  have  seen 
that,  putting  aside  the  Simple  Fibrous  tissues,  whose  function  is  purely  me- 
chanical, the  Animal  fabric,  so  far  as  we  have  yet  passed  its  elements  under 
review,  is  constructed  upon  the  very  same  type  with  that  of  Plants ;  all  the 
parts  actively  concerned  in  the  processes  of  nutrition,  secretion,  reproduction, 
&c.,  retaining  their  original  cellular  character ;  the  vessels  that  serve  for  the 
conveyance  of  fluid,  having  their  origin  in  cells,  whose  cavities  have  coalesced  ; 
whilst  the  more  solid  portions  of  the  frame- work  are  made  up  of  united  cells, 
whose  cavities  are  occupied  by  internal   deposit. — Now  the  purpose   of  the 
Muscular  and  Nervous  system  is  entirely  different.     The  former  is  the  one, 
by  which  all  the  sensible  movements  of  the  body  are  immediately  effected  ; 
and  it  is  only  amongst  a  small  number  of  Plants,  that  any  such  movements 
are  exhibited.     The  latter  serves  as  the  instrument  by  which  sensations  are 
received ;  and  by  which  the  instincts,  emotions,  or  volitions,  excited  by  these 
sensations,  act  upon  the   muscles  : — a  class  of  functions  which  we  have  no 
reason  whatever  to  regard  as  performed  by  Plants.     In  fact,  as  already  pointed 
out  (§  1 — 4),  the   distinction   between  the  two   kingdoms   is  more  properly 
founded  upon  the  presence  of  these  functions  and  of  their  instruments  in  the 
Animal,  and  upon  their  absence  in  the  Plant,  than  upon  any  other  structural 
character. 

224.  Now  it  might  have  not  been  unreasonable  to  expect,  that  tissues  alto- 
gether so  dissimilar  in  their  properties,  and  in  the  purposes  to  which  they  are 
destined,  should  have  a  structure  departing  widely  from  the  type  of  the  simple 
Cell.     Yet  it  does  not  appear  that  this  is  the  case.     That  portion  of  the  Nerv- 
ous matter,  by  which  its  most  active  functional  changes  are   effected,  retains 
its  original  cellular  character   without  alteration ;    and  the   so-called  fibres, 
which  constitute  the  Nerve-trunks,  and  which  convey  the  influence  of  these 
changes,  are  in  reality  tubes,  formed  as  it  would  seem  by  the  coalescence  of 
a  linear  series  of  cells,  and   chiefly  distinguished   by  the  peculiar  nature  of 
their  internal  deposit.     In  like  manner,  we  shall  find  that  the  ultimate  Mus- 
cular Fibre  is  also  a  tube,  formed  out  of  the  same  elements,  and  distinguished 
by  the  nature  of  its  contents ;  which,  in  the  most  perfect  form  of  the  tissue, 
are  composed  of  linear  series  of  extremely  minute  secondary  cells. 

225.  Muscular  tissue  exists  under  two  forms  ;  one  in  which  the  ultimate 
fibres  are  marked  by  transverse  striae ;  and  the  other  in  which  they  are  plain 
or  unstriped.    The  former  is  chiefly  employed  in  performing  the  various  move- 
ments, which  are  effected  through  the  agency  of  the  Nervous  system,  and  which 

*  Physiology  of  Inflammation  and  the  Healing  Process. 


STRIATED  MUSCULAR  FIBRE. 


193 


Fig.  93. 


are  connected  with  the  peculiarly  Animal  powers  of  the  being.  The  latter  is 
with  difficulty  called  into  action  through  the  nervous  system,  but  is  much 
more  readily  excited  by  stimuli  applied  to  itself;  and  this  is  employed  to  per- 
form various  movements,  which  are  more  immediately  concerned  in  the  Vege- 
tative or  organic  functions.* 

226.  When  we  examine  an  ordinary  Muscle  (from  one  of  the  extremities, 
for  example)  with  the  naked  eye,  we  observe  that  it  presents  a  fibrous  ap- 
pearance ;  and  that  the  fibres  are  arranged  with  great  regularity,  in  the  direc- 
tion in  which  the  muscle  is  to  act.  Upon  further  examination  it  is  found, 
that  these  fibres  are  arranged  in  fasciculi  or  bundles  of  larger  or  smaller  size, 
connected  by  means  of  areolar  tissue ;  and  when  the  Microscope  is  applied  to 
the  smallest  fibre  which  can  be  seen  with  the  naked  eye,  it  is  seen  itself  to 
consist  of  a  fasciculus,  composed  of  a  number  of  cylindrical  fibres  lying  in  a 
parallel  direction,  and  closely  bound  to- 
gether. These  primitive  fibres  present 
two  sets  of  markings  or  stride;  one  set 
longitudinal, — the  other  transverse  or 
annular.  By  more  closely  examining 
these  fibres,  when  separated  from  each 
other,  it  is  frequently  seen  that  each  may 
be  resolved  into  fibrillse,  by  the  splitting 
of  its  contents  in  a  longitudinal  direction, 
as  shown  in  Fig.  93.  These  fibrillae  have 
a  peculiar  beaded  appearance,  which  will 
be  presently  noticed  more  particularly. — 
It  not  unfrequently  happens,  however,  that 
when  a  fibre  is  drawn  apart,  its  contents 
separate  in  the  direction  of  the  transverse  stria3 ;  forming  a  series  of  discs,  as 
shown  in  Figs.  94  and  95.  This  cleavage  is  just  as  natural  as  the  former, 
though  less  frequent;  and  it  leads  us  to  a  view  of  the  composition  of  Muscu- 
lar Fibre,  somewhat  different  from  the  one  commonly  adopted.  To  use  the 

Fig.  94. 


Fasciculus  of  Fibres  of  Voluntary  Muscle; 
the  fibres  separated  at  one  end,  into  brush- 
like  bundles  of  fibrillae. 


Portion  of  Human  Muscular  fibre,  separating  into  discs,  by  cleavage  in  direction  of  transverse  striae. 

words  of  Mr.  Bowman,t  it  would  be  as  proper  to  say,  "that  the  fibre  is  a  pile 
of  discs,  as  that  it  is  a  bundle  of fibrillse  ;  but  in  fact  it  is  neither  the  one  nor 
the  other,  but  a  mass  in  whose  structure  there  is  an  intimation  of  the  existence 
of  both,  and  a  tendency  to  cleave  in  the  two  directions.  If  there  were  a  gene- 
ral disintegration  along  all  the  lines  in  both  directions,  there  would  result  a 

*  By  some,  the  two  classes  have  been  spoken  of  as  those  of  Voluntary  and  Involuntary 
muscles;  but  this  distinction  is  not  correct;  since  every  muscle  ordinarily  termed  voluntary, 
may  be  called  into  action  involuntarily. 

t  See  Bowman  on  the  Minute  Structure  and  Movements  of  Voluntary  Muscle;  in  Phil. 
Trans.  1840. 

17 


194 


ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 


series  of  particles,  which  may  be  termed  primitive  particles  or  sarcous  ele- 
ments, the  union  of  which  constitutes  the  mass  of  the  fibre.    These  elementary 

[Fig.  95. 


Fragments  of  Striped  Elementary  Fibres,  showing  a  cleavage  in  opposite  directions ;  magnified  300 
diameters;  1,  longitudinal  cleavage;  the  longitudinal  and  transverse  lines  are  both  seen;  some  longitu- 
dinal lines  are  darker  and  wider  than  the  rest,  and  are  not  continuous  from  end  to  end ;  this  results  from 
partial  separation  of  the  fibrillae;  6,  fibriHee,  separated  from  one  another  by  violence  at  the  broken  end 
of  the  fibre,  and  marked  by  transverse  lines  equal  in  width  to  those  on  the  fibre  ;  7,  8  represent  two  ap- 
pearances commonly  presented  by  the  separated  single  fibrilla,  (more  highly  magnified;)  at  7 the  borders 
and  transverse  lines  are  all  perfectly  rectilinear,  and  the  included  spaces  perfectly  rectangular;  at  8  the 
borders  are  scalloped,  the  spaces  bead-like ;  when  most  distinct  and  definite,  the  fibrilla  presents  the 
former  of  these  appearances ;  2,  transverse  cleavage  ;  the  longitudinal  lines  are  scarcely  visible ;  3,  in- 
complete fracture  following  the  opposite  surfaces  of  a  disc,  which  stretches  across  the  interval  and  re- 
tains the  two  fragments  in  connection ;  the  edge  and  surface  of  this  disc  are  seen  to  be  minutely  granular, 
the  granules  corresponding  in  size  to  the  thickness  of  the  disc,  and  to  the  distance  between  the  faint 
longitudinal  lines;  4,  another  disc  nearly  detached;  5,  detached  disc  more  highly  magnified,  showing  the 
sarcous  elements.] 


Fig.  96. 


particles  are  arranged  and  united  together  in  the  two  directions.  All  the  re- 
sulting discs,  as  well  as  fibrillae,  are  equal  to  one  another  in  size ;  and  con- 
tain an  equal  number  of  particles.  The  same  particles  compose  both.  To 
detach  an  entire  fibrilla,  is  to  abstract  a  particle  of  every  disc;  and  vice  versa." 
227.  The  elements  of  Muscular  Fibre  are  bound  together,  in  the  perfect 
condition  of  the  fibre,  by  a  very  delicate  tubular  sheath.  This  cannot  always 
be  readily  brought  into  view ;  but  it  is  occasionally  seen  with  great  distinct- 
ness :  thus,  when  the  two  ends  of  a  fibre  are  drawn  apart,  its  contents  will 

sometimes  separate  without  the  rupture 
of  the  sheath,  which  then  becomes  evi- 
dent ;  and  this,  during  the  act  of  con- 
traction, may  sometimes  be  observed 
to  rise  up  in  wrinkles  upon  the  surface 
of  the  fibre,  as  seen  in  Fig.  100.  This 
sheath  is  quite  distinct  from  the  areolar 
tissue,  which  binds  the  fibres  into  fasci- 
culi; and  it  has  been  termed,  for  the 
sake  of  distinction,  the  Myolemma.  Its  existence  may  be  demonstrated  in 
any  Muscular  fibre,  by  subjecting  it  to  the  action  of  fluids,  which  occasion  a 
swelling  of  its  contents  ;  this  is  especially  the  effect  of  acids  and  alkalies,  and 
may  be  well  produced  by  the  citric  and  tartaric  acids,  and  by  potash.  For  a 
time,  the  Myolemma  yields  to  the  distention  which  takes  place  from  within ; 
but  at  last  it  bursts  at  particular  points,  and  a  sort  of  hernia  of  its  contents 
takes  place,  making  the  existence  of  a  perfect  envelope  in  all  other  parts  quite 


Fibre  of  Human  Muscle  broken  across;  the 
fragments  connected  by  the  untorn  Myolemma. 


STRIATED  MUSCULAR  FIBRE.  195 

evident.  This  membrane  is  itself  perfectly  transparent,  and  has  nothing  to  do 
with  the  production  of  either  the  longitudinal  or  the  transverse  striae.  There  is 
no  reason  to  believe  that  it  is  perforated  either  by  nerves  or  by  capillary  ves- 
sels ;  in  fact  it  seems  to  be  an  effectual  barrier  between  the  real  elements  of 
Muscular  structure,  and  the  surrounding  parts.  That  it  has  no  share  in  the 
contraction  of  the  fibre,  is  evident  from  the  fact  just  mentioned,  respecting  the 
condition  which  it  occasionally  presents  when  the  fibre  is  much  shortened. 

228.  Muscular  Fibres  are  commonly  described  as  cylindrical ;  but  there  is 
reason  to  believe  that  they  are  rather  of  a  polygonal  form,  their  sides  being 
flattened  against  those  of  adjoining  fibres  (Fig.  97).  In  some  instances  the 
angles  are  sharp  and  decided ;  in  others  they  are  rounded  off,  so  as  to  leave 
spaces  between  the  contiguous  fibres  for  the  passage  of  vessels.  In  Insects, 
the  fibres  often  present  the  form  of  flattened  bands.  The  average  diameter  of 
the  fibres  in  Man  maybe  stated  at  about  l-400th  of  an  inch;  being  somewhat 
greater  than  this  in  the  Male,  and  less  in  the  Female.  Their  size  varies  con- 
siderably, however,  in  different  classes  of  animals ;  and  even  in  the  same  ani- 
mal, and  the  same  muscle.  The  following  table  gives  illustrations  of  these 
varieties;  the  extremes  are  those  met  with  by  Mr.  Bowman  himself;  but 
other  observers  speak  of  dimensions  more  widely  separated. 

Fractions  of  an  inch. 

*»»""  j"±te  :  :  ;  ±  E  t 

MAMMALU     .     ^   •;•;;••    •  «W    £   ij, 

Mole j^j  to    T{F 

Mouse ?J-F 

Owl T7,iff?r  to 

BIRDS    . 

REPTILES 


FISH 


INSECTS 


Chaffinch ^  to    ^ 

Heron T^  to    TTTIF 

Fro? ToVir  to    sffs- 

Lizard ^ 

Boa *i*  to    T£, 

Skate ^  to      & 

Cod         ....'....       Tjjg-  tO 

Sprat    , ^^  to 

Staghorn  Beetle      ....    5£y  to 

Blue-bottle  Fly 7£y  to 


f 


4UT 


It  is  interesting  to  remark,  upon  this  table,  that  the  Muscular  Fibre  of  Rep- 
tiles and  Fishes  is  upon  the  whole  much  larger  than  that  of  other  Vertebrata, 
and  that  its  dimensions  present  the  greatest  extremes  of  variation ;  whilst  in 
Birds,  it  is  much  smaller  than  in  all  other  Vertebrata,  and  its  dimensions  are 
also  less  variable.  Further,  the  size  of  the  fibres  bears  no  proportion  to  that 
of  the  animal;  for  we  observe  that  in  the  Chaffinch  they  are  larger  than  in 
the  Owl,  in  the  Cat  larger  than  in  the  Horse,  and  in  the  Frog  often  larger 
than  in  the  Boa.  Moreover  in  Insects,  the  diameter  of  the  fibres  is  even 
greater  than  it  is  in  Mammalia. — The  average  distance  of  the  transverse  striae, 
in  the  muscular  fibre  of  different  animals,  is  very  nearly  uniform ;  as  will  be 
seen  from  the  following  table.  Between  the  extremes,  however,  there  is  con- 
siderable variation ;  and  this  will  be  presently  shown  to  depend  upon  the  con- 
dition of  the  muscle,  at  the  time  of  examination.  The  distance  is  not  only 
often  different  in  the  same  muscle  and  the  same  fasciculus,  but  even  in  the 
same  fibre  in  different  parts  of  its  length.  The  figures  indicate  the  number  of 
striae  in  l-1000th  of  an  inch.  The  extremes  in  the  same  specimen,  however, 
are  in  no  instance  so  widely  apart,  as  the  table  indicates  for  the  Class ;  the 


196 


ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 


greatest  proportion  between  the  maximum  and  minimum  being,  except  in  In- 
sects, as  2  to  1. 

Mean. 

9-4 
10-9 
104 
111 
11-1 

9-5 

229.  It  has  been  maintained  by  some,  that  each  Muscular  Fibre  is  a  hol- 
low bundle  of  fibrillae  ;  but  the  appearance  presented  by  transverse  sections 
proves  that  this  is  not  the  case,  the  whole  area  of  the  tube  being  occupied  by 
fibrillae,  without  any  trace  of  central  cavity.  The  extremities  of  the  cut  fibrillae, 
however,  cannot  always  be  distinguished  in  Mammalia,  in  consequence,  as  it 
would  seem,  of  their  close  and  intimate  lateral  union ;  but  they  are  very  evi- 

Fig.  97. 


Maximum. 

Minimum. 

Human 

.     15-0 

6-0 

Other  Mammalia     . 

.     15-0 

6-7 

Birds 

.     140 

7-0 

Reptiles 

.     20-0 

G-7 

Fish 

.     18-0 

7-5 

Insects 

.     16-0 

4-5 

Transverse  section  of  Muscular  fibres  from  pectoral  muscle  of  Teal ;  showing  the  irregular  form  of  the 
fibres,  and  the  aggregation  of  circular  particles,  with  which  they  are  completely  filled. 

dent  in  Birds,  Reptiles,  and  Fishes  (Fig.  97).  The  addition  of  an  acid  in- 
creases the  distinctness  of  the  fibrillae,  by  widening  the  interstices  between 
them. 

230.  When  the  fibrilla3  are  separately  examined,  they  are  found  to  present 
an  alternation  of  dark  and  light  spaces,  corresponding  with  the  transverse 
striae  of  the  fibre,  and  the  lighter  intervals  between  them.  It  is  this  alterna- 
tion, which  gives  to  the  fibrillae  the  beaded  appearance  they  present,  when 
their  outline  is  not  perfectly  seen.  When  good  specimens,  however,  are 
carefully  examined  under  a  sufficient  magnifying  and  good  defining  power,  it 
is  seen  that  the  border  of  the  fibrillae  is  straight  or  nearly  so ;  so  that  the 
beaded  appearance  is  an  optical  illusion.  Moreover,  each  of  the  light  spaces 
is  seen  to  be  crossed  by  a  delicate  but  distinct  line,  separating  it  into  two 
equal  parts;  and -upon  attentive  examination  it  is  seen,  that  a  transparent 
border,  equal  in  breadth  to  either  of  these  parts,  is  seen  at  the  sides,  as  well 
as  between  the  ends,  of  the  dark  spaces.  Thus  each  dark  space  is  completely 
surrounded  by  this  pellucid  border ;  and  it  can  scarcely  be  doubted  that  the 
whole  constitutes  a  complete  though  minute  cell,  and  that  the  entire  fibrilla 


STRIATED  MUSCULAR  FIBRE. 


197 


Fig.  99. 


7> 


Fragment  of  Muscular  fibre 
from  macerated  heart  of  Ox, 
showing  formation  of  strise  by 
the  aggregation  of  fibrillse. 


I 


is  made  up  of  a  linear  aggregation  of  such  cells.*  When  the  fibril  is  in  a 
state  of  relaxation,  as  seen  at  «,  the  diameter  of  the  cells  is  greatest  in  the 
longitudinal  direction  ;  but  when  it 
is  contracted,  the  fibril  increases  in 
diameter  as  it  diminishes  in  length ; 
so  that  the  transverse  diameter  of 
each  cell  equals  or  even  exceeds  the 
longitudinal  diameter,  as  seen  at  b. 
The  difference  between  the  two 
states  is  frequently  much  more  strik- 
ing than  is  represented  in  the  figure. 
— Thus  the  act  of  Muscular  contrac- 
tion seems  to  consist  in  a  change  of 

form  in  the  cells  of  the  ultimate  fibrillae,  consequent  upon  an 
attraction  between  the  walls  of  their  two  extremities,  or  per- 
haps between  their  nuclei;  and.it  is  interesting  to  observe 
how  very  closely  it  thus  corresponds  with  the  contraction  of 
certain  Vegetable  tissues,  of  which  the  component  cells  change 
their  form  when  irritated,  and  thus  produce  a  movement  (§  1). 
The  essential  difference,  therefore,  between  the  striated  mus- 
cular tissue  of  Animals,  and  the  contractile  tissues  of  Plants, 
consists  in  the  subjection  of  the  former  to  nervous  influence. 
— The  diameter  of  the  ultimate  fibrillae,  and  the  length  of  the 
component  cells,  will  of  course  vary  according  to  the  contract-  St 

,          ,  T  •  r-    i       /*i  i      .   -u  >L-          •  ultimate fibrillae of 

ed  or  relaxed  condition  of  the  fibre ;  but  they  otherwise  seem 
to  be  tolerably  uniform  in  different  animals.  The  average 
diameter  may  be  stated  at  about  l-10,000th  of  an  inch;  but 
it  has  been  observed  as  high  as  l-5000th,  and  as  low  as  1- 
20,000th,  even  when  not  put  upon  the  stretch.  The  length  of 
the  component  cells  corresponds,  of  course,  to  the  distance  of 
the  striae  on  the  entire  fibre  ;  and  this  also  has  been  just  shown 
to  average  about  1-1 0,000th  of  an  inch. 

231.  The  general  opinion  as  to  the  disposition  of  the  fibres  during  the  con- 
traction of  Muscle,  has  been,  until  lately,  that  of  Prevost  and  Dumas,  who 
stated  that  they  were  thrown  into  a  sinuous  or  zig-zag  flexure.  Recent  ob- 
servations, however,  have  fully  demonstrated  the  incorrectness  of  this  view ; 
the  improbability  of  which  might  have  been  suspected  from  the  consideration, 

*  This  account  of  the  ultimate  structure  of  Muscular  Fibre  was  first  published  simulta- 
neously (March,  1846),  by  the  Author  of  this  Treatise,  in  his  Manual  of  Physiology,  and  by 
Dr.  Sharpey,  in  his  new  edition  of  Dr.  Quain's  Anatomy.  Both  of  these  statements,  which 
were  completely  independent  of  each  other,  were  founded  upon  the  examination  of  the  very 
beautiful  preparations  of  Muscular  Fibre,  made  by  Mr.  Lealand  the  Optician  ;  who  appears 
to  have  been  the  first  to  direct  attention  to  the  transverse  line  dividing  the  bright  space,  and 
to  the  bright  border  edging  the  dark  spot.  A  similar  delineation  had  previously  been  pub- 
lished, however,  by  Dr.  Goodfellow  (Physiological  Journal,  No.  IV.)  ;  but  his  interpretation 
of  the  appearances  was  altogether  different;  for  he  considered  the  dark  spaces  as  the  "  sar- 
cous  elements"  of  Mr.  Bowman,  and  regarded  them  as  separately  inclosed  within  partitions 
formed  by  internal  prolongations  of  the  general  investing  Myolemma.  By  Mr.  Erasmus 
Wilson,  again,  the  appearances  were  described  as  leading  to  the  belief  that  two  kinds  of 
cells  exist  in  each  fibrilla,  a  dark  and  a  light ;  a  pair  of  light  cells,  separated  by  the  delicate 
transverse  line  just  spoken  of,  being  interposed  between  each  pair  of  dark  ones  [System  of 
Anatomy,  3d  Am.  Edit,  p.  183].  The  bright  edging  to  the  dark  spots  was  overlooked  by 
him.  The  view  taken  by  Dr.  Sharpey  and  the  Author  has  the  entire  concurrence  of  several 
of  the  most  eminent  Microscopists  in  London  and  elsewhere;  and  it  is  confirmed  by  the 
remarkable  similarity  between  the  aspect  of  the  Muscular  fibrilla,  and  that  of  a  minute  Con- 
ferva, seen  under  the  same  magnifying  power, — the  cellular  constitution  of  the  latter  being 
indubitable. 

17* 


striated  muscular 
fibre  :— a,  a  fibril 
in  a  state  of  ordi- 
nary relaxation ; 
6,  a  fibril  in  a  state 
of  partial  contrac- 
tion. 


198          ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 

that  fibres  in  this  state  of  flexure  could  scarcely  be  imagined  to  be  exerting 
any  force  of  traction.  Prof.  Owen  has  noticed  that,  in  the  contracted  state  of 
the  very  transparent  muscles  of  some  Entozoa,  each  separate  fibre,  which 
may  be  seen  with  great  distinctness,  presents  a  knot  or  swelling  in  the  middle, 
besides  being  generally  thickened ;  but  that  it  is  simply  shortened,  without 
falling  out  of  the  straight  line.  Dr.  A.  Thomson  remarked  the  same  thing  in 
the  Frog;  single  fibres,  whilst  continuing  in  contraction,  being  simply  short- 
ened, without  falling  into  zig-zag  lines:  and  he  was  led  to  suspect,  from  this 
and  other  circumstances,  that  the  zig-zag  arrangement  was  not  produced,  until 
the  act  of  contraction  had  ceased.  The  recent  inquiries  of  Mr.  Bowman 
have  proved  most  satisfactorily,  that,  in  the  state  of  contraction,  there  is  an 
approximation  of  the  transverse  stria3,  and  a  general  shortening  of  the  fibre ; 
and  that  its  diameter  is  at  the  same  time  increased;  but  that  it  is  never  thrown 
out  of  the  straight  line,  except  when  it  has  ceased  to  contract,  and  its  two 
extremities  are  still  held  in  proximity  by  the  contraction  of  other  fibres.  The 
whole  process  may  be  distinctly  seen  under  the  Microscope,  in  a  single  fibre 
isolated  from  the  rest :  it  is,  of  course,  desirable  to  select  the  specimen  from 
those  animals,  in  which  the  contractility  of  the  Muscle  is  retained  for  the 
longest  period  after  death, — which  is  particularly  the  case  in  Reptiles  among 
Vertebrata,  and  in  most  Invertebrata  (Mr.  Bowman  particularly  recommends 
the  Crab  and  Lobster) ;  but  the  change  has  been  fully  proved  to  differ  in  no 
essential  degree,  in  the  warm-blooded  Vertebrata.  The  contraction  usually 
commences  at  the  extremities  of  the  fibre;  but  it  frequently  occurs  also  at  one 
or  more  intermediate  points.  The  first  appearance  is  a  spot  more  opaque 
than  the  rest,  caused  by  the  approximation  of  a  few  of  the  dark  points  of 
some  of  the  fibrilla3 :  this  spot  usually  extends  in  a  short  time  through  the 
whole  diameter  of  the  fibre ;  and  the  shading,  caused  by  the  approximation 
of  the  transverse  striae,  increases  in  intensity.  The  stria?  are  found  to  be 
two,  three,  or  even  four  times  as  numerous,  in  the  contracted,  as  in  the  un- 
contracted  part ;  and  are  also  .proportionally  narrower  and  more  delicate. 
The  line  of  demarcation  between  the  contracted  and  uncontracted  portions  is 
well  defined;  but,  as  the  process  goes  on,  fresh  stria3  are  absorbed  (as  it 
were)  from  the  latter  into  the  former.  The  contracted  part  augments  in  thick- 
ness ;  but  not  in  a  degree  commensurate  with  its  diminished  length  ;  so  that 
its  solid  parts  lie  in  smaller  compass  than  before, — the  fluid  which  previously 
intervened  between  them,  being  pressed  out  in  bullae  under  the  myolemma 
(Fig.  100).  The  force  with  which  the  elements  of  the  fibre  thus  tend  to  ap- 
proximate is  evidently  considerable ;  for  if  the  two  extremities  be  held  apart, 

Fig.  100. 


Muscular  fibre  of  Dytiscus,  contracted  in  the  centre;  the  striae  approximated  ;  the  breadth  of  the  fibre 
increased  ;  and  the  sarcolemma  raised  in  bullae  on  its  surface. 

the  fibre  is  not  unfrequently  ruptured.  This  corresponds  with  the  appear- 
ances found  in  the  muscles  of  persons  who  have  died  from  tetanus ;  for  in 
the  ruptured  fibres  of  those  muscles,  which  have  been  the  subjects  of  the 
spasmodic  action,  the  striae  have  been  observed  to  approximate  so  closely, 
as  to.be  scarcely  distinguishable.  When  the  contraction  is  not  very  decided, 
the  dark  and  elevated  spot  appears  to  play  like  a  wave  along  the  fibre,  before 
it  involves  the  whole  diameter  in  any  part  (Fig.  101,  2) ;  and  even  when  con- 


STRIATED  MUSCULAR  FIBRE. 


199 


Fig.  101, 


3 


siderable  traction  is  being  exercised,  there  is  continual  interchange  in  the  ele- 
ments by  which  it  is  effected, — the  discs  at  one  end  of  the  contracted  part 
receding  from  each  other,  whilst  at  the  other  end  new  discs  are  being  re- 
ceived into  it. 

232.  The  foregoing  description  is  chiefly 
derived   from   the  appearances  presented  by 
muscular  fibre,  when  spontaneously  passing 
into  that  state  of  contraction,  which  is  termed 
the  rigor  mortis  ;  but  there  can  be  no  rea- 
sonable doubt,  that  the  phenomena  of  con- 
traction, excited  by  the  agency  of  the  nerves, 
are  precisely  similar.     Mr.  Bowman  has  re- 
marked, that  stimuli  of  various  kinds,  direct- 
ly applied  to  them,  produce  corresponding 
effects,  although,  in  the  case  of  galvanism, 
the  change  is  too  rapid  for  its  steps  to  be 
followed ;  and   that,  from    the    appearances 
presented  by  muscles  which  have  been  af- 
fected with  tetanic  spasms,  the  contraction 
produced  by  nervous  agency  may  be  inferred 
to  correspond  in  character. — It  now  remains, 
therefore,  to  inquire  what  is  the  cause  of  the 
zig-zag  arrangement,  which  is  often  seen  in 
the  fibres.     This  may  be  easily  produced,  by 
approximating  the  ends  of  a  fasciculus,  after 
the  irritability  of  its  fibres  has  ceased  ;  and 
it  would  not  seem  unlikely,  that  the  passage 
of  vessels   or  nerves   should   determine  the 
points    at    which    the    flexures    take    place. 
Hence  it  appears,  that  the  sinuous  or  zig-zag 
arrangement  is    that   into  which   fibres    are 
naturally  thrown,  if,  on  elongation  following 

contraction,  they  are  not  at  once  stretched  by  antagonist  muscles,*  Many 
facts  support  the  opinion,  which  has  long  been  held  by  several  Physiologists, 
that,  when  an  entire  muscle  is  contracting,  all  its  fasciculi  are  not  in  con- 
traction at  once  ;  but  that  there  is  a  continual  interchange  in  the  parts, 
by  which  the  tension  is  effected ;  some  relaxing,  whilst  others  are  short- 
ening. When  the  ear  is  applied  to  a  muscle  in  vigorous  action,  an  exceed- 
ingly rapid  faint  silvery  vibration  is  heard ;  which  seems  to  be  attributable  to 
this  constant  movement  in  its  substance.  Now,  on  examining  a  muscle,  of 
which  some  fasciculi  present  the  zig-zag  arrangement,  others  will  be  seen  (if 
the  two  extremities  have  not  been  purposely  approximated)  to  be  quite  straight, 
and  in  a  state  of  contraction ;  and  it  thence  appears,  that  the  former  appear- 
ance is  presented  by  bundles  of  fibres,  which  have  either  not  yet  entered  into 
contraction,  or  which  have  relaxed  after  undergoing  it ;  but  of  which  the  ex- 
tremities are  still  approximated,  by  the  agency  of  other  contracting  fibres. — 
The  result  of  various  experiments  made  for  the  purpose,  leads  to  the  conclu- 
sion, that  the  total  bulk  of  a  muscle  in  contraction  is  not  less  than  when  it  is 
in  a  relaxed  state  ;  or  that  the  difference,  if  any  exist,  is  extremely  trifling. 

233.  Every  Muscular  Fibre,  of  the  striated  kind  at  least,  is  attached  at  its 
extremities  to  white  fibrous  tissue  ;  through  the  medium  of  which  it  exerts  its 
contractile  power  on  the  bone  or  other  substance,  which  it  is  destined  to  move. 


Muscular'fibre  of  Skate,  in'a  state  of 
rest  (1),  and  in  three  different  stages  of 
contraction  (2,  3,  4). 


*  Mr.  Bowman's  conclusions  have  recently  been  confirmed  by  Prof.  E.  Weber.    (Archives 
d' Anatomic  Generate,  Jan.  1846.) 


200 


ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 


The  whole  fasciculus  of  fibrillae  usually  seems  to  end  abruptly  in  a  perfect 
disk  ;  and  the  myolemma  terminates  there.  The  tendinous  fibres  are  attached 
to  the  whole  surface  of  the  disk;  and  probably  become  continuous  with  the 

Fig.  102. 


Attachment  of  Tendon  to  Muscular  Fibre,  in  Skate. 


myolemma.  Thus  the  whole  muscle  is  penetrated  by  minute  fasciculi  of  tendi- 
nous fibres  ;  and  these  collect  at  its  extremities  into  a  Tendon.  Sometimes  the 
muscular  fibres  are  attached  obliquely  to  the  tendon,  which  forms  a  broad 
band  that  does  not  subdivide  ;  this  is  seen  in  the  legs  of  Insects  and  Crusta- 
cea, in  which  the  muscular  fibres  have  apenniform  arrangement;  being  inserted 
into  the  tendon,  on  either  side,  like  the  laminae  of  a  feather  into  its  stem. 

234.  The  Muscular  Fibre  of  Organic  Life  is  very  different  from  the  pre- 
ceding.    It  consists  of  a  series   of  tubes,  which  do  not  present  transverse 


Fig.  103. 


[Fig.  104.] 


Non-striated  Muscular  Fibre;  at 
ft,  in  its  natural  state  ;  at  a,  show- 
ing the  nuclei  after  the  action  of 
acetic  acid. 


4,  A  muscular  fibre 
of  Organic  Life  with 
two  of  its  nuclei ; 
taken  from  the  uri- 
nary bladder,  and 
magnified  600  diam- 
eters ;  5,  muscular 
fibre  of  organic  life 
from  the  stomach, 
magnified  the  same.] 


strife,   and   in  which  the  longitudinal  striae   are  very  faint ;  these  tubes  are 
usually  much  flattened,  and  cannot  be  shown  to  contain   distinct  fibrillee. 


NON-STRIATED  MUSCULAR  FIBRE.  201 

Their  size  is  usually  much  less  than  that  of  the  fibres  of  Animal  life  ;  but, 
owing  to  the  extreme  variation  in  the  flattening  which  they  undergo,  it  is  dif- 
ficult to  make  a  precise  estimate  of  their  dimensions.  Those  of  the  aliment- 
ary canal  are  stated  by  Dr.  Baly  to  measure  from  about  the  1 -2500th  to  the 
l-5600th  of  an  inch;  in  the  foot  of  the  common  Mussel,  the  Author  has 
found  them  to  be  as  much  as  the  1 -1920th  of  an  inch ;  whilst  in  the  respira- 
tory sac  of  a  Phallusia  (an  Ascidian  Mollusk),  their  diameter  is  no  more  than 
1 -8400th.  They  sometimes  present  markings,  which  indicate  a  granular  ar- 
rangement in  their  interior  ;  and  these  markings  have  occasionally  a  degree 
of  regularity,  which  approaches  that  of  the  striae  on  the  striped  Muscular  fibres. 
They  frequently  present  nodosities  at  intervals,  which  are  the  nuclei  of  their 
original  component  cells  ;  and,  where  these  nuclei  are  not  otherwise  visible, 
they  may  be  brought  into  sight  by  acetic  acid  (Fig.  103,  a).  The  plain  or 
non-striated  fibres,  like  those  of  the  other  muscles,  are  usually  arranged  in  a 
parallel  manner,  into  bands  or  fasciculi ;  but  these  fasciculi  are  generally  in- 
terwoven into  a  net-work,  not  having  any  fixed  points  of  attachment,  but  con- 
tracting against  each  other.  It  is  of  this  kind  of  structure,  that  the  muscular 
substance  of  the  walls  of  the  oesophagus,  stomach,  intestinal  tube,  bladder, 
and  uterus,  is  composed ;  it  occurs  also  in  the  bronchial  tubes,  in  the  ureters, 
and  most  of  the  larger  gland-ducts,  and  in  the  irjs.  In  the  Heart,  are  found 
various  forms  of  Muscular  fibre ;  some  being  distinctly  striated,  others  quite 
plain ;  and  others  of  intermediate  character.  The  average  size  of  the  fibres 
is  less  than  that  of  the  fibre,  of  which  the  voluntary  muscles  are  composed ; 
and  the  fasciculi,  instead  of  being  straight  and  parallel,  are  considerably  in- 
terlaced. This  intermediate  character  accords  well,  as  we  shall  hereafter  see, 
with  the  actions  of  the  organ  ;  which  correspond  in  their  energy  and  rapidity, 
with  the  contractions  of  voluntary  muscles  ;  whilst  they  agree  with  those  of 
the  non-striated  kind,  in  being  but  little  influenced  by  the  nervous  system. 
The  middle  coat  of  the  Arteries  contains  a  contractile  tissue,  very  similar  to 
that  of  unstriped  muscle ;  and  fibres  of  a  similar  nature  are  interwoven  with 
other  fibrous  tissues  in  the  Skin,  and  especially  in  the  Dartos, — giving  rise  in 
the  former  to  the  state  termed  cutis  anserina,  under  the  influence  of  cold  or 
of  depressing  emotions  ;  and  in  the  latter  to  the  wrinkling  of  the  scrotum. 
There  are  certain  points,  at  which  the  one  system  of  fibres  comes  into  close 
connection  with  the  other.  This  is  the  case,  for  example,  in  the  oesophagus; 
the  upper  part  of  which  contains  striated  fibres,  and  is  thrown  into  contrac- 
tion by  nerves  ;  whilst  the  muscular  wall  of  the  lower  part  seems  entirely 
composed  of  non-striated  fibres,  and  acts  for  the  most  part  independently  of 
the  nerves.  The  point  of  transition  varies  in  different  animals  (§  386) ;  and 
seems  not  to  be  constant  among  individuals  of  the  human  species. 

235.  The  Myolemma  of  the  Muscular  Fibre  appears  to  be  the  part  first 
formed  ;  being  distinctly  visible  long  before  any  traces  of  fibrillaB  can  be  ob- 
served in  it.  This  tube  seems  to  take  its  origin,  like  the  ducts  of  Plants,  in 
cells  laid  end  to  end,  the  cavities  of  which  coalesce,  by  the  disappearance  of 
the  partitions,  at  a  subsequent  period  ;  and  the  nuclei  of  these  original  cells 
may  be  distinctly  seen,  for  some  time  after  the  appearance  of  the  striae,  which 
indicate  the  formation  of  the  fibrillae  in  their  interior.  In  an  early  stage  of 
the  development  of  the  fibres,  indeed,  these  bodies  project  considerably  from 
their  sides  :  in  this  respect,  as  well  as  in  others,  there  is  a  close  correspond- 
ence between  the  temporary  character  of  the  Muscular  fibre  of  Animal  life, 
and  the  permanent  condition  of  that  of  Organic  life.  In  the  fully  formed 
muscle  of  Animal  life,  they  are  not  perceptible,  except  when  a  peculiar  me- 
thod has  been  adopted  for  bringing  them  into  view.  This  method  consists  in 
treating  the  fibre  with  weak  acids,  which  render  the  nuclei  more  opaque, 
whilst  the  surrounding  structure  becomes  more  transparent.  They  are  usually 


202 


ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 


numerous  in  proportion  to  the  size  of  the  fibre.     There  is  every  probability 
that  these  nuclei  continue  to  act,  like  the  "  germinal  spots"  of  the  glandular 


Fig.  105. 


Fig.  106. 


Muscular  fibres  from  foetal  pectoral  is  ; 
A,  from  Calf  at  two  months ;  B,  from  hu- 
man foetus  of  nine  months. 


Mass  of  ultimate  fibres  from 
the  pectoralis  major  of  the  hu- 
man fetus,  at  nine  months. 
These  fibres  have  been  im- 
mersed in  a  solution  of  tartaric 
acid ;  and  their  "  numerous  cor- 
puscles, turned  in  various  direc- 
tions, some  presenting  nucle- 
oli,"  are  shown. 


follicles  or  parent-cells,  as  centres  of  nutrition  ;  from  which  the  minute 
secondary  cells,  that  compose  the  fibrillae,  are  developed  as  they  are  re- 
quired. The  diameter  of  the  Muscular  fibre  of  the  foetus  is  not  above  one- 
third  of  that  which  it  possesses  in  the  adult ;  and  as  the  size  of  their  ultimate 
particles  is  the  same  in  both  cases,  their  number  must  be  greatly  multiplied 
during  the  growth  of  the  structure.  But  we  shall  find  reason  to  believe,  that 
a  decay  is  continually  taking  place  in  the  component  cells,  with  a  rapidity 
proportional  to  the  functional  activity  of  the  Muscle,  and  their  generation, 
which  occurs  as  constantly  when  the  nutrient  operations  proceed  in  their 
regular  course,  is  probably  accomplished  by  a  development  from  these  cen- 
tres, at  the  expense  of  the  blood,  with  which  the  muscle  is  copiously  supplied. 

236.  From  the  preceding  history  it  appears,  that  there  is  no  difference,  at 
an  early  stage  of  development  between  the  striated  and  non-striated  forms  of 
Muscular  fibre.    Both  are  simple  tubes,  containing  a  granular  matter,  in  which 
no  definite  arrangement  can  be  traced,  and  presenting  enlargements  occasioned 
by  the  presence  of  the  nuclei.     But  whilst  the  striated  fibre  goes  on  in  its 
development,  until  the  fibrillae,  with  their  alternation  of  light  and  dark  spaces, 
are  fully  produced,  the  non-striated  fibre  retains  throughout  life  its  original 
embryonic  character. 

237.  Notwithstanding  the  energy  of  growth  in  Muscular  Fibre,  and  the 
constant  interstitial  change  which  seems  to  take  place  in  its  contents,  it  is 
doubtful  if  it  is  ever  regenerated,  when  there  has  been  actual  loss  of  substance. 
Wounds  of  muscles  are  united  by  Areolar  tissue,  which  gradually  becomes 
condensed;  but  its  fibres  never  acquire  any  degree  of  contractility. 

238.  The  Chemical  Composition  of  Muscular  Fibre  seems  to  be  very  uni- 
form, from  whatever  source  it  is  obtained.     It  is  impossible,  however,  to  de- 
termine it  with  precision  ;  on  account  of  the  difficulty  of  completely  isolating 
the  substance  of  the  fibres  from  the  areolar  tissue,  vessels,  and  nerves,  that 
are  blended  with  them.     The  proper  muscular  substance  differs   from  the 
simple  fibrous  tissues,  in  not  being  resolvable  into  gelatine  by  the  prolonged 
action  of  boiling  water;  and  in  being  soluble  in  acetic  acid,  from  which  it  is 


CHEMICAL  COMPOSITION  OF  MUSCLE.  203 

precipitated  by  ferrocyanide  of  potassium,  showing  that  it  belongs  to  the  pro- 
teine-compounds.  The  following  analyses  of  Muscle  by  Berzelius  corre- 
sponds very  exactly  with  those  since  made  by  Braconnot,  Schultz,  Marchand, 
and  other  Chemists : 

Fibrine  (from  the  proper  muscular  substance)     . 

Gelatine  (from  areolar  tissues)  

Albumen  and  hsematine 

Phosphate  of  lime,  with  albumen       ..... 

Alcoholic  extract,  with  salts  (lactates?)       .... 

Watery  extract,  with  salts   ....... 

Water,  and  loss 

100-00 

Thus  something  less  than  23  percent,  of  solid  matter  exists  in  ordinary  meat; 
and  in  100  parts  of  this  solid  mattter,  there  are  about  7k  parts  of  fixed  salts. 

\Kreatine  (from  xfsa?,  flesh),  originally  discovered  by  Chevreul,  in  1835,  has  been  proved 
by  the  recent  investigations  of  Liebig  to  be  a  constant  ingredient  of  the  muscles  of  all  the 
higher  classes  of  animals.  Schlossberger  found  it  in  the  flesh  of  the  alligator.  Its  crystals 
are  colorless,  perfectly  transparent,  and  of  great  lustre.  They  form  groups,  the  character 
of  which  is  exactly  similar  to  that  of  sugar  of  lead.  Its  formula  is  C8  N3  Hn  06.  It  dissolves 
easily  in  boiling  water,  and  a  solution  saturated  at  212°  forms  on  cooling  a  mass  of  small  bril- 
liant crystals,  and  is  nearly  insoluble  in  cold  alcohol.  It  is  neither  acid  nor  basic.  From  the 
action  of  strong  mineral  acids,  a  new  body  of  totally  different  chemical  qualities,  a  true  or- 
ganic alkali  is  formed,  which  Liebig  has  called  Kreatinine.  It  is  easily  obtained  from  the 
hydrochlorate  or  the  sulphate.  Kreatinine  is  more  soluble  both  in  cold  and  hot  water  than 
kreatine;  it  dissolves  in  boiling  alcohol,  and  crystallizes  on  cooling.  In  its  chemical  cha- 
racter it  is  analogous  to  ammonia. — Its  formula  is  C8  N3  H7  02. — Researches  on  the  Chemistry 
of  Food,  by  J.  Liebig.— London,  1847.— M.  C.] 

a.  The  exact  correspondence  in  ultimate  composition,  between  dried  Muscle,  and  dried 
Blood,  according  to  the  analyses  of  Playfair  and  Bockmann,  is  not  a  little  remarkable.     The 
following  are  their  results. 

PLAYFAIII.  BOCKMASTN. 

Muscle.  Blood.  Muscle.  Blood. 

Carbon         .         .         .     51-83  51-95  51-89  51-96 

Hydrogen    .         .         .       7-57  7-17  7-59  7-33 

Nitrogen      .         .         .     15-01  15-07  15-05  1508 

Oxygen        ...     21'36  21-39  21-24  21-21 

Ashes           .         .         .      4-23  4-42  4-23  4-42 

It  may  be  questioned,  from  these  results,  whether  the  amount  of  Haematine  in  Muscle  is  not 
greater  than  that  which  is  represented  by  the  previous  analysis ;  since  a  tissue  composed  of 
Fibrine  and  Albumen  alone,  could  not  possess  the  same  ultimate  composition  with  one,  in 
which  Haematine  is  present  in  large  proportion. 

b.  Some  very  interesting  researches  have  lately  been  made  by  Helmholtz,|  on  the  changes 
induced  in  the  tissue  by  Muscular  action.     Powerful  contractions  were  induced  by  electricity 
in  the  amputated  leg  of  a  Frog ;  and  were  kept  up  as  long  as  the  irritability  was  retained. 
The  flesh  of  the  two  limbs  was  then  analyzed;  and  it  was  found  that,  in  every  instance  the 
water-extractive  was  diminished  in  the  electrized  muscle,  to  the  extent  of  from  20  to  24  per 
cent.;  whilst  the  alcoholic  extract  was  increased  to  about  the  same  amount. — Similar  results 
were  obtained  from  experiments  on  warm-blooded  animals ;  the  amount  of  change,  how- 
ever, being  less,  on  account  of  the  shorter  duration  of  their  muscular  irritability. 

239.  Muscular  tissue,  properly  so  called,  is  as  extra-vascular  as  cartilage 
or  dentine ;  for  its  fibres  are  not  penetrated  by  vessels ;  and  the  nutriment 
required  for  the  growth  of  its  contained  matter  must  be  drawn  by  absorption 
through  the  myolemma.  But  the  substance  of  Muscle,  as  a  whole,  is  ex- 

*  [The  recent  researches  of  Liebig  make  it  exceedingly  probable  that  lactic  acid  is  a  con- 
stituent of  muscle.     Its  purpose  in  the  animal  organism  will  be  alluded  to  hereafter. — M.  C.] 
t  Mullet's  Archiv.,  1845. 


204 


OX  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 


Capillary  net- work  of  Muscle. 


tremely  vascular,  the  capillary  vessels  being  distributed  in  parallel  lines,  united 

by  transverse  branches,  in  the  minute  inter- 
spaces between  the  fibres  (Fig.  107);  so  that  it 
is  probable  that  there  is  no  fibre,  which  is  not  in 
close  relation  with  a  capillary.  The  number 
of  blood-vessels  in  a  given  space  will  of  course 
be  greater,  where  the  fibres  and  the  capilla- 
ries are  both  small,  as  in  Mammals  and  Birds, 
than  where  they  are  of  larger  diameter,  as  in 
Reptiles  and  Fishes ;  and  the  former  condition 
will  obviously  be  the  one  most  favourable  to 
the  performance  of  active  changes  between  the 
blood  and  the  muscle.  These  changes  consist, 
it  would  appear,  not  merely  in  the  nutrition  of 

the  tissue;  but  in  the  supply  of  oxygen,  which  is  a  necessary  condition  of 
the  excitement  of  its  activity.  We  shall  hereafter  see,  indeed,  that  every 
muscular  contraction  probably  involves  the  disintegration  of  a  certain  amount 
of  its  substance,  through  the  union  of  oxygen,  supplied  by  arterial  blood, 
with  its  elements  ;  and  that  the  great  demand  for  nutrition,  which  is  occa- 
sioned by  muscular  activity,  is  for  the  purpose  of  repairing  this  loss.  The 
muscles  of  warm-blooded  animals  speedily  lose  their  irritability,  after  the 
supply  of  arterial  blood  has  been  suspended,  either  through  the  cessation  of 
the  general  circulation,  or  by  deficient  aeration  of  the  fluid.  But  the  muscles 
of  cold-blooded  animals,  which  are  very  inferior  in  the  energy  and  rapidity 
of  their  action,  preserve  their  properties  for  a  much  longer  period,  after  the 
deprivation  of  their  supply  of  arterial  blood ;  in  accordance  with  the  general 
principle,  that,  the  lower  the  usual  amount  of  vital  energy,  the  longer  is  its 
persistence,  after  the  withdrawal  of  the  conditions  on  which  it  is  dependent. 
The  very  indisposition  to  a  change  of  composition,  on  which  the  less  ready 
action  depends,  produces  a  longer  retention  of  the  power  of  acting. 

240.  The  Muscles  of  Animal  life  are,  of  all  the  tissues  except  the  skin, 
those  most  copiously  supplied  with  Nerves.  These,  like  the  blood-vessels, 
lie  on  the  outside  of  the  Myolemma  of  the  several  fibres  ;  and  their  influence 
must  consequently  be  excited  through  it.  The  general  arrangement  of  these 
nerves  is  shown  in  Fig.  108.  Their  ultimate  fibres  or  tubes  cannot  be  said 

Fig.  108. 


Form  of  the  terminating  loops  of  the  nerves  in  the  muscles. 

to  terminate  anywhere  in  the  Muscular  substance;  for  after  issuing  from  the 
trunks,  they  form  a  series  of  loops,  which  return  either  to  the  same  trunk,  or 


NERVOUS  SYSTEM;  ITS  GENERAL  STRUCTURE. 


205 


to  an  adjacent  one.  The  occasional  appearance  of  a  termination  to  a  nervous 
fibril  is  caused  by  its  dipping  down  between  the  muscular  fibres,  to  pass  to- 
wards another  stratum.  The  nerves  are  almost  exclusively  of  the  motor 
kind;  but  a  few  sensory  are  blended  with  them.  We  see  this  most  clearly 
in  cases  in  which  the  motor  and  sensory  trunks  supplying  the  muscles  are 
distinct ;  as  in  the  muscles  of  the  orbit. — The  non-striated  muscles  are  very 
sparingly  supplied  with  nerves  ;  and  these  are  derived  (for  the  most  part,  if 
not  entirely),  from  the  Sympathetic  system,  rather  than  from  the  Cerebro- 
Spinal. 

241.  We  have,  lastly,  to  consider  the  structure,  composition,  actions,  and 
mode  of  growth  and  regeneration  of  the  Nervous  Tissue  ;  the  one  which  is 
most  distinctive  of  the  Animal  fabric,  and  which  serves  as  the  instrument  of 
the  operations  that  are  most  peculiar  to  it.  Wherever  a  distinct  Nervous  Sys- 
tem can  be  made  out  (which  has  not  yet  been  found  possible  in  the  lowest  of 
those  beings,  that,  from  their  general  structure  and  habits  of  life,  are  unques- 
tionably to  be  ranked  in  the  Animal  Kingdom),  it  consists  of  two  very  different 
forms  of  structure ;  the  presence  of  both  of  which,  therefore,  is  essential  to 
our  idea  of  it  as  a  whole.  We  observe,  in  the  first  place,  that  it  is  formed  of 
trunks,  which  are  distributed  to  different  parts  of  the  body,  and  especially  to 
the  muscles  and  to  the  sensory  surfaces  ;  and  of  ganglia,  or  masses  with 
which  the  central  terminations  of  those  trunks  come  into  connexion.  It  is 
easily  established  by  experiment,  that  the  trunks  themselves  have  no  power 
of  originating  changes  ;  and  that  they  only  serve  to  conduct  or  convey  the  in- 
fluence of  operations  which  take  place  at  their  central  or  peripheral  extremi- 
ties. For  if  a  trunk  be  divided  in  any  part  of  its  course,  all  the  parts  to  which 
the  portion  thus  cast  off  from  the  ganglion  is  distributed,  are  completely  para- 
lyzed ;  that  is,  no  impression  made  upon  them  is  felt  as  a  sensation  ;  and  no 
motion  can  be  excited  in  them  by  any  act  of  the  mind.  Or,  if  the  substance 
of  the  ganglion  be  destroyed,  all  the  parts  which  are  exclusively  supplied  by 
nervous  trunks  proceeding  from  it,  are  in  like  manner  paralyzed. — But  if, 

Fig.  109. 


Dorsal  ganglion  of  Sympathetic  nerve  of  Mouse  ;  a,  6,  cords  of  connection  with  adjacent  sympathetic 
ganglia ;  c,  c,  c,  c,  branches  to  the  viscera  and  spinal  nerves  ;  d,  ganglionic  globules  or  cells  ;  e,  nervous 
fibres  traversing  the  ganglion. 

when  a  trunk  is  divided,  the  portion  still  connected  with  the  ganglion  be  pinched 
or  otherwise  irritated,  sensations  are  felt  which  are  referred  to  the  points  sup- 
plied by  the  separated  portion  of  the  trunk  ;  which  shows  that  the  part  re- 
maining in  connexion  with  the  ganglion  is  still  capable  of  conveying  impres- 
18 


206 


ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 


sions,  and  that  the  ganglion  itself  receives  these  impressions,  and  makes  them 
felt  as  sensations.  On  the  other  hand,  if  the  separated  portion  of  the  trunk 
be  irritated,  motions  are  excited  in  the  muscles  which  it  supplies ;  showing 
that  it  is  still  capable  of  conveying  the  motor  influence,  though  cut  off  from 
the  usual  source  of  that  influence. 

242.  In  the  ordinary  Nerve-trunks,  we  find  only  one  form  of  Nervous  tis- 
sue ; — that  which  may  be  designated  as  the  fibrous  or  tubular.     In  the  Gan- 
glia, we   find,  in   addition  to  this,  a   substance  made  up  of  peculiar  cells  or 
vesicles  ;  which  may  be  distinguished   as  the  vesicular  nervous  matter.     In 
fact,  the  character  of  a  Ganglionic  centre  (which  is  frequently  not  otherwise 
clearly  distinguished  as   such)  is   derived  from  the  presence  of  this  vesicular 
substance. 

243.  The  ultimate  Nerve-fibre,  in  its  most  complete  form, — such  as  is  pre- 
sented to  us  in  the  ordinary  spinal  nerves, — is  distinctly  tubular ;  being  com- 
posed of  an  external  cylindrical  membranous  sheath,  within  which  the  peculiar 
nervous  matter  is  contained.     This  membranous  tube,  like  the  Myolemma  of 
muscular  fibre,  is  extremely  delicate  and  transparent ;  and  is  nearly  or  quite 


$ c  I 


A.  Diagram  of  tubular  fibre  of  a  spinal  nerve  ;— a.  Axis  cylinder,  b.  Inner  border  of  white  substance, 
e,  e.  Outer  border  of  white  substance,  d,  d.  Tubular  membrane.  B.  Tubular  fibres ;  e,  in  a  natural 
state,  showing  the  parts  as  in  A.  /.  The  white  substance  and  axis  cylinder  interrupted  by  pressure, 
while  the  tubular  membrane  remains,  g.  The  same,  with  varicosities.  h.  Various  appearances  of  the 
white  substance  and  axis  cylinder  forced  out  of  the  tubular  membrane  by  pressure,  i.  Broken  end  of  a 
tubular  fibre,  with  the  white  substance  closed  over  it.  k.  Lateral  bulging  of  white  substance  and  axis 
cylinder,  from  pressure.  I.  The  same  more  complete,  g'.  Varicose  fibres  of  various  sizes,  from  the 
cerebellum,  c.  Gelatinous  fibres  from  the  solar  plexus,  treated  with  acetic  acid,  to  exhibit  their  cell- 
nuclei.  B  and  c  magnified  320  diameters.] 

homogeneous.     It  is  not  penetrated  by  blood-vessels ;  nor  is  it  ever  seen  to 
branch  or  anastomose  with  others ;  so  that  there  is  reason  to  regard  it  as  form- 


TUBULAR  NERVOUS  TISSUE. 


207 


ing  one  continuous  sheath,  that  isolates  the  contained  matter  from  the  surround- 
ing tissue,  along  the  whole  course  of  the  nerve-trunk,  from  its  central  to  its 
peripheral  extremity.  When  the  nerve-fibres  are  examined  in  a  very  fresh 
state,  their  contents  appear  pellucid  and  homogeneous,  and  of  a  fluid  consist- 
ence ;  so  that  each  tube  or  fibre  looks  like  a  cylinder  of  clear  glass,  with  sim- 
ple, well-defined,  dark  edges.  But  a  kind  of  coagulation  soon  takes  place  in 
the  contained  substance,  making  it  easily  distinguishable  from  the  tube  itself; 
for  the  latter  is  then  marked  by  a  double  line,  as  shown  in  Fig.  Ill,  A.  The 
substance  which  is  in  immediate  contact  with  the  inner  wall  of  the  nerve-tube, 
is  more  opaque  than  that  which  occupies  its  centre,  and  of  a  different  refract- 
ing power;  and  thus  it  forms  a  hollow  cylinder,  which  surrounds  the  latter, 
and  which  is  known  under  the  name  of  the  White  substance  of  Schwann.  The 
centre  or  axis  of  the  tube  is  occupied  by  a  substance  that  preserves  its  trans- 
parency;  and  this  is  the  axis-cylinder  of  Rosenthal  and  Purkinje.  It  may  be 
surmised  that  the  White  substance  of  Schwann,  which  exhibits  much  variety 
in  thickness  in  different  parts  of  the  nervous  system,  chiefly  serves,  like  the 
membranous  investment,  to  isolate  the  interior  matter  ;  which  last  seems  to  be 
the  essential  constituent  of  the  nervous  fibre.  The  whole  of  the  matter  con- 
tained in  the  tubular  sheath  is  extremely  soft;  yielding  to  very  slight  pressure, 
and  readily  escaping  from  the  cut  extremities  of  the  tubes.  The  tubular  sheath 
itself  varies  in  density  in  different  parts  ;  being  stronger  in  the  nervous  trunks 
than  in  the  substance  of  the  brain  and  spinal  cord.  In  the  former,  it  is  not 
difficult  to  show  that  the  regular  form  of  the  nerve-tube  is  a  perfect  cylinder ; 
though  a  little  disturbance  will  cause  an  alteration  in  this, — a  small  excess  of 
pressure  in  one  part  forcing  the  contents  of  the  tube  towards  another  portion, 

Fig.  111. 


Structure  of   nerve-tubes,  magnified  350  diameters.    A.  Cylindrical  tubuli  from  nerve.    B,  Varicose 
tubuli  from  brain,    c,  Nerve-tubes,  of  which  one  exhibits  the  remains  of  nuclei  in  its  walls. 

where  they  are  more  free  to  distend  it,  and  thus  producing  a  swelling.  The 
greater  delicacy  of  the  tubular  sheath  in  the  latter,  causes  this  result  to  take 
place  with  yet  more  readiness  ;  so  that  a  very  little  manipulation  exercised 
upon  the  fibres  of  the  Brain  or  Spinal  Cord,  or  on  those  of  special  sense,  occa- 
sions them  to  assume  a  varicose  or  beaded  appearance  (Fig.  Ill,  B),  which, 
when  first  observed  by  Ehrenberg,  was  thought  to  be  characteristic  of  them. 
When  the  fibres  of  these  parts  are  examined,  however,  without  any  such  pre- 
paration, they  are  found  to  be  as  cylindrical  as  the  others. — The  diameter  of  the 
tubular  fibres  of  the  cerebro-spinal  nerve-trunks  in  Man,  usually  varies  from 
about  l-2000th  to  l-4000th  of  an  inch,  being  sometimes  as  great,  however, 
as  1-1 500th  of  an  inch ;  and  sometimes  much  below  the  least  of  the  above 


208 


ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 


dimensions.  The  fibres  decrease  in  size  as  they  approach  the  brain,  either 
directly,  or  through  the  medium  of  the  spinal  cord ;  and  in  the  brain  itself  they 
continue  to  diminish,  as  they  pass  through  the  medullary  towards  the  cortical 
portion  ;  so  that  they  are  very  commonly  found  of  no  more  than  1 -7000th  or 
l-8000th  of  an  inch  in  diameter,  and  sometimes  as  little  as  l-14,000th.  Like 
most  other  elementary  structures,  they  are  of  considerably  larger  dimensions 
in  Reptiles  and  Fishes  ;  varying,  according  to  Dr.  Todd,  from  l-1260th  to 
l-2280th  of  an  inch  in  the  Frog;  being  in  the  Eel  as  much  as  the  l-1040th 
of  an  inch  ;  and  in  the  optic  nerve  of  the  Cod,  no  less  than  l-650th  of  an  inch 
in  diameter.* 

244.  Besides  these  proper  tubular  nerve-fibres, — of  which,  in  combination 
with  areolar  and  fibrous  tissue,  blood-vessels,  &c.,  a  large  proportion  of  the 
cerebro-spinal  nerve-trunks  are  made  up, — there  are  certain  other  fibres,  which 
are  peculiarly  abundant  in  the  trunks  of  the  Sympathetic  system,  and  which 
are  of  different  character  from  the  preceding.  They  are  chiefly  distinguished 
by  their  small  size,  their  diameter  not  being  above  half  or  one-third  of  that  of 
the  ordinary  nervous  tubuli.  They  are  destitute  of  the  double  contour,  which 
has  been  shown  to  result  in  the  preceding  case  from  the  presence  of  two  dis- 
tinct substances  within  the  tubular  investment;  and  their  contents  appear  to 
be  homogeneous.  And  when  they  are  aggregated  in  bundles,  they  possess  a 
yellowish-grey  colour. — Although  these  fine  fibres  exist  in  greater  proportion 
in  the  Sympathetic  system  than  in  the  Cerebro-spinal,  yet  they  are  present 
in  great  numbers  in  some  of  the  nerves  of  the  latter;  and  it  is  even  question- 


Primitive  fibres  and  ganglionic  vesicles  of  human  brain,  after  Purkinje.  A,  ganglionic  vesicles  lying 
amongst  nerve-tubes  and  blood-vessels,  in  substance  of  optic  thalamus ;  a,  vesicle  more  enlarged  ;  6, 
vascular  trunk.  B,  B,  vesicles  with  variously-formed  processes,  from  dark  portion  of  crus  cerebri.  Mag- 
nified 350  diameters. 

able,  whether  they  may  not  be  continuous  with  the  ordinary  tubular  fibres. 
They  may  be  traced  into  the  ganglia  of  the  Sympathetic,  into  the  ganglia  on 
the  posterior  roots  of  the  Spinal  nerves,  and  even  to  the  ganglionic  matter  of 
the  Brain  and  Spinal  Cord.t 

*  Cyclopaedia  of  Anatomy  and  Physiology,  Vol.  in.,  p.  593. 

f  Much  controversy  has  recently  taken  place  in  Germany,  regarding  the  existence  of  a 
set  of  fibres  peculiar  to  the  Sympathetic  system.  The  grey  or  gelatinous  fibres,  described  by 
Remak,  and  (following  him)  by  Miiller  and  others,  as  essentially  constituting  the  Organic 
system  of  Nerves,  are  now  generally  admitted  not  to  be  entitled  to  the  designation  of  nerve- 


VESICULAR  NERVOUS  TISSUE. 


209 


113. 


245.  The  second  primary  element  of  the  Nervous  system,  without  which 
the  fibrous  portion  would  seem  to  be  totally  inoperative,  is  composed  of  nu- 
cleated cells,  consisting  of  a  finely  granular  substance,  and  lying  somewhat 
loosely  in  the  midst  of  a  minute  plexus  of  blood-vessels.    Their  original  form 
may  be  regarded  as  globular ;  whence  they  have  been  called  ganglion-globules. 
This,  however,  is  liable  to  alteration;  sometimes,  perhaps, from  external  com- 
pression ;  but  more  commonly  through  their  own  irregular  mode  of  growth. 
They  frequently  extend    themselves  into  long   processes,  which  may  give 
them  (according  to  the  number  thus  projecting)  a  caudate  or  a  stellate  aspect, 
resembling  that  of  the  pigment-cells  of  the  Batrachia.     These  processes  are 
composed  of  a  finely-granular  substance,  resembling  that  of  the  interior  of  the 
vesicle,  with  which  they  seem  to  be  distinctly  continuous.     They  are  very 
liable  to  break  off  near  the  vesicle ;  but  if  traced  to  a  distance,  they  are  found 
to  divide   and  subdivide,  and  at  last  to 

give  off  some  extremely  fine  transpa- 
rent fibres  ;  some  of  which  seem  to  in- 
terlace with  those  of  other  stellate  cells, 
whilst  others  become  continuous  with 
the  axis-cylinders  of  the  nerve-tubes. 
Such  vesicles  have  been  seen  alike  in 
the  ganglionic  masses  of  the  Cerebro- 
spinal,  and  in  those  of  the  Sympathetic 
system.*  Besides  the  finely-granular 
substance  just  mentioned,  these  cells 
usually  contain  a  collection  of  pigment- 
granules,  which  especially  cluster  round 
the  nuclei,  and  give  them  a  reddish  or 
yellowish-brown  colour.  This  pigment 
seems  to  have  some  resemblance  to 
the  hasmatine  of  the  blood  ;  and  it  is 
usually,  if  not  invariably,  deficient 
among  the  In  vertebra  ta,  as  well  as  less 
abundant  in  Reptiles  and  Fishes.  The 
vesicles  are  sometimes  covered  with  a 
layer  of  a  soft  granular  substance,  which  adheres  closely  to  their  exterior  and 
to  their  processes  ;  this  is  the  case  in  the  outer  part  of  the  cortical  substance 
of  the  human  brain.  In  other  instances,  each  cell  is  inclosed  in  a  distinct  en-' 
velope  composed  of  smaller  cells,  closely  adherent  to  each  other,  and  to  the 
contained  cell ;  such  an  arrangement  is  common  in  the  smaller  ganglia,  and 
in  the  inner  portion  of  the  cortical  substance  of  the  brain. — The  diameter  of 
the  vesicles  is  extremely  variable,  owing  to  the  changes  of  form  above  de- 
scribed ;  that  of  the  globular  ones  is  usually  between  l-300th  and  l-1250th  of 
an  inch. 

246.  In  the  central  or  ganglionic  masses  of  the  Nervous  system,  we  find 
these  vesicles  aggregated  together,  and  imbedded  in  a  finely-granular  matter; 
the  whole  being   traversed  by  a   minute   plexus   of  capillary  blood-vessels. 
The  entire  substance,  made  up  of  these  distinct  elements,  is  commonly  known 
as  the  cineritious  or  cortical  substance ;  being  distinguished  by  its  colour,  in 

fibres,  but  to  be  a  form  of  simple  fibrous  tissue.  The  peculiar  fibres  described  above,  were 
first  pointed  out  by  Bidder  and  Volkmann ;  whose  statements  in  regard  to  them  have  re- 
cently been  confirmed  by  the  laborious  and  impartial  researches  of  Kdlliker.  (See  his  work 
"Die  Selbstiindigkeit  und  Abhangigkeit  des  Sympathischen  Nervensystems,"  1844;  and  the 
abstract  of  his  results  in  Mr.  Paget's  able  Report,  in  Brit,  and  For.  Med.  Review,  July,  1846, 
p.  271.) 

*  See  Todd  and  Bowman's  Physiological  Anatomy,  Vol.  I.,  p.  214.     See  also  Kolliker,  loc. 
cit.;  and  Dr.  Radclyffe  Hall,  in  Edinburgh  Med.  &  Surg.  Journal,  April,  1846. 

18* 


Nerve-vesicles  from  the  Gasserian  ganglion  of 
the  human  subject :— a.  A  globular  one  with  de- 
fined border;  6,  its  nucleus;  c,  its  nucleolus.  d. 
Caudate  vesicle,  e.  Elongated  vesicle,  with  two 
groups  of  pigment  particles.  /.  Vesicle  surround- 
ed by  its  sheath,  or  capsule,  of  nucleated  particles. 
g.  The  same,  the  sheath  only  being  in  focns. — 
Magnified  300  diameters.] 


210 


ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 

[Fig.  114. 


Ganglion  globules,  with  their  processes,  nuclei,  and  nucleoli:— a.  a.  From  the  deeper  part  of  the  gray 
matter  of  the  convolutions  of  the  cerebellum.  The  larger  processes  are  directed  towards  the  surface 
of  the  organ,  b.  Another  from  the  cerebellum,  c.  d.  Others  from  the  post,  horn  of  gray  matter  of  the  dor- 
sal region  of  the  cord.  These  contain  pigment,  which  surrounds  the  nucleus  in  c.  In  all  these  specimens 
the  processes  are  more  or  less  broken.— Magnified  200  diameters.] 

Man  and  the  higher  animals  at  least,  from  the  white  substance  composed  of 
nerve-tubes,  of  which  the  trunks  of  the  nerves,  as  well  as  a  large  part  of  the 
brain  and  spinal  cord,  are  made  up ;  and  occupying  in  the  brain  a  position 
external  to  the  latter,  which  is  often  termed  the  medullary  substance.  This 
position,  however,  is  quite  an  exceptional  one;  for  in  the  spinal  cord  and  in 
the  scattered  ganglia  of  Vertebrated  animals,  and  in  all  the  ganglionic  centres 
of  ^Invertebrata, — everywhere,  in  fact,  except  in  the  Brain, — the  vesicular 
nerve  substance  occupies  the  centres  of  the  ganglia;  consequently  the  terms 

cortical  and  medullary,  as  applied  to  the  vesi- 
[Fag.  115.  cular  and  tubular  substances  respectively,  are 

quite  inappropriate.  Nor  are  the  designations 
that  have  reference  to  their  colour,  much  more 
uniformly  correct:  for,  as  we  have  seen, 
the  vesicular  substance  may  be  destitute  of 
internal  pigment-granules,  and  the  blood  in 
its  capillary  plexus  may  be  pale  or  colourless, 
so  that  the  reddish-grey  hue,  which  is  ex- 
pressed by  the  term  cineritious,  may  be  entirely 
wanting ;  whilst,  on  the  other  hand,  we  have 
seen  that  certain  of  the  nerve-fibres,  making 
up  what  is  commonly  termed  the  white  sub- 
stance, are  of  a  grey  colour.  Hence  the  only 
valid  distinction  between  these  two  kinds  of 
nervous  matter,  is  that  which  has  reference  to 
their  constitution; — as  consisting  of  cells  or 
vesicles  on  the  one  hand ;  or  of  tubes  or  fibres, 
on  the  other. 
247.  The  connection  between  the  fibrous  and 


A  small  piece  of  the  otic  ganglion  of 
the  sheep,  slightly  compressed ;  show- 
ing the  interlacement  of  the  internal 
fibres,  and  the  vesicular  matter. — 
(After  Valentin.)] 


CONNECTION  OF  FIBROUS  AND  VESICULAR  SUBSTANCES. 


211 


vesicular  nervous  elements,  in  the  nervous  centres,  has  not  yet  been   tho- 
roughly elucidated.     It  seems   certain,  on  the  one  hand,  that  some  of  the 


[Fig.  116. 


[Fig.  117. 


A.  Blending  of  the  vesicular  and  fibrous  nervous 
matter  in  the  dentate  body  of  the  cerebellum:— a, 
Ganglion  globule,  with  its  nucleus  and  nucleolus. 
b.  Nerve-tube,  slightly  varicose,  in  close  contact 
with  the  ganglion  globule,  b'.  Smaller  nerve-tubes. 
These  parts  all  lie  in  a  finely  granular  matrix  in- 
terspersed with  nuclei, c.  B.  Vesicular  and  fibrous 
matter  of  the  laminae  of  the  cerebellum,  a.  Gan- 
glion globule,  b.  Very  minute  nerve-tubes  tra- 
versing a  finely  granular  matrix,  in  which  are 
numerous  rounded  nuclei,  c.] 


From  the  Gasserian  ganglion  of  an  adult:— a.  a. 
Ganglion  globules  with  their  nucleus,  nucleated 
capsule,  and  pigment,  t.  Tubular  fibres,  running 
among  the  globules  in  contact  with  their  capsule. 
g.  Gelatinous  fibres  also  in  contact  with  the  gan- 
glion globules. — Magnified  3*20  diameters.] 


fibres  come  into  direct  continuity  with  caudate  prolongations  of  the  ganglionic 
corpuscles,  and  may  thus  be  said  to  originate  from  them.     This  appears  to 

Fig.  118. 


Primitive  fibres  and  ganglionic  vesicles.  A,  from  sympathetic  ganglion  ;  *  a  separate  vesicle,  show- 
ing its  pellucid  nucleus  and  nucleolus.  B,  from  grey  substance  of  human  cerebellum  ;  a,  6,  plexus  of 
primitive  fibres ;  c,  nucleated  globules  ;  *  a  separate  globule  from  human  Gasserian  ganglion.  Magni- 
fied 350  diameters. 

be  especially  the  case,  with  regard  to  the  class  of/ne  fibres  (§  244).     On  the 


212  ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 

other  hand,  it  seems  equally  certain  that  there  are  many  nerve-tubes  which 
simply  enter  the  ganglionic  masses,  pass  round  and  amongst  the  cells,  and 
then  emerge  from  them,  without  having  undergone  any  distinct  change,  save 
that  they  present  a  soft  and  varicose  appearance,  whilst  threading  their  way 
through  the  cells.  And  it  is  equally  certain  that  there  are  many  ganglionic 
corpuscles,  which  never  acquire  the  caudate  prolongations,  and  which  appear 
specially  destined  to  act  upon  this  class  of  nerve  fibres. — Some  observations 
which  have  been  made  upon  the  nervous  system  of  foetuses,  in  which  the 
brain  and  spinal  cord  were  wanting,  present  a  remarkable  confirmation  of  this 
view.*  The  nervous  cords  were  for  the  most  part  developed ;  and  at  their 
(so  called)  origins  or  central  extremities,  they  were  found  to  hang  as  loose 
threads  in  the  cavities  of  the  cranium  and  spine.  On  examining  these  threads, 
it  was  found  that  the  nerve-tubes,  of  which  they  consisted,  formed  distinct 
loops ;  each  of  which  was  composed  of  a  fibre  that  entered  the  cavity,  and 
then  returned  from  it.  These  loops  were  imbedded  in  granular  matter, 
resembling  that  interposed  between  the  vesicles  in  the  cortical  substance  of 
the  brain ;  and  perhaps  to  be  regarded  as  vesicular  matter  in  an  early  stage 
of  its  formation.  All  that  is  known  of  the  laws  regulating  the  formation  of 
such  irregular  productions,  leads  to  the  belief,  that  we  may  rightly  consider 
this  arrangement  of  the  nerve-tubes  as  one  which  exists  in  the  nervous  cen- 
tres, when  they  are  normally  developed.  But  it  may  not  be  the  only  one; 
for,  as  already  pointed  out,  some  of  the  nerve-fibres  appear  to  originate  from 
the  filamentous  prolongations  of  certain  ganglionic  cells.  Additional  informa- 
tion is  much  needed  upon  this  point. 

248.  The  arrangement  of  the  nerve-fibres,  at  their  peripheral  extremities, 
seems  to  be  essentially  of  the  same  character.  It  has  been  already  shown 
that  the  motor  fibres,  which  are  distributed  to  the  muscles,  have  no  proper 
terminations ;  a  series  of  loops,  returning  into  themselves  or  joining  others, 
being  formed  by  the  ultimate  ramifications  of  the  main  trunks.  The  arrange- 
ment of  the  sensory  fibres  seems  to  be  usually  of  the  same  nature.  The 
principal  trunks  subdivide  into  numerous  anastomosing  branches,  forming  a 
sort  of  plexus  in  the  substance  of  the  skin ;  and  from  this,  single  filaments 
detach  themselves  at  intervals,  rising  up  into  the  papillary  elevations  of  its 
surface,  and  then  returning  again  into  the  plexus,  after  making  a  series  of 

Fig.  119. 


Distribution  of  the  tactile  nerves  at  the  extremity  of  the  human  thumb,  as  seen 
in  a  thin  perpendicular  section  of  the  skin. 

loops,  in  which  a  sort  of  varicose   enlargement  of  the  fibre  may  often  be 
noticed.     Similar  looped  terminations  have  been  traced  in  the  nerves  supply- 

*  Dr.  Lonsdale,  in  Edinb.  Med.  and  Surg.  Journal,  No.  CLTII.  ;  and  Mr.  Paget  in  Brit,  and 
For.  Med.  Rev.,  No.  XLIII.  p.  273. 


CONNECTION  OF  FIBROUS  AND  VESICULAR  SUBSTANCES. 


213 


Terminal  nerves  on  the  sac  of  the  second 
molar  tooth  of  the  lower  jaw  in  the  sheep, 
showing  the  arrangement  in  loops. — (After 
Valentin.)] 


ing  the  dental  sacculi,  in  the  expansions  of  [Fig.  120. 

the  auditory  nerve  distributed  upon  the  de- 
licate membrane  lining  the  cavities  of  the 
internal  ear,  and  elsewhere.  It  would  yet, 
however,  be  premature  to  say,  that  this  ar- 
rangement is  universal. — The  peripheral 
extremities  may  be  really  considered  as 
the  origins  of  the  sensory  nerves  ;  since 
it  is  in  them  that  those  changes  are  ef- 
fected which  it  is  the  office  of  the  trunks 
to  conduct  towards  the  centres  ;  and  it  may 
be  reasonably  inquired,  whether  anything 
like  the  vesicular  substance  of  the  ganglia 
can  be  detected  in  them.  In  examining 
the  retina  microscopically,  it  is  found  to 
be  almost  entirely  made  up  of  a  layer  of 
ganglionic  cells,  very  closely  resembling 
those  of  the  grey  matter  of  the  brain ;  and 
these  are  in  apposition  with  the  vascular 
layer;  so  that  we  have  here  precisely  the 
same  provision  for  exciting  a  change,  that 
is  to  be  conducted  towards  the  centres,  as 
we  have  in  the  brain  for  exciting  a  change, 
whose  influence  is  to  be  conveyed  towards 
the  periphery.  Something  of  the  same 
kind  has  been  seen  in  connection  with  the 
corresponding  expansions  of  the  olfactive 
and  auditory  nerves  ;  and  it  is  probable 
that  similar  elements  exist  in  the  papillae 

of  the  skin  and  tongue,  to  which  the  nerves  of  taste  and  touch  are  distributed. 
In  these  papillae  we  find  loops  of  capillary  vessels  in  close  contiguity  with 
the  extremities  of  the  nerve-tubes. — Hence  we  may  state  it  as  a  general  fact, 
that  wherever  a  change  is  to  be  originated,  we  find  some  form  of  Vesicular 
matter,  with  capillary  blood-vessels ;  whilst  for  the  conduction  of  such  a 
change  to  distant  parts,  the  Fibrous  structure  is  alone  required. 

249.  The  Chemical  constitution  of  the  Nervous  matter  is  peculiar ;  and 
an  acquaintance  with  its  general  features  is  of  importance,  in  leading  us  to 
recognize  in  the  excretions  the  results  of  its  decomposition. 

a.  The  following,  according  to  L'Heritier,  is  the  relative  proportion  of  the  different  con- 
stituents in  individuals  of  different  classes  : — 

Aged 

Infants.     Youths.     Adults.      Persons.     Idiots. 

Water         ....       82-79         74-26         72-51         73-85         70-93 
Albumen          .         .         .  7-00         10-20  9-40  8-65  8-40 

Fat 3-45  5-30  6-10  4-32  5-00 

Osmazome  (?)  and  Salts  5-96  8-59         10-19         12-18         14-82 

Phosphorus      .         .         .  0-80  1-65  1-80  1-00  0-85 

It  appears  from  the  researches  of  M.  Fremy,  that  the  Phosphorus  is  combined  with  part  of 
the  fatty  matter;  and  forms  with  it  two  peculiar  fatty  acids,  termed  by  him  the  Cerebric  and 
Oleophosphoric. — Cerebric  acid,  when  purified,  is  white,  and  presents  itself  in  crystalline 
grains.  It  contains  a  small  proportion  of  Phosphorus ;  and  differs  from  the  ordinary  fatty 
matter,  in  being  partly  composed  of  Nitrogen.  It  consists  of  66-7  per  cent,  of  Carbon,  10'6 
of  Hydrogen,  2-3  of  Nitrogen,  19-5  of  Oxygen,  and  0-9  of  Phosphorus;  and  thus  differs  from 
ordinary  fat,  not  only  in  containing  Phosphorus  and  Nitrogen,  but  in  possessing  more  than 
twice  their  proportion  of  Oxygen.* — Oleophosphoric  acid  is  separated  from  the  former  by  its 

*  It  is  probable  that,  in  the  above  analysis  of  L'Heritier,  the  Cerebric  acid,  which  is  not 
soluble  in  ether,  is  included  under  the  head  of  Osmazome ;  for  the  analyses  of  Denis  and 


214  ON  THE  ELEMENTARY  PARTS  OF  THE  HUMAN  FABRIC. 

solubility  in  ether :  it  is  of  a  viscid  consistence ;  but  when  boiled  for  a  long  time  in  water  or 
alcohol,  it  gradually  loses  its  viscidity,  and  resolves  .itself  into  a  fluid  oil,  which  is  pure 
Oleine,  whilst  phosphoric  acid  remains  in  the  liquor.  The  proportion  of  Phosphorus  which 
this  oil  contains  is  about  2  per  cent. — Cholesterine  has  also  been  extracted  from  the  brain  by 
M.  Fremy  in  considerable  quantity. — The  proportion  of  Fixed  Salts  is  small;  not  being 
above  3£  parts  in  100  of  Dry  Cerebral  matter ;  which  is  less  than  half  the  proportion  that 
exists  in  Muscle. — According  to  Lassaigne,  the  chemical  composition  of  the  Cortical  and 
Medullary  substances  of  the  brain  is  essentially  different;  the  former  containing  85  per 
cent,  of  water,  whilst  the  latter  has  only  73;  the  cortical  substance  having  also  3-7  per  cent, 
of  a  red  fatty  matter,  of  which  the  medullary  has  scarcely  any;  and  being  almost  entirely 
destitute  of  the  white  fatty  matter,  which  exists  in  large  proportion  in  the  latter. 

The  Albuminous  matter  in  the  above  analyses,  is  probably  that  of  which 
the  walls  of  the  nerve-cells  and  nerve-tubes,  and  of  the  capillary  blood-vessels 
are  composed.  The  contents  of  these  cells  and  tubes  are  represented  chiefly, 
if  not  entirely,  by  the  phosphorized  fats ;  and  there  are  many  reasons  for  re- 
garding these  as  the  active  agents  in  the  operations  of  the  Nervous  system. 
It  will  be  remarked,  that  the  amount  of  phosphorus  is  the  greatest  at  the 
period  of  greatest  mental  vigour  ;  and  that  in  infancy,  old  age,  and  idiocy,  the 
proportion  is  not  above  half  that  which  is  present  during  the  adolescent  and 
adult  periods. 

250.  The  Nervous  System  is  very  copiously  supplied  with  blood-vessels  ; 
the  arrangement  of  which  varies  according  to  the  form  of  the  elementary  parts, 
in  which  they  are  distributed.  Thus  in  the  Vesicular  substance  of  the  ner- 
vous centres,  the  capillaries  form  a  minute  net-work,  in  the  interstices  of  which 
the  ganglionic  cells  are  included.  In  the  tubulo-fibrous  substance,  the  capilla- 
ries are  distributed  much  on  the  same  plan  as  in  Muscular  tissue ;  the  net- 
work being  composed  of  straight  vessels,  which  run  along  the  course  of 
the  fibres,  passing  between  the  nerve-tubes,  and  which  are  connected  at 
intervals  by  transverse  branches.  And  at  the  sensory  extremities  of  the 

Fig.  121. 


Capillary  net- work  of  Nervous  Centres.  Distribution  of  Capillaries  at  the  sur- 

face of  the  skin  of  the  finger. 

nerves  we  find  loops  of  Capillaries  arching  over  their  terminal  and  probably 
looped  filaments. — The  Brain  of  Man,  taken  en  masse,  has  been  estimated  to 
receive  one-sixth  of  the  whole  amount  of  blood,  although  its  weight  is  not 
usually  more  than  a-fortieth  part  of  that  of  the  entire  body.  Whether  or  not 
this  estimate  be  precisely  correct,  there  can  be  no  doubt  that  it  receives  far 
more  blood,  than  any  other  part  containing  the  same  amount  of  solid  matter. 
Now  this  copious  supply  of  blood  evidently  has  reference  to  two  distinct  ob- 
jects ;  first,  to  supply  the  necessary  conditions  for  the  action  of  the  Nervous 
system  ;  and,  secondly,  to  maintain  its  nutrition.  Many  circumstances  lead 
to  the  conclusion  that,  in  the  Nervous  as  in  the  Muscular  system,  every  vital 
operation  is  necessarily  connected  with  a  certain  change  of  composition,  so 

other  chemists  give  a  much  higher  proportion  to  the  phosphorized  fat,  and  a  much  smaller 
one  to  the  ill-defined  compounds  represented  by  the  designation  Osmazome. 


SUPPLY  OF  BLOOD  TO  NERVOUS  TISSUE. 


215 


that  no  manifestation  of  nervous  power  can  take  place,  unless  this  change  can 
be  effected.  There  is  strong  reason  to  believe,  further,  that  this  change  es- 
sentially consists  in  the  union  of  oxygen  conveyed  by  the  arterial  blood,  with 
the  elements  of  the  proper  nervous  matter ;  and  that  this  union  consequently 
involves  the  death  and  disintegration  of  a  certain  amount  of  the  nervous  tis- 
sue,— the  reproduction  of  which  will  be  requisite,  in  order  that  the  systsm 
may  be  maintained  in  a  state  fit  for  action.  This  reproduction  is  effected  by 
the  nutritive  process,  which  takes  place  at  the  expense  of  other  constituents 
of  the  blood;  and  it  will  proceed  most  vigorously  in  the  intervals,  when  the 
active  powers  of  the  nervous  system  are  not  being  called  into  operation  (§§  292 
—296). 

251.  The  proofs  of  this  continual  waste  and  reproduction  of  the  Nervous 
substance,  will  be  partly  found  in  the  appearance  of  the  products  of  its  de- 
composition in  the  excretions,  and  in  the  demand  which  is  set  up  for  the  ma- 
terials for  its  reparation;  these  being  found  to  accord  in  amount,  as  will  be 
shown  hereafter,  with  the  degree  of  its  functional  activity.     But  evidence  of 
another  kind  may  be  drawn  from  the  microscopic  appearances  observable  in 
the  cortical  substance  of  the  Brain.     It  seems  probable,  from  the  observations 
of  Henle,  that  there  is  as  continual  a  succession  of  nerve-cells,  as  there  is  of 
epidermic  cells;  their  development  commencing  at  the  surface,  where  they 
are  most  copiously  supplied  with  blood-vessels  from  the  pia  mater;  and  pra- 
ceeding  as  they  are   carried  towards  the  inner  layers,  where  they  come  into 
more  immediate  relation  with  the  tubular  portion  of  the  nervous  tissue.     This 
change  of  place  is  probably  due  to  the  continual  death  and  disintegration  of 
the  mature  cells,  where  they  are  connected  with  the  fibres,  and  the  equally 
rapid   production  of  new  generations  at  the  external  surface ; — the  newly- 
formed  epidermic  cells  being  thus  carried  inwards,  in  precisely  the  same  man- 
ner that  the  epidermic  cells  are  carried  outwards. 

252.  The  first  development  of  the  Nerve-tubes  appears  to  take  place,  like 
that  of  Muscular  fibre,  by  the  coalescence  of  a  number  of  primary  cells  into 
a  continuous  tube ;  for  although  the  primary  nervous   cell  has  not  yet  been 
made  out  with  precision,  the  nuclei  of  what  seem  to  be  the  original  cells  may 
frequently   be    seen   in   the   fully- 
formed   tube,  lying  between  the'ir  [Fig.  123. 
membranous  walls,  and  the  white 

substance  of  Schwann  (111,  c). 
When  first  a  nerve-fibre  can  be  re- 
cognized as  such,  it  has  a  strong  re- 
semblance to  the  gelatinous  fibres 
of  the  sympathetic  trunks ;  being  a 
cord  of  small  diameter,  without  any 
clear  distinction  between  the  tube 
and  its  contents,  of  granular  consist- 
ence, and  having  nuclei  at  no  great 
distance  from  each  other.  The 
substance  of  the  fibre,  at  this  pe- 
riod, seems  to  correspond  with  the 
axis-cylinder  of  the  fully-formed 
nerve-tube ;  the  white  substance  of 
Schwann  is  subsequently  deposited 
around  it,  separating  it  from  the 
membranous  tubular  envelope. — 
The  first  development  of  the  vesi- 
cular substance  appears  to  take  place  on  the  same  plan  with  its  subsequent 
renewal. 


Various  stages  of  the  development  of  nerve  ; — a. 
Earliest  stage,  b.  Detached  fibre,  c.  Nucleated  fibre 
in  the  lower  part  of  which,  d,  the  white  substance  of 
Schwann  has  begun  to  be  deposited,  e.  Nucleus  in  a 
more  fully-formed  fibre  between  the  white  substance 
and  tubular  membrane.  /.Displays  the  tubular  mem- 
brane, the  contained  matter  having  given  way.— (After 
Schwann.)] 


216  GENERAL  VIEW  OF  THE  FUNCTIONS. 

253.  The  regeneration  of  Nervous  tubuli  that  have  been  destroyed,  takes 
place  in  continuity  with  that  which  has  been  left  sound.  This  may  be  more 
easily  proved  by  the  return  of  the  sensory  and  motor  endowments  of  the  part 
whose  nerves  have  been  separated,  than  by  microscopic  examination  of  the 
reunited  trunks  themselves,  which  is  not  always  satisfactory.  All  our  know- 
ledge of  the  functions  of  the  Nervous  System  leads  to  the  belief,  that  perfect 
continuity  of  the  nerve-tubes  is  requisite  for  the  conduction  of  an  impression 
of  any  kind,  whether  this  be  destined  to  produce  motion  or  sensation ;  and 
various  facts,  well  known  to  Surgeons,  prove  that  such  restoration  may  be 
complete.  In  the  various  operations  which  are  practised  for  the  restoration 
of  lost  parts,  a  portion  of  tissue  removed  from  one  spot,  is  grafted  as  it  were 
upon  another ;  its  original  attachments  are  more  or  less  completely  severed, 
frequently  altogether  destroyed,  and  new  ones  are  formed.  Now  in  such  a 
part,  so  long  as  its  original  connections  exist,  and  the  new  ones  are  not  com- 
pletely formed,  the  sensation  is  referred  to  the  spot  from  which  it  was  taken ; 
thus,  when  a  new  nose  is  made,  by  partly  detaching  and  bringing  down  a  piece 
of  skin  from  the  forehead,  the  patient  at  first  feels,  when  anything  touches  the 
tip  of  his  nose,  as  if  the  contact  were  really  with  the  upper  part  of  his  fore- 
head. After  time  has  been  given,  however,  for  the  establishment  of  new 
connections  with  the  parts  into  whose  neighbourhood  it  has  been  brought,  the 
old  connections  of  the  grafted  portion  are  completely  severed,  and  an  interval 
ensues,  during  which  it  frequently  loses  all  sensibility ;  but  after  a  time  its 
power  of  feeling  is  restored,  and  the  sensations  received  through  it  are  referred 
to  the  right  spot. — A  more  familiar  case  is  the  regeneration  of  Skin,  contain- 
ing sensory  nerves,  which  takes  place  in  the  well-managed  healing  of  wounds 
involving  loss  of  substance.  Here  there  must  obviously  be,  not  merely  a  pro- 
longation of  the  nerve-tubes  from  the  subjacent  and  surrounding  trunks,  but 
also  a  formation  of  new  sensory  papillae. — A  still  more  striking  example  of 
the  regeneration  of  Nervous  tissue,  however,  is  to  be  found  in  those  cases  (of 
which  there  are  now  several  on  record),  in  which  portions  of  the  extremities, 
that  have  been  completely  severed  by  accident,  have  been  made  to  adhere  to 
the  stump,  and  have,  in  time,  completely  recovered  their  connection  with  the 
Nervous  as  with  the  other  systems, — as  indicated  by  the  restoration  of  their 
motor  and  sensory  endowments. 


CHAPTER    IV. 

GENERAL    VIEW    OF    THE    FUNCTIONS. 

1.  Of  Vital  Actions,  their  conditions,  and  their  mutual  dependence. 

254.  THE  idea  of  Life,  in  its  simplest  and  most  correct  acceptation,  is  that 
of  Vital  Action  ;  and  obviously,  therefore,  involves  that  of  change.  We  do 
not  consider  any  being  as  alive,  which  is  not  undergoing  some  continual  alte- 
ration, that  may  be  rendered  perceptible  to  the  senses.  This  alteration  may 
be  evidenced  only  by  the  growth  and  extension  of  the  organic  structure,  or 
the  development  of  new  parts  ;  and  it  may  take  place  so  slowly  as  to  be  im- 
perceptible, except  by  comparing  observations  made  at  long  intervals.  Thus 
the  scaly  Lichen,  that  forms  the  grey  or  yellow  spots  upon  old  walls,  might 
be  thought  an  inert  substance,  did  we  not  know  that  a  sufficiently-prolonged 


CONDITIONS  OF  VITAL  ACTIONS.  217 

acquaintance  with  its  history  would  detect  its  progressive  though  tardy  exten- 
sion, and  would  ascertain  that  it  multiplies  its  race  by  an  humble  yet  effectual 
process  of  fructification. — Or  the  change  may  be  rather  evidenced,  by  the 
performance  of  some  kind  of  movement,  for  which  the  ordinary  physical 
laws  of  matter  will  not  account ;  yet,  for  the  detection  of  this,  a  close  and 
careful  scrutiny  will  be  frequently  required.  Thus  the  Oyster  that  is  lying 
motionless  in  its  massive  bed,  or  the  Ascidia  that  clusters  upon  the  faces  of 
sea-beaten  rocks,  may  seem  totally  destitute  of  activity  ;  yet  it  would  be  found 
upon  close  examination,  that  their  internal  surfaces  are  covered  with  cilia 
which  are  in  continual  vibration, — that  by  this  means  water  is  drawn  into 
the  stomach  and  caused  to  traverse  the  respiratory  organs,  yielding  to  the 
former  the  animalcules  it  may  contain,  and  to  the  latter  the  oxygen  dissolved 
in  it, — that  the  food  thus  introduced  into  the  stomach  undergoes  digestion,  and 
is  converted  into  materials  adapted  to  nourish  the  body,  which  are  then  con- 
veyed to  its  different  parts  by  a  circulating  apparatus, — that  in  due  time  em- 
bryos are  produced,  which  are  endowed  with  powers  of  active  motion,  and 
which  swim  forth  from  within  the  parent-envelopes  and  locate  themselves 
elsewhere, — and  that,  apathetic  as  these  creatures  may  seem,  they  may  be 
excited  by  certain  kinds  of  stimuli  to  movements  which  seem  to  evince  sen- 
sation ;  the  Oyster  clbsing  its  shell,  and  the  Ascidia  contracting  its  muscular 
tunic,  when  it  receives  any  kind  of  mechanical  irritation  ;  and  the  former, 
whilst  lying  undisturbed  in  its  native  haunts,  drawing  together  its  valves,  if  a 
shadow  passes  between  itself  and  the  sun. — From  what  has  been  already 
stated,  regarding  the  nature  of  the  actions  of  the  Nervous  and  Muscular  sys- 
tems, by  which  the  movements  of  Animals  are  chiefly  effected,  it  would  ap- 
pear that  these,  in  common  with  the  Vegetative  functions,  involve  a  chemical 
alteration  in  the  structure  performing  them  ;  so  that  it  may  be  stated  as  a 
general  proposition,  that  a  change  in  Chemical  composition  is  an  essential 
condition  of  every  Vital  phenomenon. 

255.  If  change  be  essential  to  our  idea  of  Life,  it  may  be  asked,  what  is 
the  condition  of  a  seed,  which  may  remain  unaltered  during  a  period  of  many 
centuries ;   vegetating  at  last,   when  placed  in  favourable   circumstances,  as 
if  it  had  only  ripened  the  year  before.     Such  a  seed  is  not  alive;  for  it  is  not 
performing  any  vital  operations.     But  it  is  not  dead,  for  it  has  undergone  no 
decay  ;  and  it  is  still  capable  of  being  aroused  into  active  life,  when  the  proper 
stimuli  are  applied.     And  the  most  correct  designation  of  its  state  seems  to 
be  that  of  dormant  vitality. — The  condition  of  an  animal  reduced  to  a  state  of 
complete  torpidity  and  inaction,  is   precisely  similar ;  into   such  a  condition, 
the  Frog  may  be  brought  by  cold,  and  the  Wheel-Animalcule  by  deprivation 
of  moisture.    And  the  condition  of  a  Human  being,  during  sleep,  is  precisely 
similar,  so  far  as  his  psychical  powers  are  concerned  ;  he  is  not  then  a  feel- 
ing, thinking  Man  ;   but  he  is  capable  of  feeling   and  thinking,  when   his 
brain  is  restored  to  a  state  of  activity,  and  its  powers  are  called  into  operation 
by  the  impressions  of  external  objects. 

256.  There  can  be  no  doubt  whatever,  that,  of  the  many  changes  which 
take  place  during  the  life,  or  state  of  vital  activity,  of  an  Organised  being, 
and  which  intervene  between  its  first  development  and  its  final  decay,  a  large 
proportion  are  effected  by  the  direct  agency  of  those  forces  which  operate  in 
the  Inorganic  world;  and  there  is  no  necessity  whatever  for  the  supposition, 
.that  these  forces  have  any  other  operation  in  the  living  body,  than  they  would 
have  out  of  it  under  similar  circumstances. — But  after  every  possible  allowance 
has  been  made  for  the  operation  of  Physical  and  Chemical  forces  in  the  living 
Organism,  there  still  remain  a  large  number  of  phenomena,  which  cannot  be 
in  the  least  explained  by  them  ;  and  which  we  can  only  investigate  with  suc- 
cess, when  we  regard  them  as  resulting  from  the  agency  of  forces,  as  distinct 

19 


218  GENERAL  VIEW  OF  THE  FUNCTIONS. 

from  those  of  Physics  and  Chemistry,  as  these  are  from  each  other.  It  is  to 
such  phenomena,  that  the  name  of  Vital  is  properly  restricted  ;  the  forces 
from  whose  operation  we  assume  them  to  result,  are  termed  vital  forces;  and 
the  properties,  which  we  must  attribute  to  the  substances  exerting  those  forces, 
are  termed  vital  properties. — Thus  we  say  that  the  contraction  of  Muscle  is 
a  Vital  phenomenon  ;  because  its  character  and  conditions  appear  to  be  to- 
tally distinct  from  those  of  Chemical  or  Physical  phenomena.  The  act  is 
the  manifestation  of  a  certain  Force ;  the  possession  of  which  is  peculiar  to 
the  muscular  structure,  and  which  is  named  the  Contractile  force.  Further, 
that  force  may  remain  dormant  (as  it  were)  in  the  muscular  structure ;  not 
manifesting  itself  for  a  great  length  of  time,  and  yet  resting  capable  of  being 
called  into  operation  at  any  moment.  This  dormant  force  is  termed  a  Pro- 
perty ;  thus  we  regard  it  as  the  essential  peculiarity  of  living  muscular  tissue, 
that  it  possesses  the  vital  property  of  Contractility.  Or,  to  reverse  the  order, 
the  Muscle  is  said  to  possess  the  property  of  Contractility ;  the  property, 
called  into  operation  by  the  appropriate  stimulus,  gives  rise  to  the  Contractile 
force ;  and  the  force  produces,  if  its  operation  be  unopposed,  the  act  of  Con- 
traction. 

257.  These  distinctions,  though  apparently  verbal  only,  are  of  importance 
in  leading  us  to  the  correct  method  of  investigating  Vital  Phenomena,  and  of 
comparing  them  with  those  of  the  Inorganic  world.     It  is  now  almost  uni- 
versally admitted  by  intelligent  Physiologists,  that  we  gain  nothing  by  the 
assumption  of  some  general  controlling  agency,  or  Vital  Principle,  distinct 
from  the  organized  structure  itself;  and  that  the  Laws  of  Life  are  nothing  else 
than  general  expressions  of  the  conditions  under  which  Vital  operations  take 
place, — expressions  analogous  to  those  which  constitute  the  laws  of  Physics 
or  Chemistry, — and  to  be  arrived  at  in  the  same  manner,  namely,  by  the  col- 
lection and  comparison  of  phenomena.     The  difficulty  of  thus  generalising  in 
Physiology  results   merely  from  the  complex  nature  of  the  phenomena,  and 
the  consequent  difficulty  of  precisely  determining  their  conditions.     We  have 
as  much  ground  for  believing  in  the  fixity  and  constancy  of  Physiological 
phenomena,  when  the  causes  and  conditions  are  the  same,  as  we  have  in  those 
of  any  other  department  of  science ;  and  the  apparent  uncertainty  of  the 
actions  of  the  living  body,  results  merely  from  the  influence  of  differences  in 
those  conditions,  so  trivial  in  appearance  as  frequently  to  elude  observation, 
and  yet  sufficiently  powerful  in  reality  to  produce  an  entire  change  in  the 
result. 

258.  All  Vital  phenomena  are  dependent  upon  at  least  two  sets  of  condi- 
tions;— an  Organized  structure,  possessed  of  peculiar  properties  ; — and  certain 
Stimuli,  by  which  these  properties  are  called  into  action.     Thus,  to  revert  to 
the   example  just  cited,  the  Contraction  of  a  Muscle  is  due  to  the  inherent 
Contractility  of  the  Muscular  tissue,  called  into  operation  by  the  stimulus  of 
innervation ; — other  conditions,  as  a  certain  elevated  temperature,  a  supply  of 
oxygen,  &c.,  being   at  the    same  time  requisite.     The   Microscopical  and 
Chemical  researches  of  recent  years,  have  given  increased  stability  to  the 
position,  that  the   peculiar   properties,  which  we  term  Vital,  are  dependent 
upon  those  peculiar  modes  of  combination  and  aggregation  of  the  elementary 
particles,  which  are  characteristic  of  Organized  structures.     We  have  no  evi- 
dence of  the  existence  of  Vital  properties  in  any  other  form  of  matter  than 
that  which  we  term  Organized;  whilst,  on  the  other  hand,  we  have  no  reasoa 
to  believe  that  Organized  matter  can  possess  its  normal  constitution,  and  be 
placed   in   the  requisite  conditions,  without  exhibiting  Vital  Actions.     The 
advance  of  Pathological  science  renders  it  every  day  more  probable  (indeed, 
the  probability  may  now  be  said  to  amount  almost  to  positive  certainty),  that 
derangement  m  function, — in  other  words,  an  imperfect  or  irregular  action, — 


CONDITIONS  OF  VITAL  ACTIONS.  219 

always  results,  either  from  some  change  of  structure  or  composition  in  the 
tissue  itself,  or  from  some  corresponding  change  in  the  external  conditions, 
under  which  the  properties  of  the  organ  are  called  into  action.  Thus,  when 
a  Muscle  has  been  long  disused,  it  can  scarcely  be  excited  to  contraction  by 
the  usual  stimulus,  or  may  even  be  altogether  powerless  ;  and  minute  exami- 
nation of  its  structure  shows  it  to  have  undergone- a  change,  which  is  obvious 
to  the  Microscope  (the  fibres  being  as  it  were  shrunken,  and  the  fibrillae  in- 
distinct), though  it  may  not  be  perceptible  to  the  naked  eye,  and  which  results 
from  imperfect  nutrition.  Or,  again,  convulsive  or  irregular  actions  of  the 
Nervous  System  may  be  produced,  not  by  any  change  in  its  own  structure 
or  composition,  but  by  the  presence  of  various  stimulating  substances  in  the 
blood  (such  as  urea  or  strychnine),  although  their  quantity  may  be  so  small, 
that  they  cannot  be  detected  without  great  difficulty.  Further,  whenever  the 
peculiar  properties  of  an  Organized  structure  can  no  longer  be  excited  by  the 
requisite  stimuli,  we  find  that  it  has  undergone  some  incipient  change  of  com- 
position, or  that  some  of  the  other  conditions  are  wanting.  Thus,  the  depar- 
ture of  the  contractility  from  the  muscles  of  warm-blooded  animals,  at  no  long 
period  after  the  cessation  of  the  circulation,  is  due  in  part  to  the  lowering  of 
their  temperature,  and  in  part  to  the  cessation  of  the  supply  of  oxygen  to  the 
elementary  parts  of  their  substance ;  either  of  which  would  alone  suffice  to 
prevent  their  respondence  to  the  stimuli,  that  would  ordinarily  produce  ener- 
getic contractions. — Lastly,  we  find  special  properties  constantly  associated 
with  distinct  forms  of  organized  tissue ;  thus  we  never  find  contractility  exist- 
ing in  the  fibres  of  Nerve ;  nor  do  we  ever  find  the  power  of  conducting 
impressions  to  exist  in  the  fibres  of  Muscle.  The  details  given  in  the  pre- 
ceding Chapter  make  it  evident  that  each  tissue,  distinguished  from  others  by 
its  peculiar  composition,  and  by  the  form  of  its  elementary  parts,  has  some- 
thing peculiar  in  its  properties ;  and  this  is  true,  as  well  of  properties  that  are 
simply  physical,  as  of  those  that  belong  to  a  different  category:  thus  the 
Yellow  Fibrous  tissue  is  distinguished  from  the  White  as  much  by  its  elas- 
ticity, as  by  its  peculiar  composition ;  and  it  does  not  lose  its  elasticity,  until 
it  is  in  a  state  of  evident  decay. 

259.  By  the  study  of  the  various  forms  of  Elementary  Tissue,  of  which 
the  Human  fabric  (or  any  other  of  similar  complexity)  is  made  up,  we  are  led 
to  the  very  same  conclusion,  with  that  which  we  should  derive  from  the 
observation  of  the  simplest  forms  of  organized  being,  or  from  the  scrutiny 
into  the  earliest  condition  of  the  most  complex ; — namely,  that  the  simple 
Cell  may  be  regarded  as  the  type  of  Organization;  and  that  its  actions 
constitute  the  simplest  idea  of  Life.  Between  the  humblest  Oonfervoid  Plant, 
and  the  highest  Animal,  there  is  originally  no  perceptible  difference  ;  they  may 
be  said  to  have  a  common  starting-point ;  and  the  subsequent  difference  of 
their  course  consists  essentially  in  this, — that  the  successive  generations  of 
cells,  which  are  the  descendants  of  the  former,  are  all  similar  to  it,  each  cell 
being  capable  of  existing  by  itself,  and  therefore  ranking  as  an  independent 
individual ;  whilst  the  subsequent  generations,  which  originate  from  the 
latter,  undergo  various  departures  from  the  primary  type,  and  lose  the  power 
of  independent  existence,  their  several  actions  being  mutually  dependent  upon 
each  other,  so  that  the  integrity  of  the  whole  fabric  is  essential  to  the  con- 
tinued life  of  any  individual  cell.  Every  individual  part,  however,  even  in 
the  most  complex  and  highly-organized  fabric,  has  its  own  power  of  develop- 
ment; and  the  properties  which  it  possesses  are  the  result  of  the  exercise  of 
that  power.  But  instead  of  the  power  of  cell-growth  being  exerted,  as  in  the 
Plant,  upon  the  inorganic  elements  around,  it  can  only  be  put  in  action,  in 
the  Animal,  upon  certain  peculiar  compounds,  having  the  same  chemical  com- 
position with  its  own  substance ;  and  it  is  for  the  reception  of  these,  for  their 


220  GENERAL  VIEW  OF  THE  FUNCTIONS. 

preparation,  and  for  their  maintenance  in  the  requisite  state  of  purity,  that  a 
large  part  of  the  fabric  of  the  Animal  is  destined.  But  if  we  could  imagine 
its  several  tissues  to  be  supplied  with  nutriment  in  any  other  manner,  and 
maintained  in  other  respects  in  their  normal  circumstances  (as  regards  warmth, 
air,  &c.),  we  have  every  reason  to  believe  that  their  independent  vitality  would 
manifest  itself  by  their  continued  development,  and  by  the  regular  exhibition 
of  their  ordinary  properties.  An  approach  to  this  condition  is  made,  in  the 
experiment  of  entirely  detaching  a  limb  from  the  body,  but  keeping  up  the 
circulation  of  blood  through  it,  by  means  of  tubes  connecting  its  main  artery 
and  vein  with  those  of  the  stump.  Notwithstanding  the  prejudicial  effect  of 
such  severe  injuries,  the  increased  duration  of  the  muscular  irritability  in  the 
separated  part,  is  a  sufficient  proof  of  the  continuance  of  the  normal  actions  of 
nutrition,  although  of  course  in  a  diminished  degree.  And  the  occasional 
reunion  of  a  member  which  has  been  entirely  separated,  when  decomposing 
changes  have  not  yet  commenced  in  it,  most  clearly  shows,  that  nothing  but 
the  restoration  of  its  supply  of  nutriment  is  requisite  for  the  preservation  of 
its  vitality,  and  that  its  powers  of  growth  and  renovation  are  inherent  in  itself, 
only  requiring  a  due  supply  of  the  nutrient  material,  with  certain  other  con- 
current conditions. 

260.  In  every  living  structure  of  a  complex  nature,  therefore,  we  see  a  great 
variety  of  actions,  resulting  from  the  exercise  of  the  different  properties  of  its 
several  component  parts.     If  we  take  a  general  survey  of  them,  with  reference 
to  their  mutual  relations  to  each  other,  we  shall  perceive  that  they  may  be 
associated  into  groups;  each  consisting  of  a  set  of  actions,  which,  though 
different  in  themselves,  concur  in  effecting  some  positive  and  determined  pur- 
pose.    These  groups  of  actions  are  termed  Functions.     Thus,  one  of  the 
most  universal  of  all  the  changes  necessary  to  the  continued  existence  of  a 
living  being,  is  the  exposure  of  its  nutritious  fluid  to  the  air;  by  the  action  of 
which  upon  it,  certain  alterations  are  effected.     For  the  performance  of  this 
aeration,  simple  as  the  change  appears,  many  provisions  are  required.    In  the 
first  place,  there  must  be  an  aerating  surface,  consisting  of  a  thin  membrane, 
permeable  to  gases ;  on  the  one  side  of  which  the  blood  may  be  spread  out, 
whilst  the  air  is  in  contact  with  the  other.     Then  there  must  be  a  provision 
for  continually  renewing  the  blood  which  is  brought  to  this  surface;  in  order 
that  the  whole  mass  of  fluid  may  be  equally  benefited  by  the  process.     And, 
in  like  manner,  the  stratum  of  air  must  also  be  renewed,  as  frequently  as  its 
constituents  have  undergone  any  essential  change.     We  include,  therefore,  in 
speaking  of  the  Function  of  Respiration,  not  only  the  actual  aerating  process, 
but  also  the  various  changes  which  are  necessary  to  carry  this  into  effect,  and 
which  obviously  have  it  for  their  ultimate  purpose. 

261.  On  further  examining  and  comparing  these  Functions,  we  find  that 
they  are  themselves  capable  of  some  degree  of  classification.     Indeed  the  dis- 
tinction between  the  groups  into  which  they  may  be  arranged,  is  one  of  essen- 
tial importance  in  Animal  Physiology.     If  we  contemplate  the  history  of  the 
Life  of  a  Plant,  we  perceive  that  it  grows  from  a  germ  to  a  fabric  of  sometimes 
gigantic  size, — generates  a  large  quantity  of  organised  structure,  as  well  as 
many  organic  compounds,  which  form  the  products  of  secretion,  but  which  do 
not  undergo  organization, — and  multiplies  its  species,  by  the  production  of 
germs  similar  to  that  from  which  it  originated; — but  that  it  performs  all  these 
complex  operations,  without  (so  far  as  we  can  perceive)  either  feeling  or  think- 
ing, without  consciousness  or  will.    All  the  functions  of  which  its  Life  is  com- 
posed, are,  therefore,  grouped  together  under  the  general  designation  of  Func- 
tions of  Organic  or  Vegetative  life :  and  they  are  subdivided  into  those  con- 
cerned in  the  maintenance  of  the  structure  of  the  individual,  which  are  termed 
functions  of  Nutrition  ;  and  those  to  which  the  Reproduction  of  the  species 


CLASSIFICATION  OF  VITAL  ACTIONS  INTO  FUNCTIONS.  221 

is  due. — The  great  feature  of  the  Nutritive  operations  in  the  Plant,  is  their 
constructive  character.  They  seem  as  if  destined  merely  for  the  building-up 
and  extension  of  the  fabric;  and  to  this  extension  there  may  be  no  definite 
limit.  But  it  is  very  important  to  remark,  that  the  growth  of  the  more  per- 
manent parts  of  the  structure  is  only  attained  by  the  continual  development, 
decay,  and  renewal  of  parts,  whose  existence  is  temporary.  No  fact  is  better 
established  in  Vegetable  Physiology,  than  the  dependence  of  the  formation  of 
wood  upon  the  action  of  the  leaves.  It  is  in  their  cells,  that  those  important 
changes  are  effected  in  the  sap,  by  which  it  is  changed,  from  a  crude  watery 
fluid  containing  very  little  solid  matter,  to  a  viscid  substance  including  a  great 
variety  of  organic  compounds,  destined  for  the  nutrition  of  the  various  tissues. 
The  "fall  of  the  leaf"  results  merely  from  the  death  and  decay  of  its  tissue; 
as  is  evident  from  the  fact,  that,  for  some  time  previously,  its  regular  functions 
cease,  and  that,  instead  of  a  fixation  of  carbon  from  the  atmosphere,  there  is  a 
liberation  of  carbonic  acid  (a  result  of  their  decomposition)  in  large  amount. 
The  process  takes  place  in  evergreens  equally  with  deciduous  trees ;  the  only 
difference  being,  that  the  leaves  in  the  latter  are  all  cast  off  and  renewed  to- 
gether, whilst  in  the  former  they  are  continually  being  shed  and  replaced,  a 
few  at  a  time.  It  appears  as  if  the  nutritious  fluid  of  the  higher  Plants  can 
only  be  prepared  by  the  agency  of  cells,  whose  duration  is  brief;  for  we  have 
n'o  instance,  in  which  the  tissue  concerned  in  its  elaboration  possesses  more 
than  a  very  limited  term  of  existence.  But  by  its  active  vital  operations,  it 
produces  a  fluid  adapted  for  the  nutrition  of  parts  which  are  of  a  much  more 
solid  and  permanent  character,  and  which  undergo  little  change  of  any  kind 
subsequently  to  their  complete  development ; — the  want  of  tendency  to  decay 
being  the  result  of  the  very  same  peculiarity  of  constitution  as  that  which 
renders  them  unfit  to  participate  in  the  proper  vital  phenomena  of  the  organism. 
Thus  the  final  cause  or  purpose  of  all  the  Nutritive  functions  of  the  Plant,  so 
far  as  the  individual  is  concerned,  is  to  produce  an  indefinite  extension  of  the 
dense,  woody,  almost  inert,  and  permanent  portions  of  the  fabric,  by  the  con- 
tinued development,  decay,  and  renewal  of  the  soft,  active,  and  transitory 
cellular  parenchyma. — The  Nutritive  functions,  however,  also  supply  the 
materials  for  the  continuance  of  the  r«ce,  by  the  generation  of  new  individuals; 
since  a  new  germ  cannot  be  formed,  any  more  than  the  parent  structure  can 
be  extended,  without  organizable  materials,  prepared  by  the  assimilating  pro- 
cess, and  supplied  to  the  parts  where  active  changes  are  going  on. 

262.  On  analyzing  the  operations  which  take  place  in  the  Animal  body,  we 
find  that  a  large  number  of  them  are  of  essentially  the  same  character  with  the 
foregoing,  and  differ  only  in  the  conditions  under  which  they  are  performed  ; 
so  that  we  may,  in  fact,  readily  separate  the  Organic  functions,  which  are 
directly  concerned  in  the  development  and  maintenance  of  the  fabric,  from  the 
Jlnimal  functions,  which  render  the  individual  conscious  of  external  impres- 
sions, and  capable  of  executing  spontaneous  movements.  The  relative  de- 
velopment of  the  organs  destined  to  these  two  purposes,  differs  considerably 
in  the  several  groups  of  Animals,  as  we  have  already  in  part  seen  (Chap.  I.). 
The  life  of  a  Zoophyte  is  upon  the  whole  much  more  vegetative  than  animal ; 
and  we  perceive  jn  it,  not  merely  the  very  feeble  development  of  those  powers 
which  are  peculiar  to  the  Animal  kingdom,  but  also  that  tendency  to  indefinite 
extension  which  is  characteristic  of  the  Plant.  In  the  Insect  we  have  the 
opposite  extreme ;  the  most  active  powers  of  motion,  and  sensations  of  which 
some  (at  least)  are  very  acute,  with  a  low  development  of  the  organs  of  nutri- 
tion. In  Man,  and  in  the  higher  classes  generally,  we  have  less  active  powers 
of  locomotion,  but  a  much  greater  variety  of  Animal  powers  ;  and  the  instru- 
ments of  the  organic  or  nutritive  operations  attain  their  highest  development, 
and  their  greatest  degree  of  mutual  dependence.  "We  see  in  the  fabric  of  all 

19* 


222  GENERAL  VIEW  OF  THE  FUNCTIONS. 

things,  in  which  the  Animal  powers  are  much  developed,  an  almost  entire 
want  of  that  tendency  to  indefinite  extension,  which  is  so  characteristic  of  the 
Plant;  and  when  the  large  amount  of  food  consumed  by  them  is  considered, 
the  question  naturally  arises,  to  what  purpose  this  food  is  applied,  and  what 
is  the  necessity  for  the  continued  activity  of  the  Organic  functions,  when  once 
the  fabric  has  attained  the  limit  of  its  development. 

263.  The  answer  to  this  question  lies  in  the  fact,  that  the  exercise  of  the 
Minimal  functions  is  essentially  destructive  of  their  instruments  ;  every  ope- 
ration of  the  Nervous  and  Muscular  systems  requiring,  as  its  necessary  con- 
dition, a  disintegration  of  a  certain  part  of  their  tissues,  probably  by  their  ele- 
ments being  caused  to  unite  with  oxygen.     The  duration  of  the  existence  of 
those  tissues  (as  stated  in  the  preceding  Chapter)  varies  inversely  to  the  use 
that  is  made  of  them ;  being  less  as  their  functional  activity  is  greater.     Hence, 
when  an  Animal  is  very  inactive,  it  requires  but  little  nutrition ;  if  in  mode- 
rate activity,  there  is   a  moderate   demand  for  food  ;  but  if  its  Nervous  and 
Muscular  energy  be  frequently  and  powerfully  aroused,  the  supply  must  be 
increased,  in  order  to  maintain  the  vigour  of  the  system.     In  like  manner,  the 
amount  of  certain  products  of  excretion,  which  result  from  the  disintegration 
of  the  Nervous  and  Muscular  tissues,  increases  with  their  activity,  and  dimin- 
ishes in  proportion  to  their  freedom  from  exertion.*     We  are  not  to  measure 
the  activity  of  the  Nervous  system,  however,  like  that  of  the  Muscular,  only 
by  the  amount  of  movement  to  which  it  gives  origin.     For  there  is  equal  evi- 
dence, that  the  demand  for  blood  in  the  brain,  the  amount  of  nutrition  it  re- 
ceives, and  the  degree  of  disintegration  it  undergoes,  are  proportional  likewise 
to  the  energy  of  the  purely  psychical  operations  ;  so  that  the  vigorous  exercise 
of  the  intellectual  powers,  or  a  long-continued  state  of  agitation  of  the  feelings, 
produces  as  great  a  waste  of  Nervous  matter,  as  is  occasioned  by  active  bodily 
exercise.     From  this  and  other  considerations,  we  are  almost  irresistibly  led 
to  the  belief,  that  every  act  of  Mind  is  inseparably  connected,  in  our  present 
state  of  being,  with  material  changes  in  the  Nervous  System;  a  doctrine  not 
in  the  least  inconsistent  with  the  belief  in  the  separate  immaterial  existence  of 
the  Mind  itself,  nor  with  the  expectation  of  a  future  state,  in  which  the  com- 
munion of  Mind  with  Mind  shall  be  more  direct  and  unfettered. 

264.  Thus  in  the  Animal  fabric,  among  the  higher  classes  at  least,  the  func- 
tion or  purpose  of  the  organs  of  Vegetative  life  is  not  so  much  the  extension 
of  the  fabric,  for  this  has  certain  definite  limits,  as  the  maintenance  of  its  in- 
tegrity, by  the  reparation  of  the  destructive  effects  of  the  exercise  of  the 
purely  Animal  powers.     Thus,  by  the  operations  of  Digestion,  Assimilation, 
and  Circulation,  the  nutritious  materials  are  prepared  and  conveyed  to  the 
points  where  they  are  required  ;  the  Circulation  of  Blood  also  serves  to  convey 
oxygen,  which  is  introduced  by  the  Respiratory  process ;  and  it  has  further 
for  its  office  to  convey  away  the  products  of  the  decomposition  of  the  Muscular 
and  Nervous  tissues  that  results  from  their  functional  activity, — these  products 
being  destined  to  be  separated  by  the  Respiratory  and  other  Excreting  opera- 
tions.    In  the  performance  of  the  Organic  functions  of  Animals,  as  in  those 
of  Plants,  there  is  a  continual  new  production,  decay,  exuviation,  and  renewal, 
of  the  cells,  by  whose  instrumentality  they  are  effected  ;  which  altogether  effect 
a  change  not  less  complete  than  of  the  leaves  in  Plants.     But  it  takes  place  in 
the  penetralia  of  the  system,  in  such  a  manner  as  to  elude  observation,  except 
that  of  the  most  scrutinizing  kind ;  and  it  has  been  in  bringing  this  into  view, 
that  the  Microscope  has  rendered  most  essential  service  in  Physiology. 

*  This  doctrine,  though  propounded  in  general  terms  by  previous  writers,  was  first  point- 
edly stated  by  Prof.  Liebig,  so  far  as  regards  Muscular  tissue,  in  his  Treatise  on  Animal 
Chemistry.  It  will  be  hereafter  shown,  however,  to  be  equally  applicable  to  the  Nervous 
substance. 


MUTUAL  DEPENDENCE  OF  VITAL  OPERATIONS.  223 

265.  The  regular  maintenance  of  the  functions  of  Animal  life  is  thus  entirely 
dependent  upon  the  due  performance  of  the  Nutritive  operations ;  a  considera- 
tion of  great  importance  in  practice,  since  a  very  large  proportion  of  what  are 
termed  functional  disorders  (of  the  Nervous  system  especially)  are  immediately 
dependent  upon  some  abnormal  condition  of  the  Blood.     But  there  also  exists 
a  connection  of  an  entirely  reverse  kind,  between  the  Organic  and  Animal  func- 
tions; for  the  conditions  of  Animal  existence  render  the  former  in  great  degree 
dependent  on  the  latter.     Thus,  in  regard  to  the  acquisition  of  food,  the  Animal 
has  to  make  use  of  its  senses,  its  psychical  faculties,  and  its  power  of  locomotion, 
to  obtain  that  which  the  Plant,  from  the  different  provision  made  for  its  support, 
can  derive  without  any  such  assistance.    Moreover,  the  propulsion  of  the  food 
along  the  alimentary  canal  is  effected  by  a  series  of  operations,  in  which  the 
Nervous  and  Muscular  systems  are  together  involved  at  the  two  extremes ; 
though  simple  Muscular  contractility  is  alone  employed  through  the  greater 
part  of  the  intestinal  canal.     Thus,  the  change  in  the  conditions  required  for 
the  ingestion  of  food  by  Animals,  has  rendered  necessary  the  introduction  of 
an  additional  element  in  the  apparatus,  to  which  nothing  comparable  was  to 
be  found  in  Plants.    Again,  in  the  function  of  Respiration  as  performed  in  the 
higher  Animals,  the  Nervous  and  Muscular  systems  are  alike  involved;  for  the 
movements,  by  which  the  air  in  the  lungs  is  being  continually  renewed,  are 
dependent  upon  the  action  of  both  ;  and  those  by  which  the  blood  is  propelled 
through  the  respiratory  organs,  are  chiefly  occasioned  by  the  contractility  of  a 
muscular  organ, — the  heart.    But  in  regard  to  the  simple  contractility  of  mus- 
cular fibre,  upon  the  direct  application  of  a  stimulus  to  it,  which  is  the  agent 
in  the  movements  of  the  heart  and  of  the  alimentary  canal,  it  may  be  remarked, 
that  it  does  not  differ  in  any  essential  particular  from  that  which  is  witnessed 
in  many  Vegetables :  so  that  it  strictly  belongs  to  the  functions  of  Organic  life. 
And  with  respect  to  those  concerned  in  the  act  of  Respiration,  as  well  as  those 
which  govern  the  two  orifices  of  the  alimentary  tube,  it  will  hereafter  appear 
that  they  result,  equally  with  the  former,  from  the  application  of  a  stimulus ; 
and  that  they  may  be  performed  without  any  consciousness  on  the  part  of  the 
individual  (though  ordinarily  accompanied  by  it) : — the  difference  being,  that 
in  the  former  the  stimulus  is  applied  to  the  contractile  part  itself,  whilst  in  the 
latter  it  is  applied  to  an  organ  with  which  this  is  connected  by  nerves  only. 
Now  we  have,  even  in  Vegetables,  instances  of  the  propagation  of  an  irritation 
from  one  part  to  another,  so  that  a  motion  results  in  a  part  distant  from  that 
stimulated, — as  in  the  case  of  the  Sensitive  Plant  or  Venus's  Fly-trap.     The 
only  essential  difference,  therefore,  between  those  movements  of  Animals, 
which  are  thus  closely  connected  with  the  maintenance  of  the  organic  func- 
tions, and  those  of  Plants,  consists  in  the  medium  through  which  they  are 
performed, — this  being  in  Animals  a  distinct  Nervous  and  Muscular  apparatus, 
whilst  in  Plants  it  is  only  a  peculiar  modification  of  the  ordinary  structure. 

266.  From  what  has  been  said,  then,  it  appears  that  all  the  functions  of  the 
Animal  body  are  so  completely  bound  up  together,  that  none  can  be  suspended 
without  the  cessation  of  the  rest.     The  properties  of  all  the  tissues  and  organs 
are  dependent  upon  their  regular  Nutrition,  by  a  due  supply  of  perfectly-ela- 
borated blood ;  this  cannot  be   effected  unless  the  functions  of  Circulation, 
Respiration,  and  Secretion,  be  performed  with  regularity, — the  first  being  ne- 
cessary to  convey  the  supply  of  nutritious  fluid,  and  the  two  latter  to  separate 
it  from  its  impurities.     The  Respiration  cannot  be  maintained  without  the  in- 
tegrity of  a  certain  part  of  the  nervous   system;  and  the  due  action  of  this, 
again,  is  dependent  upon  its  regular  nutrition.     The  materials  necessary  for 
the  replacement  of  those  which  are  continually  being  separated  from  the  blood, 
can  only  be  derived  by  the  Absorption  of  ingested  aliment ;  and  this  cannot 
be  accomplished  without  the  preliminary  process  of  Digestion.     The  intro- 


224  GENERAL  VIEW  OF  THE  FUNCTIONS. 

duction  of  food  into  the  stomach,  again,  is  dependent,  like  the  actions  of  Re- 
spiration, upon  the  operations  of  the  muscular  apparatus  and  of  a  part  of  the 
nervous  centres;  and  the  previous  acquirement  of  food  necessarily  involves 
the  purely  Animal  powers.  Now  it  will  serve  to  show  the  distinction  between 
these  powers,  and  those  which  are  merely  subservient  to  Organic  life,  if  we 
advert  to  thfe  case,  which  is  of  no  unfrequent  occurrence,  of  a  human  being, 
deprived,  by  some  morbid  condition  of  the  brain,  of  all  the  powers  of  Animal 
life, — Sensation,  Thought,  Volition,  &c. ;  and  yet  capable  of  maintaining  a 
vegetative  existence, — all  the  organic  functions  going  on  as  usual,  the  morbid 
condition  not  having  affected  the  division  of  the  nervous  system,  that  is  con- 
cerned in  the  movements  on  which  some  of  them  depend.  It  is  evident  that 
we  can  assign  no  definite  limits  to  such  a  state,  so  long  as  the  necessary  food 
is  placed  within  reach  of  the  grasp  of  the  muscles,  that  will  convey  it  into  the 
stomach ;  as  a  matter  of  fact,  however,  it  is  seldom  of  long  continuance  ; 
since  the  disordered  state  of  the  brain  is  sure  to  extend  itself,  sooner  or  later, 
to  the  rest  of  the  nervous  system.  This  condition  may  be  experimentally 
imitated,  however,  by  the  removal  of  the  brain  in  many  of  the  lower  animals, 
whose  bodies  will  sustain  life  for  many  months  after  such  a  mutilation ;  but 
this  can  only  take  place  when  that  food  is  conveyed  by  external  agency 
within  the  pharynx,  which  they  would,  if  in  their  natural  condition,  have  ob- 
tained for  themselves.  A  similar  experiment  is  sometimes  made  by  Nature 
for  the  Physiologist,  in  the  production  of  fetuses,  as  well  of  the  human  as  of 
other  species,  in  which  the  brain  is  absent ;  these  can  breathe  and  suck  and 
swallow,  and  perform  all  their  organic  functions  ;  and  there  is  no  assignable 
limit  to  their  existence,  so  long  as  they  are  duly  supplied  with  food.  Hence 
we  may  learn  the  exact  nature  of  the  dependence  of  the  Organic  functions 
upon  those  of  purely  Animal  life ;  and  we  perceive  that,  though  less  imme- 
diate than  it  is  upon  the  simple  organic  operations  of  the  nervous  and  muscu- 
lar systems,  it  'is  not  less  complete.  On  the  other  hand,  the  functions  of 
Animal  life  are  even  more  closely  dependent  upon  the  Nutritive  actions  than 
are  those  of  organic  life  in  general ;  for  many  tissues  will  retain  their  several 
properties,  and  their  power  of  growth  and  extension,  for  a  much  longer  pe- 
riod after  a  general  interruption  of  the  circulation,  than  will  the  Nervous 
structure  ;  which  is,  indeed,  instantaneously  affected  by  a  cessation  of  the  due 
supply  of  blood,  or  by  the  depravation  of  its  quality. 

267.  It  is  of  little  consequence,  then,  with  which  group  of  functions  we 
commence  the  detailed  study  of  the  phenomena,  which  in  their  totality  make 
up  the  life  of  Man.     In  viewing  him  merely  as  one  of  the  widely-extended 
group  of  organized  beings,  it  would  be  natural  to  commence  with  those  phe- 
nomena which  are  common  to  all ;  and  to  make,  therefore,  the  Organic  func- 
tions the  first  object  of  our  consideration.     On  the  other  hand,  regarding  Man 
as  a  being  in  some  degree  isolated  from  all  these  by  his  peculiar  character- 
istics, it  seems  right  to   inquire  into  the  latter  in  the  first  instance ;    more 
especially  as,  in  a  general  view  of  his  life,  these  occupy  the  most  prominent 
place.     It  will  be  necessary,  however,  previously  to  entering  upon  them,  to 
take  a  more  detailed  survey  than  we  have  hitherto  done,  of  the  vital  opera- 
tions performed  by  his  several  organs,  and  of  their  connections  with  each 
other.     We  shall  commence  with  those  of  Vegetative  Life. 

2.  Functions  of  Vegetative  Life. 

268.  It  is  one  of  the  most  peculiar  characteristics  of  Organized  structure, 
that  its  elements  have  a  constant  tendency  (under  ordinary  circumstances  at 
least)  to  separate  into  more  simple  combinations ;  and  although  it  has  been 
ordinarily  considered,  that  their  living  state  prevents  such  a  change,  and  that 


FUNCTIONS  OF  ORGANIC  OR  VEGETATIVE  LIFE.  225 

they  have  no  tendency  to  it  except  when  dead,  reason  will  hereafter  be  given 
for  the  belief  that  no  such  distinction  exists  (Chap.  XIV.,  Sect.  4).  The 
maintenance  of  the  vital  properties  of  all  organized  structure  then,  requires 
either  that  this  structure  should  be  completely  secluded  from  air,  moisture, 
warmth,  and  other  agents  which  tend  to  its  decomposition;  or  that  it  should 
be  renewed  as  fast  as  it  decays.  Now  the  exclusion  of  these  decomposing 
agents  would  prevent  any  vital  actions  from  being  called  into  operation; 
since  they  are  the  ordinary  stimuli  which  are  necessary  to  them.  For 
instance,  a  seed  which  is  buried  so  deep  in  the  soil  as  to  be  excluded  from 
the  contact  of  air,  and  from  the  warmth  of  the  sun,  will  not  vegetate,  although 
it  may  retain  its  power  of  germinating  when  placed  in  more  favourable  cir- 
cumstances ;  and  it  will  not  decay,  because  secluded  from  the  air  and  warmth 
which  are  necessary  to  its  decomposition.  But  as  a  certain  change  of  com- 
position appears  to  be  a  necessary  condition  of  its  vital  activity,  it  is  obvi- 
ously requisite  that  a  provision  should  be  made,  for  removing  from  the 
organism  all  those  particles  which  are  manifesting  an  incipient  tendency  to 
decay,  and  are  thus  losing  their  vital  properties ;  and  for  replacing  these  by 
newly-combined  particles,  which  in  their  turn  undergo  the  same  process. 
Thus  we  find  that,  in  the  softest  parts  of  the  Animal  frame-work,  as  in  those 
of  the  Plant,  there  is  much  less  permanency  than  there  is  in  those  harder  and 
more  solid  portions,  which  often  seem  altogether  to  defy  the  lapse  of  time. 
Now  it  is  in  the  former  that  the  most  active  vital  changes  take  place, — those 
of  the  nervous  system,  for  example;  whilst  of  the  latter,  the  function  is 
chiefly,  if  not  entirely,  that  of  giving  mechanical  support  to  the  structure. 
The  former  organs  are  renewed  many  times,  whilst  the  fabric  of  the  latter  is 
not  once  completely  changed;  and  thus  a  very  interesting  correspondence  is 
shown  between  the  degree  in  which  the  action  of  any  organized  structure  is 
removed  from,  or  is  similar  to,  that  of  a  mere  inorganic  substance,  and  the 
amount  of  tendency  to  decomposition  which  that  structure  exhibits ;  since 
this  constant  renewal  can  scarcely  serve  any  other  purpose  than  that  of 
making  up  for  the  effects  of  decay. 

269.  One  of  the  most  important  purposes  of  the  supply  of  aliment,  there- 
fore, which  all  living  beings  continually  require,  is  the  replacement  of  the 
portions  of  the  fabric  that  are  thus  lost.  The  effects  of  the  process  of  decay, 
when  uncompensated  by  that  of  renovation,  are  remarkably  seen  in  cases  of 
starvation ;  for  it  is  a  very  constant  indication  of  this  condition,  that  the  body 
exhales  a  putrescent  odour,  even  before  death,  and  that  it  subsequently  passes 
very  rapidly  into  decomposition.  This,  it  may  be  considered,  is  the  reason 
why  a  constant  supply  of  aliment  is  still  required  for  the  maintenance  of 
every  organic  structure,  though  it  may  have  arrived  at  its  full  growth;  and  it 
also  affords  one  source  of  explanation  of  the  fact,  that  old  people  require  less 
food  than  adults,  since  their  tissues  are  more  consolidated,  and  thus  become 
at  the  same  time  unable  to  perform  their  usual  actions  with  their  pristine 
energy,  whilst  their  tendency  to  decomposition  is  less.  In  the  growing  state, 
however,  an  additional  important  source  of  demand  for  food  obviously  exists, 
in  the  extension  which  the  tissues  themselves  are  constantly  receiving ;  yet 
this,  perhaps,  does  not  make  so  great  a  difference,  as  it  appears  to  do,  in  the 
supply  which  is  requisite.  For  if  the  addition  which  is  made  by  growth  to 
the  body  in  any  given  time,  be  compared  with  the  amount  of  exchange  which 
has  taken  place  in  the  same  time. — the  latter  being  judged  of  by  the  quantity 
of  matter  excreted  from  the  lungs,  liver,  kidneys,  skin,  &c., — it  will  be  found 
to  bear  but  a  very  small  proportion  to  it;  except  during  foetal  life,  when  the 
growth  is  very  rapid,  and  a  large  proportion  of  the  effete  particles  are  com- 
municated to  the  maternal  blood,  to  be  excreted  from  it.  The  real  cause  of 
the  increased  demand  for  nutriment,  during  the  early  part  of  life,  is  rather 


226  GENERAL  VIEW  OF  THE  FUNCTIONS. 

this, — that  the  tissues  are  far  from  having  acquired  that  firmness  and  consoli- 
dation which  they  gain  at  adult  age;  and  that  they  are,  therefore,  more  prone 
to  decomposition,  at  the  same  time  that  their  vital  activity  is  greater,  as  is  well 
known  to  be  the  case. — The  feeling  of  hunger  or  desire  for  food  originates, 
we  shall  hereafter  find  reason  to  believe  (Chap.  X.,  Sect.  1),  not  so  much  in 
the  stomach  itself,  as  in  the  system  at  large;  of  whose  condition,  in  regard  to 
the  requirement  of  an  increased  supply  of  aliment,  it  may,  during  the  state  of 
health,  be  considered  as  a  pretty  faithful  index.  The  same  may  be  said  of 
thirst.  The  feeling  of  hunger,  then,  is  the  stimulus  to  the  mental  operations, 
which  have  for  their  object  the  acquisition  of  food;  whether  these  be  of  a 
voluntary  or  of  a  purely  instinctive  kind.  In  Man  they  are  obviously  the 
former,  during  all  but  infant  life. 

270.  The  food  received  into  the  mouth,  and  prepared  there  by  the  acts  of 
mastication  and  insalivation  (the  movements  concerned  in  which  are  dependent 
upon  the  brain,  and  can  only  be  performed  when  it  is  in  a  condition  of  some 
activity),  is  brought  by  them  within  reach  of  the  pharyngeal  muscles,  whose 
contraction  cannot  be  effected  by  the  will,  but  is  purely  excilo-motor, — result- 
ing merely  from  the  impression  made  upon  the  fauces  by  the  contact  Sf  the 
substance  swallowed,  which  impression  is  conveyed  to  the  medulla  oblongata 
and  reflected  back  to  the  muscles  (§  383).     By  these  it  is  propelled  down 
the  oesophagus ;  and,  after  their  action  has  ceased,  it  is  taken  up  (as  it  were) 
by  the  muscular  coat  of  the  oesophagus  itself,  and  conveyed  into  the  stomach. 
How   far  the  movements  of  the  lower  parts  of  the  oesophagus   and   of  the 
stomach  are   in  Man   dependent  upon  reflex   action,  is  uncertain;  the  facts 
which  have  been  ascertained  on  this  point,  by  experiment  on  animals,  will  be 
detailed  in  their  proper  place  (§  390).     In  the  stomach  the  food  is  subjected 
to  the  gastric   secretion ;  the   chemical   action  of  which,  aWed   by  the   con- 
stantly-elevated temperature  of  the  interior  of  the  body,  and  by  the  continual 
agitation  effected  by  the   contractions  of  the  parietes  of  the   organ,  effects  a 
more  or  less  complete  solution  of  it.     The   mixture  of  the  biliary  and  pan- 
creatic secretions  with  the  chyme  thus  produced,  occasions  a  separation  of  its 
elements  into  those  adapted  for  nutrition,  and  those  of  which  the  character  is 
excrementitious ;  and  this  separation  can   scarcely  be  regarded  in  any  other 
light  than  as  a  chemical   precipitation.     By  the   agency  of  the  biliary  secre- 
tion, moreover,  certain  elements  of  the  food  that  would  otherwise  be  rejected, 
are  reduced  to  a  form  in  which  they  can  be  absorbed.     The  nutritious  por- 
tion is  taken  up  by  the  Blood-vessels  and  by  the  Absorbent  vessels  (or  Lac- 
teals),  which  are  distributed  on  the  walls  of  the  alimentary  canal ;  whilst  the 
remainder  is  propelled  along  the  intestinal  tube  by  the  simple  contractility  of 
its  walls,  undergoing  at  the   same   time   some  further  change,  by  which  the 
nutritive  materials  are  still  more  completely  extracted  from  it.     And  at  last, 
the  excrementitious   matter, — consisting  not  only  of  a  portion  of  the  food 
taken  into  the  stomach,  but  also  of  part  of  the  secretion  of  the  liver,  and  of 
that  of  the  mucous  surface  of  the  intestines  and  of  their  glandulse, — is  avoided 
from  the  opposite   extremity  of  the   canal,  by  a  muscular  exertion,  which  is 
partly  reflex,  like  that  of  deglutition,  but  is  partly  voluntary,  especially  (as  it 
would  appear)  in  Man. 

271.  There  seems  no  doubt  that  fluid  containing  saline,  albuminous,  or 
other  soluble  matters,  may  be  absorbed  by  the  Blood-vessels,  with  which  the 
mucous  membrane  of  the  alimentary  canal  is  so  copiously  supplied ;  and  this 
simple  process  of  Imbibition  probably  takes  place  according  to  the  physical 
laws  of  Endosmose.     But  the  Selection  and  Absorption  of  certain  nutritious 
elements  appear  to  be  performed,  not  by  vessels,  but  by  the  growth  and  de- 
velopment of  cells  (§  181);  which,  by  their  subsequent  disintegration,  give  it 
up  to  the  Lacteals.     The  absorbed  fluid,  which  now  receives  the  name  of 


FUNCTIONS  OF  ORGANIC  OR  VEGETATIVE  LIFE.  227 

Chyle,  is  propelled  through  the  Lacteals,  by  the  contractility  of  their  walls  ; 
aided  in  part,  perhaps,  by  a  vis  a  tergo  derived  from  the  force  of  the  absorp- 
tion itself.  With  the  reception  of  the  nutritious  fluid  into  the  absorbent  ves- 
sels, commences  its  real  preparation  for  Organization.  Up  to  that  period,  it 
cannot  be  said  to  be  in  any  degree  vitalised;  the  changes  which  it  has  under- 
gone being  only  of  a  chemical  and  physical  nature,  and  such  as  merely  prepare 
it  for  subsequent  assimilation.  But  in  its  passage  through  the  long  and  tor- 
tuous system  of  absorbent  vessels  and  glands,  it  undergoes  changes  which, 
with  little  chemical  difference,  manifest  themselves  by  a  decided  alteration  in 
its  properties  ;  so  that  the  chyle  of  the  thoracic  duct  is  evidently  a  very  dif- 
ferent fluid  from  the  chyle  of  the  lacteals,  approaching  much  nearer  to  blood 
in  its  general  characters.  These  characters  are  such  as  indicate  that  the  pro- 
cess of  organization  and  vitilization  has  commenced;  as  may  be  known  alike 
from  the  microscopic  appearance  of  the  fluid,  and  from  the  actions  it  per- 
forms when  removed  from  the  body.  There  is  reason  to  believe  that  the 
changes,  which  the  Chyle  undergoes  in  its  progress  through  the  lacteals,  are 
due  to  the  action  of  certain  cells  which  are  seen  to  be  diffused  through  the 
liquid  (§  155) ;  these,  by  their  own  independent  powers  of  growth,  are  con- 
tinually absorbing  into  themselves  the  fluid  in  which  they  float ;  whilst,  by 
bursting  or  liquefying,  as  soon  as  their  term  of  life  is  completed,  they  give 
this  back  in  an  altered  state.  The  Chyle  thus  modified  is  conveyed  into  the 
Sanguiferous  system  of  vessels,  and  flows  directly  to  the  heart;  by  which  it  is 
transmitted  with  the  mass  of  the  blood,  to  the  lungs.  It  there  has  the  oppor- 
tunity of  excreting  its  superfluous  carbonic  acid,  and  of  absorbing  oxygen  ; 
and  probably  acquires  gradually  the  properties,  by  which  the  blood  previous- 
ly formed  is  distinguished, — thus  becoming  the  pabulum  vitse  for  the  whole 
system. 

272.  The  Circulation  of  the  Blood  through  the  tissues  and  organs  which 
it  is  destined  to  support,  is  a  process  evidently  necessary  for  the  conveyance 
to  them  of  the  nutritious  materials,  which  are  provided  for  the  repair  of  their 
waste  ;  and  for  the  removal  of  those  elements  of  their  fabric,  which  are  in  a 
state  of  incipient  decomposition.  In  the  lowest  classes  of  organized  beings, 
every  portion  of  the  structure  is  in  direct  relation  with  its  nutritive  materials  ; 
it  can  absorb  for  itself  that  which  is  required  ;  and  it  can  readily  part  with 
that  of  which  it  is  desirable  to  get  rid.  Hence  in  such,  no  general  circulation 
is  necessary.  In  Man,  on  the  other  hand,  the  digestive  cavity  occupies  so 
small  a  portion  of  the  body,  that  the  organs  at  a  distance  from  it  have  no  other 
means,  than  their  vascular  communication  affords,  of  participating  in  the  re- 
sults of  its  operations  ;  and  it  is  moreover  necessary  that  they  should  be 
continually  furnished  with  the  organizable  materials,  of  which  the  occasional 
operation  of  the  digestive  process  would  otherwise  afford  only  an  intermitting 
supply.  This  is  especially  the  case,  as  already  mentioned,  with  the  Nervous 
system,  which  is  so  predominant  a  feature  in  the  constitution  of  Man ;  and 
we  accordingly  find  both  objects  provided  for,  in  the  formation  of  a  large 
quantity  of  a  semi-organized  product,  which  contains  within  itself" the  mate- 
rials of  all  the  tissues,  and  is  constantly  being  carried  into  relation  with  them. 
Blood  has  been  not  unaptly  termed  chair  coulante,  or  liquid  flesh ;  and  al- 
though it  has  been  heretofore  much  questioned,  whether  it  could  be  regarded 
as  either  organized  or  endowed  with  vital  properties,  there  now  appears  to  be 
sufficient  reason  for  admitting,  that  this  is  the  case  to  a  very  considerable 
extent.  The  propulsion  of  the  blood  through  the  large  trunks,  which  subse- 
quently divide  into  capillary  vessels,  is  due  to  the  contractions  of  a  hollow  mus- 
cular organ,  the  Heart;  but  these,  like  the  peristaltic  movements  of  the  ali- 
mentary canal,  are  quite  independent  of  (though  frequently  influenced  by)  the 


228  GENERAL  VIEW  OF  THE  FUNCTIONS. 

agency  of  the  Nervous  system ;  and  are  therefore  to  be  referred  to  the  class 
of  Organic  movements,  such  as  occur  in  Vegetables. 

273.  Upon  the  circulation  of  the  blood  through  all  parts  of  the  fabric,  de- 
pends, in  the  first  place,  the  Nutrition  of  the  tissues.     Upon  this  subject,  for- 
merly involved  in  the  greatest  obscurity,  much  light  has  recently  been  thrown 
by  Microscopic   discovery  ;  it  being  now  understood   (as  explained  in  the 
preceding  Chapter),  that  the  continued  growth  and  renewal  of  each  tissue  are 
effected  by  a  continuation  of  a  process  of  cell-growth,  similar  to  that  by  which 
it  was  first  developed.     Even  where  the  primary  cells  have  changed   their 
character,  their  nuclei  remain  persistent;  and  may  be  regarded   (in  the  lan- 
guage of  Mr.  J.  Goodsir)  as  so  many  "germinal  centres,"  for  giving  origin  to 
new  products.     The  greatest  difficulty,  in  the  present  condition  of  our  know- 
ledge of  this  most  interesting  subject,  is  to  comprehend  the  reason  why  such  a 
variety  of  products  should  spring  up  ;  when  the  cells  in  which  they  all  origi- 
nate, appear  to  be  so  exactly  alike.     The  important  discoveries  now  referred 
to  are  not  confined  to  healthy  structures ;  for  it  has  been  ascertained,  that  dis- 
eased growths  have  a  similar  origin  and  mode  of  extension  ;  and  that  the  ma- 
lignant character,  assigned  to  Cancer,  Fungus  Haematodes,  and  other  such 
productions,  is  to  be  traced  to  the  fact,  that  they  are  composed  of  cells  which 
undergo  little  metamorphosis,  and  retain  their  reproductive  power  ;  so  that 
from  a  single  cell,  as  from  that  of  a  Vegetable  Fungus,  a  large  structure  may 
rapidly  spring  up,  the  removal  of  which  is  by  no  means  attended  with  any 
certainty  that  it  will  not  speedily  re-appear,  from  some  germs  left  in  the  sys- 
tem. 

274.  The  independent  character  of  the  cells  in  which  all  organized  tissues 
originate,  might  be  of  itself  a  satisfactory  proof  that,  in  Animals,  as  in  Plants, 
the  actions  of  Nutrition  are  performed  by  the  powers  with  which  they  are 
individually  endowed  ;  and  that,  whatever  influence  the  Nervous  system  may 
have  upon  them,  they  are  not  in  any  way  essentially  dependent  upon  it.  More- 
over, there  is  an  evident  improbability  in  the  idea,  "  that  any  one  of  the  solid 
textures  of  the  living  body  should  have  for  its  office,  to  give  to  any  other  the 
power  of  taking  on  any  vital  actions  :"  and  the  improbability  becomes  an  im- 
possibility, when  the  fact  is  made  known,  that  no  formation  of  nervous  matter 
takes  place  in  the   embryonic  structure,  until  the  processes  of  Organic  life 
have  been  for  some  time  in  active  operation.     The  influence  which  the  Nerv- 
ous System  is  known  to  have  upon  the  Function  of  Nutrition,  is  probably  ex- 
erted, rather  through  the  medium  of  its  power  of  regulating  the  diameter  of  the 
arteries  and  capillaries,  by  which  it  controls  in  some  degree  the  afflux  of  blood, 
and  of  affecting  those  preliminary  actions  on  which  the  quantity  and  quality  of 
the  nutritious  fluid  depend  ;  than  in  any  more  direct  manner.     At  any  rate, 
it  may  be  safely  asserted,  that  no  such  proof  of  its  more  direct  influence,  as 
is  required  to  counterbalance  the  manifest  improbability  which  has  been  shown 
to   attend  it,  has  yet  been  given ; — all  the  facts  which  have  been  adduced  in 
support  of  this  hypothesis  being  equally  explicable  on  the  other,  which,  being 
in  itself  more  probable,  ought  to  be  preferred. 

275.  The  renewal  which  the  various   tissues  of  the  body  are  continually 
undergoing,  has  for  its  chief  object  the  counteraction  of  the  decay  into  which 
they  would  otherwise  speedily  pass;  and  it  is  obviously  required, that  a  means 
should  be   provided  for  conveying  away  the  waste,  as  well  as  for  supplying 
the  new  material.     This  is  partly  effected  by  the  Venous  circulation ;  which 
takes  up  a  large  part  of  the  products  of  incipient  decomposition,  and  conveys 
them  to  organs  of  Excretion,  by  which  they  may  be  separated  and  cast  forth 
from  the  body.     The  first  product  of  the  decay  of  all  organized  structures, 
is   carbonic  acid ;  and  this  is  the  one  which  is  most  constantly  and  rapidly 
accumulating  in  the  system,  and  the  retention  of  which,  therefore,  within  the 


FUNCTIONS  OF  ORGANIC  OR  VEGETATIVE  LIFE.  229 

body,  is  the  most  injurious.  Accordingly,  we  find  two  large  organs — the 
Lungs  and  the  Liver — adapted  to  remove  it ;  and  to  both  these  Venous  blood 
passes,  before  it  is  again  sent  through  the  system.  The  function  of  the  Lungs 
is  so  important  in  warm-blooded  animals,  that  a  special  heart  is  provided  for 
propelling  the  blood  through  them ;  in  addition  to  the  one  possessed  by  most 
of  the  lower  animals,  the  function  of  which  is  the  propulsion  of  the  blood 
through  the  system.  In  these  organs,  the  blood  is  subjected  to  the  influence 
of  the  atmosphere,  by  which  the  carbonic  acid  with  which  it  was  charged,  is 
removed  and  replaced  by  oxygen ;  and  this  change  takes  place,  through  the 
delicate  membrane  that  lines  the  air-cells  of  the  lungs,  according  to  the  physi- 
cal law  of  the  mutual  diffusion  of  gases.  The  introduction  of  oxygen  into 
the  blood  is  necessary  for  the  maintenance  of  those  peculiar  vivifying  powers, 
by  which  the  Nervous  and  Muscular  systems  are  kept  in  a  state  fit  for  activity  ; 
and  its  union  with  their  elements  appears  to  be  a  necessary  condition  of  the 
manifestation  of  their  peculiar  powers.  Of  this  union,  carbonic  acid  is  one 
of  the  chief  products ;  and  we  shall  find  that  the  demand  for  oxygen,  and  the 
excretion  of  carbonic  acid,  vary  according  to  the  amount  of  nervous  and  mus- 
cular action.  The  continual  formation  of  carbonic  acid,  in  this  and  other  in- 
terstitial changes,  appears  to  have  a  most  important  purpose  in  the  vital  eco- 
nomy,— that  of  keeping  up  its  temperature  to  a  fixed  standard;  for  the  union 
of  carbon  and  oxygen  in  this  situation  may  be  compared  to  a  process  of  slow 
combustion  ;  and  it  is  well  known  that,  the  more  energetic  this  is,  the  higher 
is  the  temperature.  Thus,  in  Birds,  whose  muscular  and  nervous  activity  is 
so  great,  and  whose  respiration  is  so  energetic,  the  temperature  is  constantly 
maintained  at  a  point  higher  than  that  which  other  animals  ever  attain,  in  the 
healthy  state  at  least ;  whilst  in  Reptiles,  which  present  a  condition  exactly 
the  reverse  of  this,  the  temperature  is  scarcely  above  that  of  the  surrounding 
medium. — The  function  of  the  Liver  is,  like  that  of  the  lungs,  twofold ;  it 
separates  from  the  blood  a  large  quantity  of  the  superfluous  hydro-carbon, 
which  it  acquires  by  circulating  through  the  tissues ;  and  it  combines  that 
carbon  with  other  elements,  into  a  secretion,  which,  as  we  have  seen,  is  of 
great  importance  in  the  digestive  process.  The  hepatic  circulation,  however, 
is  not  kept  up  by  a  distinct  impelling  organ ;  but  the  venous  blood  from  the 
abdominal  viscera  (and,  in  the  lower  Vertebrata,  that  from  the  posterior  part 
of  the  body)  passes  through  the  Liver  on  its  return  to  the  heart. 

276.  All  animal   substances  have  a  tendency,  during  their  decomposition, 
to  throw  off  nitrogen,  as  well  as  carbon  ;  and  this  nitrogen  may  take  the  form 
either  of  cyanogen,  by  going  off  in  combination  with  carbon,  or   of  ammo- 
nia, by  uniting  at  the  time  of  its  liberation  with  hydrogen.    The  chief  function 
of  the  Kidneys  is  evidently  to  separate  the  azotized  products  of  decay  from 
the  circulating  fluid  ;  for  the  secretion  which  is  characteristic  of  them, — namely 
urea, — contains   a  larger  proportion  of  nitrogen  than  is  found  in  any  other 
organic  compound ;  it  is  identical  in  its  chemical  nature  with  cyanate  of  am- 
monia, and  maybe  considered  as  the  result  of  the  union  of  these  two  products 
of  animal  decomposition.     The  action  of  the  kidneys  is  equally  essential  to 
the  continued  performance  of  the  other  vital  functions,  with  that  of  the  lungs 
and  liver ;  since  death  invariably  follows  its  suspension,  unless  some  other 
means  be  provided  by  Nature  (as  occasionally  happens),  for  the  separation  of 
its  characteristic  excretion  from  the  circulating  blood. 

277.  There  seems  reason  to  believe,  however,  that,  of  the  products  of 
decomposition  which  are  set  free  in  the   various  tissues   and  organs  of  the 
body,  only  a  part  is   destined  to  be  immediately  excreted ;   and  that  it  is  this 
part,  which  is  taken  up  by  the  Veins,  and  conveyed,  by  the  general  vascular 
apparatus,  to  the  several  glands  which  are  to  separate  it.     The   remainder, 
consisting  of  substances  which  are  fit  to  be  re-assimilated,  appears  to  be 

20 


230  GENERAL  VIEW  OF  THE  FUNCTIONS. 

taken  up  by  a  distinct  system  of  vessels,  termed  Lymphatics;  which  may  be 
considered  as  an  extension  of  the  Lacteal  system  through  the  fabric  at  large. 
There  is  good  reason  to  believe,  that  the  special  function  of  the  Lymphatics 
is,  like  that  of  the  Lacteals,  to  minister  to  Nutritive  absorption  (although 
other  substances  may  find  their  way  into  them,  by  the  mere  physical  process 
of  imbibition);  the  latter  being  especially  destined  to  take  up  assimilable 
matter  from  the  digestive  cavity,  whilst  the  former  absorb  the  products  of  the 
secondary  digestion,  which  seems  to  be  continually  going  on  in  every  part  of 
the  body.  (See  Chap.  XL,  Sects.  1  and  2.)  Of  these,  however,  a  portion 
may  still  be  destined  to  immediate  excretion. 

278.  The  various  Secretions  which  have  not  already  been  adverted  to, 
appear  for  the  most  part  to  have  for  their  object  the  performance  of  some 
special  function  in  the  system,  rather  than  the  conveyance  out  of  it  of  any 
substances  which  it  would  be  injurious  to  retain.  This  is  the  case,  for 
example,  in  regard  to  the  secretion  of  the  Lachrymal,  Salivary,  and  Mam- 
mary Glands,  as  well  as  with  that  of  the  Mucous  and  Serous  Membranes. 
The  Excretion  of  fluid  from  the  cutaneous  surface,  however,  appears  to 
answer  two  important  purposes, — the  removal  from  the  body  of  a  portion  of 
its  superfluous  fluid, — and  the  regulation  of  its  temperature.  Just  as,  by  the 
action  of  the  Lungs,  the  conditions  are  supplied,  by  which  the  temperature  of 
the  body  is  kept  up  to  a  certain  standard,  so,  by  that  of  the  Skin,  it  is  pre- 
vented from  rising  too  high ;  for  by  the  continual  excretion  from  its  surface, 
of  fluid  which  has  to  be  carried  off  by  evaporation,  a  degree  of  cold  is  gene- 
rated, which  keeps  the  calorific  processes  in  check;  and  this  excretion  is 
augmented,  in  proportion  to  the  elevation  of  the  external  temperature,  which 
seems,  in  fact,  the  direct  stimulus  to  the  process. — In  all  forms  of  true  Secre- 
tion, the  selection  of  the  materials  to  be  separated  from  the  blood,  is  accom- 
plished, like  selective  Absorption,  by  the  agency  of  cells.  These  are  de- 
veloped in  the  interior  of  the  secreting  organ ;  and  when  they  are  distended 
with  the  fluid  they  have  imbibed,  their  term  of  life  appears  to  have  expired, 
so  that  they  burst  or  liquefy,  yielding  their  contents  to  the  ducts,  by  which 
the  secreted  product  is  conveyed  away.  In  the  case  of  Adipose  tissue,  we 
have  an  instance  in  which  the  secreted  product  (separated  from  the  blood  by 
the  cells  of  which  this  tissue  essentially  consists)  is  not  carried  out  of  the 
body,  but  remains  to  form  a  constituent  part  of  it.— The  regulation  of  the 
amount  of  fluid  in  the  vessels,  is  provided  in  a  kind  of  safety-valve  structure, 
which  has  been  lately  shown  to  exist  in  the  Kidneys.  This  readily  permits 
the  escape  of  aqueous  fluid  from  the  capillary  vessels,  into  the  urinary  canals, 
by  a  process  altogether  distinct  from  the  secretion  of  the  solid  matter,  which 
it  is  the  office  of  the  kidneys  to  separate  from  the  circulating  fluid.  Hence, 
if  the  excretion  of  fluid  from  the  skin  be  checked  by  cold,  so  that  an  accumu- 
lation would  take  place  in  the  vessels,  the  increased  pressure  within  them 
causes  an  increased  escape  of  water  through  the  kidneys.  The  relation 
between  the  true  process  of  Secretion,  which  is  performed  by  the  selective 
power  of  cells,  and  that  of  simple  Transudation,  is  the  same  as  that  which 
has  been  already  pointed  out,  between  Selective  Absorption  and  simple 
Imbibition  (§  271). 

279.  There  is  no  sufficient  reason  to  believe,  that  the  Nervous  System  has 
any  more  direct  influence  on  the  process  of  Secretion,  than  it  has  been  stated 
to  have  on  that  of  Nutrition.  That  almost  every  secretion  in  the  body  is 
affected  by  states  of  mind,  which  must  operate  through  the  nerves,  daily 
experience  teaches ;  but  the  very  remarkable  degree  of  control,  which  the 
Nervous  system'  possesses  over  the  Circulation,  appears  sufficient  to  explain 
any  of  these  effects,  whether  they  be  local  or  general.  The  flow  of  the 
secreted  fluids  through  their  efferent  ducts,  seems  to  be  principally  caused  by 


FUNCTIONS  OF  ORGANIC  OR  VEGETATIVE  LIFE.  231 

the  proper  contractility  of  these,  which  (like  that  of  the  heart  and  alimentary 
canal)  is  directly  stimulated  by  the  contact  of  their  contents;  but  there  is 
also  evidence  that  this  contractility  may  be  affected  (as  it  is  in  those  two 
instances)  by  the  nervous  system;  and  thus  we  have  an  additional  means  of 
influence,  by  which  the  nervous  system  can  operate  on  these  processes,  since 
its  power  is  probably  not  confined  to  the  large  ducts,  but  extends  to  their 
ultimate  ramifications.  Where,  as  happens  in  the  case  of  the  urinary  excre- 
tion, there  is  a  reservoir  into  which  it  is  received  as  fast  as  it  is  formed,  for 
the  purpose  of  preventing  the  inconvenience  which  its  constant  passage  from 
the  body  would  otherwise  occasion, — the  power  of  emptying  this  reservoir  is 
usually  placed  in  some  degree  under  the  dominion  of  the  will,  although 
chiefly  governed  by  reflex  action.  It  is  obvious  that  such  a  provision  is  by 
no  means  essential  to  the  function ;  and  that  it  has  for  its  object  the  adapta- 
tion, merely,  of  that  function,  to  the  conditions  of  Animal  existence. 

280.  Thus  we  see  that,  when  we  enter,  as  it  were,  into  the  penetralia  of 
the  Animal  system,  and  study  those  processes,  of  which  the  development  and 
maintenance  of  the  material  fabric  essentially  consist,  we  find  them  performed 
under  conditions  essentially  the  same  as  those  which  obtain  in  Plants;  and 
we  observe  that  the  operations   of  the   Nervous  System  have  none  but  an 
indirect  influence  or  control  over  them.     It  is,  therefore,  quite  philosophical 
to  distinguish  these  Organic   Functions,  or  phenomena  of  Vegetative   Life, 
from  those  concerned  in  the  Life  of  Relation,  or  Animal  Life.     The  distinc- 
tion is,  indeed,  of  great  practical  importance,  and  lies  at  the  foundation  of  all 
Physiological  Science ;  yet  it  is  seldom  accurately  made,  and  a  very  confused 
notion  on  the  subject  is  generally  prevalent.     It  is  commonly  said,  for  ex- 
ample, that  the  function  of  Respiration  is  the  connecting  link  between  the 
two: — the  fact  being,  however,  that  the  true  process  of  Respiration  is  no 
more  a  function  of  Animal  life,  tha'n  is  any  ordinary  process  of  secretion ;  but 
that,  in  order  to  secure  the  constant  interchange  of  air,  which  is  necessary  to 
its  performance,  the  assistance  of  the  nervous  and  muscular  systems  is  called 
in,  though  not  in  a  manner  which  necessarily  involves  either  consciousness 
or  will. 

281.  The  process  of  Reproduction,  like  that  of  Nutrition,  has  been  until 
recently  involved  in  great  obscurity  ;  and  although  it  cannot  be  said  to  be  yet 
fully  elucidated,  it  has  been  brought,  by  late  investigations,  far  more  within 
our  comprehension,  than  was  formerly  deemed  possible.     The  close  connec- 
tion between  the  Reproductive  and  Nutritive  operations,  both  as  regards  their 
respective  characters,  and  their  dependence  upon  one  another,  has  long  been 
recognized;  and  it  is  now  rendered  still  more  evident.    Nutrition  has  not  been 
unaptly  designated  "  a  perpetual  reproduction  ;"  and  the  expression  is  strictly 
correct.     In  the  fully-formed  organism,  the  supply  of  alimentary  material  to 
every  part  of  the  fabric,  enables  it  to  produce  a  tissue  resembling  itself;  thus 
we  only  find  true  bone  produced  in  continuity  with  bone,  nerve  with  nerve, 
muscle  with  muscle,  and  so  on.     Hence  it  would  appear  that,  when  a  group 
of  cells  has  once  taken  on  a  particular  kind  of  development,  it  continues  to 
reproduce  itself  on  the  same  plan.     But  in  the  Reproductive  process  it  is 
different.     A  single  cell  is  generated  by  certain   preliminary  actions, — from 
which  single  cell,  all  those  which  subsequently  compose  the  embryonic  struc- 
tures, take  their  origin ;  and  it  is  not  until  a  later  period,  that  any  distinction 
of  parts  can  be  traced,  in  the  mass  of  vesicles  which  spring  from  it.     Hence 
the  essential  character  of  the  process  of  Reproduction  consists  in  the  forma- 
tion of  a  cell,  which  can  give  origin  to  others,  from  which  again  others  spring ; 
— and  in  the  capability  of  these  last  to  undergo  several  kinds  of  transforma- 
tion, so  as  ultimately  to   produce  a  fabric,  in  which  the  number  of  different 
parts  is  equal  to  that  of  the  functions  to  be  performed,  every  separate  part 


232  GENERAL  VIEW  OF  THE  FUNCTIONS. 

having  a  purpose  distinct  from  that  of  the  rest.  Such  a  fabric  is  considered 
as  a  very  heterogeneous  one  ;  and  is  eminently  distinguished  from  those  homo- 
geneous organisms,  in  which  every  part  is  but  a  repetition  of  the  rest.  Of  all 
Animals,  Man  possesses,  as  already  shown,  the  greatest  variety  of  endow- 
ments,— the  greatest  number  of  distinct  organs ;  and  yet  Man,  in  common  with 
the  simplest  Animal  or  Plant,  takes  his  origin  in  a  single  cell.  It  is  in  the 
almost  homogeneous  fabrics  of  the  Cellular  Plants,  that  we  find  the  closest 
connection  between  the  function  of  Nutrition,  and  that  of  Reproduction;  for 
every  one  of  the  vesicles  which  compose  their  fabric,  is  endowed  with  the 
power  of  generating  others  similar  to  itself;  and  these  may  either  extend  the 
parent  structure,  or  separate  into  new  and  distinct  organisms.  Hence  it  is 
scarcely  possible  to  draw  a  line,  in  these  cases,  between  the  Nutrition  of  the 
individual,  and  the  Reproduction  of  the  species. 

282.  But,  it  will  be  inquired,  how  and  where  in  the  Human  body  (and  in 
the  higher  Animals  in  general)  is  this  embryonic  vesicle  produced,  and  what 
are  the  relative  offices  of  the  two  sexes  in  its  formation  ?  This  is  a  question 
which  must  still  be  answered  with  some  degree  of  doubt ;  and  yet  observed 
phenomena,  if  explained  by  the  aid  of  analogy,  seem  to  lead  to  a  very  direct 
conclusion.  The  embryonic  vesicle  itself,  like  other  cells,  must  arise  from  a 
germ  ;  and  reasons  will  be  hereafter  given  for  the  belief,  that  the  germ  is  sup- 
plied by  the  male  parent,  and  that  the  female  supplies  only  the  materials  for 
its  development.  Here,  as  in  the  Nutritive  processes,  we  find  that  the  opera- 
tions immediately  concerned  in  this  function, — namely,  the  act  of  fecundation, 
and  the  development  of  the  ovum, — are  not  directly  influenced  in  any  way  by 
the  nervous  system ;  and  that  the  functions  of  Animal  Life  are  called  into  play, 
only  in  the  preliminary  and  concluding  steps  of  the  process.  In  many  of  the 
lower  Animals,  there  is  no.  sexual  congress,  even  where  the  concurrence  of 
two  sets  of  organs  (as  in  the  Phanerogamic  Plants)  is  necessary  for  the  pro- 
cess; the  ova  are  liberated  by  one,  and  the  spermatozoa  by  the  other;  and 
the  accidental  meeting  of  the  two  produces  the  desired  result.  In  many  Ani- 
mals higher  in  the  scale,  the  impulse  which  brings  the  sexes  together  is  of  a 
purely  instinctive  kind.  But  in  Man,  it  is  of  a  very  compound  nature.  The 
instinctive  propensity,  unless  unduly  strong,  is  controlled  and  guided  by  the 
will,  and  serves  (like  the  feelings  of  hunger  and  thirst)  as  a  stimulus  to  the 
reasoning  processes,  by  which  the  means  of  gratifying  it  are  obtained;  and  a 
moral  sentiment  or  affection  of  a  much  higher  kind  is  closely  connected  with 
it,  which  acts  as  an  additional  incitement.  Those  movements,  however, 
which  are  most  closely  connected  with  the  essential  part  of  the  process,  are, 
like  those  of  deglutition,  respiration,  &c.,  simply  reflex  and  involuntary  in  their 
character;  and  thus  we  have  another  proof  of  the  constancy  of  the  principle, 
that,  where  the  action  of  the  apparatus  of  Animal  Life  is  brought  into  near 
connection  with  the  Organic  functions,  it  is  not  such  as  requires  the  operation 
of  the  purely  animal  powers, — sensation  and  volition.  Thus,  then,  as  it  has 
been  lucidly  remarked,  "the  Nervous  System  lives  and  grows  within  an  Ani- 
mal, as  a  parasitic  Plant  does  in  a  Vegetable  ;  with  its  life  and  growth,  certain 
sensations  and  mental  acts,  varying  in  the  different  classes  of  Animals,  are 
connected  by  nature  in  a  manner  altogether  inscrutable  to  man ;  but  the  ob- 
jects of  the  existence  of  Animals  require,  that  these  mental  acts  should  exert 
a  powerful  controlling  influence  over  all  the  textures  and  organs  of  which  they 
are  composed." 

3.  Functions  of  Animal  Life. 

283.  The  existence  of  consciousness,  by  which  the  individual  (le  moi,  in 
the  language  of  French  physiologists)  becomes  sensible  of  impressions  made 


FUNCTIONS  OF  ANIMAL  LIFE.  233 

upon  its  bodily  structure, — and  the  power  of  spontaneously  exciting  contrac- 
tions in  its  tissues,  by  which  evident  motions  are  produced, — have  been  already 
stated  to  be  the  peculiar  attributes  of  the  beings  composing  the  Animal  king- 
dom. The  evident  motions  exhibited  by  some  Plants,  cannot  be  regarded  as 
indicating  the  existence  of  any  psychical  endowments  in  the  beings  included 
in  the  Vegetable  kingdom ;  for  they  are  usually  to  be  referred  without  difficulty 
to  the  action,  either  direct  or  indirect,  of  an  external  stimulus,  upon  a  contrac- 
tile tissue  ;  and  even  where  no  such  action  evidently  takes  place,  there  is  good 
reason  to  suppose  its  existence.  To  refer,  therefore,  the  movements  of  Vege- 
tables to  a  Nervous  system,  of  which  no  traces  can  be  found, — still  more  to 
suppose  them  endowed  with  consciousness  and  will,  as  some  have  done, — is 
to  violate  most  grossly  a  well-known  rule  in  philosophy,  which  cannot  be  too 
steadily  kept  in  view  in  prosecuting  physiological  inquiries — non  finger e  hy- 
potheses. 

284.  There  are  in  Animals,  however,  many  movements  which  are  equally 
dependent  upon  direct  stimuli  for  their  production ;  such  are  (as  we  have 
seen),  even  in  the  highest,  the  actions  of  the  heart  and  of  the  alimentary  canal. 
These,  in  the  lowest  tribes,  probably  bear  a  much  greater  proportion  to  the 
whole  amount  of  those  exhibited  by  the  beings,  than  they  do  in  the  higher; 
whilst  those,  which  we  may  regard  as  specially  dependent  on  a  nervous  sys- 
tem, appear  to  constitute  but  a  small  part  of  their  general  vital  actions.     The 
life  of  such  beings,  therefore,  bears  a  much  closer  resemblance  to  that  of  the 
Vegetable,  than  to  that  of  the  higher-Animal.     Their  organic  functions  are 
performed  with  scarcely  more  of  sensible  movement,  than  is  seen  in  plants ; 
and  of  the  motions  which  they  do  exhibit  (nearly  all  of  them  immediately 
concerned  in  the  maintenance  of  the  organic  functions),  it  is  probable  that 
many  are  the  result  of  the  simple  contractility  of  their  tissues,  called  into 
action  by  the  stimuli  directly  applied  to  them.    It  is  scarcely  possible  to  ima- 
gine that  such  beings  can  enjoy  any  of  those  higher  mental  powers,  which 
Man  recognizes  by  observation  on  himself,  and  of  which  he  discerns  the  ma- 
nifestations in  those  tribes,  which,  from  their  nearer  relation  to  himself,  he 
regards  as  more  elevated  in  the  scale  of  existence. — If  we  direct  our  attention 
on  the  other  hand,  to  the  psychical*  operations  of  Man,  as  forming  part  of 
his  general  vital  actions,  we  perceive  that  the  proportion  is  completely  re- 
versed.    So  far  from  his  organic  life  exhibiting  a  predominance,  it  appears 
entirely  subordinate  to  his  animal  functions,  and  seems  destined  only  to  afford 
the  conditions  for  their  performance.     If  we  could  imagine  his  nervous  and 
muscular  systems  to  be  isolated  from  the  remainder  of  his  corporeal  structure, 
and  endowed  in  themselves  with  the  power  of  retaining  their  integrity  and 
activity,  we  should  have  all  that  is  essential  to  our  idea  of  Man.     But,  as  at 
present  constituted,  these  organs  are  dependent,  for  the  maintenance  of  their 
integrity  and  functional  activity,  upon  the  nutritive  apparatus ;  and  the  whole 
object  of  the  latter  appears  to  be  the  supply  of  those  conditions,  which  are 
necessary  to  the  exercise  of  the  peculiarly  animal  functions.     That  his  men- 
tal activity  should  be  thus  made  dependent  upon  the  due  supply  of  his  bodily 
wants,  is  a  part  of  the  general  scheme  of  his  probationary  existence  ;  and  the 
first  excitement  of  his  intellectual  powers  is  in  a  great  degree  dependent  upon 
this  arrangement. 

285.  The  most  simple  or  elementary  function  of  the  Nervous  System  is,  as 
already  observed,  the  establishment  of  a  communication  between  a  part  which 
is  susceptible  of  impressions,  and  another  which  can  perform  contractile  move- 

*  Here  and  elsewhere  this  term  will  be  employed  in  its  most  extended  sense,  to  designate 
all  the  mental  operations, — whether  intellectual,  emotional  or  instinctive, — of  which  Man's 
nervous  system  is  the  instrument. 

20* 


234  GENERAL  VIEW  OF  THE  FUNCTIONS. 

ments  ;  so  that  a  stimulus  applied  to  one  may  immediately  excite  a  respondent 
action  in  the  other,  however  great  may  be  its  distance.  Hence  it  may  be  said 
to  have  an  internuncial  function ;  but  this,  so  far  as  it  is  performed  without 
the  necessary  participation  of  the  consciousness  or  will  of  the  individual,  is 
not  essentially  higher  in  character,  than  the  corresponding  function  in  Plants, 
although  the  latter  is  affected  by  a  different  apparatus.  The  ministration  of 
the  nervous  system  to  purely  Animal  life,  obviously  consists  in  its  rendering 
the  mind  cognizant  of  that  which  is  taking  place  around,  and  in  enabling  it  to 
act  upon  the  material  world,  by  the  instruments  with  which  the  body  is  pro- 
vided for  the  purpose.  It  is  important  to  observe,  that  every  method  at  pre- 
sent known,  by  which  Mind  can  act  upon  Mind,  requires  muscular  contraction 
as  its  medium,  and  sensation  as  its  recipient.  This  is  the  case,  for  example, 
not  only  in  that  communication  which  takes  place  by  language,  whether 
written  or  spoken ;  but  in  the  look,  the  touch,  the  gesture,  which  are  so  fre- 
quently more  expressive  than  any  words  can  be ;  and  thus  we  trace  the  limi- 
tation, which,  even  in  communication  that  appears  so  far  removed  from  the 
material  world,  constantly  bounds  the  operations  of  the  most  powerful  intel- 
lect, and  the  highest  flights  of  the  imagination.  That  in  a  future  state  of  being', 
the  communion  of  mind  with  mind  will  be  more  intimate,  and  that  Man  will 
be  admitted  into  more  immediate  converse  with  his  Maker,  appears  to  be  alike 
the  teaching  of  the  most  comprehensive  Philosophical  inquiries,  and  of  the 
most  direct  Revelation  of  the  Divinity. 

286.  The  Organs  of  Sense  are  instruments,  which  are  adapted  to  enable 
particular  nerves  to  receive  impressions  from  without;  of  a  kind,  and  in  a  de- 
gree, of  which  they  would  not  otherwise  be  sensible.  Thus,  although  the 
simple  contact  of  a  hard  body  with  the  nerve  may  be  readily  conceived  to 
produce  a  material  change  in  it,  of  such  a  kind  as  would  be  easily  propagated 
to  the  central  sensorium,  it  is  evident  that  a  nerve  must  be  peculiarly  modi- 
fied, to  receive  and  conduct  sonorous  impressions  from  the  undulations  of  the 
air ;  still  more — to  be  susceptible  of  the  impressions  produced  by  those  un- 
dulations, to  which  most  Natural  Philosophers  now  attribute  the  transmission 
of  light.  And,  even  when  this  difficulty  has  been  provided  for,  by  some  mo- 
dification in  the  structure  of  the  nerve  itself,  there  is  evidently  another  still 
remaining, — that  of  understanding  how  distinct  images  of  the  form,  colour, 
&c.,  of  external  objects  can  be  communicated  to  the  nerve  of  sight;  or  ideas 
of  the  direction,  pitch,  quality,  &c.,  of  sonorous  undulations,  can  be  obtained 
through  the  auditory  nerve.  There  is  reason  to  believe  that  many  among 
the  lower  Animals,  which  do  not  see  objects  around  them,  are  conscious  of 
the  influence  of  light ;  and  thus  the  distinction  between  the  mere  reception  of 
the  impression,  and  the  communication  of  the  optical  image,  becomes  evident. 
The  former  may  take  place  through  the  intervention  of  nerves,  whose  sensory 
extremities  offer  no  peculiarities :  the  latter  can  only  be  received  through  the 
medium  of  an  instrument,  which  shall,  from  the  mixture  of  rays  falling 
equally  upon  every  part  of  a  surface,  produce  an  optical  image,  and  then 
impress  it  upon  the  expanded  surface  of  the  nerve ;  so  that  each  fibril  may 
receive  a  distinct  impression,  the  image  presented  to  the  mind  being  formed 
by  the  combination  of  the  whole.  That  this  is,  in  fact,  the  share  which  the 
organs  of  special  sense  bear  in  the  general  endowments  of  the  whole  appa- 
ratus, may  be  inferred  especially  from  the  conformation  of  the  Eye ;  which 
is  in  every  respect  a  merely  optical  instrument,  of  the  greatest  beauty  and 
perfection,  adapted  to  present  to  the  nerve,  in  the  most  advantageous  manner, 
the  images  of  surrounding  objects  in  all  their  variations.  And  we  might  con- 
ceive that,  if  it  were  possible  for  the  interior  of  the  living  eye  to  be  replaced 
by  one  constructed  of  inorganic  materials  by  the  hand  of  man,  without  de- 
stroying the  functional  power  of  the  retina,  the  sense  of  sight  would  be  but 


FUNCTIONS  OF  ANIMAL  LIFE.  235 

little  impaired, — except  through  the  incapability,  on  the  part  of  any  piece  of 
human  mechanism,  to  imitate  those  wondrous  contrivances  of  Infinite  Skill, 
which  have  for  their  object  the  adaptation  of  the  instrument  to  varieties  of  dis- 
tance, of  intensity  of  light,  &c.  There  can  be  little  doubt,  that  the  structure 
of  the  Ear  is  arranged  to  do  the  same  for  the  sonorous  vibrations,  which  the 
eye  does  for  the  rays  of  light;  that  is,  through  its  means,  the  undulations 
which  strike  upon  the  external  surface  of  the  organ  are  separated  and  distin- 
gished,  those  of  a  like  kind  being  brought  together  upon  one  division  of  the 
nerve,  and  those  of  another  order  upon  a  different  set  of  fibres  ;  so  that  the 
different  kinds  of  sound,  and  the  peculiar  quality  and  direction  of  each,  may 
be  discriminated ;  whilst,  by  the  concentration  of  all  the  impressions  of  the 
same  character,  a  higher  amount  of  force  is  given  to  them.  Of  the  sense  of 
Smell,  no  similar  account  can  be  given;  since  the  medium  by  which  odours  are 
propagated  is  not  known.  If,  as  is  generally  believed,  this  is  accomplished  by 
the  diffusion  through  space,  of  minute  particles  of  the  odoriferous  body  itself 
(which  supposition  seems  to  derive  support  from  the  general  fact,  that  the 
most  volatile  substances  are  usually  most  odoriferous),  smell  may  be  regarded, 
— as  taste  also  is  probably  to  be  considered, — in  the  light  of  a  refined  kind  of 
touch. 

287.  Thus,  the  general  rule  holds  good,  here  as  elsewhere,  that  the  pro- 
cesses, by  which  the  organism  is  immediately  brought  into  relation  with  the 
external  world,  are  performed  in  obedience  to  physical  laws  ;  the  living  struc- 
ture only  affording  certain  peculiar  conditions,  which  may  be  imitated  in  a 
great  degree  by  other  means.     This  is  the  case,  for  example,  with  regard  to 
Digestion,  which  is  in  itself  a  simply  Chemical  process,  that  will  take  place 
out  of  the  body  as  well  as  in  it,  if  the  materials  and  the  necessary  solvent  be 
submitted  to  the  same  circumstances,  as  those  to  which  they  are  exposed  in 
the  stomach  ;  and  in  regard  also  to  the  act  of  Respiration,  which  depends 
upon  the  physical  tendency  to  mutual  diffusion,  inseparable  from  the  exist- 
ence of  gases  ;  and  we  notice  the  prevalence  of  the  same  general  fact  in  the 
Animal  as  in  the  Organic  functions.     We  cannot  become  cognizant  of  the 
changes,  or  even  of  the  existence,  of  the  external  world,  unless  some  mate- 
rial effect  be  produced  by  it  on  our  organs  of  sense  ;  nor  can  we  produce  any 
alteration  in  its  condition,  except  by  powers  which  act  according  to  purely 
mechanical  principles. 

288.  In  regard  to  the  Muscular  System,  it  has  already  been  sufficiently 
explained  that  it  forms  a  part  of  the  apparatus  of  Animal  life,  no  otherwise 
than  as  the  instrument  by  which  nervous  energy  operates   upon   external 
objects.     The  contractility  which  it  manifests  on  the  application  of  a  stimulus, - 
is  an  endowment  which  it  derives  from  its   own  structure,  and  not  from  the 
nervous  system ;  for  it  will  be  clearly  proved  in  its  appropriate  place,  that 
the  presence  of  this  contractility  is  connected  with  the  healthy  nutrition  of 
the  tissue,  and  with  its  due  supply  of  arterial  blood ;  and  that  the  complete 
separation  of  any  muscular  part  from  all  its  nervous   connections,  has  none 
but  an  indirect  influence  on  its  properties. 


236 


CHAPTER    V. 

FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

1.   General  Summary. 

289.  OUR  fundamental  idea  of  a  Nervous  System  includes  a  central  organ 
or  ganglion,  essentially  composed  of  vesicles  or  cells,  with  a  plexus  of  capil- 
lary vessels  distributed   amongst  these  ;  and  a  set  of  trunks  and  ramifying 
branches,  composed  of  tubular  fibres,  and  connecting  the  ganglion  with  differ- 
ent parts  of  the  fabric.     These  branches  are  for  the  most  part  distributed,  on 
the  one  hand,  to  the  sensory  surfaces  and  organs  ;   and,  on  the  other,  to  the 
muscles  or  motor  organs.     The  former  serve  for  the  conveyance  of  impres- 
sions, made  upon  the  periphery,  towards  the   centre  ;  and  they  may  thence 
be  denominated  afferent  fibres.*     The  latter,  on  the  other  hand,  serve  to  con- 
vey an  influence,  originating  in  the   central  ganglion,  to  the  muscles,  which 
are  thereby  thrown  into  contraction ;  and  these  are  distinguished  as  efferent 
or  motor  fibres.     Although  the  distinctness  of  these  two   sets   of  fibres  has 
only  been  proved  in  the  Vertebrata,  yet  there  can  be  no  reasonable  doubt  of 
its  universality.     Now  this  fundamental  idea  of  a  Nervous  apparatus,  which 
is  based  upon  what  are  believed  to  be  the  relative  offices  of  its  several  com- 
ponent parts  (as  formerly  explained  §  248),  is  found  to  be  exactly  realized  in 
the  simple  forms  of  that  system,  which  we  find  in  the  lowest  animals  in  which 
Nervous  structure  can   be  discovered  at  all ;  and  even  where  the  apparatus 
has,  to  all  appearance,  a  character  of  much  greater  complexity,  it  may  still  be 
reduced  to  the  same  simple  idea,  by  taking  it  to  pieces  (so  to  speak)  and  exa- 
mining its  component  parts.     For  it  will  then  be  found,  that  the  multiplica- 
tion of  ganglia  and  trunks  is   principally  due  to   the  multiplication  of  the 
organs  to  be  supplied ;  as  in  the  case  of  the  nervous  ring  of  the  Star-fish, 
where  the  ganglia, — all  of  them  apparently  identical  in  function,  and  similar  in 
the  distribution  of  their  branches, — are  repeated  in  conformity  with  the  num- 
ber of  the  radiating  parts  of  the  body  ;  or  in  the  case  of  the  ventral  nervous 
cord  of  an  Articulated  animal,  in  which  the  ganglia  are   in  like  manner  re- 
peated longitudinally,  in  accordance  with  the  number  of  segments  of  the  body, 
and  of  the  pairs  of  members  connected  with  them.     In  other  instances,  the 
multiplication  of  ganglia  is  due  to  the  increased  complexity  of  the  functions 
performed  by  a  set  of  organs ;  of  this  we   shall  see  numerous   examples  in 
the  higher  Vertebrata.     In  all  cases,  the  individual  ganglia  remain  to  a  great 
extent  independent  of  each  other;  so  that  the  removal  of  any  one  (if  it  can 
be  accomplished  without  injury  to  the  rest)  affects  only  the  particular  organ 
with  which  it  may  be  connected,  and  the  special  function   of  that  organ  to 
which  alone  it  ministers. 

290.  Before  proceeding  to  inquire  into  the  operations  of  the  Nervous  Sys- 
tem as  a  whole,  it  is  desirable  that  we  should  stop  to  consider  the  conditions 

*  Such  are  commonly  denominated  sensory  fibres ;  but  this  designation  is  objectionable, 
in  as  much  as  many  of  them  serve  to  excite  reflex  actions,  without  necessarily  producing 
sensations. 


DEPENDENCE  OF  NERVOUS  POWER  ON  SUPPLY  OF  BLOOD.        237 

on  which  its  functional  activity  is  dependent. — The  chief  of  these,  is  a  con- 
stant supply  of  oxygenated  blood  ;  which  is  more  necessary  for  the  mainte- 
nance of  the  Nervous  power,  than  it  is  for  that  of  any  other  tissue  whatever. 
This  supply  is  peculiarly  required  at  those  points  at  which  changes  originate  ; 
not  being,  it  would  appear,  so  necessary  for  the  mere  conduction  of  impres- 
sions. Consequently  we  find  that  the  greatest  supply  of  blood  is  afforded  to 
the  nervous  centres,  and  to  the  peripheral  extremities  or  origins  of  the  affe- 
rent nerves ;  and  that  the  effects  of  any  interruption  to  the  supply  are  mani- 
fested in  an  immediate  and  most  striking  manner.  Thus,  if  the  circulation 
through  the  Brain  be  suspended  but  for  an  instant,  insensibility  and  loss  of 
voluntary  power  supervene,  and  continue  until  it  is  restored.  This  was 
shown  by  the  following  experiment  of  Sir  A.  Cooper's.  After  having  tied 
both  carotid  arteries  in  a  dog,  he  compressed  the  Vertebral  trunks ;  and  im- 
mediate insensibility  came  on,  the  animal  at  the  same  time  falling  powerless. 
But  convulsive  movements  occurred  at  the  same  time  ;  showing  that  the  func- 
tions of  the  spinal  cord  were  not  suspended,  but  only  deranged.  As  soon  as 
the  blood  was  re-admitted  to  the  brain,  the  animal  recovered  its  consciousness 
and  voluntary  power,  and  stood  on  its  legs  again ;  the  convulsive  movements 
ceased  at  the  same  time. — In  Syncope,  the  circulation  through  the  Spinal 
cord  is  weakened,  by  the  failure  of  the  heart's  action,  to  the  same  extent  as 
the  flow  of  blood  through  the  Brain ;  and  a  general  cessation,  not  merely  of 
muscular  movement,  but  of  all  power  of  exciting  it,  is  the  immediate  result. 
No  sooner,  however,  is  the  circulation  fully  re-established,  than  the  power  of 
the  Nervous  centres  is  restored. — Again,  the  influence  of  diminished  circula- 
tion, at  the  origins  of  the  afferent  nerves,  is  shown  in  the  deficient  impressi- 
bility of  the  nerves,  at  the  part  affected.  Thus,  if  the  movement  of  blood 
through  the  capillaries  of  a  limb  be  stagnated, — whether  by  pressure  on  the 
arterial  trunks,  by  cold,  or  by  any  other  cause, — it  is  at  once  made  apparent 
by  the  numbness  of  the  surface ;  and  a  complete  stagnation  produces  com- 
plete insensibility.  The  power  of  receiving  impressions,  that  are  to  excite 
reflex  movements,  is  diminished  in  the  same  degree. 

291.  On  the  other  hand  it  is  found,  that  increased  circulation  through  the 
same  parts,  is  attended  with  an  exaltation  of  their  function.     This  is  particu- 
larly noticed  in  those  affections  of  the  brain  and  spinal  cord,  closely  border- 
ing on  inflammation,  to  which  the  terms  active  congestion  and  determination 
of  blood  have  been  applied.     We  have,  in  such  cases,  extreme  acuteness  of 
sensation,  excessive  activity  of  the  mental  functions,  or  violent  excitement  of 
the  motor  powers  ;  according  (it  would  seem)  to  the  particular  division  of  the 
nervous  centres  most  affected.     Again,  we  find  that  an  increase  in  the  circu- 
lation through  any  organ,  from  which  afferent  nerves  arise,  increases  their 
readiness  to  receive  impressions ;  thus  the  sensibility  of  the  genital  organs  of 
animals  during  the  period  of  heat,  and  of  those  of  man  in  a  state  of  venereal 
excitement,  are  greatly  augmented ;  and  the  tendency  of  impressions,  made 
upon  them,  to  excite  reflex  movements,  is  similarly  exalted. 

292.  The  due  activity  of  the  Nervous  System  is  not  merely  dependent 
upon  a  constant  and  ample  supply  of  Blood ;  but  it  requires  that  this  blood 
should  be  in  a  state  of  extreme   purity,  and  more   especially  that  it  should 
contain  a  due  supply  of  oxygen,  and  should  be  depurated  of  its  carbonic  acid, 
and  of  other  products  of  the  decomposition  of  the  body.     The  final  cessa- 
tion of  nervous  power,  in  death  by  Asphyxia,  is  partly  due  (as  will  be  shown 
hereafter,  Chap.  XIIL,  Sect.  3),  to  a  positive  deficiency  in  the  supply  of  blood  ; 
but  the  obtuseness  of  sensibility  which  gradually  increases  until  a  state  of 
unconsciousness  comes  on,  may  be  clearly  traced  in  the  first  instance  to  the 
deficient  aeration  of  the  blood,  which  is  gradually  deprived  of  its  oxygen,  and 
charged  with  more  and  more  carbonic  acid.     Corresponding  but  less  severe 


238  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

symptoms  occur,  when  the  excretion  of  carbonic  acid  is  not  checked,  but  only 
slightly  impeded ;  provided  the  impediment  be  in  operation  for  a  sufficient 
length  of  time,  as. in  the  case  of  an  ill-ventilated  apartment;  an  indisposition 
to  mental  exertion,  a  deficiency  of  muscular  power,  and  an  obtuseness  of  the 
intellectual  and  moral  faculties,  being  the  general  result. — These  facts  are 
readily  explained  upon  the  hypothesis  (which  seems  now  to  have  a  sufficiently 
wide  foundation,  to  be  entitled  to  rank  as  physiological  truth,  although  no 
very  direct  proof  of  it  can  be  given),  that  the  functional  activity  of  the  nerv- 
ous system  is  mainly  dependent  upon  the  combination  of  the  oxygen  sup- 
plied by  the  blood,  with  its  elements',  the  production  of  the  nervous  force, 
whatever  be  its  nature,  being  a  result  of  this  change  of  composition.  The 
chief  grounds  for  this  doctrine  will  now  be  enumerated. 

293.  In  the  first  place,  the  dependence  of  nervous  energy  upon  the  con- 
stant circulation  of  blood  through  the  tissue,  is  much  more  close  and  imme- 
diate than  can  be  accounted  for  on  the  idea  that  the  relation  is  one  of  mere 
nutrition  or  development.     On  the   contrary,  where   these  last  changes  are 
taking  place  most  actively,  we  often  find  rather  a  disposition  to  stagnation  of 
the  current,  to  give  time  for  the  elaboration  of  the  nutrient  materials  that  are 
to  be  withdrawn  from  it;  and  in  no  case  does  the  process  so  instantaneously 
cease,  when  the  flow  is  suspended.     From  this  it  would  appear,  that  some 
combination  takes  place  between  the  elements  of  the  nervous  tissue,  and  some 
material  supplied  by  the  blood ;  which  is  much  more  rapid  in  its  character, 
than  the  process  of  cell-development ;  and  which  is  essentially  concerned  in 
the  production  and  maintenance  of  the  active  condition  of  the  nervous  sys- 
tem.— Again,  that  the  material  supplied  by  the  blood  for  this  purpose  is  Oxy- 
gen, would  appear  from  a  variety  of  considerations.     A  general  survey  of 
the  Animal  kingdom  shows,  that  oxygen  is  essential  to  the  maintenance  of 
animal  life,  as  distinct  from  vegetative;  and  a  more  particular  comparison 
of  different  tribes  demonstrates  most  unequivocally,  that  the  consumption  of 
oxygen  is  in  direct  relation  to  the  development  of  the  animal  powers  in  each. 
These  facts  harmonize  completely  with  what  has  been  just  stated,  respecting 
the  effects  of  a  suspension  of  the  oxygenating  process. 

294.  Further,  in  proof  that  the  activity  of  the  Nervous  system  is  immedi- 
ately dependent,  not  upon   a  process  of  development  or  nutrition,  but  upon 
one  of  disintegration  or  destruction,  it  may  be  urged,  that  it  is  impossible  for 
this  state  of  activity  to  be  maintained,  in  a  large  portion  of  it,  without  an  in- 
terval of  repose,  which  we  know  to  be  favourable  to  the  vegetative  or  repa- 
rative  processes.     There  are  certain  parts  of  the  Nervous  System,  particularly 
those  that  put  in  action  the  respiratory  muscles,  which  are  in  a  state  of  un- 
ceasing though  moderate  activity  ;  and  in  these,  the  constant  nutrition  is  suffi- 
cient to  repair  the   effects  of  the  constant  decay.     But  those  parts  which 
operate  in  a  more  powerful  and  energetic  manner,  and  which  are  therefore 
more  rapidly  disintegrated  when  in  action,  need  a  season  of  rest  for  their  re- 
paration.    Hence  the  sense  of  fatigue  which  is  experienced  when  the  mind 
has  been  long  acting  through  its  instrument, — the  Brain ;  and  the  irresistible 
tendency  to  sleep,  which  usually  supervenes  after  any  unusual  exertion  of  this 
kind.  In  the  healthy  state  of  the  body,  when  the  exercise  of  the  nervous  system 
by  day  does  not  exceed  that  which  the  repose  of  the  night  may  compensate, 
the  Nervous   System  is  maintained  in  a  condition  which  fits  it  for  constant 
moderate  exercise  ;  but  unusual  demands  upon  its  powers,— whether  by  long- 
continued  and  severe  exercise  of  the  intellect,  by  excitement  of  the  emotions, 
or  by  the   combination  of  both,  in  that  state  of  anxiety  which  the  circum- 
stances of  man's  condition  too  frequently  induce, — occasion  an  unusual  waste, 
and  require  a  prolonged  repose  and  uninterrupted  nutrition,  for  the  complete 
restoration  of  its  powers.     There  can  be  no  doubt  that  (from  causes  which 


DISINTEGRATION  OF  NERVOUS  MATTER  WITH  USE.  239 

are  not  known)  the  amount  of  sleep  required  by  different  persons,  for  the 
maintenance  of  a  healthy  condition  of  the  Nervous  System,  varies  consider- 
ably ;  some  being  able  to  dispense  with  it  to  a  degree  which  would  be  exceed- 
ingly injurious  to  other  individuals,  who  do  not  surpass  them  in  mental  activity. 
Where  a  prolonged  exertion  of  the  mind  has  been  made,  and  the  natural  tend- 
ency to  sleep  has  been  habitually  resisted,  by  a  strong  effort  of  the  will, 
injurious  results  are  sure  to  follow.  The  bodily  health  breaks  down;  and  too 
frequently  the  mind  itself  is  permanently  enfeebled.  It  is  obvious  that  the 
Nutrition  of  the  Nervous  System  becomes  completely  deranged  ;  and  that  the 
tissue  is  no  longer  formed  in  a  manner  requisite  for  the  discharge  of  its  healthy 
functions.  The  same  may  be  said  of  the  state  of  Mania  ;  in  which  there  is, 
for  a  time,  an  extraordinary  degree  of  activity  (though  manifested  in  an  irregu- 
lar manner)  of  the  cerebral  functions,  and  an  absence  of  disposition  to  sleep. 
Such  a  state  may  continue  for  some  time;  but  the  subsequent  exhaustion  of 
nervous  power  is  proportioned  to  the  duration  of  the  excitement,  and  frequent 
attacks  of  mania  almost  invariably  subside  at  last  into  imbecility. 

295.  Additional  evidence  for  the  belief  that  the  functional  activity  of  the 
Nervous  tissue  involves  disintegration  of  its  tissue  by  the  agency  of  Oxygen, 
is  found  in  the  increase  of  phosphatic  deposits  in  the  urine, — and  especially 
of  those  having  alkaline  bases, — when  there  has  been  any  unusual  demand 
upon   the   nervous  power.     No   others  of  the  soft  tissues  contain  any  large 
amount  of  phosphorus ;  and  the  marked  increase  in  these  deposits,  which  has 
been  continually  observed  to  accompany  long-continued  wear  of  mind,  whether 
by  intellectual  exertion,  or  by  the  excitement  of  the  feelings, — and  which  fol- 
lows any  temporary  strain  upon  its  powers,  can  scarcely  be  set  down  to  any 
other  cause.     The  most  satisfactory  proof  is  to  be  found  in  cases,  in  which 
there  is  a  periodical  demand  upon  the  mental  powers  ;  as,  for  example,  among 
Clergymen,  in  the  preparation  for  and  discharge  of  their  Sunday  duties.    This 
is  found  to  be  almost  invariably  followed  by  the  appearance  of  a  large  quantity 
of  the  alkaline  phosphates  in  the  urine.     And  in  cases  in  which  constant  and 
severe  intellectual  exertion  has  impaired  the  nutrition  of  the  brain,  and  has 
consequently  weakened  the  mental  power,  it  is  found  that  any  premature  at- 
tempt to  renew  the  activity  of  its  exercise,  causes  the  re-appearance  of  the 
excessive  phosphatic  discharge  indicative  of  an  undue  waste  of  nervous  mat- 
ter.* 

296.  There  is  not  the  same  evidence  of  constant  change,  however,  in  re- 
gard to  the  fibrous  element  of  the  Nervous  System;  and  its  conducting  power 
appears  to  be  much  less  dependent  upon  the  supply  of  blood,  than  is  the  ori- 
ginating power  of  the  vesicular  matter.     It  remains,  with  little  decrease,  for 
some  time   after  death  ;  especially  in  cold-blooded  animals  ;  for  we  can,  by 
pinching,  pricking,  or  otherwise  stimulating  the  motor  trunks,  give  rise  to  con- 
tractions in  the  muscles  supplied  by  them,  exactly  as  during  life.     Its  earlier 
departure  in  warm-blooded  animals,  may  be  partly  due  to  the  cooling  of  the 
body. 

297.  Of  the  actual  nature  of  the  changes  by  which  impressions  are  received 
upon  the  peripheral  origins  of  the  afferent  nerves,  or  are  communicated  to  the 

*  A  large  amount  of  evidence  confirmatory  of  the  above  views,  and  showing  the  im- 
portance of  carefully  distinguishing  between  the  alkaline  and  earthy  phosphates,  has  been 
adduced  by  Dr.  Bence  Jones,  in  a  Paper  lately  read  to  the  Royal  Society.  The  quantity  of 
the  latter,  which  is  present  in  the  urine,  is  found  to  bear  a  constant  relation  to  that  which  is 
contained  in  the  food.  On  the  other  hand,  the  amount  of  the  former  varies  with  different 
conditions  of  the  nervous  system,  in  such  a  manner  as  to  warrant  the  inference  that  its  pro- 
duction is  a  result  of  the  disintegration  of  nervous  matter;  being  due  to  the  union  of  the 
phosphoric  acid  thus  set  free,  with  alkaline  bases  present  in  the  blood  in  a  state  of  feeble 
combination. 


240  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

central  origins  of  the  motor,  and  by  which  they  are  conducted  along  each  to 
their  opposite  extremities,  Physiologists  have  no  certain  knowledge.  That 
they  are  Electrical  in  their  character,  has  been,  and  still  continues  to  be,  a 
favourite  theory  with  some;  and  the  idea  seems  to  derive  support  from  the 
marked  degree  in  which  Electricity,  transmitted  along  the  Nervous  trunks, 
can  excite  the  changes  to  which  those  nerves  are  ordinarily  subservient. 
Thus,  a  feeble  galvanic  current,  transmitted  along  the  motor  nerves  of  an  ani- 
mal recently  killed,  will  call  the  muscles  supplied  by  it  into  contraction  ;  whilst, 
on  the  other  hand,  a  similar  current  transmitted  along  an  afferent  nerve,  shall 
excite  reflex  movements  through  its  ganglionic  centre.  Further,  if  the  cur- 
rent be  transmitted  along  an  afferent  nerve,  in  a  living  animal,  it  will  excite 
sensations  which  are  referred  to  the  part  whence  the  nerve  arises  ;  and,  as 
will  be  shown  hereafter  (Chap.  VI.,  Sect.  1),  Electricity  is  capable  of  thus 
producing  sensations  of  a  special  kind,  as  well  as  those  of  a  general  nature. 
Moreover,  in  the  instantaneousness  of  the  transmission  of  Nervous  agency 
from  one  part  of  the  system  to  another,  there  is  more  analogy  to  Electricity, 
than  to  any  other  known  force.  But  these  and  similar  arguments  do  not  prove 
the  identity  of  Nervous  agency  with  Electricity ;  since  the  effects  of  the  for- 
mer may  be  imitated  to  a  certain  extent,  not  merely  by  Electricity,  but  by 
mechanical  and  chemical  stimulation  of  various  kinds.  Further,  there  are 
powerful  arguments  against  such  a  supposition,  the  validity  of  which  cannot 
be  easily  set  aside.  All  attempts  to  prove  the  existence  of  an  Electric  current, 
in  a  Nervous  trunk  that  is  actively  engaged  in  conveying  motor  influence, 
have  completely  failed,  though  made  with  the  greatest  precaution.  Thus,  Mat- 
teucci  has  lately  experimented  upon  the  very  large  crural  nerve  of  a  Horse, 
which  was  caused,  by  stimulating  its  roots,  to  throw  the  muscles  of  the  leg 
into  violent  contraction  ;  nevertheless,  although  he  used  instruments  of  such 
delicacy,  as  to  be  capable  of  detecting  an  infinitesimally-small  disturbance  of 
the  electric  equilibrium,  no  such  disturbance  was  apparent.  Further,  it  is  well 
known  that  the  conducting  power  of  the  nerves  is  destroyed,  not  merely  by 
dividing  the  trunk,  but  also  by  putting  a  ligature  round  it ;  which  last  opera- 
tion does  not  diminish  its  powers  as  a  conductor  of  Electricity.  Moreover, 
the  various  fibrils  are  not  as  completely  insulated  from  each  other  in  regard  to 
Electricity,  as  we  know  them  to  be  with  respect  to  nervous  agency  ;  for  the 
first  of  these  forces,  when  transmitted  along  a  nervous  trunk,  cannot  be  re- 
stricted to  any  fibre  or  fasciculus  of  fibres,  but  spreads  through  the  entire 
trunk,  and  even  to  the  neighbouring  parts  in  which  it  is  imbedded;  whilst  the 
latter  is  continually  restricted  to  a  small  portion  of  the  trunk,  as  is  manifested 
by  its  results.  Again,  if  a  small  piece  of  nervous  trunk  be  cut  out,  and  be 
replaced  by  an  electric  conductor,  electricity  will  still  pass  along  the  nerve ; 
but  no  nervous  force,  excited  by  stimulus  above  the  section,  will  be  propa- 
gated through  the  conductor  to  the  parts  below.  And  lastly,  the  conducting 
power  of  Nerve  for  Electricity  is  stated  by  Matteucci  to  be  not  more  than 
one-fourth  that  of  Muscle ;  whilst  Messrs.  Todd  and  Bowman  give  it  as  the 
result  of  their  experiments,  that  both  Nerve  and  Muscle  are  both  infinitely 
worse  conductors  than  copper ;  their  power  of  conduction  not  ranking  above 
that  of  water  holding  in  solution  a  small  quantity  of  saline  matter. 

a.  Although,  for  the  sake  of  convenience,  Electricity  and  Nervous  power  are  spoken  of, 
here  and  elsewhere,  as  actual  entities  or  agents,  traveling  along  the  wires  or  cords  that  con- 
duct them,  it  must  not  be  forgotten  that  the  present  tendency  of  scientific  inquiry  leads  us 
to  abandon  such  an  idea,  in  the  former  case  at  least ;  what  is  commonly  termed  the  trans- 
mission of  electricity  being  the  result  of  a  molecular  change,  instantaneously  occurring  along 
the  whole  length  of  the  conducting  body,  in  virtue  of  a  disturbance,  in  the  polar  arrangement 
of  its  particles,  at  one  extremity,  which  causes  a  similar  disturbance  to  manifest  itself  at  the 
other.  Thus  if 

ab     ab     ab     ab     ab     ab     ab     ab 


LAWS  OF  NERVOUS  TRANSMISSION.  241 

represent  the  arrangement  of  the  particles,  in  the  condition  of  equilibrium  or  quiescence,  and 
this  condition  be  disturbed  at  one  extremity,  by  the  operation  of  a  new  attraction  upon  the 
first  particle  a,  a  new  arrangement  will  instantaneously  take  place  throughout:  this  may  be 
represented  by 

a     ba     ba     ba     ba     ba     ba     ba     b 

which  shows  b  in  a  free  state  at  the  opposite  end,  ready  to  exert  its  influence  upon  anything 
submitted  to  it.  It  is  probable  that  in  this  respect  there  is  an  analogy  between  the  Nervous 
and  electrical  forces ;  and  that,  instead  of  speaking  of  the  "transmission  of  nervous  influence" 
along  a  nerve,  we  should  describe  the  change  as  the  production  of  a  "  polar  state"  in  the 
nervous  trunk;  as  first  pointed  out  by  Messrs.  Todd  and  Bowman  (Physiological  Anatomy, 
vol.  i.  p.  240). 

298.  Every  fibre,  there  is  reason  to  believe,  runs  a  distinct  course  between 
the  central  organ,  in  which  it  loses  itself  at  one  extremity,  and  the  muscle  or 
organ  of  sense  in  which  it  terminates  at  the  other.     Each  Nervous  Trunk  is 
made  up  of  several  fasciculi  of  these  fibres ;  and  each  fasciculus  is  composed 
of  a  large  number  of  the  ultimate  fibres  themselves.     Although  the  fasciculi 
occasionally  intermix  and  exchange  fibres  with  one  another  (as  occurs  in  what 
is  termed  a  plexus),  the  fibres  themselves  never  inosculate.     Each  fibre  would 
seem,  therefore,  to  have  its  appropriate  office,  which  it  cannot  share  with 
another.     The  objects  of  a  plexus  are  twofold.     In  some  instances  it  serves 
to   intermix  fibres,  which    have   endowments   fundamentally   different :    for 
example,  the  Spinal  Accessory  nerve,  at  its  origin,  appears  to  be  exclusively 
motor,  and  the   roots  of  the  Par  Vagum  are  as  exclusively  afferent ;  but  by 
the  early  admixture  of  these,  a  large  number  of  motor  fibres  are  imparted  to 
the  Par  Vagum,  and  are  distributed  in  variable  proportion,  with  its  different 
branches  ;  whilst  few  of  its  sensory  filaments  seem  to  enter  the  Spinal  Acces- 
sory.— In  other  instances,  the  object  of  a  plexus  appears  to  be,  to  give  a  more 
advantageous  distribution  to  fibres,  which  all  possess  corresponding  endow- 
ments.    Thus  the  Brachial  plexus  mixes  together  the  fibres  arising  from  five 
segments  of  the  spinal  cord,  and  sends  off  five  principal  trunks  to  supply  the 
arm.     Now  if  each  of  these  trunks  had  arisen  by  itself,  from  a  distinct  seg- 
ment of  the  spinal  cord,  so  that  the  parts  on  which  it  is  distributed  had  only 
a  single  connection  with  the  nervous  centres,  they  would  have  been   much 
more  liable  to  paralysis  than  at  present.     By  means  of  the  plexus,  every  part 
is  supplied  with  fibres  arising  from  each  segment  of  the  spinal  cord  ;  and  the 
functions  of  the  whole  must  therefore  be  suspended,  before  complete  paralysis 
of  any  part  can  occur,  from  a  cause  which  operates  above  the  plexus.     Such 
a  view  is  borne  out  by  direct  experiment;  for  it  has  been  ascertained  by 
Panizza  that,  in  Frogs,  whose  crural  plexus  is  much  less  complicated  than 
that  of  Mammalia,  section  of  the  roots  of  one  of  the  three  nerves  which  enter 
into  it,  produces  little  effect  on  the  general  movements  of  the  limb ;  and  that, 
even  when  two  are  divided,  there  is  no  paralysis  of  any  of  its  actions,  all 
being  weakened  in  a  nearly  similar  degree. — It  is  not  unlikely  also  that,  by 
this  arrangement,  a  consentaneousness  of  action  is  in  some  degree  favoured,  as 
is  supposed  by  Sir  C.  Bell;  for  comparative  anatomy  shows  that  something 
resembling  it  may  be  traced,  wherever  a  similar  purpose  has  to  be  attained. 
Thus,  in  the  Hymenoptera,  there  is  a  similar  interlacement  between  the  nerves 
of  the  anterior  and  posterior  pairs  of  wings,  which  act  very  powerfully  to- 
gether; whilst  in  the  Coleoptera,  in  which  the  anterior  wings  are  converted 
into  elytra,  and  are  motionless  during  flight,  the  nerves  supplying  each  pair 
run  their  course  distinctly.     In  the  Octopus,  or  Poulp,  again,  the  trunks  which 
radiate  from  the  cephalic  mass  to  the  eight  large  arms  surrounding  the  head, 
are  connected  by  a  circular  band ;  forming  a  kind  of  plexus,  which  seems  to 
contribute  to  the  very  powerful  and  harmonious  movements  of  the  arms  of 
this  Cephalopod. 

299.  The  following  statements,  in  which  the  language  of  Miiller  is  adopted 
21 


242  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

with  some  modification,  embody  the  general  principles  ascertained  by  ex- 
periment, respecting  the  transmission  of  sensory  and  motor  impressions. 
Their  rationale  will  be  at  once  understood,  from  the  facts  already  mentioned 
in  regard  to  the  isolated  characters  of  each  fibril,  and  the  identity  of  its 
endowments  through  its  whole  course,  i.  When  the  whole  trunk  of  a  sensory 
nerve  is  irritated,  a  sensation  is  produced,  which  is  referred  by  the  mind  to 
the  parts  to  which  its  branches  are  ultimately  distributed  ;  and  if  only  part  of 
the  trunk  be  irritated,  the  sensation  will  be  referred  to  those  parts  only,  whicli 
are  supplied  by  the  fibrils  it  contains. — This  is  evidently  caused  by  the  pro- 
duction of  a  change  in  the  sensorium,  corresponding  with  that  which  would 
have  been  transmitted  from  the  peripheral  origins  of  the  nerves,  had  the 
impression  been  made  upon  them.  Such  a  change  only  requires  the  integrity 
of  the  afferent  trunk,  between  the  point  irritated  and  the  sensorium ;  and  is 
not  at  all  dependent  upon  the  state  of  the  extremity,  to  which  the  sensations 
are  referred  :  for  this  may  have  been  paralyzed  by  the  division  of  the  nerve  ; 
or  altogether  separated,  as  in  amputation;  or  the  relative  position  of  its  parts 
may  have  been  changed. — It  results  from  the  foregoing,  that,  when  different 
parts  of  the  thickness  of  the  same  trunk  are  separately  subjected  to  irritation, 
the  sensations  are  successively  referred  to  the  several  parts  supplied  by  these 
divisions.  This  may  be  easily  shown  by  compressing  the  ulnar  nerve,  in 
different  directions,  where  it  passes  at  the  inner  side  of  the  elbow-joint. 

ii.  The  sensation  produced  by  irritation  of  a  branch  of  the  nerve,  is  con- 
fined to  the  parts  to  which  that  branch  is  distributed,  and  does  not  affect  the 
branches  which  come  off  from  the  nerve  higher  up.  The  rationale  of  this 
law  is  at  once  understood:  but  it  should  be  mentioned  that  there  are  certain 
conditions,  in  which  the  irritation  of  a  single  nerve  will  give  rise  to  sensations 
over  a  great  extent  of  the  body.  This  seems  due,  however,  to  a  particular 
state  of  the  central  organs  ;  and  not  to  any  direct  communication  among  the 
sensory  fibres. 

in.  The  motor  influence  is  propagated  only  in  a  centrifugal  direction,  never 
in  a  retrograde  course.  It  may  originate  in  a  spontaneous  change  in  the 
central  organs:  or  it  may  be  excited  by  an  impression  conveyed  to  them 
through  afferent  nerves ;  but  in  both  cases  its  law  is  the  same. 

iv.  When  the  whole  trunk  of  a  motor  nerve  is  irritated,  all  the  muscles 
wrhich  it  supplies  are  caused  to  contract:  but  when  only  a  part  of  the  trunk 
or  a  branch  is  irritated,  the  contraction  is  confined  to  the  muscles,  which 
receive  their  nervous  fibres  from  it.  This  contraction  evidently  results  from 
the  similarity  between  the  effect  of  an  artificial  stimulus  applied  to  the  trunk 
in  its  course,  and  that  of  the  change  in  the  central  organs  by  which  the  motor 
influence  is  ordinarily  propagated.  In  this  instance,  as  in  the  other,  there  is 
no  lateral  communication  between  the  fibrils. 

300.  Various  methods  of  determining  the  functions  of  particular  nerves 
present  themselves  to  the  Physiological  inquirer.  One  source  of  evidence  is 
drawn  from  their  anatomical  distribution.  For  example,  if  a  nervous  trunk 
is  found  to  lose  itself  entirely  in  the  substance  of  muscles,  it  may  be  inferred 
to  be  chiefly,  if  not  entirely,  motor  or  efferent.  In  this  manner,  Willis  long 
ago  determined  that  the  third,  fourth,  sixth,  portio  dura  of  the  seventh,  and 
ninth  cranial  nerves,  are  almost  entirely  subservient  to  muscular  movement; 
and  the  same  had  been  observed  of  the  fibres  proceeding  from  the  small  root 
of  the  fifth  pair,  before  Sir  C.  Bell  experimentally  determined  the  double 
function  of  that  division  of  the  nerve,  into  which  alone  it  enters.  Again, 
where  a  nerve  passes  through  the  muscles,  with  little  or  no  ramification  among 
them,  and  proceeds  to  a  cutaneous  or  mucous  surface,  on  which  its  branches 
are  minutely  distributed,  there  is  equal  reason  to  believe  that  it  is  of  a  sensory, 
or  rather  of  an  afferent,  character.  In  this  manner  Willis  came  to  the  con- 


' 


DETERMINATION  OF  FUNCTIONS  OF  NERVES.  243 

elusion,  that  the  fifth  pair  of  cranial  nerves  differs  from  those  previously 
mentioned,  in  being  partly  sensory.  Further,  where  a  nerve  is  entirely  dis- 
tributed upon  a  surface  adapted  to  receive  impressions  of  a  special  kind, — as 
the  Schneiderian  membrane,  the  retina,  or  the  membrane  lining  the  internal 
ear, — it  may  be  inferred  that  it  is  not  capable  of  transmitting  any  other  kind 
of  impressions;  for  experiment  has  shown,  that  the  special  sensory  nerves  do 
not  possess  common  sensibility.  The  case  is  different,  however,  in  regard  to 
the  sense  of  taste,  which  originates  in  impressions  not  far  removed  from  those 
of  ordinary  touch;  and  it  is  probable  that  the  same  nerves  minister  to  both. — 
Anatomical  evidence  of  this  kind  is  valuable  also,  not  only  in  reference  to  the 
functions  of  a  principal  trunk,  but  even  as  to  those  of  its  several  branches, 
which,  in  some  instances,  differ  considerably.  Thus,  some  of  the  branches  of 
the  Par  Vagum  are  especially  motor,  and  others  almost  exclusively  afferent;  and 
anatomical  examination,  carefully  prosecuted,  not  only  assigns  the  reasons  for 
these  functions,  when  ascertained,  but  is  in  itself  nearly  sufficient  to  determine 
them.  Thus  the  superior  laryngeal  branch  is  distributed  almost  entirely  upon 
the  mucous  surface  of  the  larynx,  the  only  muscle  it  supplies  being  the  crico- 
thyroid ;  whilst  the  inferior  laryngeal  or  recurrent  is  almost  exclusively  dis- 
tributed to  the  muscles.  From  this  we  should  infer,  that  the  former  is  an 
afferent,  and  the  latter  a  motor  nerve  ;  and  experimental  inquiries  (hereafter  to 
be  detailed)  fully  confirm  this  view.  In  like  manner  it  may  be  shown,  that 
the  Glosso-pharyngeal  is  chiefly  an  afferent  nerve,  since  it  is  distributed  to  the 
surface  of  the  tongue  and  pharynx,  and  scarcely  at  all  to  the  muscles  of  those 
parts ;  whilst  the  pharyngeal  branches  of  the  Par  Vagum  are  chiefly  if  not 
entirely,  motor.  Lower  down,  however,  the  branches  of  the  glosso-pharyn- 
geal  cease,  and  the  oesophageal  branches  of  the  par  vagum  are  distributed  both 
to  the  mucous  surface  and  to  the  muscles ;  from  which  it  may  be  inferred  that 
they  are  both  afferent  and  motor — a  deduction  which  experiment  confirms. 

301.  We  perceive,  therefore,  that  much  knowledge  of  the  function  of  a 
nerve  may  be  obtained,  from  the  attentive  study  of  its  ultimate  distribution: 
but  it  is  necessary  that  this  should  be  very  carefully  ascertained,  before  it  is 
made  to  serve  as  the  foundation  for  physiological  inferences.     As  an  example 
of  former  errors  in  this  respect,  may  be  mentioned  the  description  of  the 
Portio  Dura  of  the  seventh,  at  first  given  by  Sir  C.  Bell:  he  stated  it  to  be 
distributed  to  the  skin  as  well  as  to  the  muscles  of  the  face,  and  evidently 
regarded  it  as  in  part  an  afferent  nerve,  subservient  to  respiratory  impressions 
as  well  as  to  motions.     In  the  same  manner,  from  inaccurate  observation  of 
the  ultimate  distribution  of  the  Superior  Laryngeal  nerve,  it  was  long  re- 
garded as  that  which  stimulated  to  action  the  constrictors  of  the  glottis. — But 
the  knowledge  obtained  by  such  anatomical  examinations  alone  is  of  a  very 
general  kind ;  and  requires  to  be  made  particular, — to  be  corrected  and  modi- 
fied by  other  sources  of  information.     One  of  these  relates  to  the  connection 
of   the   trunks  with  the   central  organs.     The   evidence   derived   from   this 
source,  however,  is  seldom  of  a  very  definite   character;    and,  in  fact,  the 
functions   of  particular  divisions   of  the   nervous  centres   have   rather  been 
hitherto  judged  of,  by  those  of  the  nerves  with  which  they  are  connected, 
than   afforded   aid   in  the   determination   of   the  latter.     Still,   this   kind   of 
examination  is  not  without  its  use,  when  there  is  reason  to  believe  that  a 
particular  tract  of  fibrous  structure  has  a  certain  function,  and  when  the  office 
of  a  nerve  whose  roots  terminate  in  it  is  doubtful.     Here  again,  however, 
very  minute  and  accurate  examination  is  necessary,  before  any  sound  physio- 
logical inferences  can  be  drawn  from  facts  of  this  description ;  and  many 
instances  might  be  adduced  to  show,  that  the  real  connections  of  nerves  and 
nervous  centres  are  often  very  different  from  their  apparent  ones, 

302.  Experimental  inquiries  into  the  functions  of  particular  nerves  are  also 


244  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

liable  to  give  fallacious  results,  unless  they  are  prosecuted  with  a  full  know- 
ledge of  all  the  precautions  necessary  to  insure  success.  Some  of  these  will 
be  here  explained.  Suppose  that,  upon  irritating  the  trunk  of  a  nerve,  whilst 
still  in  connection  with  its  centre,  muscular  movements  are  excited ;  it  must 
not  be  hence  concluded  that  the  nerve  is  an  efferent  one,-  for  it  may  have  no 
directly  motor  powers.  The  next  step  would  be  to  divide  the  trunk,  and  to 
irritate  each  of  the  cut  extremities.  If,  upon  irritating  the  end  separated 
from  the  centre,  muscular  contractions  are  produced,  it  may  be  safely  inferred 
that  the  nerve  is,  in  part  at  least,  of  an  efferent  character.  Should  no  such 
result  follow,  this  would  be  doubtful.  If,  on  the  other  hand,  muscular  move- 
ment should  be  produced  by  irritating  the  extremity  in  connexion  with  the 
centre,  it  will  then  be  evident,  that  it  is  occasioned  by  an  impression  conveyed 
towards  the  centre  by  this  trunk,  and  propagated  to  the  muscles  by  some 
other;  in  other  words,  to  use  the  language  of  Dr.  M.  Hall,  this  nerve  is  an 
excitor  of  motion,  not  a  direct  motor  nerve.  The  glosso-pharyngeal  nerve 
has  been  satisfactorily  determined  to  be  chiefly,  if  not  entirely,  an  efferent 
nerve,  by  experiments  of  this  kind,  performed  by  Dr.  J.  Reid. 

303.  It  has  been  from  the  want  of  a  proper  mode  of  experimenting,  that 
the  functions  of  the  posterior  roots  of  the  Spinal  nerves  have  been  regarded 
as  in  any  degree  motor.     If  they  be  irritated,  without  division  of  either  root, 
motions  are  often  excited;  but  if  they  be  divided,  and  their  separated  trunks 
be  then  irritated,  no  motions  ensue;  nor  are  any  movements  produced  by 
irritation  of  the  roots  in  connexion  with  the  spinal  cord,  if  the  anterior  roots 
have  been  divided.     Hence  it  appears  that  the  motor  powers  of  these  fibres 
are  not  direct,  but  that  they  convey  an  impression  to  the  centre,  which  is 
reflected  to  the  muscles  through  the  anterior  roots.    Another  source  of  fallacy 
is  to  be  guarded   against,  arising  from  the  communication  to  a  nerve,  in  its 
course,  of  properties  it  did  not  possess  at  its  root,  by  inosculation  with  an- 
other nerve.     Of  this  many  instances  will  hereafter  present  themselves. 

304.  The  same  difficulties  do  not  attend  the  determination  of  the  sensory 
properties  of  nerves.     If,  when  the  trunk  of  a  nerve  be  pricked  or  pinched, 
the  animal  exhibits  signs  of  pain,  it  may  be  concluded  that  the  nerve  is  sen- 
sible to  ordinary  impressions  at  its  peripheral  extremity.     But  not  unfre- 
quently  this  sensibility  is  derived  by  inosculation  with  another  nerve ;  as  is 
the  case  with  the  portio  dura,  which  is  sensory  after  it  has  passed  through 
the  parotid  gland,  having  received  there  a  twig  from  the  fifth  pair.     A  similar 
inosculation  explains  the   apparent  sensibility  of  the  anterior  roots  of  the 
spinal  nerves.     If  these  be  irritated,  the  animal  usually  gives  signs  of  uneasi- 
ness ;  but  if  they  be  divided,  and  the  cut  ends  nearest  the  centre  be  irritated, 
none  such  are  exhibited ;  whilst  they  are  still  shown,  when  the  farther  ends 
are  irritated,  but  not  if  the  posterior  roots  are  divided.     This  seems  to  indi- 
cate that,  from  the  point  of  junction  of  the  two  roots,  sensory  fibres  derived 
from  the  posterior  root  pass  backwards  (or  towards  the  centre)  in  the  anterior; 
and  thus  its  apparent  sensory  endowments  are  entirely  dependent  upon  its 
connexion  with  the  posterior  column  of  the  spinal  cord,  through  the  posterior 
roots. 

305.  The  fallacies  to  which  all  experiments  upon  the  nerves  are  subject, 
arising  from  the  partial  loss  of  their  powers  of  receiving  and  conveying  im- 
pressions, and  of  exciting  the  muscles  to  action,  after  death,  are  too  obvious 
to  require  particular  mention  here;  yet  they  are  frequently  overlooked.     Of 
a  similar  description  are  those  arising  from  severe  disturbance  of  the  system, 
in  consequence  of  operations;  which  also  have  not  been  enough  regarded  by 
experimenters. 

306.  All  our  positive  knowledge  of  the  functions  of  the  Nervous  System 
in  general,  save  that  which  results  from  our  own  consciousness  of  what  passes 


DETERMINATION  OF  FUNCTIONS  OF  NERVES.  245 

within  ourselves,  and  that  which  we  obtain  from  watching  the  manifestations 
of  disease  in  Man,  is  derived  from  observation  of  the  phenomena  exhibited 
by  animals  made  the  subjects  of  experiments;  and  it  is  desirable  to  preface 
our  general  summary  of  the  results  of  these,  by  some  remarks  upon  the  in- 
ferences to  be  drawn  from  them. — In  the  first  place  it  must  be  constantly 
borne  in  mind  that,  except  through  the  movements  consequent  upon  them, 
we  have  no  means  of  ascertaining,  whether  or  not  particular  changes  in  the 
Nervous  System,  whose  character  we  are  endeavoring  to  determine,  are 
attended  with  Sensation;  since  we  have  no  power  of  judging  whether  or  not 
this  has  been  excited,  save  by  the  cries  and  struggles  of  the  animal  made  the 
subject  of  experiment.  Now  although  such  cries  and  struggles  are  ordinarily 
considered  as  indications  of  pain,  yet  it  is  not  right  so  to  regard  them  in  every 
instance;  and  the  only  unequivocal  evidence  is  derived  from  observation  of 
the  corresponding  phenomena  in  the  Human  subject;  since  we  can  there 
ascertain,  by  the  direct  testimony  of  the  individual  affected,  what  impressions 
produce  sensation,  and  what  excite  movements  independently  of  sensation. 
Further,  we  are  not  justified  in  assuming  that  consciousness  is  excited  by  an 
irritation, — still  less  that  the  intelligence  and  will  are  called  into  exercise  by 
it, — merely  because  movements,  evidently  tending  to  get  rid  of  this,  are  per- 
formed in  respondence  to  it.  We  know  that  the  contractions  of  the  heart 
and  alimentary  tube  are  ordinarily  excited  by  a  stimulus,  without  any  sensa- 
tion being  involved;  and  these  movements,  like  all  that  are  concerned  in  the 
maintenance  of  the  Organic  functions,  have  an  obvious  design,  when  con- 
sidered either  in  their  immediate  effects,  or  in  their  more  remote  consequences. 
The  character  of  adaptiveness,  then,  in  Muscular  movements  excited  by 
external  stimuli,  is  no  proof  that  they  are  performed  in  obedience  to  sensa- 
tion ;  much  less,  that  they  have  a  voluntary  character.  In  no  case  is  this 
adaptiveness  more  remarkable,  than  in  some  of  those  actions,  which  are  not 
only  performed  without  any  effort  of  the  will,  but  which  the  will  cannot 
imitate.  This  is  the  case,  for  example,  with  the  act  of  Deglutition;  the 
muscles  concerned  in  which  cannot  be  thrown  into  contraction  by  a  voluntary 
impulse,  being  stimulated  only  by  impressions  conveyed  from  the  mucous 
surface  of  the  fauces  to  the  medulla  oblongata,  and  thence  reflected  along  the 
the  motor  nerves.  No  one  can  swallow  without  producing  an  impression  of 
some  kind  upon  this  surface,  to  which  the  muscular  movements  will  imme- 
diately respond.  Now  it  is  impossible  to  conceive  any  movements  more 
perfectly  adapted  to  a  given  purpose  than  those  of  the  parts  in  question ;  and 
yet  they  are  independent,  not  only  of  Volition,  but  of  Sensation, — being  still 
performed  in  cases  in  which  consciousness  is  completely  suspended,  or 
entirely  absent. 

307.  There  is  much  difficulty,  then,  in  ascertaining  the  really  elementary 
functions  of  the  Nervous  System,  by  experiments  upon  animals ;  and  it  is 
only  when  their  results  are  corrected  and  explained  by  pathological  observa- 
tion on  Man, — the  sole  case  in  which  we  can  obtain  satisfactory  evidence  of 
the  presence  or  absence  of  sensation, — that  they  have  much  value  to  the  phy- 
siological inquirer.  From  these  combined  sources,  however,  a  vast  amount 
of  knowledge  of  the  functions  of  the  nervous  system  has  recently  been  gained; 
and  the  general  purposes  to  which  it  is  subservient,  may  be  advantageously 
stated  in  a  systematic  form,  before  we  enter  upon  any  detailed  examination  of 
them. 

i.  The  Nervous  System  receives  impressions,  which,  being  conveyed  by 
its  afferent  fibres  to  the  Sensorium,  are  there  communicated  to  the  conscious 
Mind,  and  thus  give  origin  to  Sensations.  The  Nervous  structure  is  further 
subservient,  in  some  way,  to  the  acts  of  that  mind ;  as  the  result  of  which,  a 
motor  impulse  is  transmitted  along  the  efferent  trunks,  to  particular  Muscles, 


246  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

exciting  them  to  contraction.  There  is  reason  to  believe,  however,  that  this 
motor  impulse  may  proceed  from  at  least  two  distinct  sources;  being  either 
the  direct  consequence  of  the  sensation,  acting  involuntarily  as  an  emotional 
or  instinctive  impulse  ;  or  resulting  from  a  more  or  less  complicated  series 
of  intellectual  operations,  which  terminate  in  an  act  of  volition  or  will. — To 
these  functions,  taken  collectively,  the  Encephalon,  and  the  nerves  connected 
with  it,  are  alone  subservient ;  and  we  may  probably  assign  the  group  of  sim- 
ple consensual  or  involuntary  actions  to  the  ganglia  which  receive  the  nerv- 
ous trunks  from  the  organs  of  sense,  and  which  make  up  nearly  the  whole 
of  the  Cephalic  masses  of  ganglia  in  the  Invertebrata  ;  whilst  the  Cerebral 
hemispheres  of  Vertebrata  are  the  instruments  of  the  intellectual  operations 
and  of  the  mandates  of  the  will. 

ii.  Certain  parts  of  the  Nervous  System  receive  impressions  which  are 
propagated  along  afferent  fibres,  that  terminate  in  ganglionic  centres  distinct 
from  the  sensorium;  and  in  these  a  reflex  motor  impulse  is  excited,  which, 
being  conveyed  along  the  efferent  trunks  proceeding  from  them,  excites  mus- 
cular contraction,  without  any  necessary  intervention  of  sensation  or  volition. 
Of  this  function  (called  by  Dr.  Hall,  to  whom  the  discovery  of  it  is  in  a  great 
part  due,  the  reflex  function),  we  shall  find  that  the  portion  of  the  Spinal 
Cord  of  Vertebrata,  which  is  not  continuous  with  the  fibrous  structure  of  the 
brain,  together  with  the  portion  of  the  nervous  trunks  which  are  connected 
with  it  alone,  is  the  instrument:  whilst,  in  the  Invertebrata,  the  same  office 
is  performed  by  ganglia  still  more  obviously  disconnected  from  the  cephalic 
mass. 

in.  Another  division  of  the  Nervous  System  appears  to  have  for  its  object, 
to  combine  and  harmonize  the  muscular  movements  immediately  connected 
with  the  maintenance  of  Organic  life ;  and  to  bring  these  into  relation  with 
certain  conditions  of  the  mind.  There  is  reason  to  believe  (though  this  is 
less  certain)  that  it  also  influences,  and  brings  into  connection  with  each  other, 
the  processes  of  Nutrition.  Secretion,  &c. ;  though  these,  like  the  muscular 
movements  just  mentioned,  are  essentially  independent  of  it.  This  portion 
of  the  nervous  apparatus  is  commonly  known  under  the  name  of  the  Sympa- 
thetic system. 

308.  "Now,  in  reference  to  the  first  of  these  classes  of  operations,  it  is  well 
to  explain  that  though  the  Physiologist  speaks  of  the  intellectual  powers, 
moral  feelings,  &c.,  as  functions  of  the  Nervous  System,  they  are  not  so  in 
the  sense  in  which  the  term  is  employed  in  regard  to  other  operations  of  the 
bodily  frame.     In  general,  by  the  function  of  an  organ,  we  understand  some 
change  which  may  be  made  evident  to  the  senses  ;  as  well  in  our  own  sys- 
tem, as  in  the  body  of  another.     Sensation,  Thought,  Emotion,  and  Volition, 
however,  are  changes  imperceptible  to  our  senses,  by  any  means  of  observa- 
tion we  at  present  possess.     We  are  cognizant  of  them  in  ourselves,  without 
the  intervention  of  those  processes  by  which  we  observe  material  changes 
external  to  our  minds  ;  but  we  judge  of  them  in   others,  only  by  inferences 
founded  on  the  actions  to  which  they  give  rise,  when  compared  with  our  own. 
When  we  speak  of  sensation,  thought,  emotion  or  volition,  therefore,  as  func- 
tions of  the  Nervous  System,  we  mean   only  that  this  system  furnishes  the 
conditions  under  which  they  take  place  in  the  living  body ;   and  we  leave  the 
question  entirely  open,  whether  the  "Vvzy  has  or  has  not  an  existence  independ- 
ent of  that  of  the  material  organism,  by  which  it  operates  in  Man,  as  he  is 
at  present  constituted. 

309.  In  regard  to  the  second  class  of  actions,  it  may  be  remarked,  that  they 
are  nearly  all  connected,  more  or  less  closely,  with  the  maintenance  of  the 
Organic  functions,  or  with  the  protection  of  the  body  from  danger.     Thus 
the  movements  of  the  pharynx  supply  to  the  stomach  the  alimentary  materi- 


COMPARATIVE  ANATOMY  AND  PHYSIOLOGY. RADIATA.  247 

als,  which  it  has  to  prepare  for  the  nutrition  of  the  body ;  and  those  of  the 
muscles  of  the  thorax,  &c.,  maintain  that  constant  interchange  of  air  in  the 
lungs,  which  is  necessary  for  the  aeration  of  the  blood :  whilst  those,  by 
which  a  limb  is  involuntarily  retracted  from  any  cause  of  pain  or  irritation,  are 
obviously  adapted  to  the  latter  of  these  two  ends. 

2.   Comparative  Anatomy  and  Physiology  of  the  Nervous  System  in 
Invertebrated  •Animals. 

310.  Although  the  structure  and  distribution  of  the  Nervous  System  in  the 
different  classes  of  Animals  have  been,  until  recently,  but  little  appealed  to 
in  the  determination  of  its  functions,  they  are  capable  of  supplying  evidence 
regarding  some  of  these,  not  less  important  in  its  character  than  that  which 
Comparative  Anatomy  affords  to  other  departments  of  Physiology.     Some  of 
the  principal  of  these  contributions  will  now  be  pointed  out. 

311.  In  the  lowest  tribes  of  the  RADIATED  division  of  the  animal  kingdom, 
no  Nervous  System  has  yet  been  discovered.     These  have,  therefore,  been 
separated  by  some  naturalists  into  a  new  primary  group,  to  which  the  desig- 
nation of  Jicrita  has  been  given,  on  account  of  the  (supposed)  "indistinct, 
diffused,  or  molecular  character  of  their  nervous  system."     This  idea  of  a 
"diffused  nervous  system"  seems  to  be  regarded  by  many — Physiologists  as 
well  as  Naturalists — as  the  necessary  alternative,  resulting  from  the  want  of 
any  definite  indications  of  its  presence.     It  may  be  said,  however,  to  be  based 
on  very  erroneous  notions,  as  to  the  true  offices  of  the  nervous  apparatus. 
Its  influence  is  not  required  to  endow  the  tissues  with  contractility  $  a  pro- 
perty possessed  in  a  high  degree  by  the  structures  of  many  Plants,  to  which 
these  beings  present  a  much  greater  general  resemblance,  than  they  bear  to 
the  higher  Animals;  and,  even  in  the  latter  (as  will  be  shown  hereafter),  this 
property  is   independent  of  nervous  agency,  although  generally  called  into 
exercise  by  it.     That  a  nervous  system  is  not  required  by  them  for  the  per- 
formance of  the  functions  of  Nutrition  and  Reproduction,  otherwise  than  to 
supply,  by  its  locomotive  actions,  the  conditions  of  those  functions,  would 
also  appear  from  its  absence  in  Pfants.     It  is  on  the  sensible  movements  of 
these  beings,  that  our  belief  in  their  possession  of  a  nervous  system  must  be 
founded,  when  we  cannot  render  it  cognizable  by  our  senses.     But  we  must 
be  careful  not  to  draw  hasty  inferences  from  such  phenomena.    Sensible  move- 
ments are,  as  we  have  seen,  performed  by  the  Dionaea  and  Sensitive  plant,  in 
respondence  to  external  stimuli  acting  on  distant  organs  ;  and  they  are  also 
exhibited,  in  a  very  remarkable  manner,  by  the  reproductive  particles  of  many 
of  the  simpler  Plants,  as  well  as  by  numerous  beings  now  generally  referred 
to  the  Vegetable  kingdom.     It  is  to  be  remarked,  however,  that  such  motions 
are  of  a  very  simple  description.     In  objects  of  the  latter  class,  they  are  of 
a  rhythmical  character,  and  do  not  seem  to  be  in  direct  dependence  on  any 
external  influences.     And  even  where  they  are  performed  solely  in  respond- 
ence to  external  stimuli,  there  is  usually  such  a  uniformity  in  their  character, 
as  indicates  that  the  means  by  which  the  influence  is  propagated  are  of  a  very 
mechanical  nature.     On  the  other  hand,  those  movements  of  Polypes,  which 
are  performed  in  respondence  to  external  stimuli,  are  of  a  much  more  varied 
character;  and  there  are  others,  which  seem  to  indicate  a  certain  degree  of 
voluntary  power,  and  therefore  to  display  a  consciousness  of  impressions  made 
upon  the  body.     These  phenomena,  then,  would  lead  us  to  suspect  the  ex- 
istence of  a  Nervous  System  in  the  beings  which  exhibit  them ;  not,  however, 
in  a  "diffused"  condition,  but  in  the  form  of  connected  filaments.     For,  what 
consentaneousness  of  action  can  be  looked  for  in  a  being  whose  nervous 
matter  is  incorporated  in  the  state  of  isolated  globules  with  its  tissues?     How 


248  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

should  an  impression  made  on  one  part  be  propagated  by  these  to  a  distance  ? 
And  how  can  that  consciousness  and  will,  which  are  one  in  each  individual, 
exist  in  so  many  unconnected  particles  ?  If,  then,  we  allow  any  sensibility, 
consciousness,  and  voluntary  power,  to  the  beings  of  this  group  of  Acrita — 
to  deny  which  would  be  in  effect  to  exclude  them  from  the  Animal  Kingdom 
— we  must  regard  these  faculties  as  associated  with  nervous  filaments,  of  such 
delicacy  as  to  elude  our  means  of  research.  When  the  general  softness  of 
the  textures,  and  the  laxity  of  structure  that  characterizes  the  nervous  fibres, 
in  the  lowest  animals  in  which  they  can  be  traced,  are  kept  in  view,  little 
difficulty  need  be  felt  in  accounting  for  their  apparent  absence.  The  case  is 
very  different  from  that  of  Vegetable  structure ;  the  greater  consistency  of 
which  enables  us  to  place  much  more  reliance  upon  the  negative  evidence 
afforded  by  anatomical  research. 

312.  The  correctness  of  this  view  (which  has  been  here  dwelt  on  the  longer, 
because  it  involves  a  fundamental  question  in  Nervous  Physiology),  is  borne 
out  by  the  fact,  that,  in  those  members  of  the  group  whose  size  and  consist- 
ency allow  their  structures  to  be  sufficiently  examined,  a  definite  nervous 
system  has  been  detected  ;  in  the  position  which  it  might,  a  priori,  be  ex- 
pected to  occupy,  according  to  the  type  of  the  individual.     Thus,  in  the  large 
fleshy  isolated  polype,  commonly  known    as  the  Sea-Anemone  (Jictinia),  a 
nervous  ring  has  been  discovered,  surrounding  the  mouth  as  in  other  Radiata, 
and  sending  off  branches  to  the  tentacula,  with  a  minute  ganglionic  enlarge- 
ment at  the  base  of  each.     In  the  higher  Radiata,  as  the  Star-Fish,  the  nerv- 
ous system  has  the  same  regular  form  as  that  which   prevails  through  the 
other  organs.     The  mouth  is  surrounded  by  a  filamentous  ring,  which  presents 
a  regular  series  of  ganglionic  enlargements,  one  of  them  corresponding  with 
each  segment  of  the  body.     From  every  one  of  these,  a  branch  is  transmitted 
to  the  corresponding  ray  ;  and  two  smaller  ones  proceed  to  the  viscera  included 
in  the  central  disk. 

313.  The  POLYPIFERA  being  the  lowest  of  the  Radiated  classes,  in  which 
there  is  a  regularly-organized  digestive  apparatus,  and  which  perform  move- 
ments of  a  character  ascribable  only  to  a  Nervous  System,  it  will  be  desir- 
able to  inquire  a  little  more  particularly  mto  the  phenomena  they  exhibit,  and 
the  degree  in  which  these  necessarily  involve  the  possession  of  the  higher 
mental  endowments.     In  this  inquiry  we  shall  refer  principally  to  the  little 
Hydra,  or  fresh-water  Polype ;  the  habits  of  which  are  better  known  than 
those  of  any  other  species.     Although  no  nervous  filaments  have  been  de- 
tected in  this,  we  have  a  right  to  infer  their  presence  for  the  reasons  already 
given ;  and  they  probably  form  a  ring  around  the  mouth,  as  in  the  Actinia, 
sending  filaments  to  the  tentacula.     This  interesting  little  being  may  be  re- 
garded as  essentially  a  stomach;    and  the  orifice  of  this  is  provided  with 
tentacula,  which  contract  when  irritated  by  the  touch  of  any  adjacent  body, 
and  endeavour  to  draw  it  towards  the  entrance      Now,  the  action  in  the  Hu- 
man body,  to  which  this  is  most  allied,  is  evidently  that  of  the  muscles  of 
Deglutition ;  which  lay  hold,  as  it  were,  of  the  food  that  has  been  conveyed 
to  the  fauces,  and  carry  it  into  the  stomach.     These  muscles  are  called  into 
action,  not  by  an  effort  of  the  will,  but  by  the  contact  of  the  food  with  the 
lining   membrane  of  the   pharynx.     This   impression  is  propagated  by  the 
glosso-pharyngeal  nerve  to  the  medulla  oblongata.  where  a  respondent  motor 
impulse  is  excited,  which  is  transmitted  through  the  pharyngeal  branches  of 
the  par  vagum  to  the  muscles  of  deglutition,  and  causes  their  contraction. 
This  phenomenon  will  be  more  fully  examined  hereafter ;  it  is  here  adduced 
simply  as  an  instance  of  the  important  class  of  reflex  movements,  which  are 
independent  of  the  brain  (though,  to  a  certain  extent,  controlled  by  it),  which 
are  altogether  involuntary,  and  which  do  not  necessarily  involve  the  produc- 


MOVEMENTS  OF  POLYPES.  249 

tion  of  sensation.  There  would  appear  to  be  little  difference  in  the  character 
of  this  movement,  between  the  simple  Hydra  and  the  most  perfect  Vertebrated 
animal.  In  the  latter,  however,  another  set  of  muscles  are  superadded  to 
these,  for  the  purpose  of  preparing  the  aliment  by  mastication  for  the  opera- 
tion of  the  stomach,  and  of  bringing  it  within  reach  of  the  pharyngeal  con- 
striction.— But,  it  has  been  urged,  the  inactivity  of  the  tentacula  when  the 
Hydra  is  gorged  with  food,  proves  that  they  are  excited  to  action  by  the  will 
of  the  animal.  This  inference,  however,  may  be  easily  disproved.  The 
muscles  of  deglutition  in  Man  are  not  called  into  action  with  nearly  the  same 
readiness  and  energy,  when  the  stomach  is  distended,  as  when  it  is  empty;  a 
fact  of  which  any  one  may  convince  himself,  by  observing  the  relative  facility 
of  swallowing,  at  the  commencement  and  the  termination  of  a  full  meal.  No 
one  will  assert  that  this  variation  is  an  effect  of  the  will;  indeed,  it  is  often 
opposed  to  it;  being  one  of  those  beautiful  adaptations,  by  which  the  welfare 
of  the  economy  is  provided  for,  but  which  the  indulgence  of  the  sensual  appe- 
tites opposes.  Most  of  the  movements  of  this  animal,  and  of  others  of  the 
class,  appear  to  be  equally  the  result  of  external  stimuli,  with  that  already 
described;  and  it  is  only  in  a  few  instances,  principally  those  of  absolute 
locomotion  or  change  of  place,  that  any  evidence  of  voluntary  action  can  be 
discerned.  It  may  be  occasionally  remarked,  however,  that  one  or  more  of 
the  tentacula  are  retracted  or  extended,  without  the  slightest  appreciable 
change  in  any  of  those  external  circumstances,  which  seem  ordinarily  to 
affect  the  motions  of  the  animal ;  and  this  action  we  can  scarcely  regard  as 
otherwise  than  voluntary. 

314.  Thus  in  the   Nervous  System  of  Radiated  Animals,  we  have  an  in- 
stance of  that  community  of  function,  which  is  so  remarkable  in  the  organism 
of  the  lower  tribes,  when  contrasted  with  the  separation,  which  is  perceptible 
in  those  at  the  opposite  extremity  of  the  scale.     The  visceral  nerves  of  the 
Asterias   are  not  isolated  at  their  central  terminations  from  those  which  are 
connected  with  the  sensorial  and  locomotive  functions :  nor  are  the  nerves 
which  minister  to  the  instinctive  actions  separable  from  those  which  convey 
the  influence  of  the  will.     Every  segment  of  the  body  appears  equal  in  its 
character  and  endowments  to  the  remainder;  each  has  a  ganglion  appropriated 
to  it ;  and,  as  the  ganglia,  like  the  segments,  are  all  alike,  neither  of  them  can 
be  regarded  as  having  any  presiding  character. 

315.  From  the  Radiated  we  now  pass  to  the   MOLLUSCOUS  classes;   the 
general  character  of  which,  as  a  natural  group,  is  the   remarkable   predomi- 
nance of  the  Nutritive  system  over  that  of  Animal  life.     There  is  not  in  the 
Mollusca,  as  in  the  Radiata,  any  repetition  of  parts  around  a  common  centre; 
and  we  do  not  therefore   meet  in  them  with  a  number  of  ganglia,  nearly  or 
altogether  alike  in  endowments.     In  some  of  the  higher  species,  there  is  a 
conformity  between  the  two  sides  of  the  body,  or  a  lateral  symmetry ;  which 
involves  a  subdivision  of  some  of  the  ganglia,  that  are  single  in  the  inferior 
tribes,  into  two  masses,  which  always  remain  in  connexion  with  each  other. 
With  this  exception,  it  may  be  observed,  that  all  the  principal  ganglia,  to  the 
number  of  four  or  five,  which  we  meet  with  in  the  higher  Mollusca,  appear 
to  have  distinct  functions;  as  may  be  determined  by  tracing  the  distribution 
of  their  nerves.     Thus  we  find  a  pair  of  cephalic  ganglia,  situated  above  the 
03sophagus,  connected  with  the  organs  of  special  sensation,  and  sending  motor 
nerves  (as  we  shall  see  reason  to  believe)  to  all  parts  of  the  body.     This  is 
obviously  analogous  to  the  brain  of  Vertebrata.     Below  the  oesophagus  there 
is  generally  a  small  ganglion,  connected  with   the  apparatus  of  deglutition, 
which  may  be  called  the  stomato- gastric  ganglion.     In  connexion  with  the 
gills  we  have  always  one  ganglion,  sometimes  a  pair,  which  may  be  termed 
the  branchial  ganglion.     Another  is  found  at  the  base  of  the  foot,  which  may 


250  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

be  called  the  pedal  ganglion.  And  there  is  sometimes  another,  which  espe- 
cially supplies  the  mantle  with  nerves ;  and  this  may  be  called  the  palleal 
ganglion. — The  distribution  of  their  nerves  to  the  different  organs,  would 
alone  indicate  the  respective  functions  of  these  ganglia;  but  these  are  placed 
beyond  doubt,  by  that  very  great  variety  in  the  disposition  of  these  organs, 
which  is  characteristic  of  the  Mollusca.  The  development  of  the  sensory 
organs,  the  situation  of  the  gills,  the  structure  and  position  of  the  foot,  the 
conformation  and  uses  of  the  mantle,  are  well  known  to  differ  in  the  most 
obvious  manner,  in  genera  which  are  closely  allied  to  each  other.  Hence 
the  anatomist  is  enabled,  by  the  discovery  of  corresponding  changes  in  the 
nervous  system,  to  satisfy  himself  of  the  particular  functions  of  its  different 
centres.* 

316.  It  is  only  in  the  higher  tribes,  however,  that  this  separation  of  function 
is  evident ;  for  in  the  lowest,  we  find  the  Nervous  System  in  its  least  deve- 
loped form.     This  is  the  case  in  the  class  TUNICATA;  composed  of  animals, 
in  which  the  whole  body  is  enclosed  in  a  tunic  or  bag,  having  two  orifices, 
through  one  of  which  the  water  is  drawn  in  by  ciliary  action,  whilst  through 
the  other  it  is  expelled.     This  bag  incloses  a  large  chamber,  the  lining  of 
which  is  devoted  to  the  respiratory  function ;  and  at  the  bottom  of  it  lies  the 
mass  of  the  viscera,  on  which  is  the  entrance  to  the  stomach.     A  part  of  the 
water  which  is  taken  into  the  respiratory  chamber  flows  into  this,  and  passes 
through  the  intestinal  canal ;  being  discharged  along  with  that,  which  has 
only  served  the  purpose  of  aerating  the  blood.     These  animals  have  no  power 
of  motion,  but  such  as  is  effected  by  the  general  contraction  of  the  respiratory 
sac;  this  is  effected  by  a  single  ganglion  placed  between  its  orifices,  which  is 
therefore  chiefly  a  branchial  ganglion,  and  is  the  only  nervous  centre  they 
possess.     The   trunks   connected  with  it  send  branches  over  the  muscular 
envelope  of  the  respiratory  sac,  and  to  the  sphincters   which   surround  its 
orifices ;  whilst  other  branches  proceed  to  the  membrane  lining  the  orifices, 
and  especially  to  the  tentacula,  or  lips,  which  are  situated  at  the  oral  entrance. 
The  maintenance  of  the  regular  current  is  effected,  as  just  stated,  by  ciliary 
action ;  but  when  any  substance  is  being  drawn  in,  the  entrance  of  which 
would  be  injurious,  its  contact  with  the  tentacula  excites  a  general  contraction 
of  the  muscular  envelope,  and  causes  a  jet  of  water  to  issue  from  one  or  both 
orifices,  which  carries  the   offending  body  to  a  distance.     And,  in  the  same 
manner,  if  the  exterior  of  the  body  be  touched,  the  mantle  suddenly  and  vio- 
lently contracts,  and  expels  the  contents  of  the  sac. — These  are  the  chief,  if 
not  the  only  actions,  which  the  Nervous  System  of  these  animals  is  destined 
to  perform  ;  and  they  are  evidently  of  a  reflex  character ;  bearing  a  close 
correspondence  with  the  acts  of  coughing  and  sneezing  in  Man,  which  are  in 
like  manner  destined  to  expel  injurious  substances  from  the  respiratory  pas- 
sages.    By  the  contact  of  such  substances  with  the  tentacula  that  guard  the 
oral  orifice,  or  with  the  lining  of  the  respiratory  sac,  or  by  irritation  of  the 
external  surface  of  the  body,  an  impression  is  produced  on  the  afferent  fibres  ; 
which,  being  conveyed  to  the  central  ganglion,  excites  there  a  reflex  motor 
impulse ;  and  the  propagation  of  this  impulse  along  the  afferent  fibres,  to  the 
muscular  fibres   of  the   contractile  sac,  and  to  the  sphincters,  produces  the 
movements  in  question. 

317.  In  the  CONCHIFERA,  or  Mollusks  inhabiting  bivalve  shells,  there  are 
invariably  two  ganglia,  having  different  functions.     The  larger  of  these  (Fif 


124,  c),  corresponding  to  the  single  ganglion  of  the  Tunicata,  is  situated  towards 
the  posterior  end  of  the  body  (that  is,  the  end  most  distant  from  the  mouth), 

*  See  Mr.  Garner  on  the  Nervous  System  of  the  Mollusca,  in  the  Linnsean  Transactions, 
Vol.  xvn. 


NERVOUS  SYSTEM  OF  THE  LOWER  MOLLUSC  A. 


251 


Fig.  124. 


in  the  neighbourhood  of  the  posterior  adductor  muscle ;  and  its  branches  are 
distributed  to  that  muscle,  to  the  mantle,  to  the  gills,  and  to  the  siphons 
through  which  the  water  is  introduced 
and  carried  off.  But  we  find  another 
ganglion,  or  rather  pair  of  ganglia,  a, 
a,  situated  near  the  front  of  the  body, 
either  upon  the  resopliagus,  or  at  its 
sides ;  these  ganglia  are  connected 
with  the  very  sensitive  tentacula 
which  guard  the  mouth ;  and  they 
may  be  regarded  as  presenting  the 
first  approach,  both  in  position  and 
functions,  to  the  brain  of  higher  ani- 
mals. In  the  Oyster,  and  others  of 
the  lower  Conchifera  which  have  no 
foot, — which  is  a  muscular  tongue- 
like  organ,  —  we  find  an  additional 
ganglion  (b)  connected  with  it. — This 
is  the  case  in  the  Solen,  or  animal  of 
the  Razor-shell ;  whose  foot  is  a  very 
powerful  boring  instrument,  enabling 
it  to  penetrate  deeply  into  the  sand. 
Here,  then,  we  have  three  distinct 
kinds  of  ganglionic  centres ;  every  one 
of  which  may  be  doubled,  or  repeated 
on  the  two  sides  of  the  body.  First, 
the  cephalic  ganglia,  a,  a,  which  are 
probably  the  sole  instruments  of  sen- 
sation and  of  consensual  movements; 
as  well  as  of  whatever  voluntary 
power  the  animal  may  possess  :  these 
are  almost  invariably  double,  being 
connected  together  by  a  transverse 
band,  which  arches  over  the  oesopha- 
gus. Second,  the  pedal  ganglion,  b, 
which  is  usually  single,  in  conformity 
with  the  single  character  of  the  organ 
it  supplies ;  but  in  one  very  rare  Bi- 
valve Mollusk,  the  foot  is  double,  and 
the  pedal  ganglion  is  double  also. — 
Third,  the  respiratory  ganglion,  c, 
which  frequently  presents  a  form  that 
indicates  a  partial  division  into  two 
halves,  corresponding  with  the  repe- 
tition of  the  organs  it  supplies,  on  the 
two  sides  of  the  body.  Besides  these 
principal  centres,  we  meet  with  nu- 
merous smaller  ones  upon  the  nervous 
cords  (/,  /,  and  g,  g),  which  proceed  from  them  to  the  different  parts  of  the 
general  muscular  envelope  or  mantle. 

318.  Now  it  will  be  observed,  that  the  two  cephalic  ganglia  a,  a,  are  con- 
nected with  the  pedal  ganglion,  b,  by  means  of  a  pair  of  trunks,  e,  proceeding 
from  the  former  to  the  latter ;  and  that  they  are,  in  like  manner,  separately 
connected  with  the  respiratory  or  branchial  ganglion  c.  It  is  found,  upon 


Nervous  system  of  Solen;  a,  a,  cephalic  ganglia, 
connected  by  a  transverse  band  passing  over  the 
oesophagus;  6,  pedal  ganglion,  the  branches  of 
which  are  distributed  to  the  powerful  muscular 
foot;  c,  branchial  ganglion,  the  branches  of  which 
proceed  to  the  gills  g,  the  siphons  i,  t,  and  other 
parts  ;  A,  anus  :  e,  trunks  connecting  cephalic  and 
branchial  ganglia;  /-/././,  minute  ganglia  on  the 
branches  distributed  to  the  mantle. 


252  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

careful  dissection,  that  these  cords  do  not  serve  merely  to  bring  the  ganglia 
into  relation ;  but  that  a  part  of  them  pass  through  the  ganglion  into  the  trunks 
proceeding  from  it.  Thus,  of  the  nerves  which  supply  the  large  fleshy  foot, 
and  which  appear  to  proceed  from  the  pedal  ganglion,  6,  a  part  are  undoubt- 
edly connected  with  that  ganglion  alone,  coming  into  relation  with  its  vesicu- 
lar substance  ;  but  a  part  also  pass  on  to  the  cephalic  ganglia,  by  the  connecting 
trunks, — so  that  these,  rather  than  the  pedal  ganglion,  constitute  their  centre. 
The  same  may  be  said  of  the  nerves  proceeding  from  the  branchial  ganglion : 
a  portion  of  them  having  their  centre  in  the  vesicular  matter  of  that  ganglion ; 
whilst  another  portion  has  no  relation  to  it  whatever  (beyond  that  of  prox- 
imity), but  passes  through  or  over  it,  to  become  connected  with  the  cephalic 
ganglia.  There  is  good  reason  to  believe,  that  the  pedal  and  branchial  gan- 
glia minister  to  the  purely  reflex  actions  of  the  organs  they  respectively  sup- 
ply; and  that  they  would  serve  this  purpose  as  well,  if  altogether  cut  off  from 
connection  with  the  cephalic  ganglia :  whilst  the  latter,  being  the  instruments 
of  the  actions  which  are  called  forth  by  sensation  (whether  these  be  of  a  con- 
sensual or  of  a  voluntary  nature),  exert  a  general  control  ancT  direction  over 
the  movements  of  the  animal. 

319.  The  animals  of  the  class  GASTEROPODA,  whether  furnished  with  uni- 
valve shells,  or  entirely  destitute  of  such  protection,  are,  for  the  most  part, 
much  more  highly  organized  than  the  preceding;  possessing  not  merely 
greater  locomotive  power,  but  organs  of  special  sense,  which  are  situated  in 
the  neighbourhood  of  the  mouth,  upon  a  projecting  part  of  the  body,  which  is 
thus  constituted  a  head.  Their  nervous  system  consists  of  at  least  three  dis- 
tinct centres ;  the  relative  position  of  which  varies  with  that  of  the  organs 
supplied  by  them.  The  anterior  or  cephalic  ganglia  are  larger  in  proportion 
to  the  rest,  than  they  are  in  the  Conchifera  ;  and  they  exhibit  a  tendency  to 
gain  a  position  anterior  to  the  oesophagus,  and  to  approximate  towards  each 
other,  so  as  to  meet  and  form  a  single  ganglionic  mass  on  the  median  line. 
The  branchial  ganglion  is  constantly  to  be  met  with ;  but  its  position  is  ex- 
tremely variable.  This  centre,  however,  always  bears  a  close  relation  with 
the  gills,  both  in  situation  and  in  degree  of  development ;  and  even  where 
conjoined,  as  it  frequently  is,  with  the  pedal  ganglion,  it  may  be  distinguished 
from  it  by  the  distribution  of  its  nerves,  as  well  as  by  its  separate  connection 
with  the  cephalic  ganglia,  which  is  always  noticed  in  such  cases.  This  may 
be  observed  in  the  Patella  (limpet)  and  Limax  (slug).  Sometimes  the  func- 
tions of  this  ganglion  are  subdivided  between  two ;  of  which  one  is  still  ap- 
propriated to  the  branchiae ;  whilst  the  other  is  connected  with  the  general 
surface  of  the  mantle,  and  with  the  respiratory  passages  which  are  prolonga- 
tions of  it,  and  hence  may  be  called  the  palleal  ganglion.  The  position  of 
the  pedal  ganglion  (which  is  generally  double  in  the  Gasteropoda,  though  the 
foot  is  single),  also  varies,  but  in  a  less  degree,  since  it  is  generally  in  the 
neighbourhood  of  the  head. — Besides  these  nervous  centres,  we  find,  in  many 
of  the  Gasteropoda,  a  separate  system  connected  with  a  very  important  set 
of  organs,  the  gustatory  and  manducatory,  which  are  but  slightly  shadowed 
out  among  the  Conchifera.  In  these  higher  tribes,  the  oesophagus  is  dilated 
at  its  commencement  into  a  muscular  cavity  (Fig.  3,  a);  containing  a  curious 
rasp-like  tongue,  often  supported  upon  cartilages,  which  serves  to  reduce  the 
food;  and  sometimes  furnished  with  horny  maxillae.  The  nerves  which  sup- 
ply these  do  not  proceed  directly  from  the  cephalic  ganglia,  but  from  a  dis- 
tinct centre;  and  their  ramifications  proceed  along  the  oesophagus  and  sto- 
mach, and  are  occasionally  connected  with  the  other  nerves  by  inosculating 
filaments.  This  set  of  ganglia  and  nerves,  which  is  even  more  important 
from  its  relative  development  in  some  other  classes,  and  into  the  analogies  of 


NERVOUS  SYSTEM  OF  HIGHER  MOLLUSCA.  253 

which  in  the  nervous  system  of  Vertebrata  we  shall  hereafter  inquire,  may  be 
called,  from  its  distribution,  the  stomato- gastric  system. 

320.  The  ganglia  first  described  may  be  regarded  as  corresponding  with 
those  parts  of  the  nervous  centres  in  the  Vertebrata,  the  distribution  of  whose 
nerves  is  analogous.     Thus  the  branchial  ganglion  obviously  corresponds 
with  that  portion  of  the  Medulla  Oblongata  which  is  the  centre  of  their  respi- 
ratory actions  ;  and  the  pedal  ganglion  is  analogous  to  that  division  of  the 
Spinal  Cord  from  which  the  nerves  of  the  anterior  or  posterior  extremities 
pass  off.     It  is  well  known  that  such  portions  of  the  spinal  cord  may  be  com- 
pletely isolated,  without  destroying  the  functions  to  which  they  minister. 
Thus,  the  brain  and  lower  part  of  the  spinal  cord  may  be  removed, — that 
portion  only  of  the  cerebro-spinal  axis  being  left,  which  is  connected  with  the 
principal  respiratory  nerves,  in  fact  the  respiratory  ganglion, — and  yet  the 
animal  may  continue  to  exist  for  some  time.     It  is  then  reduced  to  a  condi- 
tion similar  to  that  of  the  Tunicata;  whose  single  ganglion,  though  combining 
in  some  degree  the   functions  of  those  which  exist  separately  in  the   higher 
tribes,  has  evidently  the  regulation  of  the  respiratory  movements  for  its  chief 
object.     In  the  same  manner,  the  integrity  of  the  segment  of  the  cord,  with 
which  the  nerves  of  the  extremities  are  connected,  will  enable  them  to  execute 
those  movements  of  a  reflex  character,  which  depend  upon  its  power  as  their 
centre;  even  though  it  be  isolated  from  every  other  part  of  the  nervous  ap- 
paratus.— The  cephalic  ganglia  must  be  regarded  as  chiefly  analogous  to  those 
portions  of  the  Encephalon  of  Vertebrata,  which   are  immediately  connected 
with  the  nerves  of  sense.     We  find  nerves  of  special  sensation  proceeding 
from  them,  certainly  to   eyes   and  an   auditory  apparatus,  perhaps  also   to 
olfactive  organs  ;  as  well  as  others  of  common  sensation,  supplying  the  ten- 
tacula  and  mouth.     Hence  we  must  admit,  that  they  perform  the  functions  of 
the  optic  ganglia  of  Vertebrata,  and  perhaps  also  of  the  olfactory  lobes  ;  as 
well  as  of  the  portion  of  the  medulla  oblongata,  in  which  the  sensory  portion 
of  the  fifth  pair  terminates.     Moreover,  they  certainly  give   origin  also  to 
motor  nerves  ;  and  must  thus  perform  the  functions  of  the  Medulla  Oblongata, 
from  which  the  corresponding  nerves  arise  in  Vertebrata  ;  as  well  as,  perhaps, 
of  the  Cerebellum. — It  is  obvious  that  the  portion  of  the  Nervous  system  of 
the  Gasteropod  Mollusca,  into  the  analogies  of  which  we  have  thus  inquired, 
cannot  in  the  least  be  compared  as  a  whole  with  the  Sympathetic  system  of 
the  Vertebrata,  which  it  was  formerly  imagined  to  resemble.     The  distribu- 
tion of  some  of  its  nerves  to  the  viscera,  however,  may  indicate  that  it  partly 
performs  the   functions  of  that  system;  with  which  it  is  structurally  inter- 
mixed, even   in  Vertebrata.     But  the  stomato-gastric  system  may,  perhaps, 
with  more  probability,  be  considered  as  executing  its  offices.     Into  the  pecu- 
liar character  of  that  system  we  shall  be  more  competent  to  inquire  when  we 
have  traced  it  through  other  classes  of  Invertebrata. 

321.  Having  thus  separately  considered  the  nervous  centres  of  the  Gaste- 
ropoda, and  determined  their  special  functions  by  their  structural  relations,  we 
shall  inquire  into  the  mode  in  which  these  functions  are  combined,  so  as  to 
enable  them  to  act  in  harmony.     This  is  an  inquiry  of  much  interest,  in  re- 
ference to  the  determination  of  the  offices  of  the  different  parts  of  the  nervous 
centres  in  Articulated  and  Vertebrated  animals.     If  we  examine  the  mode  in 
which  the  different  ganglia  are  united  by  connecting  trunks,  we  are  led  to  per- 
ceive the  important  fact,  that,  while  they  have  little  or  no  communication  with 
each  other,  they  are  all  directly  connected  with  the  cephalic  ganglia ;  which 
seem  thus  to  harmonize  and  control  their  individual  actions.     Frequently  a 
communication  with  one  another  appears  to  exist,  where  there  is  really  none. 
Thus,  in  the  Jlplysia,^.  cord  passes  from  the  branchial  ganglion  (Fig.  125,  D), 

22 


254 


FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 


Fig.  125. 


which  is  situated  in  the  posterior  part  of  the  body,  to  the  pedal  ganglion  of 
each  side,  (c,  c).     Where  such  is  the  case,  the  trunk  is  not  united  with  that 

proceeding  from  the  ganglion  through 
which  it  passes  ;  but  the  two  remain 
distinct,  though  running  in  the  same 
direction.  Moreover,  the  double  func- 
tion of  a  ganglion  may  be  sometimes 
recognized,  by  its  being  connected 
with  the  cephalic  mass  by  a  double 
trunk.  Thus,  in  the  Aplysia,  that 
which  has  been  termed  the  pedal  gan- 
glion is  really  made  up  of  a  pedal  and 
palleal  ganglion,  as  is  proved  by  the 
distribution  of  its  branches;  and  in 
conformity  with  this  double  function, 
we  find  it  communicating  with  the 
cephalic  mass  by  two  cords,  besides 
the  one  which  has  been  just  mentioned 
as  passing  through  it,  and  which  ap- 
pears as  a  third.  In  the  Bullsea, 
whose  nervous  system  is  disposed  on 
the  same  general  plan,  the  pedal  and 
palleal  ganglia  are  separately  connected 
with  the  cephalic  ;  the  cord  from  the 
branchial  ganglion  passing  through  the 
palleal. 

322.  Further,  a  careful  examination 
of  these  ganglia,  and  of  their  connecting 
cords,  discloses  this  important  fact, 
which  is  peculiarly  evident  in  the  case 
of  the  pedal  ganglia  —  that  the  cords 
proceeding  from  the  cephalic  mass  do 
not  lose  themselves  in  the  grey  matter 
of  these  ganglia;  but  divide  themselves 
into  filaments,  which  mix  with  those 
proceeding  from  them,  to  form  the 

nervOUS  trunks  which  they  distribute. 

Ttfe  can  scarcely,  then,  fail  to  infer, 

h        h  ,   j  ^ngUon,  with  the  nerv- 

,.,     .,  6     »*      * 

OUS  fibnls  proceeding  from  itself,  IS  the 

SOUTCe  of  the  reflex  actions  of  this  Or- 
gan;  whilst  the  filaments  whichare  con- 

tinuous with  those  of  the  connecting 


Nervous  system  of  Aplysia.    A,  pharyngeal  gan- 

giion;  B,  cephalic  ganglion.  The  cephalic  is  con- 

nected,  by  three  distinct  cords  on  each  side,  with 
the  lateral  masses,  c  c,  which  combine  the  functions 
of  pedal  and  palleal  ganglia;  these  are  united  with 
each  other  by  two  transverse  bands,  between  which 
the  aorta  passes.  From  the  lateral  ganglia,  a  con- 
necting  cord  passes  backwards  on  each  side  to  the 


with  the  nucleus  of  the  cephalic  gang- 
lia, are  the  channels  of  sensory  impres- 
sions, and  of  the  motor  impulses  prompted  by  them.  —  This  is  well  illustrated 
in  the  curious  disposition  of  parts,  which  we  find  in  the  arms  of  the  Cuttle-fish. 
These  are  provided,  it  is  well  known,  with  a  series  of  suckers,  which  are  to 
the  animal  important  instruments  of  locomotion  and  prehension.  It  has  been 
observed  by  Dr.  Sharpey,  that  the  nerves  which  supply  these  arms  are  fur- 
nished with  ganglionic  enlargements,  of  which  one  corresponds  with  each 
sucker;  and  that  each  trunk  consists  of  two  tracts,  in  one  of  which  the  gan- 
glionic enlargements  exist;  whilst  the  other  passes  continuously  over  these, 
but  sends  off  nervous  filaments,  which  help  to  form  the  branches  going  to  the 


NERVOUS  SYSTEM  OF  MOLLUSCA  AND  ARTICTJLATA.  255 

several  suckers.  When  the  animal  endeavours  to  embrace  any  object  firmly 
with  its  arm,  it  brings  all  the  suckers  simultaneously  to  bear  upon  it.  There 
can  be  little  doubt  that  this  action  is  occasioned  by  a  motor  impulse,  propa- 
gated from  the  cephalic  masses  by  the  non-ganglionic  portion  of  the  cord, 
which  supplies  all  the  suckers  alike.  On  the  other  hand,  any  individual 
sucker  may  be  made  to  attach  itself,  by  placing  a  substance  in  contact  with 
it  alone ;  this  action  is  independent  of  the  cephalic  ganglia,  as  is  evident  from 
the  fact,  that  it  will  take  place  when  the  arm  is  severed  from  the  body,  or  even 
in  a  small  piece  of  the  arm,  if  recently  separated;  and  it  can  scarcely  be  doubted, 
that  it  is  due  to  the  reflection  of  the  impression  made  upon  the  sucker,  through 
the  small  ganglion  in  its  own  neighbourhood,  where  it  excites  a  motor  impulse. 
The  operation  of  these  independent  centres  appears,  in  the  entire  living  animal, 
to  be  controlled,  directed,  and  combined,  by  the  cephalic  ganglia ;  through  the 
medium  of  the  fibrous  band  which  passes  over  them,  and  which  mixes  its 
branches  with  theirs.  A  very  similar  arrangement  will  be  presently  shown 
to  exist  in  the  double  nervous  column  of  the  Articulata. 

323.  Upon  reviewing  all  the  anatomical  facts  hitherto  stated,  it  will  be  per- 
ceived that  ganglionic  masses,  characterized  by  nuclei  of  grey  matter,  or  of 
something  equivalent  to  it,  seem  to  exist,  wherever  it  is  desirable  that  impres- 
sions made  upon  the  afferent  nerves  should  excite  motions  ;  and  that,  as  we 
rise  dn  the  scale,  there  is  an  increase  in  the  number  of  centres  possessing  a 
diversity  of  functions.     We  have  seen  that  sometimes  these  centres  are,  for 
the  sake  of  convenient  disposition,  united  into  one  mass ;  whilst  on  the  other 
hand,  when  the  organs  are  multiplied,  they  also  are  repeated  to  a  like  extent ; 
especially  when  it  is  desirable  that  they  should  be  able  to  act  independently 
of  one  another,  as  in  the  case  of  the  suckers  of  the  Cuttle-fish.     It  may  further 
be  remarked,  that  wherever  the  presence  of  special  sensory  organs,  confined 
to  one  part  of  the  body,  gives  to  that  part  a  predominance  over  the  remainder 
(the  entrance  to  the  alimentary  canal  being  always  in  this  neighbourhood),  we 
find  the  ganglia  with  which  they  are  connected  possessing  a  special  relation 
with  all  the  rest,  which  these  do  not  possess  with  each  other.     It  is  obvious 
that,  where  visual  organs  are  developed,  the  impressions  made  upon  these  will 
determine  the  movements  of  the  animal,  more  than  those  of  any  other  kind ; 
and  it  would  seem  to  be  chiefly  owing  to  the  information  they  communicate, 
that  the  cephalic  ganglion  has  such  an  evident  presiding  influence  over  the  rest, 
even  when  smaller  than  any  of  them.     This   is,  however,  more  the  case  in 
animals  whose  movements  are  rapid,  and  in  which,  therefore,  the  perception 
of  distant  objects  is  more  important — as  in  the  Insect  tribes.     Except  in  the 
Cephalopoda,  the  subservience  of  the  nervous  system  to  the  nutritive  functions 
of  the  Mollusca  is  so  great  that  it  might  almost  be  regarded  as  an  appendage  to 
the  digestive  organs,  destined  for  the  selection  and  prehension  of  aliment. 
But  in  the  more  active  members  of  that  class  it  derives  a  more  elevated  cha- 
racter, from  the  development  of  organs  of  special  sensation  and  of  active  loco- 
motion. 

324.  The  animals  composing  the  group  ARTICULATA  all  present,  in  a  more 
or  less  evident  degree,  a  division  into  segments,  which  have  an  obvious  tend- 
ency to  resemble  one  another,  as  in  the  Radiata ;  these  are  disposed,  however, 
not  in  a  circle,  as  in  the  Radiata,  but  in  a  continuous  line.     In  those  in  which 
these  segments  differ  but  little  (as  in  the  Centipede,  or  the  Caterpillar  of  the 
Insect),  the  nervous  system  is  a  repetition  of  similar  parts ;  the  most  anterior 
of  the  ganglia,  however,  has   an    evident  predominating  influence  over  the 
rest,  for  the  reason  just  specified ;  and  this  influence  will  be  found,  by  com- 
parison in  other  classes,  to  diminish  with  the  loss*  and  to  increase  with  the  de- 
velopment, of  the  faculties  of  special  sensation,  which  have  their  seat  there. 
The  locomotive  power's  are  just  as  predominant  in  the  Articulated  series,  as 


256 


FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 


Fig.  126. 


Nervous  System  of  Larva  of  Sphinx  Ugus. 


distances  ;  the  last  is  formed  by  the  consoli- 
dation of  the  llth  and  12th. 


are  the  nutritive  functions  among  the  Mol- 
lusca.  Accordingly,  we  find  the  deve- 
lopment of  the  Nervous  system  to  bear  a 
special  reference  to  them  ;  and  the  sensori- 
motor  divisions  of  it  can  be  more  distinctly 
separated,  than  in  the  Mollusca,  from  the 
portion  which  ministers  to  the  organic  func- 
tions. 

325.  The  general   arrangement   of  the 
Nervous  System  differs  so  little,  except  as 
to  the  degree  of  concentration  of  the  ganglia, 
in  the  different  classes  of  this  sub-king- 
dom, that  it  is  of  little  consequence  what 
example  we  select.     It  will  be  convenient 
to  take  for  illustration  that  of  the  Larva  of 
the  Sphinx  ligustri,  or  Privet  Hawk-Moth, 
which  has  been  minutely  described  by  Mr. 
Newport.     Here  we   observe  a  chain  of 
ganglia  running  from  one  extremity  of  the 
body  to  the  other,  along  the  ventral  sur- 
face, and  in  the  median  line.     These  gan- 
glia are  connected   by  trunks,  which,  on 
close  examination,  are  seen  to  consist  of 
two  cords  closely  united.     The  cephalic 
ganglion  is  bilobed ;    evidently  consisting 
of  two  masses,  which  are  united  on  the 
median  line.  These  receive  the  nerves  of  the 
eyes  and  antennae ;  but  they  are  still  of  small 
size,  in  accordance  with  the  low  develop- 
ment of  the  sensory  organs.     The  ganglia 
of  the  longitudinal  cord  are  nearly  equal 
from  one  extremity  of  the  body  to  the 
other.     Each  sends  off  nerves   to  its  re- 
spective segments  ;  and  the  branches  pro- 
ceeding from   the    different   ganglia   have 
little  communication  with  each  other.  The 
highest  of  them,  situated  just  beneath  the 
oesophagus,  is  connected  with  the  cephalic 
masses  by  two  cords  ;  between  which  that 
canal  passes,  encircled,  as  it  were,  in  a  ring. 

326.  The  most  detailed  account  of  the 
conformation  of  the  Nervous  Centres  in 
the  Articulata,  is  that   recently  given  by 
Mr.  Newport,  in  regard  to  the  lulus,  and 
other    animals  of  the  class    MYRIAPODA.* 
Their   general    arrangement   corresponds 
with  that  which  has  been  just  described 
in  the  Iarva3  of  the  Sphinx  ligustri ;  but 
the  number  of  ganglia  is  much  greater.  In 
each  lateral  half  of  the  cord,  two  distinct 
tracts  or  layers  of  fibres  can  be  detected : 
of  these,  one — known  as  the  fibrous  tract 
— is  continuous  with  the 

*  Philosophical  Transactions,  1843. 


NERVOUS  SYSTEM  OF  ARTICULATA. 


257 


Portion  of  the  gang]  ionic  tract  of  Po- 
lydesmus  maculalus  ;  b,  inter-ganglionic 
cord ;  c,  anterior  nerves ;  d,  posterior 
nerves;  /,  &,  fibres  of  reinforcement; 
g-,  h,  commissural  fibres  ;  i,  longitudinal 
fibres,  softened  and  enlarged,  as  they 
pass  through  ganglionic  matter. 


and  contains  no  vesicular  matter  ;  whilst  the  other  known  as  the  ganglionic 
tract — has  vesicular  matter  deposited  at  intervals  amongst  its  fibres,  some  of 
which  are  continuous  with  the  brain,  whilst  others  do  not  reach  it.  (Fig.  128, 
A.)  Every  nerve  that  is  given  off  from  this  ventral  column,  is  connected  with 
both  tracts  ;  and  thus  it  has  two  sets  of  roots,  one  proceeding  to  the  brain,  the 
other  entering  the  ganglion  near  which  it  arises.  Of  this  last  division,  a  part 
crosses  to  the  opposite  side,  forming  the 
commissural  fibres  which  unite  together  the 
lateral  halves  of  the  cord  ;  whilst  another 
bundle  of  fibres  runs  along  the  side  of  the 
ganglionic  tract,  for  a  greater  or  less  propor- 
tion of  its  length,  and  then  emerges  again 
forming  part  of  another  nervous  trunk.  In 
Fig.  127  is  seen  Mr.  N.'s  representation  of 
one  of  the  ventral  ganglia,  and  part  of  the 
cord,  of  Polydesmus  maculalus;  showing 
the  longitudinal  and  commissural  fibres,  to- 
gether with  those  to  which  he  has  given  the 
name  of  fibres  of  reinforcement.  These 
lateral  fibres,  which  do  not  pass  on  to  the 
brain,  but  issue  again  from  the  ventral  cord 
at  a  point  a  little  distant  from  their  entrance, 
seem  to  be  more  numerous  in  the  hinder  part 
of  the  body  of  the  Centipede  tribe,  than  in 
its  front  portion  :  and  thus  it  is,  that  the  whole 
size  of  the  cord  remains  nearly  the  same 
along  its  entire  length ;  whilst  that  of  the  por- 
tion which  passes  backwards  from  the  brain,  must  be  continually  diminishing, 
as  it  gives  off'  fibres  to  the  nerves. 

327.  After  what  has  been  said  of  the  offices  which  the  ganglia  perform  in 
the  Mollusca,  and  of  the  relation  which  they  bear  to  the  cephalic  mass,  we 
shall  have  little  difficulty  in  understanding  the  character  of  the  nervous  appa- 
ratus in  the  Articulata,  if  our  minds  be  unoccupied  by  any  preconceived 
notion.  When  we  examine  into  the  actions  of  the  ventral  cord,  we  perceive 
that  those  of  all  its  ganglia  are  similar  to  each  other;  being  related  only  to 
the  movements  of  their  respective  segments,  and  of  the  members  which  belong 
to  them.  In  fact,  these  ganglia  may  be  regarded  as  so  many  repetitions  of 
the  pedal  or  locomotive  ganglion  of  the  Mollusca.  It  is  easily  proved,  that 
the  movements  of  each  pair  of  feet  may  be  produced  by  that  ganglion  alone, 
with  which  it  is  connected ;  since  a  single  segment,  isolated  from  the  rest, 
will  continue  to  perform  these  movements  for  some  time,  under  favourable 
circumstances.  But  it  is  evident  that  they  must  be  placed,  in  the  living  ani- 
mal, under  some  general  control ;  by  which  the  consentaneousness  of  action, 
that  is  essential  to  regular  locomotion,  may  be  produced.  This  is  proved  by 
the  experiments  to  be  presently  quoted.  We  can  scarcely  account  for  the 
exercise  of  such  a  general  control,  otherwise  than  by  attributing  it  to  the 
fibrous  portion  of  the  cord,*  which  directly  connects  each  of  the  nervous 

*  It  is  believed  by  Mr.  Newport,  that  the  fibrous  portion  of  the  ganglionic  tract,  which  lies 
nearest  the  surface  of  the  body,  may  be  the  channel  by  which  sensory  impressions  are  con- 
veyed to  the  brain;  whilst  the  fibrous  tract  itself  may  convey  downwards  the  motor  impulses 
which  originate  in  the  cephalic  ganglia.  The  chief  reason  for  this  supposition,  is  the  corre- 
spondence in  position, — relatively  to  each  other,  and  to  the  rest  of  the  body, — between  the 
fibrous  and  ganglionic  columns  in  Articulata,  and  the  portions  of  the  Spinal  Cord  of  Verte- 
tebrata,  from  which  the  anterior  or  motor  roots,  and  the  posterior  or  sensory,  respectively 
arise. — But  the  fibres  which  are  peculiar  to  the  ganglionic  tract,  obviously  form  a  distinct 
system. 

22* 


258  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

trunks  with  the  cephalic  ganglia,  as  in  the  Mollusca;  and  this  must,  there- 
fore, conduct  to  the  sensorium  (whose  seat  is  probably  in  the  latter)  the  im- 
pressions which  there  produce  sensations,  and  must  convey  downwards  the 
locomotive  impulse;  whilst  the  ganglion  of  each  segment,  with  the  filaments 
connected  with  its  nucleus,  will  form  the  circle  necessary  for  the  simply- 
reflex  actions  of  its  members.  The  independence  of  the  segments  of  the 
Articulata,  as  far  as  their  reflex  actions  are  concerned,  and  their  common  sub- 
ordination to  one  presiding  centre  of  the  will,  are  fully  explained  on  this  sup- 
position. It  is  also  quite  conformable  to  the  analogy,  both  of  Mollusca,  and 
of  Vertebrata. 

328.  The  number  and  variety  of  the  reflex  actions,  which  take  place  in  the 
Articulata  after  decapitation,  are  very  remarkable ;  and  they  seem  to  have  a 
consentaneousness,  proportioned  to  the  closeness  of  the  relation  between  the 
nervous  centres  in  the  respective  species.     Thus,  in  the  Centipede,  we  find 
the  ganglia  of  the  several  segments  distinct,  but  connected  by  a  commissural 
trunk.     Here  an  impression  made  equally  upon  the  afferent  nerves  of  all  the 
ganglia,  will  produce  a  consentaneous  action.     Thus,  if  the  respiratory  ori- 
fices on  one  side  of  a  decapitated  Centipede  be  exposed  to  an  irritating  vapour, 
the  body  will  be  immediately  flexed  in  the  opposite  direction ;  and  if  the 
stigmata  of  the  other  side  be  then  similarly  irritated,  a  contrary  movement 
will  occur.     But  different  actions   may  be  excited  in  different  parts  of  the 
cord,  by  the  proper  disposition  of  the  irritating  cause.     In  the  higher  classes, 
however,  where  the  ganglia  of  the  locomotive  organs  are  much  concentrated, 
the  same  irritation  will  produce  consentaneous  motions  in  several  members, 
similar  to   those  which  the   unmutilated  animal  performs.     In  the  Mantis 
religiosa,  for  example, — which  ordinarily  places  itself  in  a  very  curious 
position,  especially  when  threatened  or  attacked,  resting  upon  its  two  pos- 
terior pairs  of  legs,  and  elevating  its  thorax  with  the  anterior  pair,  which  are 
armed  with  powerful  claws, — if  the  anterior  segment  of  the  thorax,  with  its 
attached  members,  be  removed,  the  posterior  part  of  the  body  will  still  remain 
balanced  upon  the  four  legs  which  belong  to  it,  resisting  any  attempts  to  over- 
throw it,  recovering  its  position  when   disturbed,  and  performing  the  same 
agitated  movements  of  the  wings  and  elytra,  as  when  the  unmutilated  animal 
is  irritated:  on  the  other  hand,  the  detached  portion  of  the  thorax,  which  con- 
tains a  ganglion,  will,  when  separated  from  the  head,  set  in  motion  its  long 
arms,  and  impress   their  hooks  on  the  fingers  which  hold  it.     These  facts 
prove  unequivocally,  that  the  combined  automatic  movements  of  these  parts, 
which  are  performed  in  direct  respondence  to  external  expressions,  are  only 
dependent  for  their  stimulation  upon  that  ganglionic  centre,  with  which  the 
nerves  that  excite  them  are  immediately  connected.     Another  instance,  related 
by  Burmeister,  is   still  more  satisfactory  in  regard  to  the   manner  in  which 
these  movements  are  excited.     A  specimen  of  the  Dytiscus  Sulcatus,  from 
which   the   cephalic  ganglia  had  been  removed,  and  which  remained  in  a 
motionless   condition  whilst  lying  with  its   abdomen  on  a  dry  hard  surface, 
executed  the  usual  swimming  motions,   when  cast  into  water,   with  great 
energy  and  rapidity,  striking  all  its  comrades  to  one  side  by  its  violence,  and 
persisting  in  this  for  half  an  hour. 

329.  These  conclusions  are  also  fully  confirmed  by  the  experiments  of 
Mr.  Newport,  upon  various  Insects   and   Myriapoda;  the  results  of  which 
have  been  recently  made  public.*     The  following,  upon  the  lulus  terrestris, 
is  particularly  interesting.     "  The  cord  was   divided  in  the   fourteenth,  and 
also  the  twentieth  segment;  and  the  intervening  portion  was   destroyed,  by 
breaking  it  down  with  a  needle.     The  animal  exhibited  in  the  anterior  part 

*  Philos.  Trans.,  1843,  p.  267. 


REFLEX  ACTIONS  OF  ARTICULATA. 


259 


of  its  body  all  the  evidences  of  perfect  volition.  It  moved  actively  along, 
turning  itself  back  on  either  side  repeatedly,  as  if  to  examine  the  anterior 
wounded  portion,  which  it  felt  again  and  again  with  its  antennae:  and  when 
attempting  to  escape,  frequently  turned  back  as  if  in  pain  and  aware  of  some 
hindrance  to  its  movements ;  but  it  seemed  perfectly  unconscious  of  the 
existence  of  the  posterior  part  of  its  body,  behind  the  first  incision.  In  those 
segments,  in  which  the  cord  was  destroyed,  the  legs  were  motionless ;  while 
those  of  the  posterior  division,  behind  the  second  incision,  were  in  constant 
but  involuntary  motion,  the  movements  being  similar  to  those  of  walking  or 
running,  uniformly  continued,  but  without  any  consentaneous  action  with 
those  of  the  anterior  part,  by  which  locomotion  was  performed,  dragging  the 
posterior  divisions  of  the  body  after  them.  When  the  animal  was  held  by 
the  posterior  segments,  reflex  actions  were  excited  in  the  legs,  and  powerful 
contractions  and  gyrations  of  the  whole  animal  were  performed  in  those  seg- 
ments ;  but  these  movements  appeared  to  be  entirely  the  result  of  reflex 
actions  of  the  muscles,  since  exactly  similar  ones  took  place  in  the  whole 
body  of  decapitated  specimens.  At  the  expiration  of  twelve  hours,  the  most 
perfectly  voluntary  acts  were  performed  by  the  head  and  anterior  division  of 

Fig.  128. 


Parts  of  Xervous  System  of  Articulata.  A,  single  ganglion  of  Centipede,  much  enlarged,  showing  the 
distinctness  of  the  purely  fibrous  tract,  6,  from  the  ganglionic  column,  a.  B,  portion  of  the  double  cord 
from  thorax  of  Pupa  of  Sphinx  ligustri,  showing  the  respiratory  ganglia  and  nerves,  between  the  gan- 
glia (2,  3,  4),  and  the  separated  cords  of  the  symmetrical  system,  c,  view  of  two  systems  combined, 
showing  their  arrangement  in  the  Larva;  a,  ganglion  of  venial  column  ;  6,  fibrous  tract  passing  over 
it;  c  c,  respiratory  system  of  nerves  distinct  from  both. 

the  body,  such  as  locomotion  forwards  or  to  either  side,  avoidance  of  any 
obstacle,  touching  it  with  the  antennae,  (which  were  in  rapid  action,  as  in  an 
uninjured  animal,)  and  attempting  to  reach  and  to  climb  up  an  object  pre- 


260  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

sented  to  it,  but  not  in  immediate  contact  with  it.  But  reflex  movements 
alone  existed  in  the  posterior  division,  in  which  the  legs  were  very  slowly 
moved,  even  when  the  animal  was  not  progressing.  Brisk  actions  were  now 
more  easily  excited  in  them  than  at  first,  either  by  contact  with  the  segments, 
by  irritation  of  one  or  two  of  the  legs  themselves,  or  by  a  sudden  current  of 
air.  By  these  means,  when  the  animal  was  lying  still,  actions  were  imme- 
diately excited  in  all  the  legs  of  the  posterior  parts  of  the  body,  anterior  and 
posterior  to  those  which  were  irritated ;  and  these  actions  were  induced  in 
those  of  both  sides  of  the  body,  but  appeared  to  commence  on  the  opposite 
side,  in  the  legs  corresponding  to  those  which  were  first  irritated.  In  eighteen 
hours,  the  anterior  part  of  the  body  was  quite  dead,  so  that  no  motions  what- 
ever could  be  excited  in  it,  either  voluntary  or  reflex;  but  reflex  actions  were 
then  readily  excited  in  the  posterior,  and  also  slightly  so  by  mechanical  irrita- 
tion, even  at  twenty-four  hours."  It  would  appear,  then,  that  we  may  obtain 
more  decided  proof,  in  the  Articulated  series,  of  the  real  character  of  reflex 
actions,  and  of  their  dependence  upon  a  distinct  system  of  nerves,  than  we 
can  draw  from  any  other  class  of  animals.  In  the  Vertebrata,  it  is  easy  to 
distinguish  the  sensory  from  the  motor — the  afferent  from  the  efferent — 
fibres;  but  the  distinctness  of  the  excito-motor  system  from  the  sensori-voli- 
tional,  is  not  so  clearly  made  out.  Here,  however,  the  afferent  and  efferent 
fibres  cannot'be  readily  distinguished;  but  it  is  obvious  that  the  reflex  actions, 
which  manifest  themselves  when  the  communication  with  the  cephalic  ganglia 
is  cut  off,  are  to  be  attributed  to  those  fibres,  which  enter  the  cord  under  the 
afferent  character, — pass  into  the  edge  of  the  ganglion  as  ihe  fibres  of  rein- 
forcement, or  cross  it  as  commissural  fibres, — and  then  emerge  again  as 
efferent  fibres,  either  in  the  nerves  of  the  same  segment,  or  in  those  of  another 
more  or  less  distant.  By  traversing  the  cord  along  a  part  of  its  length,  and 
thus  placing  the  several  segments  in  communication  with  each  other,  the 
fibres  of  reinforcement  thus  constitute  a  part  of  the  longitudinal  filaments  of 
the  cord, — the  remainder  consisting  of  the  fibres  continuous  with  the  cephalic 
ganglia. 

330.  Hitherto  we  have  spoken  only  of  that  division  of  the  nervous  system 
of  the  Articulata,  which  may  be  regarded  as  corresponding  with  the  sensory 
and  locomotive  ganglia  of  the  Mollusca  ;  we  have  next  to  inquire  what  we 
find  corresponding  with  the  branchial  ganglion.  It  is  to  be  recollected,  that  the 
respiratory  apparatus  of  Insects  is  diffused  throughout  the  whole  body,  so  that  its 
presiding  system  of  nerves  must  be  proportionally  extended;  and  we  are,  there- 
fore, prepared  to  find  the  branchial  ganglion  of  the  Mollusca  repeated,  like 
the  pedal,  in  each  segment.  Besides  the  nervous  trunks  proceeding  from  the 
ventral  cord  at  its  ganglionic  enlargement,  we  find,  in  most  of  the  Articulated 
classes,  a  series  of  smaller  nerves,  given  off  at  intermediate  points,  without 
any  apparent  swelling  at  the  points  of  divergence.  The  connections  of  these 
are  most  distinctly  traced  in  the  thoracic  region,  just  as  the  Larva  is  passing 
into  the  Pupa  state  ;  for  the  cords  of  the  ventral  column  then  diverge,  so  that 
an  additional  tract  may  be  seen  which  occupies  the  central  line.  By  a  close 
scrutiny,  this  tract  may  be  found  in  the  perfect  Insect,  on  the  superior  or  vis- 
ceral aspect  of  the  cord  ;  and  its  nerves  are  given  off  from  minute  ganglionic 
enlargements  upon  it.  It  seems  to  be  quite  unconnected,  along  its  whole 
course,  with  the  column  upon  which  it  lies.  Its  nerves,  however,  communi- 
cate with  those  of  the  sensori-motor  system  ;  but  they  have  a  separate  distri- 
bution, being  transmitted  especially  to  the  tracheae,  on  the  parietes  of  which 
they  ramify  minutely,  and  also  to  the  muscles  concerned  in  the  respiratory 
movements.  (The  latter,  however,  being  a  part  of  the  general  locomotive 
apparatus,  are  also  supplied  from  the  principal  ganglionic  column.)  These 
nerves,  then,  which  are  evidently  analogous  to  those  of  the  gills  and  siphonic 


KESPIRATORY  AND  STOMATO-GASTRIC  SYSTEMS  OF  INSECTS. 


261 


Fig.  129. 


apparatus  in  the  Mollusca,  may  be  regarded  as  corresponding  with  the  pneu- 
monic portion  of  the  Par  Vagum  in  Vertebrata  (which  is  in  like  manner  dis- 
tributed on  the  air  passages),  and  with  its  associated  motor  nerves. 

331.  In  comparing  the  nervous  system  of  Insects  with  that  of  the  higher 
Mollusca,  it  will  be  seen  that  they  differ  more  in  the  arrangement  and  in  the 
relative  proportion  of  their  parts,  than  in  their  essential  character.     In  both 
there  is  a  Cephalic  division  of  the  ganglionic  centres,  in  which  sensibility  and 
psychical  power  appear  to  reside  more  particularly,  if  not  entirely.     In  both 
there  is  a  division  specially  appropriated  to  the  Locomotive  apparatus,  differ- 
ing only  in  the  multiplication  of  the  centres  in  Insects,  conformably  with  the 
arrangement  of  the   members   they  supply  ;  and  sometimes   consolidated  to 
nearly  the  same  degree.     In  both,  also,  we  find  a  division  appropriated  to  the 
Respiratory  apparatus,  in  which  there  is  a   corresponding  multiplicity  of 
centres  in  the  Articulata,  in  harmony  with  the  universal  distribution  of  their 
tracheal  system.     And  in  both,  as  we  shall  now  see, 

there  is  a  separate  system  of  nerves,  distributed  to  the 
alimentary  apparatus,  and  supplying  the  organs  of  mas- 
tication (with  the  salivary  glands),  of  deglutition,  and  of 
digestion. 

332.  Of  the  stomato- gastric  system,  some  traces  may 
be  found  in  nearly  all  the  Articulated  classes.     Thus, 
in  the   Leech,  we  find  a  minute  ganglion  existing  at  the 
base  of  each  of  the  three  teeth  which  form  the  mouth ; 
these  ganglia  are  connected  together,  and,  to  the  cephalic 
by  slender  filaments ;  and  they  seem  also  to  be  in  con- 
nection with  other  filaments,  which  may  be  traced  on  the 
alimentary  canal.     As  a  specimen  of  its  highly-deve- 
loped form,  we  shall  describe  that  of  the    Gryllotalpa 
vulgaris  (Common  Mole-Cricket).  Here  we  find  it  con- 
sisting of  two  divisions;  one   placed   on    the    median 
line,  which  may  hence  be   called  the  median  system ; 
the  other  running  on  each  side  at  some  little  distance, 
and  hence  called  the  lateral  system. — The  median  sys- 
tem appears  to  originate  in  a  small  ganglion,  situated  an- 
teriorly and  inferiorly  to  the  cephalic  mass,  with  which 
it  communicates  by  a   connecting  branch  on  each  side. 
From  this  ganglion,  nerves  proceed  to  the  walls  of  the 
buccal  cavity,  the  mandibles,  &c.     Its  principal   trunk, 
however,  (the  recurrent  of  authors,)  is  sent  backwards 
beneath  the   pharynx.      The  ramifications  of  this  are 
distributed  along  the  cesophageal  tube   and  dorsal  ves- 
sel ;  whilst  the  trunk  passes  downwards  to  the  stomach, 
where  its  branches  inosculate  with  those   supplied  by 
the  lateral  system,  and   seem   to  assist  in  forming    a 
pair  of  small  ganglia,  from  which  most  of  the  visceral 
nerves  radiate. — The  ganglia  of  the  lateral  system  are 
two  on  each  side,  lying  behind  and  beneath  the  cephalic 
masses.     The  anterior  pair  are  the  largest,  and  meet  on 
the  median  line,  just  behind  the  cephalic  ganglia,  with 
which  they  communicate.     Posteriorly  to  these  lie  the 
second  pair,  which  are  in  connection  with  them.     Two 
cords  pass  backwards  on  each  side  ;  one  derived  from 
the  anterior,  the  other  from  the  posterior,  of  these  gan- 
glia.    They  run  along  the  sides  of  the  oesophagus  and 

dorsal  vessel ;  and,  after  inosculating  with  the  branches  of  the  central  system 


IV 

Stomato-gastric  system 
of  Gryllotalpa  vulgaris  ; 
AA,  cephalic  ganglia;  a, 
anterior  median  ganglion 
with  the  recurrent  trunk 
passing  downwards  from 
it ;  66,  and  ec,  lateral  gan- 
glia ;  d,  visceral  ganglia. 


262  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

enter  the  two  cceliac  ganglia,  from  which  branches  radiate  to  the  abdominal 
viscera. 

333.  This  system  of  ganglia  and  nerves  has  an  evident  affinity  with  the 
Sympathetic  system  of  Vertebrate,  as  well  as  with  some  parts  of  the  Cerebro- 
spinal  system,  more  especially  with  the  Par  Vagum.     It  is  to  be  remembered, 
that  the  Pneumogastric  nerve  of  Vertebrata  is  distributed  to  three  separate 
systems — the   respiratory,   the  circulating  and  the  digestive.     As  we  know 
that  the  ultimate   fibrils   of  nerves   never  anastomose,  there  can  be  no  doubt 
that  these  branches  might  be  separately  traced  backwards  into  their  ganglionic 
centres ;  and  they  may  thus  be  regarded  as  functionally  three  distinct  nerves, 
though  bound  up  in  a  single  trunk.     There  is  no  difficulty,  then,  in  under- 
standing  that  the  respiratory  system    of  nerves,  in  Insects,  and  other  In- 
vertebrata,  may  be  analogous  with  the  pneumonic  portion  of  the  Par  Vagum  ; 
although  it  bears  no  relation  with   the  cardiac  and  gastric  divisions  of  the 
nerve.     To  the  latter  divisions,  the  analogy  of  the  recurrent  nerve  becomes 
sufficiently  plain,  when  we  look   at  its  distribution  upon  the  dorsal  vessel, 
oesophagus,  and  stomach  ;*  but  its  commencement  in  the  anterior  ganglion, 
which  also  supplies  the  mouth  and  pharynx,  might  seem  to  place  it  on  a  dif- 
ferent footing,  until  we   have  determined  the  true  analogy  of  this  last  centre. 
It  may  be  inferred  from  its  situation,  and  from  the   distribution  of  its  nerves, 
that  this   anterior  ganglion  is   analogous  both  to  the   labial  and   pharyngeal 
ganglia  of  the  higher  Mollusca.     These  appear  to   form  a  division  of  the 
nervous  system,  by  whichfthe  actions  immediately  concerned  in  the  prehen- 
sion of  food  are  performed  ;  and  these  seem   almost  as   independent  of  the 
cephalic  ganglia,  as  are  those  of  respiration.     There  is  evidently,  however, 
a  greater  tendency  towards  the  union  of  these  centres  with  the  oesophageal 
collar,  than  of  those  presiding  over  the  respiratory  function,  which  is  more 
independent  of  the  will. 

334.  The  division  of  the  nervous  system  of  Vertebrata  with  which  the 
central  portion  of  this  system  corresponds,  is  a  question  of  some  apparent 
difficulty;  but,  if  we  bring  into  comparison   not  only  the  highest  but   the 
lowest  forms  of  the  cerebro-spinal  apparatus,  the  chief  difficulties  will  be 
removed.    The  analogies  drawn  from  the  distribution  of  the  nervous  branches 
would  lead  us  to  infer,  that  the  third  division  of  the  Fifth  pair  (including  its 
sensory  and  motor  origins),  the  Glosso-Pharyngeal,  and  the  gastric  portion  of 
the  Par  Vagum,  would  most  nearly  represent  its  central  portion.    Now,  when 
the  fifth  pair  is  traced  back  to  its  true  origin,  it  is  found  to  be  not  a  cerebral 
but  a  spinal  nerve;  and  it  is  then  seen  to  arise  from  the  Medulla  Oblongata, 
in  such  close  approximation  with  the  par  vagum  and  glosso-pharyngeal,  as  to 
show  that,  if  this  portion  of  the  nervous  centres  were  isolated  from  the  rest, 
the  nerves  which  proceed  from  it  would  form,  anatomically  as  well  as  func- 
tionally, a  natural  group.     The  fifth  pair,  like  other  spinal  nerves,  may  act  in 
a  simply-reflex  character;  although,  in  Man,  it  is  usually  under  the  dominion 
of  the  will.    In  the  lower  animals  we  find  these  reflex  actions  bearing  a  much 
larger  proportion  to  the  voluntary,  than  in  Man;  and  even  in  him  we  not 
unfrequently  meet  with  cases,  in  which  the  functions  of  the  cerebral  hemi- 
spheres seem  suspended,  whilst  those  of  the  spinal  cord  are  unimpaired ;  so 
that  the  prehension  of  food  by  the  lips  may  take  place  without  any  effort  of 
the  will.     This  has  been  observed  in  anencephalous  fetuses,  in  puppies  from 
which  the  brain  has  been  removed,  and  in  profound  apoplexy.     Further,  the 
connection  between  the  fifth  pair  and  par  vagum  is  very  intimate  in  fishes ;  the 
class  which  approaches  nearest,  in  the  character  of  its  nervous  system,  to 
Invertebrata.     We  may  reasonably  infer,  then,  that  the  anterior  ganglion  is 

*  See  Newport,  in  Phil.  Trans.,  1832,  p.  386. 


STOMATO-GASTRIC  SYSTEM  OF  INVERTEBRATA.  263 

the  principal  centre  of  the  reflex  actions  of  those  nerves,  which  correspond  to 
the  third  branch  of  the  fifth  pair,  to  the  glosso-pharyngeal,  and  to  the  gastric 
portion  of  the  par  vagum,  in  Vertebrata ;  whilst  the  branches  which  connect 
them  with  the  cephalic  ganglia,  bring  these  nerves  more  or  less  under  the 
influence  of  the  latter. — The  lateral  ganglia  seem  more  analogous  to  the 
centres  of  the  Sympathetic  system  in  Vertebrata;  especially  in  the  connection 
of  their  branches  with  all  the  other  systems  of  nerves;  and  in  the  share 
which  they  have  in  the  formation  of  the  coeliac  ganglia.  This  view  of  the 
relative  functions  of  these  two  divisions  of  the  stomato-gastric  system,  is 
strengthened  by  the  fact,  that  the  connection  between  the  Sympathetic  system 
of  Fishes  and  the  Par  Vagum  is  much  more  intimate  than  in  the  higher 
Vertebrata;  although,  even  in  the  latter,  as  will  be  shown  hereafter,  it  is  by  no 
means  so  slight  as  it  appears.* 

335.  Upon  taking  a  general  review  of  the  facts  which  have  been  stated, 
and  of  the  inferences  which  have  been  erected  upon  them,  we  perceive  that 
a  gradual  elevation  may  be  traced,  in  the  character  of  the  actions  to  which  the 
Nervous  System  is  subservient,  as  we  ascend  from  the  lower  to  the  higher 
parts  of  the  Animal  Scale.  In  the  Radiata  and  lower  Mollusca,  in  which  no 
organs  of  special  sensation  exist,  all,  or  nearly  all,  of  the  movements  which 
are  witnessed,  may  be  legitimately  regarded  as  simply  reflex  in  their  character ; 
being  analogous  to  those,  which  are  unquestionably  so  in  the  higher  animals ; 
and  being  performed  by  the  instrumentality  of  a  nervous  apparatus,  that 
seems  to  have  little  else  than  an  internuncial  purpose.  But  when,  as  in 
the  higher  Mollusca  and  in  nearly  all  the  Articulata,  we  meet  with  distinct 
organs  of  special  sensation,  it  becomes  evident  that  the  consciousness  of  the 
animal  must  be 'concerned  in  the  direction  of  its  actions;  since  no  impressions 
upon  these  organs  (the  eyes,  for  example)  can  exert  any  motor  influence  on 
the  muscles,  except  by  producing  sensations ; — that  is,  if  we  may  apply  to 
the  lower  tribes  the  laws  deduced  from  the  study  of  the  higher.  Whilst, 
therefore,  a  large  proportion  of  the  actions  of  the  higher  Invertebrata  still 
continues  to  be  reflex  (as  we  have  especially  seen  in  the  Articulata),  a  new 
group  is  superadded  to  these;  and  this,  consisting  of  actions,  which  are 
directly  stimulated  by  sensations,  and  in  which  no  Reasoning  powers  nor 
Will  appear  to  have  any  direct  participation,  may  be  termed  consensual. 
They  require,  as  their  instruments,  a  set  of  ganglia  to  receive  the  trunks  which 
originate  in  the  organs  of  sense,  and  to  issue  motor  nerves  to  the  several  parts 
of  the  body.  These  last  are  distributed  along  with  the  trunks,  which  are 
connected  with  the  ganglia  belonging  to  each  particular  organ ;  thus  the  legs 
and  wings  of  an  Insect  appear  to  derive  their  motor  nerves,  partly  from  the 
ganglia  of  the  ventral  cord,  which  minister  to  their  reflex  actions,  and  partly 
from  the  cephalic  ganglia,  which  seem  to  harmonize,  to  control,  and  even  to 
antagonize,  the  influence  of  the  former.  In  like  manner,  the  parts  of  the 
body,  which  are  capable  of  receiving  sensory  impressions,  appear  to  have  a 
double  connection;  one  with  the  ganglia  of  the  ventral  cord,  for  the  purpose 
of  conveying  thither  those  impressions  which  are  destined  to  excite  reflex 
actions ;  and  the  other  with  the  cephalic  ganglia,  in  order  to  originate  sensa- 
tions.— Of  this  double  system  of  nerves  and  ganglia,  the  one  connected  solely 

*  The  view  given  above  of  the  comparative  structure  and  offices  of  the  Nervous  System, 
in  the  Invertebrated  animals,  is  chiefly  abridged  from  the  Author's  Prii.3  Thesis  on  this 
subject;  in  which  additional  details  will  be  found,  as  well  as  many  other  illustrative  figures 
and  references  to  authorities.  He  has  there,  also,  discussed  the  physiological  explanation 
which  had  been  previously  given  of  the  double  nervous  cord  of  the  Articulata ;  and  having 
shown  that  it  is  neither  consistent  with  itself,  nor  capable  of  being  applied  to  the  other 
Invertebrata,  he  has  deemed  it  unnecessary  to  complicate  the  present  sketch  by  introducing  it. 


264  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

with  the  reflex  actions,  and  the  other  with  the  consensual,  the  existence  in 
Articulata  seems  to  be  clearly  established  by  Mr.  Newport's  researches 
(§  326) ;  and  although  the  distinction  between  the  afferent  and  motor  fibres, 
of  each  system  respectively,  has  not  here  been  clearly  made  out,  there  can  be 
no  reasonable  doubt  of  its  existence. 

336.  The  class  of  consensual  actions  evidently  becomes  more  predominant, 
in  proportion  as  the   special  sensory  organs  are  more  evolved,  and  as   the 
ganglia  in  immediate  connection  with  them  (and  altogether  forming  the  cephalic 
mass)  present   an    increase    in   their   proportionate    development.     This    is 
especially  the  case  in  the  higher  Articulata ;  in  which  the  Instinctive  group  of 
actions  attains  its  highest  perfection   and  predominance.     The  propriety  of 
referring  these  to  the  consensual  group,  will  be  obvious  upon  a  little  considera- 
tion.    They  are  as  evidently  prompted  by  particular  sensations,  as  are  the 
reflex  actions  by  particular  impressions;  and  the  respondence  is  as  uniform 
in  the  one  case,  as  in  the  other.     Although  in  these  movements,  there  is  a 
most  remarkable    adaptation  of  means  to   ends,  (as  in   the  construction  of 
habitations  by  various  Insects,  and  especially  by  the  social  Hymenoptera,) 
yet  few  persons  will  maintain  that  this  adaptation  is  performed  by  the  reason 
of  the  animal;  since,  on  this  supposition,  every  Bee  solves  a  problem  which 
has  afforded  scope  for  the  laborious  inquiries  of  the  acutest  human  mathe- 
matician.*   The  adaptation  is  in  the  original  construction  of  a  nervous  system, 
which  should  occasion  particular  movements  to  be  performed  under  the  in- 
fluence of  particular  sensations ;   and   the  constancy  with  which  these   are 
performed  by  different  individuals  of  the  same  species,  when  placed  in  the 
same  conditions,  leads  at  once  to  the  belief,  that  they  must  be  independent  of 
any  operations  so  variable  as  those  of  judgment  and  voluntary  exertion. 

337.  On  the  other  hand,  in  the  Vertebrata,  we  shall  find  the  purely  reflex 
and  consensual  movements  forming  a  smaller  proportion  of  their  actions,  and 
brought  under  a  more  complete  subjection  to  the  Volitional  system.     This  is 
evident,  from  the  greater  variety  which  the  actions  exhibit ;  from  the  mode  in 
which  they  are  adapted  to  peculiar  circumstances ;  from  the  degree  in  which 
they  may  be  modified  by  education ;  and  from  various  other  indications  of  a 
superior  kind  of  Intelligence.     At  last,  in  adult  Man,  we  perceive  that  all  the 
movements,  which  are  elsewhere  involuntary,  but  which  are  not  immediately 
requisite  (as  are  those  of  deglutition,  respiration,  <fcc.)  for  the  maintenance  of 

*  The  hexagonal  form  of  the  cell  is  the  one  in  which  the  greatest  strength,  and  the  nearest 
approach  to  the  cylindrical  cavity  required  for  containing  the  larva,  are  attained,  with  the 
least  expenditure  of  material.  But  the  instinct  which  directs  the  Bees  in  the  construction 
of  the  partition  that  forms  the  bottom  or  end  of  the  cell,  is  of  a  nature  still  more  wonderful 
than  that  which  governs  its  general  shape.  The  bottom  of  each  cell  rests  upon  three  parti- 
tions of  cells  upon  the  opposite  side  of  the  comb ;  so  that  it  is  rendered  much  stronger,  than 
if  it  merely  separated  the  cavities  of  two  cells  opposed  to  one  another.  The  partition  is  not 
a  single  plane  surface;  but  is  formed  by  the  union  of  three  rhomboidal  planes, uniting  in  the 
centre  of  each  cell.  The  angles  formed  by  the  sides  of  these  rhombs,  were  determined  by 
the  measurements  of  Maraldi  to  be  109°  28'  and  72°  32';  and  these  have  been  shown,  by 
mathematical  calculation,  to  be  precisely  the  angles,  at  which  the  greatest  strength  and  capa- 
city can  be  attained,  with  the  least  expenditure  of  wax.  The  solution  of  the  problem  was 
first  attempted  by  Koenig,  a  pupil  of  the  celebrated  Bernouilli ;  and  as  his  result  proved  to 
differ  from  the  observed  angle  by  only  two  minutes  of  a  degree,  it  was  presumed  that  the 
discrepancy  was  due  to  an  error  of  observation,  which  it  was  easy  to  account  for  by  the 
smallness  of  the  surfaces  whose  inclination  had  to  be  measured.  The  question  has  been 
since  taken  up,  however,  by  Lord  Brougham  (Appendix  to  his  Illustrated  edition  of  Paley's 
Natural  Theology) ;  who  has  worked  it  out  afresh,  and  has  shown  that,  when  certain  small 
quantities,  neglected  by  Koenig,  are  properly  introduced  into  the  calculation,  the  result  is  . 
exactly  accordant  with  observation, — the  Bees  being  thus  proved  to  be  right,  and  the  Mathe- 
matician wrong. 


NERVOUS  SYSTEM  OF  VERTEBRATA.  265 

the  Organic  functions,  are  placed  under  the  control  of  the  Will,  guided  by  the 
reasoning  faculties.  This  is  especially  true  of  the  locomotive  organs,  whose 
reflex  actions  are  entirely  governed  by  the  will ;  being  only  distinguishable  as 
such,  when,  from  peculiar  states  of  the  system,  the  immediate  influence  of 
the  controlling  power  is  suspended. — We  shall  find  ground  to  believe,  that 
the  exercise  of  the  Reasoning  faculties,  and  the  resulting  operations  of  the 
Will,  take  place  through  the  instrumentality  of  another  division  of  the  nervous 
centres ;  to  which  there  is  nothing  distinctly  analogous  among  the  Inverte- 
brata ;  but  which  seems  to  bear  a  constant  proportion  in  size  and  importance, 
among  Vertebrated  animals,  to  the  development  of  the  Intelligence  and  its 
influence  on  the  movements  of  the  body : — namely,  the  Cerebral  ganglion. 

338.  There  is  another  aspect,  however,  under  which  we  are  to  consider 
the  Nervous  System ;  and  this  becomes  more  important  in  the  highest  division 
of  the  Animal  kingdom,  on  which  we  are  now  about  to  dwell.     We  have 
hitherto  spoken  only  of  its  influence  on  the  contractile  properties  of  the  tis- 
sues, to  which  it  is  distributed.     It  has,  however,  an  important  and  direct 
connection  with  the  purely  organic  functions  of  Nutrition  and  Secretion;  and 
we  shall  see  reason  to  regard  it  as  the  means,  not  only  of  placing  the  animal 
in  relation  with  the  external  world,  but  of  harmonizing  and  controlling  the 
organic  changes  taking  place  in  its  own  structure,  and  of  bringing  these  under 
the  influence  of  particular  mental  conditions.     The  opinion  is  entertained  by 
many,  that  all  the  Organic  Functions  are  dependent  upon  the  innervation, 
supplied  to  them  by  the  system  of  nerves,  which  has  been  termed  Sympathetic 
or  visceral.     It  is  incumbent,  however,  on  those  who  uphold  the  necessity  of 
this  nervous  power,  to  prove  it  definitively ;  since  all   analogy  leads  to  an 
opposite  conclusion.     We  may  regard  the  capability  of  separating  a  particular 
secretion  from  the  blood,  as  a  peculiar  property  inherent  in  the  glandular  cells, 
just  as  contractility  is  the  inherent  property  of  muscular  fibre.     But  as  the 
peculiar  arrangement  of  the  excitable   and    contractile  tissues   in  Animals, 
requires  a  nervous  system  to  act  as  a  conductor  between  them,  and  to  blend 
their  actions;  so  may  the  complicated  Organic  functions  of  Animals  require 
to  be  harmonized  and  kept  in  sympathy  with  each  other,  by  some  mode  of 
communication  more  direct  and  certain  than  that  afforded  by  the  circulating 
system,  which  is  their  bond  of  union  in  Plants.     We  have  seen,  in  the  fore- 
going sketch,  that  the  Visceral  system  does  not  exist  in  a  distinct  form  in  the 
lower  classes  of  Invertebrated  animals  ;  and  also  that  the  nervous  system  of 
these  classes  cannot,  as  a  whole,  be  compared  with  it,  although  it  may  be 
regarded  as  containing  some  rudiments  of  it.     As  the  divisions  of  this  system 
become  more  evident,  however,  and  the  organic  functions  more  complicated, 
some  appearance  of  a  separate  Sympathetic  system  presents  itself;  but  this  is 
never  so  distinct  as  in  Vertebrata.     Hence,  it  may  fairly  be  inferred  that, — as 
the  Sympathetic  system  is  not  developed  in  proportion  to  the  predominant 
activity  of  the  functions  of  organic  life  (which  is  so  remarkable  in  the  Mol- 
lusca  when  contrasted  with  the  Articulata),  but  in  proportion  to  the  develop- 
ment of  the  higher  divisions  of  the  nervous  system, — its  office  is   not  to 
contribute  to  these  functions    anything  essential  to  their  performance ;  but 
rather  to  exercise  that  general  control  over  them  which  becomes  the  more 
necessary  as  they  become  more  independent  of  one  another;  and  to  bring 
them  into  relation  with  the  system  of  Animal  life. 

3.  Nervous  System  of  Vertebrata. 

339.  When  we  direct  our  attention  to  the  Nervous  System  of  the  Verte- 
brated classes,  we  are  immediately  struck  by  two  remarkable  differences  which 
its  condition  presents,  from  that  under  which  we  have  seen  it  to  exist  in  the 

23 


266  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

Invertebrata.  In  the  latter  it  has  seemed  but  a  mere  appendage  to  the  rest  of 
the  organism, — a  mechanism  superadded  for  the  purpose  of  bringing  its  various 
parts  into  more  advantageous  relation.  On  the  other  hand,  in  the  Vertebrata 
the  whole  structure  appears  subservient  to  it,  and  designed  but  to  carry  its 
purposes  into  operation.  Again,  in  the  Invertebrata,  we  do  not  find  any 
special  adaptation  of  the  organs  of  support,  for  the  protection  of  the  Nervous 
System.  It  is  either  inclosed,  with  the  other  soft  parts  of  the  body,  in  one 
general  hard  tegumentary  envelope,  as  in  the  Echinodermata  and  Articulata; 
or  it  receives  a  still  more  imperfect  protection,  as  in  the  Mollusca.  In  the 
latter,  the  naked  species  are  destitute  of  any  means  of  passive  resistance,  and 
the  Nervous  System  shares  the  general  exposed  condition  of  the  whole  body  ; 
and  it  is  not  a  little  remarkable  that,  in  the  testaceous  kinds,  the  portion  of 
the  body  containing  the  most  important  nervous  centres  should  be  protruded 
beyond  the  shell,  whilst  the  principal  viscera  are  retained  within  it.  Now, 
in  the  Vertebrata,  we  find  a  special  and  complex  bony  apparatus,  adapted  in 
the  most  perfect  manner  for  the  protection  of  the  Nervous  System ;  and  it  is, 
in  fact,  the  possession  of  a  jointed  spinal  column,  and  of  its  cranial  expansion, 
which  best  characterizes  tiie  group. 

340.  When  we  look  more  particularly  at  the  Nervous  Centres  themselves, 
we  perceive  that  they  combine  the  general  characters  of  those  of  the  Articulata 
with  those  of  the  Mollusca ;  the  locomotive  powers  of  the  former  (compara- 
tively reduced,  however,  in  activity)  being  united  with  the  complex  nutritive 
system  of  the  latter ;  and  we  find  this  combination  manifested,  not  only  in 
the  organs  themselves,  but  in  the  Nervous  System,  which  stands  in  so  close 
a  relation  with  them.  The  Spinal  Cord  of  Vertebrata  is  evidently  the  ana- 
logue of  the  ventral  columns  of  Articulata.  It  is  a  continuous  ganglion,  con- 
taining two  portions  as  distinct  as  the  two  tracts  in  the  Articulata ; — a  fibrous 
•structure,  which  is  continuous  between  the  Brain  and  the  spinal  nerves,  and 
thus  resembles  the  white  tract  in  Insects ; — and  a  ganglionic  portion,  princi- 
pally composed  of  gray  matter.  Into  this  gray  matter,  as  in  the  ventral  gan- 
glia of  Insects,  a  part  of  the  roots  of  the  spinal  nerves  may  be  traced ;  whilst 
others  seem  to  pass  on  continuously  to  the  brain.  At  the  upper  extremity  of 
the  Spinal  cord  (commonly  termed  the  Medulla  Oblongata]  we  find  the 
ganglia  and  nerves  of  special  sensation;  and  the  organs  which  these  supply 
are  placed  in  immediate  proximity  with  the  entrance  to  the  alimentary  canal, 
holding  the  same  relation  to  it  as  in  the  Mollusca.  But  in  addition  to  these 
we  find  two  ganglionic  masses  in  all  Vertebrata,  to  which  we  have  no  distinct 
analogue  in  the  lower  classes — the  Cerebral  Hemispheres,  and  the  Cerebel- 
lum. With  the  development  of  the  former  of  these,  as  already  remarked, 
the  perfection  of  the  reasoning  powers  appears  to  hold  a  close  relation ;  that 
of  the  latter  seems  connected  with  the  necessity  which  exists,  for  the  adjust- 
ment and  combination  of  the  locomotive  powers,  when  the  variety  of  move- 
ments performed  by  the  animal  is  great,  and  the  harmony  required  among 
them  is  more  perfect.  Upon  these  points,  however,  we  shall  hereafter 
dwell. 

341.  The  Visceral  system  of  nerves  now  assumes  a  more  distinct  form. 
It  does  not  share  the  protection  of  the  Spinal  column;  but  its  ganglia  lie  for 
the  most  part  in  the  general  cavity  of  the  trunk.  These  ganglia,  which 
are  doubtless  the  independent  centres  of  some  of  the  nerve-fibres  proceed- 
ing from  them,  are  much  more  numerous  than  is  commonly  supposed.  It 
appears  from  recent  researches,  that  we  are  to  regard  as  belonging  to  the 
Visceral  or  Sympathetic  system,  not  only  the  Semilunar  and  Cardiac  ganglia 
(which  seem  to  be  its  principal  centres),  with  the  chain  of  cranial,  cervical, 
thoracic,  lumbar,  and  sacral  ganglia,  which  are  in  nearer  proximity  to  the 


NERVOUS  SYSTEM  OF  VERTEBRATA. 


267 


[Fig.  130. 


Cerebro-spinal  system,  but  also  nu- 
merous minute  ganglia,  which  are 
to  be  found  on  its  branches  in  vari- 
ous parts,  and,  in  addition,  the  gan- 
glia upon  the  posterior  roots  of  the 
Spinal  nerves.  If,  indeed,  we  are 
to  regard  the  fine  nerve  -  fibres, 
wherever  they  present  themselves, 
as  belonging  to  the  Visceral  sys- 
tem, we  must  regard  this  as  still 
largely  interwoven  with  the  Cere- 
bro-spinal system,  notwithstanding 
that  the  former  has  its  own  set  of 
ganglionic  centres ;  since,  as  already 
mentioned  (§  244),  these  peculiar 
fibres  are  found  in  considerable 
numbers  in  all  the  Cerebro-spinal 
nerves,  and  may  be  shown  to  origi- 
nate in  the  caudate  corpuscles  of 
the  Brain  and  Spinal  Cord.  On 
the  other  hand,  there  unquestion- 
ably exist  numerous  fibres  in  the 
Visceral  system,  which  proceed 
into  it  from  the  Cerebro-spinal  sys- 
tem; these,  however,  are  not  uni- 
formly distributed,  for  some  of  the 
Visceral  nerves  contain  few  or  none 
of  them,  whilst  in  others  they  are 
numerous.  The  branches  by  which 
the  Sympathetic  system  communi- 
cates with  the  Cerebro-spinal,  and 
which  were  formerly  considered  as 
the  roots  of  the  Sympathetic  sys- 
tem, contain  fibres  of  both  kinds : — 
i.  e.,  Cerebro-spinal  fibres  passing 
into  the  Sympathetic,  and  Sym- 
pathetic fibres  passing  into  the 
Cerebro  -  spinal.  The  latter  are 
chiefly,  if  not  entirely,  transmit- 
ted into  the  anterior  branches  of 
the  Spinal  nerves;  the  posterior 
branches  being  principally  supplied 
with  fine  fibres,  from  the  ganglia  on 


A  view  of  the  Great  Sympathetic  Nerve. — 1,  the  plexus  on  the  carotid  artery  in  the  carotid  foramen; 
2,  sixth  nerve  (motor  externus);  3,  first  branch  of  the  fifth  or  ophthalmic  nerve  ;  4,  a  branch  on  the  sep- 
tum narium  going  to  the  incisive  foramen ;  5.  the  recurrent  branch  or  vidian  nerve  dividing  into  the 
carotid  and  petrosal  branches;  6,  posterior  palatine  branches;  7,  the  lingual  nerve  joined  by  the  corda 
tympani;  8,  the  portio  dura  of  the  seventh  pair  or  the  facial  nerve;  9,  the  superior  cervical  ganglion; 
10,  the  middle  cervical  ganglion ;  11,  the  inferior  cervical  ganglion ;  12,  the  roots  of  the  great  splanchnic 
nerve  arising  from  the  dorsal  ganglia;  13,  the  lesser  splanchnic  nerve;  14,  the  renal  plexus;  15,  the  solar 
plexus;  16,  the  mesenteric  plexus ;  17,  the  lumbar  ganglia;  18,  the  sacral  ganglia;  19,  the  vesical  plexus; 
20,  the  rectal  plexus;  21,  the  lumbar  plexus  (cerebro-spinal) ;  22,  the  rectum;  23,  the  bladder;  24,  the 
pubis;  25,  the  crest  of  the  ileum;  26,  the  kidney;  27,  the  aorta;  28,  the  diaphragm;  29,  the  heart;  30,  the 
larynx  ;  31,  the  sub-maxillary  gland  ;  32,  the  incisor  teeth ;  33,  nasal  septum ;  34.  globe  of  the  eye ;  35, 
36,  cavity  of  the  cranium.] 


268 


FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 


[Fig.  131.  their  posterior  roots.   Some  of  these 

last  fibres  also  pass,  with  the  ordi- 
nary large  nerve-tubes,  from  the 
Cerebro-spinal  into  the  Sympathetic 
system.  By  these  communications 
the  two  systems  of  fibres  are  so 
blended  with  each  other,  that  it  is 
impossible  to  isolate  them;  and  all 
that  can  be  said  is,  that  the  large 
tubular  fibres  predominate  in  the 
former,  and  the  fine  homogeneous 
fibres  in  the  latter. 

342.  The  branches  proceeding 
from  the  Semilunar  ganglia  are  dis- 
tributed upon  the  abdominal  viscera; 
and  those  of  the  Cardiac  ganglia 
upon  the  heart  and  the  vessels  pro- 
ceeding from  it.  The  latter  seem 
to  accompany  the  arterial  trunks 
through  their  whole  course,  rami- 
fying minutely  upon  their  surface; 
and  it  can  scarcely  be  doubted,  that 
they  exercise  an  important  influ- 
ence over  their  functions.  What 
the  nature  of  that  influence  is,  how- 
ever, will  be  a  subject  for  future 
inquiry.  It  is  so  evidently  con- 
Roots  of  a  dorsal  spinal  nerve,  and  its  union  with  nected"  with  the  operations  of  nutri- 
sympathetic:-C,c.  Anterior  fissure  of  the  spinal  cord.  ^  secretion,  &C.,  that  the  de- 

a.  Anterior  root.    p.  Posterior  root,  with  its  ganglion.  r    ,.  ,, 

«'.  Anterior  branch.  „'.  Posterior  branch.  ,.  Sympa-  SlgnatlOn  of  nervOUS  System  of 
thetic.  e.  Its  double  junction  with  the  anterior  branch  Organic  life,  as  applied  to  this  SVS- 
of  the  spinal  nerve  by  a  white  and  a  grey  filament]  tem  does  not  Seem  objectionable, 

provided  that  we  do  not  understand 

it  as  denoting  the  dependence  of  these  functions  upon  it. — Even  in  Vertebrata, 
however,  we  do  not  always  find  the  distribution  of  the  visceral  trunks  distinct 
from  those  of  the  cerebro-spinal.  In  the  Cyclostome  Fishes,  the  par  vagum 
supplies  the  intestinal  canal  along  its  whole  length,  as  well  as  the  heart;  and 
no  appearance  of  a  distinct  sympathetic  can  be  discovered.  In  Serpents, 
again,  the  lower  part  of  the  alimentary  canal  is  supplied  from  the  spinal  cord, 
and  the  upper  part  by  the  par  vagum;  and  though  the  lateral  cords  of  the 
sympathetic  may  be  traced,  they  are  almost  destitute  of  ganglia.  Even  in 
the  highest  Vertebrata,  some  of  the  glands,  of  which  the  secretion  is  most 
directly  influenced  by  the  condition  of  the  mind,  are  supplied  with  most  of 
their  nerves  from  the  cerebro-spinal  system ;  thus,  the  lachrymal  and  sublin- 
gual  glands  receive  large  branches  from  the  fifth  pair,  and  the  mammary 
glands  from  the  intercostal  nerves.  But  it  appears  probable,  from  what  has 
just  been  stated,  that  the  influence  is  conveyed  through  the  visceral  fibres, 
contained  in  these  nerves,  and  either  originating  in  the  ganglia  at  their  roots, 
or  derived  from  the  Sympathetic  system. 

343.  The  Spinal  Cord,  with  its  encephalic  continuation — the  Medulla  Ob- 
longata, — may  be  regarded  as  constituting  the  essential  part  of  the  nervous 
system  of  Vertebrata.  Although  the  Cerebral  Hemispheres  in  Man  bear  so 
large  a  proportion  to  it  in  size,  that  the  Spinal  Cord  seems  but  a  mere  ap- 
pendage to  them,  the  case  is  reversed  when  we  look  at  the  other  extremity  of 
the  scale;  the  Cerebral  Hemispheres,  in  many  Fishes,  being  but  ganglionic 


NERVOUS  SYSTEM  OF  VERTEBRATA.  269 

protuberances  from  the  Medulla  Oblongata.  Moreover,  the  fact  that  animals 
are  capable  of  living  without  the  brain,  whilst  they  at  once  die  if  deprived  of 
the  spinal  cord,  sufficiently  demonstrates  this.  The  spinal  cord,  then,  when 
viewed  in  relation  to  the  nervous  system  of  the  Invertebrata,  may  be  regarded 
as  including  their  respiratory,  stomato-gastric,  and  pedal  ganglia.  That  these 
should  be  associated  together,  can  scarcely  be  considered  remarkable.  It  is 
obviously  convenient  that  they  should  all  be  inclosed  in  the  bony  sheath  pro- 
vided for  their  protection ;  and  their  closer  relation  favors  that  sympathy  of 
action,  which  is  so  important  in  animals  of  such  complex  structure  and 
mutually  dependent  functions,  as  the  higher  Vertebrata.  An  animal  either 
congenitally  or  experimentally  deprived  of  its  cerebral  hemispheres,  is  very 
much  in  the  condition  of  one  of  the  Acephalous  Mollusca.  It  can  perform 
those  respiratory  movements,  on  which  depend  the  maintenance  of  its  circu- 
lation, and  consequently  its  whole  organic  life ;  it  can  swallow  food  brought 
within  its  reach,  and  it  can,  in  some  degree,  exert  its  locomotive  powers  to 
obtain  it;  but  it  is  unconscious  of  the  direction  in  which  these  can  be  best 
employed,  and  is  dependent  upon  the  supplies  of  food  that  come  within  its 
grasp.  The  Acephalous  Mollusca  are  so  organized,  that  they  find  support 
from  the  particles  brought  in  by  their  respiratory  current;  but  the  more 
highly-organized  Vertebrata  are  not  capable  of  so  existing,  and  they  must 
have  their  food  provided  for  them  by  an  exertion  of  the  mental  powers.  So 
long  as  an  anencephalous  Vertebrated  animal  is  duly  supplied  with  its  requi- 
site food,  so  long  may  it  continue  to  exist,  although  in  a  state  analogous  to 
that  of  profound  sleep;  and  thus  it  is  seen,  that  the  operations  of  the  Brain 
are  not  immediately  connected  with  the  maintenance  of  the  organic  functions  ; 
the  movements  requisite  for  these  being  carried  on,  as  in  the  lower  animals, 
through  the  instrumentality  of  ganglionic  centres  and  nerves  specially  appro- 
priated to  them. 

344.  It  is  only  in  the  Vertebrata,  that  the  difference  between  the  afferent 
and  efferent  fibres  of  the  nerves,  has  been  satisfactorily  determined.  The 
merit  of  this  discovery  is  almost  entirely  due  to  Sir  C.  Bell.  He  was  led  to 
it  by  a  chain  of  reasoning  of  a  highly  philosophical  character;  and  though 
his  first  experiments  on  the  Spinal  nerves  were  not  satisfactory,  he  virtually 
determined  the  respective  functions  of  their  two  roots,  by  experiments  and 
pathological  observations  upon  the  cranial  nerves,  before  any  other  physiolo- 
gist came  into  the  field.*  Subsequently  his  general  views  were  confirmed 
by  the  very  decided  experiments  of  Muller ;  but,  until  very  recently,  some 
obscurity  hung  over  a  portion  of  the  phenomena.  It  was  from  the  first  main- 
tained by  Magendie,  and  has  been  subsequently  asserted  by  other  physiolo- 
gists, that  the  anterior  and  posterior  roots  of  the  nerves  were  both  concerned 
in  the  reception  of  sensations  and  in  the  production  of  motions ;  for  that, 
when  the  anterior  roots  were  touched,  the  animal  gave  signs  of  pain,  at  the 
same  time  that  convulsive  movements  were  performed ;  and  that,  on  touching 
the  posterior  roots,  not  only  the  sensibility  of  the  animal  seemed  to  be  affected, 
but  muscular  motions  were  excited.  These  physiologists  were  not  willing, 
therefore,  to  admit  more,  than  that  the  anterior  roots  were  especially  motor, 
and  the  posterior  especially  sensory.  But  the  recently  attained  knowledge  of 
the  reflex  function  of  the  spinal  cord,  enables  the  latter  portion  of  these  phe- 
nomena to  be  easily  explained.  The  motions  excited  by  irritating  the  pos- 
terior root  are  entirely  dependent  upon  its  connection  with  the  spinal  cord, 
and  upon  the  integrity  of  the  anterior  roots  and  of  the  trunks  into  which  they 
enter;  whilst  they  are  not  checked  by  the  separation  of  the  posterior  roots 
from  the  peripheral  portion  of  the  trunk.  It  is  evident,  therefore,  that  excita- 

*  See  British  and  Foreign  Medical  Review.     Vol.  ix.,  p.  140,  &c. 
23* 


270 


FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 


tion  of  the  posterior  root  does  not  act  immediately  upon  the  muscles  through 
the  trunk  of  the  nerve,  which  they  contribute  to  form;  but  that  it  excites  a 
motor  impulse  in  the  Spinal  Cord,  which  is  propagated  through  the  anterior 
roots 'to  the  periphery  of  the  system.  Thp  converse  phenomenon,  the  appa- 
rent sensibility  of  the  anterior  roots,  has  been  still  more  recently  explained 
by  the  experiments  of  Dr.  Kronenberg;*  which  seem  to  prove,  that  it  is  de- 
pendent upon  a  branch  of  the  posterior  root  passing  into  the  anterior  root  at 
their  point  of  inosculation,  and  then  directing  itself  towards  the  cord  (§  304). 
345.  On  the  other  hand,  the  distinctness  of  the  system  of  nerves  concerned 
in  the  simply-reflex  actions,  from  those  which  minister  to  sensation,  emotion, 
and  volition  by  their  connection  with  the  brain,  is  by  no  means  so  obvious  as 
in  the  Invertebrated  classes.  When  first  pointed  out  by  Dr.  Marshall  Hall, 
who  had  grounded  his  opinion  more  upon  physiological  phenomena  than 
upon  anatomical  facts,  the  statement  did  not  command  general  assent;  since, 
while  the  phenomena  were  admitted,  the  inferences  which  he  drew  from  them 
were  not  regarded  as  necessary  results.  When,  however,  the  anatomy  of 
the  Nervous  centres  in  Vertebrata  was  more  closely  inquired  into  (by  Mr. 
Grainger,  who  had  been  partly  anticipated  by  Bellingeri),  it  was  found  to 
present  certain  phenomena  which  might  be  regarded  as  supporting  Dr.  M. 
Hall's  views;  and  when  the  inquiry  was  extended  to  the  Invertebrated  classes, 
the  confirmation  was  found  to  be  still  more  decisive.  In  our  previous  sketch 
these  doctrines  have  been  treated  as  established;  since  they  have  been  found 
not  only  to  correspond  with  the  facts  disclosed  by  anatomical  research,  but  to 
be  required  by  them.  We  shall  now  apply  them  to  the  nervous  apparatus  of 
the  Vertebrata. 

346.  The  Spinal  Cord  consists  of  two  lateral  halves  ; 
Fig.  132.  these  are  partially  separated,  in  the  higher  classes,  by 

the  superficial  anterior  and  posterior  fissures  ;  and  in 
Fishes  by  an  internal  canal,  which  is  continuous  with  the 
fourth  ventricle.!  This  canal  is  evidently  the  indication 
of  that  complete  separation  of  the  two  columns,  which 
exists  in  the  lower  Articulata;  and  the  fourth  ventricle, 
which  in  many  Fishes  remains  unclosed  (the  cerebellum 
not  being  sufficiently  developed  to  overlap  it),  corre- 
sponds with  the  passage  between  the  cords  uniting  the 
cephalic  ganglia,  with  the  first  sub-oesophageal,  through 
which  the  cesophagus  passes  in  all  the  Invertebrata. 
The  two  lateral  halves  have  little  connection  with  each 
other  in  Fishes,  and  the  pyramidal  bodies  at  their  apex 
scarcely  decussate  ;  but  in  ascending  towards  the  higher 
classes,  the  communication  between  the  two  sides  is  more 
intimate,  and  a  larger  proportion  of  the  pyramidal  fibres, 
crosses  to  the  opposite  side.  In  all  the  Vertebrata,  the 
true  Spinal  Cord  contains  grey  substance,  or  something 
equivalent  to  it ;  thus  possessing  the  character  of  a  con- 
tinuous ganglion.  The  proportion  of  the  vertebral  column 
Frog;  A, oifactive  ganglia;  which  this  ganglion ic  portion  occupies,  is,  however,  ex- 
B,  cerebral  hemispheres ;  tremely  variable  ;  depending  principally  on  the  position 
c,  optic  ganglia;  D,  cere-  Of  tne  chief  organs  of  locomotion.  Thus,  in  the  Eel, 
beiium,  so  small  as  not  to  and  other  Vermiform  Fishes,  it  is  continued  through 

cover  the  4th  ventricle,  or      ,  ,     •,  .,  ,  ,  .,         .         IT-L-  j 

cavity  left  by  the  diver-  the  whole  spinal  canal ;  whilst  in  the  Lophius  and 
gence  of  the  columns  of  Tetraodon,  whose  body  is  less  prolonged,  and  more 
the  Spinal  Cord.  dependent  for  its  movements  upon  the  anterior  extremi- 

*  Miiller's  Archiv.,  1839,  Heft  v.;  and  Brit,  and  For.  Med.  Rev.,  vol.  ix.  p.  547. 
f  This  canal  may  be  traced  in  the  Spinal  Cord  of  Man  and  other  Mammalia;  but  it  is 
nearly  obliterated. 


Nervous     centres      in 


SPINAL  CORD  OF  VERTEBRATA. 


271 


ties,  the  true  Spinal  Cord  scarcely  passes  out  of  the  cranium.  The  quan- 
tity of  grey  matter  is  nearly  uniform  in  every  part  of  the  cord,  where 
there  is  no  great  diversity  in  the  functions  of  the  nerves  which  originate 
from  each  portion.  In  most  Fishes,  for  example,  the  body  is  propelled 
through  the  water  more  by  the  lateral  action  of  the  flattened  trunk  (whose 
surface  is  extended  by  the  dorsal  and  caudal  fins  erected  upon  prolonga- 
tions of  its  vertebra),  than  by  the  movements  of  its  extremities,  which  serve 
principally  to  guide  it.  Hence  we  usually  find  the  amount  of  grey  mat- 
ter varying  but  little  in  different  parts  of  the  cord.  But  in  the  Flying-fish, 
and  others  whose  pectoral  fins  are  unusually  powerful,  a  distinct  ganglionic 
enlargement  of  the  cord  takes  place  where  the  nerves  are  given  off.  In  Ser- 
pents, again,  the  spinal  cord  is  nearly  uniform  throughout  its  entire  length ; 
whilst  in  Amphibia  it  is  so  during  the  Tadpole  condition,  but  presents  enlarge- 
ments corresponding  to  the  anterior  and  posterior  extremities,  when  these  are 
developed;  at  the  same  time  becoming  much  shortened,  as  the  tail  is  less  im- 
portant to  locomotion,  or  is  altogether  atrophied.  In  Birds,  the  ganglionic 
enlargements  are  generally  very  perceptible  ;  and  bear  a  close  relation  in 
size,  with  the  development  of  the  locomotive  organs  with  which  they  are 
connected.  Thus,  in  birds  of  active  flight,  and  short  powerless  legs,  the  an- 
terior enlargement  is  the  principal ;  but  in  those  which  are  more  adapted  to 
run  on  hand  than  to  wing  their  way  through  the  air,  such  as  the  whole  tribe 
of  Struthious  birds,  the  size  of  the  posterior  enlargement  is  very  remarkable. 
Hence  we  have  a  right  to  infer,  that  the  increase  in  the  quantity  of  grey  mat- 
ter in  the  cord  has  some  connection  with  the  amount  of  power  to  be  supplied ; 
and  this  exactly  corresponds  with  what  has  been  observed  in  the  Articulated 
classes,  and  especially  in  watching  the  metamorphosis  of  Insects.  In  Birds 
and  Mammalia,  however,  the  whole  amount  of  the  grey  matter  in  the  spinal 
cord  does  not  bear  so  large  a  proportion  to  the  bulk  of  the  nerves  proceeding 
from  it,  as  in  the  lower  Vertebrata ;  and  the  reason  of  this  seems  obvious. 
The  actions  of  the  locomotive 

organs  are  less  and  less  of  a  Fig.  133. 

reflex  character,  and  are  more 
directly  excited  by  the  will, 
and  consequently  by  the  brain 
than  in  the  inferior  tribes ;  and 
just  in  proportion,  therefore, 
to  the  development  of  the 
Brain,  will  it  become  the  cen- 
tre of  all  the  actions  performed 
by  the  animal,  and  the  Spinal 
Cord  a  mere  appendage  to  it. 
Still,  in  all  the  Mammalia,  even 
in  Man,  do  we  find  these  gan- 
glionic enlargements  of  the 
spinal  cord ;  and  in  Man  it  is 
the  posterior  one  (or  rather  the 
inferior),  which  contains  the 
largest  quantity  of  grey  mat- 
ter. In  the  cord  of  this  class, 
too,  the  lateral  halves  are  much 
more  intimately  united,  than  in 
the  classes  below ;  for  not  only  is  the  central  canal  for  the  most  part  absent, 
but  the  two  crescent-shaped  plates  of  grey  matter  are  united  by  a  transverse 
lamella,  which  connects  their  centres  like  a  commissure. 

347.  The  Cord  is  transversed,  not  only  by  the  anterior  and  posterior  fis- 


Transverse  sections  of  human  Spinal  Cord  at  different 
points,  showing  the  proportional  quantity  and  arrangement 
of  grey  arid  white  matter  at  each :  1,  opposite  llth  dorsal  ver- 
tebra; 2,  opposite  10th  dorsal ;  3,  opposite  8th  dorsal;  4,  op- 
posite 5th  dorsal ;  5,  opposite  7th  cervical ;  6,  opposite  4th 
cervical;  7,  opposite  3d  cervical;  8,  section  of  medulla  ob- 
longata  through  centre  of  corpus  olivare. 


272 


FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 


sures,  but  by  two  furrows  on  each  side,  marking  out  three  columns  upon  Jt. 
We  have,  therefore,  on  each  half  of  the  cord,  an  anterior  middle  or  lateral 
and  posterior  column.  The  points  of  the  crescentic  lamellae  of  grey  matter 
approach  these  furrows  pretty  closely  ;  but  elsewhere  the  grey  matter  is 
covered  deeply  by  the  fibrous  columns.  Each  spinal  nerve  arises  from  two 
sets  of  roots.  The  anterior  roots  join  the  spinal  cord,  near  the  anterior  fur- 
row ;  and  the  posterior,  near  the  posterior  furrow.  Respecting  their  intimate 
connection  with  the  principal  divisions  of  the  cord,  a  considerable  diversity 
has  existed  among  the  statements  of  anatomists  ;  but  it  seems  to  be  now 
generally  admitted,  that,  as  in  the  Articulata,  a  part  of  each  root  enters  the 


[Fig.  134. 


Fig.  135. 


Transverse  section  of  human  spinal  cord,  close  to 
the  third  and  fourth  cervical  nerves  ;  magnified  ten 
diameters,  (from  Stilling;)-/.  Posterior  columns,  ii. 
Gelatinous  substance  of  the  posterior  horn.  k.  Pos- 
terior root.  I.  Supposed  anterior  roots,  a.  Anterior 
fissure,  c.  Posterior  fissure.  6.  Grey  commissure,  in 
which  a  canal  is  contained,  which,  according  to  these 
writers,  extends  through  the  length  of  the  cord.  g. 
Anterior  horn  of  grey  matter  containing  caudate  vesi- 
cles, e.  Antero-lateral  column  (from  k  to  a)]. 


Passage  of  Nerve-fibres  through  the 
Spinal  Cord,  according  to  Stilling;  A, 
posterior  fibres  continuous  with  the 
anterior  of  the  same  side,  through  the 
nucleus  of  the  cord ;  B,  posterior  fibres 
continuous  with  the  anterior  of  the 
opposite  side. 


grey  matter  or  ganglionic  portion  of  the  cord,  whilst  a  part  is  continuous 
with  its  white  or  fibrous  columns. — The  course  of  the  fibres  which  enter  the 
grey  matter,  has  been  lately  displayed,  in  part,  at  least,  by  the  researches  of 
Dr.  Stilling.*  It  appears  that  of  the  fibres  of  the  posterior  roots,  some  form 
loops  in  the  grey  matter,  and  become  continuous  with  those  of  the  anterior 
roots  of  the  same  side,  as  seen  at  A,  fig.  135.  Others  cross  the  grey  matter, 
and  become  continuous  with  those  of  the  anterior  roots  of  the  opposite  side, 
as  seen  at  B.  It  can  scarcely  be  doubted  that  these  fibres,  being  unconnected, 
with  the  brain,  constitute  the  system  to  which  reflex  actions  are  due.  Although 
Dr.  Stilling's  inquiries  have  not  proved  the  fact,t  yet  it  may  be  inferred  from 
physiological  phenomena,  as  well  as  from  the  facts  recently  shown  by  Mr. 
Newport  (§  326),  that  there  are  other  fibres,  which  pass  from  the  posterior 

*  Ueber  die  Textur  und  Function  der  Medulla  Oblongata. 

f  It  may  be  thought  that  the  mode  of  examination  which  he  adopted, — that  of  making 
very  thin  transverse  sections  of  the  Spinal  Cord, — is  not  well  fitted  to  display  the  connections 
of  the  roots  with  longitudinal  fibres.  The  subsequent  observations  of  Budge  (Muller's  Ar- 
chiv.,  1844,  p.  160),  seem  to  have  established  the  fact  of  the  continuity  of  a  portion  of  each 
root  with  the  longitudinal  fibres  of  the  cord. 


SPINAL  CORD  OF  VERTEBRATA.  273 

roots  into  the  anterior  roots  of  other  nerves  above  and  below,  both  on  the 
same  side  and  on  the  opposite. — Of  the  portions  of  the  roots  which  are  con- 
tinuous with  the  fibrous  columns,  the  anterior  would  seem  to  have  a  connec- 
tion with  both  the  anterior  and  lateral  columns  ;  and  the  posterior  cannot  be 
said  to  be  restricted  to  the  lateral  column,  some  of  their  fibres  entering  the 
posterior  division  of  the  cord. 

348.  If  the  white  or  fibrous  portion  of  the  Spinal  Cord  be  really  continu- 
ous with  the  medullary  matter  of  the  Brain,  the  roots   of  the  nerves  which 
enter  it  are  in  reality  thus  brought  into  connection  with  the  Cerebral  Hemi- 
spheres and  Cerebellum  ;  and  the  posterior  division  of  these  may,  therefore, 
be  regarded  as  conducting  to   the  Sensorium  those  impressions,  which  there 
become  sensations  ;  whilst  the  anterior  roots   convey  the  motive  influence, 
which  has  been  propagated,  by  a  voluntary  or  emotional  impulse,  down  the 
tract  of  the  Spinal  Cord  with  which  they  are  continuous.     On  the  other  hand, 
the  passage  of  one  portion  of  each  set  of  roots  through  the  grey  matter  of 
the  Cord,  completes  the  nervous  circle  required  for  the  performance  of  reflex 
actions  ;  and  by  this  they  would  seem  to  take  place  in   Vertebrated   animals, 
just  as  through  the  distinct  system   of  excito-motor  fibres   in   the  Articulata 
(§  328.)     The  fibres  which  pass  continuously  from  the  posterior  to  the  ante- 
rior roots  of  the  nerves  on  the  same  side,  probably  constitute  the  channel  of 
those  reflex  actions,  which  can  be  excited  in  apart  supplied  by  any  compound 
nerve,  by  stimulating  its  afferent  fibres,  and  thus  causing  a  motor  impulse  to 
be  transmitted  from  the  Spinal  Cord  along  its  afferent  portion.     The  fibres 
which  cross  to  the  opposite  side,  will  produce  similar  movements  in  its  cor- 
responding parts.     And  the  fibres,  if  such  there  be,  that  pass  from  the  pos- 
terior  (afferent)  roots  of  each  nerve,  into  the  anterior  (motor)  roots  of  distant 
nerves,  would  convey  to  a  great  variety  of  muscles,  the  influence  of  a  stimulus 
applied  to  a  single  afferent  nerve.     It  follows,  then,  on  this  view  of  the  cha- 
racter of  the  Spinal  Cord,  that  the  continuity  of  the  fibrous  tracts  is  all  that 
is  required,  to  convey  the  influence  of  the  brain  to  the  parts  below  ;  whilst 
the  completeness  of  the  nervous  circle  is  all  that  is  necessary,  for  the  perform- 
ance of  reflex  actions  excited  through  it.     This  is  found  to   be  strictly  true  ; 
the  former  having  been  observed  in  cases  of  disease,  and  the  latter  having 
been  proved  by  experiment.     As  far  as  simple  reflex   actions  are  concerned, 
there  is  as  much  segmental  independence  in  Vertebrata,  as  in  the  Articulata  ; 
but  these  actions  seldom  have  so  completely  the  character  of  adaptation,  and 
are  of  a  more  irregular  and  convulsive   nature.     Still,  however,  there  is  an 
essential  correspondence  between  them ;  and  we  may,  therefore,  regard  the 
distinction  between  the  reflex  and  voluntary  movements  as  the  same  in  each 
group  ;  the  former  predominating  in  Articulata  ;  the  latter  in  Vertebrata.    On 
this  view,  then,  each  spinal  nerve  contains  at  least  four  sets  of  fibres. 

i.  A  sensory  bundle  passing  upwards  to  the  Brain. 

ii.  A  motor  set,  conveying  the  influence  of  volition  and  emotion  down- 
wards/rom  the  Brain.  • 

in.  A  set  of  excitor  or  centripetal  fibres,  terminating  in  the  true  Spinal 
Cord  or  ganglion,  and  conveying  impressions  to  it. 

iv.  A  motor  or  centifrugal  set,  arising  from  the  same  Ganglionic  centre, 
and  conveying  the  motor  impulse  reflected/row  it  to  the  muscles. 

Of  these,  the  first  and  third  are  united  in  the  posterior  or  afferent  roots ; 
the  second  and  fourth  in  the  anterior  or  efferent  roots. 

349.  It  is  difficult  to  trace  the  course  of  the  fibres  within  the  Spinal  Cord; 
but  it  is  now  proved,  that  Sir  C.  Bell  was  not  altogether  correct  in  his  idea, 
that  the  functions  of  the  columns  of  the  Cord  are  respectively  similar  to  those 
of  the  roots  connected  with  them.     Cases,  indeed,  are  of  no  unfrequent  oc- 
currence, in  which  a  portion  of  one  of  the  columns  has  been  almost  entirely 


274  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

destroyed  by  injury  or  disease,  without  any  corresponding  loss  of  the  func- 
tion attributed  to  it.*  Such  cases  have  kept  alive,  in  the  minds  of  many  emi- 
nent practical  men,  a  considerable  distrust  of  the  accuracy  of  Sir  C.  Bell's 
conclusions.  We  have  seen  that,  in  regard  to  the  roots  of  the  nerves,  his 
first  statements  have  been  confirmed,  and  rendered  more  precise,  by  subse- 
quent researches ;  but  it  is  not  so  in  regard  to  the  functions  of  the  anterior 
and  posterior  divisions  of  the  Spinal  Cord. — Bellingeri  was  led,  by  experi- 
ments on  the  spinal  cord,  to  the  conclusion,  that  the  anterior  roots  of  the 
nerves  were  for  the  flexion  of  the  various  articulations,  and  the  posterior  for 
their  extension.  He  also  was  wrong,  in  extending  an  inference,  founded  on 
experiments  on  the  Cord,  to  the  roots  of  the  nerves. — The  recent  experiments 
of  Valentin,  whilst  they  fully  confirm  Sir  C.  Bell's  determination  of  the  func- 
tions of  the  roots  of  the  nerves,  coincide,  to  no  small  degree,  with  Bellingeri's 
opinion,  in  regard  to  the  offices  of  the  anterior  and  posterior  divisions  of  the 
Cord.  He  obtained  reason  to  believe  that,  in  the  Frog,  neither  the  superior 
nor  inferior  strand  of  the  cord  (posterior  and  anterior  columns  in  Man)  solely 
possesses  motor  functions ;  but  he  found  that,  when  the  former  were  irritated, 
sensations  predominated ;  and  when  the  latter,  motions  were  chiefly  excited. 
He  further  states  that,  if  the  superior  strand  (posterior  column)  be  irritated 
at  the  point  at  which  the  nerves  of  either  extremity  are  given  off,  that  ex- 
tremity is  extended ;  and  that  if  the  inferior  strand  (anterior  column)  be  irri- 
tated, the  extremity  is  flexed.  At  their  entrance  into  the  spinal  cord,  there- 
fore, it  would  appear  that  the  motor  fibres  of  the  extensors  pass  towards  the 
superior  stratum  (posterior  column  in  Man),  whilst  those  of  the  flexors  are 
continuous  with  the  inferior  stratum  (inferior  column) ;  their  course  being 
more  altered,  however,  when  they  are  examined  far  from  the  point  of  issue. 
This  doctrine  was  confirmed  by  experiments  on  Mammalia ;  and  is  borne  out 
(according  to  Valentin)  by  pathological  phenomena  observed  in  Man.  Accord- 
ing to  this  eminent  physiologist,  also,  relaxation  of  the  sphincters  is  analogous 
to  the  extended  state  of  the  extremities  ;  and  he  has  noticed  a  manifest  relaxa- 
tion of  the  sphincter  ani  in  the  frog,  when  the  superior  part  of  the  spinal 
cord  was  irritated,  so  as  to  produce  extension  of  the  limbs.  These  state- 
ments are  entitled  to  considerable  weight,  on  account  of  the  quarter  from 
which  they  come  ;  but  they  are  not,  perhaps,  to  be  received  altogether  with- 
out hesitation,  until  confirmed  by  other  physiologists,  especially  whilst  the 
phenomena  of  reflex  action  are  still  so  imperfectly  known.  For  it  is  quite 
possible  that,  whilst  stimulation  of  the  anterior  part  of  the  cord  may  excite 
direct  motions  of  flexion,  in  preference  to  those  of  extension,  the  movements 
of  extension  produced  by  stimulating  the  posterior  column  may  be  of  a  reflex 
character. 

350.  There  is  no  reason  to  believe,  that  the  functions  of  the  Spinal  Cord 
are  essentially  different  along  its  whole  length.  Everywhere  it  appears  to 
consist  of  a  ganglionic  centre,  supplying  nerves  to  its  particular  segment ; 
and  of  connecting  fibres,  by  which  the  nerves  proceeding  from  any  one  divi- 
sion are  brought  into  relation  with  distant  portions  of  the  organ,  and  with  the 
large  ganglionic  masses  at  its  anterior  extremity.  In  this  respect,  then,  it 
corresponds  precisely  with  the  double  nervous  cord  of  the  Articulata ;  the 
only  prominent  difference  between  the  two  being,  that  in  the  former  the  gan- 
glionic matter  is  continuous  from  one  extremity  of  the  organ  to  the  other; 
whilst  in  the  latter  it  is  interrupted  at  intervals ;  and  in  the  Mollusca,  the 
centres  are  still  further  separated  from  each  other.  The  connection  of  the 

*  See  especially  a  case  recorded  by  Dr.  Webster  (Medico-Chirurgical  Transactions,  vol . 
xxvi.),  in  which  there  was  complete  destruction  of  the  posterior  columns  in  the  lower  part 
of  the  cervical  region  ;  which  was  not  attended  with  loss  of  sensibility  in  the  parts  below, 
but,  on  the  contrary,  with  loss  of  power  of  voluntary  motion. 


SPINAL  CORD  OF  VERTEBRATA. 


275 


Spinal  Cord  with  the  large  ganglia 
contained  within  the  cavity  of  the 
cranium,  is  effected  by  means  of 
processes  from  its  superior  extre- 
mity, the  arrangement  of  which  is 
somewhat  complex.  This  portion 
of  the  cord,  which  also  lies  within 
the  cavity  of  the  cranium,  has  been 
termed  the  Medulla  Oblongata. 
It  has  been  supposed  to  be  the 
peculiar  seat  of  vitality ;  but  the 
only  real  foundation  of  this  idea 
is,  that  it  is  the  great  centre  of  the 
Respiratory  actions,  on  the  conti- 
nuance of  which  all  the  other 
functions  are  dependent.  The 
Brain  may  be  removed  from  above, 
and  nearly  the  whole  Spinal  Cord 
from  below,  without  an  immediate 
check  being  put  upon  all  the  phe- 
nomena of  life.  In  this  Medulla 
Oblongata,/owr  different  parts  may 
be  distinguished  on  each  side: — 1, 
The  Anterior  Pyramids,  or  Cor- 
pora Pyramidalia;  2,  The  Oli- 
vary Bodies,  or  Corpora  Oliva- 
ria;  3,  The  Restiforrn  bodies,  or 
Corpora  Restiformia ;  otherwise 
called  Processus  a  Cerebello  ad 
Medullam  Oblongatam;  4,  The 

[Fig.  137. 


[Fig.  136. 


A  posterior  superior  view  of  the  Pons  Varolii,  the 
Cerebellum,  and  the  Medulla  Oblongata  and  Spinalis. 
1,1,  the  crura  cerebrij  2,  the  pons  varolii  or  tuber- 
annularis;  3,  its  middle  fossa;  4,  an  oblique  band  of 
medullary  matter  seen  passing  from  its  side  ;  5,  the 
external  surface  of  the  crus  cerebelli  in  its  natural 
state  ;  6,  the  same  portion  deprived  of  outer  layer  ;  7, 
the  nervous  matter  which  united  it  to  4;  8,  the  trige- 
minus  or  fifth  pair  of  nerves  ;  9,  portion  of  the  audi- 
tory nerve—  the  white  neurine  is  seen  passing  from 
the  oblique  band  which  comes  from  the  corpus  resti- 
forme  to  the  trigeminus  nerve  in  front,  and  the  auditory 
nerve  behind  ;  10,  11,  the  superior  portion  of  the  hemi- 
spheres of  the  cerebellum;  12,  lobulus  amygdaloides  ; 
13,  corpus  olivare  ;  14,  corpus  pyramidale  ;  15,  medulla 
spinalis.] 


[Fig.  138. 


Front  view  of  the  medulla  oblon- 
gata :— p,  p.  Pyramidal  bodies,  de- 
cussating at  d.  0,0.  Olivary  bodies. 
r,  r.  Restiform  bodies,  a,  a.  Arci- 
form  fibres,  v.  Lower  fibres  of  the 
Pons  Varolii.] 


Posterior  view  of  the  medulla  oblongata  :—pp.  Posterior 
pyramids,  separated  by  the  posterior  fissure,  rr.  Restiform 
bodies,  composed  of  cc,  posterior  columns,  and  dd,  lateral 
part  of  the  antero-lateral  columns  of  the  cord.  aa.  Olivary 
columns,  as  seen  on  the  floor  of  the  fourth  ventricle,  sepa- 
rated by  s,  the  median  fissure,  and  crossed  by  some  fibres 
of  origin  of  nn,  the  seventh  pair  of  nerves.] 


276 


FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 


Posterior  Pyramids,  or  Corpora  Pyramidalia  Posteriora.  The  connections 
of  these  with  the  Brain  above,  and  with  the  Spinal  Cord  below,  will  be  now 
traced.* 

[Fig.  139. 


Transverse  section  of  the  medulla  oblongata  through  the  lower  third  of  the  olivary  bodies.  (From  Stil- 
ling.) Magnified  4  diameters. 

a.  Anterior  fissure,  b.  Fissure  of  the  calamus  scriptorius.  c.  Raphe".  d.  Anterior  columns,  e.  La- 
teral columns.  /.  Posterior  columns,  g  Nucleus  of  the  hypoglossal  nerve,  containing  large  vesicles. 
A.  Nucleus  of  the  vagus  nerve,  i,  i.  Gelatinous  substance.  &,&.  Roots  of  the  vagus  nerve.  I.  Roots  of 
the  hypoglossal,  or  ninth  nerve,  m.  A  thick  bundle  of  white  longitudinal  fibres  connected  with  the  root 
of  the  vagus,  n.  Soft  column  (Zartstrang,  Stilling),  o.  Wedge-like  column  (Keelstrang,  Stilling),  p. 
Transverse  and  arciform  fibres,  q.  Nucleus  of  the  olivary  bodies,  r.  The  large  nucleus  of  the  pyramid, 
s,  s,  s.  The  small  nuclei  of  the  pyramid,  u.  A  mass  of  grey  substance  near  the  nucleus  of  the  olives 
(Oliven-Nebenkern).  u.  q,  r,  are  traversed  by  numerous  fibres  passing  in  a  transverse  semicircular  direc- 
tion, v,  w.  Arciform  fibres,  x.  Grey  fibres.] 

351.  As  our  object,  however,  is  rather  Physiological  than  purely  Anato- 
mical, we  shall  commence  with  a  description  of  the  motor  and  sensory  tracts, 
which  may,  according  to  Sir  C.  Bell,t  be  very  distinctly  separated  in  the  Pons 

*  Great  diversities  will  be  found  in  the  accounts  given  of  those  connections  by  different 
Authors ;  some  of  which  are  attributable  to  a  variation  in  the  use  of  terms,  which  must  not 
pass  unnoticed.  By  the  majority  of  Anatomists,  the  name  of  Corpora  Restiformia  is  given  to 
the  Cerebellar  Columns;  and  its  designation,  therefore,  it  seems  advisable  to  retain.  Some, 
however,  and  amongst  them  Dr.  J.  Reid,  in  his  late  very  excellent  description  of  the  Ana- 
tomy of  the  Medulla  Oblongata  (Edinb.  Med.  &  Surg.  Journal,  Jan.  1841),  give  the  name  to 
the  columns  that  pass  up  from  the  posterior  division  of  the  spinal  cord  into  the  crus  cerebri, 
— which  are  here  called  (after  Sir  C.  Bell)  the  posterior  pyramids;  and  apply  the  terms 
Posterior  Pyramids  to  the  Cerebellar  column.  The  truth  is  that,  as  Sir  C.  Bell  has  justly 
observed,  all  the  tracts  of  fibrous  matter  connecting  the  Brain  with  the  Spinal  Cord,  have  a 
somewhat  pyramidal  form  ;  and  it  might  be  added  that  all  have  something  of  a  restiform  or 
cord-like-aspect. 

f  Philosophical  Transactions,  1835. 


STRUCTURE  AND  CONNECTIONS  OF  MEDULLA  OBLONGATA. 


277 


Varolii.  The  Pons  has  been  correctly  designated  as  the  great  Commissure 
of  the  Cerebellum,  inclosing  the  Crura  Cerebri;  and  its  transverse  fibres  not 
only  surround  the  longitudinal  bands  which  connect  the  Cerebrum  with  the 
Spinal  Cord,  but  pass  through  them  ;  so  as  in  some  degreee  to  isolate  the 

Fig.  140. 


Course  of  the  Motor  tract,  according  to  Sir  C.  Bell.  A,  A,  fibres  of  the  hemispheres,  converging  to  form 
the  anterior  portion  of  the  crus  cerebri ;  B,  the  same  tract  where  passing  the  crus  cerebri ;  c,  the  right 
pyramidal  body,  a  little  above  the  point  of  decussation  ;  D,  the  remaining  part  of  the  pons  Varolii,  a  por- 
tion having  been  dissected  off  to  expose  B.—l,  olfactory  nerve,  in  outline;  2,  union  of  optic  nerves; 
3.  motor  oculi ;  4,  4,  patheticus  ;  5,  5,  trigeminus ;  6,  6,  its  muscular  division ;  7, 7,  its  sensory  root ;  8,  ori- 
gin of  sensory  root  from  the  posterior  part  of  the  medulla  oblongata ;  9,  abducens  oculi ;  10,  auditory 
nerve  ;  11,  facial  nerve  ;  12,  eighth  pair ;  13,  hypoglossal ;  14,  spinal  nerves ;  15,  spinal  accessory  of  right 
side,  separated  from  par  vagum  and  glosso-pharyngeal. 

two  lateral  halves  from  one  another,  and  to  form  a  complete  septum  between 
the  anterior  and  posterior  portions  of  each.  The  Motor  tract  is  brought  into 
view,  by  simply  raising  the  superficial  layer  of  the  Pons,  and  tracing  upwards 
and  downwards  the  longitudinal  fibres  which  then  present  themselves.  It  is 
24 


278  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

then  found,  that  these  fibres  may  be  traced  upwards,  chiefly  into  the  Corpora 
Striata,  whence  they  radiate  to  the  Hemispheres  ;  and  downwards,  chiefly  into 
the  Anterior  Pyramids.  From  this  tract  arise  all  the  Motor  nerves  usually 
reckoned  as  Cranial;  as  will  be  seen  in  the  accompanying  Figure. — The 
Sensory  tract  is  displayed,  by  opening  the  Medulla  Oblongata  on  its  posterior 
aspect ;  and  then  separating  and  turning  aside  the  Restiform  Columns,  so  as 
to  bring  into  view  the  Posterior  Pyramids,  which  lie  on  the  outside  of  the  ca- 
lamus scriptorius.  On  tracing  their  fibres  upwards,  it  is  found  that  they  form 
a  part  of  the  posterior  layer  of  the  Crura  Cerebri,  ultimately  passing  on  to  the 
Thalami  optici,  whence  they  radiate  to  the  Hemispheres.  From  this  tract, 
no  motor  nerves  arise ;  but  on  tracing  it  downwards  into  the  Spinal  Cord,  it 
is  found  that  the  sensory  root  of  the  fifth  pair  terminates  in  it,  and  that  the 

Fig.  141. 


Course  of  the  Sensory  tract  according  to  Sir  C.  Bell.  A.  Pons  Varolii :  B,  B,  sensory  tract  separated  ; 
c,  union  and  decussation  of  posterior  columns ;  D,  D,  posterior  roots  of  spinal  nerves ;  E,  sensory  roots  of 
fifth  pair. 

posterior  roots  of  the  spinal  nerves  are  evidently  connected  with  its  continua- 
tion. Also  forming  part  of  the  posterior  division  of  the  crus  cerebri,  and  se- 
parated from  the  anterior  by  the  transverse  septum,  is  a  layer  of  fibres  which 
ascends  from  the  Olivary  bodies,  some  of  which  terminate  in  the  Corpora 
Quadrigemina. 

352.  On  tracing  upwards  the  four  divisions  of  the  Medulla  Oblongata,  the 
following  are  found  to  be  their  chief  connections  with  the  Brain. — 1.  The 
fibres  of  the  Anterior  Pyramids  for  the  most  part  enter  thevCrura  Cerebri, 
passing  through  the  Pons  Varolii,  and  traversing  the  Optic  Thalami  (which, 
it  must  be  carefully  borne  in  mind,  have  scarcely  any  real  connection  with 
the  Optic  Nerves,  or  with  the  sense  of  sight) ;  after  which  they  diverge  and 
become  intermingled  with  grey  matter,  thus  forming  the  Corpora  Striata,  and 
finally  radiate  to  the  convolutions  of  the  Cerebrum. — 2.  The  fibres  of  the 
Olivary  body  also  pass  into  the  Pons  Varolii,  and  there  divide  into  two  bands  ; 


STRUCTURE  AND  CONNECTIONS  OF  MEDULLA  OBLONGATA. 


279 


of  which  one  proceeds  upwards  and  forwards  to  join  the  Crus  Cerebri, 
thence  to  pass  to  the  Optic  Thalami ;  whilst  the  other  passes  upwards  and 
backwards  into  the  Corpora  Quadrigemina. — 3.  Of  the  true  Restiform  bodies, 
the  fibres  pass  entirely  into  the  Cerebellum. — 4.  Finally,  of  the  Posterior 
Pyramids,  the  fibres  pass  directly  onwards  through  the  Crura  Cerebri  into 
the  Thalami,  whence  they  radiate  to  the  convolutions. 

353.  The  downward  course  of  these  fibres  into  the  Spinal  Cord  now  re- 
mains to  be  traced;  and  their  arrangement  is  by  no  means  a  simple  one. — 1. 
The  Anterior  Pyramids  decussate,  as  is  well  known,  at  their  lower  extremity ; 

[Fig.  142. 


Analytical  diagram  of  the  encephalon— in  a  vertical  section.    (After  Mayo.) 

s.  Spinal  cord.  r.  Restiform  bodies  passing  to,  c  the  cerebellum,  d.  Corpus  dentatum  of  the  cerebel- 
lum, o.  Olivary  body.  f.  Columns  continuous  with  the  olivary  bodies  and  central  part  of  the  medulla 
oblongata,  and  ascending  to  the  tubercular  quadrigemina  and  optic  thalami.  p.  Anterior  pyramids,  v. 
Pons  Varolii.  n,  b.  Tubercular  quadrigemina.  g.  Geniculate  body  of  the  optic  thalamus.  t.  Pro- 
cessus  cerebelli  ad  testes.  a.  Anterior  lobe  of  the  brain,  q.  Posterior  lobe  of  the  brain.] 

the  principal  part  (but  not  the  whole)  of  the  fibres  on  each  side,  passing  over 
to  the  other.  The  decussating  fibres  pass  backwards  as  well  as  downwards, 
and  enter,  not  the  anterior  column  of  the  spinal  cord,  (as  commonly  stated,) 
but  the  lateral  column.  The  smaller  bundle  of  fibres,  which  do  not  decus- 
sate, passes  downwards,  along  with  those  of  the  olivary  bodies,  to  form  the 
anterior  column. — 2.  The  fibres  descending  from  the  Olivary  bodies  converge 


280  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

as  those  of  the  pyramids  pass  backwards  from  between  them,  until  they  meet 
on  the  median  line,  forming  the  greater  part  of  the  anterior  column.  —  3.  The 
fibres  of  the  Restiform,  or  Cerebellar  columns,  —  which,  like  those  of  the 
Olivary  columns,  do  not  decussate,  mostly  pass  downwards  into  the  posterior 
columns  ;  but  a  band  (which  has  been  termed,  from  its  curved  aspect,  the 
arciform  layer)  passes  forwards  into  the  anterior  columns  :  and  another 
small  fasciculus  enters  the  lateral  columns.  —  4.  The  fibres  of  the  Posterior 
Pyramids  are  stated  by  Sir  C.  Bell  to  decussate  like  those  of  the  anterior; 
they  pass  down  chiefly  into  the  posterior  part  of  the  lateral  column,  forming 
part  also  of  the  posterior. 

354.  The  following  tabular  view  may  assist,  better  than  any  delineations 
could  do,  in  the  comprehension  of  this  very  intricate  piece  of  Anatomy  ;  the 
knowledge  of  which  can  be  readily  applied  to  the  explanation  of  many  curious 
pathological  phenomena,  and  cannot  but  assist  in  the  elucidation  of  others, 
whose  rationale  is  as  yet  obscure. 

SPIRAL  CORD.  MEDULLA  OBLONGATA.  BRAIX. 

(  Arciform  fibres  of  Cerebellar  Columns     .         .  )  Cerebellum 
Anterior  Column  <  Olivary  Columns      ......  $  Corpora  Quadrigemina 

Non-decussating  portion  of  Ant.  Pyramids       .  )  r  <>    • 

' 


355.  The  Medulla  Oblongata  is  not  to  be  viewed,  however,  solely  as  a  series 
of  connecting  bands  or  commissures,  between  the  Brain  and  Spinal  Cord;  for 
it  contains  vesicular  matter  of  its  own,  in  virtue  of  which  it  serves  as  a  gan- 
glionic  centre  to  nerves  that  are  specially  connected  with  it.     The  vesicular 
matter  is  partly  found  in  a  situation  corresponding  to  that  which  it  occupies 
in  the  spinal  cord  ;  and  it  forms  a  tract,  which  is  continuous  above  with  the 
grey  nucleus  of  the  Corpora  Quadrigemina,  and  below  with  that  of  the  Spinal 
Cord  ;  and  which  is  opened  out  to  view  (as  it  were)  on  the  floor  of  the  fourth 
ventricle,  forming  the  calamus   scriptorius.     Besides   this   central  portion, 
there  are  other  outlying  masses,  which  are  continuous  with  it.     Thus  the 
bulk  of  the  Olivary  body  is  principally  due  to  the  presence  of  a  ganglionic 
mass  in  its  interior  ;  inclosed  in  the  fibres  of  which   the   olivary  column  is 
composed,  and  which,  for  the  most  part,  pass  over  and  around  it  without  en- 
tering it.     This  mass  consists  of  a  layer  of  grey  matter,  spread  in  a  thin  pli- 
cated stratum  over  a  centre  of  white  substance,  and  altogether  forming  what 
is  known  as  t^je  corpus  dentatum.     There  is  a  considerable  amount  of  ve- 
sicular substance  in  the  Restiform  bodies  also  ;  and  this  is  continuous  with 
the  grey  matter  forming  the  posterior  cornua  in  the  Spinal  Cord. 

356.  We  have  now  to  inquire  into  the  character  of  the  ganglionic  masses, 
which  form,  with  the  Medulla  Oblongata,  the  Encephalon  of  Vertebrated  ani- 
mals.    We  should  be  liable  to  form  a  very  erroneous  conception  of  the  rela- 
tive importance,  and  of  the  real  nature,  of  these,  if  we  were  to  study  them 
only  in  the  Brain  of  Man  and  of  the  higher  animals  ;  for  the  great  develop- 
ment of  their  Cerebrum  and  Cerebellum  throws  into  the  shade  (so  to  speak) 
certain  other  ganglionic  centres,  which  constitute  yet  more  essential  parts  of 
the  nervous  apparatus.     It  is  one  of  the  most  interesting  results  of  the  com- 
parison of  the  Human  Brain  with  that  of  the  lower  tribes  of  Vertebrata,  that 
the  great  change  in  the  relative  proportions  of  the  parts,  which  we  encounter 
in  the  latter,  makes  evident  the  real  nature  and   importance  of  what  would 
otherwise  have  been  considered  as  subordinate  appendages  :  whilst,  at  the 
same  time,  they  afford  us  the  connecting  links,  by  which  we  are  enabled 
to  trace  the  real  analogies  of  the  different  parts  of  the  Encephalon  with  the 
ganglionic  masses  which  represent  it  among  Invertebrated  animals. 


ENCEPHALON  OF  FISHES. 


281 


357.  Commencing  with  FISHES,  we  find  a  series  of  four  distinct  ganglionic 
masses,  arranged  in  a  line  which  is  nearly  continuous,  from  behind  forwards, 
with  that  of  the  Spinal  Cord ;  of  these,  the  posterior  is  usually  single,  and 
on  the  median  plane,  whilst  the  others  are  in  pairs.  The  posterior,  from  its 
position  and  connections,  is  evidently  to  be  regarded  in  the  light  of  a  Cere- 
bellum ;  and  it  bears  a  much  larger  proportion  to  the  rest,  in  this  class,  than 
in  any  other.  The  pair  in  front  of  this  are  not  the  hemispheres  of  the  Ce- 
rebrum, as  their  large  size  in  some  instances  (the  Cod  for  instance)  might 
lead  us  to  suppose ;  but  they  are  immediately  connected  with  the  Optic  nerve, 
which,  in  fact,  terminates  in  them,  and  are  therefore  to  be  considered  (like  the 
chief  part  of  the  cephalic  masses  of  Invertebrated  animals)  as'  Optic  Ganglia. 
In  front  of  these  are  the  Cerebral  Hemispheres,  which  are  small,  generally 
destitute  of  convolutions,  and  possess  no  ventricle  in  their  interior, — except 
in  the  Sharks  and  Rays,  in  which  they  are  much  more  highly  developed  than 
in  the  Osseous  Fishes.  Anterior  to  these  is  another  pair  of  ganglionic  en- 
largements, from  which  the  Olfactory  nerves  arise ;  and  these  are,  therefore, 
correctly  designated  as  the  Olfactive  tubercles  or  ganglia.  In  some  instances, 
these  ganglia  are  not  immediately  seated  upon  the  prolonged  spinal  cord,  but 
are  connected  with  it  by  long  peduncles ;  this  is  the  case  in  the  Sharks ;  and 
we  are  thus  led  to  perceive  the  real  nature  of  the  portion  of  the  trunk  of  the 
Olfactory  nerve  in  Man,  which  lies  within  the  cranium,  and  of  its  bulbous 
expansion  on  the  Ethmoid  bone.  Besides  these  principal  ganglionic  enlarge- 
ments, there  are  often  smaller  ones,  with  which  other  nerves  are  connected. 
Thus,  in  the  Shark,  we  find  a  pair  of  tubercles  of  considerable  size,  at  the 
origin  of  the  Trifacial  nerves  ;  and  another  pair,  in  most  Fishes,  at  the  roots 
of  the  Vagi.  In  some  instances,  too,  distinct  Auditory  ganglia  present  them- 
selves ;  as  in  the  Carp. 


Pike. 


Cod. 


Fig.  143. 


Fox- shark. 


Brains  of  Fishes.  A.  olfactive  lobes  or  ganglia;  B,  cerebral  hemispheres ;  c,  optic  lobes  ;  D,  cerebel- 
lum ;  ol,  olfactory  nerve  ;  op,  optic  nerve ;  pa,  pathelicus ;  »no,  motor  oculi ;  a&,  abducens ;  tri,  trifacial ; 
/a,  facial ;  vag,  vagus  ;  «,  tubercles  or  ganglia  of  the  trifacial ;  «w,  tubercles  of  the  vagus. 

358.  The  Optic  Lobes  of  Fishes  have  no  analogy  whatever  with  the  Tha- 
lami  optici  of  Mammalia  ;  the  connection  of  which,  with  the  Optic  nerves,  is 

24* 


282  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

very  slight.  They  are  rather  to  be  compared  with  the  Tubercula  Quadri- 
gemina,  which  are  the  real  ganglia  of  the  Optic  nerve.  Their  analogy  is  not 
so  complete,  however,  to  these  bodies  in  the  fully  formed  Brain  of  Man,  as 
it  is  to  certain  parts  which  occupy  their  place  at  an  earlier  period.  The  Third 
Ventricle,  which  is  quite  distinct  from  the  Corpora  Quadrigemina,  is  hollowed 
out,  as  it  were,  from  the  floor  of  the  Optic  Lobes  of  Fishes ;  and  the  Anterior 
Commissure  bounds  its  front;  hence  these  must  be  considered  as  analogous 
to  the  parts  surrounding  the  Third  Ventricle,  as  well  as  to  the  Corpora  Quad- 
rigemina. This  is  made  evident  by  the  fact,  observed  by  Miiller,  that,  in  the 
Lamprey,  there  is  a  distinct  Lobe  of  the  third  ventricle,  replacing  the  Optic 
Lobes  of  other  Fishes,  and  partly  giving  origin  to  the  optic  nerves ;  and  a 
separate  vesicle,  analogous  to  the  Corpora  Quadrigemina.  With  this  condition, 
the  early  state  of  the  Brain  in  the  embryo  of  the  Bird  and  Mammiferous  ani- 
mal, and  even  in  Man  himself,  bears  a  very  close  correspondence.  The  En- 
cephalon  consists  at  this  time  of  a  series  of  vesicles,  arranged  in  a  line  with 

each  other,  of  which  those  that  represent 

Fig.  144.  the  Cerebrum  are  the  smallest,  whilst  that 

which  represents  the  Cerebellum  is  the 
largest.  The  latter,  as  in  Fishes,  is  single, 
covering  the  fourth  ventricle  on  the  dorsal 
surface  of  the  Medulla  Oblongata.  Ante- 
rior to  this,  is  the  single  vesicle  of  the 
Corpora  Quadrigemina,  from  which  the 
Optic  nerve  chiefly  arises;  this  has  in  its 
interior  a  cavity,  the  ventricle  of  Sylvius, 
which  exists  even  in  the  adult  Bird,  where 
the  Corpora  Quadrigemina  are  pushed,  as 
it  were,  from  each  other  by  the  increased 
development  of  the  Cerebral  hemispheres. 
In  front  of  this  is  the  vesicle  of  the  Third 
Ventricle,  which  contains  also  the  Thala- 
T'  »  Development  proceeds  this  like 
6,  vesicle  of  cerebral  hemi-  the  preceding,  is  covered  by  the  enlarged 

spheres;    c,  vesicle  of  thalami  optici  and        hemispheres  ;      whilst    its     roof    becomes 

third  ventricle ;  rf,  vesicle  for  cerebellum      cleft  anteriorly  on  the  median  line,  so  as 

and  medulla  oblongata;  e,  auditory  vesicle  ;  ^  form  tfae  anterior  entrance  to  the  Cavity. 
f,  olfactory  fossa ;  h,  liver;  **  caudal  extre-  ^  .,,  ,  .  .,  j  ,  •  •  i 

mity  Still  more  anteriorly  is  the  double  vesicle, 

which  represents  the  hemispheres  of  the 

Cerebrum  ;  this  has  a  cavity  on  each  side,  the  floor  of  which  is  formed  by  the 
corpora  striata.  The  cavity  of  the  cerebral  vesicles  has  at  first  no  opening, 
except  into  that  of  the  third  ventricle;  at  a  later  period  is  formed  that  fissure 
on  the  inferior  and  posterior  side,  which  (under  the  name  of  the  fissure  of 
Sylvius)enables  the  membranes  enveloping  the  brain  to  be  reflected  into  the 
lateral  ventricles. 

359.  Thus  it  will  be  seen  that  the  real  analogy  between  the  brain  of  the 
Human  foetus,  and  that  of  the  adult  Fish,  is  not  so  close  as,  from  the  resem- 
blance in  their  external  form,  might  have  been  supposed.  In  the  small  pro- 
portion which  the  Cerebral  Hemispheres  bear  to  the  other  parts,  there  is  evi- 
dently a  very  close  correspondence  ;  and  this  extends  also  to  the  general 
simplicity  of  their  structure,  the  absence  of  convolutions,  and  the  deficiency  of 
commissures.  But  there  is  a  much  nearer  analogy  between  the  foetal  brain 
of  the  Fish,  and  ihefostal  brain  of  the  Mammal ;  indeed,  at  the  earliest  period 
of  their  formation,  they  could  not  be  distinguished  ;  during  their  advance  to  the 
permanent  condition,  however,  each  undergoes  changes,  which  are  so  much  more 
decided  in  the  higher  animals  than  in  the  lower,  that  in  the  latter  there  seems 
but  little  departure  from  the  foetal  condition,  whilst  in  the  former  the  condition 


ENCEPHALON  OF  REPTILES  AND  BIRDS.  283 

appears  entirely  changed.  Hence  it  is  not  correct  to  assert,  as  is  frequently 
done, — that  the  Brain,  or  any  other  organ,  in  the  higher  animals,  passes 
through  a  series  of  forms,  which  are  parallel  to  the  permanent  forms  of  the 
same  organ  in  different  parts  of  the  animal  scale  ;  since  the  fact  is  rather,  that 
the  more  nearly  all  are  traced  back  to  their  first  origin,  the  closer  will  their 
conformity  be  found  to  be  ;  the  subsequent  development  of  each  taking  place 
not  only  in  various  degrees,  but  in  different  modes  or  directions ;  so  that  the 
resemblances  presented  by  the  higher,  at  different  epochs  of  their  evolution, 
to  the  permanent  conditions  of  the  lower,  are  often  far  from  being  complete.* 
This  we  have  seen  to  be  the  case  in  the  present  instance  ;  the  vesicle  of  the 
Corpora  Quadrigemina,  and  that  of  the  third  Ventricle,  uniting  to  form  the 
Optic  Lobes  of  Fishes,  whilst  in  the  higher  Vertebrata  they  remain  distinct ; 
so  that  there  is  no  single  part,  with  which  the  Optic  Lobes  can  be  properly 
compared,  either  in  the  foetal  or  perfect  state  of  the  Human  Brain. 

360.  The  Brain  of  REPTILES  does  not  show  any  considerable  advance  in 
its  general  structure  above  that  of  Fishes ;  but  the  Cerebral  Hemispheres  are 
usually  much  larger  in  proportion  to  the  Optic  lobes  ;  whilst  the  Cerebellum 
is  smaller.  The  very  low  development  of  the  Cerebellum  is  especially  seen 
in  the  Frog  (Fig.  132),  in  which  it  is  so  small  as  not  even  to  cover-in  the 
Fourth  Ventricle;  but  it  is  common  to  nearly  the  whole  group.  The  defi- 
ciency in  commissures  still  exists  to  a  great  extent.  The  anterior  Commissure 
in  front  of  the  third  ventricle,  is  the  only  uniting  band  which  can  be  distinctly 
traced  in  Fishes ;  and  Reptiles  have,  in  addition  to  this,  a  layer  of  uniting 
fibres  which  may  be  compared  to  the  Fornix ;  but  as  yet,  there  is  no  vestige 
of  a  true  Corpus  Callosum,  or  great  transverse  commissure  of  the  hemi- 
spheres. The  distinction  between  the  tubercula  quadrigemina,  and  the  parts 
inclosing  the  third  ventricle,  is  more  obvious  than  in  Fishes  ;  in  fact  the  Optic 
ganglia  of  Reptiles  correspond  pretty  closely  with  the  Vesicle  of  the  tubercula 
quadrigemina  in  the  brain  of  the  fetal  Mammal. 

Fig.  145.  Fig.  146. 


Brain  of  Turtle;  A,  olfactive  Brain  of  Buzzard;  the  olfactive  ganglia 

ganglia;      B,  cerebral   hemi-  are  concealed  beneath  B,  the  hemispheres; 

spheres;  c,  optic  ganglia;  D,  c,  optic  ganglia;  D,  cerebellum ;  g,  pineal 

cerebellum.  gland 

*  For  a  fuller  examination  of  this  interesting  question,  see  General  and  Comparative  Phy- 
siology, §  244. 


284 


FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 


361.  This  is  still  more  evident  in  BIRDS,  in  whose  Encephalon  the  Tuber- 
cula  Quadrigemina  or  Optic  Ganglia,  and  the  Thalami  with  their  included 
ventricle,  are  obviously  very  distinct  parts.  The  Cerebral  Hemispheres 
attain  a  great  increase  of  development,  and  arch  backwards,  so  as  partly  to 
cover  the  Optic  ganglia  ;  and  these  are  separated  from  one  another,  and  thrown 
to  either  side.  The  Cerebellum  also  is  much  increased  in  size,  proportion- 
ably  to  the  Medulla  Oblongata  and  its  ganglia ;  and  it  is  sometimes  marked 
with  transverse  lines,  which  indicate  the  intermixture  of  grey  and  white  mat- 
ter in  its  substance  ;  there  is  as  yet,  however,  no  appearance  of  a  division 
into  hemispheres.  On  drawing  apart  the  hemispheres  of  the  Cerebrum,  the 
Corpora  Striata,  Optic  Thalami,  and  Tubercula  Quadrigemina  or  Optic  Gan- 
glia, are  seen  beneath  them ;  the  size  of  the  last  still  bears  a  considerable  pro- 
portion to  that  of  the  whole  Encephalon.  The  Optic  Ganglia  are  still  hollow, 
as  they  are  in  the  embryo  condition  of  Man.  Indeed  the  Brain  of  the  Human 
foetus  about  the  twelfth  week  will  bear  comparison,  in  many  respects,  with 
that  of  the  Bird.  The  Cerebral  hemispheres,  much  increased  in  size,  and 
arching  back  over  the  Thalami  and  Optic  ganglia,  but  destitute  of  convolutions, 
and  imperfectly  connected  by  commissures, — the  large  cavity  still  existing  in 

Fig.  147. 


Fig.  148. 


Brain  of  Human  Embryo  at  twelfth  week.  A,  seen  from  behind  ;  B,  side  view ;  c,  sectional  view ;  a, 
corpora  quadrigemina;  bb,  hemispheres;  d,  cerebellum; -e,  medulla  oblongata ; ./,  optic  thalamus;  g, 
floor  of  third  ventricle;  i,  olfactory  nerve., 

the  Optic  ganglia,  and  freely  communicating  with  the  third  ventricle, — and 
the  imperfect  evolution  of  the  Cerebellum, — make  the  correspondence  in  the 
general  condition  of  the  two  very  considerable. 

362.  The  Brain  of  the  lowest  MAMMALIA  presents  but  a  slight  advance 

upon  that  of  Birds,  in  regard  both  to  the  rela- 
tive proportions  of  its  parts,  and  to  their  degree 
of  development.  Thus,  in  the  Marsupialia,  the 
Cerebral  hemispheres  exhibit  no  convolutions ; 
and  the  great  transverse  commissure, — the 
Corpus  Callosum, — is  deficient.  There  is  gra- 
dually to  be  noticed,  however,  in  ascending  the 
scale,  a  backward  prolongation  of  the  Cerebral 
hemispheres ;  so  that  first  the  Optic  ganglia, 
and  then  the  Cerebellum,  are  covered  by  them. 
The  latter  partly  shows  itself,  however,  in  all 
but  the  Quadrumana,  when  we  look  at  the 
brain  from  above  downwards;  in  the  Rabbit, 
which  is  in  this  respect  among  the  lowest  of 
the  true  Viviparous  Mammalia,  nearly  the 
whole  of  the  Cerebellum  is  uncovered.  In 
proportion  to  the  increase  of  the  Cerebral 
hemispheres,  there  is  a  diminution  in  the  size 
of  the  ganglia  immediately  connected  with  the 
organs  of  sense ;  and  this  in  comparison,  not 
only  with  the  rest  of  the  Encephalon,  but  even 


Brain  of  Squirrel,  laid  open ;  the 
hemispheres,  B,  being  drawn  to  either 
side  to  show  the  subjacent  parts;— c, 
the  optic  lobes ;  D,  cerebellum ;  thai, 
thalamus  opticus ;  cs,  corpus  striatum. 


ENCEPHALON  OF  MAMMALIA. 


285 


with  the  Spinal  Cord ;  so  that  in  Man  the  Tubercula  Quadrigemina  are  abso- 
lutely smaller  than  they  are  in  many  animals  of  far  inferior  size.     The  inter- 
Fig.  149. 


Upper  and  under  surface  of  Brain  of  Rabbit,  A,  B,  D,  as  before  ;  oJ,  olfactive  lobes;  op,  optic  nerve  ; 
mo,  motor  oculi ;  cm,  corpora  mamillaria;  cc,  crus  cerebri ;  pv,  pons  varolii ;  pa,  patheticus;  tri,  trifa- 
cial ;  ab,  abducens ;  fac,  facial ;  au,  auditory ;  vag,  vagus  ;  s,  spinal  accessory ;  hyp,  hypoglossal. 

nal  structure  of  the  hemispheres  becomes  more  complex,  in  the  same  propor- 
tion as  their  size  and  the  depth  of  the  convolutions  increase;  and  in  Man  all 
these  conditions  present  themselves  in  a  far  higher  degree,  than  in  any  other 
animal.  In  fact  it  is  only  among  the  Ruminantia,  Pachydermata,  Carnivora, 
and  Quadrumana,  that  regular  convolutions  can  be  said  to  exist.  The  cor- 
respondence between  the  bulbous  expansion  of  the  Olfactive  Nerves  in  Mam- 
malia, and  the  Olfactive  lobes  of  the  lower  Vertebrata,  is  made  evident  by  the 
presence,  in  both  instances,  of  a  cavity  which  communicates  with  the  lateral 
ventricle  on  each  side  ;  it  is  in  Man  only  that  this  cavity  is  wanting.  The 
external  form  of  the  Corpora  Quadrigemina  of  Mammalia,  differs  from  that  of 
the  Optic  ganglia  of  Birds,  owing  to  the  division  of  the  former  into  anterior 
and  posterior  eminences,  (the  nates  and  testes ;)  and  there  is  also  an  internal 
difference,  occasioned  by  the  contraction  of  the  cavity  or  ventricle,  which  now 
only  remains  as  the  Aqueduct  of  Sylvius.  The  Cerebellum  is  chiefly  re- 
markable for  the  development  of  its  lateral  parts  or  hemispheres ;  the  central 
portion,  sometimes  called  the  vermiform  process,  is  relatively  less  developed 
than  in  the  lower  Vertebrata,  in  which  it  forms  the  whole  of  the  organ. 

4.   General  Functions  of  the  Spinal  Cord. — Reflex  Action. 

363.  The  functions  of  the  Nervous  System  in  Vertebrated  Animals  are  so 
complex  in  their  nature,  and  our  means  of  analyzing  them  are  so  imperfect, 
that  the  inquiry  is  confessedly  one  of  the  greatest  difficulty,  and  needs  all  the 
light  which  can  be  thrown  upon  it  from  any  source.  The  great  accession  to 
our  knowledge  of  them,  which  has  been  made  within  the  last  few  years, 
chiefly  by  the  labours  of  Sir  C.  Bell,  and  Dr.  M.  Hall,  has  so  far  changed 
the  aspect  of  this  department  of  Physiological  Science,  as  to  render  it  neces- 
sary for  those  who  had  previously  studied  it,  to  begin  de  novo.  This  is  espe- 
cially the  case  in  regard  to  the  actions  dependent  on  the  Spinal  Cord ;  which 
it  seems  desirable  to  consider  in  the  first  instance,  in  order  that  it  may  be 


286  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

clearly  defined  what  the  Brain  does  not  do.  By  many,  even  in  recent  times, 
the  Spinal  Cord  has  been  considered  as  a  mere  appendage  to  the  Brain ;  but 
the  phenomena  of  its  independent  action  render  such  an  idea  quite  inadmis- 
sible. These  phenomena  have  been  especially  pointed  out  by  Dr.  M.  Hall ; 
and  it  is  mainly  owing  to  his  arguments,  that  Physiologists  are  now  for  the 
most  part  agreed  in  the  general  fact, — that  the  Spinal  Cord  constitutes  a  dis- 
tinct centre,  or  rather  a  collection  of  centres,  of  nervous  influence,  and  that 
its  operations  are  carried  on  through  the  nervous  trunks  with  which  it  is  con- 
nected. It  is  further  generally  admitted  that  its  functions  are  independent  of 
the  will;  and  that  they  are  in  effect  frequently  opposed  to  those  of  the  Brain, 
which  operates  on  the  muscles,  either  by  a  volitional,  or  by  an  emotional 
impulse.  And  lastly,  its  actions  are  always  (except  when  excited  by  a  physi- 
cal irritation  directly  applied  to  itself)  entirely  of  a  reflex  character;  that  is 
to  say,  the  motor  impulses  which  originate  in  it  are  not  spontaneous,  but  re- 
sult from  the  stimulus  of  impressions,  conveyed  to  it  by  the  afferent  trunks,  and 
operating  upon  it,  to  use  the  expression  of  Prochaska,  according  to  certain 
"peculiar  laws  written,  as  it  were,  by  nature  on  its  medullary  pulp."  It  is 
not,  however,  universally  admitted  that  these  actions  are  independent  of  sen- 
sation; and  some  eminent  physiologists,  among  whom  may  be  named  Dr. 
Alison,  still  hold  that  the  intervention  of  sensation  is  necessary — in  the  case 
at  least,  of  the  ordinary  associated  movements,  which  "have  definite  ends  in 
view,  and  follow  one  another  in  regular  succession,  as  those  of  Respiration, — 
for  an  impression  to  give  rise  to  that  organic  change  in  the  Spinal  Cord,  which 
shall  terminate  in  a  muscular  motion.*  It  will  be  desirable,  therefore,  to  con- 
sider the  evidence  upon  which  the  statement  rests,  that  reflex  actions  are  in- 
dependent of  sensation,  though  ordinarily  accompanied  by  it. 

364.  In  the  first  place,  then,  it  has  long  been  well  known  that,  in  the 
Human  being,  the  Spinal  Cord  does  not  by  itself  possess,  in  the  remotest 
degree,  the  power  of  communicating  sensory  impressions  to  the  mind;  since, 
when  its  lower  portion  has  been  severed  from  the  brain  by  injury  or  disease, 
there  is  complete  anaesthesia  of  all  the  parts  of  the  body,  which  derive  their 
nerves  exclusively  from  it.  Hence  it  might  be  inferred,  that  throughout  the 
Vertebrated  classes,  the  spinal  cord  is  equally  destitute  of  sensibility ;  and 
that  any  movements  produced  by  stimuli  acting  through  it,  are  the  results  of  a 
physical,  and  not  of  a  sensorial  change.  This  inference,  however,  has  been 
disputed  ;  and,  if  unsupported  by  other  evidence,  it  would  not,  perhaps,  be 
entitled  to  rank  as  an  ascertained  truth.  The  very  performance,  by  decapi- 
tated animals  of  inferior  tribes,  of  actions  which  had  not  been  witnessed  in 
Man  under  similar  circumstances,  has  been  held  to  indicate,  that  the  spinal 
cord  in  them  has  an  endowment  which  his  does  not  possess.  The  possibility 
of  such  an  explanation — however  unconformable  to  that  analogy  throughout 
organized  nature,  which  the  more  it  is  studied,  the  more  invariably  is  found 
to  guide  to  truth — could  not  be  disproved.  Whatever  experiments  on  decapi- 
tated animals  were  appealed  to,  in  support  of  the  doctrine  that  the  brain  is 
the  only  seat  of  sensibility,  could  be  met  by  a  simple  denial  that  the  spinal 
cord  is  everywhere  as  destitute  of  that  endowment,  as  it  appears  to  be  in  Man. 
The  cases  of  profound  sleep  and  apoplexy  might  be  cited,  as  examples  of 
reflex  action  without  consciousness  ;  and  these  might  be  met  by  the  assertion, 
that  in  such  conditions  sensations  are  felt,  though  they  are  not  remembered. 
It  is  difficult,  however,  to  apply  such  an  explanation  to  the  case  of  anence- 

*  See  Outlines  of  Physiology,  3d  edit,  211.  By  many  of  the  German  Physiologists,  also, 
it  is  maintained  that  Sensation  is  a  necessary  link  in  the  chain  of  reflex  actions  ;  but  as  they 
employ  the  term  sensation  in  a  sense  which  does  not  involve  consciousness,  it  is  obvious  that 
their  dissent  from  Dr.  Hall's  views  is  chiefly  verbal. 


FUNCTIONS  OF  THE  SPINAL  CORD. REFLEX  ACTION.  287 

phalous  human  infants  (in  which  all  the  ordinary  reflex  actions  have  been  ex- 
hibited, with  an  entire  absence  of  brain),  without  supposing  that  the  Medulla 
Oblongata  is  the  seat  of  a  sensibility  which  we  know  that  the  lower  part  of 
the  Spinal  Cord  does  not  possess ;  and  of  this  there  is  no  evidence  whatever. 

365.  Experiments  on  the  lower  animals,  then,  and  observation  of  the  phe- 
nomena manifested  by  apoplectic  patients   and  anencephalous  infants,  might 
lead  to  the  conclusion,  that  the   Spinal  Cord   does  not  possess  a  sensibility, 
and  that  its  reflex  actions  are  independent  of  sensation.     At  this  conclusion, 
Prochaska,  Sir  G.  Blane,  Flourens,  and  other  physiologists,  had  arrive*  ;  but 
it  was  not  until  special  attention  was  directed  to  the  subject  by  Dr.  M.  Hall, 
that  facts  were  obtained  by  which  a  positive  statement  of  it  could  be  supported. 
For  the  question  might  have  been  continually  asked, — If  the  spinal  cord  in 
Man  is  precisely  analogous  in  function  to  that  of  the  lower  Vertebrata,  why 
are  not  its  reflex  phenomena  manifested,  when  a  portion  of  it  is  severed  from 
the  rest  by  disease  or  injury  ?     The  answer  to  this  question  is  twofold.     In 
the  first  place,  simple  division  of  the  cord  with  a  sharp  instrument  leaves  the 
separated  portion  in   a  state  of  much  more  complete  integrity,  and  therefore 
in  a  state  much  more  fit  for  the  performance  of  its  peculiar  functions,  than  it 
ordinarily  is  after  disease  or  violent  injury ;  and  as  the  former  method  of  di- 
vision is  one  with  which  the  Physiologist  is  not  likely  to  meet  in  Man  as  a 
result  of  accident,  and  which  he  cannot  experimentally  put  in  practice,  the 
cases  in  which  reflex  actions  are  manifested,  are  likely  to  be  comparatively  few. 
But,  secondly,  a  number  of  such  instances  have  now  been  accumulated,  sufficient 
to  prove  that  the  occurrence  is  by  no  means  so  rare  as  might  have  been  sup- 
posed; and  that  nothing  is   required   but  patient  observation,  to  throw  great 
light  on  this  interesting  question,  from  the  phenomena  of  disease.     A  most 
valuable  collection  of  such  cases,  occurring  within  his  own  experience,  has 
been  published  by  Dr.  W.  Budd  ;*  and  the  leading  facts  observed  by  him  will 
be  now  enumerated. 

366.  In  the  first  case,  paraplegia  was  the  result  of  angular  distortion  of  the 
spine  in  the  dorsal  region.     The  sensibility  of  the  lower  extremities  was  ex- 
tremely feeble,  and  the  power  of  voluntary  motion  was  almost  entirely  lost. 
"  When,  however,  any  part  of  skin  is   pinched  or  pricked,  the  limb  that  is 
thus   acted  on  jumps  with   great  vivacity;  the  toes  are  retracted  towards  the 
instep,  the  foot  is  raised  on  the  heel,  and  the  knee  so  flexed  as  to  raise  it  off 
the  bed ;  the  limb  is  maintained  in  this  state  of  tension  for  several  seconds 
after  the  withdrawal  of  the  stimulus,  and  then  becomes  suddenly  relaxed." 
"  In  general,  while  one  leg  was  convulsed,  its  fellow  remained  quiet,  unless 
stimulus  was  applied  to  both  at  once."    "  In  these  instances,  the  pricking  and 
pinching  were  perceived  by  the  patient ;  but  much  more  violent  contractions 
are  excited  by  a  stimulus,  of  whose  presence  he  is  unconscious.     "When  a 
feather  is  passed  lightly  over  the  skin,  in  the  hollow  of  the  instep,  as  if  to 
tickle,  convulsions  occur  in  the  corresponding  limb,  much  more  vigorous  than 
those  induced  by  pinching  or  pricking;  they  succeed  one  another  in  a  rapid 
series   of  jerks,  which  are  repeated  as  long  as  the  stimulus  is  maintained." 
"When  any  part  of  the  limb  is  irritated  in  the  same  way,  the  convulsions 
which  ensue  are  very  feeble,  and  much  less  powerful  than  those  induced  by 
pricking  or  pinching."     "  Convulsions,  identical  with  those  already  described, 
are  at  all  times  excited  by  the  acts  of  defecation  and  micturition.     At  these 
times,  the  convulsions  are  much  more  vigorous  than  under  any  other  circum- 
stances, insomuch  that  the  patient  has  been  obliged  to  resort  to  mechanical 
means  to  secure  his  person  while  engaged  in  these  acts.     During  the  act  of 
expulsion,  the  convulsions  succeed  one  another  rapidly,  the  urine  is  discharged 

*  Medico-Chirurgical  Transactions,  vol.  xxii. 


288  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

in  interrupted  jets,  and  the  passage  of  the  faeces  suffers  a  like  interruption." 
The  convulsions  are  more  vigorous,  the  greater  the  accumulation  of  urine ; 
and  involuntary  contractions  occur  whenever  the  bladder  is  distended,  and 
also  when  the  desire  to  relieve  the  rectum  is  manifested.  "In  all  these  cir- 
cumstances, the  convulsions  are  perfectly  involuntary ;  and  he  is  unable,  by 
any  effort  of  the  will,  to  control  or  moderate  them."  The  patient  subse- 
quently regained,  in  a  gradual  manner,  both  the  sensibility  of  the  lower  ex- 
tremiges,  and  voluntary  power  over  them  ;  and  as  voluntary  power  increased, 
the  susceptibility  to  involuntary  movements,  and  the  extent  and  power  of  these, 
diminished. 

367.  This  case,  then,  exhibits  an  increased  tendency  to  perform  reflex  actions, 
when  the  control  of  the  brain  was  removed ;  and  it  also  shows  that  a  slight 
impression  upon  the  surface,  of  which  the  patient  was  not  conscious,  was 
more  efficacious  in  exciting  reflex  movements,  than  were  others  that  more 
powerfully  affected  the  sensory  organs.  This  is  constantly  observed  in  ex- 
periments upon  the  lower  animals  ;  and  it  harmonizes,  also,  with  the  important 
fact,  that,  when  the  trunk  of  an  afferent  nerve  is  pinched,  pricked,  or  other- 
wise irritated,  the  reflex  function  will  not  be  nearly  so  strongly  excited,  as 
when  a  gentler  impression  is  made  on  a  surface  supplied  by  the  branches  of 
this  nerve.  The  former  produces  pain,  whilst  the  latter  does  not;  the  amount 
of  sensation,  therefore,  does  not  at  all  correspond  with  the  intensity  of  reflex 
action,  but  rather  bears  a  converse  relation  to  it.  Mr.  Grainger  found,  that 
he  could  remove  the  entire  hind  leg  of  a  Salamander  with  the  scissors,  with- 
out the  creature  moving,  or  giving  any  expression  of  suffering,  if  the  spinal 
cord  had  been  divided :  yet  that,  by  irritation  of  the  foot,  especially  by  heat, 
in  an  animal  similarly  circumstanced,  violent  convulsive  actions  in  the  leg  and 
tail  were  excited. — It  should  be  added  that,  in  the  foregoing  case,  the  nutrition 
of  the  lower  extremities  was  not  impaired,  as  in  most  cases  of  paraplegia. 
The  rationale  of  this  phenomenon,  which  is  to  be  constantly  observed  when 
the  reflex  actions  of  the  part  remain  entire,  will  be  hereafter  noticed  (Chap. 
VIL). 

368.  In  another  case,  the  paralysis  was  more  extensive,  having  been  pro- 
duced by  an  injury  (resulting  from  a  fall  into  the  hold  of  a  vessel)  at  the  lower 
part  of  the  neck.  There  was  at  first  total  loss  of  voluntary  power  over  the 
lower  extremities,  trunk,  and  hands ;  slight  remaining  voluntary  power  in  the 
wrists,  rather  more  in  the  elbows,  and  still  more  in  the  shoulders.  The 
intercostal  muscles  did  not  participate  in  the  movements  of  respiration.  The 
sensibility  of  the  hands  and  feet  was  greatly  impaired.  There  were  retention 
of  urine,  and  involuntary  evacuation  of  the  faeces.  Recovery  took  place  very 
gradually ;  and  during  its  progress,  several  remarkable  phenomena  of  reflex 
action  were  observed.  At  first,  tickling  one  sole  excited  to  movement  that 
limb  only  which  was  acted  upon  ;  afterwards,  tickling  either  sole  excited  both 
legs,  and,  on  the  26th  day,  not  only  the  lower  extremities,  but  the  trunk  and 
other  extremities  also.  Irritating  the  soles,  by  tickling  or  otherwise,  was  at 
first  the  only  method,  and  always  the  most  efficient  one,  by  which  convulsions 
could  be  excited.  From  the  26th  to  the  69th  day,  involuntary  movements  in 
all  the  palsied  parts  continued  powerful  and  extensive,  and  were  excited  by 
the  following  causes: — In  the  lower  extremities  only,  by  the  passage  of  flatus 
from  the  bowels,  or  by  the  contact  of  a  cold  urinal  with  the  penis ;  convulsions 
in  the  upper  extremities  and  trunk,  attended  with  sighing,  by  plucking  the 
hair  of  the  pubes.  On  the  41st  day,  a  hot  plate  of  metal  was  applied  to  the 
soles,  and  found  a  more  powerful  excitor  of  movement  than  any  before  tried. 
The  movements  continued  as  long  as  the  hot  plate  was  kept  applied ;  but  the 
same  plate,  at  the  common  temperature,  excited  no  movements  after  the  first 
contact.  The  contact  was  distinctly  felt  by  the  patient ;  but  no  sensation  of 


FUNCTIONS  OF  THE  SPINAL  CORD. REFLEX  ACTION.  289 

heat  was  perceived  by  him,  although  the  plate  was  applied  hot  enough  to 
cause  vesication.  At  three  different  intervals,  the  patient  took  one-eighth  of 
a  grain  of  strychnia  three  times  a  day.  Great  increase  of  susceptibility  to 
involuntary  movements  immediately  followed,  and  they  were  excited  by  the 
slightest  causes.  No  convulsions  of  the  upper  extremities  could  ever  be  pro- 
duced, however,  by  irritating  their  integument;  though,  under  the  influence  of 
strychnia,  pulling  the  hair  of  the  head,  or  tickling  the  chin,  would  occasion 
violent  spasmodic  actions  in  them.  Spontaneous  convulsions  of  the  palsied 
parts,  which  occurred  at  other  times,  were  more  frequent  and  more  powerful 
after  the  use  of  strychnia.  On  the  first  return  of  voluntary  power,  the 
patient  was  enabled  to  restrain  in  some  measure  the  excited  movements  ;  but 
this  required  a  distinct  effort  of  the  will ;  and  the  first  attempts  to  walk  were 
curiously  affected,  by  the  persistence  of  the  susceptibility  to  excited  involun- 
tary movements.  When  he  first  attempted  to  stand,  the  knees  immediately 
became  forcibly  bent  under  him ;  this  action  of  the  legs  being  excited  by 
contact  of  the  soles  with  the  ground.  On  the  95th  day  this  effect  did  not 
take  place,  until  the  patient  had  fciade  a  few  steps ;  the  legs  then  had  a 
tendency  to  bend  up,  a  movement  which  he  counteracted  by  rubbing  the 
surface  of  the  belly :  this  rubbing  excited  the  extensors  to  action,  and  the  legs 
became  extended  with  a  jerk.  A  few  more  steps  were  then  made ;  the 
manoeuvre  repeated,  and  so  on.  This  susceptibility  to  involuntary  movements 
from  impressions  on  the  soles,  gradually  diminished ;  and  on  the  141st  day, 
the  patient  was  able  to  walk  about,  supporting  himself  on  the  back  of  a  chair 
which  he  pushed  before  him ;  but  his  gait  was  unsteady,  and  much  resembled 
that  of  chorea.  Sensation  improved  very  slowly :  it  was  on  the  53d  day 
that  he  first  slightly  perceived  the  heat  of  the  metal  plate. 

369.  This  important  case  suggests  many  interesting  reflections.     Common 
sensation  was  not  so  completely  abolished  as  in  the  former  instance;  but  of 
the  peculiar  kind  of  impression,  which  was  found  most  efficacious  in  exciting 
reflex   movements,  no  consciousness  whatever  was  experienced.     Not  less 
interesting  was  the  circumstance,  that  convulsions  could  be  readily  excited  by 
impressions  on  surfaces  above  the  seat  of  injury;  as,  by  pulling  the  hair  of 
the  scalp,  a  sudden  noise,  and  so  on.     This  proves  two  important  points : 
first,  that  a  lesion  of  the  cord  may  be  such,  as  to  intercept  the  transmission  of 
voluntary  influence,  and  yet  may  allow  the  transmission  of  that  reflected  from 
incident  nerves.     Secondly,  that  all  influences  from  impressions  on  incident 
nerves  are  diffused  through  the  cord;  for,  in  the  instance  adduced,  the  reflected 
influence  was  undoubtedly  not  made  to  deviate  into  the  cord  by  the  morbid 
condition  of  that  organ,  but  followed   its   natural  course  of  diffusion,  being 
rendered  manifest  in  this  case  by  the  convulsions  which  were  excited,  in  con- 
sequence of  increased  activity  of  the  motor  function  of  the  cord.    It  is  further 
interesting  to  remark,  that,  in  the  foregoing  case,  the  reflex  actions  were  very 
feeble  during  the  first  seven  days, in  comparison  with  their  subsequent  energy; 
being  limited  to  slight  movements  of  the  feet,  which  could  not  always  be 
excited  by  tickling  the  soles.     In  another  case  of  very  similar  character,  it  was 
three  days  after  the  accident,  before  any  reflex  actions  could  be  produced.    It 
is  evident,  then,  that  the  spinal  cord  must  have  been  in  a  state  of  concussion, 
which  prevented  the  manifestation  of  its  peculiar  functions,  so  long  as  this 
effect  lasted;  and  it  is  easy,  therefore,  to  perceive,  that  a  still  more  severe 
shock  might  permanently  destroy  its  power,  so  as  to  prevent  the  exhibition  of 
any  of  the  phenomena  of  reflex  action. 

370.  It  seems  well  established,  then,  by  such  cases,  that  the  Spinal  Cord, 
or  small  segments  of  it,  may  serve  in   Man  as   the  centre  of  very  energetic 
reflex  actions ;  when  the  voluntary  power  exercised  through  the  Brain,  over 
the  muscular  system,  is  suspended  or  destroyed.     And  it  is  further  evident, 

25 


290  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

that  these  movements  are  produced  by  a  mere  physical  change  in  the  nervous 
centres ;  the  consciousness  of  the  individual  not  being  affected  in  their  per- 
formance, and  sensation  having  therefore  no  necessary  participation  in  them. 
As  the  movements  witnessed  in  the  lower  animals,  under  the  same  circum- 
stances, are  altogether  of  a  similar  character,  there  seems  no  good  reason  to 
attribute  to  their  Spinal  Cord  an  attribute,  of  which  it  is  certainly  destitute  in 
Man.  There  is  no  essential  difference,  either  in  structure,  or  in  the  nature  of 
the  actions  performed  by  them,  between  the  Spinal  Cord  and  the  Medulla 
Oblongata,  which  can  warrant  us  in  assigning  to  the  latter  a  function  that  the 
former  does  not  possess:  and  if  the  reflexions  of  the  Spinal  Cord  do  not 
involve  sensation,  there  is  good  reason  for  concluding,  that  this  change  is  not 
a  necessary  element  in  those  of  the  Medulla  Oblongata.  It  is  perfectly  true, 
that  it  usually  accompanies  in  us  the  greater  number  of  actions,  to  which  that 
division  of  the  centre  is  subservient;  for  example,  those  of  respiration  and 
deglutition :  and  it  is  scarcely  possible  for  such  an  accident  to  occur  in  the 
Human  being,  as  the  separation  of  the  Medulla  Oblongata  from  the  brain, 
without  the  destruction  of  the  independent  functions  of  both.  It  is  not  likely 
that  we  can  ever  have  the  power  of  ascertaining,  by  the  testimony  of  a  patient 
so  affected,  that  the  Respiratory  movements  are  performed  without  the  neces- 
sary intervention  of  sensation ;  as  we  have  been  able  to  do  in  regard  to  other 
reflex  movements.  But  as  the  general  fact  is,  that  there  is  no  positive  ground 
whatever  for  regarding  any  part  of  the  Spinal  Cord  as  a  sensorium  independent 
of  the  brain,  and  that  the  Respiratory  movements  certainly  correspond  in  all 
their  conditions  with  the  actions  denominated  reflex,— there  would  seem  no 
good  reason  for  maintaining  that  sensation  is  an  element  in  their  production, 
whilst  it  is  admitted  to  be  not  essential  in  the  case  of  the  less  regular  con- 
vulsive actions  already  described.  The  character  of  adaptiveness  to  a  designed 
end,  in  regard  to  their  combination  and  succession,  which  the  movements  of 
respiration  and  deglutition  exhibit,  has  been  shown  to  be  no  proof  of  their 
dependence  on  sensation. 

-  371.  The  question  has  been  often  put  to  those  who  advocate  this  view, — 
wrfy  the  sensation  should  be  so  constantly  associated  with  these  changes,  if 
not  essential  to  produce  the  motion?  An  objection  might  fairly  be  made  to 
any  reasoning  from  final  causes,  in  a  question  of  facts ;  but  the  inquiry  may 
be  easily  answered.  In  many  instances  the  production  of  sensations  is  the 
stimulus  necessary  for  the  excitement  of  other  actions,  which  are  required 
for  the  continued  maintenance  of  those  in  question.  This  may  be  rendered 
more  comprehensible  by  a  simple  illustration. — A  cistern  filled  with  water 
may  be  speedily  emptied  by  a  cock  occasionally  opened  at  the  bottom ;  but, 
if  it  communicate  with  a  reservoir,  by  means  of  a  valve  opened  by  a  ball 
floating  on  the  surface  of  the  water  it  contains,  it  may  be  kept  constantly  full. 
The  lower  cock  is  opened,  and  the  water  flows  out ;  and,  in  consequence  of 
the  lowering  of  the  surface  thus  produced,  the  floating  valve  above  is  opened, 
and  the  cistern  is  refilled  from  the  reservoir.  Now  here  the  action  of  the  ball- 
cock  at  the  top  is  not  essential  to  the  flow  of  water  at  the  bottom,  but  is 
rather  consecutive  upon  it. — Just  so  is  it  with  regard  to  those  movements  of 
Animals,  which  are  concerned  in  the  ingestion  of  their  food.  The  muscular 
contractions  required  to  propel  it  along  the  alimentary  canal,  from  the  stomach 
downwards,  are  provided  for,  without  even  the  intervention  of  the  nervous 
system.  To  bring  it  within  reach  of  these,  a  muscular  apparatus  is  provided, 
by  which  anything  that  comes  within  its  grasp  is  conveyed  downwards, 
through  a  reflex  operation,  originating  in  the  impression  made  upon  the  sur- 
face of  the  pharynx.  Now  this  action,  in  the  ordinary  condition,  may  be 
considered  as  attended  with  sensation,  in  order  that  the  Animal  may  be  called 
upon  to  execute  those  other  movements,  which  will  bring  food  within  the 


FUNCTIONS  OF  THE  SPINAL  CORD. — REFLEX  ACTION.  291 

reach  of  the  apparatus  of  deglutition.  The  Polype  is  dependent  for  its  sup- 
plies of  aliment,  upon  what  the  currents  in  the  surrounding  fluid,  or  other 
chances,  bring  into  its  neighbourhood ;  but  anything  which  touches  its  ten- 
tacula,  is  entrapped  and  conveyed  into  its  stomach.  The  anencephalous 
Infant,  again,  can  swallow,  and  even  suck;  but  it  can  execute  no  other  move- 
ments adapted  to  obtain  the  supply  of  food  continually  necessary  for  mainte- 
nance, because  it  has  not  a  mind  which  sensations  could  awake  into  activity. 

372.  The  sensation  connected  with  reflex  actions  has  not  only  this  import- 
ant end,  but  it  frequently  contributes  to  enjoyment,  as  in  suction  and  ejaculatio 
seminis.     Now  there  is  evidence  that  the  latter  of  these  processes,  involving 
though  it  does  the  combined  action  of  a  number  of  muscles,  and  dependent 
as  it  seems  upon  sensation  of  a  very  peculiar  kind,  may  take  place  without 
consciousness  on  the  part  of  the  individual.     Brachet  mentions  a  case  of  this 
kind  in  the  Human  subject,  in  which  the  patient's  own  testimony  could  be 
adduced;  and  he  ascertained  that  emission  could  be  produced  in  dogs,  in 
which  the  spinal  cord  had  been  divided  in  the  back,  and  in  which,  therefore, 
it  can  scarcely  be  doubted  that  the  sensibility  of  the  genital  organs  was  de- 
stroyed.    Such  cases,  it  might  be  thought,  are  sufficient  to  prove,  that  the 
Reflex  power,  operating  independently  of  sensation,  is  not  confined  to  such 
irregular  convulsive  movements  as  are  seen  in  Man  after  disease  or  injury; 
but  is  exercised  in  producing  the  regular  combined  actions  which  are  neces- 
sary for  the  maintenance  of  the  organic  functions.     The  sensation  accompa- 
nying these  actions,  moreover,  frequently  affords  premonition  of  danger,  or 
gives  excitement  to  supplementary  actions  destined  to  remove  it,  as  in  the 
case  of  respiration ;  for  where  anything  interferes  with  the  due  discharge  of 
the  function,  the  uneasy  sensation  that  ensues   occasions  unwonted  move- 
ments, which  are  more  or  less  adapted  to  remove  the  impediment,  in  propor- 
tion as  they  are  guided  by  judgment  as  well  as  by  consciousness.     Again, 
sensation  often  gives  warning  against  inconvenience,  as  in  the  excretory  func- 
tions; and  here  it  is  very  evident,  that  its  object  is  not  only  (if  it  be  at  all)  to 
excite  the  associated  muscles  necessary  for  the  excretion,  but  actually  to  make 
the  Will  set  up  the  antagonizing  action  of  the  sphincters,  as  will  be  hereWter 
explained  (§  391).     There  is  one  unequivocal  case,  in  the  ordinary  condition 
of  the  human  body,  of  reflex  action  without  sensation ;  this  is  the  muscular 
contraction,  by  which  the  food  is  propelled  from  the  bottom  of  the  pharynx 
to  the  stomach.     Unless  the  morsel  be  very  bulky,  so  as  to  press  on  the  sur- 
rounding parts,  or  be  very  different  in  temperature  from  the  surface  it  touches, 
or  have  any  peculiar  irritating  quality,  we  are  not  more  conscious  of  its  pre- 
sence, whilst  it  is  passing  down  the  lower  part  of  the  resophagus,  than  when 
it  is  being  propelled  along  the  intestinal  tube;  and  yet,  as  Dr.  J.  Reid's  ex- 
periments* have  shown,  this  contraction  is  of  a  reflex  character,  not  being 
stimulated  by  direct  contact,  but  requiring  the  completeness  of  the  nervous 
circle  for  its  performance. 

373.  We  shall  now  separately  consider  the  chief  operations,  in  which  the 
Spinal  Cord  and  its  system  of  nerves  are  usually  concerned,  in  the  ^ordinary 
course  of  the  vital  actions  of  the  Human  body.     Upon  taking  a  general  sur- 
vey of  these,  it  will  be  found  that  their  principal  function  is,  to  supply  the 
conditions  requisite  for  the  maintenance  of  the  various   Organic  processes. 
Thus,  the  aeration  of  the  blood,  which  takes   place  whenever  that  fluid  is 
placed  in  relation  with  the  atmosphere,  can  only  be  carried  on,  by  the  regular 
exchange  of  the  small  quantity  of  the  gas  contained  in  the  lungs;  if  this 
cease,  the  circulation  is  soon  brought  to  a  stand,  and  loss  of  vitality  of  the 
whole  system  speedily  results.     Hence  this  is  the  most  constantly  necessary 

*  Edinb.  Med.  and  Surg.  Journ.,  vol.  xlix. 


292  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

of  all  the  actions  of  the  Spinal  Cord ;  and  we  find  its  maintenance,  in  spite 
of  accident  or  disease  of  the  spine,  remarkably  provided  for,  in  the  location  of 
the  centre  of  the  respiratory  movements,  which  occupies  a  position  where  it 
receives  the  greatest  possible  amount  of  protection.  The  supply  of  the  di- 
gestive apparatus,  again,  is  immediately  dependent  upon  the  Spinal  system  ; 
and  this,  being  another  essential  function,  has  its  centre  equally  protected. 
The  outlets  of  the  cavities  are  also  controlled  by  the  Spinal  system ;  but  this 
control,  although  essential  to  the  comfort  of  life,  is  less  necessary  to  its  main- 
tenance ;  and  we  find  it  dependent  upon  a  portion  of  the  Cord,  which  is 
more  liable  to  lose  its  powers  by  disease  or  injury.  It  is  possible,  as  will 
hereafter  be  shown,  that  several  actions,  which  are  at  first  voluntary,  may  be 
effected,  when  so  frequently  performed  as  to  become  habitual,  through  the 
medium  of  the  Spinal  system  ;  of  this  kind  seem  to  be  the  movements  of 
locomotion,  which  are  continued  involuntarily,  when  the  whole  attention  of 
the  mind  is  given  to  other  objects,  but  which  the  Will  can  check  at  any  time. 
We  shall  commence  our  particular  survey  of  the  Reflex  movements  in  Man, 
with  the  consideration  of  those  of  Respiration,  which  are  well  adapted  for 
illustrating  their  general  character. 

374.  Respiratory  Movements. — The  centre  of  these  is  the  upper  part  of 
the  Medulla  Oblongata;  into  this  may  be  traced  the  excitor  nerves,  that  con- 
vey the  stimulus  on  which  the  movements  are  dependent;  and  from  it  pro- 
ceed, either  directly  or  indirectly,  the  motor  nerves  by  which  they  are  carried 
into  effect.  The  chief  Excitor  of  the  respiratory  movements  is  unquestion- 
ably the  Par  Vagum.  When  this  is  divided  on  both  sides,  according  to  the 
experiments  of  Dr.  Reid,*  the  number  of  respiratory  movements  is  considera- 
bly diminished,  usually  about  one-half.  Now  if  this  nerve  excites  the  motions 
of  respiration  by  its  powerful  action  in  producing  sensation,  we  should  ex- 
pect to  find  its  trunk  endowed  with  considerable  sensibility,  which  is  not  the 
case ;  for  all  experimenters  agree  in  stating  that,  when  its  trunk  is  pinched  or 
pricked,  the  animal  does  not  exhibit  signs  of  pain  nearly  so  acute,  as  when 
the  trunks  of  the  ordinary  spinal  nerves,  or  of  the  fifth  pair,  are  subjected  to 
sircar  treatment.  It  cannot  be  questioned,  however,  that  its  power  as  an 
excitor  of  respiration  is  very  great ;  since,  besides  the  fact  of  the  diminution 
in  the  number  of  inspirations  which  occurs  immediately  on  section  of  it, 
irritation  of  its  trunk  in  the  neck  is  instantly  followed  by  an  act  of  inspira- 
tion. It  is  evident  that  this  power  must  arise  from  impressions  made  upon 
its  peripheral  extremities.  The  impression  is  probably  due  to  the  presence 
of  venous  blood  in  the  capillaries  of  the  lungs ;  or,  as  Dr.  M.  Hall  thinks,  to 
the  presence  of  carbonic  acid  in  the  air-cells.  Either  or  both  may  be  true. — 
The  Pneumogastric  nerve,  however,  is  not  the  only  excitor  of  the  respiratory 
movements ;  since,  when  the  nerve  is  cut  on  each  side,  they  still  continue. 
Dr.  Reid  has  satisfactorily  shown  the  statement  of  many  experimenters,  that 
the  inspirations  are  increased  in  frequency  after  this  operation,  to  be  erroneous ; 
this  idea  having  originated  in  their  very  prolonged  and  laborious  character. 
The  removal  of  the  Encephalon,  also,  diminishes  the  frequency  of  the  respi- 
ratory movements,  whether  it  be  performed  before  or  after  the  section  of  the 
Vagi.  Dr.  Reid  found  that,  in  a  kitten  of  a  day  old,  in  which  the  inspira- 
tions were  100  per  minute,  they  fell  to  40  when  the  Encephalon  was  re- 
moved ;  and  on  subsequently  cutting  the  Pneumogastrics,  the  number  of 
inspirations  instantly  fell  to  between  3  and  4  in  the  minute,  and  continued  so 
-for  some  time.  Hence  it  appears  that  the  respiratory  movements  are  partly 
dependent  upon  sensation,  and  a  motor  influence  excited  by  it;  and  this  may 
also  be  learned  from  the  prolonged  and  laborious  character  of  the  inspirations 

*  Edinb.  Med.  and  Surg.  Journ.,  vol.  li. 


REFLEX  ACTIONS. RESPIRATORY  MOVEMENTS.  293 

during  sleep  or  profound  attention,  when  the  influence  of  the  Encephalon  is 
more  or  less  suspended. 

375.  But  why  (it  may  be  asked)  do  the  movements  continue,  when  the 
Pneumogastrics  have  been  divided,  and  the  Encephalon  has  been  removed  ? 
It  is  evident  that  there  must  be  other  excitors  to  the  action  of  the  respiratory 
muscles.     Amongst  these,  the  nerves  distributed  to  the  general  surface,  and 
particularly  to  the  face,  probably  perform  an  important  part;  and  in  exciting 
the  first  inspiration,  the  Fifth  pair  seems  the  principal  agent.     It  has  long 
been  a  well-known  fact,  that  the  first  inspiratory  effort  of  the  new-born  infant 
is  most  vigorously  performed,  when  the  cool  external  air  comes  into  contact 
with  the  face ;  and  that  impressions  on  the  general  surface,  such  as  a  slap  of 
the  hand  on  the  nates,  are  often  effectual  in  exciting  the  first  inspiratory 
movements,  when  they  would  not  otherwise  commence.     Dr.  M.  Hall  relates 
an  interesting  case,  in  which  the  first  inspiration  was  delayed,  simply  because 
the  face  was  protected  by  the  bed-clothes  from  the  atmosphere ;  and,  on  lift- 
ingtup  these,  the  infant  immediately  breathed.     Dr.  M.  Hall  has  recently 
mentioned  the  important  fact,  that  if  the  cerebrum  be  removed,  and  the  pneu- 
mogastrics  be  divided,  in  a  young  kitten,  the  number  of  acts  of  respiration 
will  be  reduced  to  four  in  a  minute;  but  by  directing  a  stream  of  air  on  the 
animal,  or  by  irritating  various  parts  of  the  general  surface,  we  may  excite 
twenty  or  thirty  acts  of  respiration  within  the  same  space  of  time.     He 
further  remarks,  that  in  the  very  young  warm-blooded  animal,  as  in  the  cold- 
blooded animal,  the  phenomena  of  the  excito-motor  power  are  far  more  vividly 
manifested,  than  in  the  older  and  the  warm-blooded.     In  the  very  young 
.kitten,  even  when  asphyxiated  to  insensibility,  every  touch,  contact,  or  slight 
blow,— every  jar  of  the  table,  any  sudden  impression  of  the   external  air,  or 
that  of  a  few  drops  of  cold  water,  induces  at  once  energetic  reflex  movements, 
and  acts  of  inspiration.     This  may  be  looked  upon  as  Nature's  provision  for 
the  first  establishment  of  the  acts  of  inspiration  in  the  new-born  animal. — 
But  the  influence  of  the  nerves  of  the  general  system  is  by  no  means  want- 
ing in  the  adult;  as  the  following  experiment  of  Dr.  J.  Reid's  demonstrates. 
After  dividing  the  pneumogastrics,  and  removing  the  cerebrum  and  ceflUbel- 
lum,  he  divided  the  spinal  cord  high  up  in  the  neck,  so  as  to  cut  off  the  com- 
munication between  the  spinal  nerves   and  the  Medulla  Oblongata;  and  he 
found  that  the  frequency  of  the  respiratory  movements   was   still  further 
diminished,  although  they  were  not  even  then   entirely  suspended. — Every 
one  knows  the  fact,  that  the  first  plunge  into  cold  water,  the  first  descent  of 
the  streams  of  the  shower-bath,  or  even  the  dashing  of  a  glass  of  cold  water 
in  the  face,  will  produce  inspiratory  efforts ;  and  this  fact  has  many  important 
practical  applications.     Thus  in  the  treatment  of  Asphyxia,  whether  congeni- 
tal, or  the  result  of  narcotic  poisoning,  drowning,  &c.,  the  alternate  applica- 
tion of  cold  and  heat  is  found  to  be  one  of  the  most  efficacious  means   of 
restoring  the  respiratory  movements;  and  a  paroxysm  of  hysteric  laughter 
may  be  cut  short,  by  dashing  a  glass  of  cold  water  in  the   face. — It  may  be 
surmised  that  the  Sympathetic  nerve,  which  derives  many  filaments  from  the 
Cerebro-Spinal  system,  and  which  especially  communicates  with  the  Pneu- 
mogastric  nerves,  is  one  of  the  excitors  to  this  function;  and  this,  perhaps, 
not  only  through  its  ramifications  in  the  lungs,  which  are  considerable,  but 
also  by  its  distribution  on  the  systemic  vessels ;  so  that  it  may  convey  to  the 
Spinal  Cord  the  impression  of  imperfectly-arterialized  blood,  circulating  in 
these,  such  as  the  Pneumogastric  is  believed  to  transmit  from  the  lungs.     It 
will  hereafter  be  shown,  that  an  impression  of  a  corresponding  kind  is  more 
probably  the  cause  of  the  sense  of  Hunger  and  Thirst,  than  any  which  origi- 
nates in  the  stomach  alone  (Chap.  X.,  Sect.  1). 

376.  The  Motor  or  Efferent  nerves  concerned  in  the  function  of  Respira- 

26* 


294  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

tion,  are  those  which  Sir  C.  Bell  has  grouped  together  in  his  respiratory 
system.  The  most  important  of  these,  the  Phrenic,  arises  from  the  upper 
part  of  the  Spinal  Cord;  the  Intercostals  much  lower  down;  whilst  the  Facial 
nerve  and  the  Spinal  Accessory,  to  the  latter  of  which,  as  will  hereafter  be 
stated  (§  408),  the  motor  powers  of  the  par  vagum  are  chiefly  due,  take  their 
origin  in  the  Medulla  Oblongata  itself.  But  we  must  not  decide  upon  the 
connection  of  a  particular  nerve  with  a  particular  segment  of  the  Spinal  Cord, 
simply  because  it  diverges  from  it  at  that  point.  It  has  been  shown  that,  in 
the  Mollusca,  a  nerve  passing  to,  or  proceeding  from,  one  ganglion,  frequently 
passes  through  or  over  another  which  lies  in  its  course  ;  and  in  the  Articulata, 
this  is  a  still  more  constant  occurrence.  It  is  by  no  means  improbable,  then, 
that  the  connection  of  the  intercostal  nerves  is  really  in  part  with  the  grey 
matter  of  the  Medulla  Oblongata;  at  any  rate,  such  a  connection  has  not  been 
disproved.  The  white  columns  of  the  Spinal  Cord  consist  of  fibres,  which 
bring  the  spinal  nerves  into  connection,  not  only  with  the  brain,  but  also  with 
other  segments  of  the  ganglionic  portion  of  the  cord;  being  analogous  in  junc- 
tion, not  merely  to  the  distinct  fibrous  tract  of  the  ventral  column  of  the  Arti- 
culata, but  also  to  the  fibrous  bands  that  connect  the  ganglia  themselves.  And 
as  the  Medulla  Oblongata,  in  Vertebrated  animals,  is  the  chief  centre  of  the 
actions  of  Respiration,  it  can  scarcely  be  doubted  that  all  the  nerves  concerned 
in  that  function  have  a  direct  structural  connection  with  it. 

377.  That  the  Respiratory  movements,  as  ordinarily  performed,  are  essen- 
tially independent  of  the  Will,  appears  not  only  from  our  own  consciousness, 
but  also  from  cases  of  paralysis;  in  some  of  which,  the  power  of  the  will  over 
the  muscles  has  been  lost,  whilst  the  movements  have  been  kept  up  by  the 
reflex  action  of  the  Medulla  Oblongata  or  respiratory  ganglion ;  whilst  in 
others,  some  of  the  respiratory  muscles  have  been  motionless  during  ordinary 
breathing,  and  yet  have  remained  under  the  power  of  the  will.  Such  cases 
are  mentioned  by  Sir  C.  Bell,  in  the  Appendix  to  his  work  on  the  Nervous 
System,  That  consciousness  is  not  a  necessary  link  in  the  chain  of  causes, 
which  produce  the  respiratory  movements,  we  are  enabled  to  judge  from  the 
phenomena  presented  by  the  human  being  in  sleep  and  coma,  by  anencephalous 
foetuses,  and  by  decapitated  animals.  Further,  Dr.  Ley*  has  put  on  record  a 
case,  which  confirms  this  particular  inference,  just  in  the  same  manner  as  the 
cases  already  related  confirm  the  general  doctrine  of  the  non-existence  of  sen- 
sibility in  the  Spinal  Cord.  He  had  under  his  care  a  patient,  in  whom  the 
par  vagum  appeared  to  be  diseased;  the  lungs  suffered  in  the  usual  way  in 
consequence,  and  the  patient  had  evidently  laborious  breathing;  but  he  dis- 
tinctly said  that  he  felt  no  uneasiness  in  his  chest. — The  experience  of  every 
one  informs  him,  that  Respiratory  movements  are  partly  under  the  control 
and  direction  of  the  will,  though  frequently  unrestrainable  by  it.  In  ordinary 
circumstances,  when  the  blood  is  being  perfectly  aerated,  and  there  is  a  suffi- 
cient amount  of  arterial  blood  in  the  system  to  carry  on  the  functions  of  life 
for  a  short  time,  we  can  suspend  the  respiratory  actions  during  a  few  seconds 
without  any  inconvenience.  If,  however,  we  endeavour  to  prolong  the  sus- 
pension, the  stimulus  conveyed  by  the  excitor  nerves  to  the  Medulla  Oblon- 
gata becomes  too  strong,  and  we  cannot  avoid  making  inspiratory  efforts  ;  and 
if  the  suspension  be  still  further  prolonged,  the  whole  body  becomes  agitated 
by  movements,  which  are  almost  of  a  convulsive  nature  ;  and  no  effort  of  the 
will  can  then  prevent  the  ingress  of  air.t  It  is  easy  to  understand  why,  in 

*  On  Laryngismus  Stridulus,  p.  417. 

t  It  is  asserted  by  M.  Bourdon  (Recherches  sur  le  Mecanisme  de  la  Respiration,  p.  81), 
that  no  person  ever  committed  suicide,  though  many  have  attempted  to  do  so,  by  simply 
holding  the  breath;  the  control  of  the  will  over  the  respiratory  muscles  not  being  sufficiently 
great,  to  antagonize  the  stimulus  of  the  "  besoin  de  respirer,"  when  this  has  become  aggra- 


REFLEX  ACTIONS. RESPIRATORY  MOVEMENTS.  295 

the  higher  animals  at  least,  and  more  especially  in  Man,  the  respiratory  actions 
should  be  thus  placed  under  the  control  of  the  will :  since  they  are  subser- 
vient to  the  production  of  those  sounds,  by  which  individuals  communicate 
their  feelings  and  desires  to  each  other ;  and  which,  when  articulate,  are  capa- 
ble of  so  completely  expressing  what  is  passing  in  the  mind  of  the  speaker. 
If  the  respiratory  mucles  of  Man  were  no  more  under  his  control,  than  they 
appear  to  be  in  the  Insect  or  Molluscous  animal,  he  might  be  provided  with 
the  most  perfect  apparatus  of  speech,  and  yet  he  would  not  be  able  to  employ 
it  to  any  advantage. 

378.  The  motor,  power  of  the  Respiratory  nerves  is  exercised,  however, 
not  only  on  the  muscles  which  perform  the  inspiratory  and  expiratory  move- 
ments, but  on  those  which  guard  the  entrance  to  the  windpipe,  and  also  on 
certain  other  parts.  The  movements  of  the  internal  respiratory  apparatus 
are  chiefly,  if  not  entirely,  effected  through  the  medium  of  the  motor  fibres, 
which  the  Par  Vagum  contains.  These  motor  fibres  exist  in  very  different 
amount  in  its  different  branches.  For  example,  the  pharyngeal  and  resopha- 
geal  branches,  by  which  (as  will  hereafter  appear)  the  muscles  of  deglutition 
are  excited  to  contraction,  possess  a  much  larger  proportion  of  them,  and 
exhibit  much  less  sensibility  when  irritated,  than  do  other  divisions  of  the 
trunk.  Between  the  superior  and  inferior  laryngeal  nerves,  again,  there  is  an 
important  difference,  which  anatomical  and  experimental  research  has  now 
very  clearly  demonstrated.  It  has  long  been  known,  that  section  of  the  Par 
Vagum  in  the  neck,  above  the  inferior  laryngeals,  is  frequently  followed  by 
suffocation,  resulting  from  closure  of  the  glottis ;  and  hence  it  has  been  in- 
ferred, that  the  office  of  the  inferior  laryngeals  was  to  call  into  action  the 
dilators  of  the  larynx,  whilst  the  superior  laryngeals  were  supposed  to  stimu- 
late the  constrictors.  This  view,  however,  is  incorrect.  It  is  inconsistent 
with  the  results,  just  stated,  of  anatomical  examination  into  the  respective 
distribution  of  these  two  trunks ;  and  it  has  been  completely  overthrown  by 
the  very  careful  and  satisfactory  observations  and  experiments  of  Dr.  J.  Reid, 
which  have  established  that,  whilst  the  inferior  laryngeal  is  the  motor  nerve 
of  nearly  all  the  laryngeal  muscles,  the  superior  laryngeal  is  the  excitolf  or 
afferent  nerve,  conveying  to  the  Medulla  Oblongata  the  impressions  by  which 
muscular  movements  are  excited.  Its  motor  endowments  are  limited  to  the 
crico-thyroid  muscle,  to  which  alone  of  all  the  muscles  its  filaments  can  be 
traced,  the  remainder  being  distributed  beneath  the  mucous  surface  of  the 
larynx ;  and  its  sensibility  is  very  evident,  when  it  is  pinched  or  irritated 
during  experiments  upon  it.  On  the  other  hand,  the  motor  character  of  the 
inferior  laryngeal  branch  is  shown  by  its  very  slight  sensibility  to  injury,  its 
nearly  exclusive  distribution  to  muscles,  and  its  influence  in  exciting  contrac- 
tion of  these  when  its  separated  trunk  is  stimulated. 

379.  It  has  been  ascertained  by  Dr.  Reid  that,  if  the  inferior  laryngeal 
branches  be  divided,  or  the  trunk  of  the  par  vagum  be  cut  above  their  origin 
from  it,  there  is  no  constriction  of  the  glottis,  but  a  paralyzed  state  of  its  mus- 
cles. After  the  first  paroxysm  occasioned  by  the  operation,  a  period  of  qui- 
escence and  freedom  from  dyspnoea  often  supervenes,  the  respirations  being 
performed  with  ease,  so  long  as  the  animal  remains  at  rest;  but  an  unusual 
respiratory  movement,  such  as  takes  place  at  the  commencement  of  a  struggle, 
induces  immediate  symptoms  of  suffocation, — the  current  of  air  carrying  in- 
wards the  arytenoid  cartilages,  which  are  rendered  passive  by  the  paralyzed 

vated  by  the  temporary  cessation  of  the  action.  But  such  persons  have  succeeded  better,  by 
holding  the  face  beneath  the  surface  of  water;  because  here  another  set  of  muscles  is  called 
into  action,  which  are  much  more  under  the  control  of  the  will,  than  are  those  of  respiration ; 
and  a  strong  volition  applied  to  these  can  prevent  all  access  of  air  to  the  lungs,  however 
violent  may  be  the  inspiratory  efforts. 


296  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

state  of  their  muscles;  and  these,  falling  upon  the  opening  of  the  glottis,  like 
valves  obstruct  the  entrance  of  air  into  the  lungs.  The  more  effort  is  made, 
the  greater  will  be  the  obstruction:  and  accordingly,  it  is  generally  necessary 
to  counteract  the  tendency  to  suffocation,  when  it  is  desired  to  prolong  the  life 
of  the  animal  after  this  operation,  by  making  an  opening  into  the  trachea.  Dr. 
Reid  further  ascertained  that  the  application  of  a  stimulus  to  the  inferior 
laryngeal  nerves,  when  separated  from  the  trunk,  would  occasion  distinct 
muscular  contractions  in  the  larynx;  whilst  a  corresponding  stimulus  applied 
to  the  superior  laryngeal  occasioned  no  muscular  movement,  except  in  the 
crico-thyroid  muscle.  But  when  the  superior  laryngeals  were  entire,  irritation 
of  the  mucous  surface  of  the  larynx,  or  of  the  trunks  themselves,  produced 
contraction  of  the  glottis  and  efforts  to  cough ;  effects  which  were  at  once  pre- 
vented by  dividing  those  nerves,  and  thereby  cutting  off  their  communication 
with  the  Medulla  Oblongata.  There  can  be  no  doubt,  then,  that  the  superior 
and  inferior  laryngeal  branches  constitute  the  circle  of  incidents  and  motor 
nerves,  by  which  the  aperture  of  the  glottis  is  governed,  and  by  which  any 
irritation  of  the  larynx  is  made  to  close  the  passage,  so  as  to  prevent  the 
entrance  of  improper  substances;  whilst  the  superior  laryngeal  nerve  also  ex- 
cites the  muscles  of  expiration,  so  as  to  cause  the  violent  ejection  of  a  blast  of 
air,  by  which  the  offending  gas,  fluid,  or  solid,  may  be  carried  off.  The  effect 
of  carbonic  acid  in  causing  spasmodic  closure  of  the  glottis  is  well  known ; 
and  affords  a  beautiful  example  of  the  protective  character  of  this  system  of 
nerves.  The  mucous  surface  of  the  trachea  and  bronchi  appears,  from  the 
experiments  of  Valentin,  to  be  endowed  with  excitability,  so  that  stimuli  ap- 
plied to  it  produce  expiratory  movements;  and  this  evidently  operates  through 
the  branches  of  the  par  vagum  distributed  upon  the  membrane.  Here,  as 
elsewhere,  we  find  that  a  stimulus  applied  to  the  surface  has  a  much  more 
decided  influence  than  irritation  of  the  trunk  of  the  nerve  supplying  it. 

380.  The  actions  of  sighing,  yawning,  sobbing,  laughing,  coughing,  and 
sneezing,  are  nothing  else  than  simple  modifications  of  the  ordinary  movements 
of  respiration,  excited  either  by  mental  emotions,  or  by  some  stimulus  originat- 
ing in  the  respiratory  organs  themselves. — Sighing  is  nothing  more  than  a  very 
long-drawn  inspiration,  in  which  a  larger  quantity  of  air  than  usual  is  made  to 
enter  the  lungs.  This  is  continually  taking  place  to  a  moderate  degree  ;  and 
we  notice  it  particularly,  when  the  attention  is  released,  after  having  been 
fixed  upon  an  object;  which  has  excited  it  strongly,  and  which  has  prevented 
our  feeling  the  insufficiency  of  the  ordinary  movements  of  respiration.  Hence 
this  action  is  only  occasionally  connected  with  mental  emotion. — Yawning  is 
a  still  deeper  inspiration,  which  is  accompanied  by  a  kind  of  spasmodic  con- 
traction of  the  muscles  of  the  jaw,  and  also  by  a  very  great  elevation  of  the 
ribs,  in  which  the  scapulae  partake.  The  purely  involuntary  character  of  this 
movement  is  sometimes  seen,  in  a  remarkable  manner,  in  cases  of  palsy;  in 
which  the  patient  cannot  raise  his  shoulder  by  an  effort  of  the  will,  but  does 
so  in  the  act  of  yawning.  Nevertheless  this  act  may  be  performed  by  the 
will,  though  not  completely;  and  it  is  one  that  is  particularly  excited  by 
an  involuntary  tendency  to  imitation ;  as  every  one  must  have  experienced, 
who  has  ever  been  in  company  with  a  set  of  yawners. — Sobbing  is  the  con- 
sequence of  a  series  of  short  convulsive  contractions  of  the  diaphragm ;  and  it 
is  usually  accompanied  by  a  closure  of  the  glottis,  so  that  no  air  really  enters. 
In  Hiccup,  the  same  convulsive  respiratory  movement  occurs ;  and  the  glottis 
closes  suddenly  in  the  midst  of  it;  the  sound  is  occasioned  by  the  impulse  of 
the  column  of  air  in  motion,  against  the  glottis.— In  Laughing,  a  precisely 
reverse  action  takes  place ;  the  muscles  of  expiration  are  in  convulsive  move- 
ment, more  or  less  violent,  and  send  out  the  breath  in  a  series  of  jerks,  the 
glottis  being  open.  This  sometimes  goes  on,  until  the  diaphragm  is  more 


REFLEX  ACTIONS. RESPIRATORY  MOVEMENTS.  297 

arched,  and  the  chest  is  more  completely  emptied  of  air,  than  it  could  be  by 
an  ordinary  movement  of  expiration. — The  act  of  Crying,  though  occasioned 
by  a  contrary  emotion,  is,  so  far  as  the  respiration  is  concerned,  very  nearly 
the  same  as  the  last.  Every  one  knows  the  effect  of  mixed  emotions,  in  pro- 
ducing an  expression  of  them,  which  is  "  between  a  laugh  and  a  cry." — The 
greater  part  of  the  preceding  movements  seem  to  belong  as  much  to  the  con- 
sensual  or  emotional,  as  to  the  purely  reflex  group  of  actions  ;  for  whilst  they 
are  sometimes  the  result  of  peculiar  states  of  the  respiratory  organs,  or  of  the 
bodily  system  in  general,  they  may  also  be  called  forth  by  influences,  which 
operate  directly  through  the  senses,  or  which  excite  the  emotions.  Thus, 
whilst  Sighing  and  Yawning  often  occur  as  simple  results  of  deficient  aeration, 
they  may  be  brought  on, — the  former  by  a  depressed  state  of  the  feelings, — 
the  latter  by  the  mere  sight  of  the  act  in  another  person.  The  actions  of 
Laughter  and  Crying  never  seem  to  originate  in  the  respiratory  system ;  but 
to  be  always  either  expressions  of  the  emotions,  or  simple  results  of  sensa- 
tions,— crying  being  connected  with  the  sense  of  pain, — and  laughter  with  that 
of  tickling.  The  origin  of  the  act  of  Hiccup  does  not  seem  very  clear ;  but 
the  movement  is  probably  of  a  purely  reflex  nature. 

381.  The  purposes  of  the  acts  of  Coughing  and  Sneezing  are,  in  both 
instances,  to  expel  substances  from  the  air-passages,  which  are  sources  of  irri- 
tation there ;  and  this  is  accomplished  in  both,  by  a  violent  expiratory  effort, 
which  sends  forth  a  blast  of  air  from  the  lungs. — Coughing  occurs,  when  the 
source  of  irritation  is  situated  at  the  back  of  the  mouth,  in  the  trachea,  or 
bronchial  tubes.     The  irritation  may  be  produced  by  acrid  vapours,  or  by 
liquids  or  solids,  that  have  found  their  way  into  these  passages ;  or  by  secre- 
tions which  have  been  poured  into  them  in  unusual  quantity,  as  the  result  of 
disease;  or  by  the  simple  entrance  of  air  (especially  if  cold),  when  the  mem- 
brane is  in  a  peculiarly  irritable  state.     Any  of  these  causes  may  produce  an 
impression  upon  the  excitor  fibres  of  the  Par  Vagum,  which,  being  conveyed 
to  the  Medulla  Oblongata,  shall  give  rise  to  the  transmission  of  motor  impulses 
to  the  several  muscles,  that  shall  combine  them  in  the  act  of  coughing.    This 
act  consists, — 1st,  in  a  long  inspiration,  which  fills  the  lungs;  2d,  in  the 
closure  of  the  glottis  at  the  moment  when  expiration  commences ;  and  3d,  in 
the  bursting  open  (as  it  were)  of  the  glottis,  by  the  violence  of  the  expiratory 
movement;  so  that  a  sudden  blast  of  air  is  forced  up  the  air-passages,  carrying 
before  it  anything  that  may  offer  an  obstruction. — The  difference  between 
coughing  and  Sneezing  consists  in  this, — that  in  the  latter,  the  communication 
between  the  larynx  and  the  mouth  is  partly  or  entirely  closed,  by  the  drawing 
together  of  the  sides  of  the  velum  palati  over  the  back  of  the  tongue;  so  that 
the  blast  of  air  is  directed,  more  or  less  completely,  through  the  nose,  in  such 
a  way  as  to  carry  off  any  source  of  irritation  that  may  be  present  there. — It  is 
difficult  to  say  how  far  these  actions  are  simply  reflex ;  or  how  far  they  may 
require  the  stimulus  of  sensation  for  their  performance. 

382.  Deglutition  and  Defecation. — Another  very  important  function  of  the 
Spinal  Cord  (and  of  the  ganglia  corresponding  to  it  in  the  Invertebrata),  is  the 
control  which  it  exercises  over  the  entrance  and  termination  of  the  Alimentary 
Canal;  and  this  reflex  action  might  probably  be  traced  in  some  animals,  in 
which  the  necessity  for  that  of  Respiration  does  not  exist.    In  all  beings  which 
are  unequivocally  of  an  animal  character,  a  stomach  or  digestive  cavity  exists ; 
and  a  means  must  be  provided  for  the  introduction  of  food  into  it.     This  is 
partly  accomplished  by  the  power,  with  which  its  entrance  is  endowed,  of 
contracting  upon,  and  of  attempting  to  draw  inwards,  whatever  comes  in  con- 
tact with  it;  as  we  may  readily  observe  in  the  Star-Fish,  or  Sea-Anemone, 
where  what  is  commonly  regarded  as  the  mouth,  is  really  the  aperture  of  the 
stomach.    But  we  almost  always  find  some  more  special  apparatus,  for  bring- 


298  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

ing  food  within  reach  of  this  orifice.  In  the  Sea-Anemone,  the  Hydra,  and 
other  Polypes,  for  example,  we  find  that  aperture  surrounded  by  tentacula; 
which  have  an  evident  tendency  to  lay  hold  of  anything  that  touches  them,  so 
as  to  bring  it,  by  their  contraction,  within  reach*  of  the  muscles  immediately 
surrounding  the  aperture.  This  is  just  the  purpose  of  the  pharyngeal  muscles 
of  Man.  The  lower  part  of  the  oesophagus,  near  its  termination  in  the  sto- 
mach, has  the  same  simple  tendency  to  contraction  from  above  downwards 
(so  as  to  convey  into  the  stomach  anything  which  is  brought  within  its  reach), 
as  have  the  muscles  surrounding  the  mouth  of  the  Polype;  but  there  is  need 
of  some  more  complex  apparatus,  for  the  purpose  of  laying  hold  of  the  food, 
and  of  conducting  it  into  its  grasp.  This  is  provided  for,  in  the  higher  animals, 
in  the  muscles  of  that  funnel-like  entrance  to  the  oesophagus,  which  is  called 
the  Pharynx.  The  actions  of  these  are  most  distinctly  reflex;  and  it  is  inte- 
resting to  remark,  that  the  movements  can  neither  be  caused  nor  controlled  by 
the  direct  influence  of  the  will.  In  the  case  of  the  movements  of  respiration, 
we  found  sufficient  provision  made  for  their  constant  maintenance;  and  yet, 
for  secondary  purposes,  they  were  placed  in  a  considerable  degree  under  the 
control  of  the  brain.  But  here  there  are  no  secondary  purposes  to  be  an- 
swered ;  the  introduction  into  the  stomach  of  food,  brought  by  the  will  within 
reach  of  the  pharyngeal  muscles,  is  the  only  object  contemplated  by  them; 
and  they  are  accordingly  placed  under  the  sole  government  of  the  Spinal  Cord. 

383.  No  attempts,  on  our  own   part,  will  succeed  in   producing  a  really 
voluntary  act  of  Deglutition.     In  order  to  excite  it,  we  must  supply  some 
stimulus  to  the  fauces.     A  very  small  particle  of  solid  matter,  or  a  little  fluid 
(saliva,  for  instance),  or  the  contact  of  the  back  of  the  tongue  itself,  will  be 
sufficient ;  but  without  either  of  these  we,  cannot  swallow  at  will.     Nor  can 
we  restrain  the  tendency,  when  it  is   thus  excited  by  a  stimulus ;  every  one 
knows  how  irresistible  it  is,  when  the  fauces  are  touched  in  any  unusual  man- 
ner ;  and   it  is  equally  beyond  the  direct  control  of  the  will,  in  the  ordinary 
process  of  eating, — voluntary  as  we  commonly  regard  this.     The  only  mode 
in  which  the  will  can  influence  it,  is  by  regulating  the  approach  of  the  stimu- 
lus necessary  to   excite  it;  thus,  we  voluntarily  bring  a  morsel  of  food,  or  a 
little  fluid,  into  contact  with  the  surface  of  the  fauces,  and  an  act  of  deglutition 
is  then  involuntarily  excited :  or  we  may  voluntarily  keep  all  stimulus  at  a 
distance  ;  and  no  effort  of  the  will  can  then  induce  the  action.     Moreover, 
this  action  is  performed,  like  that  of  respiration,  when  the  power  of  the  will 
is  suspended,  as  in  profound  sleep,  or  in  apoplexy  affecting  only  the  brain; 
and  it  does  not  seem  to  be  at  all  affected  by  the  entire  removal  of  the  brain, 
in  an  animal  that  can  sustain  the  shock  of  the  operation ;  being  readily  ex- 
citable, on  stimulating  the  fauces,  so  long  as  the  nervous  structure  retains  its 
functions.     This  has  been   experimentally  proved  by  Dr.  M.  Hall;  and  it 
harmonizes  with  the  natural  experiment  sometimes  brought  under  our  notice 
in  the  case  of  an  anencephalous  infant,  in  which  the  power  of  swallowing 
seems  as  vigorous  as  in  the  perfect  one.     But,  if  the  nervous  circle  be  de- 
stroyed, either  by  division  of  the  trunks,  or  by  injury  of  any  kind  to  the  por- 
tion of  the  nervous  centres  connected  with  them,  the  action  can   no  longer  be 
performed;  and  thus  we  see  that,  when  the  effects  of  apoplexy  are  extending 
themselves   from  the  brain  to  the   spinal  cord,  whilst  the  respiration  becomes 
stertorous,  the  power  of  Deglutition  is  lost,  and  then  respiration  also  speedily 
ceases. 

384.  Our  knowledge  of  the  nerves   specially  concerned  in  this  action  is 
principally  due  to  the  very  careful  and  well-conducted  experiments  of  Dr.  J. 
Reid.*     The  distribution  of  the  Glosso-Pharyngeal  evidently  points  it  out  as 

*  Edinb.  Med.  and  Surg.  Journ.,  vol.  xlix. 


ACTIONS  PRELIMINARY  TO  DEGLUTITION.  299 

in  some  way  connected  with  it ;  and  this,  when  carefully  examined,  discloses 
the  important  fact,  that  the  nerve  scarcely  sends  any  of  its  branches  to  the 
muscles  which  they  enter ;  but  that  these  mostly  pass  through  them,  to  be 
distributed  to  the  super] acent  mucous  surface  of  the  tongue  and  fauces. 
Further,  when  the  trunk  is  separated  from  the  nervous  centres,  irritation 
scarcely  ever  produces  muscular  movements.  Hence  it  is  not  in  any  great 
degree  an  efferent  or  motor  nerve  ;  and  its  distribution  would  lead  us  to  sup- 
pose its  function  to  be,  the  conveyance  of  impressions  from  the  surface  of  the 
Fauces  to  the  Medulla  Oblongata.  This  inference  is  fully  confirmed  by  the 
fact,  that,  so  long  as  its  trunk  is  in  connection  with  the  Medulla  Oblongata, 
and  the  other  parts  are  uninjured,  pinching,  or  other  severe  irritation  of  the 
Glosso-Pharyngeal,  will  often  excite  distinct  acts  of  deglutition.  Such  irrita- 
tion, however,  may  excite  only  convulsive  twitches,  instead  of  the  regular 
movements  of  swallowing;  and  it  is  evident  that,  here,  as  elsewhere,  the 
impressions  made  upon  the  extremities  of  the  nerves  are  much  more  power- 
ful exciters  of  reflex  movement,  than  those  made  upon  the  trunk,  though  the 
latter  are  more  productive  of  pain.  It  was  further  observed  by  Dr.  Reid,  that 
this  effect  was  produced  by  pinching  the  pharyngeal  branches  only  ;  no  irrita- 
tion of  the  lingual  division  being  effectual  to  the  purpose. 

385.  If,  then,  the  muscles  of  deglutition  are  not  immediately  stimulated  to 
contraction  by  the  Glosso-Pharyngeal  nerve,  it  remains  to  be  inquired,  by 
what  nerve  the  motor  influence  is  conveyed  to  them  from  the  Medulla  Oblon- 
gata ;  and  Dr.  Reid  has  been  equally  successful  in  proving,  that  this  function 
is  chiefly  performed  by  the  pharyngeal  branches  of  the  Par  Vagum.  Ana- 
tomical examination  of  their  distribution  shows,  that  they  lose  themselves  in 
the  muscles  of  the  pharynx  ;  and  whilst  no  decided  indications  of  suffering 
can  be  produced  by  irritating  them,  evident  contractions  are  occasioned,  when 
the  trunk,  separated  from  the  brain,  is  pinched  or  otherwise  stimulated.  It 
appears,  however,  that  neither  is  the  Glosso-Pharyngeal  the  sole  excitor 
nerve,  nor  are  the  pharyngeal  branches  of  the  Par  Vagum  the  sole  motor 
nerves,  concerned  in  deglutition ;  for  after  the  former  has  been  perfectly  di- 
vided on  each  side,  the  usual  movements  can  still  be  excited,  though  with  less 
energy;  and,  after  the  latter  have  been  cut,  the  animal  retains  the  means  of 
forcing  small  morsels  through  the  pharynx,  by  the  action  of  the  muscles  of 
the  tongue  and  neck.  From  a  careful  examination  of  the  actions  of  degluti- 
tion, and  of  the  influence  of  various  nerves  upon  them,  Dr.  Reid  draws  the 
following  conclusions : — The  excitor  impressions  are  conveyed  to  the  Me- 
dulfa  Oblongata  chiefly  through  the  Glosso-Pharyngeal,  but  also  along  the 
branches  of  the  Fifth  pair  distributed  upon  the  fauces,  and  probably  along  the 
branches  of  the  Superior  Laryngeal  distributed  upon  the  pharynx.  The 
motor  influence  passes  chiefly  along  the  pharyngeal  branches  of  the  Vagus  ; 
along  the  branches  of  the  Hypo-glossal,  distributed  to  the  muscles  of  the 
tongue,  and  to  the  sterno-hyoid,  sterno-thyroid,  and  thyro-hyoid  muscles  ; 
along  the  motor  filaments  of  the  Recurrents,  ramifying  upon  the  larynx ; 
along  some  of  the  branches  of  the  Fifth,  supplying  the  elevator  muscles  of  the 
lower  jaw;  along  the  branches  of  the  Portio  Dura,  ramifying  upon  the  digas- 
tric and  stylo-hyoid  muscles,  and  upon  the  muscles  of  the  lower  part  of  the 
face  ;  and  probably  along  some  of  the  branches  of  the  Cervical  plexus,  which 
unite  themselves  to  the  descendens  noni. 

386.  When  the  food  has  been  propelled  downwards  by  the  Pharyngeal 
muscles  as  far  as  their  action  extends,  its  further  progress  through  the  (Eso- 
phagus is  effected  by  the  peristaltic  movement  of  the  muscular  coat  of  the 
tube  itself.  This  movement  is  not,  however,  due  only  to  the  direct  stimulus 
of  the  muscular  fibre  by  the  pressure  of  the  food,  as  it  seems  to  be  in  the 
lower  part  of  the  alimentary  canal ;  for  Dr.  J.  Reid  has  found,  by  repeated 


300  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

experiment,  that  the  continuity  of  the  oesophageal  branches  of  the  Par  Vagum 
with  the  Spinal  Cord,  is  necessary  for  the  rapid  propulsion  of  the  food ;  so 
that  it  can  scarcely  be  doubted,  that  an  impression  made  upon  the  mucous 
surface  of  the  oesophagus,  conveyed  by  the  afferent  fibres  of  these  nerves  to 
the  Medulla  Oblongata,  and  reflected  downwards  along  the  motor  fibres,  is 
the  real  cause  of  the  muscular  contraction.  If  the  Par  Vagum  be  divided  in 
the  rabbit,  on  each  side,  above  the  cesophageal  plexus,  but  below  the  pharyn- 
geal  branches,  and  the  animal  be  then  fed,  it  is  found  that  the  food  is  delayed 
in  the  oesophagus,  which  becomes  greatly  distended.  Further,  if  the  lower 
extremity  of  the  par  vagum  be  irritated,  distinct  contractions  are  seen  in  the 
cesophageal  tube,  proceeding  from  above  downwards,  and  extending  over  the 
cardiac  extremity  of  the  stomach.  We  have  here,  then,  a  distinct  case  of 
reflex  action  without  sensation,  occurring  as  one  of  the  regular  associated 
movements  in  the  natural  condition  of  the  animal  body  ;  and  it  is  very  inte- 
resting to  find  this  following  upon  a  reflex  action  with  sensation  (that  of  the 
pharynx),  and  preceding  a  movement  which  is  altogether  unconnected  with 
the  Spinal  Cord  (that  of  the  lower  part  of  the  alimentary  canal).  The  use  of 
sensation  in  the  former  case  will  presently  appear.  The  muscular  fibres  of 
the  oesophagus  are  also  excitable,  though  usually  in  a  less  degree,  by  direct 
stimulation ;  for  it  appears  that,  in  some  animals  (the  Dog,  for  example), 
section  of  the  pneumogastric  does  not  produce  that  check  to  the  propulsion  of 
the  food,  which  it  occasions  in  the  Rabbit;  and  even  in  the  Rabbit,  as  Dr. 
M.  Hall*  has  remarked,  the  simple  contractility  of  the  muscular  fibre  occa- 
sions a  distinct  peristaltic  movement  along  the  tube,  after  its  nerves  have  been 
divided;  causing  it  to  discharge  its  contents,  when  cut  across.  Such  a  move- 
ment, indeed,  seems  to  take  place  in  something  of  a  rhythmical  manner  (that 
is,  at  short  and  tolerably  regular  intervals),  whilst  a  meal  is  being  swallowed; 
but  as  the  stomach  becomes  full,  the  intervals  are  longer,  and  the  wave-like 
contractions  less  frequent. — These  movements  are  reversed  in  Vomiting  ;  and 
this  reversion  has  been  observed,  even  after  the  separation  of  the  stomach 
from  the  oesophagus,  as  a  consequence  of  the  injection  of  tartar  emetic  into 
the  veins. 

a.  It  will  be  desirable  here  to  revert  for  a  short  time  to  the  actions,  which,  in  the  higher 
animals,  precede  those  of  Deglutition.  There  can  be  no  doubt  that,  in  the  Human  being, 
the  motions  adapted  to  the  Ingestion  and  Mastication  of  aliment  originally  result,  in  part  at 
least,  from  distinct  operations  of  the  Will ;  but  it  would  appear  almost  equally  certain  that, 
in  time,  they  come  to  be  of  so  habitual  a  character,  that  the  will  only  exerts  a  general  con- 
trolling influence  over  them,  each  individual  act  being  directly  excited  by  sensation.  Every 
one  is  conscious  that  the  act  of  mastication  may  be  performed  as  well,  when  the  mind  is 
attentively  dwelling  on  some  other  object,  as  when  directed  to  it ;  but,  in  the  former  case, 
one  is  rather  apt  to  go  on  chewing  and  rechewing  what  is  already  fit  to  be  swallowed, 
simply  because  the  will  does  not  exert  itself  to  check  the  action,  and  to  carry  the  food  back- 
wards within  the  reach  of  the  muscles  of  deglutition.  We  now  see  why  sensation  should 
be  associated  unth  the  latter  process,  though  not  essential  to  it.  The  conveyance  of  food  back- 
wards to  the  fauces  is  a  distinctly  voluntary  act;  and  it  is  necessary  that  it  should  be  guided 
by  the  sensation,  which  there  results  from  the  contact  it  induces.  If  the  surface  of  the 
pharynx  were  as  destitute  of  sensation,  as  is  the  lower  part  of  the  oesophagus,  we  should  not 
know  when  we  had  done  what  was  necessary  to  excite  its  muscles  to  operation. — The 
muscles  concerned  in  the  Mastication  of  food  are  nearly  all  supplied  by  the  third  branch  of 
the  Fifth  pair,  a  large  proportion  of  which  is  well  known  to  have  a  motor  character.  Many 
of  these  muscles,  especially  those  of  the  cheeks,  are  also  supplied  by  the  Portio  Dura  of  the 
Seventh;  and  yet,  if  the  former  be  paralyzed,  this  cannot  stimulate  them  to  the  necessary 
combined  actions.  Hence  we  see  that  the  movements  are  of  an  associated  character,  their 
due  performance  being  dependent  on  the  part  of  the  nervous  centres,  from  which  the  motor 
influence  originates.  If  the  Fifth  pair,  on  the  other  hand,  be  uninjured,  whilst  the  Portio 
Dura  is  paralyzed,  the  movements  of  Mastication  are  performed  without  difficulty ;  whilst 
those  connected  in  any  way  with  the  Respiratory  function,  or  with  Expression,  are  para- 
lyzed. 

*  Third  Memoir  on  the  Nervous  System,  §  201. 


ACTIONS  PRELIMINARY  TO  DEGLUTITION.  301 

b.  Comparative  Anatomy  supplies  us  with  the  key  to  the  explanation  of  these  phenomena. 
It  has  been  seen  that,  in  the  lower  animals,  the  Respiratory  organs  are  completely  uncon- 
nected with  the  mouth,  and  that  a  very  distinct  set  of  muscles  is  provided  to  keep  them  in 
action.     These  muscles  have  distinct  ganglia  as  the  centres  of  their  operations ;  and  these 
ganglia  are  only  connected  indirectly  with  those  of  the  sensori-motor  system.     The  same 
would  appear  to  be  the  case,  in  regard  to  the   introduction  of  the  food  into  the   digestive 
apparatus.     It  has  been  shown  that  the  muscles  concerned  in  this  operation  have  their  own 
centres, — the  Stomato-gastric  and  Pharyngeal  ganglia,  which  are  not  very  closely  connected 
with  the  cephalic,  or  with  the  respiratory,  or  with  those  of  general  locomotion.     Now  in  the 
Vertebrata,  the  distinct  organs  have  been  so  far  blended  together,  that  the  same  muscles 
serve  the  purposes  of  both;  but  the  different  sets  of  movements  of  these  muscles  are  excited 
by  different  nerves;  and  the  effect  of  division  of  either  nerve,  is  to  throw  the  muscle  out  of 
connection  with  the  function,  to  which  that  nerve  previously  rendered  it  subservient, — as 
much  as  if  the  muscle  were  separated   from  the  nervous  system  altogether.     There  is  an 
apparent  exception  to  this  view  of  the  matter,  in  the  case  of  the  Portio  Dura;  this  being  the 
source  of  those  movements  of  the  upper  lip,  which,  in  many  animals,  are  essential  to  the 
prehension  of  food.     These  movements,  however,  are  dependent  upon  sensations  conveyed 
through  the  Fifth  pair.*  being  completely  checked  by  division  of  its  infra-orbital  trunk;  and 
it  can  scarcely  be  doubted,  from  their  general  character,  that  they  are  of  a  strictly  voluntary 
nature,  and  are  not  to  be  regarded  as  part  of  the  reflex  associated  movements  in  which  that 
nerve  is  concerned. 

c.  Now  although,  in  the  adult  Human  being,  the  movements  required  to  convey  the  food 
to  the  pharynx  are  under  the  control  of  the  Will,  if  not  constantly  dependent  upon  it,  there 
is  good  reason  to  believe  that  this  is  not  the  case  in  regard  to  those  remarkable  associated 
movements,  which  constitute  the  act  of  suction  in  the  Infant.     The  experiments  provided 
for  us  by  nature,  in  the  production  of  anencephalous  monstrosities,  fully  prove   that  the 
nervous  connection  of  the  lips  and  respiratory  organs  with  the  Spinal  Cord,  is  alone  sufficient 
for  its  execution;  and  Mr.  Grainger  has   sufficiently  established  the  same,  by  experiment 
upon  puppies  whose  brain  had  been  removed.     He  adds  that,  as  one  of  the  puppies  lay  on 
its  side,  sucking  the  finger  which  was  presented  to  it,  it  pushed  out  its  feet  in  the  same 
manner  as  young  pigs  exert  theirs  against  the  sow's  dugs.     On  the  whole,  however,  the  act 
of  suction  belongs  more  to  the  Respiratory  ganglion  (so  to  speak)  than  to  the  Stomato-gastric 
system  of  nerves ;  and  hence  we  can  understand  why,  even  in  the  highest  animals,  it  should 
be  purely  reflex;  the  movements  of  Respiration  being  so  from  the  first,  whilst  those  ordi- 
narily concerned  at  a  later  period  in  the  Ingestion  of  the  food  are  more  directed  by  sensa- 
tion and  volition.     The  actions  of  the  mammary  foetus  of  the  kangaroo,  described  by  Mr. 
Morgan,  furnish  a  very  interesting  exemplification  of  the  same  function  of  the  Spinal  Cord; 
this  creature,  resembling  an  earth-worm  in  appearance,  and  only  about  fourteen  lines  in 
length,  with  a  brain  corresponding  in  degree  of  development  to  that  of  a  human  foetus  of 
the  ninth  week,  executes  regular,  but  slow,  movements  of  respiration,  adheres  firmly  to  the 
point  of  the  nipple,  and  moves  its  limbs  when  disturbed.     The  milk  is  forced  into  the  oeso- 
phagus by  a  compressor  muscle,  with  which  the  mamma  of  the  parent  is  provided.    "  Can  it 
be  imagined,"  very  justly  asks  Mr.  Grainger,  "that  in  this  case  there  are  sensation  and  vo- 
lition, in  what  can  be  proved  anatomically  to  be  a  foetus?" 

387.  The  Sphincter  muscle,  which  guards  the  Cardiac  orifice  of  the 
stomach,  appears  to  be  under  the  influence  of  the  Spinal  system  of  nerves. 
It  is  usually  closed;  but  it  opens  when  there  is  a  sufficient  pressure  on  it, 
made  by  the  accumulated  food  propelled  by  the  movements  of  the  oesophagus 
above;  and  it  then  closes  again,  so  as  to  retain  the  food  in  the  stomach. 
That  this  closure  is  due  to  reflex  action  appears  from  the  fact  that,  when  the 
nerves  supplying  the  muscle  are  divided,  the  sphincter  no  longer  contracts, 
and  the  food  regurgitates  into  the  oesophagus.  The  opening  of  the  cardiac 
orifice  is  one  of  the  first  of  the  changes,  which  occur  in  the  act  of  vomiting. — 
With  regard  to  the  degree,  in  which  the  movements  of  the  Stomach,  that  have 
so  important  a  share  in  the  Digestive  operation,  are  dependent  upon  the  Spinal 
system,  and  are  consequently  of  a  reflex  nature,  it  is  difficult  to  speak  with 

*  Hence  originated  one  of  Sir  C.  Bell's  early  errors.  He  found  that  an  ass,  in  which  the 
infra-orbital  branch  of  the  fifth  was  divided,  would  not  pick  up  oats  with  its  lip,  although 
they  were  in  contact  with  it;  hence  he  concluded  that  its  power  of  motion  was  destroyed, — 
when  it  was  in  reality  only  the  sensation  necessary  to  excite  the  will  to  cause  the  motion, 
that  was  deficient. 
26 


302  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

certainty,  owing  to  the  contradictory  results  obtained  by  different  experi- 
menters. These  contradictions,  however,  seem  partly  due  to  a  diversity  in 
the  nature  of  the  animals  experimented  on.  It  seems  to  be  well  established, 
by  the  researches  of  Reid,  Valentin,  and  others,  that  distinct  movements  may 
be  excited  in  the  Stomach  of  the  Rabbit,  if  distended  with  food,  by  irritating 
the  Par  Vagum  soon  after  the  death  of  the  animal;  these  movements  seem  to 
commence  from  the  cardiac  orifice,  and  then  to  spread  themselves  in  a  sort 
of  peristaltic  manner  along  the  walls  of  the  stomach;  but  no  such  movements 
can  be  excited  if  the  stomach  be  empty.  Various  experiments  upon  living 
animals  have  led  to  a  similar  conclusion ;  food  taken  in  shortly  before  or  sub- 
sequently to  its  division,  having  been  found  to  be  only  dissolved  on  the  sur- 
face of  the  mass,  where  it  was  in  contact  with  the  mucous  membrane.  But 
these  experiments  have  been  made  for  the  most  part  upon  Herbivorous 
animals,  such  as  horses,  asses,  and  rabbits ;  whose  food  is  bulky  and  difficult 
of  solution,  requiring  to  be  constantly  changed  in  its  position,  so  that  every 
part  of  it  may  be  successively  brought  to  the  exterior.  On  the  other  hand, 
Dr.  Reid  found,  in  his  experiments  upon  Dogs,  that,  after  the  first  shock  of 
the  operation  had  gone  off,  solution  of  the  food  in  the  stomach,  and  absorp- 
tion of  chyle,  might  take  place;  and  hence  it  may  be  inferred,  that  no  influ- 
ence of  this  nerve  upon  the  muscular  parietes  of  the  stomach  is  essential  to 
digestion  in  that  species.  This  conclusion  harmonizes  well,  therefore,  with 
,  the^fact  already  stated  respecting  the  absence  of  such  influence  in  the  lower 
parts  of  its  oesophagus ;  and  it  may,  perhaps,  be  explained  by  the  considera- 
tion, that  the  natural  food  of  the  dog  is  much  less  bulky  and  more  easy  of 
solution,  than  that  of  the  animals  already  named ;  so  that  there  is  not  so  much 
need  of  the  peculiar  movement,  which  is  in  them  so  important  an  aid  to  the 
process  of  reduction. — The  muscular  walls  of  the  stomach  appear  to  be  called 
into  reflex  contraction  in  the  act  of  Vomiting;  the  mechanism  of  which  will 
be  considered  hereafter  (§  505). 

388.  That  the  ordinary  peristaltic  movements  of  the  Intestinal  canal,  from 
the  stomach  to  the  rectum,  may  take  place  without  any  connection  with  the 
nervous  system,  being  due  to  the  direct  stimulation  of  the  contact  of  food, 
there  is  now  ample  evidence  ;  and  though  some  may  yet  be  found  to  deny  the 
Hallerian  doctrine,  that  muscular  fibre  possesses  in  itself  the  property  of  con- 
tractility, so  much  additional  evidence  of  its  truth  has  been  recently  adduced 
whilst  the  doctrine  itself  is  so  conformable  to  the  analogy  supplied  by  other 
vital  phenomena,  that  it  will  be  here  unhesitatingly  adopted.  (See  Chapter  V.) 
Some  Physiologists  still  suppose,  that  the  peristaltic  movements  of  the  ali- 
mentary canal  are  due  to  a  sort  of  reflex  action,  taking  place  through  the 
ganglia  of  the  Sympathetic  system  of  nerves,  especially,  of  course,  the  semi- 
lunar.     This  supposition,  however,  has  little  or  no  evidence  to  support  it;  for 
it  has  been  fully  proved  that  the   muscular  contractions  will  continue,  long 
after  the  tube  has   been  separated  from  its  nervous  connections  through  its 
whole  extent ;  and  the  only  evidence  in  its  favour  is  derived  from  the  con- 
tractions, which  may  sometimes  be  induced  in  parts  of  the  tube  which  are  at 
rest,  when  the  Sympathetic  nerves  supplying  them  are  irritated.     The  ex- 
periments of  Valentin,  however, — by  which  the  fact  that  such  contractions 
may  be  induced  (which  has  been  denied  by  some)  is  clearly  substantiated, — 
also  show  that  the  motor  influence  does  not  originate  in  the  Sympathetic  gan- 
glia, but  in  the  Spinal  Cord.     The  following  are  the  general  results  of  up- 
wards of  three  hundred  experiments,  so  far  as  they  apply  to  this  subject. — 
The  pharynx  may  not  only  be  excited  to  contraction  by  irritation  of  the  pha- 
ryngeal  branches  of  the  !Par  Vagum,  or  of  the  roots  of  the  Spinal  Accessory, 
from  which  their  motor  power  is  derived  (as  will  be  hereafter  explained),  but 
also  by  stimulating  the  roots  of  the  first  two  Cervical  nerves ;  and  the  lower 
* 


REFLEX  ACTIONS. MOVEMENTS  OF  STOMACH.  303 

part  of  the  oesophagus  in  the  neck  is  made  to  contract  peristaltically  from 
above  downwards,  by  irritation  of  the  roots  of  the  first  three  Cervical  nerves, 
and  of  the  cervical  portion  of  the  Sympathetic,  through  which  last  the  former 
evidently  operate.  The  thoracic  portion  of  the  O3sophagus  is  made  to  con- 
tract, by  irritation  of  the  lowest  Sympathetic  ganglion  of  the  neck,  and  of 
the  higher  thoracic  ganglia,  and  also  of  the  roots  of  the  lower  Cervical  spinal 
nerves.  Muscular  contractions  of  the  stomach  are  produced,  by  irritation  of 
the  roots  of  the  4th,  5th,  6th,  and  7th  Cervical  nerves,  and  of  the  first  tho- 
racic in  the  rabbit ;  so  that  a  distinct  furrow  is  evident  between  the  cardiac 
and  pyloric  portion  of  the  viscus  ;  and  the  lower  the  nerve  irritated,  the 
nearer  the  pylorus  do  the  contractions  extend.  Irritation  of  the  first  thoracic 
ganglion  of  the  Sympathetic  produces  the  same  effect.  Contractions  of  the 
intestinal  tube,  varying  in  place  according  to  the  part  of  the  Spinal  Cord  ex- 
perimented on,  may  be  excited  by  irritation  of  the  roots  of  the  dorsal,  lumbar, 
and  sacral  nerves,  and  of  the  trigeminus ;  and  similar  effects  are  produced  by 
irritation  of  the  lower  part  of  the  thoracic  portion,  of  the  lumbar,  and  of  the 
sacral  portions  of  the  Sympathetic, — also  of  the  splanchnic,  and  of  the  gastric 
plexus. 

389.  From  these  facts  it  is  evident,  that  the  movements  of  the  Intestinal 
tube  may  be  influenced  by  the   Spinal  Cord  ;  and   that  what  is  commonly 
termed  the  Sympathetic  nerve,  is  the  channel  of  that  influence,  by  the  fibres 
which  it  derives  from  the  Spinal  system.     But  it  by  no  means  thence  follows, 
that  the  ordinary  peristaltic  actions  of  the  muscles  in  question  are  dependent 
on  a  stimulus  reflected  through  the  spinal  cord,  rather  than  on  one  directly 
applied  to  themselves.     It  is  clear  that,  although  these  movements  are  of  the 
first  importance  to  the  welfare  of  the  system,  such  means  of  sustaining  them 
are  feeble,  compared  to  those  which  we  find  provided  for  the  maintenance  of 
the  distinctly-reflex  actions   of  deglutition,  respiration,  &c.     The  difficulty 
with  which  any  evidence  can  be  obtained  of  the  connection,  is  a  sufficient 
proof  of  this.     On  the  other  hand,  we  do  know  that  these  peristaltic  move- 
ments are  influenced  by  particular  states  of  mind,  or  by  conditions  of  the  bodily 
system  ;  and  the  connection  just  traced  satisfactorily  accounts  for  this,  and  is 
itself  sufficiently  explained.     The  intestinal  tube,  then,  from  the  stomach  to 
the  rectum  is  not  dependent  upon  the   Spinal  cord  for  its  contractility,  but  is 
enabled  to  propel  its  contents  by  its  own  inherent  powers  ;  still  we  find  that 
here,  as  in  other  instances,  the  nervous   centres  exert  a  general  control  over 
even  the  Organic  functions, — doubtless  for  the  purpose  of  harmonizing  them 
with  each  other,  and  with  the  conditions  of  the  organs  of  Animal  life. 

390.  The  Muscular  Coat  of  the  Bladder  appears,  like  that  of  the  Intestinal 
tube,  to  be  ordinarily  excited  to  contraction,  rather  by  direct  stimulation  than 
by  the  agency  of  the  Spinal  nerves.     It  is  not,  however,  altogether  removed 
from  the  influence  of  the  Spinal  Cord ;  for  the  experiments  of  Valentin  have 
shown  that  a  connection  exists,  as  in  the  former  case,  through  the  Sympathetic 
nerve,  affecting  not  only  the  bladder  but  also  the  ureters.     That  physiologist 
states,  that  a  very  distinct  and  powerful  peristaltic  action  of  the  ureter,  pro- 
ceeding from  the  kidneys  to  the  bladder,  may  be  produced,  by  irritating  the 
abdominal  ganglia  of  the  Sympathetic,  or  the  roots  of  the  superior  abdominal 
Spinal  nerves ;  and  that  strong  contractions  of  the  bladder  are  excited,  by  irri- 
tation of  the  inferior  portion  of  the  abdominal  Sympathetic,  but  especially  of 
its  sacral  portion,  and  of  the  roots  of  the  middle  and  inferior  nerves  of  the 
Spine.     In  these,  as  in  former  cases,  no  effect  is  produced  by  irritation  of  the 
Spinal  Nerves,  unless  the  portion  of  the  Sympathetic  connected  with  the  par- 
ticular organ  be  entire. 

391.  On  examining  the  outlets  by  which  the  excretions  are  voided,  we  find 
that  they  are  placed,  like  the  entrances,  under  the  guardianship  of  the  Spinal 
Cord;  subject,  however,  to  some  control  on  the  part  of  the  Will.     In  the 


304  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

lowest  animals,  the  act  of  discharging  excrementitious  matter  is  probably  as 
involuntary,  as  are  the  acts  immediately  concerned  in  the  introduction  of  nu- 
triment ;  and  it  is  performed  as  often  as  there  is  anything  to  be  got  rid  of. 
In  the  higher  classes,  however,  such  discharges  are  much  less  frequent ;  and 
reservoirs  are  provided,  in  which  the  excrementitious  matter  may  accumulate 
in  the  intervals.  The  associated  movements  required  to  empty  these,  are 
completely  involuntary  in  their  character ;  and  are  excited  by  the  quantity, 
or  stimulating  quality,  of  the  contents  of  the  reservoir.  But,  had  volition  no 
control  over  them,  great  inconveniences  would  ensue ;  hence  sensation  is  ex- 
cited by  the  same  stimulus,  which  produces  the  movements;  in  order  that, 
by  arousing  the  will,  the  otherwise  involuntary  motions  may  be  restrained 
and  directed. — There  can  be  little  doubt,  from  the  experiments  of  Dr.  M. 
Hall,  as  well  as  from  other  considerations,  that  the  associated  movements,  by 
which  the  contents  of  the  rectum  and  bladder  are  discharged,  correspond 
much  with  those  of  Respiration  ;  being  in  their  own  nature  excito-motor,  but 
capable  of  a  certain  degree  of  voluntary  restraint  and  assistance.  The  acts 
of  Defecation  and  Urination  chiefly  depend  upon  the  combined  contraction 
of  the  abdominal  muscles,  similar  to  that  which  is  concerned  in  the  expiratory 
movement ;  but,  the  glottis  being  closed,  and  the  diaphragm  fixed,  the  expulsor 
power  is  restricted  to  the  contents  of  the  abdominal  cavity  ;  and  so  long  as  the 
sphincter  of  the  cardia  remains  closed,  the  force  must  act  downwards,  upon 
the  walls  of  the  rectum  and  bladder, — the  contents  of  the  one  or  the  other  of 
these  cavities,  or  of  both,  being  expelled,  according  to  the  condition  of  their 
respective  sphincters.  These  actions  are  doubtless  assisted  by  the  contrac- 
tion of  the  walls  of  the  rectum  and  bladder  themselves;  for  we  sometimes  find 
their  agency  sufficient  to  expel  the  contents  of  the  cavities,  when  there  is  a 
total  paralysis  of  the  ordinary  expulsors, — provided  that  the  sphincters  be  at 
the  same  time  sufficiently  relaxed.  This  is  more  especially  the  case,  when 
their  power  is  augmented  by  increased  nutrition.  For  example,  in  many 
cases  of  disease  or  injury  of  the  Spinal  Cord,  the  bladder  ceases  to  expel 
its  contents,  through  the  interruption  of  the  circle  of  reflex  actions ;  but  after 
a  time,  the  necessity  for  drawing  off  the  urine  by  the  catheter  is  found  to 
exist  no  longer;  the  fluid  is  constantly  expelled  as  soon  as  it  has  accumulated 
in  small  quantities.  In  such  cases,  the  mucous  coat  is  found  after  death  to 
be  thickened  and  inflamed;  and  the  muscular  coat  to  be  greatly  increased  in 
strength,  and  contracted  upon  itself.  It  would  seem,  then,  that  the  abnormal 
irritability  of  the  mucous  membrane,  and  the  increased  nutrition  of  the  mus- 
cular substance  which  appears  consequent  upon  it,  enable  the  latter  to  expel 
the  urine  without  the  assistance  of  the  ordinary  expulsors. 

392.  On  the  other  hand,  the  sphincters  which  antagonize  the  expellent  ac- 
tion, are  usually  maintained  in  a  state  of  moderate  contraction,  so  as  to  afford 
a  constant  check  to  the  egress  of  the  contents  of  the  cavities ;  and  this  con- 
dition has  been  fully  proved  by  Dr.  M.  Hall,  to  result  from  their  connection 
with  the  Spinal  Cord,  ceasing  completely  when  this  is  interrupted.  But  the 
sphincters  are  certainly  in  part  controlled  by  the  will,  and  are  made  to  act  in 
obedience  to  the  warning  given  by  sensation  ;  and  this  voluntary  power  is 
frequently  destroyed  by  injuries  of  the  Brain,  whilst  the  Spinal  Cord  remains 
able  to  perform  all  its  own  functions,  so  that  discharge  of  the  urine  and 
fa3ces  occurs. — In  their  moderate  action,  the  expulsors  and  the  sphincters 
may  be  regarded  as  balancing  one  another,  so  far  as  their  reflex  action  is 
concerned, — the  latter  having  rather  the  predominance,  so  as  to  restrain  the 
operation  of  the  former.  But,  when  the  quantity  or  quality  of  the  contents 
of  the  cavity  gives  an  excessive  stimulus  to  the  former,  their  action  pre- 
dominates, unless  the  will  is  put  in  force  to  strengthen  the  resistance  of 
the  sphincter ;  this  we  are  frequently  experiencing,  sometimes  to  our  great 


REFLEX  ACTIONS. MOVEMENTS  OF  GENITAL  ORGANS,  ETC.  305 

discomfort.  On  the  other  hand,  if  the  stimulus  is  deficient,  the  will  must 
aid  the  expulsors,  in  order  to  overcome  that  resistance  which  is  due  to  the 
reflex  contraction  of  the  sphincters;  of  this  also  we  may  convince  ourselves, 
when  a  sense  of  propriety,  or  a  prospective  regard  to  convenience,  occasions 
us  to  evacuate  the  contents  of  the  rectum  or  bladder  without  a  natural  call  to 
do  so. 

393.  Movements  of  the  Genital  Organs. — The  muscular  contractions  in- 
volved in  the  Emissio  Seminis   are  clearly  of  a  reflex  nature  ;  being  inde- 
pendent of  the  will  and  not  capable  of  restraint  by  it,  when  once  fully  excited; 
and  being  producible  in  no  other  way,  than  (like  those  concerned  in  Degluti- 
tion) by  a  particular  local  irritation.     That  this  irritation  need  not  amount  to 
a  sensation,  is  proved  by  cases  already  referred  to  (§  372) ;  and  it  has  been 
also  shown  by  experiment,  that  section  of  the  Spinal  Cord  in   the   lumbar 
region  does  not  prevent  the  act  from  being  performed,  the  lower  division  only 
being  concerned  in  the  reflexion  of  the  impression.     It  further  appears,  from 
the  experiments  of  Valentin,  that  the  Spinal  Cord  may  operate  on  the  Genital 
organs  through  the  Sympathetic  system.     Contractions  were  excited  in  the 
vas  deferens  vesiculae  seminales,  especially  of  the  Guinea  Pig  at  the  time  of 
heat,  by  irritation  of  the  inferior  lumbar  and  highest  sacral  portions  of  the 
Sympathetic;  and   the  Fallopian  tubes,  as  well  as  the  Uterus  itself,  may  be 
excited  to  contraction,  by  irritation  of  the  same  nerves  as  those  which  excite 
the  rectum, — namely,  the  lower  lumbar  and  first  sacral  nerves  of  the  Spine. 
This  last  fact  is  important,  in  regard  to  the  rationale  of  the  operation  of  certain 
medicines,  such  as  aloes,  which   are   known  to  have  an  influence  on   both 
parts. — In  regard  to  the  act  of  Parturition,  there  would  seem  reason  to  believe, 
from  the  evidence  of  cases  of  paraplegia,  that,  of-the  muscles  whose  operation 
is  associated  in  it,  the  diaphragm,  abdominal  muscles,  &c.,  are   called   into 
action  (as  in  defecation)  through  the  Spinal  Cord ;  but  that  the  contractions 
of  the  Uterus  itself  are  but  little  dependent  on  its  connection  with  the  nervous 
centres.     Of  the  reason  why  the  muscles,  which  were  up  to  that  time  inert, 
should  then  combine  in  this  extraordinary  mariner,  and  with  such  remarkable 
energy,  Physiology  can  afford  no   certain  information.     There  can  be  little 
doubt,  however,  that  the  stimulus  usually  originates  in  the  uterus,  or  in  some 
of  the  neighbouring  organs  which  are  incommoded  by  the  pressure ;  but  it 
may  also  result  from  some   condition  of  the  general  system,  in  which  the 
uterus  itself  is  but  little  concerned.     It  is  an  interesting  fact,  which  has  been 
more  than  once  observed,  that  the  foetus  may  be  expelled  from  the  dying  body 
of  the  mother,  even  after  the  respiratory  movements  have  ceased.     This  would 
appear  due  to  the  contraction  of  the  Uterine  fibres  alone,  which,  like  those  of 
the  heart  and  alimentary  canal,  retain  their  irritability  longer  than  those  ot 
the  muscles  supplied  by  the  cerebro-spinal  nerves;   and, the  power  of  these 
would   be  unopposed  by  the  resistance  which  they  ordinarily  have  to  en- 
counter ;  since  the  tension  of  all  the  muscles  surrounding  the  outlet  would  be 
destroyed,  by  the  cessation  of  the  activity  of  the  Spinal  system  of  nerves 
(§398). 

394.  Protecting  Agency  of  the  Spinal  Cord. — From  the  foregoing  details 
it  appears,  that  one  of  the  chief  functions  of  the  Spinal  Cord  is  to  control  the 
orifices  of  the  various  open  cavities  of  the  body;  and  this  function  evidently 
has  safety,  as  well  as  convenience,  in  view.     It  has  been  manifestly  designed 
by  the  All-wise  Creator,  that  the  Glottis  should  close  against  agents  injurious 
to  the  organs  within;  and  that  the  effort  to  vomit  should •  be  excited  by  the 
attempt  to  swallow  substances  so  nauseous  as  to  induce  loathing. — There  is 
another  protective  influence  exerted  by  it,  of  a  still  more  remarkable  nature. 
It  has  been  ascertained  by  Dr.  M.  Hall  that,  if  the  functions  of  the  Brain  be 
suspended  or  destroyed,  without  injury  to  the  Spinal  system  of  nerves,  the 

26* 


306  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

Orbicularis  muscle  will  contract,  so  as  to  occasion  the  closure  of  the  eyelids, 
upon  the  tarsal  margin  being  touched  with  a  feather.  •  This  fact  is  interesting 
in  several  points  of  view.  In  the  first  place,  it  is  a  characteristic  example  of 
pure  reflex  action  ;  occurring  under  circumstances  in  which  volition  cannot  be 
imagined  to  guide  it,  and  in  which  there  is  no  valid  reason  to  believe  that  sen- 
sation directs  it.  Further,  it  explains  the  almost  irresistible  nature  of  the  tend- 
ency to  winking,  which  is  performed  at  short  intervals  by  the  contraction  of  the 
Orbicularis  muscle;  this  is  evidently  a  Spinal  action,  capable  of  being  in  some 
degree  restrained  (like  that  of  respiration)  by  the  will,  but  only  until  such  time 
as  the  stimulus  (resulting  perhaps  from  the  -collection  of  minute  particles  of 
dust  upon  the  eyes,  or  from  the  dryness  of  its  surface  in  consequence  of 
evaporation),  becomes  too  strong  to  be  any  longer  resisted.  Again,  we  have 
in  sleep  or  in  apoplexy  an  example  of  this  purely  spinal  action,  unbalanced 
by  the  influence  of  the  will,  which,  in  the  waking  state,  antagonizes  it  by 
calling -the  levator  palpebra  into  action.  As  soon  as  the  will  ceases  to  act,  the 
lids  droop,  and  close  over  the  eye  in  order  to  protect  it;  and  if  those  of  a 
sleeping  person  be  separated  by  the  hand,  they  will  be  found  presently  to 
return.  Here,  as  in  studying  the  respiratory  and  other  movements,  we  are 
led  to  perceive,  that  it  is  the  Brain  alone,  which  is  torpid  during  sleep,  and 
whose  functions  are  affected  by  this  torpidity.  As  Dr.  M.  Hall  very  justly 
remarks,  the  Spinal  system  never  sleeps;  it  is  constantly  in  activity;  and  it  is 
thus  that,  in  all  periods  and  phases  of  Life,  the  movements  which  are  essential 
to  its  continued  maintenance  are  kept  up  without  sensible  effort. 

395.  The  closure  of  the  Pupil  against  a  strong  light,  is  another  movement 
of  the  same  protective  tendency.  The  channel,  through  which  that  just 
named  is  performed,  is  completed  by  the  first  branch  of  the  Fifth  and  the 
Portio  Dura  of  the  seventh.  The  contraction  of  the  pupil  is  immediately 
caused  by  the  Third  pair,  or  Motor  Oculi;  as  is  easily  shown  by  irritating  the 
trunk  of  that  nerve  and  observing  the  result.  But  it  is  not  easy  to  speak  with 
certainty  as  to  the  afferent  nerve,  by  which  the  motor  influence  is  excited. 
Although  the  contraction  of  the  pupil  is  usually  in  close  accordance  with  the 
sensation  occasioned  by  the  impression  of  light  upon  the  retina,  yet  there  is 
no  want  of  evidence  to  prove  that  the  sensation  of  light  is  not  always  neces- 
sary ;  for,  even  when  the  sight  of  both  eyes  has  been  entirely  destroyed  by 
amaurosis,  the  regular  actions  have  been  witnessed  in  the  pupil,  in  accordance 
with  varying  degrees  of  light  impinging  on  the  retina.  This  fact  may  be 
explained  in  two  ways.  It  may  either  be  imagined  that  the  requisite  stimulus 
is  not  that  of  light  conveyed  through  the  Optic  nerve ;  but  that  of  heat  con- 
veyed through  the  ophthalmic  branch  of  the  Fifth  pair.  Or  it  may  be  still 
supposed,  that  the  motion  results  from  an  impression  upon  the  retina,  which 
impression,  being  conducted  to  the  Sensorium,  ordinarily  produces  a  sensation; 
whilst  in  these  curious  cases,  no  sensation  is  produced,  on  account  of  a  dis- 
ordered state  of  the  part  of  the  ganglionic  centre  in  which  the  Optic  nerve 
terminates;  though  some  filaments  of  that  nerve,  being  connected  with  the 
Third  pair  by  means  of  a  distinct  tract  of  vesicular  matter,  can  produce  a 
reflex  action  through  it,  although  no  sensation  intervene.  In  either  view,  the 
rarity  of  the  occurrence  is  at  once  accounted  for ;  since  in  most  cases  of 
amaurosis,  the  disease  lies  in  the  trunk  of  the  nerve,  and  thereby  checks  both 
its  spinal  and  its  encephalic  actions. 

396.  The  Physiologist  has  not  at  present  any  knowledge  of  any  similar 
protective  movements,  in  the  Human  being,  designed  to  keep  the  organ  of  Hear- 
ing from  injury ;  but  there  can  be  little  doubt  that  those  which  we  are  constantly 
witnessing  in  other  animals,  possessing  large  external  ears,  are  reflex  actions 
excited  by  the  irritation  applied  to  them.  In  regard  to  the  Nose,  we  find  a 
remarkably  complex  action — that  of  Sneezing — adapted  to  drive  off"  any  cause 


REFLEX  ACTIONS. MOVEMENTS  OF  LOCOMOTION.  307 

of  irritation  (§  381).  It  will  hereafter  be  shown  that  the  stimulus  is  conveyed, 
in  this  case,  not  through  the  Olfactory  nerve,  but  through  the  Fifth  pair;  so 
that  it  is  not  dependent  upon  the  excitement  of  the  sensation  of  Smell.  The 
act  of  Coughing,  also,  may  be  regarded  as  of  a  protective  character ;  being 
destined  to  remove  sources  of  irritation  from  the  air-passages.  The  automatic 
movements,  performed  by  the  limbs  of  Frogs  and  other  animals,  when  their 
connection  with  the  brain  has  been  cut  off  (§§  306,  370)  appear  destined  to 
remove  these  parts  from  sources  of  irritation  or  injury;  and  they  may  thus  be 
rightly  placed  under  the  same  category. 

397.  Movements  of  Locomotion. — Lastly,  we  have  to  inquire  how  far  the 
Reflex  function  of  the  Spinal  Qord  is  concerned  in  the  locomotive -actions  of 

"the  lower  extremities  in  Man.  It  will  be  remembered  that,  in  the  Dytiscus 
whose  head  had  been  removed  (§  328),  the  stimulus  of  the  contact  of  water 
immediately  excited  regular  and  continued  locomotive  actions  which  lasted 
for  some  time.  So  in  the  cases  already  quoted  (§§  366- — 368),  when  the  con- 
trol of  the  will  over  the  lower  extremities  was  lost,  powerful  muscular  actions 
were  excited  in  them,  through  the  Spinal  Cord  alone.  In  the  healthy  con- 
dition of  the  Human  system,  when  the  Will  is  controlling  all  the  movements, 
which  are  not  immediately  concerned  in  the  maintenance  and  regulation  of 
the  organic  functions,  no  such  actions  can  be  excited  :  but  in  proportion  as  its 
control  is  lost,  does  the  independent  power  of  the  Spinal  Cord  manifest  itself. 
The  more  such  actions  are  of  a  simple  rhythmical  character,  similar  to  those 
of  Respiration,  the  more  does  it  seem  that  they  may  with  probability  be  re- 
ferred to  the  Spinal  system ;  and  if  we  attribute  to  this  (as  we  can  scarcely 
help  doing)  the  rapid  vibration  of  the  wings  of  Insects,  there  seems  no  reason 
why  we  should  riot  extend  the  same  view  to  the  wings  of  Birds.  Such  an 
explanation  of  their  movements  will  account  for  their  occasional  continuance, 
without  apparent  fatigue,  during  a  period  through  which  no  known  voluntary 
effort  can  endure;  for  it  is  one  of  the  attributes  of  the  Spinal  system  of 
nerves,  well  pointed  out  by  Dr.  M.  Hall,  that  the  exercise  of  the  muscles 
excited  by  it  does  not  occasion  fatigue,  the  sense  of  which  is  Cerebral  only. 
It  would  seem  to  the  Author  more  probable,  however,  that  those  movements 
which  guide  the  body,  and  which  must  themselves  be  directed  by  Sensation, 
are  to  be  referred  to  a  class  intermediate  between  the  Voluntary  and  the  Re- 
flex, which  may  be  properly  termed  Consensual.  Numerous  actions,  in  Man, 
which  were  at  first  Voluntary,  appear,  at  last  to  be  performed  as  instinctively 
or  intuitively,  as  they  are  in  the  lower  animals  from  the  commencement  of 
their  existence.  (See  the  next  Section.) 

398.  Influence  on  Muscular  Tension. — The  various  muscles  of  the  body, 
even  when  there  is  the  most  complete  absence  of  effort,  maintain,  in  the 
healthy  state  of  the  system,  a  certain  degree  of  firmness,  by  their  antagonism 
with  each  other ;  and  if  any  set  of  muscles  be  completely  paralyzed,  the  op- 
posing muscles  will  draw  the  part  on  which  they  act,  out  of  its  position  of 
repose ;  as  is  well  seen  in  the  distortion  of  the  face,  which  is  characteristic 
of  paralysis  of  the  facial  nerve  on  one  side.     This  condition  has  been  desig- 
nated as  the  tone  of  the  Muscles ;  but  this  term  renders  it  liable  to  be  con- 
founded with  their  tonic  contraction,  which  is  also  concerned  in  maintaining 
their  firmness,  but  which  operates  in  a  very  different  manner.     The  latter  is 
dependent  upon  the  simple  contractility  of  the  muscle ;  and  is  exhibited  alike 
by  the  striated  and  the  non-striated  forms  of  muscular  fibre,  but  more  espe- 
cially by  the  latter  (§  593).     On  the  other  hand,  the  condition  now  alluded  to, 
which  may  perhaps  be  appropriately  termed  their  tension,  is  the  result  of  a 
moderate  though  continued  excitement  of  that  contractility,  through  the  nerv- 
ous centres.     It  has  been  proved  by  Dr.  M.  Hall,  that  the  Muscular  Tension 
is  not  dependent  upon  the  influence  of  the  Brain  ;  but  upon  that  of  the  Spinal 


308  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

Cord  ;  as  the  following  experiments  demonstrate. — "  Two  Rabbits  were  taken ; 
from  one  the  head  was  removed ;  from  the  other  also  the  head  was  removed, 
and  the  spinal  marrow  was  cautiously  destroyed  with  a  sharp  instrument:  the 
limbs  of  the  former  retained  a  certain  degree  of  firmness  and  elasticity; 
those  of  the  second  were  perfectly  lax."  Again  : — "  The  limbs  and  tail  of  a 
decapitated  Turtle  possessed  a  certain  degree  of  firmness  or  tone,  recoiled  on 
being  drawn  from  their  position,  and  moved  with  energy  on  the  application  of 
a  stimulus.  On  withdrawing  the  spinal  marrow  gently  out  of  its  canal,  all 
these  phenomena  ceased.  The  limbs  were  no  longer  obedient  to  stimuli,  and 
became  perfectly  flaccid,  having  lost  all  their  resilience.  The  sphincter  lost 
its  circular  form  and  contracted  state,  becoming  lax,  flaccid,  and  shapeless. - 
The  tail  was  flaccid,  and  unmoved  on  the  application  of  stimuli."  It  is  further* 
remarked  by  Messrs.  Todd  and  Bowman,  that  '  a  decapitated  frog  will  con- 
tinue in  the  sitting  posture  through  the  influence  of  the  spinal  cord  ;  but  im- 
mediately this  organ  is  removed,  the  limbs  fall  apart." 

399.  This  operation  of  the  Spinal  Cord  is  doubtless  but  a  peculiar  mani- 
festation of  its  ordinary  reflex  function.     We  shall  hereafter  see  (Section  5) 
how  much  the  influence  of  the  will  in  producing  the  active  contraction  of  a 
muscle,  is  connected  with  sensations  received  from  it;  and  it  seems  highly 
probable,  that  the   impression  of  the  state  of  the  muscle,  conveyed  by  the 
afferent  fibres  proceeding  from  it  to  the  spinal  cord,  is  sufficient  to  excite  this 
state   of  moderate  tension   through  the  motor  nerves,  arising  from  the  latter. 
Such  a  view  derives  probability  from  the  fact,  which  must  have  fallen  under 
the  observation  of  almost  every  one,  that  most  reflex  actions  become  increased 
in  energy  if  resistance  is  made  to  them.     Of  this  we  have  familiar  examples 
in  the  action  of  the  expulsor  muscles,  which  operate  in  defecation,  urination, 
and  parturition,  if,  when  they  are  strongly  excited,  their  efforts  be  opposed 
by  the  will  acting  on  the  sphincters,  or  by  mechanical  means.     Many  forms 
of  convulsive  movement  exhibit  the  same  tendency  ;  their  violence  being  pro- 
portional to  the  mechanical  force  used  to  restrain  them.*     Here  it  is  evident 
that  the  impression  of  resistance,  conveyed  to  the  Spinal  Cord,  is  the  source 
of  the  increased  energy  of  its  motor  influence  ; — from  which  we  may  fairly 
infer  that  the  moderate  resistance,  occasioned  by  the  natural  antagonism  of  the 
muscles,  is  the  source  of  their  continued  and  moderate  tension,  whilst  they 
are  under  the  influence  of  the  Spinal  Cord.     This  constant  though  gentle 
action  serves  to  keep  up  the  nutrition  ef  the  muscles,  which  are  paralyzed  to 
the  will ;  and  this  is  still  more  completely  maintained,  if  the  portion  of  the 
nervous   centres,  with  which   they  remain  connected,  is  so  unduly  irritable, 
that  the  muscles  are  called  into  contraction  upon  the  slightest  excitation,  and 
are  thus  continually  exhibiting  twitchings,  starlings,  or  more  powerful  convuls- 
ive movements.     It  is  upon  the  state  of  nutrition  of  the  muscles,  that  their 
contractility  depends,  as   will  be   shown  hereafter  (§  588) ;  and  hence   the 
Spinal  Cord  has   an  indirect  influence  upon  this  peculiar  property,  which  is 
more  likely  to  be  retained,  when  the  muscle  is  still  subject  to  the  influence  of 
the  Spinal  Cord,  though  cut  off  from  that  of  the  Brain,  than  when  it  is  com- 
pletely paralyzed  by  the  entire  cessation  of  the  influence   of  the   nervous 
centres. 

400.  Pathological  Phenomena. — It  would  not  be  right  to  conclude  this 
account  of  the  principal  functions  of  the  Spinal  Cord,  without  adverting  to 
some  of  the  leading  Pathological  applications  of  the  physiological  doctrines 

*  Hence  the  absurdity  of  the  common  practice  of  endeavouring  to  prevent  the  move- 
ments of  the  limbs  and  tody,  in  convulsive  paroxysms,  by  mechanical  constraint.  Nothing 
should  be  attempted  but  what  is  requisite  to  prevent  the  sufferer  from  doing  himself  an  in- 
jury. 


REFLEX  ACTIONS. PATHOLOGICAL  PHENOMENA.  309 

which  have  been  developed  in  it;  although  they  will  hereafter  be  passed 
under  a  more  general  review  (Section  8).  A  large  part  of  these  were  first 
pointed  out  by  Dr.  M.  Hall;*  and  they  are  receiving  continual  and  important 
extensions  from  his  own  labours  and  those  of  other  practical  inquirers.  It 
may  be  remarked,  in  the  first  place,  that  the  power  of  the  whole  Spinal  sys- 
tem is  capable  of  being  morbidly  diminished  or  augmented.  It  may  even  be 
for  a  time  almost  completely  suspended,  as  in  Syncope ;  which  state  may  be 
induced  by  sudden  and  violent  impressions,  either  of  a  mental  or  physical 
nature,  that  operate  upon  the  whole  nervous  system  at  once, — commencing, 
however,  in  the  brain.  It  is  to  be  remarked  that,  in  recovering  from  these,  it 
is  the  Spinal  system  of  which  the  activity  is  first  renewed, — the  respiratory 
movements  recommencing,  and  the  power  of  swallowing  being  restored, 
before  any  voluntary  actions  can  be  performed.  A  corresponding  state  may 
be  induced  in  particular  portions  of  the  system  by  concussion ;  as  is  seen  in 
severe  injuries  of  the  Spinal  Cord,  which  are  almost  invariably  followed  for 
a  time  by  the  suspension  of  its  functions.  Again,  the  power  of  the  whole 
Spinal  Cord  may  be  diminished  by  various  causes,  such  as  enfeebled  circula- 
tion, pressure,  &c. ;  and  then  we  have  torpidity  of  the  whole  muscular  sys- 
tem. If  oppression  exists  in  the  Brain,  the  functions  of  the  Medulla  oblon- 
gata  will  be  especially  affected;  and  if  it  be  prolonged  and  sufficiently  severe, 
Asphyxia  will  result  from  the  interruption  of  the  respiratory  movements  which 
it  occasions. 

401.  On  the  other  hand,  the  excitability  of  the  whole  Cord,  or  of  particu- 
lar parts  of  it,  may  be  .morbidly  increased.  This  is  especially  seen  in  ordi- 
nary Tetanus  and  the  artificial  Tetanus  induced  by  Strychnine;  in  which  the 
slightest  external  stimulus  is  sufficient  to  induce  reflex  actions  in  their  most 
terrific  forms.  It  is  interesting  to  remark,  that  in  this  formidable  disease  the 
functions  of  the  muscles  controlling  the  various  orifices  are  those  most  affected ; 
and  it  is  by  the  spasms  affecting  the  organs  of  respiration  or  deglutition,  that 
life  is  commonly  terminated. — Various  remedial  agents  will  probably  be  found 
to  operate,  by  occasioning  increased  excitability  in  some  particular  segments 
of  the  Cord;  so  that  the  usual  stimuli  applied  to  the  parts  connected  with 
these,  will  occasion  increased  muscular  tension.  This  seems  to  be  the  case, 
for  example,  in  regard  to  the  influence  of  aloes  on  the  rectum  and  uterus, 
cantharides  on  the  neck  of  the  bladder  and  adjoining  parts,  and  secale  cornu- 
tum  on  the  uterus.  The  mode  of  influence  of  cantharides  is  illustrated  by  a 
curious  case,  related  by  Dr.  M.  Hall,  of  a  young  lady  who  lost  the  power  of 
retention  of  urine,  in  consequence  of  a  fatty  tumour  in  the  spinal  canal,  which 
gradually  severed  the  Spinal  Cord,  and  induced  paraplegia.  The  power  of 
retaining  the  urine  was  always  restored  for  a  time  by  a  dose  of  tincture 
of  cantharides,  which  augmented  the  excitability  of  the  segment  of  the  cord, 
with  which  the  sphincter  vesica3  is  connected. — The  researches  of  Valentin, 
when  grafted  (as  it  were)  on  the  doctrines  of  Dr.  M.  Hall,  afford  the  key  to 
the  explanation  of  the  numberless  sympathetic  influences  of  the  organs  of 
nutrition,  &c.,  upon  one  another;  by  showing  that  they  are  all  connected  with 
the  Spinal  Cord  ;  and  that  the  muscular  structure,  with  which  they  are  all 
provided,  may  be  excited  to  contraction  through  it.  And,  lastly,  the  more 
recent  observations  of  Dr.  M.  Hall,  in  regard  to  the  peculiar  excitor  power 
that  belongs  to  the  nervous  fibres  distributed  on  various  serous  and  fibrous 
membranes,  will  probably  lead,  when  they  have  been  fully  carried  out,  to  the 
explanation  of  the  various  convulsive  actions,  that  result  from  pressure  or 
irritation  affecting  these  parts. 

*  See  especially  his  Treatise  on  the  Diseases  and  Derangements  of  the  Nervous  System. 


310  FUNCTIONS  OF  THE  NEllVOUS  SYSTEM. 

a.  It  has  been  pointed  out  by  Messrs.  Todd  and  Bowman  (Physiological  Anatomy,  Vol.  I. 
p.  315),  that  the  Spinal  Cord  of  the  male  frog,  at  the  season  of  copulation,  naturally  pos- 
sesses a  state  of  most  extraordinary  excitability.  The  thumb  of  each  anterior  extremity  at 
this  season,  becomes  considerably  enlarged;  as  is  well  known  to  Naturalists.  "  This  enlarge- 
ment is  caused  principally  by  a  considerable  development  of  the  papillary  structure  of  the 
skin  which  covers  it;  so  that  large  papillas  are  formed  all  over  it.  A  male  frog,  at  this 
season,  has  an  irresistible  propensity  to  cling  to  any  object,  by  seizing  it  between  his  anterior 
extremities.  It  is  in  this  way  that  he  seizes  upon,  and  clings  to  the  female ;  fixing  his 
thumbs  to  each  side  of  her  abdomen,  and  remaining  there  for  weeks,  until  the  ova  have  been 
completely  expelled.  An  effort  of  the  Will  alone  could  not  keep  up  the  grasp  uninterrupt- 
edly for  so  long  a  time,  yet  so  firm  is  the  hold,  that  it  can  with  difficulty  be  relaxed.  What- 
ever is  brought  in  the  way  of  the  thumbs,  will  be  caught  by  the  forcible  contraction  of  the 
anterior  limbs ;  and  hence  we  often  find  frogs  clinging  blindly  to  a  piece  of  wood,  or  a  dead 
fish,  or  some  other  substance  which  they  may  chance  to  meet  with.  If  the  finger  be  placed 
between  the,  anterior  extremities,  they  will  grasp  it  firmly ;  nor  will  they  relax  their  grasp 
until  they  are  separated  by  force.  If  the  animal  be  decapitated,  whilst  the  finger  is  within 
the  grasp  of  its  anterior  extremities,  they  still  continue  to  hold  on  firmly.  The  posterior  half 
of  the  body  may  be  cut  away,  and  yet  the  anterior  extremities  will  still  cling  to  the  finger; 
but  immediately  that  the  segment  of  the  cord,  from  which  the  anterior  extremities  derive 
their  nerves,  has  been  removed,  all  their  motion  ceases.  This  curious  instinct  only  exists 
during  the  period  of  sexual  excitement;  for  at  other  periods  the  excitability  of  the  anterior 
extremities  is  considerably  less  than  that  of  the  posterior." 

402.  Nerves  of  the  Spinal  System. — The  nerves  which  minister  to  the 
functions  of  the  Spinal   Cord,  conveying  to  it  the   impressions  made  on  the 
periphery,  and  transmitting  its  motor  influence  to  the  muscles, — are  not  those 
alone  which  are  ordinarily  designated  as  Spinal  nerves;   for  several  of  those, 
which  pass  forth  through  the  base  of  the  cranium,  and  which  are  commonly 
described  as   Cephalic  nerves,  belong  to  the   same   category.     The  general 
characters  of  the   Spinal  nerves,  their  mode  of  connection  with   the  Spinal 
Cord  by  two  sets  of  roots,  and  the  presence   of  ganglion  upon  the  posterior 
root,  have  already  been  adverted  to  (§  344).     The  anterior  roots  are  usually 
the  smaller ;  and  this  is  particularly  the  case  with  those  of  the  cervical  nerves, 
in  which  the  posterior  roots  are  of  remarkable  comparative  size.    In  the  First 
Cervical  or  Sub-occipital  pair,  the  anterior  roots  are  sometimes  wanting ;  but 
there  is  then  a  derivation  of  fibres  from  the  Spinal  Accessory,  or  from  the 
Hypoglossal,  or  from  both.     The  two  roots  of  the  ordinary  Spinal  nerves 
unite  immediately  beyond  the  ganglion,  which  is  situated  on  the  posterior  one; 
and  the  trunk  thus  formed  separates  immediately  into  two  divisions, — the  an- 
terior and  posterior, — each  of  which  Contains  both  afferent  and  motor  fibres. 
These  divisions,  of  which  the  anterior  is  by  far  the  larger,  proceed  to  the  ante- 
rior and  posterior  parts  of  the  body  respectively ;  and  are  chiefly  distributed  to 
the  skin  and  the  muscles.     The  anterior  branch  is  that  which  communicates 
with  the  sympathetic  nerve. 

403.  The  pair  of  nerves  commonly  designated  as  the  Fifth  of  the  Cephalic 
series,  or  as  the  Trifacial,  is  the  one  which  more  nearly  resembles  the  ordi- 
nary Spinal  nerves  (as  was  long  since  pointed  out  by  Sir  C.  Bell),  than  does 
any  other  of  those  originating  within  the  cranium.     It  possesses  two  distinct 
sets  of  roots,  of  which  one  is  much  larger  than  the  other  ;  on  the  larger  root, 
as  on  the  posterior  and  larger  root  of  the  Spinal  nerves,  is  a  distinct  ganglion; 
and  the  fibres  arising  from  the  smaller  root  do  not  blend  with  the  others,  until 
after  the  latter  have  passed  through  this  ganglion.     The  trunk  of  the  nerve 
separates,  as  is  well  known,  into  three  divisions, — the  Ophthalmic,  the  Supe- 
rior Maxillary,  and  the  Inferior  Maxillary ;  and  it  can  be  easily  shown,  by 
careful  dissection,  that  the  fibres  of  the  smaller  root  pass  into  the  last  of  these 
divisions  alone.     When  the  distribution  of  this  nerve  is  carefully  examined, 
it  is  found  that  the  first  and  second  divisions  of  it  proceed  almost  entirely  to 
the  skin  and  mucous  surfaces ;  a  very  small  proportion,  only,  of  their  fibres 
being  lost  in  the  muscles :  whilst  of  the  branches  of  the  third  division,  a  large 
number  are  distinctly  muscular.     Hence  analogy,  and  the  facts  supplied  by 


SPINAL  NERVES. FIFTH  PAIR,  OR  TRIFACIAL. 


311 


anatomical  research,  would  lead  to  the  conclusion,  that  the  first  two  divisions 
are  nerves  of  sensation  only,  and  that  the  third  division  combines  sensory  and 
motor  endowments.  Such  an  inference  is  fully  borne  out  by  experiment. 
When  the  whole  trunk  is  divided  within  the  cranium  by  the  penetration  of  a 
sharp  instrument  (which  Magendie,  by  frequent  practice,  has  been  able  to  ac- 
complish), evident  signs  of  acute  pain  are  given.  After  the  incision  has  been 
made  through  the  skin,  the  animal  remains  quiet  until  the  nerve  is  touched ; 
and  when  it  is  pressed  or  divided,  doleful  cries  are  uttered,  which  continue 
for  some  time,  showing  the  painful  effect  of  the  irritated  state  of  the  cut  ex- 
tremity. The  common  sensibility  of  all  the  parts  supplied  by  this  nerve  is 
entirely  destroyed  on  the  affected  side.  The  jaw  does  not  hang  loosely,  be- 
cause it  is  partly  kept  up  by  the  muscles  of  the  other  side ;  but  it  falls  in  a 
slight  degree ;  and  its  movements  are  seen,  when  carefully  observed,  to  be 
somewhat  oblique.  If  the  trunk  be  divided  on  each  side,  the  whole  head  is 
deprived  of  sensibility ;  and  the  animal  carries  it  in  a  curious  vacillating  man- 
ner, as  if  it  were  a  foreign  body. 

Fig.  150. 


A  diagram  showing  the  Fifth  pair  of  nerves  with  its  branches.  1.  The  origin  of  the  nerve  by  two  roots, 
2.  The  nerve  escaping  from  the  crus  cerebelli.  3.  The  Gasserian  ganglion.  4.  Its  ophthalmic  division. 
5.  The  frontal  nerve,  giving  off  the  supra-trochlear  branch,  and  escaping  on  the  forehead  through  the 
supra-orbital  foramen.  6.  The  lachrymal  nerve.  7.  The  nasal  nerve,  passing  at  8  through  the  anterior 
ethmoidal  foramen,  and  giving  off  the  infra- trochlear  branch.  9.  The  communication  of  the  nasal  nerve 
with  the  ciliary  ganglion.  10.  A  small  portion  of  the  third  nerve  with  which  the  ganglion  is  seen  com- 
municating; the  ganglion  gives  off  the  ciliary  branches  from  its  anterior  aspect.  11.  The  superior  maxil- 
lary nerve.  12.  Its  orbital  branch.  13.  The  two  branches  communicating  with  Meckel's  ganglion ;  the 
three  branches  given  off  from  the  lower  part  of  the  ganglion  are  the  posterior  palatine  nerves.  14, 14. 
The  superior  dental  nerves,  posterior,  middle,  and  anterior.  15.  The  infra-orbital  branches  distributed 
upon  the  cheek.  16.  The  inferior  maxillary  nerve.  17.  Its  anterior  or  muscular  trunk.  18.  The  pos- 
terior trunk ;  the  two  divisions  are  separated  by  an  arrow.  19.  The  gustatory  nerve.  20.  The  corda 
tympani  joining  it  at  an  acute  angle.  21.  The  submaxillary  ganglion.  22.  The  inferior  dental  nerve. 
23.  Its  mylo-hyoidean  branch.  24.  The  auricular  nerve,  dividing  behind  the  articulation  of  the  lower 
jaw,  to  reunite  and  form  a  single  trunk.  25.  Its  branch  of  communication  with  the  facial  nerve.  26.  Its 
temporal  branch. 

404.  If  the  anterior  or  Ophthalmic  branch  only  be  divided,  all  the  parts 
supplied  by  it  are  found  to  have  lost  their  sensibility,  but  their  motions  are 
unimpaired ;  and  all  experiments  and  pathological  observations  concur  in  at- 


312 


FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 


tributing  to  it  sensory  endowments  only.  The  only  apparent  exception  is  in 
the  case  of  the  Naso-Ciliary  branch;  since  there  is  good  reason  to  believe  that 
the  long  root  of  the  ciliary  ganglion,  and  the  long  ciliary  nerves,  possess  motor 


[Fig.  151. 


A  view  of  the  distribution  of  the  Trifacial  or  Fifth 
pair;  1,  orbit;  2,  antrum  highmorianum ;  3,  tongue; 
4,  lower  jaw-bone;  5,  root  of  the  fifth  pair,  forming 
the  ganglion  of  Gasser ;  6,  first  branch  of  the  fifth  pair, 
or  ophthalmic  ;  7,  second  branch  of  the  fifth  pair,  or 
superior  maxillary  ;  8,  third  branch  of  the  fifth  pair,  or 
inferior  maxillary ;  9,  frontal  branch,  dividing  into  ex- 
ternal and  internal  frontal  nerves;  10,  lachrymal 
branch  of  the  fifth  pair ;  11,  nasal  branch ;  just  under 
the  figure  is  the  long  root  of  the  lenticular  or  ciliary 
ganglion  and  a  few  of  the  ciliary  nerves;  12,  internal 
nasal  nerve,  disappearing  through  the  anterior  eth- 
moidal  foramen;  13,  external  nasal  nerve;  14,  external 
and  internal  frontal  nerve ;  15,  infra-orbitary  nerve  ; 
16,  posterior  dental  branches ;  17,  middle  dental 
branch;  18,  anterior  dental  nerve:  19,  terminating 
branches  of  the  infra-orbital  nerve,*called  the  labial 
and  palpebral  nerves;  20,  subcutaneous  malae,  oror- 
bitar  branch  ;  21,  pterygoid,  or  recurrent  nerve,  from 
Meckel's  ganglion;  22,  five  anterior  branches  of  the 
third  branch  of  the  fifth  pair;  23,  lingual  branch  of  the 
fifth,  joined  by  the  chorda  tympani ;  24,  inferior  dental 
nerve ;  25,  its  mental  branches ;  26,  superficial  tempo- 
ral nerve;  27,  auricular  branches;  28,  mylo-hyoid 
branch.] 


powers  ;  but  these  appear  to  be  derived  from  the  Sympathetic  nerve.  When 
the  whole  nerve,  or  its  anterior  branch,  is  divided  in  the  rabbit,  the  pupil  is 
exceedingly  contracted,  and  remains  immovable ;  but  in  dogs  and  pigeons  it 
is  dilated.  The  pupil  of  the  other  eye  is  scarcely  affected ;  or,  if  its  dimen- 
sions be  changed,  it  soon  returns  to  its  natural  state.  The  eyeball  speedily 
becomes  inflamed,  however;  and  the  inflammation  usually  runs  on  to  suppu- 
ration and  complete  disorganization.  The  commencement  of  these  changes 
may  be  commonly  noticed  within  twenty-four  hours  after  the  operation  ;  and 
they  appear  to  be  due  to  the  want  of  the  protective  secretion,  which  (as  will 
be  explained  when  the  direct  influence  of  the  nervous  system  upon  the  organic 
functions  is  considered),  is  necessary  to  keep  the  mucous  surface  of  the  eye 
in  its  healthy  condition,  and  which  is  not  formed  when  the  sensibility  of  that 
surface  is  destroyed.— The  Superior  Maxillary  branch,  considered  in  itself, 
is  equally  destitute  of  motor  endowments  with  the  ophthalmic ;  but  its  con- 
nections with  other  nerves,  through  the  spheno-palatine  ganglion  and  its  anas- 
tomosing twigs,  may  introduce  a  few  motor  fibres  into  it. — The  Inferior 
Maxillary  branch  is  the  only  one  which  possesses  motor  as  well  as  sensory 
endowments  from  its  origin;  but  its  different  subdivisions  possess  these  endow- 
ments in  varying  proportions,  some  being  almost  exclusively  motor,  and  others 
as  completely  of  a  sensory  character.  The  latter  is  probably  the  nature  of 
the  Lingual  branch ;  and  there  seems  good  reason  to  believe,  as  will  hereafter 
be  shown,  that  this  ministers  not  only  to  the  tactile  sensibility  of  the  tongue, 
but  to  the  sense  of  Taste.  The  muscles  put  in  action  by  this  division  of  the 
Fifth  pair,  are  solely  those  concerned  in  the  masticatory  movements. 

405.  The  Third,  Fourth,  and  Sixth  pairs,  together  make  up  the  appara- 
tus of  motor  nerves,  by  which  the  muscles  of  the  Orbit  are  called  into  ac- 
tion. The  Third  pair  supplies  the  greater  number  of  the  muscles  ;  the  Fourth 


CRANIAL  NERVES. THIRD  TO  SEVENTH. 


313 


being  confined  to  the  superior  ob-  [Fig.  152. 

lique,  and  the  Sixth  to  the  abdu- 
cens.  Of  these  nerves,  the  Third 
pair  is  the  only  one  which  exhibits 
any  appearance  of  sensibility,  when 
its  trunk  is  irritated  ;  but  this  sen- 
sibility is  not  nearly  so  great  as 
that  of  the  Fifth  pair ;  and  it  may 
be  doubted  whether  it  is  really  pos- 
sessed by  the  Third,  in  virtue  of 
its  direct  connection  with  the  nerv- 
ous centres,  or  whether  it  is  not 
imparted  by  the  anastomosis  of  that 
nerve  with  the  Fifth, — some  fila- 
ments of  which  may  pass  back- 
wards as  well  as  forwards,  so  as  to 
confer  sensibility  on  the  trunk  of 
the  Third,  above  as  well  as  beyond 
their  point  of  entrance. — The  pe- 
culiar mode  in  which  these  motor 
nerves  ordinarily  excite  the  mus- 
cles to  action,  will  be  considered 
in  the  next  Section.  Although 
commonly  ranked  as  cephalic 
nerves,  they  have  no  direct  con- 
nection with  the  Cerebrum ;  their 
real  origin  being  from  the  upper 
part  of  the  Medulla  Oblongata,  and 
those  prolongations  of  it  which  are 
known  as  the  Crura  Cerebri.  The 

roots  of  the  Third  pair  may  be  traced  into  direct  connection  with  the  Cor- 
pora Quadrigemina;  a  fact  of  considerable  physiological  importance,  as  will 
hereafter  appear.  The  chief  actions  of  a  purely  reflex  nature,  to  which  this 
group  of  nerves  ordinarily  ministers,  are  the  government  of  the  diameter  of 
the  pupil,  which  is  accomplished  through  the  Third  pair  ;  and  the  rolling  of 
the  eyeball  beneath  the  upper  lid  during  sleep,  as  well  as  in  the  efforts  of 
sneezing,  coughing,  &c.  But  irregular  movements  of  the  eyeballs,  which 
must  be  referred  to  the  same  group,  are  continually  seen  to  accompany  various 
other  forms  of  convulsive  action. 

406.  The  Portio  Dura  of  the  Seventh  pair,  or  Facial  nerve,  has  been 
supposed,  since  the  first  researches  of  Sir  C.  Bell,  to  be  a  nerve  of  motion 
only ;  but  some  recent  physiologists  have  maintained,  that  it  both  possesses 
sensory  endowments,  and  arises  by  a  double  root.  According  to  Valentin, 
however,  who  experimented  on  the  roots  exposed  within  the  cranium,  it  pos- 
sesses no  sensory  endowments  at  its  origin  ;  since,  when  these  roots  were 
touched,  the  animals  gave  no  signs  of  pain,  though  violent  muscular  move- 
ments were  excited  in  the  face.  Subsequently  to  its  first  entrance  into  the 
canal  by  which  it  emerges,  however,  it  anastomoses  with  other  nerves  ;  and 
thus  sensory  fibres  are  introduced  into  it  from  many  different  sources, — ante- 
riorly, from  the  Fifth  pair,  and  posteriorly,  from  the  Cervical  nerves, — which 
cause  irritation  of  several  of  its  branches  to  produce  pain.  The  number 
and  situation  of  the  anastomoses  vary  much  in  different  animals  ;  so  that  it 
is  impossible  to  make  any  very  comprehensive  statement  in  regard  to  them. 
— Experimental  researches  leave  no  doubt  that  the  Portio  Dura  is  the  general 
motor  nerve  of  the  face  ;  ministering  to  the  influence  of  volition  and  Emo- 
27 


A  view  ofthe  Third,  Fourth  and  Sixth  pairs  of 
Nerves;  1,  ball  ofthe  eye  and  rectus  externus  muscle; 
2,  the  superior  maxilla;  3,  the  third  pair,  or  motores 
oculi,  distributed  to  all  the  muscles  of  the  eye  except 
the  superior  oblique  and  external  rectus;  4,  the  fourth 
pair,  or  pathetici.  going  to  the  superior  oblique  muscle; 
5,  one  of  the  branches  of  the  seventh  pair  ;  6,  the  sixth 
pair,  or  motor  externus,  distributed  to  the  external 
rectus  muscle ;  7,  spheno-palatine  ganglion  and 
branches;  8,  ciliary  nerves  from  the  lenticular  gan- 
glion, the  short  root  of  which  is  seen  to  connect  it  with 
the  third  pair.] 


314  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

Fig.  153. 


The  distribution  of  the  Facialjierve,  and  the  branches  of  the  Cervical  plexus.  1  .The  facial  nerve, 
escaping  from  the  stylo-mastoid  foramen,  and  crossing  the  ramus  of  the  lower  jaw;  the  parotid  gland 
has  been  removed  in  order  to  see  the  nerve  more  distinctly.  2.  The  posterior  auricular  branch;  the 
digastric  and  stylo-mastoid  filaments  are  seen  near  the  origin  of  this  branch.  3.  Temporal  branches, 
communicating  with  (4)  the  branches  of  the  frontal  nerve.  5.  Facial  branches,  communicating  with 
(6)  the  infra-orbital  nerve.  7.  Facial  branches,  communicating  with  (8)  the  mental  nerve.  9.  Cervico- 
facial  branches,  communicating  with  (10)  the  superficialis  colli  nerve,  and  forming  a  plexus  (11)  over 
the  sub-maxillary  gland.  The  distribution  of  the  branches  of  the  facial  in  a  radiated  direction  over  the 
side  of  the  face,  constitutes  the  pes  anserinus.  12.  The  auricularius  magnus  nerve,  one  of  the  ascending 
branches  of  the  cervical  plexus.  13.  The  occipitalis  minor,  ascending  along  the  posterior  border  of  the 
sterno-mastoid  muscle.  14.  The  superficial  and  deep  descending  branches  of  the  cervical  plexus.  15. 
The  spinal  accessory  nerve,  giving  oft'  a  branch  to  the  external  surface  of  the  trapezius  muscle.  16. 
The  occipitalis  major  nerve,  the  posterior  branch  of  the  second  cervical  nerve. 

tion,  and  also  being  the  channel  of  the  Reflex  movements  concerned  in  respi- 
ration and  other  associated  movements  of  the  muscles ;  but  not  being  in  the 
least  concerned  in  the  act  of  mastication. 

a.  The  distinctness  of  the  Spinal  and  Encephalic  actions  of  this  nerve,  is  made  evident 
by  the  not  unfrequent  occurrence  of  paralysis  in  either  of  them,  without  the  other  being 
affected. — Thus  we  may  see  the  mouth  drawn  to  one  side  (in  consequence  of  the  loss  of 
tone,  which  the  muscles  have  experienced),  and  all  the  Reflex  and  Emotional  actions  of 
the  face  performed  only  on  one  side ;  and  yet  Voluntary  power  may  remain  unaffected  ;  so 
that,  in  ordinary  winking,  the  lid  of  the  affected  side  does  not  close ;  though  the  patient  can 
shut  the  eye  by  an  effort  of  the  will. — OH  the  other  hand,  the  tension  of  the  muscles  may 
remain  unimpaired,  and  all  their  Reflex  and  Emotional  actions  may  be  performed  as  usual  • 
and  yet  distortion  may  be  at  once  apparent,  when  Voluntary  actions  are  attempted;  in  con- 
sequence of  paralysis  of  the  Cerebral  portion  of  the  nerve  on  one  side. 

407.  The  functions  of  the  Glosso-Pharyngeal  nerve  have  been  heretofore 
alluded  to  in  part ;  but  there  still  remain  several  questions  to  be  discussed  in 
regard  to  them.  Reasons  have  been  given  for  the  belief  that  it  is  chiefly  an 
afferent  nerve, — scarcely  having  any  direct  power  of  exciting  muscular  con- 
traction, but  conveying  impressions  to  the  Medulla  Oblongata,  which  produce 
reflex  movements  of  the  other  nerves  (§  384).  This  view  of  its  function  has 
been  deduced  by  Dr.  Reid  from  minute  anatomical  investigation,  and  from  a 
large  number  of  experiments.  Some  experimenters  assert,  that  they  have 
succeeded  in  exciting  direct  muscular  actions  through  its  trunk ;  but  these  ac- 
tions seem  to  be  limited  to  the  stylo-pharyngei  and  to  the  palato-glossi  mus- 


FUNCTIONS  OF  THE  PAR  VAGUM.  315 

cles.  Much  controversy  has  taken  place  on  the  question,  whether  this  nerve  is  to 
be  regarded  as  ministering,  partly  or  exclusively,  to  the  sense  of  Taste ;  and 
many  high  authorities  have  ranged  themselves  on  each  side.  The  question 
involves  that  of  the  function  of  the  Lingual  branch  of  the  Fifth  pair;  and  it  is 
partly  to  be  decided  by  the  anatomical  relations  of  the  two  nerves  respectively. 
The  glosso-pharyngeal  is  principally  distributed  on  the  mucous  surface  of  the 
fauces,  and  on  the  back  of  the  tongue.  According  to  Valentin,  it  sends  a 
branch  forwards,  on  either  side,  somewhat  beneath  the  lateral  margin,  which 
supplies  the  edges  and  inferior  surface  of  the  tip  of  the  tongue,  and  inosculates 
with  the  Lingual  branch  of  the  Fifth  pair.  On  the  other  hand,  the  upper  sur- 
face of  the  front  of  the  tongue  is  supplied  by  this  lingual  branch.  The  experi- 
ments of  Dr.  Alcock,  whose  conclusions  are  borne  out  by  Dr.  J.  Reid,  de- 
cidedly support  the  conclusion,  that  the  gustative  sensibility  of  this  part  of 
the  tongue  is  due  to  the  latter  nerve,  being  evidently  impaired  by  division  of 
it.  Moreover,  cases  are  by  no  means  rare,  in  which  the  gustative  sensibility 
of  the  anterior  part  of  the  tongue  has  been  destroyed,  with  its  tactual  sensi- 
bility; when  there  was  no  reason  to  suppose  that  any  other  than  the  Fifth 
pair  of  nerv.es  was  involved.*  On  the  other  hand,  it  is  equally  certain,  that 
the  sense  of  taste  is  not  destroyed  by  section  of  the  Lingual  nerve  on  each 
side;  and  it  seems  also  well  ascertained,  that  it  is  impaired  by  section  of  the 
Glosso-pharyngeal  nerve.  Considering  how  nearly  allied  is  the  sense  of 
Taste  to  that  of  Touch,  and  bearing  in  mind  the  respective  distribution  of 
these  two  nerves,  it  does  not  seem  difficult  to  arrive  at  the  conclusion,  that  both 
nerves  are  concerned  in  this  function  ;  but  there  seems  good  reason  to  believe 
the  Glosso-pharyngeal  to  be  exclusively  that  through  which  the  impressions 
made  by  disagreeable  substances  taken  into  the  mouth  are  propagated  to  the 
Medulla  Oblongata,  so  as  to  produce  nausea,  and  to  excite  efforts  to  vomit. 

408.  The  functions  of  the  Par  Vagum  at  its  roots  have  lately  been  made 
the  subject  of  particular  examination  by  various  experimenters ;  some  of 
whom  (for  instance,  Bischoff,  Valentin,  Longet,  and  Morgan ti),  have  concluded 
that  it  there  possesses  no  motor  power,  but  is  entirely  a  sensory,  or  rather,  an 
afferent  nerve.  According  to  these,  if  the  roots  be  carefully  separated  from 
those  of  the  Glosso-Pharyngeal,  and  (which  is  a  matter  of  some  difficulty) 
from  those  of  the  spinal  Accessory  nerve,  and  be  then  irritated,  no  movements 
of  the  organs  supplied  by  it  can  be  observed ;  whilst,  if  the  roots  be  irritated 
when  in  connection  with  the  nervous  centres,  muscular  contractions,  evidently 
of  a  reflex  character,  result  from  the  irritation ;  and  strong  evidences  of  their 
sensibility  are  also  given.  It  has  been  further  asserted  that,  when  the  roots 
of  the  Spinal  Accessory  nerve  are  irritated,  no  indications  of  sensation  are 
given ;  but  that  the  muscular  parts  supplied  by  the  Par  Vagum,  as  well  as  by 
its  own  trunk,  are  made  to  contract,  even  when  the  roots  are  separated  from 
the  nervous  centres ;  so  that  these  roots  must  be  regarded  as  the  channel  of 
the  motor  influence,  transmitted  to  them  from  the  Medulla  Oblongata.  When 
the  Par  Vagum  swells  into  the  jugular  ganglion,  an  interchange  of  fibres  takes 
place  between  it  and  the  Spinal  Accessory ;  and  it  seems  clear  that  the  pha- 
ryngeal  branches,  which  are  among  the  most  decidedly  motor  of  all  those 
given  off  from  the  Pneumogastric,  may  in  great  part  be  traced  backwards  into 
the  Spinal  Accessory.  These  statements  confirm  the  idea  of  Arnold  and 
Scarpa, — that  the  Par  Vagum  and  Spinal  Accessory  are  together  analogous  to 
a  spinal  nerve,  the  former  answering  to  the  posterior  roots,  and  the  latter  to 
the  anterior. — But,  on  the  other  hand,  an  equally  numerous  and  trustworthy 
set  of  experimenters  (among  whom  may  be  mentioned  J.  Reid,  Miiller,  Volk- 
mann,  and  Stilling)  are  opposed  to  this  opinion ;  maintaining  that  the  Par  Va- 
gum has  motor  roots  of  its  own,  and  that  the  Spinal  Accessory  possesses  sen- 

*  Romberg,  in  Mxiller's  Archiv.,  1838,  Heft  HI. 


316  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

Fig.  154.  [Fig.  155. 


Origin  and  distribution  of  the  Eighth  pair  of  nerves. 
1,  3,  4,  the  medulla  oblongala;  1,  the  corpus  pyrami- 
dale  of  one  side ;  3,  the  corpus  olivare ;  4,  ihe  cor- 
pus restiforme  ;  2,  the  pons  Varolii ;  5,  the  facial 
nerve  ;  6,  the  origin  of  the  glosso-pharyngeal  nerve  ; 
7,  the  ganglion  of  Andersch ;  8,  the  trunk  of  the  nerve; 
9,  the  spinal  accessory  nerve;  10,  the  ganglion  of  the 
pneumogastric  nerve;  11,  its  plexiform  ganglion; 
12,  its  trunk;  13,  its  pharyngeal  branch  forming  the 
pharyngeal  plexus  (14)  assisted  by  a  branch  from  the 
glosso-pharyngeal  (8)  and  one  from  the  superior  la- 
ryngeal  nerve  (15) ;  16,  cardiac  branches;  17,  recur- 
rent laryngeal  branch ;  18,  anterior  pulmonary 
branches;  19,  posterior  pulmonary  branches;  20, 
03sophageal  plexus  ;  21,  gastric  branches ;  22,  origin 
of  the  spinal  accessory  nerve;  23,  its  branches  dis- 
tributed to  the  sterno-mastoid  muscle  j  24,  its  branches 
to  the  trapezius  muscle. 


A  view  of  the  distribution  of  the  Glosso-Pha 
ryngeal  Pneumogastric  and  Spinal  Accessory 
Nerves,  or  the  Eighth  pair  ;  1,  the  inferior  max- 
illary nerve;  2,  the  gustatory  nerve;  3,  the 
chorda-tympani  ;  4,  the  auricular  nerve ;  5,  its 
communication  with  the  portio  dura;  6,  the  fa- 
cial nerve  coming  out  of  the  stylo-mastoid  fora- 
men ;  7,  the  glosso-pharyngeal  nerve  ;  8,  branch- 
es to  the  stylo-pharyngeus  muscle;  9,  the  pha- 
ryngeal branch  of  the  pneumogastric  nerve 
descending  to  form  the  pharyngeal  plexus;  10, 
branches  of  the  glosso-pharyngeal  to  the  pha- 
ryngeal plexus  ;  11,  the  pneumogastric  nerve  , 
12,  the  pharyngeal  plexus  ;  13,  the  superior  la- 
ryngeal branch  ;  14,  branches  to  the  pharyngeal 
plexus;  15,  15,  communication  of  the  superior 
and  inferior  laryngeal  nerves ;  16,  cardiac 
branches  ;  17,  cardiac  branches  from  the  right 
pneumogastric  nerve  ;  18,  the  left  cardiac  gan- 
glion and  plexus ;  19,  the  recurrent  or  inferior 
laryngeal  nerve;  20,  branches  sent  from  the 
curve  of  the  recurrent  nerve  to  the  pulmonary 
plexus;  21,  the  anterior  pulmonary  plexus;  22, 
22,  the  oesophageal  plexus.] 


FUNCTIONS  OF  THE  PAR  VAGUM.  317 

sory  roots ;  and  affirming  that  irritation  of  the  roots  of  the  Spinal  Accessory 
produces  little  or  no  effect  on  the  muscles  supplied  by  the  trunk  of  the  Par 
Vagum.  The  fact  appears  to  be,  that  the  roots  of  these  two  nerves  are  so 
commingled,  that  it  is  difficult  to  say  what  belong  exclusively  to  each.  Some 
of  the  fibres  usually  considered  to  belong  to  the  Spinal  Accessory,  are  occa- 
sionally seen  to  connect  themselves  with  the  roots  of  the  Par  Vagum,  even 
before  the  ganglion  is  found  upon  it.  And  it  seems  most  probable,  that  the 
roots  of  the  Spinal  Accessory  are  chiefly  motor,  and  those  of  the  Par  Vagum 
chiefly  afferent ;  that  they  inosculate  with  each  other  in  a  degree  which  may 
vary  in  different  species,  and  even  in  different  individuals ;  and  that  the  Par 
Vagum  may  thus  derive  additional  motor  fibres  from  the  Spinal  Accessory, 
whilst  it  supplies  that  nerve  with  additional  afferent  fibres. — In  regard  to  its 
trunk,  there  can  be  no  doubt  that  the  Par  Vagum  is  to  be  considered  as  a 
nerve  of  double  endowments  ;  although  it  is  certain  that  these  endowments 
are  very  differently  distributed  amongst  its  branches.  That  the  nerve  is  capa- 
ble of  conveying  those  impressions  which  become  sensations  when  commu- 
nicated to  the  sensorium,  is  experimentally  proved  by  the  fact  that,  when  its 
trunk  is  pinched,  the  animal  gives  signs  of  acute  pain  ;  but  it  is  also  evident 
from  the  painful  consciousness  we  occasionally  have  of  an  abnormal  condition 
of  the  organs  which  it  supplies.  Thus,  the  suspension  of  the  respiratory 
movements  gives  rise  to  a  feeling  of  the  greatest  uneasiness,  which  must  be 
excited  by  impressions  conveyed  through  this  nerve  from  the  lungs  ;  and  an 
inflamed  state  of  the  walls  of  the  air-passages  causes  the  contact  of  cold  and 
dry  air  to  produce  distressing  pain  and  irritation.  Yet,  of  the  ordinary  im- 
pressions conveyed  from  these  organs,  which  are  concerned  in  producing  the 
respiratory  movements,  and  in  regulating  the  actions  of  the  glottis,  we  are  not 
conscious.  The  same  may  be  said  of  the  portion  of  the  nerve  distributed 
upon  the  alimentary  tube.  The  pharyngeal  branches  are  almost  exclusively 
motor,  the  afferent  function  being  performed  by  the  Glosso-pharyngeal ;  whilst 
the  oesophageal  and  gastric  are  both  afferent  and  motor,  conveying  impressions 
which  excite  reflex  movements  in  the  muscles  of  those  parts,  but  which  do 
not  become  sensations  except  under  extraordinary  circumstances. 

409.  The  section  of  the  Par  Vagum  produces,  as  would  readily  be  expected, 
great  disorder  of  the  functions  of  Respiration  and  Digestion,  to  which  it  minis- 
ters. It  is  an  operation  which  has  been  very  frequently  performed ;  and  the 
statements  of  its  results  vary  considerably  amongst  each  other,  being  generally 
influenced,  in  some  degree,  by  the  preconceived  views  of  the  experimenter.* 
The  section  of  the  Par  Vagum,  when  practised  with  the  view  of  ascertaining 
the  influence  of  the  nerve  upon  the  lungs  and  stomach,  is  usually  made  in  the 
neck,  between  the  origins  of  the  superior  and  inferior  (or  recurrent)  laryngeal 
branches.  Hence  the  muscles  of  the  larynx  are  paralyzed  (§  379) ;  and,  if  the 
animal  should  struggle  violently,  the  ingress  of  air  is  likely  to  be  obstructed 
by  the  flapping  down  of  the  arytenoid  cartilages,  and  by  the  closure  of  the 
glottis.  This  is  especially  the  case  in  young  animals,  in  which  the  larynx  is 
small.  But  in  those  that  are  full  grown,  and  have  a  large  larynx,  an  adequate 
quantity  of  air  may  still  find  its  way  through  the  aperture,  if  the  animal  refrain 
from  any  violent  effort.  In  a  considerable  number  of  Dr.  Reid's  experiments, 
therefore,  he  did  not  find  it  necessary  to  introduce  the  trachea-tube,  which 
other  experimenters  have  generally  employed ;  an  opening  was  made  into  the 
trachea,  however,  in  those  instances  in  which,  from  any  cause,  the  entrance  of 
air  was  obstructed.  . 

*  The  Author  employs,  as  in  his  opinion  the  most  worthy  of  confidence,  the  experiments 
of  Dr.  J.  Reid  (Edinb.  Med.  and  Surg.  Journ.,  vols.  xlix.  and  li.),  on  whose  accuracy  he  has 
strong  personal  reasons  for  placing  reliance;  and  whose  anatomical  and  pathological  attain- 
ments are  such  as  to  render  him  fully  competent  to  the  task. 

27* 


318  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

410.  The  functions  of  the  Pharyngeal  and  Laryngeal  branches  of  the  Pneu- 
mogastric  having  been  already  explained  (§§  378,  379,  and  385),  we  may  now 
proceed  to  its  Pulmonary  division.    In  regard  to  this,  we  have  to  notice,  that 
its  endowments  are  chiefly  afferent;  its  most  important  office  being,  to  con- 
vey to  the  Medulla  Oblongata  the  impression  produced  by  venous  blood  in 
the  capillaries  of  the  lungs,  or  of  carbonic  acid  in  the  air-cells.     This  impres- 
sion may  give  rise,  as  we  have  seen,  to  respiratory  movements,  without  pro- 
ducing sensation;  but  if  it  be  from  any  cause  stronger  than  usual,  the  sense  of 
uneasiness  which  it  occasions  is  very  distressing.     The  impression  may  be 
imitated  by  pressure  on  the  nerve ;  which  occasions  an  immediate  inspiratory 
movement.     Hence  the  chief  function  of  the  afferent  portion  of  the  pulmonary 
division  of  the  Par  Vagum,  is  to  serve  as  an  excitor  to  the  respiratory  move- 
ments ;  which  are  consequently  diminished  in  frequency,  when  the  trunk  is 
divided  on  both  sides. — But  this  division  also  contains  motor  fibres,  which 
are  distributed  upon  the  muscular  fibres  surrounding  the  bronchial  tubes  ;  and 
the  experiments  of  Dr.  Williams,  which  have  been  recently  confirmed  by 
Longet  and  Volkmann,  agree  in  proving,  that  the  calibre  of  the  bronchial  tubes 
can  be  caused  to  contract  in  a  very  considerable  degree,  by  stimuli  applied  to 
this  nerve,  and  especially  by  electricity. 

411.  Various  alterations  are  produced  in  the  Lungs,  by  section  of  the  Pneu- 
mogastric  nerves.     The  order  in  which  these  arise,  and  the  causes  to  which 
they  are  immediately  due,  constitute  very  interesting  subjects  of  investigation; 
and  the  knowledge  of  them  will  probably  throw  light  upon  many  ill-understood 
morbid  phenomena. 

a.  In  the  first  place,  it  has  been  fully  established  by  Dr.  Reid,  that  section  of  the  Vagus 
on  one  side  only  does  not  necessarily,  or  even  generally,  induce  disease  of  that  lung;  and 
hence  the  important  inference  may  be  drawn,  that  the  nerve  does  not  exercise  any  immediate 
influence  on  its  functions.  When  both  Vagi  are  divided,  however,  the  animal  rarely  survives 
long;  but  its  death  frequently  results  from  the  disorder  of  the  digestive  functions.  Never- 
theless, the  power  of  digestion  is  sometimes  restored  sufficiently  to  re-invigorate  the  animals ; 
and  their  lives  may  then  be  prolonged  for  a  considerable  time.  In  fifteen  out  of  seventeen 
animals  experimented  on  by  Dr.  Reid,  the  lungs  were  found  more  or  less  unfit  for  the 
healthy  performance  of  their  functions.  The  most  common  morbid  changes  were  a  congested 
state  of  the  blood-vessels,  and  an  effusion  of  frothy  serum  into  the  air-cells  and  bronchial  tubes. 
In  eight  out  of  the  fifteen,  these  changes  were  strongly  marked.  In  some  portions  of  the 
lungs,  the  quantity  of  blood  was  so  great  as  to  render  them  dense.  The  degree  of  conges- 
tion varied  in  different  parts  of  the  same  lung;  but  it  was  generally  greatest  at  the  most 
depending  portions.  The  condensation  was  generally  greater,  than  could  be  accounted  for 
by  the  mere  congestion  of  blood  in  the  vessels;  and  probably  arose  from  the  escape  of  the 
solid  parts  of  the  blood  into  the  tissue  of  the  lung.  In  some  instances  the  condensation  was 
so  great,  that  considerable  portions  of  the  lung  sank  in  water,  and  did  not  crepitate ;  but 
they  did  not  present  the  granulated  appearance  of  the  second  stage  of  ordinary  pneumonia. 
In  five  cases  in  which  the  animals  had  survived  a  considerable  time,  portions  of  the  lungs 
exhibited  the  second,  and  even  the  third  stages  of  pneumonia,  with  puriform  effusion  into 
the  small  bronchial  tubes ;  and  in  two,  gangrene  had  supervened. 

6.  One  of  the  most  important  points  to  ascertain,  in  an  investigation  of  this  kind,  is  the 
first  departure  from  a  healthy  state ; — to  decide  whether  the  effusion  of  frothy  reddish  serum, 
by  interfering  with  the  usual  change  in  the  lungs,  causes  the  congested  state  of  the  pulmo- 
nary vessels  and  the  laboured  respiration ;  or  whether  the  effusion  is  the  effect  of  a  pre- 
viously congested  state  of  the  blood-vessels.  The  former  is  the  opinion  of  many  physiolo- 
gists, who  have  represented  the  effusion  of  serum  as  a  process  of  morbid  secretion,  directly 
resulting  from  the  disorder  of  that  function  produced  by  the  section  of  the  nerve ;  the  latter 
appears  the  unavoidable  inference  from  the  carefully-noted  results  of  Dr.  Reid's  experiments. 
In  several  of  these,  only  a  very  smalt  quantity  of  frothy  serum  was  found  in  the  air-tubes, 
even  when  the  lungs  were  found  loaded  with  blood,  and  when  the  respiration  before  death 
was  very  laboured.  This  naturally  leads  us  to  doubt,  whether  the  frothy  serum  is  the  cause 
of  the  laboured  respiration,  and  of  the  congested  state  of  the  pulmonary  vessels,  in  those 
cases  where  it  is  present ;  though  there  can  be  no  doubt  that,  when  once  it  is  effused,  it  must 
powerfully  tend  to  increase  the  difficulty  of  respiration,  and  still  further  to  impede  the  cir- 
culation through  the  lungs.  Dr.  R.  has  satisfied  himself  of  an  important  point,  which  has 


FUNCTIONS  OF  THE  PAR  VAGTJM.  319 

been  overlooked  by  others — that  this  frothy  fluid  is  not  mucus,  though  occasionally  mixed 
with  it ;  but  that  it  is  the  frothy  serum  so  frequently  found  in  cases  where  the  circulation 
through  the  lungs  has  been  impeded  before  death.  From  this  and  other  facts,  Dr.  R.  con- 
cludes "  that  the  congestion  of  the  blood-vessels  is  the  first  departure  from  the  healthy  state 
of  the  lung,  and  that  the  effusion  of  frothy  serum  is  a  subsequent  effect." 

c.  The  next  point,  therefore,  to  be  inquired  into,  is  the  cause  of  this  congestion ;  and  this 
is  most  satisfactorily  explained,  upon  the  general  principles  regulating  the  circulation  of  the 
blood,  by  remembering  that  section  of  the  Par  Vagum  greatly  diminishes  the  frequency  of 
the  respiratory  movements,  and  that  the  quantity  of  air  introduced  into  the  lungs  is,  there- 
fore, very  insufficient  for  the  due  aeration  of  the  blood.  We  shall  hereafter  see  reason  to 
regard  it  as  one  of  the  best  established  principles  in  Physiology,  that  the  activity  of  the 
changes  which  the  blood  undergoes  in  the  capillary  vessels,  does,  in  some  way  or  other, 
regulate  its  movement  through  them ; — that,  when  these  changes  are  proceeding  with  ac- 
tivity, the  capillary  circulation  is  proper tionably  accelerated ; — and  that  when  they  are  ab- 
normally low  in  degree,  the  movement  of  the  blood  in  the  capillaries  is  stagnated.  There 
is  now  abundant  evidence,  in  regard  to  the  Pulmonary  circulation  in  particular,  that,  to  pre- 
vent the  admission  of  oxygen  in  the  lungs,  either  by  causing  the  animal  to  breathe  pure 
nitrogen  or  hydrogen,  or  by  occlusion  of  the  air-passages,  is  to  bring  the  circulation  through 
their  capillaries  to  a  speedy  check.  Hence  we  should  at  once' be  led  to  infer,  that  diminu- 
tion in  the  number  of  Respiratory  movements  would  produce  the  same  effect;  and  as  little 
or  no  difference  in  their  frequency  is  produced  by  section  of  one  Vagus  only,  the  usual  ab- 
sence of  morbid  changes  in  the  lung  supplied  by  it  is  fully  accounted  'for.  The  congestion 
of  the  vessels,  induced  by  insufficient  aeration,  satisfactorily  accounts  not  only  for  the  effusion  of 
serum,  but  also  for  the  tendency  to  pass  into  the  inflammatory  condition,  sometimes  pre- 
sented by  the  lungs,  as  by  other  organs  similarly  affected.  Dr.  Reid  confirms  this  view,  by 
the  particulars  of  cases  of  disease  in  the  human  subject,  in  which  the  lungs  presented  after 
death  a  condition  similar  to  that  observed  in  the  lower  animals  after  section  of  the  Vagi ; 
and  in  these  individuals,  the  respiratory  movements  had  been  much  less  frequent  than  natu- 
ral during  the  latter  part  of  life,  owing  to  a  torpid  condition  of  the  nervous  centres.  The 
opinion  (held  especially  by  Dr.  Wilson  Philip)  that  section  of  the  par  vagum  produces  the 
serous  effusion,  by  its  direct  influence  on  the  function  of  Secretion,  is  further  invalidated  by 
the  fact  stated  by  Dr.  Reid, — that  he  always  found  the  bronchial  membrane  covered  with  its 
true  mucus,  except  when  inflammation  was  present. 

"  The  experimental  history  of  the  Par  Vagum,"  it  is  justly  remarked  by 
Dr.  Reid,  "furnishes  an  excellent  illustration  of  the  numerous  difficulties  with 
which  the  physiologist  has  to  contend,  from  the  impossibility  of  insulating 
any  individual  organ  from  its  mutual  actions  and  reactions,  when  he  wishes 
to  examine  the  order  and  dependence  of  its  phenomena."  In  such  investi- 
gations, no  useful  inference  can  be  drawn  from  one  or  two  experiments  only; 
in  order  to  avoid  all  sources  of  fallacy,  a  large  number  must  be  made ;  the 
points  in  which  all  agree  must  be  separated  from  others,  in  which  there  is  a 
variation  of  results ;  and  it  must  be  then  inquired,  to  what  the  latter  is  due. 

412.  These  observations  apply  equally  to  the  other  principal  subject  of  in- 
quiry in  regard  to  the  functions  of  the  Par  Vagum, — its  influence  upon  the 
process  of  Digestion.  The  results  obtained  by  different  experimenters  have 
led  to  differences  of  opinion  as  to  its  action,  no  less  remarkable  than  those 
which  have  prevailed  on  the  question  just  discussed.  Thus,  in  regard  to  the 
afferent  fibres  of  the  Gastric  division  of  the  nerve,  some  physiologists  main- 
tain it  to  be  by  impressions  on  them  alone,  that  the  sense  of  hunger  or  satiety 
is  excited;  whilst  others  deny  that  they  have  any  power  of  transmitting  such 
impressions,  which,  according  to  them,  do  not  originate  in  the  stomach  at  all. 
Dr.  Reid  has  arrived  at  the  conclusion,  from  his  numerous  experiments,  that 
the  Par  Vagum  is  the  channel  through  which  the  mind  becomes  cognizant  of 
the  condition  of  the  stomach ;  but  that  it  is  not  the  sole  excitor  of  the  sense 
of  hunger.  Animals,  which  have  sustained  section  of  the  nerve  on  both  sides, 
will  eagerly  take  food,  if  they  have  not  received  too  great  a  shock  from  the 
operation ;  but  they  seem  to  experience  no  feeling  of  satiety  when  the  sto- 
mach is  loaded.  This  inference  is  confirmed  by  Valentin,  who  mentions  that 
puppies  after  the  operation  will  take  three  times  the  same  quantity  of  milk, 
as  uninjured  individuals  of  the  same  age,  so  as  greatly  to  distend  the  abdomen. 


320  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

The  act  of  Vomiting  has  been  proved  to  be  excitable  by  impressions  trans- 
mitted through  the  Gastric  branches  of  the  Par  Vagum  ;  although  they  con- 
stitute by  no  means  the  only  channel,  through  which  the  various  muscles  con- 
cerned in  it  may  be  called  into  combined  action  (§  505). 

413.  The  question  of  the  influence  of  the   motor  fibres  of  the  Pneumo- 
gastric,  upon  the  muscular  walls  of  the  stomach,  has  been  already  in  part  dis- 
cussed (§  387).     Although  it  seems  unquestionable  that  they  have  the  power 
of  stimulating  these   muscles  to  contraction,  yet  there  is  evidence  that  the 
movements  of  the  stomach,  which  are  most  essential  to  digestion,  may  take 
place  without  it.     Thus  Dr.  Reid  found,  in  several  of  his  experiments,  that 
food  was  not  only  digested  in  the  Stomach,  but  propelled  into  the  Duodenum, 
subsequently  to  the  operation.     It  seems  very  probable,  however,  that  a  tem- 
porary suspension  of  these  movements  (as  of  other  independent  functions  of 
the  stomach)  may  be  the  first  effect  of  the  operation. 

414.  It  is   necessary  here  to  stop  to  notice,  on  account  of  the  currency 
which  it  has  obtained,  the  doctrine  of  Dr.  Wilson  Philip ; — that  the  Par  Va- 
gum controls  the  secretion  of  the  Gastric  fluid ;  and  that  its  division  checks 
the  secretion.     He  further  stated,  that  the  influence  of  Galvanism  propagated 
along  the  nerve,  would  re-establish  the  secretion.  This  statement  has  been  quoted 
and  re-quoted,  as  an  established  physiological  position  ;  and,  when  united  with 
the  well-known  fact,  that  galvanism  would  excite  muscular  contraction,  it  has 
seemed  to  Dr.  W.  Philip  and  other  physiologists   sufficient  to  establish  the 
important  position,  that  galvanism  and  nervous  influence  are  identical.     It  has 
been  disputed,  however,  by  many  other  experimenters ;  who  have  satisfied 
themselves  that  the  secretion  of  gastric  juice  continues  after  the  operation ; 
and  consequently,  that  the  elaboration  of  this  product  cannot  be  dependent  on 
nervous  influence  supplied  by  the  Par  Vagum,  though  doubtless  in  part  regu- 
lated by  it.     The  first  effects  of  the  operation,  however,  are  almost  invariably 
found  to  be  vomiting  (in  those   animals  capable  of  it),  loathing  of  food,  ami 
arrestment  of  the  digestive  process  ;  and  it  is  not  until  after  four  or  five  days, 
that  the  power  seems  re-established.     In  the  animals  which  died  before  that 
time,  no  indication  of  it  could  be  discovered  by  Dr.  R. ;  in  those  which  survived 
longer,  great  emaciation  took  place ;  but  when  life  was  sufficiently  prolonged,  the 
power  of  assimilation  seemed  almost  completely  restored.     This  was  the 
case  in  four  out  of  the  seventeen  dogs  experimented  on  ;  and  the  evidence  of 
this  restoration  consisted  in  the  recovery  of  flesh  and  blood  by  the  animals, 
the  vomiting  of  half-digested  food  permanently  reddening  litmus  paper,  the 
disappearance  of  a  considerable  quantity  of  alimentary  matter  from  the  intes- 
tinal canal,  and  the  existence  of  chyle  in  the  lacteals.     It  may  serve  to  account 
in  some  degree  for  the  contrary  results,  obtained  by  other  experimenters,  to 
state  that  seven  out  of  Dr.  R.'s  seventeen  experiments  were  performed  before 
he  obtained  any  evidence  of  digestion  after  the  operation ;  and  that  the  four 
which  furnished  this  followed  one  another  almost  in  succession  ;  so  that  it  is 
easy  to  understand  why  those  who  were  satisfied  with  a  small  number  of 
experiments,  should  have  been  led  to  deny  it  altogether. 

[M.  Bernard  has  instituted  fresh  experiments  to  determine  this  still-debated  question, 
making  use  of  the  artificial  fistulous  openings  into  the  stomach,  invented  by  M.  Blondlot. 
A  dog's  digestion  had  been  thus  watched  for  eight  days,  and  had  always  been  well  effected. 
On  the  ninth  day,  after  a  day's  fast,  M.  Bernard  sponged  out  the  stomach,  which  contracted 
on  the  contact  of  the  sponge,  and  at  once  secreted  a  large  quantity  of  gastric  fluid  ;  he  then 
divided  the  pneumogastric  nerves  in  the  middle  of  the  neck,  and  immediately  the  mucous 
membrane,  which  had  been  turgid,  became  pale,  as  if  exsanguine,  its  movements  ceased, 
the  secretion  of  gastric  fluid  was  instantaneously  put  a  stop  to,  and  a  quantity  of  ropy  neutral 
mucus  was  soon  produced  in  its  place.  After  this,  no  digestion  was  duly  performed,  and 
milk  was  no  longer  coagulated;  raw  meat  remained  unchanged,  and  the  food  (meat,  milk, 
bread  and  sugar,  which  the  dog  had  before  thoroughly  digested)  remained  for  a  long  time 


FUNCTIONS  OF  THE  PAR  VAGUM.  321 

neutral,  and  at  last  acquired  acidity  only  from  its  own  transformation  into  lactic  acid.  In 
the  stomachs  of  otljer  dogs  after  the  division  of  the  nerves,  he  traced  the  transformation  of 
cane-sugar  into  grape-sugar  in  three  or  four  hours ;  and  in  ten  or  twelve  hours  the  trans- 
formation into  lactic  acid  was  complete.  In  others,  when  the  food  was  not  capable  of  an 
acid  transformation,  it  remained  neutral  to  the  last.  In  no  case  did  any  part  of  the  food  pass 
through  the  peculiar  changes  of  chymification.  In  a  last  experiment,  he  gave  to  each  of  two 
dogs,  in  one  of  which  he  had  cut  the  nerves,  a  dose  of  emulsine,  and  half  an  hour  after,  a 
dose  of  am ygdaline  (substances  which  are  innocent  alone,  but  when  mixed  produce  hydro- 
cyanic acid).  The  dog,  whose  nerves  were  cut,  died  in  a  quarter  of  an  hour,  the  sub- 
stances being  absorbed  unaltered  and  mixing  in  the  blood:  in  the  other,  the  emulsine  was 
changed  by  the  action  of  the  gastric  fluid  before  the  amygdaline  was  administered,  and  it 
survived. — Gazette  Med.,  Juin  1,  1844,/rom  tlie  Report  of  the  jlcad.  des  Sri.,  seance  du  27  Mai, 
1844.— M.  C.] 

a.  Another  series  of  experiments  was  performed  by  Dr.  Reid,  for  the  purpose  of  testing 
the  validity  of  the  results  obtained  by  Sir  B.  Brodie,  relative  to  the  effects  of  section  of  the 
Par  Vagum  upon  the  secretions  of  the  stomach,  after  the  introduction  of  arsenious  acid  into 
the  system.  According  to  that  eminent  Surgeon  and  Physiologist,  when  the  poison  was 
introduced  after  the  Par  Vagum  had  been  divided  on  each  side,  the  quantity  of  the  pro- 
tective mucous  and  watery  secretions  was  much  less  than  usual,  although  obvious  marks  of 
inflammation  were  present.  In  order  to  avoid  error  as  much  as  possible,  Dr.  Reid  made  five 
sets  of  experiments,  employing  two  dogs  in  each,  as  nearly  as  possible  of  equal  size  and 
strength,  introducing  the  same  quantity  of  the  poison,  into  the  system  of  each  in  the  same 
manner,  but  cutting  the  Vagi  in  one,  and  leaving  them  entire  in  the  other.  This  comparative 
mode  of  experimenting  is  obviously  the  only  one  admissible  in  such  an  investigation.  Its 
result  was  in  eveiy  instance  opposed  to  the  statements  of  Sir  B.  Brodie ;  the  quantity  of  the 
mucous  and  watery  secretions  of  the  stomach  being  nearly  the  same,  in  each  individual  of 
the  respective  pairs  subjected  to  experiment;  so  that  they  can  no  longer  be  referred  to  the 
influence  of  the  Eighth  pair  of  nerves.  Moreover,  the  appearances  of  inflammation  were,  in 
four  out  of  the  five  cases,  greatest  in  the  animals  whose  Vagi  were  left  entire ;  and  this  seemed 
to  be  referrible  to  the  longer  duration  of  their  lives  after  the  arsenic  had  been  introduced. 
The  results  of  Sir  B.  Brodie's  experiments  may  perhaps  be  explained,  by  the  Speedy  occur- 
rence of  death  in  the  subjects  of  them,  consequent  (it  may  be)  upon  the  want  of  suffi- 
ciently free  respiration,  which  was  carefully  guarded  against  by  Dr.  Reid. 

415.  So  far  as  the  results  of  Dr.  Reid's  experiments  may  be  trusted  to, 
therefore,  (and  the  Author  is   himself  disposed  to  rely  on  them  almost  im- 
plicitly,) all  the  arguments  which  have  been  drawn  in  favour  of  the  doctrine 
that  Secretion  depends  upon  Nervous  agency,  from  the  effects  of  lesion  of  the 
Vagi  upon  the  functions  of  the  Stomach,  must  be  set  aside.     That  this  nerve 
has  an  important  influence  on  the  gastric  secretion,  is  evident  from  the  defi- 
ciency in  its  amount  soon  after  the  operation,  as  well  as  from   other  facts. 
But  this  is  a  very  different  proposition  from  that  just  alluded  to;  and  the 
difference  has  been  very  happily  illustrated  by  Dr.  R.     "The  movements  of' 
a  horse,"  he  observes,  "  are  independent  of  the  rider  on  his  back, — in  other 
words,  the  rider  does  not  furnish  the  conditions  necessary  for  the  movements 
of  the  horse; — but  everyone  knows  how  much  these  movements   maybe 
influenced  by  the  hand  and  heel  of  the  rider."     It  may  be  hoped,  then,  that 
physiologists  will  cease  to  adduce  the  oft-cited  experiments  of  Dr.  Wilson 
Philip,  in  favour  of  the  hypothesis  (for  such  it  must  be  termed)  that  secretion 
is  dependent  upon  nervous  influence,  and  that  this  is  identical  with  galvan- 
ism.— Additional  evidence  of  their  fallacy  is  derived  from  the  fact  mentioned 
by  Dr.  Reid,  that  the  usual  mucous  secretions  of  the  stomach  were  always 
found;  and  they  are   further  invalidated  by  the  testimony  of  Miiller,  who 
denies  that  galvanism  has  any  peculiar  influence  in  re-establishing  the  gastric 
secretion,  when  it  has  been  checked  by  section  of  the  nerves. 

416.  It  only  remains  to  notice  the  influence  of  section  of  the  Vagi  upon 
the  actions  of  the  Heart.     It  has  been  asserted  by  Valentin  and  other  experi- 
menters, that  mechanical  irritation  of  these  nerves,  especially  at  their  roots, 
has  a  tendency  to  excite  or  accelerate  the  heart's  action ;  other  experimenters, 
however,  have  obtained  none  but  negative  results.     Admitting,  what  seems 
probable,  that  the  Cardiac  branches  of  the  Pneumogastric  have  some  influence 


322  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

upon  the  Heart's  action,  it  remains  to  inquire  whether  that  influence  is  essen- 
tial to  its  movements ;  and  whether  these  nerves  form  the  channel,  through 
which  they  are  affected  by  emotions  of  the  mind,  or  by  conditions  of  the 
bodily  system.  In  regard  to  the  first  point,  no  doubt  can  be  entertained; 
since  the  regular  movements  of  the  heart  are  but  little  affected  by  section  of 
the  Vagi.  With  respect  to  the  second,  there  is  more  difficulty ;  since  the 
number  of  causes,  which  may  influence  the  rapidity  and  pulsations  of  the 
heart,  is  very  considerable.  For  example,  when  the  blood  is  forced  on  more 
rapidly  towards  the  heart,  as  in  exercise,  struggling,  &c.,  the  stimulus  to  its 
contractions  is  more  frequently  renewed,  and  they  become  more  frequent; 
and  when  the  current  moves  on  more  slowly,  as  in  a  state  of  rest,  their  fre- 
quency becomes  proportionably  diminished.  If  the  contractions  of  the  heart 
were  not  dependent  upon  the  blood,  and  their  number  were  not  regulated  by 
the  quantity  flowing  into  its  cavities,  very  serious  and  inevitably  fatal  dis- 
turbances of  the  heart's  action  would  soon  result.  That  this  adjustment  takes 
place  otherwise  than  through  the  medium  of  the  nervous  centres,  is  evident 
from  the  fact  that,  in  a  dog,  in  which  the  par  vagum  and  sympathetic  had 
been  divided  in  the  neck  on  each  side,  violent  struggling,  induced  by  alarm, 
raised  the  number  of  pulsations  from  130  to  260  per  minute.  It  is  difficult 
to  ascertain,  by  experiment  upon  the  lower  animals,  whether  simple  emotion, 
unattended  with  struggling  or  other  exertion,  would  affect  the  pulsation  of  the 
heart,  after  section  of  the  Vagi;  but  when  the  large  proportion  of  the  Sympa- 
thetic nerves  proceeding  to  this  organ  is  considered,  and  when  it  is  also  re- 
membered that  irritation  of  the  roots  of  the  upper  cervical  nerves  stimulates 
the  action  of  the  heart  through  these,  we  can  scarcely  doubt  that  both  may 
serve  as  the  channels  of  this  influence,  especially  in  such  animals  as  the  dog, 
in  which  the  two  freely  inosculate  in  the  neck. 

417.  In  regard  to  the  functions  of  the  Spinal  Accessory  nerve,  also,  there 
has  been  great  difference  of  opinion ;  the  peculiarity  of  its  origin  and  course 
having  led  to  the  belief,  that  some  very  especial  purpose  is  answered  by  it. 
The  predominance  of  motor  fibres  in  its  roots,  its  inosculation  with  the  Par 
Vagum,  and  its  probable  reception  of  sensory  fibres  from  the  latter  whilst 
imparting  to  it  motor  filaments,  have  been  already  referred  to  (§  408).  As  its 
trunk  passes  through  the  foramen  lacerum,  it  divides  into  two  branches;  of 
which  the  internal,  after  giving  off  some  filaments  that  assist  in  forming  the 
pharyngeal  branch  of  the  Par  Vagum,  becomes  incorporated  with  the  trunk  of 
that  nerve;  whilst  the  external  proceeds  outwards,  and  is  finally  distributed  to 
the  sterno-cleido-mastoideus  and  trapezius  muscles,  some  of  its  filaments 
inosculating  with  those  of  the  cervical  plexus.  When  the  external  branch  is 
irritated,  before  it  perforates  the  sterno-mastoid  muscles,  vigorous  convulsive 
movements  of  that  muscle,  and  of  the  trapezius,  are  produced;  and  the  animal 
does  not  give  any  signs  of  pain,  unless  the  nerve  is  firmly  compressed  between 
the  forceps,  or  is  included  in  a  tight  ligature.  Hence  it  may  be  inferred,  that 
the  functions  of  this  nerve  are  chiefly  motor,  and  that  its  sensory  filaments  are 
few  in  number.  Further,  when  the  nerve  has  been  cut  across,  or  firmly  tied, 
irritation  of  the  lower  end  is  attended  by  the  same  convulsive  movements  of 
the  muscles ;  whilst  irritation  of  the  upper  end,  in  connection  with  the  spinal 
cord,  is  unattended  with  any  muscular  movement.  Hence  it  is  clear  that  the 
motions  occasioned  by  irritating  it  are  of  a  direct,  not  of  a  reflex  character. 
The  same  muscular  movements  are  observed  on  irritating  the  nerve  in  the 
recently-killed  animal,  as  during  life. 

a.  According  to  Sir  C.  Bell,  the  Spinal  Accessory  is  a  purely  Respiratory  nerve,  whose  office 
it  is  to  excite  the  involuntary  or  automatic  movements  of  the  muscles  it  supplies,  which 
share  in  the  act  of  respiration ;  and  he  states  that  the  division  of  it  paralyzes  the  muscles  to 
which  it  is  distributed,  as  muscles  of  respiration ;  though  they  still  perform  the  voluntary 


HYPOGLOSSAL  NERVE.  323 

movements,  through  the  medium  of  the  spinal  nerves.  Both  Valentin  and  Dr.  Reid,  however, 
positively  deny  that  this  is  the  case.  Dr.  Reid's  method  of  experimenting  was  well  adapted 
to  test  the  truth  of  the  assertion.  Considering  that,  in  the  ordinary  condition  of  the  animal, 
it  might  be  difficult  to  distinguish  the  actions  of  particular  muscles,  beneath  the  skin,  when 
those  in  the  neighbourhood  were  in  operation ;  and  also  that  the  usual  automatic  movements 
might  be  simulated  by  voluntary  action,  when  the  breathing  might  be  rendered  difficult ;  he 
adopted  the  following  plan  : — A  small  dose  of  prussic  acid  was  given  to  an  animal,  in  which 
the  Spinal  Accessory  had  been  previously  divided  on  one  side ;  and  after  the  convulsive 
movements  produced  by  it  had  ceased,  the  animal  was  generally  found  in  a  state  similar  to 
that  which  we  sometimes  see  in  apoplexy,— the  action  of  the  heart  going  on,  the  respirations 
being  slow  and  heaving,  and  the  sensorial  functions  appearing  to  be  completely  suspended. 
The  Respiratory  movements  always  ceased  before  the  action  of  the  heart;  but  they  con- 
tinued, in  several  of  the  animals  experimented  on,  sufficiently  long  to  allow  the  muscles  Of 
the  anterior  part  of  the  neck  to  be  laid  bare,  so  that  accurate  observations  could  be  made 
upon  their  contractions.  In  the  dog  and  cat,  the  sterno-mastoid  does  not  appear  to  have 
much  participation  in  the  ordinary  movements  of  respiration ;  for  in  several  instances  it 
could  not  be  seen  to  contract  on  either  side,  though  the  head  was  forcibly  pulled  towards  the 
chest  at  each  inspiratory  movement,  chiefly  by  the  action  of  the  sterno-hyoid  and  thyroid 
muscles.  In  two  dogs  and  one  cat,  however,  in  which  the  head  was  fixed,  and  these 
respiratory  movements  were  particularly  vigorous,  distinct  contractions  were  seen  in  the 
exposed  sterno-mastoid  muscles,  synchronous,  with  the  other  movements  of  respiration  :  these 
were,  perhaps,  somewhat  weaker  on  the  side  on  which  the  nerve  had  been  cut,  but  were 
still  decidedly  present.  In  one  of  these  dogs,  similar  movements  were  observed  in  the 
trapezius,  on  the  side  on  which  the  nerve  had  been  divided.  As  the  condition  of  the  animal 
forbade  the  idea  that  volition  could  be  the  cause  of  these  movements,  it  can  scarcely  be  ques- 
tioned that  Sir  C.  Bell's  statement  was  an  erroneous  one.  As  far,  therefore,  as  these  experi- 
ments afford  any  positive  data,  in  regard  to  the  functions  of  this  nerve,  it  may  be  concluded 
that  they  are  the  same  as  those  of  the  cervical  plexus,  with  which  it  anastomoses  freely. 
"Future  anatomical  researches,"  as  Dr.  Reid  justly  remarks,  "may  perhaps  explain  to  us  how 
it  follows  this  peculiar  course,  without  obliging  us  to  suppose  that  it  has  a  reference  to  any 
special  function  in  the  adult  of  the  human  species."  Thus,  the  study  of  the  history  of 
development  has  accounted  satisfactorily  for  the  peculiar  course  of  the  recurrent  laryngeal, 
which  may  be  traced  passing  directly  from  the  par  vagum  to  the  larynx,  at  a  time  when  the 
neck  can  scarcely  be  said  to  exist,  and  when  that  organ  is  buried  in  the  thorax.  As  this 
rises  in  the  neck,  the  nerve,  which  at  first  came  off  below  the  great  transverse  blood-vessels, 
has  both  its  origin  and  its  termination  carried  upwards ;  whilst  it  is  still  tied  down  by  these 
vessels  in  the  middle  of  its  course. 

418.  The  Hypo  glossal  nerve,  or  Motor  Linguae,  is  the  only  one  which, 
in  the  regular  order,  now  remains  to  be  considered.  That  the  distribution  of 
this  nerve  is  restricted  to  the  muscles  of  the  tongue,  is  a  point  very  easily 
established  by  anatomical  research ;  and  accordingly  we  find  that,  long  before 
the  time  of  Sir  C.  Bell,  Willis  spoke  of  it  as  the  nerve  of  the  motions  of 
articulation,  whilst  to  the  Lingual  branch  of  the  fifth  pair  he  attributed  the 
power  of  exercising  the  sense  of  taste ;  and  he  distinctly  stated,  that  the 
reason  of  this  organ  being  supplied  with  two  nerves  is  its  double  function. 
The  inference  that  it  is  chiefly,  if  not  entirely,  a  motor  nerve,  which  has  been 
founded  upon  its  anatomical  distribution,  is  supported  also  by  the  nature  of 
its  origin,  which  is  usually  from  a  single  root,  corresponding  to  the  anterior 
root  of  the  Spinal  nerves.  Experiment  shows  that,  when  the  trunk  of  the 
nerve  is  stretched,  pinched,  or  galvanized,  violent  motions  of  the  whole  tongue, 
even  to  its  tip,  are  occasioned;  and  also,  that  similar  movements  take  place 
after  division  of  the  nerve,  when  the  cut  end  most  distant  from  the  brain  is 
irritated.  In  regard  to  the  degree  in  which  this  nerve  possesses  sensory  pro- 
perties, there  is  some  difference  of  opinion  amongst  physiologists,  founded,  as 
it  would  seem,  on  a  variation  in  this  respect  between  different  animals. 
Indications  of  pain  are  usually  given,  when  the  trunk  is  irritated  after  its  exit 
from  the  cranium;  but  these  may  proceed  from  its  free  anastomosis  with  the 
cervical  nerves,  which  not  improbably  impart  sensory  fibres  to  it.  But  in 
some  Mammalia,  the  hypoglossal  nerve  has  been  found  to  possess  a  small 
posterior  root  with  a  ganglion:  this  is  the  case  in  the  ox,  and  also  in  the  rabbit; 


324  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

and  in  the  latter  animal,  Valentin  states  that  the  two  trunks  pass  out  from  the 
cranium  through  separate  orifices,  and  that,  after  their  exit,  one  may  be  shown 

[Fig.  156. 


The  course  and  distribution  of  the  Hypo-Glossal  or  Ninth  pair  of  nerves ;  the  deep-seated  nerves  of 
the  neck  are  also  seen ;  1,  the  hypo-glossal  nerve ;  2,  branches  communicating  with  the  gustatory  nerve ; 
3,  a  branch  to  the  origin  of  the  hyoid  muscles ;  4,  the  descendens  noni  nerve ;  5,  the  loop  formed  with  the 
branch  from  the  cervical  nerves ;  6,  muscular  branches  to  the  depressor  muscles  of  the  larynx  ;  7,  a 
filament  from  the  second  cervical  nerve,  and  8,  a  filament  from  the  third  cervical,  uniting  to  form  the 
communicating  branch  with  the  loop  from  the  descendens  noni ;  9,  the  auricular  nerve ;  10,  the  inferior 
dental  nerve  ;  11,  its  mylo-hyoidean  branch;  12,  the  gustatory  nerve  ;  13,  the  chorda-tympani  passing  to 
the  gustatory  nerve;  14,  the  chorda-tympani  leaving  the  gustatory  nerve  to  join  the  sub-maxillary 
ganglion;  15,  the  sub-maxillary  ganglion;  16,  filaments  of  communication  with  the  lingual  nerve;  17, 
the  glosso-pharyngeal  nerve  ;  18,  the  pneumogastric  or  par  vagum  nerve;  19,  the  three  upper  cervical 
nerves;  20,  the  four  inferior  cervical  nerves;  21,  the  first  dorsal  nerve;  22,  23,  the  brachial  plexus ;  24, 
25,  the  phrenic  nerve;  26,  the  carotid  artery;  27,  the  internal  jugular  vein.] 

to  be  sensory,  and  the  other  to  be  motor.  Hence,  this  nerve,  which  is  the 
lowest  of  those  that  originate  in  the  cephalic  prolongation  of  the  spinal  cord, 
generally  known  as  the  medulla  oblongata,  approaches  very  closely  in  some 
animals  to  the  regular  type  of  the  spinal  nerves ;  and  though  in  Man  it  still 
manifests  an  irregularity,  in  having  only  a  single  root,  yet  this  irregularity  is 
often  shared  by  the  first  cervical  nerve,  which  also  has  sometimes  an  anterior 
root  only. 

419.  The  Hypoglossal  nerve  is  distributed  not  merely  to  the  tongue,  but  to 
the  muscles  of  the  neck  which  are  concerned  in.  the  movements  of  the  larynx  ; 
and  the  purpose  of  this  distribution  is  probably  to  associate  them  in  those 
actions,  which  are  necessary  for  articulate  speech.  Though  all  the  motions 
of  the  tongue  are  performed  through  the  medium  of  this  nerve,  yet  it  would 
appear,  from  pathological  phenomena,  to  have  at  least  two  distinct  connec- 
tions with  the  nervous  centres ;  for  in  many  cases  of  paralysis,  the  masticatory 
movements  of  the  tongue  are  but  little  affected,  when  the  power  of  articula- 
tion is  much  injured  or  totally  destroyed  :  and  the  converse  may  be  occasion- 
ally noticed.  When  this  nerve  is  paralyzed  on  one  side,  in  hemiplegia,  it 
will  be  generally  observed  that  the  tongue,  when  the  patient  is  directed  to  put 


CEPHALIC  NERVES  IN  GENERAL.  325 

it  out,  is  projected  towards  the  palsied  side  of  the  face :  this  is  due  to  the 
want  of  action  of  the  lingual  muscles  of  that  side,  which  do  not  aid  in  pushing 
forward  the  tip ;  the  point  is  consequently  directed  only  by  the  muscles  of 
the  other  side,  which  will  not  act  in  a  straight  direction,  when  unantagonized 
by  their  fellows.  It  is  a  curious  fact,  however,  that  the  hypoglossal  nerve 
seems  not  to  be  always  palsied  on  the  same  side  with  the  facial,  but  sometimes 
on  the  other.  This  has  been  suggested  to  be  due  to  the  origination  of  the 
roots  of  this  nerve  from  near  the  point,  at  which  the  pyramids  of  the  medulla 
oblongata  decussate ;  so  that  some  of  its  fibres  come  off,  like  those  of  the 
spinal  nerves,  without  crossing ;  whilst  others  are  transmitted  to  the  opposite 
side,  like  those  of  the  higher  cerebral  nerves  ;  and  the  cause  of  paralysis  may 
affect  one  or  other  of  these  sets  of  roots  more  particularly.  Whatever  may 
be  the  validity  of  this  explanation,  the  circumstance  is  an  interesting  one,  and 
well  worthy  of  attention.* 

420.  The  general  character  and  arrangement  of  the  Cephalic  nerves,  as 
distinguished  from   the  ordinary  Spinal,  constitute  a  study  of  much  interest, 
when  considered  in  relation  to  Comparative  Anatomy,  and  to  Embryology.  It 
appears,  from   what  has  been   already  stated,  that  the  Par  Vagum,  Spinal 
Accessory,  Glosso-pharyngeal,  and   Hypoglossal  nerves,  may  be  considered 
nearly  in  the  light  of  ordinary  Spinal  nerves.     They  all  take  their  origin  ex- 
clusively in  the  Medulla  Oblongata ;  and  the  want  of  correspondence  in  posi- 
tion, between  their  roots  and  those  of  the  Spinal  nerves,  is  readily  accounted 
for  by  the  alteration   in  the  direction  of  the  columns   of  the   Spinal  Cord, 
which, — as  long  since  pointed  out  by  Rosenthal,  and  lately  stated  prominently 
by  Dr.  Reid, — not  only  decussate  laterally,  but,  as  it  were,  antero-posteriorly 
(§  353).     The  Hypoglossal,  as  just  stated,  not  unfrequently  possesses  a  sen- 
sory in  addition  to  its  motor  root.     The  Glosso-pharyngeal,  which  is  princi- 
pally an  afferent  nerve,  is  stated  by  Arnold  and  others  to  have  a  small  motor 
root;  at  any  rate,  the  motor  fibres  which  answer  to  it  are  to  be  found  in  the 
Par  Vagum.     That  the  Par  Vagum  and   a  portion  of  the   Spinal  Accessory 
together  make  up  a  spinal  nerve,  has  been  already  stated  as  probable. 

421.  Leaving  these  nerves  out  of  the  question,  therefore,  we  proceed  to  the 
rest.     Comparative  anatomy,  and  the  study  of  Embryonic  development,  alike 
show  that  the  Spinal  cord  and  Medulla  Oblongata  constitute  the  most  essen- 
tial part  of  the  nervous   system  in  Vertebrata ;  and  that  the  Cerebral  Hemi- 
spheres are  superadded,  as  it  were,  to  this.     At  an  early  period  of  develop- 
ment, the   Encephalon   consists  chiefly  of  three  vesicles,  which  correspond 
with  the  ganglionic  enlargements  of  the  nervous  cord  of  the  Articulata,  and 
mark  three  divisions  of  the  cerebro-spinal  axis ;  and,  in  accordance  with  this 
view,  the  Osteologist  is  able  to  trace,  in   the  bones  of  the  cranium,  the  same 
elements  which  would  form  three  vertebrae,  in  a  much  expanded  and  altered 
condition.     However  improbable  such  an  idea  might  seem,  when  the  cranium 
of  the  higher  Vertebrata  alone  is  examined,  it  at  once  reconciles  itself  to  our 
reason,  when  we  direct  our  attention  to  that  of  Reptiles    and   Fishes ;  in 
which  classes  the  size  of  the  Cerebral  or  hemispheric  ganglia  is  very  small, 
in  comparison  with  that  of  the  Ganglia  of  special  sensation;  and  in  which  the 
latter  evidently  form  but  a  continuation  of  the  Spinal   Cord,  modified  in  its 
function  ;  so  that,  when  we  trace  upwards   the  cavity  of  the  spinal  column 
into  that  of  the  cranium,  we  encounter  no  material  change,  either  in  its  size  or 

*  It  may  be  questioned,  however,  whether  the  Hypoglossal  is  really  paralyzed  on  the  op- 
posite side  from  the  facial  in  such  cases.  An  instance  has  been  communicated  to  the  Author 
by  Dr.  W.  Budd,  in  which  the  hypoglossal  nerve  was  completely  divided  on  one  side;  and 
yet  the  tip  of  the  tongue,  when  the  patient  was  desired  to  put  it  out,  was  sometimes  directed 
from  and  sometimes  towards  the  palsied  side ;  showing  that  the  muscles  of  either  half  are 
sufficient  to  give  any  required  direction  to  the  whole. 
28 


326  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

direction.  The  three  pairs  of  nerves  of  special  sensation  make  their  way 
out  through  these  three  cranial  vertebrae  respectively.  At  a  later  period  of 
development,  other  nerves  are  interposed  between  these  ;  which,  being  inter- 
vertebral,  are  evidently  more  analogous  to  the  Spinal  nerves,  both  in  situation 
and  function.  A  separation  of  the  primitive  fibres  of  these  takes  place,  how- 
ever, during  the  progress  of  development,  so  that  their  distribution  appears 
irregular.  Thus  the  greater  part  of  the  sensory  fibres  are  contained  in  the 
large  division  of  the  Trigeminus ;  whilst,  of  the  motor  fibres,  the  anterior 
ones  chiefly  pass  forwards  as  the  Oculo-motor  and  Patheticus ;  and  of  the 
posterior,  some  form  the  small  division  of  the  Trigeminus,  and  others  unite 
with  the  first  pair  from  the  Medulla  Oblongata  to  form  the  Facial.  This  last 
fact  explains  the  close  union  which  is  found  in  Fishes  and  some  Amphibia, 
between  that  nerve  and  those  proceeding  more  directly  from  the  Medulla  Ob- 
longata. According  to  Valentin,  the  Glosso-pharyngeal  is  the  sensory  por- 
tion of  the  first  pair  from  the  Medulla  Oblongata,  of  which  the  motor  part  is 
chiefly  comprehended  in  the  Facial  nerve.  It  is  very  interesting  to  trace  this 
gradual  metamorphosis  from  the  character  of  the  Spinal  nerves,  which  is  ex- 
hibited in  the  Cephalic,  when  they  are  traced  upwards  from  the  Medulla  Ob- 
longata ;  and  this  is  shown  also,  in  some  degree,  in  the  nerves  of  special  sen- 
sation (§  446,  a).  Although  we  are  accustomed  to  consider  the  Fifth  pair  as 
par  eminence  the  Spinal  nerve  of  the  head,  the  foregoing  statements,  founded 
upon  the  history  of  development,  show  that  the  nerves  of  the  Orbit  really 
belong  to  its  motor  portion  ;  they  may  consequently  be  regarded  as  altogether 
forming  the  first  of  the  inter  vertebral  or  Spinal  nerves  of  the  cranium..  The 
Facial  and  Glosso-pharyngeal  appear  to  constitute  the  second ;  whilst  the  Par 
Vagum  and  Spinal  Accessory,  forming  the  third  pair,  intervene  between  this 
and  the  true  spinal,  of  which  the  Hypoglossal  may  be  considered  as  the  first. 

5.   Of  the  Sensory  Ganglia  and  their  Functions. — Consensual  Movements. 

422.  At  the  base  of  the  Brain  in  Man,  concealed  by  the  Cerebral  Hemi- 
spheres, but  still  readily  distinguishable  from  them,  we  find  a  series  of  gan- 
glionic  masses ;  which  are  in  direct  connection  with  the  nerves  of  Sensation; 
and  which  appear  to  have  functions  quite  independent  of  those  of  the  other 
components  of  the  Encephalon. — Thus  anteriorly  we  have  the  Olfactive 
ganglia,  in  what  are  commonly  termed  the  bulbous  expansions  of  the  Olfactive 
nerve.  That  these  are  real  ganglia,  is  proved  by  their  containing  grey  or  ve- 
sicular substance  ;  and  their  separation  from  the  general  mass  of  the  Encepha- 
lon, by  the  peduncles  or  footstalks  commonly  termed  the  trunks  of  the  Olfac- 
tory nerves,  finds  its  analogy  in  many  species  of  Fish  (§  357).  The  ganglionic 
nature  of  these  masses  is  more  evident  in  many  of  the  lower  Mammalia,  in 
which  the  organ  of  smell  is  highly  developed,  than  it  is  in  Man,  whose  olfac- 
tive  powers  are  comparatively  moderate. — At  some  distance  behind  these,  we 
have  the  representatives  of  the  Optic  ganglia,  in  the  Tubercula  Quadrigemina, 
to  which  the  principal  part  of  the  roots  of  the  Optic  nerve  may  be  traced. 
Although  these  bodies  are  so  small  in  Man,  in  comparison  to  the  whole  En- 
cephalic mass,  as  to  be  apparently  insignificant,  yet  they  are  much  larger,  and 
form  a  more  evidently  important  part  of  it  in  many  of  the  lower  Mammalia ; 
though  still  presenting  the  same  general  aspect. — The  Auditory  ganglia  do 
not  form  distinct  lobes  or  projections  ;  but  are  lodged  in  the  substance  of  the 
Medulla  Oblongata.  Their  real  character  is  most  evident  in  certain  Fishes,  as  the 
Carp  ;  in  which  we  trace  the  Auditory  nerve  into  a  ganglionic  centre  as  distinct 
as  the  Optic  ganglion.  In  higher  animals,  however,  and  in  Man,  we  are  able 
to  trace  the  Auditory  nerve  into  a  small  mass  of  vesicular  matter,  which  lies 
on  each  side  of  the  Fourth  Ventricle ;  and  although  this  is  lodged  in  the  midst 


SENSORY  GANGLIA. CONSENSUAL  ACTIONS.  327 

of  parts  whose  function  is  altogether  different,  yet  there  seems  no  reason  for 
doubting  that  it  has  a  character  of  its  own,  and  that  it  is  really  the  ganglionic 

[Fig.  157. 


A  view  of  the  base  of  the  Cerebrum  and  Cerebellum,  together  with  their  nerves  ;  1,  anterior  extremity 
of  the  fissure  of  the  hemispheres  of  the  brain  ;  2,  posterior  extremity  of  the  same  fissure  ;  3,  the  anterior 
lobes  of  the  cerebrum;  4,  its  middle  lobe  ;  5,  the  fissure  of  Sylvius;  6,  the  posterior  lobe  of  the  cerebrum; 
7,  the  point  of  the  infundibulum  ;  8,  its  body;  9,  the  corpora  albicantia;  10,  cineritious  matter;  11,  the 
crura  cerebri ;  12,  the  pons  Varolii ;  13,  the  top  of  the  medulla  oblongata;  14.  posterior  prolongation  of 
the  pons  Varolii;  15,  middle  of  the  cerebellum  ;  16,  anterior  part  of  the  cerebellum ;  17,  its  posterior  part 
and  the  fissure  of  its  hemispheres  ;  18,  superior  part  of  the  medulla  spinalis  ;  19,  middle  fissure  of  the 
medulla  oblongata ;  20,  the  corpus  pyramidale  ;  21,  the  corpus  restiforme ;  22,  the  corpus  olivare  ;  23,  the 
olfactory  nerve  ;  24,  its  bulb  ;  25,  its  external  root ;  26,  its  middle  root ;  27,  its  internal  root ;  28,  the  op- 
tic nerve  beyond  the  chiasm;  29,  the  optic  nerve  before  the  chiasm;  30,  the  motor  oculi,  or  third  pair 
of  nerves  ;  31,  the  fourth  pair  or  pathetic  nerves  ;  32,  the  fifth  pair,  or  trigemini  nerves  ;  33,  the  sixth 
pair,  or  motor  externus  ;  34,  the  facial  nerve  ;  35,  the  auditory — the  two  making  the  seventh  pair  ;  36, 
37,  38,  the  eighth  pair  of  nerves.  (The  ninth  pair  is  not  here  seen.)] 

centre  of  the  Auditory  nerve. — In  like  manner,  we  may  probably  fix  upon  a 
collection  of  vesicular  matter,  imbedded  in  the  Medulla  Oblongata, — which  is 
considered  by  Stilling  to  be  the  nucleus  of  the  Glosso-pharyngeal  nerve,  and 
to  which  a  portion  of  the  sensory  root  of  the  Fifth  pair  may  be  traced, — as 
representing  the  Gustatory  ganglion. 

423.  At  the  base  of  the  Cerebral  Hemispheres,  we  find  two  other  large 
ganglionic  masses,  on  either  side  ;  into  which  all  the  fibres  appear  to  pass, 
which  connect  the  Hemispheres  with  the  Medulla  Oblongata.  These  are  the 
Thalami  Optici,  and  the  Corpora  Striata.  Now,  although  these  are  com- 
monly regarded  in  the  light  of  appendages,  merely,  to  the  Cerebral  Hemi- 
spheres, it  is  evident,  from  the  large  quantity  of  vesicular  matter  they  contain, 
that  they  have  an  independent  character  ;  and  that,  even  if  the  Cerebral  fibres 
simply  pass  through  them,  other  fibres  have  their  proper  ganglionic  centres 


328  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

in  them.  Such  an  idea  is  further  warranted  by  the  history  of  their  develop- 
ment ;  for  we  find,  in  the  Human  embryo  of  the  sixth  week,  a  distinct  vesi- 
cle for  the  Thalami  Optici,  interposed  between  the  vesicle  of  the  Corpora 
Quadrigemina,  and  that  which  gives  origin  to  the  Cerebral  Hemispheres ; 
whilst  the  Corpora  Striata  constitute  the  floor  of  the  cavity  or  ventricle,  which 
exists  in  the  latter. — Now,  as  already  pointed  out,  we  may  distinguish  in  the 
Medulla  Oblongata  and  Crura  Cerebri,  a  sensory  and  a  motor  tract;  by 
the  endowments  of  the  nerves  which  issue  from  them.  The  sensory  tract 
may  be  traced  upwards  from  the  Olivary  columns,  until  it  almost  entirely 
spreads  itself  through  the  substance  of  the  Thalamus.  Moreover,  the  Optic 
nerves,  and  the  peduncles  of  the  Olfactive,  may  be  shown  to  have  a  distinct 
connection  with  the  Thalami ;  the  former  by  the  direct  passage  of  a  portion 
of  their  roots  into  these  ganglia;  and  the  Blatter  through  the  medium  of  the 
Fornix.  Hence  we  may  fairly  regard  the  Thalami  Optici  as  the  chief  focus 
of  the  Sensory  nerves ;  and  more  especially  as  the  ganglionic  centre  of  the 
nerves  of  common  sensation,  which  ascend  to  it  from  the  Medulla  Oblongata 
and  Spinal  Cord.— On  the  other  hand,  the  Corpora  Striata  are  implanted  on 
the  motor  tracts  of  the  Crura  Cerebri,  which  descend  into  the  Pyramidal  co- 
lumns ;  and  their  connection  with  the  motor  function  is  very  generally  admit- 
ted, from  the  constancy  with  which  paralysis  is  observed  to  accompany  lesions 
of  these  bodies,  even  when  they  are  affected  to  a  very  trifling  extent. 

424.  The  Thalami  Optici,  and  the  Corpora  Striata,  as  is  well  known,  are 
very  closely  connected  with   each  other  by  commissural  fibres  ;  and,  if  the 
preceding  account  of  (heir  respective  offices  be  correct,  they  may  be  regarded 
as  having  much  the  same  relation  to  each  other,  as  that  which  exists  between 
the  posterior  and  anterior  peaks  of  vesicular  matter  in  the  Spinal  Cord  ;  the 
latter  issuing  motor  impulses  in  respondence  to  sensations  excited  through 
the  former.     They  are  also  closely  connected  with  other  ganglionic  masses 
in  their  neighbourhood,  such   as   the  locus  niger,  and  the  vesicular  matter  of 
the  pons;  which  again,  are  in  close  relation  with  the  vesicular  matter  of  the 
medulla  oblongata. — Altogether  it  is  very  evident,  that  an  extensive  tract  of 
ganglionic  matter  exists  at  the  base  of  the  Encephalon,  which  is  really  just  as 
distinct  from  either  the  Cerebrum  or  Cerebellum,  as  these   are  from  each 
other ;  and  we  have  next  to  inquire,  what  functions  are  to  be  assigned  to  it. 

425.  The  determination  of  these  may  seem  the  more  difficult,  as  it  is  im- 
possible to  make  any  satisfactory  experiments  upon  the  ganglionic  centres  in 
question,  by  isolating  them  from  the  Cerebral  Hemispheres  above,  and  from  the 
Medulla  Oblongata  and  Spinal  Cord  below.     But  the  evidence  derived  from 
Comparative   Anatomy  appears   to   be  in   this   case  particularly  clear;  and, 
rightly  considered,  seems  to  afford  us  nearly  all  the  information  we  require. 
In  the  series  of  "  experiments  prepared  for  us  by  nature,"  which  is  presented 
to  us   in  the   descending  scale  of  Animal  life,  we  witness  the  effects  of  the 
gradual  change  of  the  relative  development  of  the  Sensory  ganglia  and  Cerebral 
Hemispheres,  which  are  presented  to  us  in  the  Vertebrated  classes ;  and  the  results 
of  the  entire  "withdrawal  of  the  latter,  and  of  the  sole  operation  of  the  former, 
which  are  presented  in  the  higher  Invertebrata.     Tn  the  sketch  already  given 
of  the   Comparative  Anatomy  of  the  Encephalon  in  Vertebrata,  it  has  been 
shown  that  the  Sensory  ganglia  gradually  increase,  whilst  the  Cerebral  hemi- 
spheres as  regularly  diminish,  in  relative  size  and  importance,  as  we  descend  from 
the  higher  Mammalia  to  the  lower, — from  these  to  Birds, — thence  to  Reptiles, — 
from  these,  again,  to   the  higher  Fishes,  in  which  the"  aggregate  size  of  the 
Sensory  ganglia  equals   that  of  the  Cerebrum, — thence  to  the  lower  Fishes, 
in  which  the  size  of  the  Cerebral  lobes  is  no  greater  than  that  of  a  single  pair 
of  sensory  ganglia,  the  Optic,  and  frequently  even  inferior, — and  lastly,  to  the 
jZmphioxus  or  Lancelot,  the  lowest  Vertebrated  animal  of  which  we  have 


FUNCTIONS  OF  SENSORY  GANGLION.  329 

any  knowledge,  in  which  there  is  not  the  rudiment  of  a  Cerebrum,  the  En- 
cephalon  being  only  represented  by  a  single  ganglionic  mass,  which,  from  its 
connection  with  the  nerves  of  sense,  must  obviously  be  regarded  as  analogous 
to  the  congeries  of  ganglia  that  we  find  in  the  higher  forms  of  the  class. 

a.  It  has  been  supposed,  from  the  results  of  an  imperfect  examination  of  this  very  remarka- 
ble animal,  that  it  is  altogether  destitute  of  Encephalon;  and  that  it  possesses  no  ganglionic 
centre,  except  the  Spinal  Cord  and  Medulla  Oblongata.  The  researches  of  M.  de  Quatre- 
fages,  however,  indicate  that  the  most  anterior  of  the  ganglionic  enlargements  exhibited  by 
its  Cerebro-Spinal  axis,  is  of  a  more  special  character  than  the  rest;  uniting  in  itself  the 
characters  of  several  distinct  ganglionic  centres.  The  ganglionic  enlargements,  arranged  in 
a  linear  series,  which  altogether  represent  the  Spinal  Cord,  each  give  origin  to  a  single  pair 
of  nerves ;  but  the  cephalic  ganglion  is  the  centre  of  Jive  pairs.  Of  these,  the  first  pair  is 
distinctly  an  Optic  nerve;  being  exclusively  distributed  to  an  organ,  which  has  the  structure 
of  a  rudimentary  Eye,  though  lodged  within  the  dura  mater; — reminding  us,  in  its  situation, 
of  the  Auditory  apparatus  of  the  Gasteropod  Mollusks,  which  is  actually  imbedded  in  the 
posterior  part  of  the  Cephalic  ganglia.  The  second  pair  seems  to  correspond  in  its  distribu- 
tion with  the  Facial;  whilst  the  third  represents  the  Fifth  pair  and  the  Pneumogastric  con- 
jointly. The  fourth  and  fifth  pairs  are  distributed  to  the  fin-like  expansion,  which  forms  the 
margin  of  the  head  as  well  as  of  the  body;  and  seem  to  hold  the  same  relation  to  the  two 
preceding  pairs,  as  the  dorsal  branches  of  the  Spinal  nerves  bear  to  the  ventral, — or,  in  Man, 
the  posterior  to  the  anterior.  Hence  we  see  that  this  single  ganglion  is  made  up  of  at  least 
three  centres;  of  which  the  first  corresponds  to  the  Optic  ganglion  of  higher  Vertebrata; 
whilst  the  second  and  third  are  analogous  to  certain  parts  of  the  Medulla  Oblongata  in  im- 
mediate connection  with  them.  Moreover,  this  little  animal  possesses  an  organ  of  Smell, 
much  more  distinct  than  the  rudimentary  eye ;  and  although  its  connection  with  the  anterior 
part  of  the  cephalic  ganglion  has  not  yet  been  traced  (owing  to  the  extreme  minuteness  of 
the  parts,  and  the  difficulty  resulting  from  the  interposition  of  the  dura  mater,  which  is  in 
equally  close  contact  with  the  nervous  mass  which  it  incloses,  and  with  the  olfactive  organ 
which  abuts  upon  its  exterior),  there  can  be  little  doubt  that  such  a  connection  exists,  and 
that  the  Cephalic  mass  unites  within  itself  also  the  characters  of  an  Olfactive  ganglion.  But 
no  part  whatever  can  be  traced,  which  bears  any  resemblance  to  the  Cerebral  hemispheres ; 
and  as  these,  wherever  they  exist,  are  completely  isolated  from  the  Sensory  ganglia,  their 
absence  may  be  stated  as  an  almost  certain  fact.  Hence,  in  this  particular,  the  Amphioxus 
evidently  corresponds  with  the  Invertebrata ;  to  which  its  affinity  is  so  close  in  other  particu- 
lars, that  many  Naturalists  have  hesitated  to  assign  it  a  place  in  the  Vertebrated  series  at  all ; 
and,  as  will  be  seen  in  the  next  paragraph,  the  union  of  several  really  distinct  ganglionic 
centres  into  one  Cephalic  mass,  is  a  fact  which  is  capable  of  actual  demonstration.  (See 
the  Memoir  on  the  Branchiostoma  or  Amphioxus,  by  M.  de  Quatrefages,  in  the  Annales  des 
Sciences  Naturelles,  3me  Serie,  Zoologie,  torn,  iv.) 

426.  Descending  to  the  Invertebrated  series,  we  find  that,  except  in  a  few 
of  those  which  border  most  closely  upon  Vertebrata  (such,  for  example,  as 
the  Cuttle-Fish),  the  whole  Cephalic  mass  appears  to  be  made  up  of  ganglia, 
in  immediate  connection  with  the  nerves  of  sense.  These  may  appear  to 
form  but  a  single  pair ;  yet  they  are  in  reality  composed  of  several  pairs, 
fused  (as  it  were)  into  one  mass.  Of  this  we  may  judge  by  determining  the 
number  of  distinct  pairs  of  nerves  which  issue  from  them  ;  and  also  by  the 
investigation  of  the  history  of  their  development,  the  results  of  which  bear  a 
close  correspondence  with  those  obtained  in  the  preceding  method. 

a.  Thus,  Mr.  Newport  has  shown,  by  studying  the  development  of  the  head  in  certain 
species  of  the  class  Myriapoda,  that  it  is  originally  composed  of  no  less  than  eight  segments; 
each  having  its  peculiar  appendages;  and  each  possessing  (like  the  segments  of  the  body) 
its  own  pair  of  ganglionic  centres.  These  segments  afterwards  coalesce  into  two  portions ; 
of  which  the  most  anterior,  made  up  by  the  union  of  four  sub-segments,  is  termed  the  pro- 
per cephalic;  whilst  the  posterior,  also  made  up  of  four  sub-segments,  is  termed  the  basilar. 
The  four  pairs  of  ganglia  belonging  to  the  cephalic  portion  coalesce  into  the  one  pair  of 
cephalic  ganglia;  whilst  the  other  four  pairs  unite  to  form  the  first  sub-cesophageal  ganglia. — 
The  first  of  the  original  sub-segments  had,  as  its  proper  appendages,  the  antennae;  and  the 
ganglia  contained  in  it  were  evidently  the  proper  centres  of  the  antennal  nerves.  The 
second  had  no  movable  appendages,  but  contained  the  eyes ;  and  its  ganglia  were  evidently 
the  proper  centres  of  the  optic  nerves.  To  the  third  belonged  the  first  pair  of  jaws,  the 
maxillae;  and  to  the  fourth,  the  maxillary  palpi:  and  these  organs  derived  nerves  from  their 

28* 


330  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

own  ganglionic  centres,  belonging  to  their  respective  segments.  Now  as  all  these  nerves 
are  found  to  proceed,  in  the  adult  animal  from  the  single  pair  of  Cephalic  ganglia,  it  is 
obvious  that  these  combine  the  functions  of  the  ganglionic  centres  of  the  nerves  of  the 
antennae,  eyes,  and  palpi,  which  are  all  sensory  organs,  aa  well  as  of  the  maxillary  nerves, 
which  must  be  chiefly  motor.  And  it  is  equally  obvious,  that  there  is  nothing  in  such  an 
animal,  which  can  be  compared  to  a  pair  of  Cerebral  hemispheres;  since  all  the  ganglia 
of  the  original  segments  are  directly  connected  with  the  appendages  of  those  segments 
respectively. 

427.  It  is  further  to  be  remarked,  that  the  development  of  the  Cephalic 
ganglia  in  the  Invertebrata  always  bears  an  exact  proportion  to  the  develop- 
ment of  the  eyes ;    the  other  organs  of  special  sense  being   comparatively 
undeveloped ;  whilst  these,  in  all  the  higher  classes  at  least,  are  instruments 
of  great  perfection,  and  evidently  connected  most  intimately  with  the  direc- 
tion of  the  movements  of  the  animals.     Of  this  fact  we  have  a  remarkable 
illustration  in  the  history  of  the  metamorphoses  of  Insects ;  the  eyes  being 
almost  rudimentary,  and  the  Cephalic  ganglia  comparatively  small,  in  most 
Larvae ;  whilst  both  these  organs  attain  a  high  development  in  the  Imago,  to 
whose  actions  the  faculty  of  sight  is  essential. 

428.  Now  upon  making  a  similar  comparison  of  the  psychical  operations 
of  these  different  classes  of  animals,  we  are  led  to  perceive  that,  as  we  de- 
scend from  the  higher  to  the  lower  Vertebrata,  we  gradually  lose  the  indica- 
tions of  Intelligence  and  Will,  as  the  sources  of  the  movements  of  the  animal; 
whilst  we  see  a  corresponding  predominance  of  those,  which  are  commonly 
denominated   Instinctive,  and  which  are  performed  (as  it  would  appear)  in 
immediate  respondence  to  certain  sensations, — without  any  intentional  adapta- 
tion of  means  to  ends  on  the  part  of  the  individual,  although  such  adaptive- 
ness  doubtless  exists  in  the  actions  themselves,  being  a  consequence  of  the 
original  constitution  of  the  nervous  system  of  each  animal  performing  them. 
It  cannot  be  doubted  by  any  person  who  has  attentively  studied  the  charac- 
ters of  the  lower  animals,  that  many  of  them  possess  psychical  endowments, 
corresponding  with  those  which  we  term  the  intellectual  powers  and  moral 
feelings  in  Man;  but  in  proportion  as  these  are  undeveloped,  in  that  propor- 
tion is  the  animal  under  the  dominion  of  those  Instinctive  impulses,  which, 
so  far  as  its  own  consciousness  is  concerned,  may  be  designated  as  blind  and 
aimless,  but  which  are  ordained  by  the  Creator  for  its  protection  from  danger, 
and  for  the  supply  of  its  natural  wants.    The  same  may  be  said  of  the  Human 
infant,  or  of  the  Idiot,  in  whom  the  reasoning  powers  are  undeveloped.     In- 
stinctive actions  may  in  general  be  distinguished  from  those  which  are  the 
result  of  voluntary  power  guided  by  reason,  chiefly  by  the  two  following 
characters: — 1.  Although,  in  many  cases,  experience  is  required  to  give  the 
Will  command  over  the  muscles  concerned  in  its  operations,  no  experience 
or  education  is  required,  in  order  that  the  different  actions,  which  result  from 
an  Instinctive  impulse,  may  follow  one  another  with  unerring  precision.     2. 
These  actions  are  always  performed  by  the  same  species  of  animal,  nearly, 
if  not  exactly,  in  the  same  manner;  presenting  no  such  variation  in  the  means 
adapted  to  the  object  in  view,  and  admitting  of  no  such  improvement  in  the 
progress  of  life,  or  in  the  succession  of  ages,  as  we  observe  in  the  habits  of 
individual  men,  or  in  the  manners  and  customs  of  nations,  that  are  adapted  to 
the  attainment  of  any  particular  ends,  by  those  voluntary  efforts  which  are 
guided  by  reason.     The  fact,  too,  that  these  instinctive  actions  are  often  seen 
to  be  performed  under  circumstances  rendering  them  nugatory,  as   reason 
informs  us,  for  the  ends  which  they  are  to  accomplish — (as  when  the  Flesh-fly 
deposits  her  egg  on  the  Carrion-plant  instead  of  a  piece  of  meat,  or  when  the 
Hen  sits  on  a  pebble  instead  of  her  egg) — is  an  additional  proof,  that  the 
Instinctive  actions  of  animals  are  prompted,  like  the  consensual  movements 


SENSORY  GANGLIA. CONSENSUAL  ACTIONS.  331 

we  have  been  recently  inquiring  into,  by  an  impulse  which  immediately 
results  from  a  particular  sensation  being  felt,  and  not  by  anticipation  of  the 
effect  which  the  action  will  produce. 

429.  The  highest  development  of  the  purely  Instinctive  tendencies,  is  to  be 
found  in  the  class  of  Insects ;  and  above  all  in  the  order  Hymenoptera,  and  in 
that  of  Neuroptera,  which  is  nearly  allied  to  it.  It  is  in  this  division  of  the 
class,  that  we  find  the  highest  development  of  the  sensory  organs  and  of  the 
cephalic  ganglia,  and  the  most  active  powers  of  locomotion.  We  may  here 
trace  the  operations  of  Instinct,  with  the  least  possible  interference  of  Intelli- 
gence. It  is,  of  course,  impossible  to  draw  the  line  between  the  two  sources 
of  action,  with  complete  precision ;  but  we  observe,  in  the  habits  of  Bees  and 
other  social  Insects,  every  indication  of  the  absence  of  a  power  of  choice,  and 
of  the  entire  domination  of  instinctive  propensities  called  into  action  by  sen- 
sations. Thus,  although  Bees  display  the  greatest  art  in  the  construction  of 
their  habitations,  and  execute  a  variety  of  curious  contrivances,  beautifully 
adapted  to  variations  in  their  circumstances,  the  constancy  with  which  indi- 
viduals and  communities  will  act  alike  under  the  same  conditions,  appears  to 
preclude  the  idea  of  their  possessing  any  inherent  power  of  spontaneously  de- 
parting from  the  line  of  action,  to  which  they  are  tied  down  by  the  constitution 
of  their  Nervous  system.  We  do  not  find  one  individual  or  one  community 
clever,  and  another  stupid;  nor  do  we  ever  witness  a  disagreement,  or  any 
appearance  of  indecision,  as  to  the  course  of  action  to  be  pursued  by  the 
several  members  of  any  republic.*  For  a  Bee  to  be  destitute  of  its  peculiar 
tendency  to  build  at  certain  angles,  would  be  as  remarkable  as  for  a  Human 
being  to  be  destitute  of  the  desire  to  eat,  when  his  system  should  require 
food.  It  may  be  doubted,  on  the  other  hand,  whether  there  was  ever  a  case, 
in  which  an  Insect  of  any  kind  could  be  taught  to  recognize  any  one,  who  had 
been  in  the  habit  of  feeding  it;  or  to  show  any  other  unequivocal  indications 
of  intelligence. 

a.  Such  anecdotes  have  been  related  of  Spiders;  but  these  animals  are  the  highest  of  the 
Articulated  series,  having  many  points  of  approach  to  Vertebrata.     It  is  probable,  therefore, 
that  they  may  possess  the  rudiment  of  a  Cerebrum ;  a  similar  rudiment  making  its  appear- 
ance in  the  higher  Cephalopods,  which  occupy  a  corresponding  place  in  the  Molluscous 
series. 

b.  The  only  manifestation  of  educability,  which  the  Author  has  ever  noticed,  during  a 
pretty  long  familiarity  with  the  habits  of  Bees,  is  the  acquirement  of  a  power  of  distinguish- 
ing the  entrance  of  their  hive  from  that  of  others  around.    When  a  swarm  is  first  placed  in 
a  new  box,  and  the  Bees  have  gone  forth  in  search  of  food,  they  often  seem  puzzled  on  their 
return,  as  to  which  is  their  own  habitation ;  more  especially  if  there  be  several  hivesr  with 
similar  entrances,  in  one  bee-house ;  and  it  has  been  proposed  to  paint  these  entrances  of 
different  colours,  in  order  to  enable  the  Bee  to  distinguish  them  more  readily.     In  a  short 
time,  however,  even  without  such  aid,  the  Bees  are  seen  to  dart  from  a  considerable  height 
in  the  air,  directly  down  to  their  proper  entrances ;  showing  that  they  have  learned  to  dis- 
tinguish these,  by  a  memorial  power.    This  the  Author  has  observed  most  remarkably,  in  a 
case  in  which  a  hive  is  placed  in  the  drawing-room  of  a  house,  the  entrance  to  it  being  be- 
neath one  of  the  windows ;  the  adjoining  houses  have  windows  precisely  similar,  except  in 
the  absence  of  this  small  passage;  and  he  has  often  noticed  that,  when  a  new  stock  has  been 
placed  in  this  hive,  the  Bees  are  some  days  in  learning  the  exact  position  of  their  house,  con- 
siderably annoying  the  neighbours  by  flying  in  at  their  windows. 


*  The  community  of  Bees,  though  commonly  reputed  to  be  a  monarchy,  governed  by  a 
sovereign,  is  really  a  republic,  in  which  every  individual  performs  its  own  independent  part. 
The  function  of  the  queen  is  simply  that  of  breeding  ;  and  as  (among  the  Hive-Bees  at  least) 
she  is  the  only  female,  the  purpose  of  the  instinct, 'which  leads  the  workers  to  treat  her  with 
peculiar  attention,  is  very  obvious.  But  the  idea  that  she  directs  the  operations  of  the  hive, 
of  exerts  any  peculiar  control  over  the  ordinary  Bees,  is  entirely  destitute  of  foundation.  The 
actions  of  the  latter  all  tend  to  one  common  end ;  simply  because  they  are  performed  in  re- 
spondence  to  impulses,  which  all  alike  share. 


332  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

430.  Thus  the  analysis  of  such  of  the  actions  of  these  animals,  as  are  evi- 
dently of  a  higher  order  than  the  simply-reflex,  terminates  in  referring  them  to 
the  immediate  directing  influence  of  Sensations  ;  which,  being  received  by  the 
cephalic  ganglia  through  the  sensory  nerves,  excite  respondent  motor  impulses, 
which  are  propagated  to  the  various  muscles  of  the  body,  through  those  por- 
tions of  the  motor  trunks  that  issue  from  them.     As  the  term  Instinctive  has 
been  employed  in  a  great  variety  of  significations,  and  is  very  indefinite  in  its 
character,  we  may  more  appropriately  apply  the  designation  Consensual  to  the 
actions  of  this  group.    We  have  now  to  inquire,  whether  there  is  any  class  of 
movements  in  Man  and  the  higher  Vertebrata,  which  seems  to  possess  a  simi- 
lar character,  and  which  may  be  regarded  as  the  special  function  of  the  gangli- 
onic  centres  under  consideration. — By  far  the  larger  part  of  the  movements  of 
these  animals  (putting  aside  the  simply-reflex)  are  performed  under  the  direc- 
tion of  the  Intelligence  ;  to  which  the  sensations  are  communicated  ;  by  which 
a  reasoning  process   is  founded  upon  them  ;  and  from  which,  at  last,  issues 
that  mandate,  which  is  called  the  Will.     Consequently,  there  are  compara- 
tively few  movements,  in  the  adult  at  least,  which  can  be  clearly  distinguished 
as  neither  voluntary,  on  the  one  hand,  nor  reflex  on  the  other.     Such  actions, 
however,  do  exist ;  and  serve  to  show  that,  although  the  Instinctive  propensities 
are  in  great  measure  superseded  by  the  Intelligence,  they  may  still  operate 
independently  of  it.     As  examples  of  this  group,  we  may  advert  to  the  act  of 
Vomiting,  produced  by  various  causes  which  act  through  the  organs  of  sense; 
such  as  the  sight  of  a  loathsome  object,  a  disagreeable  smell,  or  a  nauseous 
taste.     The  excitement  of  the  act  of  Sneezing  by  a  dazzling  light,  is  another 
example  of  the  same  kind;  for  even  if  it  be  granted,  that  the  act  of  sneezing 
is  ordinarily  excited  through  the  reflex  system  alone  (which  is  by  no  means 
certain),  there  can  be  no  doubt  that  in  this  instance  it  cannot  be  brought  into 
play  without  a  sensation  actually  felt.    The  same  may  be  said  of  the  Laughter 
which  sometimes  involuntarily  bursts  forth,  at  the  provocation  of  some  sight 
or  sound,  to  which  no  distinct  ludicrous  idea  or  emotion  can  be  attached ;  and 
of  that  resulting  from  the  act  of  tickling,  in  which  case  it  is  most  certainly 
occasioned  by  the  sensation,  and  by  that  alone. 

431.  The  direct  influence  of  Sensations,  in  occasioning  and  governing  move- 
ments, which  are  neither  reflex  nor  voluntary,  is  most  remarkably  manifested 
in  many  phenomena  of  disease.     Thus  in  cases  of  excessive  irritation  of  the 
retina,  which  renders  the  eye  most  painfully  sensitive  to  even  a  feeble  amount 
of  light, — the  state  designated  as  photophobia, — the  eyelids  are  drawn  together 
spasmodically,  with  such  force  as  to  resist  very  powerful  efforts  to  open  them  ; 
and  if  they  be  forcibly  drawn  apart,  the  pupil  is  frequently  rolled  beneath  the 
upper  lid  (apparently  by  the  action  of  the  inferior  oblique  muscle),  much  fur- 
ther than  it  could  be  carried  by  a  voluntary  effort.    And  in  Pleuritis,  Pericar- 
ditis, and  other  painful  affections  of  the  parietes  of  the  chest,  we  may  observe 
the  usual  movements  of  the  ribs  to  be  very  much  abridged  ;  the  dependence  of 
this  abridgement  upon  the  painful  sensation  which  they  occasion,  being  most 
evident  in  those  instances  in  \vhich  the  affection  is  confined  to  one  side, — for 
there  is  then  a  marked  curtailment  in  its  movements,  whilst  those  of  the  other 
side  may  take  place  as  usual ;  a  difference  which  cannot  be  reflex,  and  which 
the  Will  cannot  imitate.     Again,  in  some  Convulsive  disorders,  we  observe 
that  the  paroxysms  are  excited  by  causes,  which  act  through  the  organs  of 
special  sense ;  thus  in  Hydrophobia,  we  observe  the  immediate  influence  of 
the  sight  or  the  sound  of  liquids,  and  of  the  slightest  currents  of  air ;  and  in 
many  Hysteric  subjects,  the  sight  of  a  paroxysm  in  another  individual  is  the 
most  certain  means  of  inducing  it  in  themselves. 

432.  The  results  of  experiments,  so  far  as  any  reliance  can  be  placed  upon 
them,  confirm  these  views ;  by  showing  that  any  disturbance  of  the  usual 


SENSORY  GANGLIA. CONSENSUAL  ACTIONS.  333 

actions  of  the  organs  of  sense,  and  of  the  nervous  centres  with  which  they  are 
connected,  in  animals  whose  movements  are  directly  governed  by  the  sensations 
received  through  these,  is  followed  by  abnormal  movements.  Thus  it  has 
been  ascertained  by  Flourens,  that  a  vertiginous  movement  may  be  induced  in 
pigeons,  by  simply  blindfolding  one  eye  ;  and  Longet  has  produced  the  same 
effect,  by  evacuating  the  humours  of  one  eye.  These  vertiginous  movements 
are  more  decided  and  prolonged,  when,  instead  of  blinding  one  eye,  one  of 
the  tubercula  quadrigemina  is  removed ;  the  animal  continuing  to  turn  itself 
towards  the  injured  side,  as  if  rotating  on  an  axis. — The  results  of  the  experi- 
ments of  M  Flourens  upon  the  portion  of  the  Auditory  nerve  proceeding  to 
the  Semi-circular  canals,  are  still  more  extraordinary.  Section  of  the  hori- 
zontal semi-circular  canal  in  Pigeons,  on  both  sides,  induces  a  rapid  jerking 
horizontal  movement  of  the  head,  from  side  to  side ;  and  a  tendency  to  turn 
to  one  side,  which  manifests  itself  whenever  the  animal  attempts  to  walk  for- 
wards. Section  of  a  vertical  canal,  whether  the  superior  or  inferior,  of  both 
sides,  is  followed  by  a  violent  vertical  movement  of  the  head.  And  section  of 
the  horizontal  and  vertical  canals  at  the  same  time,  causes  horizontal  and  ver- 
tical movements.  Section  of  either  canal  on  one  side  only,  is  followed  by  the 
same  effect  as  when  the  canal  is  divided  on  both  sides  ;  but  this  is  inferior  in 
intensity-  The  movements  continue  to  be  performed  during  several  months. 
In  Rabbits,  section  of  the  horizontal  canal  is  followed  by  the  same  movements, 
as  those  exhibited  by  pigeons ;  and  they  are  even  more  constant,  though  less 
violent.  Section  of  the  anterior  vertical  canal  causes  the  animal  to  make  con- 
tinued forward  somersets;  whilst  section  of  the  posterior  vertical  canal  occa- 
sions continual  backward  somersets.  The  movements  cease  when  the  animal 
is  in  repose ;  and  they  recommence  when  it  begins  to  move,  increasing  in 
violence  as  its  motion  is  more  rapid. — These  curious  results  are  supposed  by 
M.  Flourens  to  indicate,  that  the  nerve  supplying  the  semi-circular  canals  does 
not  minister  to  the  sense  of  hearing,  but  to  the  direction  of  the  movements  of 
the  animal:  but  they  are  fully  explained  upon  the  supposition  that  the  normal 
function  of  the  semi-circular  canals  is  to  indicate  to  the  animal  the  direction 
of  sounds,  and  that  its  movements  are  partly  determined  by  these;  so  that  a 
destruction  of  one  or  other  of  them  will  produce  an  irregularity  of  movement 
(resulting,  as  it  would  seem,  from  a  sort  of  giddiness  on  the  part  of  the  animal), 
just  as  when  one  of  the  eyes  of  a  bird  is  covered  or  destroyed,  as  in  the  ex- 
periments just  cited. 

433.  But  we  may  trace  the  influence  of  the  Sensory  ganglia,  not  merely  in 
their  direct  and  independent  operation  on  the  muscular  system,  but  also  in  the 
manner  in  which  they  participate  in  all  Voluntary  actions.  There  can  be  no 
doubt  that,  in  every  exertion  of  the  will  upon  the  muscular  system,  we  are 
guided  by  the  sensations  communicated  through  the  afferent  nerves,  which 
indicate  to  the  Sensorium  the  state  of  the  muscle.  Many  interesting  cases 
are  on  record,  which  show  the  necessity  of  this  Muscular  Sense,  for  determin- 
ing voluntary  contraction  of  the  muscle.  Thus,  Sir  C.  Bell  (who  first  promi- 
nently directed  attention  to  this  class  of  facts,  under  the  designation  of  the 
Nervous  Circle),  mentions  an  instance  of  a  woman,  who  was  deprived  of  it  in 
her  arms,  without  losing  the  motor  power;  and  who  stated,  that  she  could  not 
sustain  anything  in  her  hands  (not  even  her  child),  by  the  strongest  effort  of 
her  will,  unless  she  kept  her  eyes  constantly  fixed  upon  it;  the  muscles  losing 
their  power,  and  the  hands  dropping  the  object,  as  soon  as  the  eyes  were 
withdrawn  from  it.  Here  the  employment  of  the  visual  sense  supplied  the 
deficiency  of  the  muscular  ;  but  instead  of  being  inseparably  connected,  as  the 
latter  is  in  the  state  of  health,  with  the  action  of  the  muscle,  the  former  could 
be  only  brought  to  bear  by  an  effort  of  the  will ;  and  the  sustaining  power  was 
therefore  dependent,  not  upon  the  immediate  influence  of  the  will  upon  the 


334  FUNCTIONS  or  THE  NERVOUS  SYSTEM. 

muscle,  but  upon  the  voluntary  direction  of  the  Sight  towards  the  object  to  be 
supported.  Again,  in  the  production  of  vocal  sounds,  the  nice  adjustment  of 
the  muscles  of  the  larynx,  which  is  requisite  to  produce  determinate  tones, 
can  only  be  learned  in  the  first  instance  under  the  guidance  of  the  sensation 
of  the  sounds  produced,  and  can  only  be  effected  by  an  act  of  the  will,  in 
obedience  to  a  mental  conception  (a  sort  of  inward  sensation)  of  the  tone  to 
be  uttered, — which  conception  cannot  be  formed,  unless  the  sense  of  hearing 
has  previously  brought  similar  tones  to  the  mind.  Hence  it  is,  that  persons 
who  are  born  deaf,  are  also  dumb.  They  may  have  no  malformation  of  the 
organs  of  speech ;  but  they  are  incapable  of  uttering  distinct  vocal  sounds  or 
musical  tones,  because  they  have  not  the  guiding  conception,  or  recalled  sen- 
sation, of  the  nature  of  these.  By  long  training,  and  by  efforts  directed  by  the 
muscular  sense  of  the  larynx  itself,  some  persons  thus  circumstanced  have 
acquired  the  power  of  speech ;  but  the  want  of  a  sufficiently  definite  control 
over  the  vocal  muscles,  is  always  very  evident  in  their  use  of  the  organ. 

434.  The  conjoint  movements  of  the  two   eyes,  which   concur  to  direct 
their  axes  towards  the  same  object,  are  among  the  most  interesting  of  these 
actions,  in  which  Volition  and  Consensual  action  are  alike  concerned ;  and 
they  afford   an   excellent  illustration  of  the  necessity  for  guiding  sensations, 
to  determine  the  actions  of  muscles.     The   sensations,  however,  are   not  so 
much  those  of  the  muscles  themselves,  as  those  received  through   the  visual 
organ;  but  the  former  appear  capable  of  continuing  to  guide  the  harmonious 
movements  of  the  eyeballs,  when   the  sense  of  sight  has  been  lost.     It  is  a 
striking  peculiarity  of  these   movements,  that,  in  the  majority  of  them,  two 
muscles  or  combinations   of  muscles  of  opposite   action  are  in  operation  at 
once ;  thus,  when  the  eyes  are  made  to  rotate  in  a  horizontal  plane,  the  in- 
ternal rectus  of  one  side  acts  with  the  external  rectus  of  the  other.     In  most 
other  cases,  there  is  a  difficulty  in  performing  two  opposite   movements,  on 
the  two  sides  at  the  same  time.     Thus,  if  we  move  the  right  hand  as  if  wind- 
ing on  a  reel,  and  afterwards  make  the  left  hand  revolve  in  a  contrary  direc- 
tion, no  difficulty  is  experienced;  but  if  we  attempt  to  move  the  two  at  the 
same  time  in  contrary  directions,  we  shall  find  it  almost  impossible. — As  the 
Consensual  movements  of  the  Eyes  are  of  sufficient  interest  and  importance, 
to  require  a  detailed   consideration,  they  will  be  examined  more  fully  at  the 
close  of  the  present  section  (§§  450 — 456). 

435.  If  the  preceding  views  be  correct,  we  may  regard  the  series  of  Gan- 
glionic  centres  which  have  been  enumerated  (§§  422,  423),  as  constituting  the 
real   Sensorium ;  each  ganglion  having  the  power  of  cummunicating  to  the 
mind  the  impressions  derived  from  the  organ,  with  which  it  is  connected,  and 
of  exciting  automatic  muscular  movements  in  respondence  to  these  sensations. 
If  this  position  be  denied,  we  must  either  refuse  the  attribute  of  consciousness 
to  those  animals,  which  possess  no  other  encephalic  centres  than  these ;  or 
we  must  believe  that  the  addition  of  the  Cerebral  hemispheres,  in  the  Verte- 
brated  series,  alters  the  endowments  of  the  Sensory  ganglia, — an  idea  which 
is  contrary  to  all  analogy.     So  far  as  the  results  of  experiments  can  be  relied 
on,  they  afford  a  corroboration  of  these  views.     The  degree  in  which  animals 
high  in  the  scale  of  organization  can  perform   the   functions  of  life,  without 
any  other  centre  of  action   than  the  Ganglia  of  Special  sense,  the   Medulla 
Oblongata/and  the  Cerebellum,  appears  extraordinary  to  those  who  are  accus- 
tomed to  regard  the  Cerebral  Hemispheres  as  the  centre  of  all  energy.     From 
the  experiments  of  Flourens,  Hertwig,  Magendie,  and  others,  it  appears  that 
not  only  Reptiles,  but  Birds  and  Mammalia,  may  survive  for  many  weeks  or 
months  (if  their  physical  wants  be  duly  supplied)   after  the  removal  of  the 
whole   Cerebrum.     It  is   difficult  to   substantiate   the  existence  in  them  of 
actual  Sensation;  but  some  of  their  movements  appear  to  be  of  a  higher  kind 


SENSORY  GANGLIA. CONSENSUAL  AND  EMOTIONAL  ACTIONS.  335 

than  those  resulting  from  mere  Reflex  action.  One  of  the  most  remarkable 
phenomena  exhibited  by  such  a  being,  is  the  power  of  maintaining  its  equili- 
brium, which  could  scarcely  exist  without  consciousness.  If  it  be  laid  upon 
the  back,  it  rises  again;  if  pushed,  it  walks.  If  a  Bird  thus  mutilated  be 
thrown  into  the  air,  it  flies;  if  a  Frog  be  touched,  it  leaps.  It  swallows  food 
and  liquid,  when  they  are  placed  in  its  mouth;  and  the  digestive  operations, 
the  acts  of  excretion,  &c.,  take  place  as  usual.  In  the  case  of  a  Pigeon  ex- 
perimented on  by  Malacorps,  which  is  recorded  by  Magendie,  there  appears 
sufficient  proof  of  the  persistence  of  a  certain  amount  of  sensation.  Although 
the  animal  was  not  affected  by  a  strong  light  suddenly  made  to  fall  upon  its 
eyes,  it  was  accustomed,  when  confined  in  a  darkened  or  partially-illuminated 
room,  to  seek  out  the  light  parts ;  and  it  avoided  objects  that  lay  in  its  way. 
In  the  same  manner,  it  did  not  seem  to  be  affected  by  sudden  noises;  but  at 
night,  when  it  slept  with  closed  eyes  and  its  head  under  its  wing,  it  would 
raise  its  head  in  a  remarkable  manner,  and  open  its  eyes,  on  the  slightest 
noise ;  speeflily  relapsing  into  a  state  of  complete  unconsciousness.  Its 
principal  occupation  was  to  prune  its  feathers  and  scratch  itself. — The  con- 
dition of  such  a  being  seems  to  resemble  that  of  a  Man,  who  is  in  a  slumber 
sufficiently  deep  to  lose  all  distinct  perception  of  external  objects,  but  who  is 
yet  conscious  of  sensations,  as  appears  from  the  movements  occasioned  by 
light  or  by  sounds,  or  from  those  which  he  executes  to  withdraw  the  body 
from  an  uneasy  position.* 

436.  Among  the  ganglia  of  special  sensation,  the  functions  of  the  Optic 
Lobes,  or   Corpora  Quadrigemina,  have  been  chiefly  examined.     The  re- 
searches of  Flourens  and  Hertwig  have   shown,  that  their  connection  with 
the  visual  function,  which  might  be  inferred  from  their  anatomical  relations, 
is   substantiated  by  experiment.     The  partial  loss  of  the  ganglion   on   one 
side  produces  partial  loss  of  power  and  temporary  blindness  on  the  opposite 
side  of  the  body,  without  necessarily  destroying  the  mobility  of  the  pupil; 
but  the  removal  of  a  larger  portion,  or  complete  extirpation  of  it,  occasions 
permanent  blindness  and  immobility  of  the  pupil,  with  temporary  muscular 
weakness,  on  the  opposite  side.     This  temporary  disorder  of  the  muscular 
system  sometimes  manifests  itself  (as  already  stated)  in  a  tendency  to  move  on 
the  axis,  as  if  the  animal  were  giddy.     No  disturbance  of  consciousness  ap- 
pears to  be  produced;  and  Hertwig  states  that  he  never  witnessed  the  con- 
vulsions, which  Flourens  mentions  as  a  consequence  of  the  operation,  and 
which  were  probably  occasioned  by  his  incision   having   been  carried   too 
deeply.     These  results  are  confirmed  by  pathological  phenomena  in  Man; 
for  there  are  many  instances  on  record,  in  which  blindness  has  been  one  of 
the  consequences  of  diseased  alterations  in  one   or  both   tubercles  ;  and  in 
some  of  the  cases,  in  which  the  lesion  extended  to  parts  seated  beneath  the 
tubercles,  disturbed  movements  were  observed. — No  definite  conclusions  can 
be  drawn,  either  from  experiment  or  from  pathological  observation,  in  regard 
to  the   functions  of  the   Thalami  Optici   and  Corpora  Striata;   but   there  is 
nothing  in  these  sources  of  information  to  oppose  the  views  already  offered, 
which  are  based  on  other  foundations. 

437.  Emotional  Actions. — There  appears  strong  reason  for  regarding  the 
Ganglionic  tract,  which  is  the  instrument  of  Consensual  actions,  as  the  imme- 
diate centre  also  of  those  movements  which  directly  result  from   the  excite- 
ment of  the  Emotions.     Several  considerations  tend'  to  establish  this  position. 

*  It  must  not  be  forgotten  that,  in  such  experiments,  the  severity  of  the  operation  will  of 
itself  occasion  a  suspension  or  disturbance  of  the  functions  of  parts  that  remain  ;  so  that  the 
loss  of  a  power  must  not  be  at  once  inferred  from  the  absence  of  its  manifestations.  But  the 
persistence  of  a  power,  after  the  removal  of  a  particular  organ,  is  a  clear  proof  that  it  cannot 
be  the  peculiar  attribute  of  that  organ. 


336  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

In  the  first  place,  that  the  channel  through  which  the  direct  impulses  of  the 
Emotions  are  conveyed  to  the  Muscles,  is  not  the  same  with  that  which  con- 
veys to  them  the  mandates  of  the  Will,  appears  sufficiently  established  by 
Pathological  observation ;  since  cases  of  paralysis  not  unfrequently  occur,  in 
which  the  muscles  are  obedient  to  an  emotional  impulse,  though  the  will  exerts 
no  power  over  them ;  whilst,  on  the  other  hand,  the  will  may  have  its  due 
influence,  and  yet  the  emotional  state  cannot  manifest  itself.  This  is  espe- 
cially remarkable  in  the  different  forms  of  paralysis  of  the  Facial  nerve  ;  since 
the  facial  muscles  manifest  the  ordinary  influence  of  the  Emotions,  more  evi- 
dently than  any  others.  But  it  is  not,  however,  confined  to  them;  thus,  for 
example,  the  arm  of  a  man,  which  no  effort  of  his  will  could  move,  has  been 
seen  to  be  violently  agitated  at  the  sight  of  a  friend.  Dr.  M.  Hall  has  inferred 
from  cases  of  this  kind,  that  the  Spinal  system  of  nerves  constitutes  the  chan- 
nel of  the  Emotional  actions;  but  all  which  is  proved  by  them  is,  that  these 
are  not  effected  through  the  same  agency  with  the  Volitional ;  and  the  idea 
that  they  are  of  the  same  character  with  Reflex  actions  is  distinctly  negatived 
by  the  fact,  that  in  a  great  majority  of  instances,  they  are  excited  through  the 
organs  of  special  sense,  and  that  consciousness  is  a  distinct  element  in  the 
series  of  changes  which  ends  in  their  performance.  These  facts  would  lead 
us  to  infer,  that  the  Emotional  actions  are  dependent  on  a  set  of  centres,  in- 
termediate between  the  Cerebrum  and  the  Spinal  Cord ;  a  position  which  is 
precisely  that  of  the  ganglionic  tract  under  consideration. — In  the  next  place 
it  may  be  remarked,  that  the  Emotions  are  so  closely  linked  with  Sensations, 
as  to  be  regarded  by  many  Metaphysicians  as  almost  identical  with  them  ;  and 
this  connection  is  universally  recognized  in  the  term  Feelings  popularly  ap- 
plied to  both.  Like  the  Instinctive  tendencies  of  Animals,  the  Emotional 
states  follow  directly  and  necessarily  upon  Sensations,  without  any  interven- 
ing process  of  ratiocination  ;  and  there  is  such  a  marked  correspondence  in 
the'character  of  the  actions,  which  flow  from  these  sources,  as  to  point  to  the 
conclusion  of  the  identity  of  the  conditions  on  which  they  immediately  de- 
pend. Of  this,  an  example  will  be  presently  given.  We  have  seen  that  the 
Sensory  ganglia  must  necessarily  be  regarded  as  the  instruments  of  the  In- 
stinctive actions ;  and  a  probable  inference  may  therefore  be  drawn  from  this 
fact,  in  regard  to  their  relation  to  those  which  (in  Man)  are  designated  as 
Emotional.* — A  third  argument  in  support  of  this  view  may  be  drawn  from 
the  fact,  of  the  very  close  connection  of  this  division  of  the  nervous  centres, 
with  the  nervous  trunks,  through  which  the  emotional  states  are  excited,  and 
the  respondent  muscular  actions  are  stimulated.  For  the  Sensory  ganglia  re- 
ceive all  those  nerves,  which  communicate  the  Sensations  through  whose 
immediate  agency  the  Emotion  is  excited ;  and  the  nerves  of  the  Orbit,  the 
Face,  and  the  Respiratory  organs, — those  most  concerned  in  producing  the 
movements,  by  which  the  emotions  are  expressed  or  manifested, — arise  in 
their  immediate  proximity.  It  is  chiefly  through  these  nerves,  too,  that  the 

*  It  seems  by  no  means  certain,  that  we  are  always  to  attribute  to  the  lower  animals  the 
Emotions  which  we  ourselves  feel,  because  they  perform  movements  analogous  to  those  by 
•which  we  ordinarily  express  them:  for  the  movements  may  be  directly  excited  by  the  Sen- 
sations, without  the  intervention  of  the  Emotion ;  just  as  in  ourselves,  involuntary  laughter 
is  occasioned  by  tickling,  although  no  ludicrous  emotion  be  excited  ;  or  as  Vomiting  results 
from  the  sight  of  a  loathsome  object,  rather  in  respondence  to  the  sensation  of  nausea,  than 
to  the  emotion  of  disgust  which  it  concurrently  excites.  We  might,  on  equally  valid  grounds, 
assert,  that  the  Bee  goes  through  a  process  of  mathematical  ratiocination,  before  it  commences 
the  construction  of  its  cell.  The  purpose  of  the  Emotion,  in  animals  possessed  of  Intelligence, 
may  be  rather  to  act  upwards  upon  it  •  and,  although  closely  connected  with  the  sensation 
which  excites  it ;  it  may  be  no  more  necessary  to  the  resulting  muscular  movement,  than 
sensation  is  to  reflex  action. — On  this  view,  all  actions  of  the  directly  Emotional  character 
would  be  in  reality  purely  Consensual. 


EMOTIONAL  AND  INSTINCTIVE  ACTIONS.  337 

abnormal  movements  are  effected,  in  those  disorders  of  the  Nervous  centres, 
which  may  be  most  distinctly  referred  to  the  Emotional  system ;  such  as 
Chorea  and  Hysteria. 

438.  The  correspondence  between  the  purely  Emotional  actions  in  Man, 
and  those  actions  in  the  lower  animals  to  which  we  give  the  name  of  Instinc- 
tive, may  be  made  evident  by  a  very  simple  illustration.     The  Cuttle-fish  is 
well  known  to  discharge  its  ink,  when  pursued,  and  to  tinge  the  water  around 
with  a  colour  so  deep,  as  to  enable  it  to  escape  under  the  cloud  thus  formed. 
Now  it  is  not  to  be  supposed,  that  the  Cuttle-fish  has  any  notion  of  the  pur- 
pose which  this  act  will  serve ;  since  its  constancy  and  uniformity,  and  the 
provision  for  its  performance  immediately  on  the  emersion  of  the  young  ani- 
mal from  the  egg,  forbid  our  regarding  it  as  the  result  of  any  act  of  reasoning. 
Further,  the  ink  is  an  excretion  which  corresponds  to  the  urine  (having  been 
found  to  contain  urea) ;  and  every  one  knows  how  strong  an  impulse  to  dis- 
charge this,  is  frequently  caused  by  mental  emotion.     The  same  may  be  said 
of  the  strongly  odorous  secretions  possessed  by  many  Mammalia,  which  are 
discharged  under  similar  circumstances,  and  evidently  with^  the  same  object; 
though  of  that  object,  the   animal  itself  be  not  conscious.     The  emotion  of 
fear  involuntarily  opens  the  sphincters,  and  causes  the  contraction  of  the  recep- 
tacle, in  one  case  as  in  the  other ;  and  the  great  difference  between  the  condi- 
tion of  Man,  and  that  of  the  lower  animals,  in  this  respect,  is  simply  that,  in 
the  former,  the  purely  Emotional  or  Instinctive  actions  are  few  in  comparison 
with  the  whole,  whilst  in  the  latter  they  constitute  by  far  the  largest  part;  and 
also  that  Man  has  much  greater  power  of  controlling  these  actions  by  a  volun- 
tary effort,  than  that  which  the  lower  animals  possess,  although  even  he  is  not 
unfrequently  compelled  by  the  strength  of  his   Emotions  to  act  against  his 
Will.-    Thus,  we  see  or  hear  something  ludicrous,  which  involuntarily  pro- 
duces laughter,  although  we  may  have  the  strongest  motives  for  desiring  to 
restrain  it. 

a.  It  is  a  very  interesting  question,  how  far  actions  at  first  performed  voluntarily  by  Man, 
may  by  habit  cease  to  require  an  effort  of  the  Will;  being  prompted,  like  the  movements  of 
the  Consensual  class,  by  the  direct  impulse  of  sensations.  Thus  we  all  know  that,  in  walking 
along  an  accustomed  road,  we  frequently  occupy  our  minds  with  some  continuous  train  of 
thought,  and  yet  our  limbs  continue  to  move  under  us  with  regularity,  until  we  are  surprised 
by  finding  ourselves  at  the  place  of  our  destination,  or  perhaps  at  some  other  which  we  had 
not  intended  to  visit,  but  to  which  habit  has  conducted  us.  Or  we  may  read  aloud  for  a 
long  time,  without  having  in  the  least  degree  comprehended  the  meaning  of  the  words  we 
have  uttered ;  our  attention  having  been  closely  engaged  by  some  engrossing  thoughts  or 
feelings  within.  Or  a  Musician  may  play  a  well-known  piece  of  music,  whilst  carrying  on 
an  animated  conversation ; — the  Author  has  known  a  skilful  performer  who  could  play  at 
sight  whilst  thus  occupied.  Now  in  such  a  case  it  would  be  said  by  some  Metaphysicians 
(acknowledging,  as  most  do,  that  the  mind  cannot  will  two  different  things  at  the  same  time) 
that  the  Volition  is  in  a  sort  of  vibratory  condition  between  the  two  sets  of  actions,  now 
prompting  one,  and  now  the  other!  But  it  would  seem  much  more  conformable  to  the 
analogy  afforded  by  other  psychical  phenomena,  to  refer  the  habitual  series  of  actions  to  the 
same  operation  of  the  Nervous  System  with  the  Instinctive ;  and  perhaps  the  term  Automatic 
may  be  fairly  applied  to  the  whole  of  this  group.  It  is  well  known  that  in  cases  of  severe 
injury  of  the  brain,  in  which  Intelligence  and  Will  seem  completely  in  abeyance,  habitual 
actions  may  be  often  excited.  Thus,  Dr.  Perceval,  in  his  Essay  on  habit,  mentions  the  case 
of  a  snuff-taking  Countess,  in  whom,  when  seized  with  apoplexy,  irritation  of  the  -nose  with 
a  feather  produced  contraction  of  the  fore-finger  and  thumb  of  the  right  Jtiand;  and  Mr. 
Traverse  has  recorded  a  similar  fact  in  the  case  of  a  boy,  who,  when  apparently  insensible 
from  depressed  fracture  of  the  skull,  assisted  in  removing  his  clothes,  preparatorily  to  the 
required  operation. 

439.  The  purely  Emotional  actions  are  not  always  directly  excited,  however, 
by  external  sensations ;  for  they  may  result  from  the  operations  of  the  Mind 
itself.     Thus  involuntary  laughter  may  result  from  a  ludicrous  idea,  called  up 
by  some  train  of  association,  and  having  no  obvious  connection  with  the  sen- 

29 


338  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

sation  which  first  set  this  process  in  operation;  and  the  various  movements 
of  the  face  and  person,  by  which  Actors  endeavour  to  express  strong  Emotions, 
are  only  effectual  in  conveying  their  meaning,  when  they  result  from  the  actual 
working  of  the  emotions  in  the  mind  of  the  performer,  who  has,  by  an  effort 
of  the  will,  identified  himself  (so  to  speak)  with  the  character  he  personates. 
A  still  more  remarkable  case  is  that,  in  which  paroxysms  of  Hysterical  con- 
vulsion, in  themselves  beyond  the  power  of  the  Will  to  excite  or  to  control, 
are  brought  on  by  a  voluntary  effort;  which  seems  to  act  by  "getting  up,"  so 
to  speak,  the  state  of  feeling,  which  is  the  immediate  cause  of  the  disordered 
movements.  In  all  these  instances,  and  others  of  like  nature,  it  would  seem 
as  if  the  agency  of  the  Cerebrum  produced  the  same  condition  in  the  Sensory 
ganglia  and  their  motor  fibres,  as  that  which  is  more  directly  excited  by  sen- 
sations received  through  their  own  afferent  nerves.  It  may  be  reasonably 
surmised,  that  the  Sensory  ganglia,  like  the  Cephalic  ganglia  which  are  the 
instruments  of  the  Instinctive  actions  of  the  lower  animals,  can  only  be  excited 
to  action  by  stimuli  immediately  operating  upon  them ;  but  that  these  stimuli 
may  be  either  Sensations  directly  originating  in  external  objects,  or  Concep- 
tions resulting  from  the  remembrance  of  those  objects,  of  which  there  is  strong 
reason  to  believe  that  the  Cerebrum  is  the  storehouse. 

440.  The  Emotions  are  concerned  in  Man,  however,  in  many  actions,  which 
are  in  themselves  strictly  voluntary.  Unless  they  be  strongly  excited,  so  as 
to  get  the  better  of  the  Will,  they  do  not  operate  directly  through  the  nervous 
trunks,  but  are  subservient  to  the  intellectual  operations;  to  which  they  supply 
materials,  or  motives.  Thus,  of  two  individuals,  with  differently  constituted 
minds,  one  shall  judge  of  everything  through  the  medium  of  a  gloomy  morose 
temper,  which,  like  a  darkened  glass,  represents  to  his  judgment  the  whole 
world  in  league  to  injure  him ;  and  all  his  determinations,  being  based  upon 
this  erroneous  view,  exhibit  the  indications  of  it  in  his  actions ;  which  are 
themselves,  nevertheless,  of  an  entirely  voluntary  character.  On  the  other 
hand,  a  person  of  a  cheerful,  benevolent  disposition,  looks  at  the  world  around 
as  through  a  Claude  Lorraine  glass,  seeing  everything  in  its  brightest  and 
sunniest  aspect;  and,  with  intellectual  faculties  precisely  similar  to  those  of 
the  former  individual,  he  will  come  to  opposite  conclusions ;  because  the 
materials,  which  form  the  basis  of  his  judgment,  are  submitted  to  it  in  a  very 
different  condition.  Various  forms  of  Moral  Insanity  exhibit  the  same  con- 
trast in  a  yet  more  striking  light.  We  not  unfrequently  meet  with  individuals, 
still  holding  their  place  in  society,  who  are  accustomed  to  act  so  much  upon 
feeling,  and  to  be  so  little  guided  by  reason,  as  to  be  scarcely  regarded  as 
sane ;  and  a  very  little  exaggeration  of  such  a  tendency  causes  the  actions  to 
be  so  injurious  to  the  individual  himself,  or  to  those  around  him,  that  restraint 
is  required,  although  the  intellect  is  in  no  way  disordered,  nor  are  any  of  the 
feelings  perverted.  Not  unfrequently  we  may  observe  similar  inconsistencies 
resulting  from  the  habitual  indulgence  of  one  particular  feeling,  or  a  morbid 
exaggeration  of  it.  The  mother  who,  through  weakness  of  will,  yields  to  her 
instinctive  fondness  for  her  offspring,  in  allowing  it  gratifications  which  she 
knows  to  be  injurious  to  it,  is  placing  herself  below  the  level  of  many  less 
gifted  beings.  The  habit  of  yielding  to  a  natural  infirmity  of  temper  often 
leads  into  paroxysms  of  ungovernable  rage,  which,  in  their  turn,  pass  into  a 
state  of  maniacal  excitement.  It  is  not  unfrequently  seen,  that  a  delusion  of 
the  intellect  (constituting  what  is  commonly  known  as  Monomania)  has  in 
reality  resulted  from  a  disordered  state  of  the  feelings,  which  have  represented 
every  occurrence  in  a  wrong  light  to  the  mind  of  the  individual.  All  such 
conditions  are  of  extreme  interest,  when  compared  with  those  which  are  met 
with  amongst  idiots,  and  animals  enjoying  a  much  lower  degree  of  intelligence : 
for  the  result  is  much  the  same,  in  whatever  way  the  balance  between  the 


NERVES  OF  SPECIAL  SENSE. OLFACTIVE.  339 

feelings  and  the  judgment  (which  is  so  beautifully  adjusted  in  the  well-ordered 
mind  of  Man)  is  disturbed ;  whether  by  a  diminution  of  the  intelligence,  or 
by  an  exaltation  of  the  feelings. — These  views  will  probably  be  found  correct, 
whatever  be  the  truth  of  the  speculation  with  which  they  have  been  here  con- 
nected, as  to  the  part  of  the  Nervous  system  concerned  in  the  performance  of 
the  purely  Emotional  actions.  That  their  channel  is  alike  distinct,  however, 
from  that  of  the  Voluntary  movements,  and  from  that  of  Reflex  operations, 
must  be  apparent  to  any  one  who  fairly  weighs  the  evidence. 

441.  Nerves  connected  with  the  Sensory  Ganglia. — That  the  First  pair, 
or  Olfactory  nerves,  minister  to  the   sense   of  smell,  has  long  been  known, 
yet  it  could  not  be  predicted  without  experimental  inquiry,  that  it  is  not  a 
conductor  of  the  impressions  which  produce  ordinary  sensation;  nor  that  it 
is  destitute  of  all  power  of  exciting  muscular  movement,  either  by  direct  or 
reflex  action.    Anatomical  examination  of  the  distribution  of  this  nerve,  proves 
that  it   is  not  one  which  directly  conveys   motor  influence  to  any  muscles ; 
since  all  its  branches  are  distributed  to  the  membrane  lining  the  nasal  cavity. 
Experimental  inquiry  leads  to  the  same  result ;  for  no  irritation  of  the  pedun- 
cles or  branches  excites  any  muscular  movement.     Further,  no  irritation  of 
any  part  of  this  nerve  excites  reflex  actions  through  other  nerves.     Again,  it 
is  not  a  nerve  of  common  sensation  ;  for  animals  exhibit  no  sign  of  pain, 
when  it  is  subjected  to  any  kind  of  irritation.     Neither  the  division  of  the 
nerve,  nor  the  destruction  of  the   olfactive  ganglia,  seems   to  inconvenience 
them  materially.     They  take  their  food,  move  with  their  accustomed  agility, 
and  exhibit  the  usual  appetites  of  their  kind.    The  common  sensibility  of  the 
parts  contained  in  the  olfactive  organ  is  in  no   degree  impaired,  as  is  shown 
by  the  effect  of  irritating  vapours ;  but  the  animals  are  destitute  of  the  sense 
of  smell,  as  is  shown  by  the  way  in  which  these  vapours  affect  them.     At 
first  they  appear  indifferent  to  their  presence,  and  then  suddenly  and  vehe- 
mently avoid  them,  as  soon  as  the  Schneiderian  membrane  becomes  irritated. 
Moreover,  if  two  dogs,  with  the   eyes   bandaged,   one  having  the   olfactory 
nerves    and  ganglia  sound,  and   the  other  having  had  them  destroyed,  are 
brought  into  the  neighbourhood  of  the  dead  body  of  an  animal,  the  former 
will  examine  it  by  its  smell ;  whilst  the  latter,  even  if  he  touches  it,  pays  no 
attention  to  it.     This  experiment  Valentin  states  that  he  has  repeated  several 
times,   and  always   with  the   same  results.     Further,  common  observation 
shows  that  sensibility  to  irritants,  such  as   snuff,  and  acuteness  of  the  power 
of  smell,  bear  no   constant  proportion  to   one  another  ;  and  there   is  ample 
pathological  evidence,  that  the  want  of  this   sense  is  connected  with  some 
morbid  condition  of  the  olfactory  nerves  or  ganglia. — It  is  well  known  that 
Magendie  has  maintained,  that  the  Fifth  pair  in  some  way  furnishes  conditions 
requisite  for  the  enjoyment  of  the  sense  of  smell;  asserting  that,  when  it  is 
cut,  the  animal  is  deprived  of  this.     But  his  experiments  were  made  with  ir- 
ritating vapours,  which  excite  sternutation  or  other  violent  muscular  actions, 
not  through  the  Olfactory  nerve,  but  through  the  Fifth  pair  ;  and  the  experi- 
ments of  Valentin,  just  related,  fully  prove  that  the  animals  are  not  sensitive 
to  odours,  strictly  so  called,  after  the  Olfactory  has  been   divided.     It  is  by 
no  means  improbable,  however,  that  the  acuteness  of  the  true  sense  of  smell 
may  be   diminished  by  section  of  the  Fifth  pair;  since  the  olfactory  mem- 
brane is  no  longer  duly  moistened  by  its  proper  secretion;  and,  when  dry,  it  is 
not  so  susceptible  of  the  impressions  made  by  those  minute  particles  of  odori- 
ferous substances,  to  which  the  excitement  of  the  sensation  must  be  referred. 

442.  That  the  Second  pair,  or  Optic  nerves,  have  an  analogous  character, 
appears  alike  from   anatomical  and  experimental  evidence.     No  chemical  or 
mechanical  stimulus  of  the  nerve  produces  direct  muscular  motion  ;  nor  does 
it  give  rise,  as  far  as  can  be  ascertained,  to  indications  of  pain ;  whence  it  may 


340 


FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 


[Fig.  158. 


be  concluded,  that  this  nerve  is  not  one  of  common  sensation.  That  the  ordi- 
nary sensibility  of  the  eyeball  remains,  when  the  functions  of  the  Optic  nerve 
are  completely  destroyed,  is  well  known  ;  as  is  also  the  fact,  that  division  of 
it  puts  an  end  to  the  power  of  vision.  Valentin  states  that, although  the  Optic 
nerve  may,  like  other  nerves,  be  in  appearance  completely  regenerated,  he  has 

never  been  able  to  obtain  any  evi- 
dence that  the  power  of  sight  has 
been  in  the  least  degree  recovered. 
He  remarks  that  animals  suddenly 
made  blind  exhibit  great  mental  dis- 
turbance, and  perform  many  unaccus- 
tomed movements  ;  and  that  the  com- 
plete absence  of  the  power  of  vision 
is  easily  ascertained.  Morbid  changes 
are  sometimes  observed  to  take  place 
in  eyes,  whose  Optic  nerve  has  been 
divided  ;  but  these  are  by  no  means 
so  constant  or  so  extensive,  as  when 
the  Fifth  pair  is  paralyzed ;  and  they 
may  not  improbably  be  attributed  to 
the  injury,  occasioned  by  the  opera- 
tion itself,  to  the  parts  within  the  or- 
bit.— It  is  well  known  that,  when 
amaurosis  is  produced  by  a  morbid 
condition  of  the  Optic  nerve  alone, 
the  eye  retains  its  usual  appearance  ; 
but,  if  the  amaurosis  be  complete,  the 
texture  of  the  Retina  undergoes  a  re- 
markable change,  ceasing  to  exhibit 
that  peculiar  structure  which  normally 
characterizes  it.  Neither  primitive 
nervous  fibrils,  nor  nucleated  vesicles, 
can  be  distinguished  in  it,  and  the 
yellow  spot  of  Soemmering  becomes 
paler,  and  is  at  last  undistinguishable. 
But  if  a  very  slight  degree  of  sensi- 
bility to  light  remain,  these  changes 
are  much  less  decided.  Further,  it  is 
well  known  that,  when  the  sight  is 
destroyed  by  a  disease  or  injury, 
which  prevents  the  passage  of  light  through  the  pupil,  the  whole  eye  becomes 
more  or  less  atrophied  ;  and  the  Retina  and  Optic  nerve,  although  previously 
sound,  are  found  after  death,  (if  the  morbid  condition  have  lasted  sufficiently 
long)  to  have  lost  their  characteristic  structure.  It  seems  evident,  then,  that 
the  continuance  of  the  functional  operations  of  nerves,  is  a  necessary  condi- 
tion of  the  maintenance  of  their  normal  organization;  and  we  can  very  well 
understand  that  this  should  be  the  case,  from  the  analogy  of  other  parts  of  the 
system. 

443.  The  Optic  nerve,  though  analogous  to  the  Olfactory  in  all  the  points 
hitherto  mentioned,  differs  from  it  in  one  important  respect ; — that  it  has  the 
power  of  conveying  impressions  which  shall  excite  reflex  muscular  motions. 
This  is  especially  the  case  in  regard  to  the  Iris,  the  ordinary  actions  of  which 
are  regulated  by  the  degree  of  light  impinging  on  the  retina.  When  the  optic 
nerve  is  divided,  a  contraction  of  the  pupil  takes  place;  but  this  does  not 
occur,  if  the  connection  of  this  nerve  with  the  third  pair,  through  the  nerv- 


A  view  of  the  2d  pair  or  optic,  and  the  origins  of 
seven  other  pairs.  1, 1.  Globe  of  the  eye,  the  one 
on  the  left  hand  is  perfect,  but  that  on  the  right  has 
the  sclerotic  and  choroid  removed  to  show  the 
retina.  2.  The  chiasm  of  the  optic  nerves.  3.  The 
corpora  albic an tia.  4.  The  infundibulura.  5.  The 
Pons  Varolii.  6.  The  medulla  oblongata.  The 
figure  is  on  the  right  corpus  pyramidale.  7.  The 
3d  pair,  motores  oculi.  8.  4th  pair,  pathetici.  9. 
5th  pair,trigemini.  10.  6th  pair,  abducentes.  11. 
7th  pair,  auditory  and  facial.  12.  8th  pair,  pneumo- 
gastric,  spinal  accessory,  andjglosso-pharyngeal. 
13.  9th  pair,  hypoglossal.  ] 


NERVES  OF  SPECIAL  SENSE. OPTIC.  341 

ous  centres,  be  in  any  way  interrupted.  After  such  division  (if  complete), 
the  state  of  the  pupil  is  not  affected  by  variations  in  the  degree  of  light  im- 
pinging on  the  retina ;  except  in  particular  cases,  in  which  it  is  influenced 
through  other  channels.  Thus,  in  a  patient  suffering  under  amaurosis  of  one 
eye,  the  pupil  of  the  affected  eye  is  often  found  to  vary  in  size,  in  accord- 
ance with  that  of  the  other  eye  ;  but  this  effect  is  produced  by  the  action  of 
light  on  the  retina  of  the  sound  eye,  which  produces  a  motor  change  in  the 
third  pair  on  both  sides.  Further,  as  has  been  formerly  stated  (§  395),  the 
impression  only  of  light  upon  the  retina  may  give  rise  to  contraction  of  the 
pupil,  by  reflex  action,  when  the  optic  nerve  is  itself  sound  ;  whilst  no  sen- 
sations are  received  through  the  eye,  in  consequence  of  disease  in  the  sen- 
sorial  portion  of  the  nervous  centres.  Although  the  contraction  of  the  pupil 
is  effected  by  the  influence  of  motor  fibres,  which  proceed  to  the  sphincter 
of  the  Iris  from  the  third  pair  of  nerves,  through  the  Ophthalmic  ganglion, 
there  is  evidence  that  its  dilatation  depends  rather  upon  the  influence  it  de- 
rived from  that  ganglion  itself,  and  from  the  Sympathetic  system,  of  which  it 
forms  part. — Some  have  attempted  to  show,  that  the  actions  of  the  iris  are  in 
a  slight  degree  voluntary,  because,  by  an  effort  of  the  will,  they  could  occa- 
sion contraction  of  the  pupil ;  but  this  so-called  voluntary  contraction  is  al- 
ways connected  with  a  change  in  the  place  of  the  eyeball  itself,  occasioned 
by  an  action  of  some  of  its  muscles.  It  is  principally  noticed  under  the  two 
following  conditions : — 1.  When  an  object  is  brought  very  near  the  eye,  and  we 
steadily  fix  our  attention  upon  it,  the  axes  of  the  two  eyes  are  made  to  con- 
verge ;  and  if  this  convergence  be  carried  to  a  considerable  extent,  so  that  the 
pupils  of  both  eyes  are  sensibly  directed  towards  the  inner  canthus,  a  con- 
traction of  the  pupil  takes  place.  The  final  cause  or  purpose  of  this  contrac- 
tion is  very  evident.  When  an  object  is  brought  near  the  eye,  the  rays  pro- 
ceeding from  it  would  enter  the  pupil  (if  it  remained  of  its  usual  size)  at  an 
angle  of  divergence,  so  much  greater  than  that  which  would  allow  them  to 
be  properly  refracted  to  a  focus,  that  indistinct  vision  \vould  necessarily  re- 
sult. By  the  contraction  of  the  pupil,  however,  the  extreme  or  most  diver- 
gent rays  are  cut  off,  and  the  pencil  is  reduced  within  the  proper  angle.  The 
principle  is  precisely  the  same  as  that  on  which  the  optician  applies  a  stop 
behind  his  lenses,  which  reduces  their  aperture  in  proportion  to  the  shortness 
of  their  focal  distance.  2.  Contraction  of  the  pupil  is  also  noticed,  when  the 
eyeball  is  performing  that  rotation  upwards  and  inwards,  which,  when  per- 
formed along  with  violent  respiratory  actions,  or  during  sleep,  mus't  be  regarded 
as  involuntary.  This  rotation  also  takes  place,  to  a  slight  degree,  when  the 
eyelid  is  depressed,  as  in  ordinary  winking  ;  and  it  is  obvious  that,  in  this 
manner,  the  surface  of  the  eye  is  more  effectually  swept  free  from  impurities 
which  may  have  gathered  upon  it,  than  it  would  be  by  the  downward  motion 
of  the  lid  alone.  But  the  pupil  is  not  contracted,  when  the  eyeball  is  volun- 
tarily rotated  upwards  and  inwards. 

444.  Besides  the  contractions  of  the  pupil,  another  action,  which  has  been 
sometimes  spoken  of  as  reflex,  is  produced  through  the  Optic  nerve, — the 
contraction  of  the  Orbicularis  muscle  under  the  influence  of  strong  light,  or 
when  a  foreign  body  is  suddenly  brought  near  the  eye.  But  this  cannot  be 
produced  by  any  mechanical  stimulation,  and  it  evidently  involves  sensation  ; 
in  fact,  it  is  a  movement  of  a  consensual  kind,  produced  by  the  painful  effect 
of  light,  which  gives  rise  to  the  condition  well  characterized  by  the  term 
photophobia.  The  involuntary  character  of  it  must  be  evident  to  every  one, 
who  has  been  engaged  in  the  treatment  of  diseases  of  the  eyes;  and  the  effect 
of  it  is  aided  by  a  similarly-involuntary  movement  of  the  eyeball  itself,  which 
is  rotated  upwards  and  inwards,  to  a  greater  extent  than  the  Will  appears  able 
to  effect. 

29* 


342 


FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 


445.  There  is  a  further  peculiarity,  of  a  very  marked  kind,  attending  the 
course  of  the  Optic  nerves;  this  is  the  crossing  or  decussation  which  they 


[Fig.  159. 


[Fig.  160. 


Plan  of  the  optic  nerves  on  a 
small  scale,  showing  their  diver- 
gence from  the  chiasma,  c,  and 
their  junction  with  the  globe,  on 
the  inner  side  of  the  axis  of  the 
humors.] 


Course  of  fibres  }n  the  chiasma,  as  exhibited  by 
tearing  off  the  superficial  bundles  from  a  specimen 
hardened  in  spirit,  a.  Anterior  fibres,  commissural 
between  the  two  retinse.  -p.  Posterior  fibres,  com- 
missural between  the  thalami.  a',  p'.  Diagram  of 
the  preceding.] 


undergo,  more  or  less  completely,  whilst  proceeding  from  their  ganglia  to  the 
eyes.  In  some  of  the  lower^  animals,  in  which  the  two  eyes  (from  their  lateral 
position)  have  entirely  different  spheres  of  vision,  the  decussation  is  complete ; 
the  whole  of  the  fibres  from  the  right  optic  ganglion  passing  into  the  left  eye, 
and  vice  versa.  This  is  the  case,  for  example,  with  most  of  the  Osseous 
Fishes  (as  the  cod,  halibut,  &c.) ;  and  also,  in  great  part  at  least,  with  Birds. 
In  the  Human  subject,  however,  and  in  animals  which,  like  him,  have  the  two 
eyes  looking  in  the  same  direction,  the  decussation  seems  less  complete ;  but 
there  is  a  very  remarkable  arrangement  of  the  fibres,  which  seems  destined  to 
bring  the  two  eyes  into  peculiarly  consentaneous  action.  The  posterior  border 
of  the  Optic  Chiasma  is  formed  exclusively  of  commissural  fibres,  which  pass 
from  one  optic  ganglion  to  the  other,  without  entering  the  real  optic  nerve. 
Again,  the  anterior  border  of  the  Chiasma  is  composed  of  fibres,  which  seem, 
in  like  manner,  to  act  as  a  commissure  between  the  two  retinas;  passing  from 
one  to  the  other,  without  any  connection  with  the  optic  ganglia.  The  tract 
which  lies  between  the  two  borders,  and  occupies  the  middle  of  the  Chiasma, 
is  the  true  Optic  Nerve  ;  and  in  this  it  would  appear  that  a  portion  of  the  fibres 
decussates,  whilst  another  portion  passes  directly  from  each  Optic  ganglion 
into  the  corresponding  eye.  The  fibres  which  proceed  from  the  ganglia  to 
the  retinae,  and  constitute  the  proper  Optic  Nerves,  may  be  distinguished  into 
an  internal  and  an  external  tract.  Of  these,  the  external  on  each  side,  passes 
directly  onwards  to  the  eye  of  that  side ;  whilst  the  internal  crosses  over  to 
the  eye  of  the  opposite  side.  The  distribution  of  these  two  sets  of  fibres  in 
the  retina  of  each  eye  respectively,  is  such  that,  according  to  Mr.  Mayo,  the 
fibres  from  either  optic  ganglion  will  be  distributed  to  its  own  side  of  both 
eyes  ;  the  right  optic  ganglion  being  thus  exclusively  connected  with  the  outer 
part  of  the  retina  of  the  right  eye,  and  with  the  inner  part  of  the  retina  of  the 
left  eye ;  and  the  left  optic  ganglion  being,  in  like  manner,  connected  exclu- 
sively with  the  outer  side  of  the  left  retina,  and  with  the  inner  side  of  the 
right.  Now  as  either  side  of  the  eye  receives  the  images  of  objects,  which 
are  on  the  other  side  of  its  axis,  it  follows,  if  this  account  of  their  distribution 
be  correct,  that  in  Man,  as  in  the  lower  animals,  each  ganglion  receives  the 
sensations  of  objects  situated  on  the  opposite  sides  of  the  body.  The  purpose 
of  this  decussation  may  be,  to  bring  the  visual  impressions,  which  are  so  im- 
portant in  directing  the  movements  of  the  body,  into  proper  harmony  with  the 


NERVES  OF  SPECIAL  SENSE. AUDITORY  AND  GUSTATORY. 


343 


[Fig.  161. 


apparatus ;  so  that,  the  decussation  of  the  motor  fibres  in  the  pyramids  being 
accompanied  by  a  decussation  of  the  optic  nerves,  the  same  effect  is  produced 
as  if  neither  decussated, — which  last  is  the  case  with  Invertebrated  animals  in 
general. 

446.  The  functions  of  the  Auditory  nerve,  or  Portio  Mollis  of  the  Seventh, 
are  easily  determined,  by  anatomical  examination  of  its  distribution,  and  by 
observation  of  pathological  phenomena,  to  be  analogous  to  those  of  the  two 
preceding,     Atrophy  or  lesion  of  the  trunk  destroys  the  sense  of  Hearing; 
whilst  irritation  of  it  produces  auditory  sensations,  but  does  not  occasion  pain. 
From  experiments  made  upon  the 

nerve  before  it  leaves  the  cranial 
cavity,  it  appears  satisfactorily  as- 
certained, that  this  nerve  is  not 
endowed  either  with  common  sen- 
sibility, or  with  the  power  of  di- 
rectly stimulating  muscular  move- 
ment. Nor  can  any  obvious  reflex 
actions  be  executed  by  irritation  of 
this  nerve;  but  it  seems  neverthe- 
less by  no  means  improbable,  that 
the  muscles  which  regulate  the  ten- 
sion of  the  tympanum,  are  called 
into  action  by  impressions  made 
upon  it  and  reflected  through  the 
auditory  ganglion,  in  the  same  man- 
ner as  the  diameter  of  the  pupil  is  A  view  of  the  origin  and  distribution  of  the  Portio 
regulated  through  the  Optic  nerve.  Mollis  of  the  Seventh  pair  or  Auditory  Nerve  ;  1,  the 

It   has    been    attempted    by    FloU-     medulla  oblongata;  2,  the  pons  Varolii ;  3,  4,thecrura 

reilS    to    Show,  that    the    division    of     cerebelli  of  the  right  side;  5  the  eighth  pair  of  nerves; 

•..  ,.  ,        6,  the  ninth  pair;  7,  the  auditory  nerve  distributed  to 

the  Auditory  nerve,  Which  proceeds     thec0chlea  and  labyrinth;  8,  the  sixth  pair  of  nerves; 

tO     the     Semi-circular      Canals,     has     9,  the  portio  dura  of  the  seventh  pair;  10,  the  fourth 

functions    altogether  different  from    pair;  n,  the  fifth  pair.] 
that  portion  which  supplies  the  Ves- 
tibule and  Cochlea.     This  inference,  however,  is  grounded  only  upon  the 
movements  exhibited  by  animals,  in  which  these  nerves  are  irritated ;  which 
movements  are  capable  of  a  different  explanation  (§  432). 

a.  It  is  interesting  to  remark,  that  microscopic  examination  of  the  structure  of  the  Audi- 
tory nerve  clearly  indicates  its  intermediate  character  between  the  nerves  of  special  sensa- 
tion issuing  from  the  anterior  part  of  the  cranium  (namely,  the  Optic  and  Olfactory),  and 
those  whose  function  is  to  minister,  either  to  common  sensation,  or  to  that  of  Taste,  which 
approaches  nearly  to  it,  (namely,  the  Fifth  pair  and  the  Glosso-pharyngeal,)  which  issue 
from  the  posterior  part  of  the  Encephalon,  and  are  more  nearly  analogous  to  the  Spinal 
nerves.  The  primitive  fibres  are  not  so  soft  as  those  of  the  Olfactive,  nor  so  slender  as 
those  of  the  Optic  ;  and  they  are  softer  than  those  of  the  Glosso-pharyngeal.  Moreover,  the 
Auditory  nerve  forms  a  plexus  with  the  Facial,  to  which  there  is  no  analogy  in  the  Optic 
and  Olfactive  nerves,  but  to  which  a  similar  one  exists  in  the  Glosso-pharyngeal.  This 
intermediate  structural  character  is  interesting,  when  we  compare  it  with  the  intermediate 
character  of  the  function;  for  the  impressions  made  upon  the  sense  of  Hearing  are  pro- 
duced through  vibrations  of  a  material  fluid, — instead  of  being,  as  in  the  case  of  Sight,  the 
result  of  changes  so  subtle  as  to  be  almost  inscrutable  to  our  means  of  research, — or,  as  in 
the  case  of  Taste  and  Touch,  being  produced  by  the  direct  contaA  of  the  substance  which 
gives  rise  to  the  sensation. 

447.  The  nerves  which  minister  to  the  sense  of  Taste,  as  already  men- 
tioned,  are   destitute   of  the  peculiarities  which   distinguish   the  preceding; 
being  no  other  than  certain  branches  of  ordinary  afferent  nerves, — the  Fifth 
Pair  and   Glosso-pharyngeal, — the   peculiar  endowments  of  which  seem  to 


344  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

depend  rather  upon  the  structure  and  actions  of  the  papillae  at  their  peripheral 
extremities,  than  upon  anything  special  in  their  own  characters. — From  the 
recent  observations  and  experiments  of  M.  Ch.  Bernard,  it  appears  that  the 
Facial  nerve  (Portio  Dura  of  the  7th)  supplies  some  condition  requisite  for 
the  sense  of  Taste,  through  the  branch  known  as  the  Chorda  Tympani,  which 
is  the  motor  nerve  of  the  Lingualis  muscle.  When  paralysis  of  the  Facial 
exists  in  Man,  the  sense  of  taste  is  very  much  impaired  on  the  corresponding 
side  of  the  tongue,  provided  the  cause  of  the  paralysis  be  seated  above  the 
origin  of  the  Chorda  Tympani  from  its  trunk.  Similar  results  have  been  ob- 
tained from  experiments  upon  other  animals.  The  nature  of  the  influence 
afforded  by  this  nerve  is  entirely  unknown  ;  and  it  is  the  more  obscure,  as  the 
Chorda  Tympani  contains  no  sensory  filament. 

448.  To  the  sense  of  Touch,  all  the  afferent  nerves  of  the  body  (save  the 
nerves  of  special  sense)  appear  to  minister;  in  virtue — according  to  the  hypo- 
thesis here  upheld — of  the  direct  connection  of  certain  of  their  fibrils  with  the 
Sensorium  commune.    But  the  degree  in  which  they  are  capable  of  producing 
Sensations,  does   not  bear  any  constant  relation   to   their  power  of  exciting 
Reflex  actions.     Thus,  the  Glosso-pharyngeal  is  not  nearly  so  sensitive  as 
the  Fifth  pair;  though  more  powerful  as  an  excitor  nerve.     The  Par  Vagum 
appears  to  have  even  less  power  of  arousing  sensory  changes ;  although  it  is 
the  most  important  of  all  the  excitors  to  reflex  action.     So  again,  the  afferent 
nerves  of  the  inferior  extremities,  in  Man,  are  less  concerned  in  ministering 
to  sensations,  than  are  those  of  the  superior ;  and  yet  they  appear  to  be  much 
more  efficient  as  excitors  to  muscular  action. — These  differences  may  be  ac- 
counted for,  by  supposing  that  the  proportion  which  the  fibres,  having  their 
centre  in  the  ganglionic  matter  of  the  Spinal  Cord,  bear  to   that  of  the  fibres 
which  pass  on  to  the  Sensorium,  is  not  constant,  but  is   liable  to  variation ; 
the  former  predominating  in   the   Par  Vagum   and   the  Glosso-pharyngeal ; 
whilst  the  latter  are  more  numerous  in  the  Fifth  Pair,  and  in  most  of  the  Spi- 
nal nerves. 

449.  It  appears,  from  what  has  been  already  stated,  that  all  the  motor  fibres 
of  the  Cerebro-spinal  system,  not  exclusively  concerned  in  Reflex  movements, 
must  be  in  connection  with   the  Sensory  ganglia ;  since  we  find  that  their 
actions,  whether  simply  consensual,   emotional,  or  volitional,  are   dependent 
upon  guiding  sensations.     Of  these   sensations,  the  greater  proportion  are 
received  from  the  muscles  themselves  ;  but  there  are  certain  cases,  as  we  have 
seen,  in  which  the  guiding  influence  is  communicated  rather  by  the  organs 
and  nerves  of  Special  sense.     Of  these,  a  good  example  is  afforded  by  the 
movements  of  the  Eyeball,  presently  to  be  examined  in  detail ;  and  another 
is  to  be  found  in  those  of  the  Larynx,  to  be  fully  treated  of  hereafter  (Chap, 
viii.).    The  Emotions,  in  like  manner,  may  operate  upon  all  the  motor  nerves 
of  the  body;  as  we  see  in  the  violent  movements  of  unrestrained  passion,  or 
in  the  increased  power  given  to  voluntary  efforts,  by  the  simultaneous  excite- 
ment of  certain  emotional  states.     But,  as  already  remarked,  their  ordinary 
action  is  most  displayed  through  the  motor  nerves  of  the  face  and  respiratory 
organs. 

450.  Consensual  Movements  of  the  Eye. — It  will  be  recollected  that,  in 
the  Human  Orbit,  six  muscles  for  the  movements  of  the  eyeball  are  found, — 
the  four  recti,  and  the,  two  oblique  muscles.     The  precise  actions  of  these  are 
not  easily  established  by  experiment  on  the  lower  animals ;  for  in  all  those 
which  ordinarily  maintain  the  horizontal  position,  there  is  an  additional  mus- 
cle, termed  the  retractor,  which  embraces  the  whole  posterior  portion  of  the 
globe,  and  passes  backwards  to  be  attached  to  the  bottom  of  the  orbit.     This 
muscle  is  most    developed  in  Ruminating  animals,  which,  during  their  whole 
time  of  feeding,  carry  their  heads  in  a  dependent  position.     In  most  Carni- 


CONSENSUAL  MOVEMENTS  OF  THE  EYE.  345 

vorous  animals,  instead  of  the  complete  hollow  muscular  cone  (the  base  inclos- 
ing the  eyeball,  whilst  the  apex  surrounds  the  optic  nerve)  which  we  find  in 
the  Ruminants,  there  are  four  distinct  strips,  almost  resembling  a  second  set 
of  recti  muscles,  but  deep-seated,  and  inserted  into  the  posterior  instead  of  the 
anterior  portion  of  the  globe.  It  is  obvious  that  the  actions  of  these  must 
greatly  affect  the  results  of  any  operation,  which  we  may  perform  upon  the 
other  muscles  of  the  Orbit;  and,  as  it  is  impossible  to  divide  the  former, 
without  completely  separating  the  eye  from  its  attachments,  we  have  no  means 
of  correcting  such  results,  but  by  reasoning  alone.  Experiments  upon  ani- 
mals of  the  order  of  Quadrumana,  most  nearly  allied  to  Man,  would  be  more 
satisfactory  ;  as  in  them,  the  retractor  muscle  is  almost  or  entirely  absent. — 
If  the  origin  and  insertion  of  the  four  Recti  muscles  be  examined,  however, 
no  doubt  can  remain  that  each  of  them,  acting  singly,  is  capable  of  causing 
the  globe  to  revolve  in  its  own  direction, — the  superior  rectus  causing  the  pupil 
to  turn  upwards, — the  internal  rectus  causing  it  to  roll  towards  the  nose, — and 
so  on.  A  very  easy  and  direct  application  of  the  laws  of  mechanics  will  fur- 
ther make  it  evident  to  us,  that  the  combined  action  of  any  two  of  the  Recti 
muscles  will  cause  the  pupil  to  turn  in  a  direction  intermediate  between  the 
lines  of  their  single  action ;  and  that  any  intermediate  position  may  thus  be 
given  to  the  eyeball  by  these  muscles  alone.  This  fact,  which  has  not 
received  the  attention  it  deserves,  leads  us  to  perceive,  that  the  Oblique  mus- 
cles must  have  some  supplementary  function.  It  may  be  objected  that  this  is 
a  theoretical  statement  only ;  and  that  there  may  be  some  practical  obstacle 
to  the  performance  of  diagonal  movements  by  the  Recti  muscles,  which  ren- 
ders the  assistance  of  the  Obliques  essential  for  this  purpose.  But  to  this  it 
may  be  replied,  that  no  single  muscle  can  direct  the  ball  either  downwards 
and  inwards,  or  upwards  and  outwards;  and  that,  as  we  have  good  reason  to 
believe  these  movements  to  be  effected  by  the  combination  of  the  Recti  mus- 
cles, there  is  no  reason  why  the  other  diagonal  movements  should  not  also  be 
due  to  them. 

451.  The  most  probable  account  of  the  functions  of  the  Oblique  muscles  of 
the  eye,  seems  to  be  that  which  was  long  ago  suggested  by  John  Hunter,  and 
which  has  received  confirmation  from  the  recent  experiments  of  Dr.  G.  John- 
son.*— It  has  been  just  shown  that  the  action  of  the  Recti  muscles  upon  the 
pupil,  is  such  as  to  cause  it  to  revolve  in  any  given  direction ;  and  they  are 
put  in  action,  not  merely  to  alter  the  range  of  vision,  the  head  remaining 
stationary,  but  also  to  keep  the  range  of  vision  the  same,  and  to  cause  the 
images  of  the  objects,  upon  which  our  gaze  is  fixed,  still  to  fall  upon  the 
same  parts  of  the  retinae,  by  maintaining  the  position  of  the  eyes  when  the 
head  is  moved  upwards,  downwards,  from  side  to  side,  or  in  any  intermediate 
direction.  But  these  muscles  are  not  able  to  rotate  the  eyeball  upon  its  antero- 
posterior  axis ;  and  such  rotation  is  manifestly  necessary  to  preserve  the  fixed 
position  of  the  eyeball,  and  consequently  to  keep  the  image  of  the  object  un- 
der survey  upon  the  same  part  of  the  retina,  when  the  head  is  inclined  side- 
ways, or  bowed  towards  one  shoulder  and  then  towards  the  other.  It  appears 
from  the  experiments  of  Dr.  G.  Johnson,  that  the  action  of  the  Oblique  mus- 
cles is  exactly  adapted  to  produce  such  a  rotation;  the  Inferior  oblique,  in  its 
contraction,  causing  the  eyeball  to  move  upon  its  antero-posterior  axis,  in  such 
a  manner  that  a  piece  of  paper,  placed  at  the  outer  margin  of  the  cornea,  passed 
downwards  and  then  inwards  towards  the  nose;  and  the  Superior  oblique 
effecting  precisely  the  reverse  action,  the  paper  at  the  outer  margin  of  the  cor- 
nea passing  first  upwards  and  then  inwards.  There  was  not  the  slightest 
appearance,  in  these  experiments,  of  elevation,  depression,  abduction,  or  ad- 

*  Cyclopaedia  of  Anatomy  and  Physiology,  vol.  iii.  p.  790. 


346  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

duction,  of  the  cornea,  as  a  result  of  the  action  of  the  Oblique  muscles ;  all 
these  movements  being  attributable  to  the  Recti  alone. 

452.  On  studying  the  conjoint  movements  of  the  Eyeball,  we  are  led  to 
observe  the  very  curious  fact,  that  they  are  not  so  much  symmetrical  as  har- 
monious; that  is  to  say,  the  corresponding  muscles  on  the  two  sides  are  rarely 
in  action  at  once ;  whilst  such  a  harmony  or  consent  exists  between  the  ac- 
tions of  the  muscles  of  the  two  orbits,  that  they  work  to  one  common  purpose, 
namely,  the  direction  of  both  eyes  towards  the  required  objects.     In  order  to 
study  them  properly,  it  is  necessary  to  reduce  them  to  some  kind  of  classifica- 
tion.    We  may  divide  them  into  the  Voluntary  and  the  Involuntary ;  and  the 
former,  being  numerous,  require  to  be  further  classified.     They  may  be  ar- 
ranged under  two  groups ;  the  first  comprising  those  which  are  alike  har- 
monious and  symmetrical ;  the  second  including  those  which  are  harmonious 
but  not  symmetrical. — To  the  first  group  belong  the  following: — 1.  Both 
eyeballs  are  elevated  by  the  contraction  of  the  two  Superior  Recti. — 2.  Both 
eyeballs  are  depressed  by  the  conjoint  action  of  the  Inferior  Recti  muscles. — 
3.  Both  are  drawn  directly  inwards,  or  inwards  and  downwards,  as  when 
we  look  at  an  object  placed  on  or  near  the  nose  ;  this  movement  is  effected  by 
the  action  of  the  Internal  Recti  of  the  two  sides,  with  or  without  the  Inferior 
Recti.     It  is  evidently  symmetrical,  but  might  seem  at  first  sight  not  to  be 
harmonious,  because  the  eyes  do  not  move  together  towards  one  side  or  the 
other;  it  is,  however,  really  harmonious,  since  their  axes  are  directed  towards 
the  same  point. — Now  it  is  to  be  observed,  with  regard  to  these  movements, 
that  we  can  never  effect  them  in  antagonism  with  each  other,  or  with  those  of 
other  muscles.    We  cannot,  for  example,  raise  one  eye  and  depress  the  other ; 
nor  can  we  raise  or  depress  one  eye,  when  we  adduct  or  abduct  the  other. 
The  explanation  of  this  will  be  found  in  the  fact,  that  we  can  never,  by  so 
doing,  direct  the  eyes  to  the  same  point. — The  harmonious  but  unsymmetrical 
movements,  forming  the  second  class,  are  those  in  which  the  Internal  and  Ex- 
ternal Recti  of  the  two  sides  are  made  to  act  together,  either  alone,  or  in  con- 
junction with  the  Superior  and  Inferior  Recti.     They  are  as  follows. — 4.  One 
eye  is  made  to  revolve  directly  inwards,  by  the  action  of  its  Internal  Rectus, 
whilst  the  other  is  turned  outwards  by  the  action  of  its  External  Rectus. — 5. 
One  eye  is  made  to  revolve  upwards  and  inwards,  by  the  conjoint  action  of 
the  Internal  and  Superior  Recti ;  the  other,  upwards  and  outwards,  by  the 
conjoint  action  of  the  External  and  Superior  Recti. — 6.   One  eye  is  made  to 
revolve  downwards  and  inwards,  by  the  conjoint  action  of  the  Internal  and 
Inferior  Recti ;  the  other,  downwards  and  outwards,  by  the  conjoint  action 
of  the  External  and  Inferior  Recti. — In  these  movements,  two  different  mus- 
cles, the  Abducens  and  Adducens,  are  called  into  action  on  the  two  sides;  but 
they  are  so  employed  for  the  purpose  of  directing  the  axes  of  the  eyes  towards 
the  same  point. 

453.  The  normal  Involuntary  movements  of  the  eyeballs  are  only  of  two 
kinds. — 1.  The  rotation  of  the  two  eyeballs  on  their  own  axes,  which  takes 
place  when  the  head  is  moved  in  certain  directions  (§  451) ;  this  is  effected 
in   direct  respondence  to  certain  guiding  sensations,  and  without  any  influ- 
ence or  control   on  the   part  of  the  will;  it  is  therefore  a  purely  consensual 
action. — 2.  The  revolution  of  both  eyes  upwards  and  inwards,  which  takes 
place  in  the  acts  of  coughing,  sneezing,  winking,  &c. ;  this  is  altogether  inde- 
pendent of  visual  sensations,  and  is  commonly,  like  the  other  movements 
associated  in  these   actions,  of  a  reflex  nature. — Many  abnormal  movements 
of  the  eyeballs,  in  which   there  is  neither  harmony  nor  symmetry  in  the 
actions  of  the  muscles,  present  themselves  in  convulsive  diseases. 

454.  It  may  be  stated  as  a  physiological  fact,  that  Single  Vision  with  two 
eyes  is  dependent  upon  the  formation  of  the  image  upon  parts  of  the  two 


CONSENSUAL  MOVEMENTS  OF  THE  EYE.  347 

retinae,  which  are  accustomed  thus  to  act  with  each  other.  In  many  physio- 
logical works  it  is  asserted,  that  single  vision  is  the  result  of  the  impressions 
being  made  on  corresponding  parts  of  the  two  retinae, — that  is  to  say,  on 
parts  equally  distant  from  the  axis,  on  one  side  or  the  other  :  but  this  seems 
to  be  disproved  by  the  fact,  that  patients  who  have  been  long  affected  with 
Convergent  Strabismus,  and  who  see  equally  well  with  both  eyes  (as  many 
do),  are  not  troubled  with  double  vision.  On  the  other  hand,  when  a  person 
whose  eyes  look  straight  before  him,  is  the  subject  of  a  disorder  which 
renders  their  motions  in  any  degree  irregular,  he  is  at  once  affected  with 
double  vision  ;  and  the  same  has  been  noticed  to  be  a  common  immediate 
result  of  the  successful  operation  for  the  cure  of  strabismus,  where  vision  is 
good  in  both  eyes.  Although  the  images  were  previously  formed  on  parts  of 
the  retinae  which  were  very  far  from  corresponding  with  each  other,  yet  no 
sooner  is  the  position  of  the  eyes  rectified  (so  that  the  relation  between  the 
situation  of  the  images  is  the  same  as  it  would  have  been  in  a  sound  eye), 
than  the  patient  sees  double.  Now  in  these  cases  the  difficulty  very  speedily 
diminishes,  and  the  patient  soon  learns  to  see  single.  It  can  scarcely  be 
imagined,  then,  that  to  any  other  cause  than  habit,  is  to  be  attributed  the 
long-discussed  phenomenon  of  single  vision  with  two  eyes.  The  mind  re- 
ceives the  two  images,  frequently  combining  them  together  (as  Mr.  Wheat- 
stone's  ingenious  experiments  with  the  Stereoscope  have  most  satisfactorily 
shown,  §  547)  to  produce  a  picture  in  relief;  and  so  long  as  these  are  con- 
veyed to  it  in  the  accustomed  manner,  it  reconciles  them  together,  even  if  the 
parts  of  the  retinae  on  which  they  are  formed  do  not  correspond;  but  if  any 
circumstance  break  this  chain,  and  cause  the  images  to  be  transmitted  to  the 
sensorium  through  a  irew  channel,  the  mind  requires  some  little  time  to 
adapt  itself  to  this  impression,  as  it  does  by  habit  to  almost  every  other. 

a.  That  there  is  a  greater  tendency  to  consent  between  the  images,  when  they  are  formed 
upon  corresponding  parts  of  the  retinae,  the  Author  readily  admits ;  and  he  thinks  that  this 
is  a  principle  of  some  importance,  in  explaining  the  re-adjustment  of  the  eyes,  after  the 
operation  for  Strabismus.     Every  one  who  has  seen  much  of  this  operation  is  aware,  that 
the  re-adjustment  of  the  eye  is  not  always  immediate,  but  that,  after  the  muscle  has  been 
freely  divided,  the  eye  often  remains  somewhat  inverted  for  a  few  days,  gradually  acquir- 
ing its  straight  position.     The  Author  has  known  one  case,  in  which,  after  such  a  degree  of 
temporary  inversion  as  seemed  to  render  the  success  of  the  operation  very  doubtful,  e ver- 
sion actually  took  place  for  a  short  time  to  a  considerable  extent  ;  after  which  the  axes  be- 
came parallel,  and  have  remained  so  ever  since. 

b.  Another  argument,  derived  from  the  results  of  this  operation,  in  favour  of  the   con- 
sensual movement  being  chiefly  dependent  upon  the  place  of  the  impressions  on  the  retina> 
is,  that  it  is  much  more  successful  in  those  cases,  in  which  the  sight  of  the  most  displaced 
eye  is  good,  than  in  those  in  which,  (as  not  unfrequently  happens  from  long  disuse)  it  is 
much  impaired.     In  cases  of  the  latter  class,  the  cure  is  seldom  complete.     There  is  another 
curious  fact,  which  may  be  adverted  to  in  reference  to  this  subject :     Strabismus  not  unfre- 
quently arises  from  the  formation  of  an  opaque  spot  on  the  centre  of  the  cornea,  which  pre- 
vents the  formation  of  any  images  on  the  retina,  except  by  the  oblique  rays ;  and  nature 
seems  to  endeavour  (so  to  speak)  to  repair  the  mischief,  by  causing  the  eye  to  assume  the 
position  most  favourable  for  the  reception  of  these. 

c.  To  one  more  point  only,  connected  with  the  subject  of  Strabismus,  would  the  Author 
now  allude.     He  is  well  convinced,  from  repeated  observation,  that  those  Surgeons  are  in  the 
right,  who  have  maintained,  in  a  recent  controversy,  that,  in  a  large  proportion  of  cases, 
strabismus  is  caused  by  an  affection  of  both  sets  of  muscles  or  nerves,  and  not  of  one  only ; 
and  that  it  then  requires,  for  its  perfect  cure,  the  division  of  the  corresponding  muscle  on 
both   sides.     Cases  will  be  frequently  met  with,  in  which  this  is  evident ;  the  two  eyes 
being  employed  to  nearly  the  same  extent,  and  the  patient  giving  to  both  a  slight  inward 
direction,  when  desired  to  look  straight  forwards.     In   general,  however,  one  eye  usually 
looks  straight  forwards,  whilst  the  other  is  greatly  inverted;  and  the  sight  of  the  inverted 
eye  is  frequently  affected  to  a  considerable  degree  by  disuse ;  so  that,  when  the  patien: 
voluntarily  rotates  it  into  its  proper  axis,  his  vision  with  it  is  far  from  being  distinct.     Some 
Surgeons  have  maintained,  that  the  inverted  eye  is  usually  the  only  one  in  fault,  and  con- 
sider that  the  division  of  the  tendon  of  its  Internal  Rectus  is  sufficient  for  the  cure.     They 


348  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

would  even  divide  its  other  tendons,  if  the  parallelism  be  not  restored,  rather  than  touch 
the  other  eye.  The  Author  is  himself  satisfied,  however,  that  the  restriction  of  the  abnor- 
mal state  to  a  single  eye,  is  the  exception,  and  not  the  rule,  in  all  but  very  slight  cases  of 
strabismus ;  and  to  this  opinion  he  is  led  both  by  the  consideration  of  the  mode  in  which 
strabismus  first  takes  place,  and  by  the  results  of  the  operations  which  have  come  under  his 
notice.  If  the  eyes  of  an  infant  affected  with  cerebral  disease  be  watched,  there  will  fre- 
quently be  observed  in  them  very  irregular  movements;  the  axes  of  the  two  being  some- 
times extremely  convergent,  and  then  very  divergent.  This  irregularity  is  rarely  or  never 
seen  to  be  confined  to  one  eye.  Now,  in  a  large  proportion  of  cases  of  Strabismus,  the 
malady  is  a  consequence  of  some  cerebral  affection  during  infancy  or  childhood,  which  we 
can  scarcely  suppose  to  have  affected  one  eye  only.  Again,  in  other  instances  we  find  the 
Strabismus  to  have  resulted  from  the  constant  direction  of  the  eyes  to  very  near  objects,  as 
in  short-sighted  persons ;  and  here,  too,  the  cause  manifestly  affects  both. 

d.  Now  it  is  easy  to  understand,  why  one  eye  of  the  patient  should  appear  to  be  in  its 
natural  position,  whilst  the  other  is  greatly  inverted.  •  The  cause  of  strabismus  usually 
affects  the  two  eyes  somewhat  unequally,  so  that  one  is  much  more  inverted  than  the  other. 
We  will  call  the  least  inverted  eye  A,  and  the  other  B.  In  the  ordinary  acts  of  vision,  the 
patient  will  make  most  use  of  the  least  inverted  eye,  A,  because  he  can  most  readily  look 
straight  forwards  or  outwards  with  it ;  but  to  bring  it  into  the  axis,  or  to  rotate  it  outwards, 
necessitates  a  still  more  decided  inversion  of  B.  This  remains  the  position  of  things, — the 
patient  usually  looking  straight  forwards  with  A,  which  is  the  eye  constantly  employed  for 
the  purposes  of  vision, — and  frequently  almost  burying  under  the  inner  canthus  the  other 
eye,  B,  the  vision  in  which  is  of  very  little  use  to  him.  When,  therefore,  the  tendon  of  the 
internal  rectus  of  B  is  divided,  the  relative  position  of  the  two  is  not  entirely  rectified. 
Sometimes  it  appears  to  be  so  for  a  time ;  but  the  strabismus  then  begins  to  return,  and  it 
can  only  be  checked  by  division  of  the  tendon  of  the  other  eye,  A;  after  which  the  cure  is 
generally  complete  and  permanent.  That  it  has  not  been  so,  in  many  of  the  cases  on 
which  operations  have  been  performed,  the  Author  attributes,  without  the  slightest  doubt  in 
his  own  mind,  to  the  neglect  of  the  second  operation.  As  just  now  stated,  the  sight  of  the 
most  inverted  eye  is  frequently  very  imperfect ;  indeed  it  is  sometimes  impaired  to  such  an 
extent,  that  the  patients  speak  of  it  as  entirely  useless.  That  this  impairment  results  in  part 
from  disuse  merely,  seems  very  evident,  from  the  great  improvement  which  often  succeeds 
the  rectification  of  the  axes.  The  Author  cannot  help  thinking  it  probable,  however,  that 
the  same  cause  which  produced  the  distortion  of  the  eye  may,  in  some  -instances  at  least, 
have  affected  the  Optic  nerve,  as  well  as  the  Motor  nerves  of  the  orbit ;  and  this  idea  is 
borne  out  by  the  fact  of  the  restoration  of  sight,  in  certain  cases  of  Amaurosis,  by  division  of 
one  or  more  tendons,  where  no  Strabismus  previously  existed.  (See  Adams  on  Muscular 
Amaurosis.)  It  is  interesting  to  remark  that,  in  these  cases,  Strabismus  was  usually  the 
first  effect  of  the  operation  ;  but  that  the  eye  generally  recovered  its  ordinary  position  within 
a  short  time,  especially  when  the  sight  was  improving. 

455.  If  this  be  admitted,  we  gain  an  important  step  in  the  explanation  of 
the  Consensual  movements  of  the  Eye.  The  object  to  be  attained  is  evidently 
this, — that  the  usual  axes  of  the  eye  should  always  be  directed  towards  the 
object  to  be  viewed ;  and  this,  as  we  have  seen,  involves  the  necessity  (in  a 
great  majority  of  cases),  of  unsymmetrical  movements  being  performed  by 
the  two  eyeballs.  The  combination  of  these  movements  is  involuntary  or 
automatic ;  and  appears  to  be  regulated  by  the  sensations  received  through 
the  retinae.  It  is  well  known  that,  in  children  born  blind,  the  movements  are 
not  consensual ;  they  are  frequently  very  far  from  being  so,  in  cases  of  con- 
genital cataract,  where  a  considerable  amount  of  light  is  evidently  admitted, 
but  where  no  distinct  image  can  be  formed  ;  and  in  such  cases,  the  movements 
are  most  consensual  where  the  object  is  bright  and  luminous,  and  a  more  vivid 
impression  therefore  made  upon  the  retina.  It  is  no  objection  to  this  theory 
to  say,  that  persons  who  have  become  blind  may  still  move  their  eyes  in  a 
consensual  manner ;  since,  the  habit  of  the  association  of  particular  move- 
ments having  been  once  acquired,  the  guidance  of  the  muscles  may  be  effected 
by  sensations  derived  from  themselves,  in  the  manner  in  which  it  takes  place 
in  the  laryngeal  movements  of  the  deaf  and  dumb  ;  and,  as  a  matter  of  fact, 
a  want  of  consent  may  be  often  noticed  where  the  blindness  is  total.  The 
peculiar  vacant  appearance,  which  may  be  noticed  in  the  countenances  of  per- 
sons completely  deprived  of  sight  by  amaurotic  or  other  affections,  which  do 


FUNCTIONS  OF  THE  CEREBELLUM.  349 

not  alter  the  external  aspect  of  the  eyes,  seems  to  result  from  this, —  that  their 
axes  are  parallel,  as  if  the  individual  were  looking  into  distant  space,  instead 
of  presenting  that  slight  convergence  which  must  always  exist  between  them, 
when  the  eyes  are  fixed  upon  a  definite  object.  This  convergence,  which  is 
of  course  regulated  by  the  Internal  Recti,  varies  in  degree  according  to  the 
distance  of  the  object,  and  it  is  astonishing  how  minute  an  alteration  in  the 
axes  of  the  eyes  is  perceptible  to  a  person  observing  them.  For  instance,  A. 
sees  the  eyes  of  B  directed  towards  his  face,  but  he  perceives  that  B  is  not 
looking  at  him  ;  he  knows  this  by  a  sort  of  intuitive  interpretation  of  the 
fact,  that  his  face  is  not  the  point  of  convergence  of  B's  eyes.  But  if  B,  who 
might  have  been  previously  looking  at  something  nearer  or  more  remote  than 
A's  face,  fix  his  gaze  upon  the  latter,  so  that  the  degree  of  the  convergence  of 
the  axes  is  altered,  without  the  general  direction  of  the  eyes  being  in  the  least 
affected,  the  change  is  at  once  perceived  by  the  person  so  regarded  ;  and  the 
eyes  of  the  two  then  meet. 

456.  The  foregoing  considerations  maybe  summed  up  in  this  simple  state- 
ment : — that,  when  we  voluntarily  direct  our  eyes   towards  any  object,  the 
actions  of  the  several  muscles  concerned,  are  guided  by  the  visual  sensations, 
rather  than  by  the  ordinary  muscular  sense,  through  which  other  voluntary 
movements  are  regulated.     In  this  manner  are  accomplished,  not  merely  the 
revolutions  of  the  eyeballs  from  side  to  side,  upwards  and  downwards,  or  in 
any  direction  that  is  required  to  cause  the  image  to  fall  most  advantageously 
upon  the  two  retinae  ;  but  also  that  rotation  on  their  axes,  which  keeps  the 
images  in  the  same  position  upon  the'1  retina,  when  the  head  moves  in  a  plane 
perpendicular  to  their  axes ;  and  likewise  that  exact  convergence  of  the  two 
axes  which  shall  cause  them  to  meet  in  the  object  on  which  the  attention  is 
fixed,  and  which  consequently  varies  with  its  distance.     Of  all  the  movements 
of  the  eyes,  there  is  none  which  exhibits  the  necessity  of  the  guiding  visual 
sensations   so  much  as  the  revolution  of  both  eyes  inwards.     Some  persons 
can  effect  this  voluntarily  to  a  greater  extent  than  others  ;  but  even  then,  they 
can  only  accomplish  it  by  fixing  the  gaze  upon  some  object  situated  between 
the  eyes ;  and  cannot  call  the  adductor  muscles  into  combined  action  in  per- 
fect darkness,  or  if  the  lids  be  closed.     Even  those  who  have  the  least  power 
of  effecting  this  extreme  convergence,  by  at  once  directing  the  eyes  towards 
a  very  near  object,  can  accomplish  it  by  looking  at  an  object  placed  at  a  mo- 
derate  distance,  and  gradually  bringing  this  nearer  to  the  nose,  keeping  the 
eyes  steadily  fixed  upon  it.     The  unwonted  character  of  the  movement  is 
shown  in  this, — that  it  can  only  be  maintained,  even  for  a  short  time,  by  a 
strong  effort,  producing  a  sense  of  fatigue.     No  effort  whatever  can  call  into 
simultaneous  action  the  two   external  Recti ;  and  this  fact  is  an  additional 
proof  of  the  necessity  of  a  guiding  visual  sensation  ;  since  it  is  evident,  that 
no  object  can  ever  be  placed  in  such  a  position,  as  to  require  this  action  for 
the  direction  of  the  axes  of  the  eyes  towards  it. 

6.  Functions  of  the  Cerebellum. 

457.  That  the  Cerebellum  has  some  special  function,  distinct  from  that  of 
the  Cerebral  Hemispheres,  can  scarcely  be  doubted  ;  since  its  peculiar  struc- 
ture and  position,  its  independent  connections  with  the   Medulla  Oblongata, 
and  its  extremely  variable  size  relatively  to  the  remainder  of  the  Encephalon, 
point  it  out  as  an  instrument  adapted  to  some  particular  purpose.     We  shall 
inquire  briefly  into  the  nature  of  the  evidence  respecting  its  function,  which 
is  supplied  to  us  by  Comparative  Anatomy,  by  Experiment,  and  by  Patholo- 
gical phenomena.  A  Cerebellum  is  found  in  all  Vertebrated  animals;  although 
it  is  in  some  extremely  small,  looking  like  a  little  prominence  on  the  Medulla 

30 


350 


FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 


Oblongata.  When  this  is  the  case,  it  is  observed  that  the  whole  mass  is  not 
a  miniature  (so  to  speak)  of  the  large  Cerebellum  of  Man,  but  that  the  central 
portion  (termed  the  vermiform  process)  is  the  part  most  developed;  the  lobes 
not  presenting  themselves  until  the  organ  has  acquired  an  increased  dimension. 
The  following  table,  constructed  from  materials  contained  in  M.  Serres'  most 
valuable  Comparative  Anatomy  of  the  Brain,  will  afford  some  idea  of  the  ma- 
terials for  speculating  on  the  nature  of  the  function  of  the  Cerebellum,  which 
we  obtain  from  this  source.  The  first  column  gives  the  diameter  of  the  Spinal 
Cord,  at  the  second  cervical  vertebra  ;  in  the  two  succeeding  columns  are 
stated  the  transverse  and  the  antero-posterior  diameters  of  the  Cerebellum  ; 
these  dimensions  are  stated  in  hundred-thousandths  of  a  metre.  The  fourth 
column  expresses,  in  round  numbers,  the  proportion  which  the  diameters  of 
the  Cerebellum  bear  to  that  of  the  Spinal  Cord  ;  the  latter  being  reckoned  as  1. 


MAMMALIA. 

Diam.  of  Spinal 
Cord  at  2d  Cervical 
Vertebra. 

Transverse  Diam. 
of  Cerebellum. 

Antero-posterior 
Diameter 
of  Cerebellum. 

Proportions. 

Man     . 

1,100 

12,000 

6,000 

11  —5£ 

Simia  Rubra  . 

900 

4,500 

2,443 

5  —24 

Bear     . 

1,300 

5900 

3,500 

4i-2| 

Dog      . 

1.100 

4,200 

2,525 

3$—  2* 

Dromedary   . 

1,900 

.7,100 

4,600 

3$—  2i 

Kangaroo 

1.200 

3.800 

2^600 

3^-2^ 

BIRDS. 

Falcon  . 

400 

1,350 

1,100 

3£—  2| 

Swallow 

3,175 

500 

600 

3  —  3i 

Turkey  . 

500 

1,350 

1,600 

2f—  24 

Ostrich  . 

700 

1,750 

2,500 

2i—  3i 

REPTILES. 

Crocodile 

300 

500 

400 

If—  li 

Frog     . 

300 

300 

200 

1-t 

FISHES. 

,      ! 

Shark    , 

700 

1,700 

3,100 

2£—  4£ 

Cod      . 

575 

1.350 

1,700 

2i—  3 

Turbot  . 

500 

750 

900 

li-lf 

Lamprey 

275 

225 

100 

t-i 

458.  This  table  affords  us  much  scope  for  interesting  speculation,  and  may 
be  applied  to  the  correction  of  hypotheses  erected  upon  other  foundations. 
Before  we  proceed  to  these,  however,  a  few  general  remarks  may  be  made 
upon  it.  In  the  first  place,  the  proportional  development  of  the  Cerebellum 
is  seen  to  be  smallest  in  the  Vermiform  Fishes,  which  approach  most  nearly 
to  the  Invertebrate ;  but  it  is  much  greater  in  the  higher  Fishes  than  it  is  in 
Reptiles.  If  we  consider  in  what  particular,  that  may  be  reasonably  supposed 
to  have  a  connection  with  this  organ,  the  former  surpass  the  latter,  we  should 
at  once  be  struck  with  their  superiority  in  activity  and  variety  of  movement. 
Passing  on  to  Birds,  we  remark  that  the  average  dimensions  of  the  Cerebel- 
lum greatly  surpass  those  of  the  organ  in  Reptiles  ;  but  that  they  do  not  exceed 
those  occasionally  met  with  in  Fishes.  The  greatest  size  is  not  found  in  those 


FUNCTIONS  OF  THE  CEREBELLUM.  351 

• 

species  which  approach  most  nearly  to  the  Mammalia  in  general  conformation, 
such  as  the  Ostrich;  but  in  those  of  most  active  and  varied  powers  of  flight. 
Lastly,  on  ascending  the  scale  of  Mammiferous  animals,  we  cannot  but  be 
struck  with  the  rapid  advance  in  the  proportional  size  of  the  Cerebellum,  that 
we  observe,  as  we  rise  from  the  lowest,  which  are  surpassed  in  this  respect 
by  many  Birds,  towards  Man,  in  whom  it  attains  a  development  which  appears 
enormous,  even  when  contrasted  with  that  of  the  Quadrumana. 

459.  We  have  next  to  inquire  what  evidence  can  be  drawn  from  Experi- 
mental investigations  on  the  same  subject':  and  in  reference  to  this  it  is  desirable 
to  remark,  in  the  first  place,  that  the  experimental  mode  of  inquiry  is  perhaps 
more  applicable  to  this  organ  than  to  other  parts  of  the  Encephalon ;  inasmuch 
as  it  can  be  altogether  removed,  with  little  disturbance  of  the  actions  imme- 
diately essential  to  life;  and  the  animals  soon  recover  from  the  shock  of  the 
operation,  and  seem  but  little  affected,  except  in  some  easily-recognized  par- 
ticulars.    The  principal  experimenters  upon  this  subject  have  been  Rolando, 
Flourens,  Magendie,  Hertwig,  and  Longet.    It  is  not  to  be  expected,  that  there 
should  be  an  exact  conformity  among  the  results  obtained  by  all.     Every  one 
who  has  been  Engaged  in  physiological  experiments,  is  aware  of  the  amount 
of  difference  caused  by  very  minute  variations  in  their  circumstances;  in  no 
department  of  inquiry  is  this  more  the  case  than  in  regard  to  the  Nervous 
System ;  and  such  differences  are  yet  more  likely  to  occur,  in  experiments 
made  upon  the  Nervous  Centres,  than  in  those  which  concern  their  trunks. — 
The  investigations  of  Flourens  are  the  most  clear  and  decisive  in  their  results ; 
and  of  these  we  shall  accordingly  take  a  general  survey.     He  found  that,  when 
the  Cerebellum  was  mechanically  injured,  the  animals  gave  no  signs  of  sensi- 
bility, nor  were  they  affected  with  convulsions.     When  the  Cerebellum  was 
being  removed  by  successive  slices,  the  animals  became  restless,  and  their  move- 
ments were  irregular ;  and  by  the  time  that  the  last  portion  of  the  organ  was  cut 
away,  the  animals  had  entirely  lost  the  powers  of  springing,  flying,  walking, 
standing,  and  preserving  their  equilibrium, — in  short,  of  performing  any  com- 
bined muscular  movements,  which  are  not  of  a  simply-reflex  character.    When 
an  animal  in  this  state  was  laid  upon  the  back,  it  could  not  recover  its  former 
posture;  but  it  fluttered  its  wings  and  did  not  lie  in  a  state  of  stupor.     When 
placed  in  the  erect  position,  it  staggered  and  fell  like  a  drunken  man, — not,  how- 
ever, without  making  efforts  to  maintain  its  balance.     When  threatened  with  a 
blow,  it  evidently  saw  it,  and  endeavoured  to  avoid  it.     It  did  not  seem  that  the 
animal  had  in  any  degree  lost  voluntary  power  over  its  several  muscles  ;  nor  did 
sensation  appear  to  be  impaired.    The  faculty  of  combining  the  actions  of  the 
muscles  in  groups,  however,  was  completely  destroyed  ;  except  so  far  as  those 
actions  (as  that  of  respiration)  were  dependent  only  upon  the  Reflex  function 
of  the  Spinal  Cord.     The  experiments  afforded  the  same  results,  when  made 
upon  each  class  of  Vertebrated  animals ;  and  they  have  since  been  repeated, 
with  corresponding  effects,  by  Bouillaud  and  Hertwig.    The  latter  agrees  with 
Flourens,  also,  in  stating  that  the  removal  of  one  side  of  the  Cerebellum  affects 
the  movements  of  the  opposite  side  of  the  body;  and  he  further  mentions 
that,  if  the  mutilation  of  the  Cerebellum  have  been  partial  only,  its  function  is 
in  great  degree  restored. 

460.  All  these  results  are  objected  to  by  those  who  assert  that  the  Cerebel- 
lum is  the  seat  of  the  sexual  instinct;  on  the  ground  that  the  observed  aberra- 
tions of  the  motor  functions  are  sufficiently  accounted  for,  by  the  general 
disturbance  which   an  operation  so  severe  must  necessarily  induce.     The 
fallacy  of  this  objection,  however,  is  shown  by  the  fact,  that  the  much  more 
severe  operation  of  removing  the  Hemispheres  does   not  occasion  such  an 
aberration;  the  power  of  performing  the  associated  movements,  and  of  main- 


352  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

• 

taining  the  equilibrium,  being  remarkably  preserved  after  the  loss  of  them 
(§435). 

461.  Upon  comparing  these  results  with  the  preceding  table,  a  remarkable 
correspondence  will  be  observed  between  them.  The  classes  which  have  the 
greatest  variety  of  movements,  and  which  require  for  them  the  most  perfect 
combination  of  a  large  number  of  separate  muscular  actions,  have,  taken  col- 
lectively, the  largest  Cerebellum.  Of  all  classes  of  Vertebrata,  Reptiles  are 
the  most  inert ;  and  their  motions  require  the  least  co-ordination.  The  active 
predaceous  Fishes  far  surpass  them  in  this  respect;  and  may  be  compared 
with  Birds,  in  the  energy  of  their  passage  through  the  water,  and  in  their 
facility  of  changing  their  direction  during  the  most  rapid  progression.  The 
Cerebellum,  accordingly,  bears  to  the  Spinal  Cord  in  them,  very  much  the 
same  proportion  as  it  does  in  Birds.  On  the  other  hand,  the  Flat  Fish,  which 
lie  near  the  bottom  of  the  ocean,  and  which  have  a  much  less  variety  of  move- 
ment, have  a  very  much  smaller  cerebellum  :  and  the  Vermiform  Fishes,  which 
are  almost  all  completely  destitute  of  fins,  and  whose  progression  is  accom- 
plished by  flexion  of  the  body,  have  a  Cerebellum  so  small  as  to  be  scarcely 
discoverable  :  their  motion  being,  like  that  of  the  Articulata,  almost  entirely  of 
a  reflex  character, — each  segment  being  influenced  by  its  own  ganglionic  cen- 
tre, and  the  Spinal  Cord  constituting  by  far  the  largest  proportion  of  the  nervous 
centres.  On  looking  at  the  class  of  Birds,  we  observe  that  the  active  preda- 
ceous Falcons,  and  the  Swift-winged  Swallows  (the  perfect  control  possessed 
by  which  over  their  complicated  movements  must  have  been  observed  by  every 
one),  have  a  Cerebellum  much  larger  in  proportion  than  that  of  the  Gallina- 
ceous birds,  whose  powers  of  flight  are  small,  or  than  that  of  the  Struthious 
tribe,  in  which  they  are  altogether  absent.  Lastly,  on  comparing  its  propor- 
tional size  in  the  different  orders  of  Mammalia,  with  the  number  and  variety 
of  muscular  actions  requiring  combined  movements,  of  which  they  are  respect- 
ively capable,  we  observe  an  even  more  remarkable  correspondence.  In  the 
hoofed  Quadrupeds,  in  which  the  muscular  apparatus  of  the  extremities  is 
reduced  to  its  greatest  simplicity,  and  in  which  the  movements  of  progression 
are  simple,  the  Cerebellum  is  relatively  smaller  than  it  is  found  to  be  in  some 
Birds ;  but  in  proportion  as  the  extremities  acquire  the  power  of  prehension, 
and  together  with  this  a  power  of  application  to  a  great  variety  of  purposes, — 
still  more,  in  proportion  as  the  animal  becomes  capable  of  maintaining  the 
erect  posture,  in  which  a  constant  muscular  exertion,  consisting  of  a  number 
of  most  elaborately-combined  parts,  is  required, — do  we  find  the  size  of  the 
Cerebellum,  and  the  complexity  of  its  structure,  undergoing  a  rapid  increase. 
Thus,  even  between  the  Dog  and  the  Bear  there  is  a  marked  difference  ;  the 
latter  being  capable  of  remaining  for  some  time  in  the  erect  posture,  and  often 
spontaneously  assuming  it ;  whilst  to  the  former  it  is  anything  but  natural. 
In  the  semi-erect  Apes,  again,  there  is  a  very  great  advance  in  the  proportional 
size  of  the  Cerebellum  ;  and  those  which  most  approach  Man  in  the  tendency 
to  preserve  habitually  the  erect  posture,  also  come  nearest  to  him  in  the  di- 
mensions of  this  organ. 

462.  Now  it  is  evident  that  Man,  although  far  inferior  to  many  of  the  lower 
animals  in  the  power  of  performing  various  particular  kinds  of  movement,  far 
surpasses  them  all,  in  the  number  and  variety  of  the  combinations  which  he 
is  capable  of  executing,  and  in  the  complexity  of  the  combinations  themselves. 
Thus,  if  we  attentively  consider  the  act  of  walking  in  man,  we  shall  find  that 
there  is  scarcely  a  muscle  of  the  trunk  or  extremities  which  is  not  actually 
concerned  in  it ;  some  being  engaged  in  performing  the  necessary  movements, 
and  others  in  maintaining  the  equilibrium  of  the  body,  which  is  disturbed  by 
them.  On  the  other  hand,  in  the  horse  or  Camel,  the  muscular  movements 
are  individually  numerous,  but  they  do  not  require  nearly  the  same  perfect 


FUNCTIONS  OF  THE  CEREBELLUM.  353 

co-ordination.  And  in  the  Bird,  the  number  of  muscles  employed  in  the 
movements  of  flight,  and  in  directing  the  course  of  these,  is  really  comparatively 
small;  as  may  at  once  be  perceived,  by  comparing  the  rigidity  of  the  skeleton 
of  the  trunk  of  the  Bird  wi%th  that  of  Man,  and  by  remembering  the  complete 
inactivity  of  the  lower  extremities  during  the  active  condition  of  the  upper. 
In  fact,  the  motions  of  the  wings  are  so  simple  and  regular,  as  to  suggest  the 
idea,  that,  as  in  Insects,  their  character  is  more  reflex  than  directly  voluntary : 
— an  idea  which  is  supported  by  the  length  of  time  during  which  they  can  be 
kept  up  without  apparent  fatigue,  and  also  by  the  important  facts  already  men- 
tioned, which  experimental  research  has  disclosed  (§  435).  It  is  seen,  then, 
that  Comparative  Anatomy  fully  confirms  the  idea,  which  Experimental  physi- 
ology suggests,  respecting  the  chief  functions  of  the  Cerebellum. 

463.  Some  of  Magendie's   experiments  indicate   a  further  connection   of 
this  organ  with  the  motor  function,  the  nature  of  which  is  still  obscure.    This 
physiologist  asserts  that,  if  a  wound  be  inflicted  on  the  Cerebellum,  the  animal 
seems  compelled  by  an  inward  force  to  retrograde  movement,  although  mak- 
ing an  effort  to  advance;  and  that,  if  the  Crus  Cerebelli  on  one  side  be  injured, 
the  animal  is  caused  to  roll  over  towards  the  same  side.     Sometimes  (if  Ma- 
gendie's statements  can  be  relied  on),  the  animals  make  sixty  revolutions  in  a 
minute,  and  continued  this  movement  for  a  week  without  cessation.    Division 
of  the  second  Crus  Cerebelli  restored  the  equilibrium.     Hertwig  observed  the 
same  phenomenon,  when  the  Pons  Varolii  (which  is  nothing  more  than  the 
commissure  of  the  Cerebellum,  surrounding  the  Crura  Cerebri)  was  injured  on 
one  side ;  and  he  has  also  remarked,  that  the  movements  of  the  eyes  were  no 
longer  consensual. 

464.  On  turning  to  Pathology  for  evidence  of  the  functions  of  the  Cerebel- 
lum, we  meet  with  much  that  seems  contradictory.     It  must  be  remembered 
that  a  sudden  effusion  of  blood,  even  to  a  small  extent,  in  any  part  of  the  En- 
cephalon,  is  liable  to  produce  the  phenomena  of  apoplexy  or  paralysis ;  and 
inferences  founded  upon  the  phenomena  exhibited  after  sudden  lesions  of  this 
description  are,  therefore,  much  less  valid,  than  those  based  on  the  results  of 
more  chronic  affections.    In  regard  to  these  last,  however,  it  is  to  be  observed, 
that  we  are  not  yet  in  a  condition  to  be  able  to  state  with  precision,  what 
amount  of  morbid  alteration  in  any  part  of  the  nervous  centres,  is  compatible 
with  but  slightly-disturbed  performance  of  its  function ;  and  that  cases  are 
every  now  and  then  occurring,  which  would  upset  all  our  previous  notions,  if 
we  were  not  aware,  that  the  same  difficulty  presents  itself,  even  in  regard  to 
the  best-established  results  in  Neurology.     It  is  also  to  be  remembered,  that 
the  results  of  disease,  occasioning  pressure,  will  be  peculiarly  liable  to  affect 
the  Medulla  oblongata,  as  well  as  the  Cerebellum ;  and  will  thus  occasion  a 
greater  loss  of  motor  power  than  would  be  occasioned  by  the  mere  suspension 
of  the  function  of  the  latter. 

465.  Pathological   phenomena,  when   examined  with  these   reservations, 
appear  to  coincide  with  the  results  of  experiment,  in  supporting  the  conclu- 
sion, that  the  Cerebellum  is  not  in  any  way  the  instrument  of  psychical  ope- 
rations.    Inflammation  of  the  membranes  covering  it,  if  confined  to  that  part, 
does  not  produce  delirium  ;  and  its  almost  complete  destruction  by  gradual 
softening,  does  not  appear  necessarily  to  involve  loss  of  intellectual  power. 
"But,"  remarks  Andral,  "  whilst  the  changes  of  intelligence  were  variable, 
inconstant,  and  of  little  importance,  the  lesions  of  motion,  on  the  contrary, 
were  observed  in  all  the  cases  [of  softening  which  had  come  under  his  no- 
tice] except  one  ;  and  in  this  it  is  not  quite  certain  that  motion  was  not  inter- 
fered with."     In  general,  apoplexy  of  the  Cerebellum  is  accompanied  by  para- 
lysis ;  but  this  is  by  no  means  usual  in  cases  of  chronic  disease,  in  which 
there  is  rather  an  irregularity  of  movement,  with  a  degree  of  restlessness  re- 

30* 


354  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

sembling  that  described  by  Flourens  as  resulting  from  partial  injury  of  this 
organ.  In  a  few  cases  in  which  both  lobes  of  the  Cerebellum  have  been 
seriously  affected,  the  tendency  to  retrograde  movement  has  been  observed  ; 
and  instances  are  also  on  record,  of  the  occurrence  of  rotatory  movement, 
which  has  been  found  to  be  connected  with  lesion  of  the  Crus  Cerebelli  on 
the  same  side.  So  far  as  they  can  be  relied  on,  therefore,  the  results  of  the 
three  methods  of  investigation  bear  a  very  close  correspondence ;  and  it  can 
scarcely  be  doubted  that  they  afford  us  some  approximation  to  truth. 

466.  We  have  now  to  examine,  however,  another  doctrine  regarding  the 
functions  of  the  Cerebellum,  which  was  propounded  by  Gall,  and  which  is 
supported  by  the  Phrenological  school  of  physiologists.  This  doctrine — 
that  the  Cerebellum  is  the  organ  of  the  sexual  instinct — is  by  no  means  in- 
compatible with  the  other;  and  by  some  it  has  been  held  in  combination  with 
it.  The  greater  number  of  Phrenologists,  however,  regard  this  instinct  as  the 
exclusive  function  of  the  Cerebellum  ;  and  assert  that  they  can  judge  of  its 
intensity,  by  the  degree  of  development  of  the  organ.  We  shall  now  exam- 
ine the  evidence  in  support  of  this  position,  afforded  by  the  three  methods  of 
inquiry  which  have  been  already  indicated.  The  results  of  fair  observation 
as  to  the  comparative  size  of  the  Cerebellum  in  different  animals,  can  scarcely 
be  regarded  as  otherwise  than  very  unfavourable  to  the  doctrine  in  question. 
In  the  greatest  number  of  Fishes,  it  is  well  known  that  no  sexual  congress 
takes  place  ;  the  seminal  fluid  being  merely  effused,  like  any  other  excretion, 
into  the  surrounding  water ;  and  being  thus  brought  into  accidental  contact 
with  the  ova,  of  which  a  large  proportion  are  never  fertilized.  But  there  are 
certain  Fishes,  as  the  Sharks,  Rays  and  Eels,  in  which  copulation  takes  place 
after  the  ordinary  method.  Now  on  contrasting  these  two  groups,  we  find  no 
corresponding  difference  in  the  size  of  the  Cerebellum.  It  is  true  that  this 
organ  is  of  large  size  in  the  Sharks  ;  but  it  is  very  small  in  the  Rays  ;  and 
almost  rudimentary  in  the  Eels  : — in  this  respect  bearing  a  precise  correspond- 
ence with  the  variety  and  complexity  of  their  movements.  Further,  in  many 
ordinary  Fishes,  which  do  not  copulate,  such  as  the  Cod,  the  Cerebellum  is 
not  only  larger,  but  more  complex  in  structure,  than  it  is  in  the  generality  of 
Reptiles,  in  which  the  sexual  instinct  is  commonly  strong  ; — the  whole  spinal 
system  of  the  Frog  possessing,  at  the  season  of  reproduction,  an  extraordinary 
degree  of  excitability,  which  is  evidently  destined  to  aid  in  the  performance 
of  the  function  (§401,  «).  Again,  in  comparing  the  Gallinaceous  Birds, 
which  are  polygamous,  with  the  Raptorial  and  Insessorial  tribes  which  live 
in  pairs,  we  find  that  the  former,  instead  of  having  a  larger  cerebellum,  have 
one  of  inferior  size.  Further  on  looking  at  the  Mammalia,  the  same  dispro- 
portion may  be  noticed.  A  friend  who  kept  some  Kangaroos  in  his  garden, 
informed  the  Author  that  they  were  the  most  salacious  animals  he  ever  saw ; 
yet  their  Cerebellum  is  one  of  the  smallest  to  be  found  in  the  class.  Every 
one  knows,  again,  the  salacity  of  Monkeys  ;  there  are  many  which  are  excited 
to  violent  demonstrations  by  the  sight  even  of  a  human  female;  and  there 
are  few  which  do  not  practise  masturbation,  when  kept  in  solitary  confinement : 
yet  in  them  the  Cerebellum  is  much  smaller  than  in  Man,  in  whom  the  sexual 
impulse  is  much  less  violent.  It  has  been  supposed  that  the  large  size  of  the 
organ  in  Man  is  connected  with  his  constant  possession  of  the  appetite,  which  is 
only  occasional  in  others  ;  but  this  does  not  hold  good;  since  among  domestic 
animals,  there  are  many  which  are  ready  to  breed  throughout  the  year,-— Cats 
and  Rabbits  for  instance ;  and  in  these  we  do  not  find  any  peculiar  difference 
in  the  size  of  the  Cerebellum.  It  is  asserted,  however,  that  the  results,  of 
observation  in  Man  lead  to  a  positive  conclusion,  that  the  size  of  the  Cere- 
bellum is  a  measure  of  the  intensity  of  the  sexual  instinct  in  the  individual. 
This  assertion  has  been  met  by  the  counter-statement  of  others, — that  no 


FUNCTIONS  OF  THE  CEREBELLUM.  355 

such  relation  exists.  It  is  unfortunate  that  here,  as  in  many  other  instances, 
each  party  has  registered  the  observations  favourable  to  their  own  ,views, 
rather  than  those  of  an  opposite  character ;  so  that  until  some  additional 
evidence  of  a  less  partial  nature  has  been  collected,  we  must  consider  the 
question  as  sub  judice.  '  The  Author  is  by  no  means  disposed  to  deny 
that  such  a  correspondence  may  exist;  but  on  contrasting  the  degree  of  sup- 
port which  this  part  of  phrenology  really  derives  from  pathological  evidence, 
with  that  which  the  upholders  of  this  view  represent  it  to  receive,  he  cannot 
but  look  with  much  distrust  at  all  their  observations  on  the  subject. 

467.  It  is  stated  in  Phrenological  works,  as  an  ordinary  result  of  disease 
of  the  Cerebellum,  that  there  is  an  affection  of  the  genital  organs,  manifest- 
ing itself  in  priapism,  turgescence  of  the  testes,  and  sometimes   in  seminal 
emissions.     Now  it  is  quite  true  that,  in  cases  of  apoplexy,  in  which  these 
symptoms  manifest  themselves,  there  is  very  commonly  found  to  be  effusion 
upon  the  Cerebellum  or  in  its  substance  ;  but  it  is  to  be  remembered,  that  in 
all  such  lesions   the  Medulla   Oblongata  is   involved,  and   these   symptoms, 
equally  with  paralysis,  may  be  due  to  affection  of  that  organ.*     Further,  the 
converse  does  not  by  any  means  hold  good ;  for  the  proportion  of  cases  of 
disease  of  the  Cerebellum,  in  which  there  is  any  manifest  affection  of  the 
sexual  organs,  is   really  very  small,  being,  according  to   the  calculations  of 
Burdach,  not  above  one  in  seventeen.     The  same  physiologist  states  that  such 
affections  do  present  themselves,  although  very  rarely,  when  the  Cerebrum  is 
the  seat  of  the  lesion.     A  large  number  of  facts  adduced  by  Phrenologists  in 
support  of  their  views — such  as  the  erections  and  emissions  which  often  take 
place  during  hanging — may  be  explained  as  well,  or  even  better,  on  the  hypo- 
thesis that  the  Cerebro-spinal  axis  (that  is,  the  Spinal  cord  with  the  Medulla 
Oblongata)  is  the  seat  of  this  instinct.     And  this  hypothesis  is  much  more  con- 
formable to  the  results  of  experiment  and  disease,  than  that  which  locates  it  in 
the  Cerebellum.     For  it  has  been  found  that  mechanical  irritation  of  the  Spinal 
Cord,  and  disease  in  its  substance,  much  more  frequently  produce  excitement 
of  the  genital  organs,  than  do  lesions  of  the  Cerebellum.     This  view  is  en- 
tertained by  Miiller,  and  by  most  physiologists  who   have  taken  a  compre- 
hensive and  unbiassed  survey  of  the  phenomena  in  question. 

468.  Among  the  arguments  adduced  by  Gall  and  his  followers  in  proof  of 
the  connection  between  the  Cerebellum  and  the  sexual  instinct,  is  one  which 
would  deserve  great  attention,  if  the  facts  stated  could  be  relied  on.     It  has 
been  asserted,  over  and  over  again,  that  the  Cerebellum,  in  animals  which  have 
been  castrated  when  young,  is  much  smaller  than  in  those  which  have  retained 
their  virility, — being,  in  fact,  atrophied  from  want  of  power  to  act.     Now,  it 
is  unfortunate  that  vague   assertion,  founded  on  estimates  formed  by  the  eye 
from  the  cranium  alone,  is  all  on  which  this  position  rests  ;  and  it  will  be  pre- 
sently shown,  how  very  liable  to  error  such  an  estimate  must  be.     The  fol- 
lowing is  the  result  of  a  series  of  observations  on  this  subject,  suggested  by 
M.  Leuret,t  and  carried  into  effect  by  M.  Lassaigne : — The  weight  of  the 
Cerebellum,  both  absolutely  and  as  compared  with  that  of  the  Cerebrum,  was 
adopted  as  the  standard  of  comparison.     This  was  ascertained  in  ten  Stal- 
lions, of  the  ages  of  from  nine  to   seventeen  years ;  in  twelve  Mares,  aged 

*  A  case  has  been  recently  communicated  to  the  Author,  in  which  the  sexual  desire, 
which  had  been  always  strong  through  life,  but  which  had  been  controlled  within  the  limits 
of  decency,  manifested  itself,  during  a  period  of  some  months  preceding  death,  in  a  most 
extraordinary  degree :  on  post-mortem  examination  a  tumour  was  found  on  the  Pons  Varolii. 
This  fact  harmonizes  with  the  view  given  in  the  text  (§  470),  that  the  sexual  instinct,  if  con- 
nected with  the  Cerebellum  at  all,  has  its  seat  in  the  central  lobe:  but  it  also  corresponds 
equally  well  with  the  idea,  that  the  Medulla  Oblongata  is  its  centre. 

t  Anat.  Comp.  du  Systeme  Nerveaux,  torn,  i.,  p.  427. 


356  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

from  seven  to  sixteen  years ;  and  in  twenty-one  Geldings,  aged  from  seven 
to  seventeen  years.  The  average  weight  of  the  Cerebellum  in  the  Stallions 
was  433  grammes;  the  greatest  being  485  gr.,  and  the  least  (which  was  in  a 
horse  of  ten  years  old)  being  350.  The  average  weight  of  the  Cerebellum 
was  61  gr.  ;  the  greatest  being  65  gr.,  and  the  least  56  gr.  The  average  pro- 
portion borne  by  the  weight  of  the  Cerebellum  to  that  of  the  Cerebrum,  was, 
therefore,  1  to  7*07 ;  the  highest  (resulting  from  a  very  small  Cerebrum)  being 
1  to  6'25 ;  and  the  lowest  (resulting  from  an  unusually  large  Cerebrum)  being 
1  to  7*46.  Throughout  it  might  be  observed,  that  the  variation  in  the  size  of 
the  Cerebellum  was  much  less  than  in  that  of  the  Cerebrum. — In  the  twelve 
Mares,  the  average  weight  of  the  Cerebrum  was  402  gr. ;  the  highest  being 
432  gr.,  and  the  lowest  363  gr.  That  of  the  Cerebellum  was  61  gr. ;  the  high- 
est being  66  gr.,  (which  was  in  the  individual  with  the  smallest  Cerebrum), 
and  the  lowest  58  gr.  The  average  proportion  of  the  weight  of  the  Cerebel- 
lum to  that  of  the  Cerebrum  was  1  to  6'59  ;  the  highest  being  1  to  5'09,  and 
the  lowest  1  to  7.  The  proportion  was,  therefore,  considerably  higher  in  the 
perfect  female,  than  in  the  perfect  male.— In  the  twenty-one  Geldings,  the 
average  weight  of  the  Cerebrum  was  419  gr. ;  the  highest  being  566  gr.,  and 
the  lowest  346  gr.  The  average  of  the  Cerebellum  was  70  gr.  ;  the  highest 
being  76  gr.,  and  the  lowest  64  gr.  The  average  proportion  was,  therefore, 
1'to  5*97;  the  highest  being  1  to  5'16,  and  the  lowest  1  to  7*44.  It  is  curi- 
ous, that  this  last  was  in  the  individual  which  had  the  largest  Cerebellum  of 
the  whole  ;  but  the  proportional  weight  of  the  Cerebrum  was  still  greater. 

4Q9.  Bringing  together  the  results  of  these  observations,  they  are  found  to 
be  quite  opposed  to  the  statement  of  Gall.  The  weight  of  the  Cerebrum, 
reckoning  the  Cerebellum  as  1,  is  thus  expressed  in  each  of  the  foregoing  de- 
scriptions of  animals : — 

Average.  Highest.  Lowest. 

Stallions         ....        7-07  7-46  6-25 

Mares            ....        6-59  .       7-00  5;09 

Geldings        .         .         .         .5-97  7-44  5:16 

The  average  proportional  size  of  the  Cerebellum  in  Geldings,  therefore,  is  so 
far  from  being  less  than  that  which  it  bears  in  entire  Horses  and  Mares,  that 
it  is  positively  greater ;  and  this  depends  not  only  on  diminution  in  the  rela- 
tive size  of  the  Cerebrum,  but  on  its  own  larger  dimension,  as  the  following 
comparison  of  absolute  weights  will  show : — 

Average.  Highest.  Lowest. 

Stallions 61  65  56 

Mares  ....         61  66  58 

Geldings         ....         70  76  64 

The  difference  is  so  remarkable,  and  appears,  from  examination  of  the  indi- 
vidual results,  to  be  so  constant,  that  it  cannot  be  attributed  to  any  accidental 
circumstance,  arising  out  of  the  small  number  of  animals  experimented  on. 
The  average  weight  of  the  Cerebellum  in  the  ten  Stallions  and  twelve  Mares, 
is  seen  to  be  the  same  ;  and  the  extremes  differ  but  little  in  the  two ;  whilst 
the  average  in  the  Gelding  is  more  than  one-seventh  higher,  and  the  lowest  is 
considerably  above  the  average  of  the  preceding,  while  the  highest  far  exceeds 
the  highest  amongst  the  entire  Horses.  It  is  curious  that  Gall  would  have 
been  much  nearer  the  truth,  if  he  had  said  that  the  dimensions  of  the  Cere- 
brum are  usually  reduced  by  castration ;  for  it  appears  from  the  following 
table  that  this  is  really  the  case  :— 

Average.  Greatest.  Least. 

Stallions         ....         433  485  350 

Mares  ....         402  432  336 

Geldings        ....        419  566  346 


FUNCTIONS  OF  THE  CEREBRUM.  357 

The  weight  of  the  largest  Cerebrum  of  the  Gelding  is  far  above  the  highest  of 
the  Stallions  ;  but  it  seems  to  be  an  extraordinary  case,  as  in  no  other  was  the 
weight  above  490  gr.  If  this  one  be  excluded,  the  average  will  be  reduced 
still  further,  being  then  about  412 ;  this  may  be  seen,  by  looking  over  the 
whole  table,  to  give  a  very  fair  idea  of  the  usual  weight  in  these  animals, 
which  is  therefore  less,  by  about  one-twentieth,  than  the  average  of  the  Stal- 
lions.— The  increased  size  of  the  Cerebellum  in  Geldings  may  perhaps  be 
accounted  for  by  remembering  that  this  class  of  horses  is  solely  employed 
for  its  muscular  power,  and  that  the  constant  exercise  of  the  organ  is  not  un- 
likely to  develop  its  size ;  whilst  Stallions,  being  kept  especially  for  the  pur- 
pose of  propagation,  are  much  less  applied  to  occupations  which  call  forth 
their  motor  faculties. 

470.  The  Author  is  far  from  denying  in  toto,  that  any  peculiar  connection 
exists  between  the  Cerebellum  and  the  Genital  system  ;  but  if  the  evidence 
at  present  adduced  in  support  of  the  Phrenological  position  be  held  sufficient 
to  establish  it,  in  defiance  of  so  many  opposing  considerations,  we  must  bid 
adieu  to  all  safe  reasoning  in  Physiology.     The  weight  of  testimony  appears 
to  him  to  be  quite  decided,  in  regard  to  the  connection  of  the  Cerebellum  with 
the  regulation  of  the  motor  function.     How  far  this  invalidates  the  moderate 
phrenological  view,  which  does  not  regard  the  function  of  the  Cerebellum  as 
exclusively  devoted  to  the  sexual  instinct,  is  a  question  well  deserving  of  at- 
tention.    There  is  nothing  opposed  to  such  an  idea  in  the  results  of  the  ex- 
periments already  adverted  to  (§  459)  ;  since  there  is  no  evidence  that  sexual 
instinct  remained  after  the  removal  of  the  Cerebellum  ;  but,  on  the  other  hand, 
there  is   no  proof  that  it  was  destroyed.     A  circumstance  which  has  been 
several  times  mentioned  to  him, — that  great  application  to  gymnastic  exercises 
diminishes  for  a  time  the  sexual  vigour,  and  even  totally  suspends  desire, — 
seems  worthy  of  consideration  in  reference  to  such  a  view.    If  the  Cerebellum 
be  really  connected  with  both  kinds  of  functions,  it  does  not  seem  unreasona- 
ble that  the  excessive  employment  of  it  upon  one  should  dimmish  its  energy 
in  regard  to  the  other.     Further,  it  would  seem  by  no  means  improbable,  that 
the  Lobes  are   specially  connected  with  the  regulation  and  co-ordination  of 
movements ;  whilst  the  Vermiform  processes,  which  are  very  large  in  many 
animals  in  which  the  former  scarcely  present  themselves,  are  the  parts  con- 
nected with  the  sexual  function.     As  an  additional  argument  in  favour  of  the 
former  part  of  this  view,  it  may  be  stated,  that  in  Man  the  lobes  bear  a  larger 
proportion  to  the  Vermiform  processes  than  in  any  other  animal ;  and  that 
they  undergo  their  most  rapid  development  during  the  first  few  years  of  life, 
when  a  large  number  of  complex  voluntary  movements  are  being  learned  by 
experience,  and  are  being  associated  by  means  of  the   muscular  sensations 
accompanying  them :  whilst  in  those  animals  which  have,  immediately  after 
birth,  the  power  of  regulating  their  voluntary  movements  for  definite  objects, 
with  the  greatest  precision,  the  Cerebellum  is  more  fully  developed  at  the 
time  of  birth.     In  both  instances  it  is  well  formed  and  in  active  operation  (so 
far  as  can  be  judged  of  by  the  amount  of  circulation  through  it),  long  before 
the  sexual  instinct  manifests  itself  in  any  perceptible  degree. 

7.  Functions  of  the  Cerebrum. 

471.  We  come,  in  the. last  place,  to  consider  the  functions  of  that  portion 
of  the  Nervous  Centres,  \fhich  is  evidently,  in  Man,  the  predominant  organ 
of  his  whole  system  ;  being  not  merely  the  instrument  of  his  reasoning  facul- 
ties, but  also  possessing  a  direct  or  indirect  control  over  nearly  all  the  actions 
of  his  corporeal  frame,  save  those  purely  vegetative  processes,  which  are  most 


358  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

completely  isolated  from  his  animal  powers.  We  should  be  in  great  danger, 
however,  of  coming  to  an  erroneous  conclusion  as  to  the  real  character  of  the 
Cerebrum  and  of  its  operations,  if  we  confined  ourselves  to  the  study  of  the 
Human  organism ;  and  the  history  of  Physiological  science  shows,  that  every 
advance  of  knowledge  respecting  its  functions,  has  tended  to  limit  them,  whilst 
at  the  same  time  rendering  them  more  precise.  Thus  the  Brain  (this  term,  in 
the  older  Anatomy,  being  chiefly  appropriated  to  the  Cerebrum)  was  accounted, 
not  merely  the  centre  of  all  motion  and  sensation,  but  also  the  source  of  all 
vitality ;  the  different  processes  of  nutrition,  secretion,  &c.,  being  maintained, 
it  was  supposed,  by  a  constant  supply  of  "  animal  spirits,"  propagated  from 
the  brain,  along  the  nerves,  to  each  individual  part.  The  more  modern  doc- 
trine, that  the  Sympathetic  System  has  for  its  special  function  to  supply  the 
nervous  influence  requisite  for  the  maintenance  of  the  functions  of  Organic 
life,  was  the  first  step  in  the  process  of  limitation  ;  still  the  Brain  was  regarded 
as  the  centre  of  all  the  Animal  functions  ;  and  no  other  part  was  admitted  to 
possess  any  power  independently  of  it.  By  experiments  and  pathological 
observations,  however,  the  powers  of  the  Spinal  Cord  as  an  independent 
centre  of  action  were  next  established  ;  and  it  was  thus  shown,  that  there  is 
a  large  class  of  motions,  in  which  the  Brain  has  no  concern,  and  that  the  re- 
moval of  the  Cerebral  hemispheres  is  not  incompatible  (even  among  the  higher 
Vertebrata)  with  the  prolonged  maintenance  of  a  sort  of  inert  and  scarcely 
conscious  life.  Still,  it  has  been  usually  maintained,  and  with  great  show  of 
reason,  that  the  Cerebrum  is  the  instrument  of  all  psychical  operations ;  and 
of  all  the  movements  which  could  not  be  assigned  to  the  reflex  action  of  the 
Spinal  Cord.  An  attempt  has  been  made,  however,  in  the  preceding  pages, 
to  show  that  this  view  is  not  altogether  correct ;  and  that  there  is  a  class  of 
actions,  neither  reflex  nor  voluntary,  but  directly  consequent  upon  Sensations 
and  upon  the  instinctive  and  emotional  propensities  associated  with  these, 
which  may  be  justly  assigned  to  certain  ganglionic  centres,  not  less  inde- 
pendent of  the  Cerebrum  than  is  the  Spinal  Cord  itself.  It  has  been  advanced, 
that  the  Cerebrum  must  be  considered  in  the  light  of  an  organ  super  added 
for  a  particular  purpose  or  set  of  purposes,  and  not  as  one  which  is  essential 
to  life ;  that  it  has  no  representative  among  the  Invertebrata  (except  in  a  few 
of  the  highest  forms,  which  evidently  present  a  transition  towards  the  Verte- 
brated  series) ;  and  that,  at  its  first  introduction,  in  the  class  of  Fishes,  it  evi- 
dently performs  a  subordinate  part  in  the  general  actions  of  the  Nervous 
System.  Hence,  whatever  be  the  function,  or  set  of  functions,  we  assign  to 
the  Cerebrum,  we  must  keep  in  view  the  special  character  of  the  organ  ;  and 
must  never  lose  sight  of  the  fact,  that  its  predominance  in  Man  does  not  de- 
prive other  parts  of  their  independent  powers,  although  it  may  keep  the  exer- 
cise of  those  powers  in  check,  and  may  considerably  modify  their  manifesta- 
tions. 

472.  Before  proceeding  to  inquire  into  the  Physiology  of  the  Cerebrum, 
we  may  advantageously  take  notice  of  some  of  the  leading  features  of  its  struc- 
ture.— In  the  first  place,  it  forms  an  exception  to  the  general  plan,  on  which 
the  elements  of  ganglionic  centres  are  arranged  ;  in  having  its  vesicular  sub- 
stance on  the  exterior,  instead  of  in  the  central  part  of  the  mass.  The  pur- 
pose of  this  is  probably  to  allow  the  vesicular  matter  to  be  disposed  in  such 
a  manner,  as  to  present  a  very  large  surface,  instead  of  being  aggregated  to- 
gether in  a  more  compact  manner  ;  and  by  this  means,  to  admit  the  more 
ready  access,  on  the  one  side,  of  the  blood-vessels* which  are  so  essential  to 
the  functional  operations  of  this  tissue,  as  well  as  the  more  ready  communi- 
cation, on  the  other,  with  the  vast  number  of  fibres,  by  which  its  influence  is 
to  be  propagated.  There  is  no  reason  whatever  to  believe,  that  the  functions 


FUNCTIONS  OF  THE  CEREBRUM.  359 

of  the  vesicular  and  fibrous  substances  are  in  the  least  altered  by  this  change 
in  their  relative  position  ;  indeed  the  results  of  observation  upon  the  pheno- 
mena of  disordered  Cerebral  action  are  such,  as  to  afford  decided  confirmation 
to  the  idea  already  propounded, — that  the  action  of  the  vesicular  matter  con- 
stitutes the  source  of  nervous  power  ;  whilst  the  fibrous  structure  has  for  its 
office,  to  conduct  the  influence  generated  in  the  ^preceding,  towards  the  points 
at  which  it  is  to  operate.  The  purpose  of  this  arrangement  is  further  evi- 
denced by  the  fact,  that,  in  all  the  higher  forms  of  Cerebral  structure,  we  find 
a  provision  for  a  still  greater  extension  of  the  surface,  at  which  the  vesicular 
matter  and  the  blood-vessels  may  come  into  relation  ;  this  being  effected,  by 
the  plication  of  the  layer  of  vesicular  matter  into  "  convolutions,"  into  the 
sulci  between  which,  the  highly  vascular  membrane  known  as  the  pia  mater 
dips  down,  sending  multitudes  of  small  vessels  from  its  inner  surface  into  the 
substance  it  invests. — In  the  fibrous  or  medullary  substance  of  which  the 
great  mass  of  the  Cerebrum  is  composed,  three  principal  sets  of  fibres  may 
be  distinguished.  These  are, — -first,  the  radiating  fibres,  which  connect  the 
vesicular  matter  of  the  cortical  substance  of  the  hemispheres  with  the  Thala- 
mi  Optici,  and  which,  if  our  view  of  the  function  of  the  latter  be  correct, 
may  be  regarded  as  ascending  or  sensory ; — second,  the  radiating  fibres, 
which  connect  the  vesicular  matter  of  the  cortical  substance  of  the  hemi- 
spheres with  the  Corpora  Striata,  and  which,  on  similar  grounds,  may  be  re- 
garded as  descending  or  motor ; — and  third,  the  Commissural  fibres,  which 
establish  the  connection  between  the  opposite  hemispheres,  and  between  the 
different  parts  of  the  vesicular  substance  of  the  same  side,  especially  between 
that  disposed  on  the  surface  of  each  hemisphere,  and  those  isolated  patches 
which  are  found  in  its  interior.  It  is  on  the  very  large  proportion  which 
the  Commissural  fibres  bear  to  the  rest,  that  the  bulk  of  the  Cerebrum  of 
Man  and  of  the  higher  animals  seems  chiefly  to  depend ;  and  it  is  easy  to 
conceive,  that  this  condition  has  an  important  relation  with  the  operations  of 
the  Mind,  whatever  be  our  view  of  the  relative  functions  of  different  parts  of 
the  Cerebrum.  It  appears  from  the  late  researches  of  M.  Baillarger,  that  the 
surface  and  the  bulk  of  the  cerebral  hemispheres  are  so  far  from  bearing  any 
constant  proportion  to  each  other,  in  different  animals,  that,  notwithstanding 
the  depth  of  the  convolutions  in  the  Human  Cerebrum,  its  bulk  is  2|  times 
as  great  in  proportion  to  its  surface,  as  it  is  in  the  Rabbit,  the  surface  of  whose 
Cerebrum  is  smooth.  The  entire  surface  of  the  Human  Cerebrum,  when  the 
convolutions  are  unfolded,  is  estimated  by  him  at  about  670  square  inches.* 

473.  With  regard  to  the  Radiating  fibres,  which  connect  the  Corpora 
Striata  and  Thalami  Optici  with  the  vesicular  surface  of  the  Cerebral  hemi- 
spheres, it  must  be  admitted  that  no  positive  proof  has  yet  been  obtained  of 
their  direct  continuity  with  those,  which  enter  into  the  composition  of  the 
nerves  proceeding  from  the  Spinal  Cord  and  Medulla  Oblongata  ;  and  how- 
ever probable  such  a  continuity  may  be  regarded  on  some  grounds,  there  are 
certain  phenomena,  which  may  perhaps  be  better  explained  on  the  idea,  that 
these  radiating  fibres  are  of  a  Commissural  nature  only,  serving  to  connect  the 
vesicular  matter  of  the  Cerebrum  with  that  of  the  different  portions  of  the  Cranio- 
$pinal  Jlxis  (under  which  term  are  included  the  Spinal  Cord,  the  Medulla 

*  The  inference  drawn  by  M.  Baillarger  from  the  facts  he  has  collected. — namely,  that 
the  proportional  surface  of  vesicular  matter  in  different  animals,  whether  considered  abso- 
lutely, or  relatively  to  the  volume  of  the  Cerebrum,  has  no  correspondence  with  their  intel- 
lectual capability, — is  far  too  sweeping  an  assumption  ;  since,  as  above  shown,  the  increase 
in  the  commissural  fibres,  causing  an  augmentation  of  the  bulk  of  the  Cerebrum,  may  be  alike 
the  cause  of  increased  intelligence  and  of  a  diminished  proportional  amount  of  vesicular  mat- 
ter ;  though  the  latter  still  remains  as  the  original  source  of  power. 


360  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

Oblongata,  and  the  chain  of  Sensory  Ganglia  at  the  summit  of  the  latter), 
and  thus  brought,  through  the  medium  of  the  latter,  into  relation  with  the  cen- 
tral terminations  of  the  afferent  nerves,  and  the  origins  of  the  motor.  On  this 
view,  the  Cerebrum  would  receive  all  its  sensory  impressions,  by  the  commis- 
sural  fibres  that  connect  it  with  the  ganglia,  which  are  the  real  centres  of  these 
nerves  ;  whilst  it  would  call  the  motor  trunks  into  action,  by  exciting,  through 
another  set  of  commissural  fibres,  the  vesicular  matter  of  the  ganglionic  cen- 
tres from  which  they  pass  forth.* — This  question  cannot  be  determined  until 
it  shall  have  been  shown,  whether  there  is,  or  is  not,  a  direct  continuity  be- 
tween any  of  the  fibres  of  the  trunks  connected  with  the  Cranio-Spinal  Axis, 
and  any  of  the  radiating  fibres  of  the  Cerebral  hemispheres.  But  the  latter 
view  is  certainly  favoured  by  the  very  remarkable  fact,  in  which  the  results 
of  all  experiments  agree,  that  no  irritation  or  injury  of  the  Cerebral  fibres 
themselves,  produces  either  sensation  or  motion.  Even  the  Thalami  and  Cor- 
pora Striata  may  be  wounded,  without  the  excitement  of  convulsive  actions ; 
but  if  the  incisions  involve  the  Tubercula  Quadrigemina  or  the  Medulla  Ob- 
longata, convulsions  uniformly  occur.  These  results  are  borne  out  by  patho- 
logical observations  in  Man  ;  for  it  has  been  frequently  remarked,  when  it 
has  beeri  necessary  to  separate  protruded  portions  of  the  Brain  from  the 
healthy  part,  that  this  has  given  rise  to  no  sensation,  even  in  cases  in  which 
the  mind  has  been  perfectly  clear  at  the  time. 

474.  The  Commissural  fibres  constitute  two  principal  groups,  the  trans- 
verse, and  the  longitudinal;  the  former  connecting  the  two  Hemispheres  with 
each  other;  the  latter  uniting  the  different  parts  of  the  same  Hemisphere. — 
Of  the  transverse  commissures,  the  Corpus  Callosum  is  the  most  important. 
This  consists  of  a  mass  of  fibres  very  closely  interlaced  together;  which  may 
be  traced  into  the  substance  of  the  hemispheres  on  each  side,  particularly  at 
their  lower  part,  where  their  connections  are  the  closest  with  the  Thalami 
Optici  and  Corpora  Striata.  It  is  difficult,  if  not  impossible,  to  trace  its  fibres 
any  further;  but  there  can  be  little  doubt  that  they  radiate,  with  the  fibres 
proceeding  from  the  bodies  just  named,  to  different  parts  of  the  cortical  sub- 
stance of  the  Hemispheres.  This  commissure  is  altogether  wanting  in  Fish, 
Reptiles,  and  Birds  ;  and  it  is  partially  or  completely  wanting  in  those  Mam- 
mals, whose  Cerebrum  is  formed  upon  the  least  complex  plan — the  Rodents 
and  Marsupials.  The  anterior  commissure  particularly  unites  the  Corpora 
Striata  of  the  two  sides :  but  many  of  its  fibres  pass  through  those  organs, 
and  radiate  towards  the  convolutions  of  the  Hemispheres,  especially  those  of 
the  middle  lobe.  This  commissure  is  particularly  large  in  those  Marsupials, 
in  which  the  Corpus  Callosum  is  deficient.  The  posterior  commissure  is  a 
band  of  fibres  which  connects  together  the  Thalami  optici;  crossing  over  from 
the  posterior  extremity  of  one  to  that  of  the  other.  Besides  these,  there  are 
other  groups  of  fibres,  which  appear  to  have  similar  commissural  functions, 
but  which  are  intermingled  with  vesicular  substance.  Such  are  the  soft 
commissure,  which  also  extends  between  the  Thalami;  the  Pons  Tarini, 
which  extends  between  the  Crura  Cerebri;  and  the  Tuber  Cinereum,  which 
seems  to  unite  the  optic  tracts  with  the  thalami,  the  corpus  callosum,  the  for- 
nix,  &c.,  and  to  be  a  common  point  of  meeting  for  several  distinct  groups  .of 
fibres. — Of  the  longitudinal  commissures,  some  lie  above,  and  others  below, 
the  Corpus  Callosum.  Upon  the  transverse  fibres  of  that  body,  there  is  a 
longitudinal  tract  on  each  side  of  the  median  line,  which  serves  to  connect 

*  See  Messrs.  Todd  and  Bowman's  Physiological  Anatomy,  Chap.  XL  for  a  fuller  state- 
ment of  this  view,  and  of  the  arguments  in* its  favour.  See  also  the  General  Summary  at 
the  conclusion  of  the  present  Chapter. 


FUNCTIONS  OF  THE  CEREBRUM.  361 

the  convolutions  of  the  anterior  and  posterior  Cerebral  lobes.  Above  this, 
again,  is  the  superior  longitudinal  commissure,  which  is  formed  by  the  fibrous 
matter  of  the  great  convolutions  nearest  the  median  plane  on  the  upper  sur- 
face of  the  Cerebrum,  and  which  connects  the  convolutions  of  the  anterior  and 
middle  lobes  with  those  of  the  posterior.  Beneath  the  Corpus  Callosum,  we 
find  the  most  extensive  of  all  the  longitudinal  commissures,  the  Fornix.  This 
is  connected  in  front  with  the  Thalami  optici,  the  Corpora  mammillaria,  the 
tuber  cinereum,  &c. ;  and  behind  it  spreads  its  fibres  over  the  hippocampi 
(major  and  minor),  which  are  nothing  else  than  peculiar  convolutions  that 
project  into  the  posterior  and  descending  cornua  of  the  lateral  ventricles. 
The  fourth  longitudinal  commissure  is  the  Tsenia  semicircularis,  which 
forms  part  of  the  same  system  of  fibres  with  the  fornix ;  connecting  the  cor- 
pus mammillare  and  thalamus  opticus  of  each  side  with  the  middle  lobe  of 
the  cerebral  hemisphere.  If,  as  Dr.  Todd  has  remarked,*  we  could  take 
away  the  corpus  callosum,  the  grey  matter  of  the  internal  convolution,  and 
the  ventricular  prominence  of  the  optic  thalami,  then  all  these  commissures 
would  fall  together,  and  would  become  united  in  the  same  series  of  longitu- 
dinal fibres. — Experiment  does  not  throw  any  light  upon  the  particular  func- 
tions of  the  Corpus  Callosum  and  other  Commissures;  since  they  can 
scarcely  be  divided  without  severe  general  injury.  It  would  appear,  how- 
ever, that  the  partial  or  entire  absence  of  these  parts,  reducing  the  Cerebrum 
(in  this  respect  at  least)  to  the  level  of  that  of  the  Marsupial  Quadruped,  or  of 
the  Bird,  is  by  no  means  an  unfrequent  cause  of  deficient  intellectual  power. 

a.  The  following  case  of  deficient  commissures,  lately  recorded  by  Mr.  Paget,  is  of  much 
interest.  The  middle  portion  of  the  Fornix,  and  the  whole  of  the  Septum  Lucidum,  were 
absent;  and  in  place  of  the  Corpus  Callosum,  there  was  only  a  thin  fasciculated  layer  of 
fibrous  matter,  1/4  inch  in  length,  but  of  which  the  fibres  extended  to  all  the  parts  of  the  brain, 
into  which  the  fibres  of  the  healthy  corpus  callosum  can  be  traced.  The  Middle  commissure 
was  very  large ;  and  the  lateral  parts  of  the  Fornix,  with  the  rest  of  the  Brain,  were  quite 
healthy.  The  patient  was  a  servant-girl,  who  died  of  pericarditis.  She  had  displayed,  during 
her  life,  nothing  very  remarkable  in  her  mental  condition,  beyond  a  peculiar  want  of  forethought, 
and  power  of  judging  of  the  probable  event  of  things.  Her  memory  was  good ;  and  she  possessed 
as  much  ordinary  knowledge  as  is  commonly  acquired  by  persons  in  her  rank  of  life.  She 
was  of  good  moral  character,  trustworthy,  and  fully  competent  to  all  the  duties  of  her  station, 
though  somewhat  heedless ;  her  temper  was  good,  and  disposition  cheerful.  The  mental  de- 
ficiencies in  the  few  other  cases  of  which  the  details  have  been  recorded,  seem  to  have  been 
of  the  same  order;  and  this  is  exactly  what  might  have  been  anticipated;  since  the  depriva- 
tion of  these  parts  takes  away  that,  which  is  most  characteristic  of  the  Cerebrum  of  Man  and 
of  the  higher  Mammalia;  and  their  intellectual  operations  are  peculiarly  distinguished  by  that 
application  of  past  experience  to  the  prediction  of  the  future,  which  constitutes  the  highest  effort 
of  Intelligence. 

475.  The  weight  of  the  entire  Encephalon  in  the  adult  Male  usually  ranges 
between  46  and  53  ounces;  and  in  the  Female,  from  41  to  47  ounces.  The 
maximum  of  the  healthy  brain  seems  to  be  about  64  ounces,  or  four  pounds; 
and  the  minimum  about  31  oz.,  or  something  less  than  two  pounds.  But  in 
cases  of  idiocy,  the  amount  is  sometimes  much  below  this;  as  low  a  weight 
as  20  oz.  having  been  recorded.  It  appears,  from  the  recent  investigations 
of  M.  Bourgery,  that  the  relative  sizes  of  the  different  component  elements 
of  the  Human  Encephalon  are  somewhat  as  follows.  Dividing  the  whole 
into  204  parts,  the  weight  of  the  Cerebrum  will  be  represented  by  about  170 
of  those  parts,  that  of  the  Cerebellum  by  21,  and  that  of  the  Medulla  Oblon- 
gata  with  the  Optic  Thalami  and  Corpora  Striata  at  13.  The  weight  of  the 
Spinal  Cord  would  be,  on  the  same  scale,  7  parts.  Hence  the  Cerebral  He- 
mispheres of  Man  include  an  amount  of  nervous  matter,  which  is  four  times 

*  Anatomy  of  the  Brain,  Spinal  Cord,  &c.,  p.  234. 
31 


362  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

that  of  all  the  rest  of  the  Cerebro-spinal  mass,  more  than  eight  times  that  of 
the  Cerebellum,  thirteen  times  that  of  the  Medulla  Oblongata,  &c.,  and  twenty- 
four  times  that  of  the  Spinal  Cord. — The  average  weight  of  the  whole  En- 
cephalon,  in  proportion  to  that  of  the  body,  in  Man,  taking  the  average  of  a 
great  number  of  observations,  is  about  1  to  36.  This  is  a  much  larger  propor- 
tion than  that  which  obtains  in  most  other  animals;  thus  the  average  of  Mam- 
malia is  stated  by  M.  Leuret  to  be  1  to  186,  that  of  Birds  1  to  212,  that  of 
Reptiles  1  to  1321,  and  that  of  Fishes  1  to  5668.  It  is  interesting  to  remark, 
in  reference  to  these  estimates,  that  the  Encephalic  prolongation  of  the  Me- 
dulla Oblongata  in  Man  (being  about  one-sixteenth  of  the  weight  of  the  whole 
Encephalon)  is  alone  more  than  twice  as  heavy  in  proportion  to  his  body,  as 
the  entire  Encephalon  of  Reptiles,  and  ten  times  as  heavy  as  that  of  Fish. — 
But  there  are  some  animals  in  which  the  weight  of  the  Encephalon  bears  a 
higher  proportion  to  that  of  the  body  than  it  does  in  Man ;  thus  in  the  Blue- 
headed  Tit,  the  proportion  is  as  1  to  12,  in  the  Goldfinch  as  1  to  24,  and  in 
the  Field-Mouse  as  1  to  31.  It  does  not  hence  follow,  however,  that  the  Ce- 
rebrum is  larger  in  proportion ;  in  fact,  it  is  probably  not  nearly  so  large  ;  for 
in  Birds  and  Rodentia,  the  sensory  ganglia  form  a  very  considerable  propor- 
tion of  the  entire  Encephalon.  The  importance  of  distinguishing  between  the 
several  parts  of  this  mass,  which  are  marked  out  as  distinct,  alike  by  their 
structure  and  connections,  as  by  the  history  of  their  development,  has  not  been 
by  any  means  sufficiently  attended  to. 

476.  The  Encephalon  altogether  receives  a  supply  of  Blood,  the  amount 
of  which  is  very  remarkable,  when  its  comparative  bulk  is  considered ;  the 
proportion  which   it  receives   being,  according  to  the   estimate  of  Haller,  as 
much  as   one-fifth  of  the  whole.     The  manner  in  which  this   blood  is  con- 
veyed to  the  Brain,  and  the  conditions  of  its  distribution,  offer  some   pecu- 
liarities worthy  of  notice.     The  two  Vertebral  and  two  Carotid  arteries,  by 
which  the  blood  enters  the  cavity  of  the  cranium,  have  a  more  free  communi- 
cation by  anastomosis,  than  any  similar  set  of  arteries  elsewhere ;  and  this  is 
obviously  destined   to  prevent  an  obstruction  in  one  trunk  from  interrupting 
the  supply  of  blood  to  the  parts,  through  which  its  branches  are  chiefly  dis- 
tributed,— the   cessation  of  the  circulation   through  the  nervous  matter  being 
immediately  productive    (as  formerly   shown,  §  290)   of   suspension  of  its 
functional  activity. — Not  only  must  there  be  a  sufficient  supply  of  blood,  but 
it  must  make  a  regulated   pressure   on  the  walls  of  the  vessels.     Now  the 
Encephalon  is  differently  circumstanced  from  other  vascular  organs,  in  being 
inclosed  within  an  unyielding  bony  case ;  and  it  has  been  supposed  that  the 
total  amount  of  blood  circulating  through  it  must  consequently  be  invariable, 
any  disturbance  of  the   circulation  being  due  to   an  undue  turgidity  of  the 
arteries  and  corresponding  emptiness  of  the  veins,  or  vice  versa.     But  this  is 
by  no  means  the  case ;  for,  independently  of  the  fact  that  varying  states  of 
functional  activity  will  doubtless  produce  a  considerable  variation  in  the  entire 
bulk  of  the  nervous  mass,  we  find  a  special  provision  for  equalizing  the  bulk 
of  the  contents  of  the  cranial  cavity,  and  for  counterbalancing  the  results  of 
differences  in  the  functional   activity  of  the  brain  and  in  its  supply  of  blood. 
This   is   the   existence   of  a  fluid,  which  is  found  beneath  the   arachnoid, 
wherever  pia  mater  exists   in   connection  with  the  brain  and  spinal   cord; 
whether  on  the  surfaces  of  these  organs,  or  in  the  ventricles  of  the  latter. 
The  amount  of  this  fluid  seems  to  average  about  two  ounces ;  but  in  cases  of 
atrophy  of  the  brain,  as  much  as  twelve   ounces  of  fluid  may  sometimes  be 
obtained  from  the  cranio-spinal  cavity ;  whilst  in  all  instances,  in  which  the 
bulk  of  the  brain  has  undergone  an  increase,  whether  from  the  production  of 
additional  nervous  tissue,  or  from  undue  turgescence  of  the  vessels,  there  is 


FUNCTIONS  OF  THE  CEREBRUM.  363 

either  a  diminution  or  a  total  absence  of  this  fluid.  It  appears  from  the  ex- 
periments of  Magendie  (to  whom  our  knowledge  of  the  importance  of  this 
fluid  is  chiefly  due),  that  its  withdrawal  in  living  animals  causes  great  dis- 
turbance of  the  cerebral  functions,  probably  by  allowing  undue  distention  of 
the  blood-vessels ;  it  is,  however,  capable  of  being  very  rapidly  regenerated ; 
and  its  reproduction  restores  the  nervous  centres  to  their  natural  state. 

477.  As  the   cerebro-spinal  fluid   can  readily  find   its  way  from   the  sub- 
arachnoid  spaces  of  the  cranial  cavity  into  those  of  the   spinal,  and  as  the 
latter  are  distensible,  to  a  very  considerable  extent,  it  evidently  serves  as  an 
equalizer  of  the  amount  of  pressure  within  the  cranial  cavity ;  admitting  the 
distention   or  contraction  of  the  vessels  to  take   place,  within  certain  limits, 
without  any  considerable  change  in  the  degree  of  compression  to  which  the 
nervous  matter  is  subjected.     That  this  uniformity  is  of  the  greatest  import^ 
ance  to  the  functional  exercise  of  the  brain,  is  evident  from  a  few  well-known 
facts.     If  an  aperture  be  made  in  the  skull,  and  the  protruding  portion  of  the 
brain  be  subjected  to  pressure,  the  immediate  suspension  of  the  activity  of 
the  whole  organ  is  the  result ;   in  this  manner,  a  state   resembling  profound 
sleep  can   be  induced  in  a  moment;    and  the  normal  activity  is  renewed  as 
momentarily,  as  soon  as  the  pressure  is  withdrawn.     This  phenomenon  has 
often  been  observed  in  the  Human  subject,  in  cases  in  which  a  portion  of  the 
cranial  envelope  has  been  lost  by  disease  or  injury.     The  various  symptoms 
of  Cerebral   disturbance,  which   are  due  to  a  state  of  general  Plethora,  are 
evidently  owing  to  an  excess  of  pressure  within  the  vessels;  but  an  undue 
diminution  of  pressure  is  no  less  injurious,  as  appears  from  the  disturbance  in 
the  Cerebral  functions,  which  results  from  the  very  opposite  cause,  namely, 
a  depression  of  the  power  of  the  heart,  or  a  deficiency  of  blood  in  the  ves- 
sels.— It  is   of  peculiar  importance  to  bear  in   mind   the  disturbance  of  the 
Cerebral  functions,  which  is   occasioned  by  internal  pressure,  when  we  are 
endeavouring  to  draw  inferences  from  the  phenomena  presented  by  disease. 

478.  We  shall  now  proceed  with  our  Physiological  inquiry  into  the  func- 
tions of  the  Cerebrum ;  confining  ourselves,  in  the  present  Section,  to  certain 
general  positions,  with  regard  to  which  most  Physiologists  are  agreed ;  and 
referring  to  the  Appendix  for  a  notice  of  the  more  detailed  system  of  Cerebral 
Physiology,  first  propounded  by  Dr.   Gall. — We  shall,  as  before,  apply  to 
Comparative  Anatomy,  to  Experiment,  and  to  Pathology,  for  our  chief  data. 
Any  general  inferences,  founded  only  upon  observation  of  the  phenomena  pre- 
sented by  Man,  must  be  looked  upon  with  suspicion;  since  every  advance  in 
Comparative  Physiology  leads  us  to  perceive,  how  close  is  the  functional  rela- 
tion between  organs,  that  are  really  of  analogous  nature  in  different  classes  of 
animals ;  and  how  necessary,  therefore,  it  is,  to  examine  and  contrast  all  the 
facts  which  we  can  attain  in  regard  to  them,  in  order  to  impart  to  our  con- 
clusions the  utmost  validity  of  which  they  are   capable. — Our  first  general 
proposition  is,  that  the  Cerebrum  is  the  sole  instrument  of  intelligence  ;  by 
which  term  is  implied  the  intentional  adaptation  of  means  to  ends,  in  a  man- 
ner implying  a  perception  of  the  nature  of  both.     The  actions  performed  by 
the  lower   animals   are  often  such,  as  to  leave  us  in  doubt,  whether  they  are 
the  result  of  a  mere  Instinctive  impulse,  or  of  an  Intelligent  adaptation  of 
means  to  ends ;  and  we  are  guided  in  our  determinations,  chiefly  by  the  uni- 
formity of  these  actions,  in  the  several  individuals  of  the  same  species.     If 
we  analyze  any  of  our  own  instinctive  actions,  we  shall  perceive  the  same 
absence  of  design  on  our  own  parts,  as  that  which  we  attribute  to  the  lower 
animals.     No  one  would  assert  that  the  tendency  to  sexual  intercourse  is  the 
result  of  a  knowledge  of  its   consequences,  and  of  a  voluntary  adaptation  of 
means  to  ends  ;  or  that,  if  we  can  imagine  a  man  newly  coming  into  the 


364 


FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 


world  in  the  full  possession  of  all  his  powers,  he  would  wait  to  eat  when 
hungry,  until  experience  had  taught  him  that  the  swallowing  of  food  would 
relieve  the  uneasy  feeling.  It  has  been  already  shown,  that,  in  the  infant, 
the  act  of  sucking  may  be  performed  even  without  a  Cerebrum  (§  386,  c) ; 
and  for  this  and  other  similar  actions,  therefore,  it  is  doubtful  whether  con- 
sciousness is  a  requisite  condition.  Adult  animals,  whose  Cerebral  hemi- 
spheres have  been  removed,  will  eat  food  that  is  put  into  their  mouths,  although 
they  will  not  go  to  seek  it;  and  this  is  the  case  with  many  Human  idiots. 
When  the  functions  of  the  Brain  are  disturbed,  or  in  partial  abeyance,  as  in 
fever,  we  often  see  a  remarkable  return  to  the  instinctive  propensities  in 
regard  to  food ;  and  the  Physician  frequently  derives  important  guidance  as 
to  the  patient's  diet  and  regimen  (particularly  as  to  the  administration  of 
wine),  from  the  inclination  or  disinclination  which  he  manifests. 

479.  The  difference  between  actions  of  a  purely  Instinctive  character,  and 
those  which  rather  result  from  the  Intellectual  faculties  prompted  by  the  in- 
stinctive propensities,  is  well  seen  in  comparing  Birds  with  Insects.     Their 
Instinctive  tendencies  are  of  nearly  the  same  kind ;  and  the  usual  arts  which 
they  exhibit  in  the  construction  of  their  habitations,  in  procuring  their  food, 
and  in  escaping  from  danger,  must  be  regarded  as  intuitive,  on  account  of  the 
uniformity  with  which  they  are  practised  by  different  individuals  of  the  same 
species,  and  the  perfection  with  which  they  are  exercised  on  the  very  first 
occasion.     But  in  the  adaptation  of  their  operations  to  peculiar  circumstances, 
Birds  display  a  variety  and  fertility  of  resource,  far  surpassing  that  which  is 
manifested  by  Insects  ;  and  it  is  not  doubted,  by  those  who  have  attentively 
observed  their  habits,  that  in  such  adaptations  they  are  often  guided  by  real 
Intelligence.     This  must  be  the  case,  for  example,  when  they  make  trial  of 
several  means,  and  select  that  one  which  best  answers  the  purpose  ;  or  when 
they  make  an  obvious  improvement  from  year  to  year  in  the  comforts  of  their 
dwelling ;  or  when  they  are  influenced  in  the  choice  of  a  situation,  bv  pecu- 
liar circumstances,  which,  in  a  state  of  nature,  can  scarcely  be  supposed  to 
affect  them.     The  complete  domesticability  of  many  Birds  is  in  itself  a  proof 
of  their  possessing  a  certain  degree  of  intelligence ;  but  this  alone  does  not 
indicate  the  possession  of  more  than  a  very  low  amount  of  it ;  since  many  of 
the  most  domesticable  animals  are  of  the  humblest  intellectual  capacity,  and 
seem   to  become  attached  to  Man,  principally  as   the  source  on  which  they 
depend  for  the  supply  of  their  animal  wants.     This  is  the  case  with  most 
Herbivorous  quadrupeds,  and  with  Rabbits,  Guinea-pigs,  &c. ;  as  well  as  with 
the  Gallinaceous  Birds. 

480.  The  attachment  which  is  formed  to  Man,  by  certain  Mammalia  of 
higher  orders,  such  as  the  Dog,  the  Horse,  and  the  Elephant,  is  evidently  of 
a  more  elevated  kind,  and  involves  a  much  larger  number  of  considerations. 
The  Intelligence  of  such  animals  is  peculiarly  exhibited  in  their  Educability ; 
— that  is,  in  the  facility  with  which  their  natural  habits  may  be  changed  by 
the  new  influences  to  which  they  are  subjected,  and  the  complication  of  the 
mental  processes  which  they  appear  to  perform  under  their  altered  circum- 
stances.    Their  actions  are  evidently  the  result,  in  many  instances,  of  a  com- 
plex train  of  reasoning,  differing  in  no  essential  respect  from  that  which  Man 
would  perform  in  similar  circumstances ;  so  that  the  epithet,  "half  reason- 
ing," commonly  applied  to  these  animals,  does  not  express  the  whole  truth ; 
for  their  mental  processes  are  of  the  same  kind  with  those  of  Man,  and  differ 
more  in  the  degree  of  control  which  the  animal  possesses  over  them,  than  they 
do  in  their  own  character.     We  have  no  evidence,  however,  that  any  of  the 
lower  animals  have  a  voluntary  power  of  guiding,  restraining,  or  accelerating 
their  mental  operations,  at  all  similar  to  that  which  Man  possesses ;  these 


FUNCTIONS  OF  THE  CEREBRUM.  365 

operations,  indeed,  seem  to  be  of  very  much  the  same  character  as  those 
which  we  perform  in  our  dreams,  different  trains  of  thought  commencing  as 
they  are  suggested,  and  proceeding  according  to  the  usual  laws,  until  some  other 
disturb  them.  Although  it  is  customary  to  regard  the  Dog  and  the  Elephant  as 
the  most  intelligent  among  the  lower  animals,  it  is  not  certain  that  we  do  so 
with  justice;  for  it  is  very  possible  that  we  are  misled  by  that  peculiar  attach- 
ment to  Man,  which  in  them  must  be  termed  an  instinct,  and  which  enters  as 
a  motive  into  a  large  proportion  of  their  actions ;  and  that,  if  we  were  more 
acquainted  with  the  psychical  characters  of  the  higher  Quadrumana,  we  should 
find  in  them  a  greater  degree  of  mental  capability  than  we  now  attribute  to 
them.  One  thing  is  certain, — that,  the  higher  the  degree  of  intelligence 
which  we  find  characteristic  of  a  particular  race, — the  greater  is  the  degree  of 
variation  which  we  meet  with  in  the  characters  of  individuals  ;  thus  every  one 
knows  that  there  are  stupid  Dogs  and  clever  Dogs,  ill-tempered  Dogs  and 
good-tempered  Dogs, — as  there  are  stupid  Men  and  clever  Men,  ill-tempered 
Men  or  good-tempered  Men.  But  no  one  could  distinguish  between  a  stupid 
Bee  and  a  clever  Bee,  or  between  a  good-tempered  Wasp  and  an  ill-tempered 
Wasp,  simply  because  all  their  actions  are  prompted  by  an  unvarying  instinct. 
481.  It  is  important  to  bear  in  mind  the  view  to  which  we  have  been  con- 
ducted,— in  regard  to  the  relative  offices  of  the  vesicular  and  fibrous  matter, — 
when  forming  our  opinions  upon  the  functions  of  the  Cerebrum  in  general,  or 
of  its  several  parts ;  from  the  various  data  supplied  to  us  by  Comparative 
Anatomy,  by  the  comparison  of  the  Cerebra  of  different  individuals  of  the 
Human  race  with  each  other  and  with  their  respective  psychical  manifestations, 
and  by  experimental  and  pathological  inquiry.  For  in  regard  to  the  first  of 
these  sources  it  is  to  be  remarked,  that  the  size  of  the  brain  does  not,  con- 
sidered alone,  afford  a  means  of  judgment  as  to  its  power.  The  quantity  of 
vesicular  matter  on  its  surface  should  rather  be  our  guide ;  and  this  we  may 
judge  of,  not  only  by  the  depth  of  the  layer,  but  by  the  complexity  of  the 
convolutions  by  which  the  surface  is  extended.  In  no  class,  save  in  Mam- 
malia, do  we  find  the  surface  marked  with  convolutions;  and  in  general 
we  do  not  meet  with  that  fissure  between  the  hemispheres,  which  greatly 
increases  the  extent  of  surface.  In  forming  comparisons  as  to  the  con- 
nection between  the  size  of  the  Cerebrum,  and  the  Intelligence,  in  different 
animals,  we  must  not  be  at  all  guided  by  its  simple  proportional  dimensions ; 
since  it  is  very  evident,  that  it  is  rather  the  proportion  of  the  bulk  of  the 
brain  to  that  of  the  whole  body,  upon  which  we  should  found  our  compari- 
son. But  even  this  is  not  altogether  a  safe  guide;  and  many  Physiologists 
have  endeavoured  to  compare  the  size  of  the  brain,  with  the  aggregate  bulk 
of  the  nerves  proceeding  from  it.  This  is  a  much  fairer  measure;  but  it 
cannot  be  taken  without  great  difficulty.  For  all  practical  purposes,  the 
comparison  of  the  bulk  of  the  Cerebrum  with  that  of  the  Spinal  Cord  will 
probably  answer  very  well.  The  following  table,  the  materials  of  which 
are  drawn  from  M.  Serres'  Comparative  Anatomy  of  the  Brain,  exhibits 
the  three  diameters  of  the  Cerebrum  .of  a  number  of  different  animals, 
and  the  diameter  of  the  Spinal  Cord  at  the  second  cervical  vertebra.  The 
last  three  columns  present  in  round  numbers,  the  three  diameters  of  the 
Cerebrum,  reckoning  that  of  the  Spinal  Cord  as  1,  for  the  sake  of  easy  com- 
parison. 

31* 


386 


FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 


Diameter 
of  Spinal 
Cord. 

DIMENSIONS  OF  CEREBRUM. 

Proportional  Dimensions. 

Anti.-post. 

Transv. 

Vertical. 

Man 

1,100 

17,000 

7.500 

9,000 

1—1  5£ 

l-6f 

1—81 

Dolphin 

1,100 

9,500 

5',  8  50 

8,200 

l-9i 

1-H 

1-8* 

Mandril 

950 

8,100 

3,200 

4,900 

1—  8i 

1—3* 

1—5 

Tiger 

1,600 

9,400 

4,250 

6,400 

1—5* 

l-2f 

1—4 

Dromedary 

1,900 

10,500 

5,050 

5,800 

1—  5i 

1—  2f 

1—3 

Kangaroo 

1,200 

5,300 

2,350 

3,800 

l-4f 

1—2 

1-3* 

Vulture 

800 

3,200 

2.200 

1,550 

1—4 

l-2£ 

1—2 

Falcon 

500 

1,900 

1,450 

1,200 

l_3f 

1—3 

•  92 

Swallow 

175 

1,000 

600 

550 

1—  5f 

1—3* 

3T 

Pie 

450 

2,000 

1,400 

1.200 

1—  4f 

1—3 

—  2| 

Turkey 

500 

1,750 

1,250 

1)200 

1—  3£ 

1—2* 

—  2| 

Parroquet 

400 

2,900 

1,400 

1,700 

1—  7i 

1-3* 

—  4i 

Tortoise 

300 

1,600 

500 

1-5* 

i—  H 

Crocodile 

300 

800 

500 

l-2f 

i—  if 

Viper 

200 

600 

300 

1—2 

i—  i* 

Frog 

300 

500 

400 

1-lf 

1—1* 

Shark 

710 

2,300 

1,100 

1—3| 

i—  if 

Cod 

575 

725 

800 

.1—  U 

i—  if 

Lamprey 

275 

400 

300 

1—  li 

i—  U 

Angler 

400 

400 

300 

1—1 

1-2 

i 

482.  As  might  be  expected,  the  Cerebrum  of  Man  bears  by  far  the  highest 
proportion ;  but  this  proportion  is  not  so  large  in  the  transverse  and  vertical 
diameters,  as  in  the  antero-posterior;  in  fact,  in  the  proportion  of  the  vertical 
diameter  the  Cerebrum  of  Man  is  equalled  by  that  of  the  Dolphin,  and  nearly 
so  in  that  of  the  transverse-  diameter.  In  the  complexity  of  the  convolutions, 
however,  and  in  the  thickness  of  the  grey  matter,  the  Cerebrum  of  Man 
far  surpasses  that  of  this  Cetaceous  animal.  In  these  respects  the  higher 
Quadrumana  present  the  nearest  approach  to  it;  but  their  brain  is  much  infe- 
rior in  size.  In  descending  the  scale  of  Mammalia,  there  may  be  observed  a 
gradual  simplification  in  the  general  structure  of  the  Cerebrum,  depending 
upon  a  great  diminution  in  the  amount  of  commissural  fibres ;  until  in  the 
Marsupialia  the  Brain  presents  nearly  the  same  condition  which  it  offers  in 
Birds  (§  361).  These  animals  manifest  a  much  lower  degree  of  Intelligence 
than  many  Birds  evidently  possess;  and  it  is  interesting  to  remark,  that  their 
Cerebral  hemispheres  are  proportionably  smaller  than  those  which  we  find  in 
many  Birds :  the  diminution  in  their  relative  size  not  being  counterbalanced 
(as  it  is  in  some  other  instances)  by  increased  complexity  of  structure.  In 
the  class  of  Birds,  we  observe  that  the  Vulture  and  the  Falcon,  whose  preda- 
ceous  instincts  give  them  a  considerable  amount  of  general  energy,  are  much 
inferior  in  the  size  of  their  brains  to  the  Insessorial  Birds,  which  are  more 
intelligent ;  and  that  of  all,  there  is  none  in  which  the  brain  is  so  proportion- 
ably  large,  as  it  is  in  the  Parrot  tribe,  the  educability  of  which  is  familiar  to 
every  one ;  whilst  the  easily-domesticable,  but  unintelligent  Turkey,  has  a  brain 
of  scarcely  half  the  proportional  size.  The  very  small  size  of  the  Cerebrum 
in  Reptiles  and  Fishes,  completely  harmonizes  with  the  same  view;  these 
animals  presenting  for  the  most  part  but  feeble  indications  of  intelligence. 
Among  Reptiles,  the  Tortoise  has  a  Cerebrum  comparable  in  length  to  that 
of  Birds;  but  its  breadth  and  depth  are  far  less.  The  largest  Cerebra  among 
Fishes  are  found  in  the  Shark  tribe ;  the  superior  intelligence  of  which  is 


FUNCTIONS  OF  THE  CEREBRUM.  367 

well  known  to  those  who  have  had  the  opportunity  of  observing  their  habits  : 
and  it  is  interesting  to  remark,  that  their  surface  occasionally  presents  an  ap- 
pearance of  rudimentary  convolutions. 

483.  Comparative  Anatomy,  then,  fully  bears  out  the  general  doctrine,  that 
the  Cerebrum  constitutes  the  organ  of  Intelligence,  as  distinguished  from  those 
mere  Instincts,  by  which  many  of  the  lower  animals  seem  to  be  almost  en- 
tirely guided.  By  Intelligence,  we  do  not  mean,  however,  the  reasoning 
faculties  only  ;  but  the  combination  of  those  powers  which  are  of  an  educable 
character,  and  which  become  the  springs  of  voluntary  action,  in  varying  pro- 
portions in  different  animals  of  the  same  tribe;  as  distinguished  from  those, 
which  have  more  immediate  relation  to  the  wants  of  the  corporeal  system, 
and  which  are  automatic  and  invariable  in.  the  several  individuals  of  the  same 
species. — This  definition  does  not  leave  out  of  view  the  operation  of  the  Pas- 
sions, Feelings,  and  Emotions;  which  are  all  but  modifications  of  Instinctive 
Propensities,  to  which  different  names  are  assigned.  The  true  character  of 
these,  however,  can  only  be  understood,  by  studying  the  mode  of  their  action 
on  the  bodily  system.  This  action  is  of  two  kinds; — the  one  direct,  irrational 
and  involuntary ; — the  other  indirect,  rational,  and  voluntary.  In  the  former, 
the  action  is  the  immediate  result  of  the  Emotion,  following  closely  upon  the 
Sensation  which  excited  it,  and  consequently  belongs  to  the  Consensual  group 
already  discussed  (Sect.  5) ;  it  is  executed  without  any  consciousness  of  the 
purpose  to  be  answered  by  it ;  and  the  power  of  the  Will  is  only  exerted  to  direct 
or  restrain  it.  In  the  latter,  as  will  be  presently  shown  (§  494),  the  action 
is  but  remotely  the  result  of  the  Emotion,  being  altogether  of  the  Intelligent 
class;  it  is  executed  with  a  view  to  a  distinct  purpose,  which  has  been  deter- 
mined on  by  the  reasoning  powers,  and  of  which,  therefore,  the  mind  is  fully 
conscious;  and  it  is  purely  an  act  of  the  Will,  however  strongly  the  Emotions 
may  have  acted  in  supplying  motives  to  it  and  exciting  the  intellectual  powers 
to  action. 

.484.  The  general  inferences  drawn  from  Comparative  Anatomy,  are  borne 
out  by  observation  of  the  Human  species.  When  the  Cerebrum  is  fully 
developed,  it  offers  innumerable  diversities  of  form  and  size,  among  various 
individuals  ;  and  there  are  as  many  diversities  of  character.  It  may  be  doubted 
if  two  individuals  were  ever  exactly  alike  in  this  respect.  That  a  Cerebrum 
which  is  greatly  under  the  average  size,  is  incapable  of  performing  its  proper 
functions,  and  that  the  possessor  of  it  must  necessarily  be  more,or  less  idiotic, 
there  can  be  no  reasonable  doubt.  On  the  other  hand,  that  a  large  well-de- 
veloped Cerebrum  is  found  to  exist  in  persons,  who  have  made  themselves  con- 
spicuous in  the  world  by  their  attainments  or  their  achievements,  may  be  stated 
as  a  proposition  of  equal  generality.  In  these  opposite  cases,  we  witness  most 
distinctly  the  antagonism  between  the  Instinctive  and  Voluntary  powers.  Those 
unfortunate  beings,  in  whom  the  Cerebrum  is  but  little  developed,  are  guided  al- 
most solely  by  their  instinctive  tendencies ;  which  frequently  manifest  them- 
selves with  a  degree  of  strength  that  would  not  have  been  supposed  to  exist; 
and  occasionally  new  instincts  present  themselves,  of  which  the  Human  being 
is  ordinarily  regarded  as 'destitute.*  On  the  other  hand,  those  who  have  obtained 
most  influence  over  the  understandings  of  others,  have  always  been  themselves 
persons  of  strong  intellectual  and  volitional  powers ;  in  whom  the  instinctive 
tendencies  have  been  subordinate  to  the  reason  and  will,  and  who  have  given 
their  whole  energy  to  the  particular  object  of  their  pursuit. — It  is  very  different, 

*  A  remarkable  instance  of  this  has  been  recently  published.  A  perfectly  idiotic  girl,  in 
Paris,  having  been  seduced  by  some  miscreant,  was  delivered  of  a  .child  without  assistance. 
It  was  found  that  she  had  gnawed  the  umbilical  cord  in  two,  in  the  same  manner  as  is  prac- 
tised by  the  lower  animals.  It  is  scarcely  to  be  supposed  that  she  had  any  idea  of  the  object 
of  this  separation. 


368 


FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 


however,  with  those  who  are  actuated  by  what  is  ordinarily  termed  genius ; 
and  whose  influence  is  rather  upon  i\\e  feelings,  than  upon  the  understandings, 
of  those  around  them.  Such  persons  are  often  very  deficient  in  the  power  of 
even  comprehending  the  ordinary  affairs  of  life :  and  still  more  commonly, 
they  show  an  extreme  want  of  judgment  in  the  management  of  them,  being 
under  the  immediate  influence  of  their  passions  and  emotions,  and  not  having 
brought  these  under  the  control  of  their  intelligent  will.  The  life  of  a  genius, 
whether  his  bent  be  towards  poetry,  music,  painting,  or  pursuits  of  a  more 
material  character,  is  seldom  one  which  can  he  held  up  for  imitation.  In 
such  persons,  the  general  power  of  the  mind  being  low,  the  Cerebrum  is  not 
usually  found  of  any  great  size. — The  mere  comparative  size  of  the  Cerebrum, 
however,  affords  no  accurate  measure  of  the  amount  of  mental  power ;  we  not 
unfrequently  meet  with  men  possessing  large  and  well-formed  heads,  whilst 
their  physical  capability  is  not  greater  than  that  of  others,  the  dimensions  of 
whose  crania  have  the  same  general  proportion,  but  are  of  much  less  absolute 
size.  Large  brains,  with  deficient  activity,  are  commonly  found  in  persons  of 
what  has  been  termed  the  phlegmatic  temperament,  in  whom  the  general  pro- 
cesses of  life  seem  in  a  torpid  and  indolent  state  ;  whilst  small  brains  and  great 
activity,  betoken  what  are  known  as  the  sanguine  and  nervous  temperaments. 
These  distinctions  come  to  be  very  important,  where  we  proceed  further  in 
our  inquiries,  and  attempt  to  determine  the  particular  modes  of  development 
of  the  Brain,  which  coincide  with  certain  manifestations  of  the  mind. 

485.  Having  now  inquired  into  the  evidence  of  the  general  functions  of  the 
Cerebrum,  which  may  be  derived  from  examination  of  its  Comparative  deve- 
lopment, we  proceed  to  our  other  sources  of  information ;  Experiment,  and 
Pathological  phenomena.  From  neither  of  these,  however,  is  much  informa- 
tion to  be  derived. — The  effects  of  the  entire  removal  of  the  Cerebral  Hemi- 
spheres have  been  already  stated  (§  435).  So  far  as  any  inferences  can  be 
safely  drawn  from  them,  they  fully  bear  out  the  conclusion,  that  the  Cerebrum 
is  the  organ  of  Intelligence ;  since  the  animals  which  have  suffered  this  muti- 
lation appear  to  be  constantly  plunged  in  a  profound  sleep,  from  which  no 
irritation  ever  seems  able  to  arouse  them  into  full  activity.  It  may  even  be 
argued,  that  the  phenomena  which  they  exhibit  do  not  imply  the  persistence 
of  consciousness;  and  that  this  also  must  be  regarded  as  the  attribute  of  the 
Cerebral  hemispheres,  being  destroyed  by  their  ablation.  But  a  careful  ana- 
lysis of  them  seems  to  show,  that  sensibility  still  exists,  although  it  is  much 
deadened;  for' in  no  other  way  can  we  legitimately  explain  the  efforts  made 
by  the  animals  to  balance  themselves  and  maintain  their  position,  which  are  of 
a' much  higher  character  than  the  mere  reflex  movements  exhibited  by  the 
same  animals  after  the  removal  of  the  entire  Encephalon,  and  which  can 
scarcely  be  explained  without  attributing  to  them  a  degree  of  sensation.  That 
their  sensibility  should  be  greatly  blunted,  however,  is  to  be  anticipated  from 
the  fact,  that  it  is  almost  impossible  to  remove  the  Hemispheres,  without  doing 
great  injury  to  the  other  ganglionic  centres,  especially  to  the  Thalami  Optici 
and  Corpora  Striata ;  which,  if  the  preceding  views  be  correct,  form  a  most 
important  part  of  the  Sensori-Motor  apparatus,  and  which,  in  the  experiments 
referred  to,  appear  to  have  been  generally  removed  with  the  Cerebral  Hemi- 
spheres. The  entire  and  permanent  removal  of  all  vascular  pressure,  too, 
which  is  consequent  upon  the  laying-open  of  the  cranial  cavity,  is  another 
source  of  permanent  disturbance  in  the  functions  of  the  parts  which  are  left. — 
So  far  as  they  go,  therefore,  the  results  of  such  experiments  confirm  the  de- 
ductions drawn  from  Comparative  Anatomy,  in  regard  to  the  general  functions 
of  the  Cerebrum  ;  but  we  must  be  careful  not  to  infer  too  much  from  them,  as 
to  the  extent  to  which  the  animal  functions  are  brought  to  a  close  by  the 
operation  in  question.  In  the  most  recent  experiments,  those  of  MM.  Bouil- 


FUNCTIONS  OF  THE  CEREBRUM.  369 

laud  and  Longet,  it  was  the  opinion  of  the  observers,  that  sensibility  was 
retained,  after  the  complete  removal  of  the  Cerebrum ;  although  the  animals 
appeared  unable  to  attach  any  ideas  to  their  sensations.* — The  results  of  par- 
tial mutilations  are  usually,  in  the  first  instance,  a  general  disturbance  of  the 
Cerebral  functions  ;  which  subsequently,  however,  more  or  less  subsides,  leav- 
ing but  little  apparent  affection  of  the  animal  functions,  except  muscular  weak- 
ness. The  whole  of  one  Hemisphere  has  been  removed  in  this  way,  without 
any  evident  consequence,  save  a  temporary  feebleness  of  the  limbs  on  the 
opposite  side  of  the  body,  and  what  was  supposed  to  be  a  deficiency  of  sight 
through  the  opposite  eye.  The  former  was  speedily  recovered  from,  and  the 
animal  performed  all  its  movements  as  well  as  before  ;  the  latter,  however, 
was  permanent,  but  the  pupil  remained  active. — When  the  upper  part,  only, 
of  both  Cerebral  Hemispheres  was  removed  by  Hertwig,  the  animal  was  re- 
duced, for  fifteen  days,  to  nearly  the  same  condition  with  the  one  from  which 
they  had  been  altogether  withdrawn ;  but  afterwards,  sensibility  evidently  re- 
turned, and  the  muscular  power  did  not  appear  to  be  much  diminished. 

486.  The  information  afforded  by  Pathological  phenomena  is  equally  far 
from  being  definite.  Many  instances  are  on  record,  in  which  extensive  dis- 
ease has  occurred  in  one  Hemisphere,  so  as  almost  entirely  to  destroy  it, 
without  either  any  obvious  injury  to  the  mental  powers,  or  any  interruption 
of  the  influence  of  the  mind  upon  the  body.  But  there  is  no  case  on  record 
of  severe  lesion  of  both  hemispheres,  in  which  morbid  phenomena  were  not 
evident  during  life.  It  is  true,  that  in  Chronic  Hydrocephalus,  a  very  remark- 
able alteration  in  the  condition  of  the  Brain  sometimes  presents  itself  which 
might  a  priori  have  been  supposed  destructive  to  its  power  of  activity ; — the 
ventricles  being  so  enormously  distended  with  fluid,  that  the  cerebral  matter 
has  seemed  like  a  thin  lamina,  spread  over  the  interior  of  the  enlarged  cra- 
nium. But  there  is  no  proof  that  absolute  destruction  of  any  part  was  thus 
occasioned  ;  and  it  would  seem  that  the  very  gradual  nature  of  the  change, 
gives  to  the  structure  time  for  accommodating  itself  to  it.  This,  in  fact,  is 
to  be  noticed  in  all  diseases  of  the  Encephalon.  A  sudden  lesion,  so  trifling 
as  to  escape  observation,  unless  this  be  very  carefully  conducted,  will  occasion 
very  severe  symptoms ;  whilst  a  chronic  disease  may  gradually  extend  itself, 
without  any  external  manifestation.  It  will  usually  be  found  that  sudden 
paralysis,  of  which  the  seat  is  in  the  Brain,  results  from  some  slight  effusion 
of  blood  in  the  substance  or  neighbourhood  of  the  Corpora  Striata  ;  whilst, 
if  it  follow  disorder  of  the  Brain  of  long  standing,  a  much  greater  amount  of 
lesion  will  usually  present  itself.  In  either  case,  the  paralysis  occurs  in  the 
opposite  side  of  the  body,  as  we  should  expect  from  the  decussation  of  the 
pyramids  ;  but  it  may  occur  either  in  the  same,  or  on  the  opposite  side  of  the 
face,— the  cause  of  which  is  not  very  apparent.  If  convulsions  accompany 
the  paralysis,  we  may  infer  that  the  Corpora  Quadrig6mina,  or  the  parts  below, 
are  involved  in  the  injury  ;  and  in  this  case  it  is  usually  found,  that  the  con- 
vulsions are  on  the  paralyzed  side  of  the  body, — the  effect  of  the  lesion,  both 
of  the  Cerebrum  and  of  the  Corpora  Quadrigemina,  being  propagated  to  the 
opposite  side,  by  the  decussation  of  the  Pyramids.  Where,  as  not  unfre- 
quently  happens,  there  is  paralysis  of  one  side,  accompanying  convulsions  on 
the  other,  it  is  commonly  the  result  of  a  lesion  affecting  the  base  of  the  Brain 
and  Medulla  Oblongata,  on  the  side  on  which  the  convulsions  take  place  ; — 
here  the  effect  of  the  lesion  has  to  cross  from  the  Brain,  whilst  its  influence 

*  It  is  worthy  of  remark,  also,  that  M.  Flourens,  who  in  the  first  instance  maintained  that 
sensation  is  altogether  destroyed  by  the  removal  of  the  Cerebrum,  has  substituted,  in  the 
Second  Edition  of  his  Researches,  the  word  perception  for  sensation:  apparently  implying  ex- 
actly what  is  maintained  above. — See  §  435. 


370  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

on  the  Medulla  Oblongata  is  shown  on  the  same  side.  Many  apparent  ano- 
malies present  themselves,  however,  which  are  by  no  means  easy  of  expla- 
nation, in  the  present  state  of  our  knowledge. — The  disturbance  of  the  Cere- 
bral functions,  occasioned  by  those  changes  in  its  nutrition  which  are  com- 
monly included  under  the  general  term  of  Inflammation,  presents  a  marked 
diversity  of  character,  according  to  the  part  it  affects.  Thus  it  is  well  known 
that  the  delirium  of  excitement  is  usually  a  symptom  of  inflammation  of  the 
cortical  substance  or  of  the  membranes  of  the  hemispheres.  This,  is  exactly 
•what  might  be  anticipated  from  the  foregoing  premises,  since  this  condition 
is  a  perversion  of  the  ordinary  mental  operations,  which  are  dependent  upon 
the  instrumentality  of  the  vesicular  matter ;  and  it  is  evidently  impossible  for 
the  membranes  to  be  affected  with  inflammation  without  the  nutrition  of  this 
substance  being  impaired,  since  it  derives  all  its  vessels  directly  from  them. 
On  the  other  hand,  inflammation  of  the  fibrous  portion  of  the  Cerebrum  is 
usually  attended  rather  with  a  state  of  torpor  than  with  excitement ;  and  with 
diminished  power  of  the  will  over  the  muscles.  It  is  stated  by  Foville,  that 
in  acute  cases  of  Insanity,  he  has  usually  found  the  cortical  substance  in- 
tensely red,  but  without  adhesion  to  the  membranes  ;  whilst  in  chronic  cases, 
it  is  indurated  and  adherent :  but  where  the  Insanity  has  been  complicated 
with  Paralysis,  he  has  usually  found  the  medullary  portion  indurated  and 
congested. 

487.  The  general  result  of  such  investigations  is,  that  the  Cerebrum  is 
the  organ  through  which  all  those  impressions  are  received  which  give  rise  to 
the  operations  of  the  Intellect;  and  that  it  affords  the  power  of  occasioning 
muscular  contraction,  in  obedience  to  the  influence  of  the  Will,  which  is  the 
result  of  those  operations. — That  all  the  operations  of  the  Intellect  are  ori- 
ginally dependent  upon  the  reception  of  Sensations,  is  a  position  that  can 
scarcely  be  denied.  If  it  were  possible  for  a  Human  being  to  come  into  the 
world,  with  a  Brain  perfectly  prepared  to  be  the  instrument  of  mental  opera- 
tions, but  with  all  the  inlets  to  sensation  closed,  we  have  every  reason  to  be- 
lieve that  the  Mind  would  remain  dormant,  like  a  seed  buried  deep  in  the 
earth.  For  the  attentive  study  of  cases,  in  which  there  is  congenital  defi- 
ciency of  one  or  more  sensations,  makes  it  evident  that  the  Mind  is  uttterly 
incapable  of  forming  any  definite  ideas,  in  regard  to  those  properties  of  ob- 
jects, of  which  those  sensations  are  particularly  adapted  to  take  cognizance. 
Thus  the  man  who  is  born  blind  can  form  no  conception  of  colour  ;  nor  the 
congenitally-deaf,  of  musical  tones.  And  in  those  lamentable  cases,  in  which 
the  sense  of  touch  is  the  only  one  through  which  ideas  can  be  introduced,  it 
is  evident  that  the  mental  operations  would  remain  of  the  simplest  and  most 
limited  character,  if  the  utmost  attention  be  not  given  by  a  judicious  instructor, 
to  the  development  of  the  intellectual  faculties,  and  the  cultivation  of  the 
moral  feelings,  through  the  restricted  class  of  ideas  which  there  is  a  possi- 
bility of  exciting. — The  activity  of  the  Mind,  then,  is  just  as  much  the  result 
of  its  consciousness  of  external  impressions  by  which  its  faculties  are  called 
into  play,  as  the  Life  of  the  body  is  the  consequence  of  the  excitement  of  its 
several  vital  properties  by  external  stimuli.  If  these  stimuli  are  prevented 
from  acting  in  the  first  instance,  the  state  of  inaction  continues  ;  but  when 
once  the  mind  has  been  aroused,  the  sensations  which  it  receives  are  treasured 
up  by  the  Memory:  and  they  may  thus  continue  to  be  the  sources  of  new 
ideas,  long  after  the  complete  closure  of  the  inlets,  by  which  new  sensations 
are  ordinarily  received.  We  have  remarkable  examples  of  this,  in  the  vivid 
conceptions  which  may  be  formed  from  the  description  of  a  landscape  or  a 
picture,  by  those  who  have  once  enjoyed  sight ;  or  in  the  composition  of 
music,  even  such  as  involves  new  combinations  of  sounds,  by  those  who  have 
become  deaf, — as  in  the  remarkable  case  of  Beethoven.  The  mind  thus 


FUNCTIONS  OF  THE  CEREBRUM.  371 

feeds,  as  it  were,  upon  the  store  which  has  been  laid  up  during  the  activity 
of  its  sensory  organs ;  but  instead  of  diminishing,  like  material  food,  these 
sensations  become  more  and  more  vivid,  the  oftener  they  are  recalled  to  the 
mind. 

488.  But  the  operations  of  the  Intellect  are  immediately  founded,  not  upon 
Sensations,  but  upon  the  Ideas  they  excite  in  the  Mind.*     Some  ideas  are  so 
simple,  and  so  constantly  excited  by  certain  sensations,  that  we  can  scarcely 
do  otherwise  than  attribute  them  to  original  or  fundamental  properties  of  the 
mind,  called  into  activity  by  the  sensations  in  question  ;  others,  however,  are 
of  a  much  more  complex  nature,  and  vary  according  to  the  peculiar  character 
of  the  individual  mind,  the  general  habits  of  thought,  and  its  particular  condi- 
tion at  the  time.     In  either  case,  the  formation  in  the  mind  of  an  elementary 
notion  respecting  the  object  of  the  Sensation,  is  the  first  operation  in  which 
the  Cerebrum  can  be  said  to  be  necessarily  concerned,  and  is  introductory  to 
all  the  rest.    The  process,  whether  simple  or  complex,  is  termed  Perception; 
and  the  designation  is  applied,  like  Secretion,  not  merely  to  the  act,  but  to  its 
result, — being  used  to  indicate  the  notion  thus  produced,  whether  it  be  simple 
and  directly-excited,  or  more  complex  and  the  result  of  a  succession  of  mental 
operations. 

489.  The  difference  between  Perception  and  Sensation  maybe  easily  made 
evident.     In  order  that  a  sensation  should  be  produced,  a  conscious  state  of 
the  mind  is  all  that  is  required.     Its  whole  attention  may  be  directed  towards 
some  other  object,  and  the  sensation  calls  up  no  new  ideas  whatever ;  yet  it 
will  produce  some  change  in  the  Sensorium,  which  causes  it  to  be  (as  it  were) 
registered  there  for  a  time,  and  which  may  become  the  object  of  subsequent 
attention ;  so  that,  when  the  mind  is  directed  towards  it,  that  idea  or  notion 
of  the  cause  of  the  sensation  is  formed,  which  constitutes  a  perception.     For 
example,  a   student,  who   is  directing  his  thoughts  to  some  object  of  earnest 
pursuit,  does  not  receive   any  intimation  of  the  passage  of  time,  from   the 
striking  of  a  clock  in  his  room.     The  sensation  must  be  produced,  if  there 
be  no  defect  in  his  nervous  system  ;  but  it  is  not  attended  to,  because  the  mind 
is  bent  upon  another  object.    It  may  produce  so  little  impression  on  the  mind, 
as  not  to  recur  spontaneously,  when  the  train  of  thought  which  previously 
occupied  the  mind  has  been  closed,  leaving  the  attention  ready  to  be  directed 
to  any  other  object;  or,  the  impression  having  been  stronger,  it  may  so  recur, 
and  at  once  excite  an  idea  in  the  mind. — Again,  the  individual  may  then  be 
able  only  to  say,  that  he  heard  the  clock  strike ;  or  he  may  be  able  to  retrace 
the  number  of  strokes.     Now,  in  either  case,  a  complex  perception  is  formed, 
without  his  being  aware  that  any  mental  operation  has  intervened.    He  would 
say  that  he  remembers  hearing  the  clock  strike  ;  but  this  would  not  express 
the  truth.     That  which  he  remembers  is  a  certain  series  of  sonorous  impres- 
sions, which  was  communicated  to  his  mind ;  and  he  recognizes  them  as  the 
striking  of  a  clock,  by  a  process   in  which  memory  and  judgment  are  com- 
bined,— which   process  may  further  inform  him,  that  the  sounds  proceeded 
from  his  own  particular  clock.     If  he  had  never  heard  a  clock  strike,  and  the 
sound  produced   by  it  had  never  been  described  to  him,  he  would  not  have 
been  able  to  form  that  notion  of  the  object  giving  rise  to  the  sensation,  which, 
simple  as  it  appears  to  be  at  the  time,  is  the  result  of  complex  mental  opera- 
tions.    But  when  these  operations  have  been  frequently  performed,  the  per- 

*  Some  Metaphysicians  have  spoken  of  ideas  as  transformed  sensations  ;  but  this  is  a  gross 
absurdity.  The  idea  is  excited  by  the  sensation,  in  accordance  with  the  original  properties  of 
the  mind,  and  the  laws  of  their  operation,  just  as  muscular  contraction  is  excited  by  the  sti- 
mulus of  electricity  or  innervation ;  but  it  would  be  just  as  correct  to  speak  of  a  muscular 
contraction  as  transformed  electricity  or  innervation,  because  excited  by  either  of  these  stimuli, 
as  it  is  to  call  an  idea  a  transformed  sensation. 


372  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

ception  or  notion  of  the  object  becomes  inseparably  connected  with  the  sen- 
sation ;  and  thus  it  is  excited  by  the  latter,  without  any  knowledge  on  the 
part  of  the  individual,  that  a  mental  operation  has  taken  place. 

490.  Such  Perceptions  are  termed  acquired,  in  contradistinction  to  the  in- 
tuitive perceptions,  of  which  the  lower  animals  seem  to  possess  a  large  num- 
ber.    The  idea  of  the  distance  of  an  object,  for  example,  is  one  derived  in 
Man  from  many  sources,  and  is  the  result  of  a  long  experience ;  the  infant, 
or  the  adult  seeing  for  the  first  time,  has  to  bring  the  senses  of  sight  and  of 
touch   to   bear  upon  one  another,  in  order  to  obtain  it ;  but,  when  once  the 
power  of  determining  it  is  acquired,  the  steps  of  the  process  are  lost  sight  of. 
In  the  lower  tribes  of  animals,  however,  in  which  the  young  receive  no  assist- 
ance from  their  parents,  there  is  an  evident  necessity  for  some  immediate 
power  of  forming  this  determination ;  since  they  would  not  be  able  to  obtain 
their  food  without  it.     Accordingly,  they  manifest  in  their  actions  a  percep- 
tion or  governing  idea  of  distances,  which  can  only  be  gained  by  Man  after 
long  experience.     A  fly-catcher,  for  instance,  just  come  out  of  its  shell,  has 
been  seen  to  peck  at  an  insect,  with  an  aim  as  perfect  as  if  it  had  been  all  its 
life   engaged  in  learning  the  art. — In  some  cases,  animals  seem  to  learn  that 
by  intuitive  perception,  at  which  Man  could  only  arrive  by  the  most  refined 
processes  of  reasoning,  or  by  the  careful  application  of  the  most  varied  expe- 
rience.    Thus,  a  little  fish,  named  the  Chsetodon  rostratus,  is  in  the  habit  of 
ejecting  from  its  prolonged  snout,  drops  of  fluid,  which  strike  insects  that  hap- 
pen to  be  near  the  surface  of  the  water,  and  causes  them  to  fall  into  it,  so  as 
to  come  within  its  own  reach.     Now,  by  the  laws  of  refraction  of  light,  the 
place  of  the  Insect  in  the  air,  will  not  really  be  that  at  which  it  appears   to 
the  Fish  in  the  water ;  but  it  will  be  a  little  below  its  apparent  place,  and  to 
this  point  the  aim  must  be  directed.     But  the  difference  between  the  real  and 
the  apparent  place  will  not  be  constant ;  for  the  more  perpendicularly  the  rays 
enter  the  water,  the  less  will  be   the  variation ;  and,  on  the  other  hand,  the 
more  oblique  the  direction,  the  greater  will  be  the  difference.     Now  it  is  im- 
possible to  imagine  but  that,  by  an  intuitive  perception,  the  real  place  of  the 
Insect  is  known  to  the  Fish  in  every  instance,  as  perfectly  as  it  could  be  to 
the  most  sagacious  Human  mathematician,  or  to  a  clever  marksman,  who  had 
learned  the  requisite  allowance  in  each  case  by  a  long  experience. 

490*.  In  Man,  the  acquirement  of  perceptions  is  clearly  a  Cerebral  opera- 
tion ;  but  their  intuitional  formation  in  the  lower  animals  is  probably  to  be 
regarded  as  one  of  those  processes  to  which  the  Sensory  ganglia  are  subserv- 
ient. The  same  may  be  said  of  many  of  the  intuitive  perceptions  in  Man ; 
which,  if  analyzed,  are  found  to  be  connected  rather  with  the  instinctive  and 
emotional  tendencies,  than  with  the  intellectual  powers  ; — the  perceptions 
which  minister  to  the  exercise  of  these  last,  being  the  result  of  experience. 
Thus,  it  has  been  well  remarked  by  Dr.  Alison,  that  the  changes  which  Emo- 
tions occasion  in  the  countenance,  gestures,  &c.,  of  one  individual,  are  instinc- 
tively interpreted  by  others  ;  for  these  signs  of  mental  affection  are  very  early 
understood  by  young  children,  sooner  than  any  associations  can  be  supposed 
to  have  been  formed,  by  experience,  of  their  connection  with  particular  modes 
of  conduct ;  and  they  affect  us  more  quickly  and  strongly,  and  with  nicer 
varieties  of  feeling,  than  when  it  is  attempted  to  convey  the  same  feelings  in 
words,  which  are  signs  addressed  to  the  intellect. 

491.  By  a  certain  retentive  power,  which  appears  to  be  peculiar  to  the 
Cerebrum,  Sensations  and  the  simple  ideas  or  Perceptions  they  excite,  are 
stored  up  (so  to  speak)  in  such  a  manner,  as  to  become  the  subjects  of  further 
mental  operations  at  a  time  more  or  less  remote.     They  then  present  them- 
selves as  renewed  images  of  past  sensations ;  and  these  may  recur,  either 
involuntarily,  or  by  a  special  direction  of  the  mind  towards  them  by  an  effort 


FUNCTIONS  OF  THE  CEREBRUM.  373 

of  Recollection.  In  either  case,  the  Memory  of  them  is  probably  due  to  the 
operation  of  the  principle  of  Association  ;  by  which  sensations  and  the  ideas 
they  excite  become  linked  together,  in  such  a  manner  that  the  recurrence  of 
one  shall  be  the  means  of  the  recal  of  others  which  are  connected  with  it. — 
There  seems  much  ground  for  the  opinion,  that  every  Sensation  actually  ex- 
perienced may  become  the  subject  of  a  Perception  at  any  future  time,  though 
beyond  the  voluntary  power  of  the  memory  to  retrace ;  and  the  phenomena  of 
dreams  and  delirium,  in  which  these  sensations  often  recur  with  extraordinary 
vividness,  afford  much  support  to  this  doctrine.  Some  of  the  instances  upon 
record  are  remarkable,  as  proving  that  the  sensations  may  be  thus  remembered, 
without  any  perceptions  being  attached  to  them  ;  these  sensations  having  been 
of  such  a  nature  as  not  to  excite  any  notion  or  idea  in  the  mind  of  the  indi- 
vidual. A  very  extraordinary  case  of  this  kind  has  been  recorded,  in  which  a 
woman,  during  the  delirium  of  fever,  continually  repeated  sentences  in  lan- 
guages unknown  to  those  around  her,  which  proved  to  be  Hebrew  and  Chal- 
daic ;  of  these  she  stated  herself,  on  her  recovery,  to  be  perfectly  ignorant ;  but 
on  tracing  her  former  history,  it  was  found  that,  in  early  life,  she  had  lived  as 
servant  with  a  clergyman,  who  had  been  accustomed  to  walk  up  and  down 
the  passage,  repeating  or  reading  aloud  sentences  in  these  languages,  which 
she  must  have  retained  in  her  memory  unconsciously  to  herself.  Of  the 
nature  of  the  change,  by  which  sensations  are  thus  registered,,  it  is  in  vain  to 
speculate ;  and  it  does  not  seem  likely  that  we  shall  ever  become  acquainted 
with  it.  This  is  certain,  however, — that  disease  or  injury  of  the  brain  will 
destroy  this  power,  or  will  affect  it  in  various  remarkable  modes.  We  not  un- 
frequently  meet  with  cases  in  which  the  brain  has  been  weakened  by  attacks 
of  epilepsy  or  apoplexy,  in  such  a  manner  as  to  prevent  the  reception  of  any 
neiv  impressions  ;  so  that  the  patient  does  not  remember  anything  that  passes 
from  day  to  day ;  whilst  the  impressions  of  events,  which  happened  long 
before  the  commencement  of  his  malady,  recur  with  greater  vividness  than 
ever.  On  the  other  hand,  the  memory  of  the  long-since-past  is  sometimes 
entirely  destroyed ;  wBilst  that  of  events  which  have  happened  subsequently 
to  the  malady  is  but  little  weakened.  The  memory  ,of  particular  classes  of  ideas 
is  frequently  destroyed ; — that  of  a  certain  language,  or  some  branch  of  science, 
for  example.  The  loss  of  the  memory  of  words  is  another  very  curious 
form  of  this  disorder,  which  is  not  unfrequently  to  be  met  with :  the  patient 
understands  perfectly  well  what  is  said,  but  is  not  able  to  reply  in  any  other 
terms  than  yes  or  wo, — not  from  any  paralysis  of  the  muscles  of  articulation, 
but  from  the  incapability  of  expressing  the  ideas  in  language.  Sometimes  the 
memory  of  a  particular  class  of  words  only,  such  as  nouns  or  verbs,  is  de- 
stroyed ;  or  it  may  be  impaired  merely,  so  that  the  patient  mistakes  the  proper 
terms,  and  speaks  a  most  curious  jargon.  These  cases  have  a  peculiar  interest, 
in  reference  to  the  inquiry  into  the  functions  of  different  parts  of  the  Cere- 
brum. 

492.  To  the  formation  of  vivid  ideas  of  sensible  objects,  whether  these  have 
actually  presented  themselves  in  the  same  form  at  some  previous  time,  or  are 
modifications  of  the  forms  which  had  a  real  existence,  the  term  Conception  is 
applied ;  and  this  designation,  like  Perception,  is  also  applied  to  the  result  of 
the  operation,  that  is,  to  the  idea  which  is  thus  formed.  The  novelty  of  the 
Conception  may  depend  upon  the  new  combination  or  correlation  of  the 
objects  it  includes ;  or  it  may  result  from  a  sort  of  decomposition  of  former 
complex  ideas,  and  the  re-assemblage  of  their  elements  under  a  different  form. 
These  processes,  like  the  Memory,  of  which  they  are  modifications,  may  be 
either  spontaneous  or  voluntary ;  and  in  both  forms  they  are  continually  em- 
ployed by  almost  every  one, — the  tendency  to  the  exact  reproduction  of  former 
32 


374  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

ideas,  however,  being  most  evident  in  some  minds,  whilst  the  tendency  to  the 
modification  of  them  is  more  obvious  in  others.  The  latter  is  one  source  of 
that  faculty,  to  which  the  term  Imagination  is  given. 

493.  The  Mind,  however,  is  not  restricted  to  external  sources,  for  objects 
of  perception ;  since,  when  once  in  activity,  it  perceives  its  own  operations, 
and  traces  the  various  relations  and  connections  among  its  objects  of  thought. 
The  power  of  doing  this  maybe  termed  Internal  Perception.  The  mind 
often  has  internal  perceptions  without  any  direct  effort  of  the  will,  just  as  it 
receives  perceptions  from  external  objects  ;  but  its  power  of  cognizance  is  not 
unfrequently  directed  inwards  by  express  volition ;  and  the  act  is  then  pecu- 
liarly termed  Reflection,  or  perhaps  better,  Introspection. — Now  by  this  pro- 
cess, a  new  class  of  ideas  is  excited,  of  a  very  different  character  from  those 
which  are  called  up  by  external  objects ;  and  these,  being  entirely  dependent 
upon  the  operation  of  the  Intellectual  powers,  and  having  no  dependence  upon 
Sensations  except  as  the  original  springs  of  those  operations,  may  be  termed 
Intellectual  Ideas,  in  contradistinction  to  the  Sensational  Ideas.  The  former, 
like  the  latter,  become  the  subjects  of  the  Associating  tendency;  and  thus  are 
combined  in  Trains  of  Thought.  Some  of  these  intellectual  ideas  appear  to 
be  so  necessarily  excited  by  mental  operations,  even  of  the  simplest  kind,  and 
to  be  so  little  dependent  on  individual  peculiarities  either  inherent  or  acquired, 
that  they  take  rank  as  fundamental  axioms  or  principles  of  Human  Thought. 
Such  are, — the  belief  in  our  own  present  existence,  or  the  faith  which  we  re- 
pose in  the  evidence  of  Consciousness  ;  this  idea  being  necessarily  associated 
with  every  form  and  condition  of  mental  activity, — the  belief  in  our  past  ex- 
istence, and  in  our  personal  identity  so  far  as  our  memory  extends,  which  is 
necessarily  connected  with  the  act  of  Recollection ;  with  this,  again,  is  con- 
nected the  general  idea  of  Space : — the  belief  in  the  external  and  independent 
existence  of  the  causes  of  our  sensations,  which  results  from  Perception,  or 
the  direction  of  the  mind  to  the  ideas  originating  in  them ;  with  this  is  con- 
nected the  general  idea  of  Space : — the  belief  in  the  existence  of  an  efficient 
cause  for  the  changes  which  we  witness  around  us,  which  springs  from  the 
Perception  of  those  changes  ;  whence  is  derived  our  idea  of  Power, — the  be- 
lief in  the  stability  of  the  order  of  nature,  or  in  the  invariable  sequence  of 
similar  effects  to  similar  causes,  which  also  springs  directly  from  the  Percep- 
tion of  external  changes,  and  seems  prior  to  all  reasoning  upon  the  results  of 
observation  of  them  (being  observed  to  operate  most  strongly  in  those  whose 
experience  is  most  scanty,  and  in  relation  to  subjects  that  are  perfectly  new 
to  them) ;  but  which  is  the  foundation  of  all  applications  of  our  own  experience 
or  that  of  others,  to  the  conduct  of  our  lives,  or  to  the  extension  of  our  know- 
ledge : — lastly,  the  belief  in  our  own  free  will,  involving  the  general  idea  of 
Voluntary  Power ;  which  is  in  like  manner  a  direct  result  of  our  Internal 
Perception  of  those  mental  changes  which  are  excited  by  sensations.  Hence 
it  is  evident,  that  "  the  only  foundation  of  much  of  our  belief,  and  the  only 
source  of  much  of  our  knowledge,  is  to  be  found  in  the  constitution  of  our  own 
minds ;"  but  it  must  be  steadily  kept  in  view,  that  these  fundamental  axioms 
are  nothing  else  than  expressions  of  the  general  fact,  that  the  ideas  in  question 
are  uniformly  excited  (in  all  ordinarily-constituted  minds,  at  least)  by  simple 
attention  to  the  changes  in  which  they  originate. 

494.  Upon  the  Sensational  and  Intellectual  Ideas  thus  brought  under  the 
cognizance  of  the  Mind,  all  acts  of  reasoning  are  founded.  These  consist, 
for  the  most  part,  in  the  aggregation  and  collocation  of  ideas  ;  the  decompo- 
sition of  complex  ideas  into  more  simple  ones,  and  the  combination  of  simple 
ideas  into  general  expressions ;  in  which  are  exercised  the  faculty  of  Com- 
parison, by  which  the  relations  and  connections  of  ideas  are  perceived, — that 


FUNCTIONS  OF  THE  CEREBRUM.  375 

of  Abstraction,  by  which  we  fix  our  attention  on  any  particular  qualities  of 
the  object  of  our  thought,  and  isolate  it  from  the  rest, — and  that  of  Generali- 
zation, by  which  we  fix  in  our  minds  some  definite  notions  in  regard  to  the 
general  relations  of  those  objects.  These  are  the  processes  chiefly  concerned 
in  the  simple  acquirement  of  Knowledge ;  with  which  class  of  operations,  the 
Emotional  part  of  our  nature  has  very  little  participation.  But  in  those 
modes  of  exercise  of  our  reasoning  powers,  which  are  chiefly  concerned  in 
the  determination  of  our  actions,  the  Emotions,  &c.,  are  largely  concerned. 
As  formerly  explained  (§  440),  they  chiefly  (if  not  solely)  act  upon  the  reason- 
ing powers,  by  modifying  the  form  in  which  the  ideas  are  presented  to  the 
mind, — whether  these  ideas  are  directly  excited  by  external  sensations,  or 
whether  they  are  called  up  by  an  act  of  the  Memory,  or  result  from  the 
exercise  of  the  Imagination.*  If  we  closely  scrutinize  our  Emotions,  indeed, 
we  shall  find  that  they  consist  chiefly,  if  not  entirely,  of  feelings  of  pleasure 
and  pain,  connected  with  certain  classes  of  ideas ;  the  former  producing  a 
desire  of  the  objects  to  which  they  relate ;  the  latter  a  repugnance  to  them. 
They  thus  have  a  most  important  influence  upon  the  Judgment,  which  is 
formed  by  the  comparison  of  certain  kinds  of  ideas;  and  they  may  conse- 
quently modify  the  Volitional  determination,  or  act  of  the  Will,  which  is  con- 
sequent upon  this,  and  which  may  either  be  directed  towards  the  further 
operations  of  the  mind  itself,  or  may  exert  an  immediate  influence  on  the 
bodily  frame,  by  the  agency  of  the  Nervous  System.  In  either  case,  it  is  the 
characteristic  distinction  of  a  Volitional  operation,  that  means  are  intention- 
ally adapted  to  ends,  in  accordance  with  the  belief  of  the  mind  as  to  their 
mutual  relations.  Upon  the  correctness  of  that  decision,  will  depend  the 
power  of  the  action  to  accomplish  what  the  mind  had  in  view. 

495.  The  faculty  of  Imagination  is  in  some  respects  opposed  in  its  cha- 
racter to  that  of  Reason;  being  concerned  about  fictitious  objects,  instead  of 
real  ones.  Still  it  is  in  a  great  degree  an  exercise  of  the  same  powers,  though 
in  a  different  manner.  Thus  it  is  partly  concerned  in  framing  new  combi- 
nations of  ideas  relating  to  external  objects,  and  is  thus  an  extended  exercise 
of  Conception,— placing  us,  in  idea,  in  scenes,  circumstances,  and  relations, 
in  which  actual  experience  never  placed  us, — and  thus  giving  rise  to  a  new 
set  of  objects  of  thought.  In  fact,  every  Conception  of  that  which  has  not 
been  itself  an  object  of  perception,  may,  strictly  speaking,  be  regarded  as  the 
result  of  the  exercise  of  Imagination.  Now  the  new  Conceptions  or  mental 
creations  thus  formed  take  their  character,  in  great  degree,  from  the  Emo- 
tional tendencies  of  the  mind ;  so  that  the  previous  development  of  particular 
feelings  and  affections  will  influence,  not  merely  the  selection  of  the  objects, 
but  the  mode  in  which  they  are  thus  idealized.  In  the  higher  efforts  of  the 
Imagination,  the  mind  is  concerned,  not  so  much  with  the  class  of  Sensa- 
tional ideas,  but  with  those  of  the  Intellectual  character;  and  the  collocation, 
analysis,  and  comparison  of  these,  by  which  new  forms  of  combinations  are 
suggested  to  the  mind,  involve  the  exercise  of  the  same  powers,  as  those  con- 
cerned in  acts  of  Reasoning, — but  they  are  exercised  in  a  different  way. 
Whilst  the  Imagination  thus  depends  upon  the  Intellectual  powers  for  all  its 
higher  operations,  the  Understanding  may  be  said  to  be  equally  indebted  to 
the  Imagination ;  for  the  ideal  combinations,  which  are  the  results  of  the 
action  of  the  latter,  do  not  merely  engage  the  attention  of  the  Artist,  who 
aims  to  develop  them  in  material  forms,  but  are  the  great  sources  of  the  im- 

*  The  recal  of  past  sensations  and  ideas  may  produce  purely  Emotional  actions  ;  by  ex- 
citing in  the  centres,  from  which  those  actions  proceed,  a  condition  corresponding  with  that 
which  would  be  excited  by  the  present  sensation  (§  439). 


376  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

provement  of  the  knowledge  and  happiness  possessed  by  our  race, — operat- 
ing alike  in  the  common  affairs  of  life,  by  suggesting  those  pictures  of  the 
future  which  are  ever  before  our  eyes,  and  are  our  animating  springs  of  action, 
with  their  visions  of  enjoyment  never  perhaps  to  be  fully  realized,  and  their 
prospects  of  anticipated  evil  that  often  prove  to  be  an  exaggeration  of  the 
reality, — prompting  the  investigations  of  Science,  that  are  gradually  unfolding 
the  sublime  plan  on  which  the  Universe  is  governed, — and  leading  to  a  con- 
tinual aspiration  after  those  highest  forms  of  Moral  and  Intellectual  beauty, 
which  are  inseparably  connected  with  purity  and  love. 

8.   General  Recapitulation  and  Pathological  Applications. 

496.  A  general  Summary  of  the  views  here  propounded,  in  regard  to  the 
Functions  of  the  Cerebro-Spinal  division  of  the  Nervous  system,  may  proba- 
bly be  useful  in  assisting  the  Student  to  gain  clear  ideas  regarding  them. — 
The  fibres  of  the  nervous  trunks  may  be  divided,  according  to  the  direction 
of  their  influence,  into  two  classes, — the  afferent  or  centripetal, — and  the  effe- 
rent or  centrifugal.  The  afferent  may  be  said  to  commence  at  the  periphery, 
especially  on  the  skin,  mucous  surfaces,  &c.,  and  to  terminate  in  the  vesicu- 
lar matter  of  the  nervous  centres  ;  whilst  the  efferent  originate  in  that  vesicu- 
lar matter,  and  terminate  in  the  muscles.*  Every  fibre  runs  a  distinct  course 
from  its  origin  to  its  termination;  and  it  is  not  improbable  that  there  are 
several  distinct  endo\vments  in  the  different  fibres  composing  each  trunk. 
There  is  no  evidence  that  the  fibrous  structure  serves  any  different  purpose 
than  that  of  a  mere  conductor;  and  there  seems  good  reason  to  believe  that 
all  the  active  operations,  of  which  the  nervous  system  is  the  instrument,  ori- 
ginate in  the  vesicular  matter.  A  mass  of  vesicular  matter,  connected  with 
nervous  trunks,  forms  a  ganglion.  In  the  Invertebrata,  the  ganglia  are  fre- 
quently numerous,  and  are  scattered  through  the  system,  without  much  con- 
nection with  each  other ; — each  having  an  independent  action,  although  its 
function  may  be  but  a  repetition  of  that  of  others.  In  Vertebrated  animals, 
on  the  other  hand,  they  are  united  into  one  mass ;  partly,  it  would  seem,  for 
the  sake  of  the  protection  afforded  them  by  the  bony  skeleton ;  and  partly, 
in  order  that  more  complete  consentaneousness  of  action  may  be  attained. 
Still,  certain  divisions  may  be  traced  in  the  central  masses  of  the  Cerebro- 
Spinal  system  ;  both  by  the  determination  of  their  respective  functions,  as 
indicated  by  observation  and  experiment ;  and  by  the  study  of  the  distribution 
of  the  nerves  proceeding  from  them.  In  this  manner  we  arrive  at  the  know- 
ledge of  several  distinct  ganglionic  centres,  of  which  the  following  may  be 
considered  as  a  general  account. 

i.  The  True  Spinal  Cord,  consisting  of  a  nucleus  of  vesicular  matter,  re- 
ceiving afferent  fibres,  and  giving  origin  to  efferent ;  by  these  it  is  connected 
with  all  parts  of  the  body,  but  especially  with  the  surface  and  muscles  of  the 
extremities.  The  actions  of  this  centre  maybe  performed  without  conscious- 
ness on  the  part  of  the  individual ;  and  they  consist  in  the  reflexion  of  a  motor 
impulse  along  an  efferent  nerve,  on  the  reception  of  a  stimulus  conveyed  by  an 
afferent  or  excitor  nerve.  These  reflex  movements  can  be  best  excited,  when 
the  muscles  are  removed  from  the  control  of  the  Will,  which  otherwise  gene- 
rally antagonizes  them.  Some  of  them  are  connected  with  the  maintenance 

*  The  terms  originate,  and  terminate  cannot  be  used  with  strict  correctness;  since,  as  for- 
merly explained  (§  548),  many  fibres  seem  to  have  no  actual  termination,  either  in  the  mus- 
cles or  in  vesicular  matter :  but  they  cease  to  run  in  their  previous  direction,  after  forming 
their  terminal  loops ;  and  their  course  as  afferent  or  efferent  fibres  may  consequently  be  said 
to  begin  or  to  end  at  these  points. 


GENERAL  SUMMARY.  377 

of  the  Organic  functions ;  others  with  locomotion  ;  and  others  with  the  pro- 
tection or  withdrawal  of  the  body  from  injury.  Muscular  movements  may 
also  be  excited  by  a  stimulus  directly  applied  to  the  Spinal  Cord  itself  (§§ 
363—373). 

ii.  The  Medulla  Oblongata,  or  cranial  prolongation  of  the  Spinal  Cord. 
The  actions  of  this  do  not  essentially  differ  from  those  of  the  true  Spinal 
Cord ;  but  they  are  connected  with  different  organs.  This  part  consists 
chiefly  of  the  centres  of  the  nerves  of  Respiration  and  Deglutition, — two 
functions,  of  which  the  continual  maintenance  is  essential  to  the  life  of  the 
being ;  and  it  would  seem  as  if  these  were  placed  within  the  cranium,  to  be 
more  secured  from  accidental  injury.  The  movements  concerned  in  Respira- 
tion and  Deglutition  are,  like  those  excited  through  the  true  Spinal  Cord,  of  a 
strictly  reflex  character,  being  in  all  instances  due  to  an  impression  or  stimulus 
originating  in  the  periphery  of  the  system,  which,  being  conveyed  to  the  cen- 
tre, excites  there  a  motor  impulse  ;  and  they,  also,  are  independent  of  Sensa- 
tion (§§  374—387). 

in.  The  Ganglia  of  the  nerves  of  Sensation,  common  and  special,  which 
form,  as  it  were,  the  continuation  of  the  Medulla  Oblongata.  These  appear 
to  minister  to  actions,  which,  like  the  Reflex,  are  almost  necessarily  excited 
by  certain  stimuli,  and  are  only  in  a  degree  controllable  by  the  Will :  but 
which  differ  from  those  of  which  the  Spinal  Cord  is  the  centre,  in  being  only 
excitable  through  Sensation.  Reasons  have  been  given  for  the  belief,  that 
these  ganglia  are  the  centres  of  those  actions,  which  are  commonly  termed 
instinctive  in  the  lower  animals,  and  consensual  and  emotional  in  ourselves ; 
these  all  correspond,  in  being  performed  without  any  idea  of  a  purpose,  and 
without  any  direction  of  the  Will, — being  frequently  in  opposition  to  it  (§§ 
422—460). 

iv.  The  Cerebral  Hemispheres  or  Ganglia,  which  are  evidently  the  instru- 
ments or  organs  of  the  intellectual  faculties.  It  is  probably  by  them  alone, 
that  Ideas  or  notions  of  surrounding  objects  are  acquired,  and  that  these  ideas 
are  made  the  groundwork  of  mental  operations.  They  would  seem,  also,  to 
be  the  exclusive  seat  of  Memory.  The  results  of  these  operations  are  mani- 
fested on  the  bodily  frame,  through  the  Will ;  which  is  capable  of  acting,  in 
greater  or  less  degree,  on  all  the  muscles  forming  part  of  the  system  of  Ani- 
mal life  (§§  471—495). 

v.  The  Cerebellum,  which  appears  to  be  concerned  in  the  regulation  and 
harmonization  of  Muscular  movements,  especially  those  of.  a  voluntary  cha- 
racter (§§  457—470). 

497.  The  arrangement  and  connections  of  these  parts  may  be  thus  con- 
cisely expressed : — 

Tabular  view  of  the  Nervous  Centres. 

Cerebral  Ganglia, 
,   the  centres  of  the  operations 
of  Intelligence  and  Will. 

Nerves  of  Special  senO  c  r>       r  f  Nerves  of  Special  sen- 

sation  _  Motor    fibres  I  ^  ^^Co^Asual,  ~  *»  «« 

r      I      ^-ive.andE^ona!  actions. 

Cerebellic  Ganglia, 

for  harmonization  of  general 

muscular  actions. 

32* 


378 


FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 


Afferent  and  Motor  Nerves 
of.  Respiration,  Deglutition, 
&c. 


Respiratory  and 
Stomato-gastric  Ganglia, 
in  Medulla  Oblongata. 


I 
-t 


Afferent  and  Motor  Nerves 
of  Respiration,  Deglutition, 


Trunks  of  Spinal  nerves,  composed  of 
afferent  and  motor  fibres  from  true 
Spinal  Cord  and  Medulla  Oblongata ; 
and  probably  also  of  sensory  and 
motor  fibres,  connected  by  the  longi- 
tudinal strands  of  the  Cord.,  with  'the 
Sensory  Ganglia. 


VM    c    H 

'.sf.2  I 


~   5  *  o 


i 


Trunks  of  Spinal  Nerves,  composed  of 
afferent  and  motor  fibres  from  true 
Spinal  Cord  and  Medulla  Oblongata ; 
and  probably  also  of  sensory  and 
motor  fibres,  connected  by  the  longi- 
tudinal strands  of  the  Cord,  with  the 
^Sensory  Ganglia. 


The  Spinal  Cord,  the  Medulla  Oblongata,  and  Sensory  Ganglia,  seem  to 
constitute  one  continuous  group  of  ganglionic  centres ;  which  must  be  regarded 
as  the  fundamental  portion  of  the  Nervous  System.  In  descending  the  Verte- 
brated  series,  we  find  the  Cerebrum  and  Cerebellum  gradually  diminishing  in 
size  and  importance,  and  at  last,  in  the  Jlmphioxus,  disappearing  altogether ; 
and  the  Cranio- Spinal  axis,  which  then  remains,  differs  in  nothing  but  the 
continuity  of  its  vesicular  structure,  from  the  nervous  system  characteristic  of 
the  Articulata,  in  which  the  vesicular  matter  is  broken  up  (so  to  speak)  into 
distinct  centres.  In  this  Cranio-Spinal  Axis,  all  the  nerves  have  their  termi- 
nation ;  and,  from  what  has  been  ascertained  of  the  anatomy  of  the  gangliated 
cord  in  the  Articulata,  there  seems  much  reason  to  believe,  that  their  fibres 
may  pass,  in  the  longitudinal  strands  of  the  Cord,  to  great  distances  from  their 
points  of  entrance  or  emersion ;  so  that  we  may  have,  in  the  nerves  connected 
with  every  part  of  the  Cord,  sensory  fibres,  whose  real  termination  is  in  the 
Sensory  ganglia  at  its  summit,  and  motor  fibres,  which  originate  from  these 
centres,  and  are  the  instruments  of  all  the  actions  to  which  they  minister. 
The  great  difficulty  of  tracing  the  individual  fibres  of  the  Spinal  Cord,  for  any 
considerable  part  of  its  length,  renders  it  impossible,  however,  to  say  with 
certainty  that  this  is  their  real  disposition ;  but  it  is  known  that  one  at  least 
of  the  nerves,  the  Third  pair,  has  this  double  connection  with  the  Sensory 
Ganglia  and  the  Spinal  Cord  (or  rather  the  Medulla  Oblongata),  and  it  is 
likely  that  the  same  is  true  of  the  other  motor  nerves  of  the  Orbit.  Hence 
there  is  no  improbability  in  the  idea,  that  of  the  afferent  fibres  of  the  Spinal 
nerves,  some  are  connected  with  the  vesicular  matter  of  the  part  of  the  Spinal 
Cord  through  which  they  pass,  and  others  with  the  Sensory  Ganglia  in  the 
Encephalon ;  the  relative  numbers  entering  these  centres  being  accordant  with 
the  chief  purposes  of  the  trunk,  whether  as  an  excitor  of  reflex  actions,  or  as 
destined  to  arouse  sensations : — and  that  the  like  is  true  of  the  motor  fibres, 
the  relative  proportions  of  those  derived  from  the  two  sources  having  reference 
to  the  character  of  the  motions,  whether  simply-reflex  or  consensual, — to 
which  the  trunk  is  destined  to  minister.  But  there  is  by  no  means  the  same 
evidence,  that  any  fibres  contained  in  the  nerves  actually  go  on  to  the  Cere- 
brum and  the  Cerebellum;  and  the  probability  seems  rather,  that  the  fibres 
which  connect  these  masses  with  the  Cranio-spinal  Axis  are  of  a  commissural 


GENERAL  SUMMARY.  379 

nature,  and  are  destined  to  enable  them  to  receive  communications,  and  to  act 
on  the  muscular  system,  through  the  mediation  of  the  latter, — than  that  they 
are  actually  continuous  with  any  of  the  fibres  in  the  nerve-trunks  connected 
with  it  (see  §  473). 

498.  According  to  these  views,  the  following  will  be  the  mechanism  of  the 
different  classes  of  actions,  in  which  the  Cerebro-Spinal  apparatus  is  directly 
concerned. 

i.  In  Reflex  movements,  a  stimulus  acting  through  the  excitor  fibres  upon 
the  vesicular  matter  of  certain  parts  of  the  Spinal  Cord,  causes  the  transmis- 
sion of  a  reflex  impulse  through  the  motor  fibres  that  proceed  from  it ;  and 
this  gives  occasion  to  muscular  contraction. — With  this  operation,  sensation 
will  be  coincident,  if  the  stimulus  act  upon  any  of  the  fibres  that  pass  on  to 
the  Sensory  ganglia;  but  this  is  not  essential  to  it;  and  will  not  be  aroused 
if  the  connection  does  not  exist,  or  the  Sensory  ganglia  be  in  a  state  of  torpor. 

ii.  In  Sensation,  the  stimulus  acts  upon  fibres  which  have  their  termina- 
tion in  the  chain  of  ganglia  that  lies  at  the  base  of  the  cranial  cavity  in  Man, 
and  is  closely  connected  with  the  Medulla  Oblongata.  The  series  is  collect- 
ively termed  the  Sensorium ;  but  it  is  probable  that  each  is  the  instrument, 
by  which  the  animal  becomes  cognizant  of  Sensations  of  a  particular  class, — 
the  Olfactive,  Optic,  and  Auditory  ganglia,  for  those  of  Smell,  Light,  and 
Hearing  respectively,  the  Thalami  Optici  for  those  of  Touch,  and  certain  parts 
of  the  Medulla  Oblongata  for  those  of  Taste. 

in.  In  Consensual  movements,  the  stimulus  conveyed  by  the  Sensory  fibres 
becomes  the  direct  source  of  motor  impulses  ;  which  are  conveyed  through  the 
agency  of  fibres  that  issue  from  the  Sensory  ganglia  and  Corpora  Striata. 
All  the  movements  which  are  neither  reflex  nor  voluntary,  seem  to  belong  to 
this  class;  which  will  include,  therefore,  the  instinctive  actions  of  .the  lower 
animals,  with  the  automatic  and  purely  emotional  movements  in  Man. 

iv.  In  the  act  of  Perception,  or  the  formation  of  ideas  from  Sensations,  in 
Memory,  and  in  all  the  higher  acts  of  Mind,  the  Cerebrum  seems  to  be  con- 
cerned ;  the  vesicular  matter  which  constitutes  its  active  portion,  receiving  the 
stimulus  to  its  operations,  through  the  ascending  and  commissural  fibres  that 
connect  its  different  parts  with  the  Sensory  Ganglia  at  its  base.  As  the  con- 
ducting power  of  these  fibres  acts  from,  not  towards,  the  Sensory  ganglia,  we 
should  not  expect  that  irritation  of  them  should  produce  Sensation ;  and  this 
is  precisely  what  experiment  shows  to  be  the  case. 

v.  In  the  act  of  Voluntary  movement,  which  results  from  mental  operations, 
the  vesicular  matter  of  the  Cerebrum  operates,  through  the  descending  and 
commissural  fibres,  upon  the  motor  portion  of  the  Sensory  ganglia ;  the 
stimulus  transmitted  downwards  by  Volition  producing  the  same  kind  of  state 
in  its  vesicular  matter,  as  that  which  is  transmitted  upwards  by  Sensation. 
In  the  same  manner,  the  recal  of  past  Sensations  and  Ideas  may  reproduce,  in 
the  Sensory  ganglia,  the  condition  which  gives  occasion  to  the  purely  Emo- 
tional movements. 

vi.  The  combination  and  harmonization  of  the  separate  acts  of  Voluntary 
Muscular  movement,  which  is  the  function  here  attributed  to  the  Cerebellum, 
appears  to  be  prompted  by  the  guiding  sensations,  of  which  the  Sensory 
ganglia  are  the  seat;  the  influence  of  these  will  be  propagated  along  the  com- 
missural fibres  known  as  the  processus  a  cerebello  ad  testes;  and  the  motor 
influence,  resulting  from  the  action  thus  excited  in  the  vesicular  matter  of  the 
Cerebellum,  will  be  propagated  downwards  by  its  connections  with  the  various 
columns  of  the  Spinal  Cord. 

499.  The  distinctness  of  the  operations  of  these  several  centres  is  shown 
in  various  ways :  but  especially  by  conditions  of  the  bodily  system,  in  which 
one  or  more  of  them  is  in  a  state  of  inaction,  whether  temporary  or  permanent; 


380 


FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 


or  is  prevented,  by  the  interruption  of  the  usual  channel  of  communication, 
from  operating  on  particular  parts.  Thus,  in  ordinary  profound  Sleep,  which 
is  a  state  of  complete  unconsciousness,  it  is  evident  that  the  Cerebral  Hemi- 
spheres, and  the  Sensory  Ganglia,  are  at  rest;  as  the  Cerebellum,  also,  may  be 
considered  to  be:  but  the  Medulla  Oblongata  and  Spinal  Cord  must  be  in  com- 
plete functional  activity.  The  same  is  the  case  in  profound  Coma,  resulting 
from  effusion  of  blood,  or  from  narcotic  poisons,  but  not  affecting  the  power 
of  breathing  or  swallowing.  It  may  be  frequently  observed,  that  the  sleep  is 
not  so  profound  as  entirely  to  suspend  the  consciousness  of  the  individual ; 
and  that  various  movements  of  an  adaptive  character  are  performed,  tending 
to  relieve  uneasiness  resulting  from  various  causes.  In  this  condition  it  seems 
not  improbable,  that  the  Sensory  ganglia  are  in  some  degree  awake,  and  that 
the  movements  are  of  an  instinctive  nature ; — the  mind  of  the  individual  not 
being  sufficiently  active  to  discern  the  cause  of  the  uneasiness,  or  to  employ 
his  intelligence  in  the  removal  of  it.  Whenever  Dreaming  takes  place,  it  is 
evident  that  the  Cerebrum  is  in  a  state  of  partial  activity.  The  states  of 
Dreaming  and  Delirium,  and  many  forms  of  Insanity,  have  considerable 
analogy  with  each  other;  especially  in  the  absence  of  the  power  which  is  so 
characteristic  of  the  well-regulated  mind  of  Man,  of  controlling  and  regulating 
the  current  of  thought.  One  idea  calls  up  another,  according  to  their  previous 
associations;  and  the  most  incongruous  combinations  are  frequently  the  result; 
but  it  will  generally,  if  not  always,  be  found,  that  the  ideas  themselves  have 
been  previously  in  the  mind,  and  that  no  entirely  new  train  of  thought  is 
started.  Of  the  degree  in  which,  when  the  mind  is  thus  closed  to  the  external 
world,  the  hidden  stores  of  Memory  are  opened  to  its  search,  many  very 
curious  instances  are  recorded. 

500.  The  state  of  Somnambulism  appears  to  be  nearer  to  that  of  wakeful 
activity  of  the  whole  mind,  than  is  that  of  Dreaming.  In  the  latter  condition, 
the  individual  is  unconscious  of  external  objects ;  for,  if  thfey  produce  an  effect 
upon  him,  it  is  in  modifying  the  current  of  ideas,  frequently  in  some  very 
extraordinary  manner :  and  he  does  not  form  any  true  perception  or  idea  of 
their  nature.  But  in  Somnambulism,  his  senses  are  partly  awake,  so  that  im- 
pressions made  upon  them  may  be  properly  represented  to  the  mind,  and 
excite  there  the  ideas  with  which  they  are  connected ;  moreover  the  Cere- 
bellum is  also  awake,  so  that  the  movements  which  the  individual  performs, 
are  perfectly  adapted  to  their  object;  indeed,  it  has  frequently  occurred,  that 
the  power  of  balancing  the  body  has  been  so  remarkably  exercised  in  this 
condition,  that  sleep-walkers  have  traversed  narrow  and  difficult  paths,  over 
which  they  could  not  have  passed  in  open  day,  when  conscious  of  their  danger. 
In  Somnambulism,  as  in  Dreaming,  there  is  an  evident  want  of  voluntary 
control  over  the  thoughts;  their  succession  is  more  influenced,  however,  by 
impressions  received  from  without,  than  it  is  in  dreaming ;  and  hence  the  mind 
may  sometimes  be  easily  guided  into  a  particular  train,  by  properly  directing 
the  impressions  made  upon  the  sensory  organs.  It  may  often  be  remarked, 
however,  that  impressions  which  do  not  in  some  degree  harmonize  with  the 
train  of  ideas,  are  not  received  by  the  mind;  or,  at  any  rate,  they  are  not 
applied  to  the  correction  of  the  erroneous  notions  which  possess  it.  But  there 
are  many  different  shades  in  the  condition  of  the  mind,  between  Dreaming 
and  Somnambulism;  the  individual  being,  in  some  cases,  much  less  conscious 
of  external  objects,  than  he  is  in  others.  In  some  instances  it  appears  as  if 
the  mind  was  so  wholly  engrossed  in  a  particular  train  of  thought,  that  it  could 
not  be  affected  by  any  new  sensations,  so  that  there  is  even  an  unconsciousness 
of  those  which  produce  pain;  this  has  its  parallel  in  the  waking  state.  A 
very  remarkable  characteristic  of  the  state  of  Somnambulism,  is  the  complete 
isolation  which  commonly  exists,  between  the  trains  of  thought  which  then 


GENERAL  SUMMARY. PATHOLOGICAL  APPLICATIONS.  381 

occupy  the  mind,  and  its  operations  during  the  waking  hours ;  so  that  in  neither 
state  is  there  a  remembrance  of  what  passes  in  the  other.  There  is  usually 
this  difference,  however; — that  the  mental  operations  which  take  place  in 
Somnambulism  are,  like  those  of  dreaming,  frequently  suggested  by  what  has 
previously  been  occupying  the  mind ;  whilst  these  seem  to  leave  no  impression 
to  be  retraced  in  the  waking  state,  though  all  that  passes  in  one  fit  of  Som- 
nambulism may  be  recollected  in  the  next.  This  has  been  most  remarkably 
observed  in  the  phenomena  of  that  curious  state,  which  is  known  under  the 
name  of  Double  Consciousness  ;*  in  this,  the  form  of  Somnambulism  in  which 
there  is  a  consciousness  of  external,  impressions,  seems  to  alternate  with  the 
condition  of  ordinary  mental  activity,  and  the  individual  leads  (as  it  were)  two 
distinct  lives,  recollecting  in  each  condition  what  happened  in  previous  states 
of  the  same  character,  but  knowing  nothing  of  the  occurrences  of  the  other. 
— In  regard  to  the  curious  forms  of  these  affections,  which  are  produced  by 
the  so-called  Mesmeric  influence,  the  present  views  of  the  Author  will  be 
stated  in  the  Appendix. 

501.  We  have  thus  witnessed  several  varieties  in  the  condition  of  the  bo- 
dily system,  depending  upon  partial  or  complete  suspension  of  the  functional 
activity  of  the  Cerebrum,  Cerebellum,  and  Sensory  ganglia.     There  is  no 
normal  condition  of  the  Spinal  system,  which  at  all  corresponds  with  these ; 
since  its  operations  are  so  closely  connected  with  the  maintenance  of  the  Or- 
ganic functions,  that  the  suspension  of  them  necessarily  induces  the  cessation 
of  the  latter.     This  is  especially  the  case,  however,  in  regard  to  the  Respira- 
tory ganglion ;  for  the  whole  remainder  of  the  Spinal  Cord  may  be  removed, 
without  the  interruption  of  the  movements  which  are  dependent  on  that  seg- 
ment of  it.     Cases  have  occurred,  however,  in  which  the  natural  performance 
even  of  these  has  been  partially  or  entirely  suspended ;   and  in  which  the 
maintenance  of  life  has  for  a  time  been  effected,  by  a  voluntary  exertion  of 
the  muscles  of  Respiration.     The  influence  of  the  Will  upon  the  general  mo- 
tor apparatus  of  Man,  seems  to  predominate  so  greatly  over  the  Reflex  action 
of  the  Spinal  Cord,  that  few  phenomena  which  are  attributable  to  the  latter 
ordinarily  present  themselves ;  these  are  manifested,  however,  when  the  in- 
fluence of  the  Brain  over  any  part  is  cut  off,  as  is  seen  in  certain  cases  of  pa- 
ralysis.    These  morbid  conditions  present  us,  also,  with  illustrations  of  other 
effects  of  the  interruption  of  the  communication  between  the  nervous  centres 
and  particular  sets  of  muscles.     Thus,  the  influence  of  the  Will  may  be  cut 
off,  although  that  of  the  Instincts,  Emotions,  and  Reflex  Function  may  remain ; 
or  the  respondence  of  the  muscles  to  Emotion  may  be  prevented,  whilst  they 
are  still  capable  of  Voluntary  control,  or  of  Reflex  action.     Such  cases  seem 
to  point  very  clearly  to  three  distinct  primary  centres  of  nervous  agency ; — 
and  to  these,  the  Cerebrum  Sensory  Ganglia,  and  Spinal  Cord  (including  the 
Medulla  Oblongata)  have  been  here  assigned  as  the  instruments.     We  shall 
next  inquire  into  some  other  morbid  conditions  of  the  system,  which  seem 
due  to  the  irregular  action  of  these;  and  in  this  we  shall  be  chiefly  guided  by 
the  researches  of  Dr.  M.  Hall,  which  have  been  already  slightly  glanced  at 
(§§  400,  401). 

502.  Of  the  Convulsive  diseases,  it  appears  that  the  greater  part,  if  not  the 
whole,  may  be  attributed  to  a  morbid  state  of  the  Spinal  System  of  nerves. 
So  completely  does  the  power  of  producing  convulsive  movements  appear 
limited  to  that  and  to  the  Sensori-motor  system,  (no  mechanical  irritation  of 
the  Cerebral  substance  being  effectual  in  exciting  such  movements,  §  473,) 
that,  where  convulsions  present  themselves  during  diseases  which  appear 

*  Much  interesting  information  on  this  and  other  subjects,  alluded  to  in  this  Section,  may 
be  found  in  Dr.  Abercrombie's  Treatise  on  the  Intellectual  Functions. 


382 


FUNCTIONS^)F  THE  NERVOUS  SYSTEM. 


limited  to  the  Brain,  we  may  infer  that  one  of  these  systems  is  involved.  Dr. 
M.  Hall  has  recently  pointed  out,  that  this  complication  is  due  to  the  impres- 
sions made  upon  the  fibres  of  the  Spinal  nerves  distributed  upon  the  Dura 
Mater,  and  other  serous  and  fibrous  membranes  ;  for  convulsive  actions  may 
be  induced  by  pinching  these  membranes,  or  otherwise  irritating  them. — Of 
the  distinct  forms  or  combinations,  of  which  the  class  of  convulsive  disorders 
is  composed,  Tetanus  is  one  of  the  most  interesting  and  instructive.  This 
disease  is  evidently  dependent  upon  a  state  of  undue  excitability  of  the  whole 
Spinal  System ;  and  this  may  be  produced  by  different  causes.  That  which 
is  termed  the  idiopathic  form  of  the  disease  has  its  origin  in  the  centres ;  it 
may  result  in  Man  from  the  operation  of  various  predisposing  and  exciting 
causes:  and  may  be  artificially  induced  in  Animals  by  the  administration  of 
Strychnia.  In  the  traumatic  form  of  the  disease,  the  morbid  state  has  its 
origin  in  a  local  injury;  and  the  irritation  propagated  from  this,  and  operating 
through  the  Spinal  Cord,  may  be  itself  a  cause  of  many  of  the  convulsive 
movements.  But,  when  the  irritable  state  is  once  established  in  the  nervous 
centres,  convulsive  action  of  the  muscles  may  be  excited  by  any  stimuli,  and 
even  almost  entirely  without  external  causes.  Hence  it  is  that,  whilst  the 
amputation  of  the  injured  part  is  not  unfrequently  the  means  of  saving  the 
patient,  if  performed  sufficiently  early,  it  is  attended  with  no  benefit  if  delayed. 
The  Cerebral  apparatus  is  entirely  unaffected  in  this  disorder ;  but  the  nerves 
of  deglutition  are  usually  those  first  influenced  by  it;  those  of  respiration, 
hbwever,  being  soon  affected,  as  also  those  of  the  trunk  in  general. — The 
condition  termed  Hydrophobia  is  nearly  allied  to  that  of  traumatic  Tetanus, 
differing  chiefly  in  the  mode  in  which  the  cranio-spinal  axis  is  affected.  The 
irritable  state  of  the  nervous  centres  results  from  a  local  injury  of  a  peculiar 
kind;  and  here,  too,  the  early  removal  of  the  part  is  very  desirable  as  a  means 
of  prevention ;  although,  when  the  malady  has  once  reached  the  centres,  it  is 
of  no  use.  The  muscles  of  respiration  and  deglutition  are,  as  in  Tetanus, 
those  spasmodically  affected  in  the  first  instance ;  but  there  is  this  curious 
difference  in  the  mode  in  which  they  are  excited  to  action, — that,  whilst  in 
Tetanus  the  stimulus  operates  through  the  true  Spinal  Cord  (either  centrally,  or 
by  being  conveyed  from  the  periphery),  in  Hydrophobia  it  is  often  conducted 
from  the  ganglia  of  Special  Sense,  or  even  from  the  Cerebrum  ;  so  that  the 
sight  or  sound  of  fluids,  or  even  the  idea  of  them,  occasions — equally  with  their 
contact,  or  with  that  of  a  current  of  air — the  most  distressing  convulsions.  It 
would  seem,  therefore,  as  if  the  Serisori-motor  system  of  nerves  was  involved 
in  it.* — In  these  and  other  general  convulsive  diseases,  it  is  probable  that  the 
whole  vesicular  matter  of  the  centres  involved  is  in  so  excitable  a  state,  that 
a  stimulus  applied  to  any  part  of  it  may  produce  a  reaction  through  the  whole. 
In  no  other  way  would  it  be  easy  to  explain  the  great  number  and  variety  of 
movements,  which  a  small  degree  of  local  irritation  may  excite. 

503.  Epilepsy  is  another  convulsive  disease,  principally  involving  the  Spinal 
Cord,  but  partly  affecting  the  Brain.  The  predisposition  to  convulsive  move- 
ments may  depend  upon  many  causes ;  but  the  movements  themselves  are  in 
general  immediately  excited  by  some  local  irritation,  as  by  the  presence  of 
undigested  matter  in  the  stomach,  of  worms  in  the  intestines,  &c.,  although 
frequently  also  from  causes  purely  mental.  The  convulsive  movements  usually 
affect  the  muscular  system  very  extensively ;  acting  especially  upon  the  mus- 
cles of  ingestion  and  egestion.  The  Brain  is  evidently  much  concerned  in 
the  disease,  however;  as  is  evident  from  the  numerous  instances  in  which  it 
has  been  clearly  traced  to  some  local  affection  of  that  organ,  as  well  as  from 

*  For  an  interesting  case  of  the  excitement  of  involuntary  muscular  movements,  by  sen- 
sations received  through  the  eye  and  ear,  see  Dr.  Cowan,  in  Lancet  for  1845,  Vol.  II.,  p.  364. 


GENERAL  SUMMARY. PATHOLOGICAL  APPLICATIONS.  383 

the  loss  of  consciousness  which  accompanies  the  convulsion.— Many  forms 
of  that  protean  malady,  Hysteria,  are  attended  with  a  similar  irritability  of 
the  Nervous  Centres ;  but  there  is  this  remarkable  difference  in  the  two  cases, 
— that  the  morbid  phenomena  of  Hysteria,  whilst  they  often  simulate  those 
of  Tetanus,  Hydrophobia,  Epilepsy,  &c.,  are  evidently  dependent  upon  a  state 
of  the  system  of  a  much  less  abnormal  character,  being  frequently  relieved 
by  very  mild  remedies,  and  -being  often  capable  of  prevention  by  a  strong 
effort  of  the  will.  Dr.  Hall  has  pointed  out  an  important  distinction  between 
Epilepsy  and  Hysteria,  which  materially  influences  the  proximate  danger  of 
the  paroxysm  of  each  respectively ;  in  the  former,  the  larynx  is  convulsively 
closed,  and  partial  asphyxia  is  the  necessary  result,  if  the  access  of  air  be  too 
long  prevented,  so  that  venous  congestion  ensues,  increasing  the  disorder  of 
the  nervous  centres  even  to  a  fatal  degree ;  in  Hysteria,  on  the  contrary,  much 
as  the  larynx  is  affected,  it  is  not  usually  closed.  Cases  sometimes  present 
themselves,  however,  in  which  the  Hysteric  paroxysm  assumes  the  Epileptic 
character,  the  larynx  being  closed  during  expiration,  so  as  to  produce  alarming 
results.  The  disordered  state  of  the  Nervous  Centres,  to  which  these  con- 
vulsive actions  are  due,  seems  to  be  peculiarly  connected  with  Emotional  con- 
ditions of  the  mind,  and  with  functional  derangements  of  the  sexual  organs. 

504.  The  foregoing  are  the  chief  general  spasmodic  diseases  in  which  the 
Spinal  system  of  nerves  is  evidently  involved  ;*  but  there  are  many  others  of 
a  more  local  character.  Such  are  the  various  forms  of  Spasmodic  Asthma, 
the  attacks  of  which  generally  result  from  some  internal  irritation,  either  in 
the  lungs  themselves  or  in  the  digestive  system,  producing  a  reflex  action  upon 
the  muscular  fibres  of  the  bronchial  tubes.  The  Croup-like  Convulsion,  or 
Crowing  Inspiration  of  Infants,  again,  is  an  obstruction  to  the  passage  of  the 
air  through  the  glottis,  by  a  spasmodic  contraction  of  the  constrictors  of  the 
larynx.  This  spasmodic  action  may  be  induced  by  various  kinds  of  irritation  ; 
such  as  that  occasioned  by  teething,  by  the  presence  of  undigested  food,  or  by 
intestinal  disorder.  In  the  crowing  inspiration,  the  larynx  is  partially  closed  ; 
when  the  spasm  is  severe,  however,  there  is  complete  occlusion  of  the  pas- 
sage ;  and  forcible  efforts  at  expiration  are  made,  which  induce,  as  in  epilepsy, 
a  severe  degree  of  venous  congestion,  and  this  reacts  upon  the  nervous  cen- 
tres, aggravating  the  previous  disorder  of  their  condition.  The  present  in- 
creased knowledge  of  the  functions  of  the  laryngeal  nerves,  and  of  the  symp- 
toms of  this  disease,  appears  to  render  inadmissible  the  explanation  of  it  given 
not  long  since  by  Dr.  H.  Ley,  who  attributed  it  to  paralysis  of  the  pneumo- 
gastric  nerves  occasioned  by  pressure. — Spasmodic  closure  of  the  larynx  may 
occur  from  other  causes.  When  the  rima-glottidis  is  narrowed,  by  effusion 
of  fluid  into  the  substance  of  its  walls,  it  is  very  liable  to  be  completely  closed, 
by  spasmodic  action,  to  which  the  unduly  irritable  condition  of  the  mucous 
membrane  will  furnish  many  sources  of  excitement.  Choking,  again,  does 
not  result  so  much  from  the  pressure  of  the  food  on  the  air-passages  them- 

*  Chorea  is  ranked  by  Dr.  M.  Hall  as  a  disease  of  the  Spinal  System  of  nerves ;  but  this 
can  scarcely  be  regarded  as  a  correct  determination.  It  is  true  that  there  is  considerable 
irregularity  in  the  ordinary  Reflex  actions ;  but  the  irregularity  is  still  greater  in  those,  to 
which  Volition  or  Emotion  are  the  stimuli.  Moreover,  the  body  is  at  rest  during  sleep ;  and 
"the  Spinal  system  never  sleeps."  The  frequent  origin  of  the  disease  in  causes  which  have 
excited  strong  mental  emotions,  and  the  effect  of  even  moderate  excitement  of  the  feelings 
in  greatly  aggravating  the  movements  of  the  body,  seem  to  indicate  the  connection  of  this 
disease  with  the  Sensori-motor  system  of  nerves.  Stammering  maybe  regarded  as  a  sort  of 
Chorea  affecting  the  muscles  of  voice ;  of  this  more  hereafter  (CHAP.  vi).  In  Paralysis  Agitans, 
it  may  be  usually  observed,  that  the  voluntary  actions  are  much  more  affected  than  the  reflex ; 
the  latter,  indeed,  not  in  general  manifesting  any  disturbance.  An  interesting  and  well  marked 
case  of  this  disease  has  been  mentioned  to  the  author  by  Dr.  W.  Budd,  in  which  softening 
was  found  in  the  Crura  Cerebri. 


384  FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 

selves,  as  from  the  spasmodic  action  of  the  larynx,  excited  by  this ;  and  the 
dislodgement  of  the  morsel  by  an  act  of  vomiting,  is  the  most  effectual  means 
of  obtaining  relief. — Tenesmus  and  Strangury  are  well-known  forms  of  spas- 
modic muscular  contraction,  excited  by  local  irritation  acting  through  the 
Spinal  system.  The  abnormal  action  which  leads  to  Abortion  is  frequently 
excited  in  the  same  manner  ;  how  far  the  uterus  itself  is  called  into  contrac- 
tion by  the  ordinary  spinal  nerves,  is  a  question  as  yet  undecided ;  but  the 
facts  already  stated  leave  no  doubt,  that  stimuli  operating  on  these  may  act 
upon  it  through  the  Sympathetic,  into  which  their  fibres  pass  (§  393).  It  will 
be  borne  in  mind,  however,  that,  in  abortion,  as  in  ordinary  parturition,  many 
muscles  are  called  in,  to  aid  the  contractions  of  the  uterus,  which  are  strictly 
under  the  dominion  of  the  Spinal  system. — There  is  a  form  of  Incontinence 
of  urine,  which  is  very  analogous  to  the  morbid  action  just  described ;  the 
sphincter  has  its  due  power  ;  but  the  stimulus  to  the  evacuation  of  the  bladder 
is  excessive  in  strength  and  degree,  owing  to  the  acridity  of  the  urine  or  other 
causes.  The  part  of  the  bladder  upon  which  this  appears  chiefly  to  act,  is 
the  trigonum  (which  is  well  known  to  be  more  sensitive  to  the  irritation  of 
calculi,  than  the  rest  of  the  internal  surface)  ;  and  Sir  C.  Bell  advises  young 
persons  who  suffer  during  the  night  from  this  very  disagreeable  complaint,  to 
lie  upon  the  belly  instead  of  the  back,  so  that  the  contact  of  the  urine  with 
the  trigonum  may  be  delayed  as  long  as  possible. 

505.  One  of  the  most  familiar  examples  of  the  pathological  excitement  of 
the  true  Spinal  system  is  the  act  of  Vomiting;  and,  as  Dr.  M.  Hall  justly 
remarks,  the  special  function  of  this  system  nowhere  receives  better  illustra- 
tion. The  act  may  be  excited  in  various  ways.  Thus,  it  results  from  the 
tickling  of  the  fauces  with  a  feather  or  with  the  finger  ;  but  if  the  feather  be 
carried  too  far  down,  an  act  of  deglutition  is  induced  instead  of  vomiting.* 
In  this  instance  the  glosso-pharyngeal,  and  perhaps  also  the  fifth  pair,  are  the 
nerves  by  which  the  stimulus  is  conveyed  to  the  Medulla  Oblongata.  Vomit- 
ing, again,  may  be  induced  by  substances  introduced  into  the  stomach ;  and 
here  the  pneumogastric  is  evidently  the  excitor.  When  it  takes  place  as  a 
result  of  pregnancy,  or  of  some  intestinal  irritation,  the  stimulus  must  be  con- 
veyed, either  through  one  of  the  ordinary  Spinal  nerves,  or  through  the  Sym- 
pathetic. But  it  may  also  be  occasioned  by  the  sight,  smell,  or  taste  of  any 
disagreeable  object,  or  by  the  mere  conception  of  it,  or  by  mental  emotion 
simply.  In  this  case,  the  stimulus  appears  to  be  received  by  the  ganglia  of 
special  sense,  and  to  be  transmitted  by  them  to  the  muscles  concerned,  as  by 
the  Spinal  Cord  or  Medulla  Oblongata  in  the  former  case.  When  Vomiting 
is  excited  by  the  introduction  of  emetic  substances  into  the  blood,  it  is  proba- 
ble that  their  stimulation  chiefly  operates  through  the  extended  plexus  of 
nerves,  spread  out  by  the  Sympathetic  upon  the  walls  of  the  blood-vessels  ; 
but  the  irritant  action  of  the  substance  upon  the  nervous  centres  may  be  also 
concerned. — In  regard  to  the  mechanism  by  which  the  act  of  Vomiting  is 
produced,  considerable  difference  of  opinion  has  existed.  The  old  doctrine 
was,  that  it  was  solely  occasioned  by  the  contraction  of  the  stomach  itself; 
but  Magendie  proved  that  this  could  not  be  the  case,  by  substituting  a  bladder 
for  the  stomach  of  an  animal,  and  then  injecting  a  solution  of  tartarized  anti- 
mony into  its  blood,  which  immediately  caused  the  emptying  of  the  bladder, 
by  the  pressure  of  the  surrounding  muscles  ;  these  muscles  he  considered  to 

*  This  has  been  the  cause  of  many  accidents.  Patients  have  tickled  the  fauces  with  a 
feather  in  order  to  excite  vomiting ;  and,  having  introduced  it  too  far  into  the  pharynx,  it  has 
been  drawn  out  of  their  fingers  by  the  muscles  of  deglutition,  and  carried  into  the  oesophagus. 
Similar  accidents  have  occurred  with  the  rectum-bougie,  and  female  catheter,  as  well  as  with 
probes,  &c.,  introduced  into  the  male  urethra  ;  all  the  orifices  being  furnished  with  a  kind  of 
ingestive  power,  which  is  clearly  the  result  of  Reflex  action. 


OF  SENSATION  IN  GENERAL.  385 

be  the  diaphragm  and  abdominal  muscles,  the  conjoint  actions  of  which  would 
be  a  peculiarity  observed  in  no  other  instance.  By  Dr.  M.  Hall,  on  the  other 
hand,  it  is  maintained  that  the  act  of  vomiting  is,  like  the  expulsion  of  the 
foetus,  urine,  faeces,  &c.,  an  expiratory  effort,  modified  in  its  effects  by  the  pe- 
culiar condition  of  the  sphincters.  It  bears,  indeed,  great  resemblance  to  the 
act  of  coughing  ;  differing  chiefly  in  this,  that  in  vomiting,  the  larynx  is  closed 
during  the  whole  operation,  whilst  it  is  only  closed  momentarily  in  coughing ; 
and  also,  that  in  coughing,  the  cardiac  orifice  of  the  stomach  is  closed,  whilst 
in  vomiting  it  is  opened.  In  this  view,  the  accuracy  of  which  has  been  proved 
by  experiment,  the  diaphragm  is  quite  inert. — A  curious  case  has  been  re- 
corded by  Drs.  Graves  and  Stokes,*  in  which  vomiting  took  place  from  the 
stomach  of  a  man,  who  was  found  after  death  to  be  the  subject  of  a  very  re- 
markable change  in  the  relative  position  of  the  viscera, — -the  stomach  lying  in 
the  thorax,  which  cavity  communicated  with  the  abdomen,  by  an  opening  in 
the  diaphragm,  giving  passage  to  the  oesophagus  and  duodenum.  This  case 
was  regarded  by  its  reporters  as  proving  that  vomiting  might  take  "place  by 
the  action  of  the  stomach  alone ;  but  it  can  scarcely  be  held  to  justify  this 
conclusion ;  since,  the  diaphragm  being  entirely  passive,  the  abdominal  mus- 
cles would  have  the  same  power  of  emptying  the  stomach,  as  they  would 
possess  over  the  lungs.  There  can  be  little  doubt,  however,  that  the  walls  of 
the  stomach  participate  in  the  action ;  for  even  the  oesophagus  is  thrown  into 
a  state  of  reversed  peristaltic  movement. 


CHAPTER    VI. 

ON    SENSATION,    AND    THE    ORGANS    OF    THE    SENSES. 

1. — Of  Sensation  in  General. 

506.  BY  the  term  Sensation  is  rightly  understood  that  change  in  the  con- 
dition of  the  mind,  by  which  we  become  aware  of  an  impression  made  upon 
some  part  of  the  body;  or,  in  a  briefer  form  of  expression,  it  may  be  denned 
to  be  the  consciousness  of  an  impression.  Some  physiologists  have,  it  is 
true,  spoken  of  a  sensation  without  consciousness ;  but  it  seems  very  de- 
sirable thus  to  limit  the  term  ;  since  the  word  impression  may  be  very  well 
applied  to  designate  the  change  produced  in  the  afferent  nerves  by  an  external 
cause,  up  to  the  point  at  which  the  mind  becomes  conscious  of  it.  We  have 
seen  reason  to  believe,  that  the  impressions  communicated  to  the  Spinal  Cord 
may  there  excite  motor  actions,  without  occasioning  true  Sensation  ;  and  it 
would  seem  to  be  with  the  Encephalon  only,  that  the  Mind  possesses  the 
relation  necessary  for  the  production  of  such  a  change  in  it.  Hence  this 
organ  is  spoken  of  as  the  Sensorium.  For  the  reasons  already  given  (§  435), 
it  seems  probable  that  the  ganglia  of  Special  Sensation  are  rather  the  essential 
instruments  of  this  function,  than  the  Cerebral  Hemispheres.  The  afferent 
nervous  fibres,  which  connect  the  various  parts  of  the  body  with  the  Senso- 
rium, are  termed  sensory.  This  term  has  also  been  applied  to  those  which 
terminate  in  the  Spinal  Cord  ;  but  as  the  impressions  which  these  convey  do 
not  produce  sensations,  it  seems  desirable  to  avoid  thus  designating  them ; 

*  Dublin  Hospital  Reports,  Vol.  v. 


386 


ON  SENSATION,  AND  THE  ORGANS  OF  THE  SENSES. 


and  the  term  excitor,  proposed  by  Dr.  M.  Hall,  is  much  preferable.  Every 
afferent  spinal  nerve,  therefore,  is  made  up  of  sensory  and  of  excitor  fibres  ; 
and  these  may  be  distributed  in  very  different  proportions  to  different  parts. 
Of  the  excitor  fibres,  enough  has  been  already  said.  Those  parts  of  the  body 
which  are  endowed  with  sensory  fibres,  and  impressions  on  which,  therefore, 
give  rise  to  sensation,  are  ordinarily  spoken  of  as  sensible,  and  different  parts 
are  spoken  of  as  sensible  in  different  degrees,  according  to  the  strength  of  the 
sensation  which  is  produced  by  a  corresponding  impression  on  each. 

507.  In  accordance  with  what  was  formerly  stated  (§  250)  of  the  depend- 
ence of  all  nervous  action  on  the  continuance  of  the  capillary  Circulation, 
especially  at  the  extremities  of  the  fibres,  it  is  found  that  the  sensory  nerves 
are  distributed  pretty  much  in  the  same  proportion  as  the  blood-vessels ;  that 
is  to  say,  in  the  non-vascular  tissues, — such  as  the  epidermis,  hair,  nails,  car- 
tilage, and  bony  substance  of  the  teeth, — no  nerves  exist,  and  there  is  an  en- 
tire absence  of  sensibility ;  and  in  those  whose  vascularity  is  trifling,  the  sen- 
sibility is  dull,  as  is  the  case  with  bones,  tendons,  ligaments,  fibrous  mem- 
branes, and  other  parts  whose  functions  are  simply  mechanical,  and  even  with 
serous  and  areolar  membranes.  Many  of  these  textures  are  acutely  sensible, 
however,  under  certain  circumstances  ;  thus,  although  tendons  and  ligaments 
may  be  wounded,  burned,  &c.,  with  little  or  no  consciousness  of  the  injury, 
they  cannot  be  stretched  without  considerable  pain  ;  and  the  fibrous,  serous 
and  areolar  tissues,  when  their  vascularity  is  increased  by  inflammation,  also 
become  extremely  susceptible  of  painful  impressions.  All  very  vascular  parts, 
however,  do  not  possess  acute  sensibility;  the  muscles,  for  instance,  are  fur- 
nished with  a  large  supply  of  blood,  to  enable  them  to  perform  their  peculiar 
function  ;  but  they  are  not  sensible  in  by  any  means  the  same  proportion. 
Even  the  substance  of  the  brain  and  of  the  nerves  of  special  sensation,  ap- 
pears to  be  destitute  of  this  property ;  and  the  same  may  be  said  of  the  mu- 
cous membranes,  lining  the  interior  of  the  several  viscera,  which,  in  the  ordi- 
nary condition,  are  much  less  sensible  than  the  membranes  which  cover  those 
viscera,  although  so  plentifully  supplied  with  blood  for  their  especial  purposes. 
The  most  sensible  of  all  parts  of  the  body,  is  the  Skin,  in  which  the  sensory 
nerves  spread  themselves  out  into  a  minute  net- work ;  and  even  of  this  tissue, 
the  sensibility  differs  greatly  in  different  parts.  The  organs  of  special  sensa- 
tion are,  by  the  peculiar  character  of  the  nerves  with  which  they  are  sup- 
plied, rendered  sensible  to  impressions  of  a  particular  kind :  thus,  the  eye  is 
sensible  to  light,  the  ear  to  sound,  &c. ;  and  whatever  amount  of  ordinary 
sensibility  they  possess,  is  dependent  upon  other  sensory  nerves.  The  eye, 
for  example,  contrary  to  the  usual  notions,  is  a  very  insensible  part  of  the 
body,  unless  affected  with  inflammation  ;  for  though  the  mucous  membrane 
which  covers  its  surface,  and  which  is  prolonged  from  the  skin,  is  acutely 
sensible  to  some  kinds  of  impressions,  the  interior  is  by  no  means  so,  as  is 
well  known  to  those  who  have  operated  much  on  the  eye.  And  there  are 
many  parts  of  the  body,  that  are  supplied  with  the  common  sensory  nerves 
which  convey  to  the  mind  impressions  of  particular  kinds,  with  much  greater 
readiness  than  they  communicate  those  of  a  different  description. 

508.  It  appears,  then,  that  the  vascularity  of  a  part  is  an  essential  condition 
of  its  sensibility;  but  it  does  not  follow  that  a  tissue  should  be  peculiarly  sen- 
sible, because  it  is  highly  vascular;  since  its  large  supply  of  blood  may  be 
required  for  other  purposes.  It  is  not  simple  vascularity,  however,  which  is 
necessary,  but  rather  an  active  capillary  circulation ;  any  cause  which  retards 
this,  deadens  the  sensibility,  as  is  well  seen  in  regard  to  cold;  and,  on  the 
other  hand,  an  increase  in  its  energy  produces  a  corresponding  increase  in  the 
sensibility,  as  is  peculiarly  evident  in  the  active  congestion  which  usually  pre- 
cedes inflammation.  Acute  sensibility  to  external  impressions  may  arise, 


OF  SENSATION  IN  GENERAL.  387 

however,  not  only  from  abnormal  activity  of  the  circulation  in  the  organ  or 
part  itself,  but  from  the  same  condition  affecting  that  part  of  the  sensorium  in 
which  the  impressions  are  received.  Thus  in  active  congestion  and  inflam- 
mation of  the  brain,  the  most  ordinary  external  impressions  produce  sensations 
of  an  unbearable  violence ;  and  there  are  some  peculiar  conditions  of  the 
nervous  system,  known  under  the  name  of  hysterical,  in  which  the  patients 
manifest  the  same  discomfort,  even  when  the  circulation  is  in  a  feeble,  rather 
than  an  excited  state.  It  is  remarkable  that  the  sensibility  of  the  mucous 
membranes  lining  the  internal  organs,  is  less  exalted  by  the  state  of  inflamma- 
tion, than  is  that  of  most  other  parts ;  and  in  this  arrangement  we  may  trace 
a  wise  and  beneficent  provision  ;  since,  were  it  otherwise,  the  functions  neces- 
sary to  life  could  not  be  performed  without  extreme  distress,  with  a  very 
moderate  amount  of  disorder  in  the  viscera.  If  a  joint  is  inflamed,  we  can 
give  it  rest ;  but  to  the  actions  of  the  alimentary  canal  we  can  give  little  volun- 
tary respite. 

509.  The  feelings  of  Pain  or  Pleasure,  which  are  connected  with  particular 
sensations,  cannot  (for  the  most  part  at  least)  be  explained  upon  any  other 
principle  than  that  of  the  necessary  association  of  these  feelings,  by  an  original 
law  of  our  nature,  with  the  sensations  in  question.  As  a  general  rule,  it  may 
be  stated,  that  the  violent  excitement  of  any  sensation  is  disagreeable,  even 
when  the  same  sensation  in  a  moderate  degree  may  be  a  source  of  extreme 
pleasure.  This  is  the  case  alike  with  those  impressions,  which  are  communi- 
cated through  the  organs  of  sight,  hearing,  smell  and  taste,  as  with  those  that 
are  received  through  the  nerves  of  common  sensation ;  and  there  can  be  no 
doubt  that  the  final  cause,  or  purpose,  of  the  association  of  painful  feelings 
with  such  violent  excitement,  is  to  stimulate  the  individual  to  remove  himself 
from  what  would  be  injurious  in  its  effects  upon  the  system.  Thus,  the  pain 
resulting  from  violent  pressure  on  the  cutaneous  surface,  or  from  the  proximity 
of  a  heated  body,  gives  warning  of  the  danger  of  injury,  and  excites  mental 
operations  destined  to  remove  the  part  from  the  influence  of  the  injurious 
cause ;  and  this  is  shown  by  the  fact,  that  loss  of  sensibility  is  frequently  the 
indirect  occasion  of  severe  lesions, — the  individual  not  receiving  the  customary 
intimation  that  an  injurious  process  is  taking  place.  Instances  have  occurred, 
in  which  severe  inflammation  of  the  membrane  lining  the  air-passages  has  re- 
sulted from  the  effects  of  ammoniacal  vapours,  introduced  into  them  during  a 
state  of  syncope, — the  patient  not  receiving  that  notice  of  the  irritation,  which 
would,  in  an  active  condition  of  his  nervous  system,  have  prevented  him  from 
inhaling  the  noxious  agent. 

a.  The  following  case,  recorded  in  the  "Journal  df  a  Naturalist,"  affords  a  remarkable 
instance  of  this  general  fact.  The  correctness  of  the  statement  having  been  called  in  question, 
it  was  fully  confirmed  by  Mr.  Richard  Smith,  the  late  senior  surgeon  of  the  Bristol  Infirmary, 
under  whose  care  the  sufferer  had  been.  "A  travelling  man,  one  winter's  evening,  laid 
himself  down  upon  the  platform  of  a  lime-kiln,  placing  his  feet,  probably  numbed  with  cold, 
upon  the  heap  of  stones,  newly  put  on  to  burn  through  the  night.  Sleep  overcame  him  in 
this  situation ;  the  fire  gradually  rising  and  increasing,  until  it  ignited  the  stones  upon  which 
his  feet  were  placed.  Lulled  by  the  warmth,  the  man  slept  on;  the  fire  increased  until  it 
burned  one  foot  (which  probably  was  extended  over  a  vent-hole)  and  part  of  the  leg  above 
the  ankle  entirely  off,  consuming  that  part  so  effectually,  that  a  cinder-like  fragment  was 
alone  remaining, — and  still  the  wretch  slept  on !  and  in  this  state  was  found  by  the  kiln-man 
in  the  morning.  Insensible  to  any  pain,  and  ignorant  of  his  misfortune,  he  attempted  to  rise 
and  pursue  his  journey,  but  missing  his  shoe,  requested  to  have  it  found ;  and  when  he  was 
raised,  putting  his  burnt  limb  to  the  ground  to  support  his  body,  the  extremity  of  his  leg-bone, 
the  tibia,  crumbled  into  fragments,  having  been  calcined  into  lime.  Still  he  expressed  no 
sense  of  pain,  and  probably  experienced  none ;  from  the  gradual  operation  of  the  fire,  and  his 
own  torpidity  during  the  hours  his  foot  was  consuming.  This  poor  drover  survived  his  mis- 
fortunes in  the  hospital  about  a  fortnight ;  but  the  fire  having  extended  to  other  parts  of  his ' 
body,  recovery  was  hopeless." 


388 


ON  SENSATION,  AND  THE  ORGANS  OF  THE  SENSES. 


510.  It  is  a  general  rule,  with  regard  to  all  sensations,  that  their  intensity 
is  much  affected  by  habit;  being  greatly  diminished  by  frequent  and  continual 
repetition.     This  is  not  the  case,  however,  with  regard  to  those  sensations  to 
which  the  attention  is  peculiarly  directed  ;  for  these  lose  none  of  their  acute- 
ness  by  frequent  repetition;  on  the  contrary,  they  become  much  more  readily 
cognizable  by  the  mind. — We  have  a  good  example  of  both  facts,  in  the  ef- 
fects of  sounds  upon  a  sleeping  person.     If  they  are  sounds  which  he  has 
been  accustomed  to  hear,  and  to  disregard,  they  may  not  awake  him,  however 
loud  they  be :  thus,  the   strokes  of  a  forge-hammer,  the  firing  of  guns,  the 
shouts  of  a  multitude,  or  the  loudest  music,  may  neither  prevent  the  acces- 
sion of  sleep,  nor  arouse  the  already  unconscious  sleeper ;  indeed,  it  oftener 
happens  that  individuals  are  prevented  from  sleeping  by  the  want  of  some 
accustomed  sound,  or  are  awoke  by  its  cessation.     On  the  other  hand,  a  very 
slight  sound,  the  nature  of  which  excites  the  attention,  is  sufficient  to  prevent 
sleep ;  thus,  the  buzz  of  a  single  musquito,  in  the  stillness  of  the  night,  is 
most  effectual  in  dispelling  repose  ; — and,  in  like  manner,  a  person  in  a  state 
of  the  profoundest  unconsciousness  may  be  aroused  by  a  whisper,  if  the  sound 
be  one  to  which  he  has  been  accustomed  to  pay  regard. 

a.  The  following  circumstance  has  been  communicated  to  the  Author  by  a  Naval  Officer 
of  high  rank : — When  a  young  man  he  was  serving  as  signal-lieutenant  under  Lord  Hood  ; 
and  being  desirous  of  obtaining  the  favourable  notice  of  his  commander,  he  devoted  him- 
self to  his  duty  with  the  greatest  energy  and  perseverance,  often  remaining  on  deck  nineteen 
hours  out  of  the  twenty-four,  with  his  attention  continually  on  the  stretch.  During  the  few 
hours  which  he  spent  in  repose,  his  sleep  was  so  profound,  that  no  noise  of  an  ordinary 
kind,  however  loud,  would  awake  him.  But  if  the  word  "  signal"  was  softly  uttered  in  his 
ear,  he  was  instantly  aroused. 

511.  The  general  law,  that  Sensations,  not  attended  to,  are  blunted  by  fre- 
(juent  repetition,  may  perhaps  be  connected  with  certain  other  general  facts, 
which  lie  under  the  observation  of  every  one.     It  is  well  known,  that  the 
vividness  of  sensations  depends  rather  on  the  degree  of  change  which  they 
produce  in  the  system,  than  on  the  absolute  amount  of  the  impressing  cause; 
and  this  is  alike  the  case  with  regard  to  the  special  and  the  ordinary  sensa- 
tions.    Thus,  our  sensations   of  heat  and  cold  are  entirely  governed  by  the 
previous  condition  of  the  parts  affected ;  as  is  shown  by  the  well-known  ex- 
periment, of  putting  one  hand  in  hot  water,  the  other  in  cold,  and  then  trans- 
ferring both  to  tepid  water,  which  will  seem  cool  to  one  hand,  and  warm  to 
the  other.    Every  one  knows,  too,  how  much  more  we  are  affected  by  a  warm 
day  at  the  commencement  of  the  summer,  than  by  an  equally  hot  day  later 
in  the  season.     The  same  is  the  case  in  regard  to  light  and  sound,  smell  and 
taste.     A  person  going  out  of  a  totally  dark  room  into  one  moderately  bright, 
is  for  the  time  painfully  impressed  by  the  light,  but  soon  becomes  habituated 
to  it ;  whilst  another,  who  enters  it  from  a  room   brilliantly  illuminated,  will 
consider  it  dark  and  gloomy.     Those  who  are  constantly  exposed  to  very  loud 
noises,  become  almost  unconscious  of  them,  and  are  even  undisturbed  by  them 
in  illness;  and  the  medical  student  well  knows,  that  even  the  effluvia  of  the 
dissecting-room  are  not  perceived,  when  the  organ  of  smell  is  habituated  to 
them,  although  an  intermission  of  sufficient  length  would,  in  either  instance, 
occasion  a  renewal  of  the  first  unpleasant  feelings,  when  the  individual  is 
again  subjected  to  the  impression. 

512.  Again,  it  is  a  well-known  fact,  that  impressions  made  upon  the  organs 
of  sense  continue  for  a  time,  after  the  cause  of  the  impression  has  ceased. 
It  is  in  this  manner  that  a  musical  tone,  which  seems  perfectly  continuous, 
results  from  a  series  of  consecutive  vibrations,  following  each  other  with  a 
certain  rapidity  ;   and  that  a  line  or  circle  of  light  is  produced  by  a  luminous 
body  moving  with  a  certain  velocity.     Now  there  is  reason  to  believe  that 


OF  SENSATION  IN  GENERAL.  389 

changes,  of  which  the  effects  thus  transiently  remain  upon  the  nerves  of  sense, 
are  more  permanently  impressed  upon  the  Sensorium;  since,  as  formerly 
shown  (§  491),  we  can  only  in  this  manner  account  for  the  phenomena  of 
Memory,  and  for  the  effects  produced  upon  this  power,  by  material  changes 
in  the  brain.  Hence,  the  diminution  in  the  force  of  sensations,  which  is  the 
consequence  of  their  habitual  recurrence,  may  be  considered  as  resulting  from 
these  two  general  facts, — the  persistence  of  the  impression  made  by  them 
upon  the  sensorium, — and  the  consequent  absence  of  a  change  in  its  state, 
when  a  sensory  impression  is  brought  to  it,  which  is  of  the  same  nature  with 
one  already  registered  there  :  the  degree  in  which  the  consciousness  is  ex- 
cited, being  dependent,  as  just  stated,  not  upon  the  absolute  degree  of  the 
impressing  cause,  but  upon  the  amount  of  change  which  it  produces  in  the 
sensorial  apparatus.  In  this  respect  there  is  a  perfect  conformity  between 
the  law  of  sensation,  and  that  of  muscular  contraction ;  for  stimuli  which  ex- 
cite the  latter,  usually  lose  their  force  in  proportion  to  the  frequency  of  their 
repetition.  Indeed,  both  may  be  considered  as  results  of  the  more  general 
laws  of  vitality ;  for  the  actions  of  other  tissues  follow  the  same  rule,  as  is 
shown  by  the  tolerance,  that  may  be  gradually  established  in  the  system,  of 
medicinal  agents,  poisons,  &c.,  which  would  have  at  first  produced  the  most 
violent  effects,  when  given  in  the  same  amount. 

513.  It  is  curious,  also,  that  the  feelings  of  Pain  or  Pleasure,  which  unac- 
customed sensations  excite,  are  often  exchanged  for  each  other,  when  the  sys- 
tem is  habituated  to  them  ;  this  is  especially  the  case,  in  regard  to  impressions 
communicated  through  the  organs  of  smell  and  taste.     There  are  many  arti- 
cles in  common  use  among  mankind, — such  as  Tobacco,  Fermented  Liquors, 
<fcc.,  the  use  of  which  cannot  be  said  to  produce  a  natural  enjoyment,  since 
it  is  at  first  unpleasant  to  most  persons  ;  and  yet  it  first  becomes  tolerable, 
then  agreeable ;  and  at  last  the  want  of  them  is  felt  as  a  painful  privation,  and 
the  stimulus  must  be  applied  in  an  increasing  degree,  in  order  to  produce 
the  usual  effect. 

514.  It  is  through  the  medium  of  Sensation,  that  we  acquire  a  knowledge 
of  the  material  world  around  us ;  and  that  its  changes  excite  mental  operations 
in  ourselves.     The  various  kinds  or  modes  of  Sensation  excite  in  us  various 
ideas  regarding  the  properties  of  matter  ;  and  these  properties  are  known  to 
us,  only  through  the  changes  which  they  produce  in  the  several  organs.     Thus 
a  man  totally  blind  from  birth  can  form  no  idea  of  the  nature  of  light  or  co- 
lours; nor  could  one  completely  deaf  have   any  just  conception  of  musical 
tones.    It  is  well  known  that  instances  exist,  in  which,  from  some  imperfection 
of  the  organization,  there  is  an  incapacity  for  distinguishing  colours  or  musi- 
cal tones,  whilst  there  is  no  want  of  sensibility  to  light  or  sound ;  and  that 
some  persons  are  naturally  endowed  with  a  much  greater  range  of  the  sen- 
sory faculties,  than  others  possess.    Hence  it  does  not  seem  at  all  improbable, 
that  there  are  properties  of  matter,  of  which  none  of  our  senses  can  take 
immediate  cognizance  ;  and  which  other  beings  might  be  formed  to  perceive, 
in  the  same  manner  as  we  are  sensible  to  light,  sound,  &c.     Thus,  it  is  well 
known,  that  many  animals  are  affected  by  atmospheric  changes,  in  such  a 
manner,  that  their  actions  are  regarded  by  Man  as  indications  of  the  probable 
state  of  the  weather ;  and  the  same  is   the  case  in  a  less  degree  with  some 
of  our  own  species ;  who  are  peculiarly  susceptible  of  the  same  influences. 
Now   the   most   universal  of  all  the    qualities  or  propensities  of  matter, — 
that,  in  fact,  on  which  our  notion  of  it  is   founded, — is  resistance ;   and 
it  is  this  quality,  of  which  the  knowledge  seems  most  universally  diffused 
throughout  the  Animal  kingdom.     In  the  lowest  tribes,  we  find  that  contact, 
between  their  surface  and  some  material  body,  is  required  to  produce  sensa- 

33* 


390  ON  SENSATION,  AND  THE  ORGANS  OF  THE  SENSES. 

tion  ;  and  beings  which  cannot  be  made  conscious,  in  this  manner,  of  the 
existence  of  something  external  to  themselves,  do  not  deserve  to  be  ranked 
in  the  Animal  kingdom.  Our  difficulty  lies  (as  heretofore  remarked,  §  1), 
in  ascertaining  what  are  to  be  regarded,  in  such  beings,  as  unequivocal  indi- 
cations of  consciousness.  Those  animals  which  are  fixed  to  one  spot,  can 
have  few  other  ideas  of  matter  than  this  most  general  one  ;  but  in  those 
which  have  the  power  of  locomotion,  the  general  sensibility  of  the  surface 
doubtless  communicates  to  them  some  notion  of  the  character  of  the  body 
over  which  they  move,  in  the  same  manner  as  we  learn  it  by  passing  the 
hand  over  its  exterior.  We  shall  presently  see,  however,  that  the  idea  of 
the  shape  of  a  body  which  we  form  from  the  touch,  results  from  a  very  com- 
plex process  ;  which  animals  of  the  lowest  grade  can  scarcely  be  supposed 
to  exercise.  There  can  be  no  doubt  that,  next  to  the  mere  sense  of  resistance, 
sensibility  to  temperature  is  the  most  universally  diffused  through  the  Ani- 
mal kingdom ;  and  probably  the  consciousness  of  luminosity  is  the  next  in 
the  extent  of  its  diffusion.  There  is  good  reason  to  believe,  from  observation 
of  their  habits,  that  many  animals  are  susceptible  of  the  influence,  and  are 
directed  by  the  guidance  of  light ;  whilst  their  organs  are  not  adapted  to  re- 
ceive true  visual  impressions,  or  to  form  optical  images  ;  and  such  would 
seem  to  be  the  function  of  the  red  spots,  frequently  seen  on  prominent  parts 
of  Animalcules,  the  lower  Articulata  and  Mollusca,  and  even  of  some  Radiata. 
Wherever  these  are  of  sufficient  size  to  allow  their  structure  to  be  examined, 
they  are  found  to  be  largely  supplied  with  nerves,  but  to  be  destitute  of  the 
peculiar  organization  which  alone  constitutes  a  true  eye.  The 'sense  of  Taste 
may  be  considered  as  a  refined  modification  of  that  of  Touch ;  and  it  is 
probable  that  this  exists  very  low  down  in  the  animal  scale,  being  obviously 
of  great  importance  in  the  selection  of  food  ;  but  the  Anatomist  has  no  means 
of  ascertaining  where  this  refinement  exists,  and  where  it  does  not ;  since  the 
organs  of  taste  and  touch  are  so  similar.  The  sense  of  Hearing  does  not 
seem  to  be  distinctly  present  among  the  Invertebrate  animals,  except  in  such 
as  approach  most  nearly  to  the  Vertebrata ;  it  is  not  improbable,  however, 
that  sonorous  vibrations  may  produce  an  effect  upon  the  system  of  those  ani- 
mals which  do  not  receive  them  as  sound;  and  this  would  appear,  from  a 
fact  subsequently  to  be  mentioned  (§  526),  to  be  not  improbably  the  case, 
with  regard  especially  to  aquatic  animals.  The  sense  of  Smell,  which  is  con- 
cerned with  one  of  the  least  general  properties  of  matter,  appears  to  be  the 
least  widely  diffused  among  the  whole ;  being  only  possessed  in  any  high 
degree  by  Vertebrated  animals,  and  being  "but  feebly  present  in  a  large  pro- 
portion of  these. 

515.  Besides  the  various  kinds  of  sensibility  which  have  been  just  enume- 
rated, there  are  others  which  are  ordinarily  associated  together,  along  with 
the  sense  of  material  resistance  (and  its  several  modifications),  and  the  sense 
of  temperature,  under  the  head  of  Common  Sensation ;  but  several  of  them, 
especially  those  which  originate  in  the  body  itself,  can  scarcely  be  regarded 
in  this  light.  Such  are  the  feelings  of  Hunger  and  Thirst;  that  of  Nausea; 
that  of  distress  resulting  from  suspended  aeration  of  the  blood  ;  that  of  "  sink- 
ing at  the  stomach,"  as  it  is  vulgarly  but  expressively  described,  which  results 
from  strong  mental  emotion  ;  that  of  the  venereal  excitement,  and  perhaps 
some  others.  Now  in  regard  to  all  these,  it  is  impossible  in  the  present  state 
of  our  knowledge  to  say,  whether  their  peculiarity  results  from  the  particular 
constitution  of  the  nerves  that  receive  and  convey  them,  or  only  from  a  modi- 
fication in  the  impressing  causes,  and  in  the  mode  in  which  they  operate. 
Thus  we  have  no  evidence  that  the  nervous  fibrils,  which  convey  from  the 
lungs  the  sense  of  distress  resulting  from  deficient  aeration,  may  not  be  of  a 
different  character  from  those  which  convey  from  the  surface  of  the  air-pas- 


OF  SENSATION  IN  GENERAL.  391 

sages  the  sense  of  the  contact  of  a  foreign  body.  But  as  we  know  that  all 
the  trunks,  along  which  these  peculiar  impressions  travel,  do  minister  to  ordi- 
nary sensation,  whilst  the  nerves  of  truly  special  sensation  are  not  sensible 
to  common  impressions,  it  is  evident  that  the  probability  is  in  favour  of  the 
identity  of  the  fibres,  which  minister  to  these  sensations,  with  those  of  the 
usual  sensory  character.  For  the  sense  of  temperature,  however,  it  is  not  by 
any  means  certain  that  a  special  set  of  fibres  does  not  exist ;  for  many  cases 
are  on  record,  in  which  it  has  been  lost,  whilst  the  ordinary  sense  of  tact 
remained;  and  it  is  sometimes  preserved,  when  the  anaesthesia  is  in  other 
respects  complete. 

516.  With  regard  to  all  kinds  of  Sensation  it  is  to  be  remembered,  that  the 
change  of  which  the  mind  is  informed,  is  not  the  change  at  the  peripheral 
extremities  of  the  nerves,  but  the  change  communicated  to  the  sensorium  ; 
hence  it  results,  that  external  agencies  can  give  rise  to  no  kind  of  sensation, 
which  cannot  also  be  produced  by  internal  causes,  exciting  changes  in  the 
condition  of  the  nerves  in  their  course.  This  very  frequently  happens  in 
regard  to  the  senses  of  sight  and  hearing ;  flashes  of  light  being  seen,  and 
ringing  sounds  in  the  ears  being  heard,  when  no  external  stimulus  has  pro- 
duced such  impressions.  The  production  of  odorous  and  gustative  sensations 
from  internal  causes,  is  perhaps  less  common ;  but  the  sense  of  nausea  is 
more  frequently  excited  in  this  manner,  than  by  the  direct  contact  of  the  nau- 
seating substance  with  the  tongue  or  fauces.  The  various  phases  of  common 
sensibility  often  originate  thus ;  and  it  is  an  additional  evidence  in  favour  of 
the  distinctness  of  the  fibres  which  convey  the  impressions  of  temperature, 
that  these  are  frequently  affected, — a  person  being  sensible  of  heat  or  of  chil- 
liness in  some  part  of  his  body,  without  any  real  alteration  of  its  temperature, 
— whilst  there  is  no  corresponding  affection  of  the  tactual  sensations.  The 
most  common  of  the  internal  causes  of  these  subjective  sensations  (as  they 
have  been  termed,  in  contradistinction  to  the  objective,  which  result  from  a 
real  material  object),  is  congestion  or  inflammation  ;  and  it  is  interesting  to 
remark  that  this  cause,  operating  through  each  nerve,  produces  in  the  senso- 
rium the  changes  to  which  that  nerve  is  usually  subservient.  Thus,  conges- 
tion in  the  nerves  of  common  sensation  gives  rise  to  feelings  of  pain  or  un- 
easiness ;  but  when  occurring  in  the  retina  and  optic  nerve  it  produces  flashes 
of  light;  and  in  the  auditory  nerve  it  occasions  "a  noise  in  the  ears." — It 
may  be  observed,  also,  of  some  external  causes,  that  they  may  excite  changes 
in  the  sensorium  through  several  different  channels ;  and  that  in  each  case  the 
sensation  is  characteristic  of  the  particular  nerve,  on  which  the  impression  is 
made.  Thus  pressure,  which  produces  through  the  nerves  of  common  sensa- 
tion the  feeling  of  resistance,  is  well  known  to  occasion,  when  exerted  on  the 
eye,  the  sensation  of  light  and  colours  ;  and,  when  made  with  some  violence 
on  the  ear,  to  produce  tinnitus  aurium.  It  is  not  so  easy  to  excite  sensations 
of  taste  and  smell,  by  mechanical  irritation ;  and  yet,  as  Dr.  Baly*  has  shown, 
it  may  readily  be  accomplished  in  regard  to  the  former.  The  sense  of  nau- 
sea may  be  easily  produced,  as  is  familiarly  known,  by  mechanical  irritation 
of  the  fauces.  The  stimulus  of  Electricity  still  more  completely  possesses 
the  power  of  affecting  all  the  sensory  nerves,  with  the  changes  which  are  pe- 
culiar to  them;  for,  by  proper  management,  an  individual  may  be  made  con- 
scious at  the  same  time  of  flashes  of  light,  of  distinct  sounds,  of  a  phosphoric 
odour,  of  a  peculiar  taste,  and  of  pricking  sensations,  all  excited  by  the  same 
cause,  the  effects  of  which,  are  modified,  according  to  the  respective  peculi- 
arities of  the  instruments  through  which  it  operates. — But  although  there  are 
some  stimuli  which  can  produce  sensory  impressions  on  all  the  nerves  of 

*  Translation  of  Mviller's  Physiology,  p.  1062,  note. 


392  ON  SENSATION,  AND  THE  ORGANS  OF  THE  SENSES. 

sensation,  it  will  be  found  that  those,  to  which  any  one  organ  is  peculiarly 
fitted  to  respond,  produce  little  or  no  effect  upon  the  rest.  Thus  the  ear  can- 
not distinguish  the  slightest  difference  between  a  luminous  and  a  dark  object. 
A  tuning-fork,  which,  when  laid  upon  the  ear  whilst  vibrating,  produces  a  dis- 
tinct musical  tone,  excites  no  other  sensation  when  placed  upon  the  eye  than 
a  slight  jarring  feeling.  The  most  delicate  touch  cannot  distinguish  a  sub- 
stance which  is  sweet  to  the  taste  from  one  which  is  bitter;  nor  can  the  taste 
(if  the  communication  between  the  mouth  and  the  nose  be  cut  off)  perceive 
anything  peculiar,  in  the  most  strongly  odoriferous  bodies. 

517.  It  may  hence  be  inferred  that  no  nerve  of  special  sensation  can,  by 
any  possibility,  take  on  the  function  of  another.     How  far  the  nerves  of  com- 
mon sensation,  can,  under  any  circumstances,  perform  the  offices  usually 
delegated  to   those  of  special  sense,  we  are  not  yet  in  a  condition  to  deter- 
mine.    Comparative  Anatomy  seems  to  show  that,  in  the  lowest  animals  in 
which  the  rudiments  of  eyes  can  be  detected,  there  is  no  distinction  between 
the  nerves  proceeding  to  these  organs,  and  the  rest ;  and  there  would  appear 
some  ground  for  the  belief  that,  as  in  other  cases,  the  special  organs  of  sensi- 
bility are  gradually  elaborated,  in  ascending  the  Animal  scale,  from  the  more 
general  apparatus,  and  are  not  merely  superadded  to  it.'    Hence  we  may  con- 
ceive the  possibility  (though  there  is  no  proof  of  the  fact)  that  states  of  the 
system  might  occur,  in  which  a  change  in  the  common  sensory  nerves  might 
produce  the  sensation  of  light,  sound,  &c.     But  it  is  quite  impossible  (so  far 
at  least  as  our  present  knowledge  of  physical  phenomena  permits  us  to  decide 
upon  the  impossibility  of  anything)  that  distinct  visual  impressions  should  be 
communicated  to  a  nerve,  except  through  the   mediation  of  such  an  optical 
instrument  as  the  eye ;  or  distinct  sonorous  impressions,  except  through  such 
an  acoustic  instrument  as  the  ear.     Hence  we  must  receive  with  the  greatest 
caution  the  wonderful  accounts  of  transference  of  sensation,  many  of  which 
have  undoubtedly  been  the  offspring  of  deception.     Still  it  may  be  objected 
that,  since  we   are  so  totally  destitute  of  real  knowledge,  as  to  the  mode  in 
which  vision  is  ordinarily  produced  by  inverted  images  upon  the  retina,  we 
have  no  right  to  assert  that  it  may  not  take  place  in  some  other  way ;  and 
perhaps  this  objection  should  lead  us  to  consider  the  phenomenon  rather  as 
extremely  improbable,  than  as  impossible.     But  the  improbability  may  be 
compared  to  that  of  a  stone  ascending  like  a  balloon,  or  a  piece  of  lead  float- 
ing on  the  water ;  for  we  have  no  more  knowledge  of  the  ultimate  cause  of 
that  which  we  term   the  force  of  Gravitation,  than  we  have  of  the  nature  of 
Sensation. 

518.  The  peculiar  aptitudes  of  the  different  Sensory  nerves,  to  receive 
and  convey  impressions  of  various  kinds,  must  be  regarded  as  the  result  of 
properties  inherent  in  themselves ;  just  as  we  consider  the  difference  between 
the  afferent  nerves  in  general,  and  the  motor  nerves,  to  be  one  belonging  to 
their  own  constitution.     But  it  is  probable  that  there  are  also  different  locali- 
ties in  the  Sensorium,  in  which  the  changes  to  which  they  give  rise  are  per- 
formed.    This  may  be  judged  of  from  the  fact,  that  the  phenomena  of  sub- 
jective sensation  frequently  originate  in  peculiar  conditions  of  the  encephalon 
itself,  and  not  in  the  nervous  trunks  or  organs  of  sense  ;  thus,  in  dreaming, 
we  have  frequently  very  vivid  pictures  of  external  objects  presented  to  our 
minds;  and  we  sometimes  distinctly  hear  voices  and  musical  tones,  or  have 
perceptions  (though  this  is  less  common)  of  tastes   and  odours.     The  phe- 
nomena of  spectral  illusions  are  very  nearly  connected  with  those  of  dream- 
ing; both  may  be  in  some  degree  influenced  by  external  causes,  acting  upon 
the  organs  of  sensation,  which  are  misinterpreted  (as  it  were)  by  the  mind, 
owing  to  its  state  of  imperfect  operation ;  but  both  also  may  entirely  originate 
in  the  central  organs.     There  seems  to  be  no  difference,  in  the  feelings  of  the 


OF  SENSATION  IN  GENERAL.  393 

individual,  between  the  sensations  thus  originating,  and  those  which  are  pro- 
duced in  the  usual  manner ;  for  we  find  that,  unless  otherwise  convinced  by 
their  own  reason,  persons  who  witness  spectral  illusions  believe  as  firmly  in 
the  reality  of  the  objects  that  come  before  their  minds,  as  if  the  images  of 
those  objects  were  actually  formed  on  their  retinae.  This  is  another  proof,  if 
any  were  wanting,  that  the  organ  of  sense,  and  the  nerve  belonging  to  it,  are 
but  the  instruments  by  which  certain  changes  are  produced  in  the  sensorium; 
of  which  changes,  and  not  of  the  immediate  impression  of  the  object,  the 
sensation  really  consists.  It  seems  to  be  by  an  innate  law  of  our  constitution, 
that  these  subjective  sensations,  whether  originating  in  the  central  organs,  or 
in  the  course  of  the  nervous  trunks,  should  be  referred  by  the  mind  to  the 
ordinary  situations  of  the  peripheral  terminations  of  those  nerves ;  even 
though  these  should  not  exist,  or  should  be  destitute  of  the  power  of  receiv- 
ing impressions.  Thus  after  amputations,  the  patients  are  for  some  time 
affected  with  sensations  (originating  probably  in  the  cut  extremities  of  the 
nerves),  which  they  refer  to  the  removed  extremities;  the  same  has  been 
noticed  in  regard  to  the  eye,  as  well  when  it  has  been  completely  extirpated, 
as  when  its  powers  have  been  destroyed  by  disease.  The  effects  of  the 
Taliacotian  operation  also  exhibit  the  operation  of  this  law  in  a  curious  man- 
ner; for  until  the  flap  of  skin,  from  which  the  new  nose  is  formed,  obtains 
vascular  and  nervous  connections  in  its  new  situation,  the  sensation  produced 
by  touching  it  is  referred  to  the  forehead.  Another  interesting  illustration  of 
it  may  be  obtained  by  the  following  very  simple  experiment : — if  the  middle 
finger  of  either  hand  be  crossed  behind  the  fore-finger,  so  that  its  extremity  is 
on  the  radial  side  of  the  latter,  and  the  ends  of  the  two  fingers  thus  disposed 
be  rolled  over  a  marble,  pea,  or  other  round  body,  a  sensation  will  be  pro- 
duced, which,  if  uncorrected  by  reason,  would  cause  the  mind  to  believe  in 
the  existence  of  two  distinct  bodies ;  this  is  due  to  the  impression  being  made 
at  the  same  time  upon  the  radial  side  of  the  fore-finger,  and  the  ulnar  side  of 
the  middle  finger, — two  joints  which,  in  the  natural  position,  are  at  a  con- 
siderable distance. 

519.  The  acuteness  of  particular  sensations  is  influenced  in  a  remarkable 
degree  by  the  attention  they  receive  from  the  mind.  If  the  mind  be  entirely 
inactive,  as  in  profound  sleep,  no  sensation  whatever  is  produced  by  ordinary 
impressions ;  on  the  other  hand,  when  the  mind  is  from  any  cause  strongly 
directed  upon  them,  impressions  very  feeble  in  themselves  produce  sensations 
of  even  painful  acuteness.  Every  one  knows  how  much  a  slight  itching  of 
some  part  of  the  surface  may  be  magnified,  by  the  direction  of  the  thoughts 
to  it;  whilst  as  soon  as  they  are  forced  by  some  stronger  impression  into  ano- 
ther channel,  the  irritation  is  no  longer  felt.  Every  one  is  aware  how  vividly 
sounds  are  perceived,  when  they  break  in  upon  the  stillness  of  the  night;  being 
increased  in  strength,  not  only  by  the  contrast,  but  by  absorbing  the  whole 
attention.  An  interesting  experiment  is  mentioned  by  Miiller,  which  shows 
how  completely  the  mind  may  be  unconscious  of  impressions  communicated 
to  it  by  one  organ  of  sense,  when  occupied,  even  without  a  distinct  effort  of 
the  will,  by  those  received  through  another.  If  we  look  at  a  sheet  of  white 
paper  through  two  differently-coloured  glasses  at  the  same  time — one  being 
placed  before  each  eye, — the  resulting  sensation  is  seldom  that  of  a  mixture 
of  the  colours :  if  the  experiment  be  tried  with  blue  and  yellow  glasses,  for 
example,  we  do  not  see  the  paper  of  an  uniform  green ;  but  the  blue  is  pre- 
dominant at  one  moment,  and  the  yellow  at  another;  or  blue  nebulous  spots 
may  present  themselves  on  a  yellow  field,  or  yellow  spots  on  a  blue  field. 
We  perceive  from  this  experiment,  that  the  attention  may  not  only  be  directed 
to  the  impressions  made  on  either  retina,  to  the  complete  exclusion  of  those  of 


394  ON  SENSATION,  AND  THE  ORGANS  OF  THE  SENSES. 

the  other,  but  it  may  be  directed  to  those  made  on  particular  spots  of  either. 
This  may  be  noticed,  again,  in  the  process  by  which  we  make  ourselves  ac- 
quainted with  a  landscape  or  a  picture ;  if  our  attention  be  directed  to  the  whole 
field  of  vision  at  once,  we  see  nothing  distinctly ;  and  it  is  only  by  abstracting 
ourselves  from  the  contemplation  of  the  greater  part  of  it,  and  by  directing 
our  attention  to  smaller  portions  in  succession,  that  we  can  obtain  a  definite 
conception  of  the  details.  The  same  is  the  case  in  regard  to  auditory  impres- 
sions ;  and  here  the  power  of  attention,  in  causing  one  sensation  or  series  of 
sensations  to  predominate  over  others  which  are  really  more  intense,  is  often 
most  remarkably  manifested.  When  we  are  listening  to  a  piece  of  music 
played  by  a  large  orchestra,  for  example,  we  may  either  attend  to  the  combined 
effect  of  all  the  instruments,  or  we  may  single  out  any  one  part  in  the  har- 
mony, and  follow  this  through  all  its  mazes ;  and  a  person  with  a  practised  ear 
(as  it  is  commonly  but  erroneously  termed,  it  being  not  the  ear  but  the  mind 
that  is  practised),  can  even  distinguish  the  sound  of  the  weakest  instrument 
in  the  whole  band,  and  can  follow  its  strajn  through  the  whole  performance. 
This  attention  to  a  single  element  can  only  be  given,  however,  by  withdrawing 
the  mind  from  the  perception  of  the  rest ;  and  a  musician  who  thus  listens, 
will  have  very  little  idea  of  the  rest  of  the  harmonic  parts,  or  of  the  general 
effect.  In  fact,  when  the  mind  is  thus  directed,  by  a  strong  effort  of  the  will, 
into  a  particular  channel,  it  may  be  almost  considered  as  unconscious  quoad 
any  other  impressions. 

520.  The  effects  of  this  principle  are  manifested. in  regard  to  the  sensations 
which  originate  within  the  system ;  as  well  as  in  respect  to  those  which  are 
excited  by  external  impressions.     Every  one  is  aware  how  difficult  it  is  to 
keep  the  body  perfectly  quiescent,*  especially  when  there  is  a  particular  mo- 
tive for  doing  so,  and  when  the  attention  is  strongly  directed  to  the  object. 
This  is  experienced  even  whilst  a  Photogenic  likeness  is  being  taken,  when 
the  position  is  chosen  by  the   individual,  and   a  support  is  adapted  to  assist 
him  iii  retaining  it;  and  it  is  still  more  strongly  felt  by  the  performers  in  the 
Tableaux  Vivans,  who  cannot  keep  up  the  effort  for  more  than  three  or  four 
minutes.     Now  it  is  well  known  that,  when  the  attention  is  strongly  directed 
to  an  entirely  different  object  (when  we  are  listening,  for  example,  to  an  elo- 
quent sermon,  or  an  interesting  lecture),  the  body  may  remain  perfectly  mo- 
tionless for  a  much  longer  period  j  the  uneasy  sensations,  which  would  other- 
wise have  occasioned  the  individual  to  change  his  position,  not  being  felt;  but 
no  sooner  is  the  discourse  ended,  than  a  simultaneous  movement  of  the  whole 
audience  takes  place,  every  one  then  becoming  conscious  of  some  discomfort, 
which  he  seeks  to  relieve.    This  is  the  case,  also,  in  regard  to  the  respiratory 
sensation ;  in  general  it  may  be  observed,  that  the  usual  reflex  movements  are 
not  enough  for  the  perfect  aeration  of  the  blood,  and  that  a  more  prolonged 
inspiration  prompted  by  an  uneasy  feeling,  takes  place  at  intervals ;  but  under 
such  circumstances  as  those  just  alluded  to,  this  feeling  is  not  experienced,  until 
the  attention  ceases  to  be  engaged  by  a  more  powerful  stimulus,  and  then  it 
manifests  itself  by  the  deep  inspirations  which  accompany,  in  almost  every 
individual,  the  general  movement  of  the  body. 

52 1 .  It  is  curious  that  the   constant  direction  of  the  attention  to  internal 
sensations  of  &  subjective  kind,  should  sometimes  occasion  actual  disorder  of 
the  parts  to  which  these  sensations  are  referred ;  and  yet  this  seems  the  only 
way  of  accounting  for  some  of  the  phenomena  of  disease.     Sometimes  the 
cause  of  the  sensation  may  exist  in  the  trunk  of  the  nerve,  in  some  part  of  its 
course;  whilst  in  other  instances,  it  may  be  confined  to  the  sensorium.    Pain 

*  Of  course  the  movements  of  respiration  and  winking  are  left  out  of  the  question. 


SENSE  OF  TOUCH.  395 

of  the  testicle,  for  example,  may  be  occasioned  by  irritation  having  its  seat 
in  the  lower  part  of  the  spine,  the  organ  itself  being  perfectly  sound ;  yet  if 
that  pain  continue,  it  may  become  diseased.  The  following  are  some  very 
interesting  remarks  on  this  subject,  from  the  able  pen  of  Dr.  Holland.* 
"  There  is  cause  to  believe  the  action  of  the  heart  to  be  quickened  or  other- 
wise disturbed,  by  the  mere  centering  of  consciousness  upon  it,  without  any 
emotion  or  anxiety."  This  is  especially  the  case  where  its  impulses  are 
irregular,  or  are  so  loud  as  to  be  audible.  "  The  same  may  be  said  of  the 
parts  concerned  in  respiration.  If  this  act  be  expressly  made  the  subject  of 
consciousness,  it  will  be  felt  to  undergo  some  change  ;  generally  to  be  retarded 
at  first,  and  afterwards  quickened."  "  The  act  of  swallowing  is  manifestly 
rendered  more  difficult,  by  the  attention  being  fixed  upon  it ;  and  the  same 
cause  will  often  be  found  to  render  articulation  less  distinct,  especially  when 
there  exists  already  some  impediment  to  the  function.  A  similar  direction  of 
consciousness  to  the  region  of  the  stomach,  creates  in  this  part  a  sense  of 
weight,  oppression,  or  other  less  definite  uneasiness  ;  and,  when  the  stomach 
is  full,  appears  greatly  to  disturb  the  due  digestion  of  the  food.  The  state 
and  action  of  the  bowels  are  much  influenced  by  the  same  cause."  A  pecu- 
liar sense  of  weight  and  restlessness  approaching  to  cramp,  is  felt  in  a  limb, 
to  which  the  attention  is  particularly  directed.  "  The  attention  concentrated, 
for  so  by  an  effort  of  will  it  may  be,  on  the  head  or  sensorium,  gives  certain 
feelings  of  tension  and  uneasiness,  caused  possibly  by  some  change  in  the 
circulation  of  the  part ;  though  it  may  be  an  effect,  however  difficult  to  be 
conceived,  on  the  nervous  system  itself.  Persistence  in  this  effort,  which  is 
seldom  indeed  possible  beyond  a  short  time  without  confusion,  produces  results 
of  much  more  complex  nature,  and  scarcely  to  be  defined  by  any  common  terms 
of  language."  These  phenomena  have  an  evident  affinity,  on  the  one  hand, 
with  the  exaltation  of  external  or  objective  sensations,  to  which  the  attention 
is  peculiarly  directed;  and  on  the  other  with  those  of  several  morbid  condi- 
tions. The  explanation  of  them  all  is  probably  to  be  sought  in  some  change 
in  the  circulation  of  the  part,  to  which  the  sensation  is  referred.  Thus  the 
hypochondriac  patient,  **  in  fixing  his  consciousness  with  morbid  intentness  on 
certain  organs,  creates  not  merely  disordered  sensations,  but  often  also  disor- 
dered actions  in  them.  There  may  be  palpitation  of  the  heart,  hurried  or 
choked  respiration,  flatulence  and  other  distress  of  stomach,  irritation  of  the 
bladder;  all  arising  from  this  morbid  direction  of  attention  to  the  organs  in 
question."  In  hysteria,  again,  "  the  instances  are  frequent,  of  attacks  brought 
on  by  the  mere  expectation  of  them ;  or  by  irritation ;  or  occasionally  even  a 
sort  of  morbid  solicitation  of  the  organs  to  these  singular  actions."  These 
facts  go  a  long  way  to  explain  the  phenomena  of  Mesmerism,  many  of  which 
are  obviously  to  be  referred  to  the  exaggerated  operation  of  the  same  principle. 
(See  Appendix.) — We  now  proceed  to  consider  in  more  detail  the  functions  of 
the  several  Organs  of  the  Senses,  and  shall  commence  with  that  of  the  most 
general  character. 

2.  Sense  of  Touch. 

522.  By  the  sense  of  Touch,  as  commonly  understood,  is  meant  that  mo- 
dification of  the  common  sensibility  of  the  body,  of  which  the  Cutaneous  sur- 
face is  the  especial  seat.  It  derives  its  peculiar  power  simply  from  the  large 
amount  of  sensory  nervous  fibres,  which  are  distributed  in  its  substance;  and 
especially  through  the  terminations  (or  rather  the  origins)  of  these  in  the  pa- 
pillae, which  are  little  elevations  of  the  surface  of  the  cutis,  easily  perceptible 

*  Medical  Notes  and  Reflections,  Chap,  v. 


396 


ON  SENSATION,  AND  THE  ORGANS  OF  THE  SENSES. 


162. 


Capillary  net-work  at  margin   of 
lips. 


by  the  aid  of  a  lens,  and  each  chiefly  composed  of  a  vascular  loop  overlapping 

the  extremity  of  the  nervous  fibril.  The  pre- 
cise arrangement  of  the  nerve-fibres  in  the  cuta- 
neous papillae,  has  not  been  indisputably  ascer- 
tained ;  but  the  opinion  that  they  form  loops 
(Fig.  119)  is  the  one  most  generally  adopted. 
The  number  of  these  papillae  within  any  given 
area,  pretty  closely  corresponds  with  the  degree 
of  sensibility  of  that  part  of  the  surface ;  thus 
we  find  them  most  abundant  on  the  hands,  es- 
pecially towards  the  points  of  the  fingers,  and 
on  the  lips  and  tongue.  In  some  animals,  es- 
pecially those  of  the  Feline  tribe,  the  long  vi- 
brissas  (commonly  termed  whiskers)  evidently 
minister  to  sensation;  and  it  has  been  demonstrated  that  their  pulps  are 
largely  supplied  with  nerves  from  the  fifth  pair.  Some  interesting  observa- 
tions have  been  made  by  Prof.  Weber,  on  the  sensibility  of  different  parts  of 
the  skin.  His  mode  of  ascertaining  this,  was  to  touch  the  surface  with  the 
legs  of  a  pair  of  compasses,  the  points  of  which  were  guarded  with  pieces  of 
cork  ;  the  eyes  being  closed  at  the  time,  the  legs  were  approximated  to  each 
other,  until  they  were  brought  within  the  smallest  distance,  at  which  they 
could  be  felt  to  be  distinct  from  one  another.  The  following  are  some  of  the 
results  of  the  experiments.  With  the  extremities  of  the  fingers  and  the 
point  of  the  tongue,  the  distance  could  be  distinguished  most  easily  in  the 
longitudinal  direction  ;  on  the  dorsum  of  the  tongue,  the  face,  neck,  and  ex- 
tremities, the  distance  could  be  recognized  best  when  the  points  were  placed 
transversely. 


Point  of  middle  finger    .         .  £  of  a  line 

Point  of  tongue     .         .         .  $  of  a  line 

Palmar  surface  of  third  finger  1  line 

Red  surface  of  lips        .         .  2  lines 
Palmar  surface  of  middle  finger  2     „ 

Dorsal  surface  of  third  finger  3     „ 

Tip  of  the  nose     .         .  3     ,, 

Dorsum  and  edge  of  tongue  4     „ 

Part  of  lips  covered  by  skin  4     „ 

Palm  of  hand      • .         .         .  5     „ 

Skin  of  cheek       .         .  5     „ 

Extremity  of  great  toe   .  5     „ 

Hard  palate  .         .         .  6     „ 

Dorsal  surface  of  forefinger    .  7     „ 

Dorsum  of  hand    .  8     , 


Mucous  Membrane  of  gums 

Lower  part  of  forehead 

Lower  part  of  occiput 

Back  of  hand    . 

Neck,  under  lower  jaw 

Vertex     . 

Skin  over  Patella 

Sacrum     . 


Dorsum  of  foot 
Skin  over  sternum    . 
Skin  beneath  occiput 
Skin  over  spine,  in  back 
Middle  of  the  arm    . 
thigh 


9  lines 

10  „ 

12  „• 

14  „ 

15  „ 

15  „ 

16  „ 
18  „ 
18  „ 
18  „ 
20  „ 
24  „ 
30  „ 
30  „ 
30  , 


It  is  curious  that  the  distance  between  the  legs  of  the  compasses  seemed  to 
be  greater  (although  really  so  much  less),  when  it  was  felt  by  the  more  sensi- 
tive parts,  than  when  it  was  estimated  by  parts  of  less  distinct  sensibility.  As 
a  general  fact,  it  seems  that  the  sensibility  of  the  trunk  is  greater  on  the  me- 
dian line,  both  before  and  behind,  and  less  at  the  sides.  Differences  of  tem- 
perature, and  the  weight  of  bodies,  were,  according  to  Prof.  Weber's  observa- 
tions, most  accurately  recognized  at  the  parts,  which  were  determined  to  be 
most  sensible  by  the  foregoing  method  of  inquiry. 

523.  As  already  stated(§  514),  the  only  idea  communicated  to  our  minds  by 
the  sense  of  Touch,  when  exercised  in  its  simplest  form,  is  that  of  Resistance ; 
but  when  the  sensory  surface  and  the  substance  touched  are  made  to  change 
their  place  in  regard  to  each  other,  we  obtain  the  additional  notion  of  Extension 
or  Space.  By  the  various  degrees  of  resistance  which  the  sensory  surface 
encounters,  we  estimate  the  hardness  or  softness  of  the  body;  but  in  this  we 


SENSE  OF  TOUCH.       v  397 

are  assisted  by  the  muscular  sense  (§  433),  which  makes  us  conscious  of  the 
degree  of  pressure  we  are  employing.  By  the  impressions  made  upon  the 
papillae,  during  the  movement  of  the  tactile  surface  over  that  which  is  being 
examined,  the  roughness,  smoothness,  or  other  peculiar  characters,  of  the  lat- 
ter are  estimated,  Our  knowledge  of  form,  however,  is  a  very  complex  pro- 
cess, requiring  not  merely  the  exercise  of  the  sense  of  touch,  but. also  great 
attention  to  the  muscular  sensations.  It  is  chiefly,  as  formerly  remarked,  in 
the  variety  of  movements  of  which  the  hand  of  Man  is  capable,  that  it  is 
superior  to  that  of  any  other  animal ;  and  it  cannot  be  doubted  that  this  affords 
a  very  important  means  of  acquiring  information  in  regard  to  the  external 
world,  and  especially  of  correcting  many  vague  and  fallacious  notions,  which 
we  should  derive  from  the  sense  of  Sight,  if  used  alone.  On  the  other  hand, 
it  must  be  confessed,  that  our  knowledge  would  have  a  very  limited  range,  if 
this  sense  were  the  only  medium,  through  which  we  could  acquire  ideas.  It 
is  probably  on  the  sensations  communicated  through  the  touch,  that  the  idea 
of  the  material  world,  as  something  external  to  ourselves,  chiefly  rests ;  but 
this  idea  is  by  no  means  a  direct  result  of  these  sensations,  being  rather  an 
instinctive  or  intuitive  perception  excited  by  them.  Every  person  who  directs 
the  least  attention  to  the  subject  must  perceive,  how  completely  different  are 
those  notions  of  the  primary  or  elementary  properties  of  matter,  which  we 
base  upon  the  information  thus  communicated  to  us,  from  the  sensations  them- 
selves ;  and,  as  Dr.  Alison  has  justly  remarked,  "a  decisive  proof  of  this  being 
the  true  representation  of  this  part  of  our  mental  constitution,  is  obtained  by 
attending  to  the  idea  of  extension  or  space ;  which  is  undoubtedly  formed 
during  the  exercise  of  the  sense  of  touch ;  and  is  no  sooner  formed,  than  it 
'  swells  in  the  human  mind  to  Infinity,'  to  which  certainly  no  human  sensation 
can  bear  any  resemblance." 

524.  That  the  conditions  under  which  certain  of  the  modifications  of  com- 
mon sensation  operate,  are  in  some  respects  different  from  those  of  ordinary 
Touch,  is  very  easily  shown.     Thus,  the  feeling  of  tickling  is  excited  most 
readily  in  parts,  which  have  the  least  tactual  sensibility, — the  armpits,  flanks, 
and  soles  of  the  feet ;  whilst  in  the  points  of  the  fingers  it  cannot  be  excited. 
Moreover,  the  nipple  is  very  moderately  endowed  with  ordinary  sensibility ; 
yet  by  a  particular  kind  of  irritation,  a  very  strong  feeling  may  be  excited 
through  it.     Again,  in  regard  to  temperature,  it  is  remarked  by  Weber,  that 
the  left  hand  is  more  sensitive  than  the  right ;  although  the  sense  of  touch  is 
undoubtedly  the  most  acute  in  the  latter.     He  states  that,  if  the  two  hands, 
previously  of  the  same  temperature,  be  plunged  into  separate  basins  of  warm 
water,  that  in  which  the  left  hand  is  immersed  will  be  felt  as  the  warmest, 
even  though  its  temperature  is  somewhat  lower  than  that  of  the  other.     In 
regard  to  the  sensations  of  heat  and  cold,  he  points  out  another  curious  fact, — 
that  a  weaker  impression  made  on  a  large  surface,  seems  more  powerful  than 
a  stronger  impression  made  on  a  small  surface ;  thus,  if  the  forefinger  of  one 
hand  be  immersed  in  water  at  104°,  and  the  whole  of  the  other  hand  be 
plunged  in  water  at  102°,  the  cooler  water  will  be  thought  the  warmer; 
whence  the  well-known  fact,  that  water  in  which  a  finger  can  be  held,  will 
scald  the  whole  hand.     Hence  it  also  follows,  that  minute  differences  in  tem- 
perature, which  are  imperceptible  to  a  single  finger,  are  appreciated  by  plung- 
ing the  whole  hand  into  the  water ;  in  this  manner,  a  difference  of  one-third 
of  a  degree  may  readily  be  detected,  when  the  same  hand  is  placed  succes- 
sively in  two  vessels.    The  judgment  is  more  accurate,  when  the  temperature 
is  not  much  above  or  below  the  usual  heat  of  the  body ;  just  as  sounds  are 
best  discriminated,  when  neither  very  acute  nor  very  grave. 

525.  The  improvement  in  the  sense  of  Touch,  in  those  persons  whose  de- 
pendence upon  it  is  increased  by  the  loss  of  other  senses,  is  well  known  ;  this 

34 


398 


ON  SENSATION,  AND  THE  ORGANS  OF  THE  SENSES. 


is  doubtless  to  be  in  part  attributed  (as  already  remarked)  to  the  increased 
attention  which  is  given  to  the  sensations,  and  in  part  to  an  increased  develop- 
ment of  the  tactile  organs  themselves,  resulting  from  the  frequent  use  of  them. 
The  case  of  Saunderson,  who,  although  he  lost  his  sight  at  two  years  old,  be- 
came Professor  of  Mathematics  at  Cambridge,  is  well  known  ;  amongst  his 
most  remarkable  faculties,  was  that  of  distinguishing  genuine  medals  from 
imitations,  which  he  could  do  more  accurately  than  many  connoisseurs  in  full 
possession  of  their  senses.  The  process  of  the  acquirement  of  the  power  of 
recognizing  elevated  characters  by  the  touch,  is  a  remarkable  example  of  this 
improveability.  When  a  blind  person  first  commences  learning  to  read  in  this 
manner,  it  is  necessary  to  use  a  large  type ;  and  every  individual  letter  must 
be  felt  for  some  time,  before  a  distinct  idea  of  its  form  is  acquired.  After  a 
short  period  of  diligent  application,  the  individual  becomes  able  to  recognize 
the  combinations  of  letters  in  words,  without  forming  a  separate  idea  of  each 
letter  ;  and  can  read  line  after  line,  by  passing  the  finger  over  each,  with  con- 
siderable rapidity.  Now  when  this  power  is  once  thoroughly  acquired,  it  is 
found  that  the  size  of  the  type  may  be  gradually  diminished ;  and  this  seems 
to  indicate,  that  the  sensations  themselves  are  rendered  more  acute,  by  the 
frequent  application  of  them  in  this  direction.  As  an  instance  of  the  correct 
notions  which  may  be  conveyed  to  the  mind,  of  the  forms  and  surfaces  of  a 
great  variety  of  objects,  and  of  the  sufficiency  of  these  notions  for  accurate 
comparison,  the  Author  may  mention  the  case  of  a  blind  friend  of  his  own, 
who  has  acquired  a  very  complete  knowledge  of  Conchology,  both  recent  and 
fossil ;  and  who  is  not  only  able  to  recognize  every  one  of  the  numerous  spe- 
cimens in  his  own  Cabinet,  but  to  mention  the  nearest  alliances  of  a  Shell 
previously  unknown  to  him,  when  he  has  thoroughly  examined  it  by  his 
touch.  Many  instances  are  on  record,  of  the  acquirement,  by  the  blind,  of 
the  power  of  distinguishing  the  colours  of  surfaces,  which  were  similar  in 
other  respects ;  and,  however  wonderful  this  may  seem,  it  is  by  no  means 
incredible.  For  it  is  to  be  remembered  that  the  difference  of  colour  depends 
upon  the  position  and  arrangement  of  the  particles  composing  the  surface, 
which  render  it  capable  of  reflecting  one  ray  whilst  it  absorbs  all  the  rest ;  and 
it  is  quite  consistent  with  what  we  know  from  other  sources,  to  believe  that 
the  sense  of  Touch  may  become  so  refined,  as  to  communicate  a  perception 
of  such  differences. 

526,  The  examples  of  peculiar  acuteness  of  this  sense,  which  we  occa- 
sionally meet  with  among  the  lower  animals,  are  very  interesting,  when 
viewed  in  connection  with  its  improveability  in  Man.  It  was  found  by  Spal- 
lanzani,  that  Bats,  when  deprived  of  sight,  and  (as  far  as  possible)  of  hearing 
and  smelling  also,  still  flew  about  with  equal  certainty  and  safety,  avoiding 
every  obstacle,  passing  through  passages  only  just  large  enough  to  admit  them, 
and  flying  about  places  previously  unknown,  with  the  most  unerring  accuracy, 
and  without  coming  into  collision  with  the  objects  near  which  they  passed. 
He  also  stretched  threads  in  various  directions  across  the  apartment,  with  the 
same  result.  So  astonished  was  he  at  these  curious  facts,  that  he  was  led  to 
attribute  the  phenomenon  to  the  possession  of  a  sixth  sense,  unknown  to  Man. 
Cuvier  was  the  first  to  appreciate  the  real  value  of  these  experiments,  as  afford- 
ing a  proof  of  the  existence  of  the  most  exquisite  tactile  sensibility,  over  the  whole 
surface  of  the  flying  membrane ;  the  naked  surface  and  delicate  structure  of 
which,  appear  well  adapted  to  constitute  the  seat  of  so  important  a  function. 
From  this  view,  therefore,  it  would  appear  that  it  is  by  means  of  the  pulsation  of 
the  wings  on  the  air,  that  the  propinquity  of  solid  bodies  is  perceived,  through 
the  manner  in  which  the  air  reacts  on  their  surface.  It  is  curious  that  the 
instance  which  (so  far  as  we  at  present  know)  is  most  analogous  to  this, 
should  be  met  with  among  the  inhabitants  of  the  deep.  It  is  a  fact  well 


SENSE  OF  TASTE. 


399 


known  to  Whale-fishers,  especially  to  those  who  pursue  the  Spermaceti 
Whale,  that  these  animals  have  the  power  of  communicating  with  each  other 
at  great  distances.  It  has  often  been  observed,  for  example,  that  when  a 
straggler  is  attacked,  at  the  distance  of  several  miles  from  a  shoal,  a  number 
of  its  fellows  bear  down  to  its  assistance,  in  an  almost  incredibly  short  space 
of  time.  It  can  scarcely  be  doubted,  then,  that  the  communication  must  be 
made  through  the  medium  of  the  vibrations  of  the  water,  excited  by  the 
struggles  of  the  animal,  or  perhaps  by  some  peculiar  movements  especially 
designed  for  this  purpose,  and  propagated  through  the  fluid  to  the  large  cuta- 
neous surface  of  the  distant  Whales  ;  and  this  idea  is  fully  confirmed  by 
the  fact,  that  the  nerves  which  proceed  to  the  skin,  pass  through  the  inner 
layers  of  blubber  with  scarcely  any  subdivision,  but  spread  out  into  a  net- 
work of  extreme  minuteness,  as  soon  as  they  arrive  at  the  surface. 

3.  Sense  of  Taste. 

527.  That  this  sense  may  be  really  considered  as  a  peculiar  modification 
of  that  of  Touch,  appears  from  several  considerations.  In  the  first  place,  the 
actual  contact  of  the  object  of  sense,  with  the  organ  through  which  the  im- 
pression is  received,  is  here  necessary ;  and  this  is  the  case  in  regard  to  no 
other  sense.  Moreover  the  intimate 
structure  of  the  organ  is  nearly  the 
same  in  both  instances.  Again,  it  ap- 
pears from  the  considerations  formerly 
alluded  to  (§  407),  that  there  is  no 
special  nerve  of  taste ;  the  gustative 
impressions  made  upon  the  front  of 
the  tongue,  being  conveyed  by  the 
lingual  branch  of  the  fifth  pair  ;  whilst 
those  made  upon  the  back  of  the  organ, 
are  conveyed  by  the  glosso-pharyngeal. 
The  first  of  these  nerves  also  ministers 
to  ordinary  tactile  sensibility ;  the  se- 
cond appears  to  convey  the  impres- 
sions which  produce  nausea.  The 
papillae  of  the  Tongue  are  essentially 
the  same  in  structure  with  those  of 
the  Skin ;  but  many  of  them  are  of  a 
peculiarly  complex  nature. 

a.  The  characters  of  the  papillae  of  the 
tongue  have  recently  undergone  a  very  careful 
examination  by  Messrs.  Todd  and  Bowman 
(Physiological  Anatomy,  Chap.  xv.).  They 
may  be  divided,  in  the  first  place,  into  the 
simple  and  the  compound;  the  former  of  which 
had  previously  escaped  observation,  through 
not  forming  any  apparent  projection. — The 
Simple  papillae  are  scattered  in  the  intervals  of 
compound,  over  the  general  surface  of  the 
tongue;  and  they  occupy  much  of  the  surface 
behind  the  circumvallate  variety,  where  no 
compound  papillas  exist.  They  are  com-  Tongue,  seen  on  its  upper  surface :  a.  One  of 

pletely  buried  and  concealed  beneath  .the  the  circumvallate  papillce.  b.  One  of  the  fungi- 
continuous  sheet  of  epithelium,  and  can  only  form  papillae.  Numbers  of  the  conical  papillae 
be  detected,  when  this  membrane  has  been  are  seen  about  d,  and  elsewhere,  e.  Glottis,  epi- 
removed  by  maceration;  they  are  then  found  glottis,  and  glosso-epiglottidean  folds  of  mucous 

membrane.— From  Scemmering.] 


400 


ON  SENSATION,  AND  THE  ORGANS  OF  THE  SENSES. 


to  have  the  general  characters  of  the  cutaneous  papillae,  but  nerve-tubes  have  not  yet  been 
detected  in  them. 

[Fig.  164. 


A 


Simple  papillae  near  the  base  of  the  tongue:— A.  a,  concealed  under  the  epithelium';  6,  uncovered  by 
it.— Magnified  10  diameters.  B.  a.  Arterial  twig,  supplying  their  capillary  loops,  v.  Vein.  The  vessels 
are  all  contained  within  the  line  b,  b,  of  basement  membrane,  c,  c.  Deeper  epithelial  particles  resting 
on  the  basement  membrane,  d.  Scaly  epithelium  on  the  surface.  The  granular  interior  of  the  papillee 
is  represented  at  e.  c.  Papillae  in  which  the  basement  membrane  is  not  visible;  and  the  deep  layer  of 
epithelium  seems  to  rest  on  the  capillary  loop.— Magnified  200  diam.] 


[Fig.  165. 


Vertical  section  of  one  of  the  circumvallate 
papillae  :— a.  Central  part.  b,  b.  Border,  c,  e. 
Fissure  between  centre  and  border.  The  se- 
condary papillae  are  seen  covered  by  the  epi- 
thelium. Similar  papillae  are  seen,  d,  d,  on  the 
membrane  beyond.— Magn.  8  diam.] 


A.  Compound  papillae  on  the  side  of  the  foramen  caecum,  injected:— a,  a.  Arterial  twigs,    v,  v.  Veins. 
The  capillary  loops  indicate  the  simple  papillae ;  in  one  of  which,  &,  the  injected  matter  has  been  extra- 
vasated  within  the  basement  membrane  of  the  papillae,  the  outline  of  which  is  thus  distinguished,    c. 
Capillary  plexus,  where  no  papillae  exist,    e,  e.  External  surface  of  the  epithelium  of  the  papilla. — 
Magn.  15  diam. 

B.  One  of  the  simple  papillae  of  A  :— a,  v,  v.    Arterial  and  venous  sides  of  the  capillary  loops.    6,  6. 
Basement  membrane,    d.  Deeper  epithelial  particles  resting  on  the  basement  membrane,    s.  Scaly  epi- 
thelium on  the  surface.— Magnified  300  diameters.] 


SENSE  OF  TASTE. 


401 


Fig.  167. 


b.  The  Compound  papillae  are  visible  to  the  naked  eye;  and  have  been  classified,  accord- 
ing to  their  shape,  into  the  rircumvallate,  the  fungiform,  and  the  filiform. — The  Circumval- 
late  or  calyci/brm  papillae  are  eight  or  ten  in  number,  and  are  situated  in  a  V-shaped  line 
at  the  base  of  the  tongue.  Each  consists  of  a  central  flattened  circular  projection  of  the 
mucous  membrane,  surrounded  by  a  tumid  ring  of  about 
the  same  elevation,  from  which  it  is  separated  by  a  narrow 
circular  fissure.  The  surface  of  both  centre  and  border 
is  smooth,  and  invested  by  scaly  epithelium,  which  con- 
ceals a  multitude  of  simple  papillae. — The  Fungiform  pa- 
pillse  are  scattered  singly  over  the  tongue,  chiefly  upon  its 
sides  and  tip.  They  project  considerably  from  the  surface, 
and  are  usually  narrower  at  the  base  than  at  their  summit. 
They  contain  a  complex  capillary  plexus,  the  terminal 
loops  of  which  enter  the  numerous  simple  papillae  that 
clothe  the  surface  of  the  fungiform  body.  They  contain 
nerve-tubes,  in  which  a  looped  arrangement  can  be  traced ; 
and  the  epithelium  which  covers  them  is  so  thin,  as  to  allow 
the  red  colour  of  the  blood  to  be  seen  through  it.  In  this 
manner  they  are  readily  distinguished  from  the  filiform  pa- 
pillse,  among  which  they  lie. — The  Filiform  papillae,  like  the  preceding,  contain  a  plexus  of 

[Fig.  168. 


Capillary  net- work  of  fungiform 
papilla  of  the  tongue. 


A.  Fungiform  papilla,  showing  the  secondary  papillae  on  its  surface,  and  at  a  its  epithelium  covering 
them  over.—  Magnified  35  diameters. 

B.  Another,  with  the  capillary  loops  of  its  simple  papilla?  injected,    a.  Artery,    v.  Vein.   The  groove 
around  the  base  of  some  of  the  fungiform  papillae  is  here  represented,  as  well  as  the  capillary  loops,  c,  c, 
of  some  neighbouring  simple  papilla?.— Magnified  18  diameters.] 

capillaries,  and  a  bundle  of  nerve-fibres,  both  terminating  in  loops,  which  enter  the  simple 
papillae  that  clothe  the  surface  of  the  compound  body;  but  instead  of  being  covered  with 
a  thin  scaly  epithelium,  they  are  furnished  with  bundles  of  long  pointed  processes,  some  of 
which  approach  hairs  in  their  stiffness  and  structure.  These  are  immersed  in  the  mucus  of 
the  mouth,  and  may  be  moved  in  any  direction,  though  they  are  generally  inclined  back- 
wards. 

[Fig.  169. 


Various  forms  of  the  conical  compound  papillae  deprived  of  their  epithelium : — a,  &,  and  especially  c, 
are  the  best  marked,  and  were  provided  with  the  stiflfest  and  longest  epithelium;  their  simple  papillae 
are  more  acuminated,  d>  approaches  the  fungiform  variety  :  e.f,  come  near  the  simple  papillae.—  Mag- 
nified 20  diameters.] 

34* 


402 


ON  SENSATION,  AND  THE  ORGANS  OF  THE  SENSES. 


c.  The  Simple  papillae  which  occur  in  an  isolated  manner,  with  those  which  are  aggre- 
gated in  the  Circumvallate  and  Fungiform  bodies,  doubtless  minister  to  the  sense  of  Taste; 
but  there  seems  much  reason  to  coincide  in  the  opinion  of  Messrs.  Todd  and  Bowman,  with 
regard  to  the  different  office  of  the  Filiform  papillae.  "The  comparative  thickness  of  their 

[Fig.  170. 


A.  Vertical  section  near  the  middle  of  the  dorsal  surface  of  the  tongue : — a,  a.  Fungiform  papillse.  b, 
Filiform  papillae,  with  their  hair-like  processes,    c.  Similar  ones  deprived  of  their  epithelium.— Magni- 
fied 2  diameters. 

B.  Filiform  compound  papillae : — a.  Artery,    v.  Vein.    c.  Capillary  loops  of  the  secondary  papillae. 
b.  Line  of  basement  membrane,    d.   Secondary  papillae,  deprived  of  e,  e,  the  epithelium,  f.  Hair-like 
processes  of  epithelium  capping  the  simple  papillae.— Magnified  25  diameters,    g.  Separated  nucleated 
particles  of  epithelium,  magnified  300  diameters. 

1,  2.  Hairs  found  on  the  surface  of  the  tongue.  3,  4, 5.  Ends  of  hair-like  epithelial  processes,  showing 
varieties  in  the  imbricated  arrangement  of  the  particles,  but  in  all  a  coalescence  of  the  particles  towards 
the  point.  5,  encloses  a  soft  hair.— Magnified  160  diameters.] 

protective  covering,  the  stiffness  and  brush-like  arrangement  of  their  filamentary  productions, 
their  greater  development  in  that  portion  of  the  dorsum  of  the  tongue  which  is  chiefly  em- 
ployed in  the  movements  Of  mastication,  all  evince  the  subservience  of  these  papilla?  to  the 
latter  function,  rather  than  to  that  of  taste ;  and  it  is  evident  that  their  isolation  and  partial 
mobility  on  one  another,  must  render  the  delicate  touch  with  which  they  are  endowed,  more 
available  in  directing  the  muscular  actions  of  the  organ.  The  almost  manual  dexterity  of  the 
organ,  in  dealing  with  minute  particles  of  food,  is  probably  provided  for,  as  far  as  sensibility 
conduces  to  it,  in  the  structure  and  arrangement  of  these  papillae."  It  may  be  added,  that 
the  filiform  papillae  of  Man  seem  to  be  the  rudimentary  forms  of  those  horny  epithelial  pro- 
cesses, which  acquire  so  great  a  development  in  the  tongues  of  the  Carnivora,  and  which  are 
of  such  importance  in  the  abrasion  of  their  food. 


SENSE  OF  TASTE. 
[Fig.  171. 


403 


A.  Secondary  papilla  of  the  conical  class,  treated  with  acetic  acid : — a.  Its  basement  membrane.    6. 
Its  nerve-tube  forming  a  loop.    c.  Its  curly  elastic  tissue.    The  epithelium  in  this  instance  is  not  abund- 
ant ;  but  the  vertical  arrangement  of  its  particles  over  the  apex  of  the  papilla  is  well  seen,  d,  and  illus- 
trates the  mode  of  formation  of  the  hair-like  processes  described  in  the  text. — Mag.  160  diam. 

B.  A  similar  papilla,  deprived  of  its  epithelium :— a.  Basement  membrane,    b.  Tubular  fibre,  probably 
forming  a  loop,  but  its  arch  not  clearly  seen,    c,  c.  Elastic  fibrous  tissue  at  its  base  and  in  its  interior. — 
Magnified  320  diameters. 

c.  Nerves  of  a  compound  papilla  near  the  point  of  the  tongue,  in  which  their  loop-like  arrangement  is 
distinctly  seen.— Magnified  160  diameters.] 

528.  As  a  general  rule,  it  is  a  necessary  condition  of  the  sense  of  Taste, 
that  the  object  should  either  be  in  a  state  of  solution,  or  should  be  soluble  in 
the  moisture  covering  the  tongue ;  if  this  be  not  the  case,  or  if  the  tongue  be 
dry,  a  simple  feeling  of  contact  is  all  that  is  produced.     As  in  the  case  of 
touch,  the  idea  of  the  character  of  the  sapid  body  is  very  imperfect,  unless  it 
is  made  to  move  over  the  gustative  surface ;  and  thus  the  taste  is  very  much 
heightened,  by  the  compression  and  friction  of  the  substance  between  the 
tongue  and  the  palate.     From  all  these  circumstances  it  appears  indisputable, 
that  a  very  strong  analogy  exists  between  Taste  and  Touch  ;  indeed  it  may 
be  questioned,  whether  they  are  not  in  reality  more  closely  allied,  than  is  the 
sense  of  Temperature  with  that  of  Resistance. 

529.  Although  the  Tongue  seems   to  be  the  chief  seat  of  Gustative  sensi- 
bility, yet  this  is  also  possessed,  though  in  a  less  degree,  by  the  palate.     But 
it  is  to  be  remarked  that  the  sensations  produced  by  most  sapid  substances 
are  of  a  complex  kind ;  and  are  in  great  part  due  to  the  organ  of  Smell.     Of 
this  any  one  may  convince  himself,  by  closing  the  nostrils,  and  inspiring  and 
expiring  through  the  mouth  only,  when  holding  in  the  mouth,  or  even  rub- 
bing between  the  tongue  and  the  palate,  some  sapid  substance ;  of  which  the 
taste  is  then  scarcely  recognized,  although  it  is  immediately  perceived,  when 
its  effluvia.are  drawn  into  the  nose.     It  is  well  known  too,  that,  when  the 


404  ON  SENSATION,  AND  THE  ORGANS  OF  THE  SENSES. 

sensibility  of  the  Schneiderian  membrane  is  blunted  by  inflammation  (as  in 
an  ordinary  cold  in  the  head),  the  power  of  distinguishing  flavours  is  very 
much  diminished.  In  fact,  some  Physiologists  are  of  opinion  that  all  our 
knowledge  of  the  flavor  of  sapid  substances  is  received  through  the  Smell ; 
and  this  is  not  improbably  true :  but  it  is  to  be  remembered,  that,  besides 
flavor,  a  sapid  body  may  excite  various  other  sensations,  as  those  of  irritation 
and  pungency  ;  and  of  these,  it  seems  to  be  the  true  function  of  the  sensory 
surface  of  the  mouth,  to  take  cognizance.  Such  sensations  are  evidently  not 
far  removed  from  those  of  ordinary  touch  ;  and  correspond  with  those  which 
may  be  excited  in  the  nostrils,  through  the  medium  of  the  Fifth  pair.  Taken 
in  its  ordinary  compound  acceptation,  the  sense  of  Taste  has  for  its  object  to 
direct  us  in  the  choice  of  food,  and  to  excite  the  flow  of  the  mucus  and  saliva, 
which  are  destined  to  aid  in  the  preparation  of  the  food  for  Digestion.  Among 
the  lower  Animals,  the  instinctive  perceptions  connected  with  this  sense  are 
much  more  remarkable  than  our. own;  thus  an  omnivorous  Monkey  will 
seldom  touch  fruits  of  a  poisonous  character,  although  their  taste  may  be 
agreeable ;  and  animals,  whose  diet  is  restricted  to  some  one  kind  of  food, 
will  decidedly  reject  all  others.  As  a  general  rule,  it  may  be  stated,  that 
substances  of  which  the  taste  is  agreeable  to  us,  are  useful  in  our  nutrition ; 
and  vice  versa :  but  there  are  many  signal  exceptions  to  this. 

530.  Like  other  senses,  that  of  Taste  is  capable  of  being  rendered  more 
acute  by  education ;  and  this  on  the  principles  already  laid  down  in  regard  to 
touch.     The  experienced  wine-taster  can  distinguish  differences  in  age,  purity, 
place  of  growth,  &c.,  between  liquors  that  to  ordinary  judgments  are  alike  ; 
and  the  epicure  can  give  an  exact  determination  of  the  spices  that  are  com- 
bined in  a  particular  sauce,  or  of  the  manner  in  which  the  animal,  on  whose 
flesh  he  is  feeding,  was  killed.     As  in  the  case  of  other  senses,  moreover, 
impressions  made  upon  the  sensory  surface  remain  there  for  a  certain  period  : 
and  this  period  is  for  the  most  part  longer  than  that  which  is  required  for 
the  departure  of  the  impressions  made  upon  the  eye,  the  ear,  or  the  organ  of 
smell.     Every  one  knows  how  long  the  taste  of  some  powerful  substances 
remains  in  the  mouth ;  and  even  of  those  which  make  less  decided  impres- 
sions, the  sensation  remains  to  such  a  degree  that  it  is  difficult  to  compare 
them  at  short  intervals.     Hence  if  a  person  be  blindfolded,  and  be  made  to 
taste  substances  of  distinct,  but  not  widely  different  flavours  (such  as  various 
kinds  of  wine  or  of  spirituous  liquors),  one  after  another  in  rapid  succession, 
he  soon  loses  the  power  of  discriminating  between  them.     In  the  same  man- 
ner, the  difficulty  of  administering  very  disagreeable  medicines  may  be  some- 
times got  over,  by  either  previously  giving  a  powerful  aromatic,  or  by  com- 
bining the  aromatic  with  the  medicine ;  its  strong  impression  in  both  cases 
preventing  the  unpleasant  taste  from  exciting  nausea. 

4.  Sense  of  Smell. 

531.  Of  the  nature  of  Odorous  emanations,  the  Natural  Philosopher  is  so 
completely  ignorant,  that  the  Physiologist  cannot  be  expected  to  give  a  defi- 
nite account  of  the  mode,  in  which  they  produce  sensory  impressions.     Al- 
though it  may  be  surmised  that  they  consist  of  particles  of  extreme  minuteness, 
dissolved  as  it  were  in  the  air,  and  although  this  idea  seems  to  derive  confir- 
mation from  the  fact  that  most  odorous  substances  are  volatile,  and  vice  versa, 
— yet  the  most  delicate  experiments  have  failed  to  discover  any  diminution  in 
weight,  in  certain  substances  (as  musk)  that  have  been  impregnating  with  their 
effluvia  a  large  quantity  of  air  for  several  years ;  and  there  are  some  volatile 
fluids,  such  as  water,  which  are    entirely  inodorous.     The    true  Olfactory 
nerves  pass  down  from  the  Olfactory  Ganglion  (§  422)  in  the  fo.rm  of  very 


SENSE  OF  SMELL.  405 

numerous  minute  threads,  which  form  a  plexus  upon  the  surface  of  the 
Schneiderian  or  Pituitary  membrane.  Nothing  satisfactory  is  known  in  re- 
gard to  their  ultimate  arrangement ;  but  it  is  probable  that  they  form  loops, 


Fig.  172. 


The  Olfactory  nerve,  with  its  distribution  on  the  septum  nasi.  The  nares  have  been  divided  by  a  longi- 
tudinal section  made  immediately  to  the  left  of  the  septum,  the  right  nares  being  preserved  entire.  1. 
The  frontal  sinus.  2.  The  nasal  bone.  3.  The  crista  galli  process  of  the  ethmoid  bone.  4.  The  sphe- 
noidal  sinus  of  the  left  side.  5.  The  sella  turcica.  6.  The  basilar  process  of  the  sphenoid  and  occipital 
bones.  7.  The  posterior  opening  of  the  right  nares.  8.  The  opening  of  the  Eustachian  tube  in  the  upper 
part  of  the  pharynx.  9.  The  soft  palate,  divided  through  its  middle.  10.  Cut  surface  of  the  hard  palate, 
a.  The  olfactory  peduncle,  b.  Its  three  roots  of  origin,  c.  Olfactory  ganglion,  from  which  the  filaments 
proceed  that  spread  out  in  the  substance  of  the  pituitary  membrane,  d.  The  nasal  nerve,  a  branch  of 
the  ophthalmic  nerve,  descending  into  the  left  nares  from  the  anterior  foramen  of  the  cribriform  plate,  and 
dividing  into  its  external  and  internal  branch,  e.  The  naso-palatine  nerve,  a  branch  of  the  spheno-pala- 
tine  ganglion  distributing  twigs  to  the  mucous  membrane  of  the  septum  nasi  in  its  course  to  (/)  the  ante- 
rior palatine  foramen,  where  it  forms  a  smali  gangliform  swelling  (Cloquet's  ganglion)  by  its  union  with 
its  fellow  of  the  opposite  side.  g.  Branches  of  the  naso-palatine  nerve  to  the  palate.  A.  Posterior  pala- 
tine nerves,  i,  i.  The  septum  nasi. 

similar  to  those  of  the  cutaneous  nerves.  It  would  appear  that  every  part  of 
the  Schneiderian  membrane  is  not  equally  endowed  with  the  faculty  of  dis- 
tinguishing odours,  which  is  a  very  different  power  from  that  of  becoming 
sensible  of  irritation  from  them.  The  Olfactory  nerves  cannot  be  traced  to 
the  membrane  covering  the  middle  and  inferior  spongy  bones,  or  to  that  which 
lines  the  different  sinuses,  these  parts  of  the  surface  being  supplied  by  the 
Fifth  pair  only ;  and  it  is  a  matter  of  common  experience,  that  we  cannot  dis- 
tinguish faint  odours,  unless,  by  a  peculiar  inspiratory  effort,  we  draw  the  air 
charged  with  them  to  the  upper  part  of  the  nose.  In  animals  living  in  the 
air,  it  is  a  necessary  condition  of  the  exercise  of  the  sense  of  Smell,  that  the 
odorous  matter  should  be  transmitted  by  a  respiratory  current  through  the 
nostrils;  and  that  the  membrane  lining  these  should  be  in  a  moist  state. 
Hence,  by  breathing  through  the  mouth,  we  may  avoid  being  affected  by 
odours  even  of  the  strongest  and  most  disagreeable  kind;  and  in  the  first  stage 
of  a  catarrh,  when  the  ordinary  mucous  secretion  is  suspended,  the  sense  of 
smell  is  blunted  from  this  cause,  as  it  afterwards  is  from  the  excess  in  the 
quantity  of  the  fluid,  which  prevents  the  odoriferous  effluvia  from  coming 
into  immediate  relation  with  the  sensory  extremities  of  the  nerves.  Hence 
we  may  easily  comprehend,  that  section  of  the  Fifth  pair,  which  exercises  a 


406 


ON  SENSATION,  AND  THE  ORGANS  OF  THE  SENSES. 


considerable  control  over  the  secretion's,  will  greatly  diminish  the  acuteness  of 
the  smell ;  and  it  will  have  the  further  effect  of  preventing  the  reception  of 
any  impressions  of  irritation  from  acrid  vapours,  which  are  entirely  different 
in  their  character  from  true  odorous  impressions,  and  which  are  not  trans- 
mitted through  the  Olfactory  nerve  (§  441).  The  nasal  passages  may  indeed 
be  considered  as  having,  in  the  air-breathing  Vertebrata,  two  distinct  offices ; 
they  constitute  the  organ  of  smell,  through  the  distribution  of  the  olfactory 
nerve  upon  a  part  of  their  surface ;  but  they  also  constitute  the  portals  of  the 
respiratory  organs,  having  for  their  office  to  take  cognizance  of  the  aeriform 
matter  which  enters  them,  and  to  give  warning  of  that  which  would  be  inju- 
rious ;  this  latter  function  is  performed  by  the  Fifth  pair,  as  by  the  Par  Vagum 
in  the  glottis.  It  is  through  this  nerve,  that  the  act  of  sneezing  is  excitable  : 
the  evident  purpose  of  which,  is  the  ejection  of  a  strong  blast  of  air  through 
the  nasal  passages,  in  such  a  manner  as  to  drive  out  any  offending  matter 
they  may  contain. 

532.  The  importance  of  the  sense  of  Smell  among  many  of  the  lower 
Animals,  in  guiding  them  to  their  food,  or  in  giving  them  warning  of  danger 
and  also  in  exciting  the  sexual  feelings,  is  well  known.  To  Man  its  utility 
is  very  subordinate  under  ordinary  circumstances ;  but  it  may  be  greatly  in- 
creased when  other  senses  are  deficient.  Thus,  in  the  well-known  case  of 
James  Mitchell,  who  was  deaf,  blind  and  dumb,  from  his  birth,  it  was  the 
principal  means  of  distinguishing  persons,  and  enabled  him  at  once  to  per- 
ceive the  entrance  of  a  stranger.  It  is  recorded  that  a  blind  gentleman,  who 
had  an  antipathy  to  cats,  was  possessed  of  a  sensibility  so  acute  in  this  re- 
spect, that  he  perceived  the  proximity  of  one  that  had  been  accidentally  shut 
up  in  a  closet  adjoining  his  room.  Among  Savage  tribes,  whose  senses  are 
more  cultivated  than  those  of  civilized  nations,  more  direct  use  being  made  of 
the  powers  of  observation,  the  scent  is  almost  as  acute  as  in  the  lower  Mam- 
malia; it  is  asserted  by  Humboldt,  that  the  Peruvian  Indians  in  the  middle  of 
the  night  can  thus  distinguish  the  different  races, — whether  European,  Ameri- 
can-Indian, or  Negro.*  The  agreeable  or  disagreeable  character  assigned  to 
particular  odours,  is  by  no  means  constant  amongst  different  individuals. 
Many  of  the  lower  Animals  pass  their  whole  lives  in  the  midst  of  odours, 
which  are  to  Man  (in  his  civilized  condition  at  least)  in  the  highest  degree 
revolting ;  and  will  even  refuse  to  touch  food,  until  it  is  far  advanced  in  pu- 
tridity. It  more  frequently  happens  in  regard  to  odours  and  savours,  than 
with  respect  to  other  sensory  impressions,  that  habit  makes  that  agreeable, 
and  even  strongly  relished,  which  was  at  first  avoided;  the  taste  of  the  epi- 
cure for  game  that  has  acquired  ihefumet, — for  olives, — for  assafoetida,  &c., 
are  instances  of  this.  As  to  the  length  of  time,  during  which  impressions 
made  upon  the  organ  of  smell  remain  upon  it,  no  certain  knowledge  can  .be 
obtained.  It  is  difficult  to  say  that  the  effluvia  have  been  Completely  removed 
from  the  nasal  passages ;  since  it  is  not  improbable  that  the  odorous  particles 
(supposing  such  to  exist)  are  absorbed  or  dissolved  by  the  mucous  secretion  ; 
it  is  probably  in  this  manner  that  we  may  account  for  the  fact,  well  known  to 
every  medical  man,  that  the  cadaverous  odour  is  frequently  experienced  for 
days  after  a  post-mortem  examination.t 

*  The  author  has  been  assured  by  a  competent  witness,  that  a  lad  in  the  state  of  Som- 
nambulism, had  his  sense  of  .smell  so  remarkably  heightened,  as  to  be  able  to  assign  (with- 
out the  least  hesitation)  a  glove  placed  in  his  hand,  to  its  right  owner, — in  the  midst  of 
about  thirty  persons,  the  boy  himself  being  blindfolded. 

f  This  may  partly  be  attributed  also  to  the  effluvia  adhering  to  the  dress.  It  has  been 
remarked  that  dark  cloths  retain  these  more  strongly  than  light. 


SENSE  OF  VISION.  407 


5.   Sense  of  Vision. 

533.  The  objects  of  this  sense  are  bodies,  which  are  either  in  themselves 
luminous,  or  which  become  so  by  reflecting  the  light  that  proceeds  from  others. 
Whether  their  light  is  transmitted  by  the  actual  emission  of  rays,  or  by  the 
propagation  of  undulations  analogous  to  those  of  sound,  is  a  j^uestion  at  pre- 
sent keenly  debated  amongst  Natural  Philosophers ;  but  it  is  of  little  conse- 
quence to  the  Physiologist,  which  is  the  true  solution;  since  it  is  only  with 
the  laws,  which  actually  regulate  the  transmission  of  light,  that  he  is  concerned. 
These  laws  it  may  be  desirable  here  briefly  to  recapitulate. 

534.  Every  point  of  a  luminous  body  sends  off  a  number  of  rays,  which 
diverge  in  every  direction,  so  as  to  form  a  cone,  of  which  the  luminous  point 
is  the  apex.     So  long  as  these  rays  pass  through  a  medium  of  the  same  dens- 
ity, they  proceed  in  straight  .lines ;  but,  if  they  enter  a  medium  of  different 
density,  they  are  refracted  or  bent, — towards  the  perpendicular  to  the  surface 
at  the  point  at  which  they  enter,  if  they  pass  from  a  rarer  into  a  denser  me- 
dium, and  from  the  perpendicular,  when   they  pass  from   a  denser  medium 
into  a  rarer.     It  is  easily  shown  to  be  a  result -of  this  law,  that,  when  parallel 
rays  passing  through   air  fall  upon  a  convex  surface   of  glass,  they  will  be 
made  to  converge ;  so  as  to  meet  at  the  opposite  extremity  of  the  diameter  of 
the  circle,  of  which  the  curve  forms  part.     If,  instead  of  continuing  in  the 
glass,  they  pass  out  again,  through  a  second  convex  surface,  of  which  the  di- 
rection is  the  reverse  of  the  first,  they  will  be  made  to  converge  still  more,  so 
as  to  meet  in  the  centre  of  curvature.  Rays  which  are  not  parallel,  but  which 
are  diverging  from  a  focus,  are  likewise  made  to  converge  to  a  point  or  focus ; 
but  this  point  will  be  more  distant  from  the  lens,  in  proportion  as  the  object 
is  nearer  to  it,  and  the  angle  of  divergence  consequently  greater.     The  rays 
diverging  from  the  several  points  of  a  luminous  object,  are  thus  brought  to  a 
corresponding  focus ;  and  the  places  of  all  these  foci  hold  exactly  the  same  re- 
lation to  each  other,  with  that  of  the  points  from  which  the  rays  diverged;  so 
that  a  perfect  image  of  the  object  is  formed  upon  a  screen  held  in  the  focus 
of  the  lens.      This  image,  however,  will  be  inverted;  and  its  size,  in  pro- 
portion to  that  of  the  object,  will  depend  upon  their  respective  distances  from 
the  lens.     If  their  distances  be  the  same,  their  size  will  also  be  the  same  ;  if 
the  object  be  distant,  and  the  image  near,  the  latter  will  be  much  the  smaller ; 
and  vice  versa. 

535.  There  are  two  circumstances,  however,  which  interfere  with  the  per- 
fection of  an  image  thus  formed  by  a  convex  lens.     The  one  is,  that,  if  the 
lens  constitute  a  large  part  of  the   sphere  from  which  it  is  taken,  the  rays 
which  fall  near  its  margin  are  not  brought  to  a  focus  at  the  same  point  with 
those  which  pass  through  its  centre ;  but  at  a  point  nearer  the  lens.     This 
difference,  which  must  obviously  interfere  greatly  with  the  distinctness  of  the 
image,  is  termed  Spherical  Aberration ;  it  maybe  corrected  by  the  combi- 
nation of  two  or  more  lenses,  of  which  the  curvatures  are  calculated  to  ba- 
lance one  another,  in  such  a  manner  that  all  the  rays  shall  be  brought  to  the 
same  focus ;  or  by  diminishing  the  aperture  of  the  lens  by  means  of  a  stop 
or  diaphragm,  in  such  a  manner  that  only  the  central  part  of  it  shall  be  used. 
The  latter  of  these  methods  is  the  one  employed,  where  the  diminution  in 
the  amount  of  light  transmitted   is  not  attended  with   inconvenience.     The 
nearer  the  object  is  to  the  lens  (and  the  greater,  therefore,  the  angle  of  diverg- 
ence of  its  rays),  the  greater  will  be  the  spherical  aberration,  and  the  more 
must  the  aperture  of  the  diaphragm  be  contracted  in  order  to  counteract  it. 
The  other  circumstance  that  interferes  with  the  distinctness  of  the  image,  is 
the  unequal  refrangibility  of  the    differently-coloured  rays,  which   together 


408 


ON  SENSATION,  AND  THE  ORGANS  OF  THE  SENSES. 


make  up  white  or  colourless  light ;  the  violet  being  more  bent  from  their 
course  than  the  blue,  the  blue  more  than  the  yellow,  and  the  yellow  more 
than  the  red ;  the  consequence  of  which  will  be,  that  the  violet  rays  are 
brought  to  a  focus  much  nearer  to  the  lens  than  the  blue,  and  the  blue  nearer 
than  the  red.  If  a  screen  be  held  to  receive  the  image,  in  the  focus  of  any 
of  the  rays,  the  others  will  make  themselves  apparent  as  fringes  round  its 
margin.  This  difference  is  termed  Chromatic  Aberration.  It  is  corrected  in 
practice,  by  combining  together  lenses  of  different  substances,  of  which  the 
dispersive  power  (that  is,  the  power  of  separating  the  coloured  rays)  differs 
considerably.  This  is  the  case  with  flint  and  crown  glass,  for  instance, — the 
dispersive  power  of  the  former  being  much  greater  than  that  of  the  latter, 
whilst  its  refractive  power  is  nearly  the  same:  so  that,  if  a  convex  lens  of 
crown  glass  be  united  with  a  concave  of  flint  whose  curvature  is  much  less, 
the  dispersion  of  the  rays  effected  by  the  former  will  be  counteracted  by  the 
latter,  which  diminishes  in  part  only  its  refractive  power. 

536.  The  Eye  may  be  regarded  as  an  optical  instrument  of  great  perfec- 
tion, adapted  to  produce,  on  the  expanded  surface  of  the  optic  nerve,  a  com- 
plete image  or  picture  of  luminous  objects  brought  before  it;  in  which  the 
forms,  colours,  lights  and  shades,  &c.,  of  the  object  are  all  accurately  repre- 
sented. By  the  different  refractive  powers  of  the  transparent  media,  through 
which  the  rays  of  light  pass,  and  by  the  curvatures  given  to  their  respective 
surfaces,  both  the  Spherical  and  Chromatic  aberrations  are  corrected  in  a  de- 
gree sufficient  for  all  practical  purposes;  so  that,  in  a  well-formed  eye,  the 
picture  is  quite  free  from  haziness,  and  from  false  colours.  The  power  by 
which  it  adapts  itself  to  variations  in  the  distance  of  the  object, — so  as  to 
form  a  distinct  image  of  it,  whether  it  be  six  inches,  six  yards,  or  six  miles 
off, — is  extremely  remarkable,  and  cannot  be  regarded  as  hitherto  completely 
explained.  It  is  obvious  that,  if  we  fix  upon  any  distance  as  that  for  which 
the  eye  is  naturally  adjusted  (say  12  or  14  inches,  the  distance  at  which  we 

(Fig.  173. 


A  longitudinal  section  of  the  globe  of  the  Eye  ;  1,  the  sclerotic,  thicker  behind  than  in  front ;  2,  the 
cornea,  received  within  the  anterior  margin  of  the  sclerotic,  and  connected  with  it  by  means  of  a  be- 
veled edge ;  3,  the  choroid,  connected  anteriorly  with  (4)  the  ciliary  ligament,  and  (5)  the  ciliary  pro- 
cesses ;  6,  the  iris  ;  7,  the  pupil ;  8,  the  third  layer  of  the  eye,  the  retina,  terminating  anteriorly  by  an 
abrupt  border  at  the  commencement  of  the  ciliary  processes  ;  9,  the  canal  of  Petit,  which  encircles  the 
lens  (12) ;  the  thin  layer  in  front  of  this  canal  is  the  zonula  ciliaris,  a  prolongation  of  the  vascular  layer 
of  the  retina  to  the  lens.  10,  the  anterior  chamber  of  the  eye,  containing  the  aqueous  humour;  the 
lining  membrane  by  which  the  humour  is  secreted  is  represented  in  the  diagram  ;  11,  the  posterior;  12, 
the  lens  more  convex  behind  than  before,  and  enclosed  in  its  proper  capsule ;  13,  the  vitreous  humour 
enclosed  in  the  hyaloid  membrane,  and  in  cells  formed  in  its  interior  by  that  membrane  ;  14,  a  tubular 
sheath  of  the  hyaloid  membrane,  which  serves  for  the  passage  of  the  artery  of  the  capsule  of  the  lens  ; 
15,  the  neurilerama  of  the  optic  nerve  ;  16,  the  arteria  centralis  retinae,  imbedded  in  its  centre.] 


SENSE  OF  VISION. 
[Fig.  174. 


409 


A  Horizontal  Section  of  the  Eyeball  ;  1,  sclerotic  coat ;  2,  sheath  of  the  optic  nerve,  or  canal  of  Pon- 
tana;  3,  circular  venous  sinus  of  the  iris;  4,  proper  substance  of  the  cornea;  5,  arachnoidea oculi ;  6, 
membrane  of  the  anterior  chamber  of  the  aqueous  humour  ;  of  the  two  dotted  lines  one  points  to  the 

35 


410 


ON  SENSATION,  AND  THE  ORGANS  OF  THE  SENSES. 


supposed  membrane  of  Descemet,  the  other  to  the  supposed  continuation  of  that  membrane  over  the 
anterior  surface  of  the  iris;  7,  choroid  coat;  8,  annulus  albidus;  9,  ciliary  ligament ;  10, 10',  ciliary  body, 
consisting  of  (10')  a  pars  non-fimbriata,  and  (10)  a  pars  fimbriata  formed  by  the  ciliary  process;  11,  ora 
serrata  of  the  ciliary  body  ;  12,  iris  ;  13,  pupil ;  14,  membrane  of  the  pigment ;  15,  delicate  membrane  lining 
the  posterior  chamber  of  the  aqueous  humour ;  16,  membrane  of  Jacob  ;  17,  the  optic  nerve  surrounded 
by  its  neurilemma;  17',  the  fibres  of  the  optic  nerve  consisting  of  fasciculi  of  primitivet  ubules;  18,  cen- 
tral artery  of  the  retina;  19,  papilla  cornica  of  the  optic  nerve ;  20,  retina;  the  situation  of  its  vascular 
layer  is  indicated  by  a  dotted  line ;  21,  central  transparent  point  of  the  retina;  22,  vitreous  humour ;  23, 
the  hyaloid  membrane ;  24,  canalis  hyaloideus ;  25,  zonula  ciliaris;  in  the  plate,  none  of  its  fimbriated 
part  is  seen,  being  concealed  by  the  ciliary  processes;  26,  canal  of  Petit;  27,  crystalline  lens;  28,  an- 
terior wall  of  the  capsule  of  the  lens  ;  29,  posterior  wall  of  the  capsule  of  the  lens;  30,  posterior  chamber 
of  the  aqueous  humour ;  31,  anterior  chamber  of  the  aqueous  humour.] 

ordinarily  read),  the  rays  proceeding  from  an  object,  placed  nearer  to  the 
eye  than  this,  would  not  be  brought  to  a  focus  upon  the  retina,  but  would 
converge  towards  a  point  behind  it ;  whilst  on  the  contrary,  the  rays  from  an 
object  at  a  greater  distance  would  meet  before  they  reached  the  retina,  and 
would  have  again  diverged  from  each  other  when  they  impinge  upon  it ;  so 
that  in  either  case,  vision  would  be  indistinct.  Now  two  methods  of  adapta- 
tion suggest  themselves  to  the  Optician.  Either  he  may  vary  the  distance 
between  the  refracting  surface  and  the  screen  on  which  the  image  is  formed,, 
in  such  a  manner,  that  the  latter  shall  always  be  in  the  focus  of  the  converg- 
ing rays  ;  or,  the  distance  of  the  screen  remaining  the  same,  he  may  vary  the 
convexity  of  his  lens,  i«  such  a  manner  as  to  adapt  it  to  the  distance  of  the  object. 
It  is  not  improbable,  that  both  of  these  methods  are  employed  in  the  Eye, 
though  no  distinct  evidence  has  been  obtained  of  the  operation  of  either.  Seve- 
ral hypotheses  have  been  proposed,  to  account  for  the  phenomenon :  it  is* 
easily  proved  that  no  one  of  them  can  alone  be  true ;  but  it  cannot  be  readily 
shown  that  any  of  them  is  entirely  false :  and  it  would  not  seem  unlikely, 
therefore,  that  all  may  participate,  in  various  degrees,  in  the  effect.  The  fol- 
lowing are  the  principal  of  these. — 1.  An  alteration  in  the  form  of  the  globe 
of  the  eye  by  the  action  of  the  muscles,  so  that  its  antero-posterior  diameter 
may  be  increased  or  diminished.* — 2.  A  change  in  the  convexity  of  the  cor- 
nea. This  might  be  very  well  connected  with  the  last ;  since,  if  the  globe 
were  converted  into  a  spheroid,  of  which  the  antero-posterior  diameter  would 
be  the  longest,  the  curvature  of  the  cornea  would  be  increased  ;  whilst,  if  the 
antero-posterior  diameter  were  shortened,  the  curvature  would  be  diminished. 

3.  Change  of  position  of  the  crystalline  lens,  by  means  of  the  ciliary  processes. 

4.  Change  of  figure  of  the  lens  itself.     That  one  or  both  of  the  last  two  are 
concerned  in  the  effect,  would  appear  from  the  fact,  well  known  to  every  Oculist, 
that,  after  the  removal  of  a  cataract,  the  power  of  adapting  the  eye  to  dis- 
tances is  greatly  diminished. — 5.  Change  in  the  aperture  of  the  pupil ;  the 
mode  in  which  this  could  assist  in  accommodating  the  eye  to  variations  of 
distance,  is  not  very  obvious. 

537.  Some  curious  circumstances,  relative  to  the  connection  between  the 
optical  adaptation  of  the  eye  to  distances,  and  the  changes  in  the  direction  of  the 
axes  of  the  two  eyes,  have  been  pointed  out  by  Miiller.  When  both  eyes  are 
fixed  upon  an  object,  their  axes  must  converge  (as  formerly  explained,  §  455) 
so  as  to  meet  in  it.  The  nearer  the  object,  the  greater  must  be  the  degree  of 
convergence;  and  when  the  object  is  brought  within  the  ordinary  distance  of 
distinct  vision,  the  convergence  must  very  rapidly  increase.  Now  this  is 
precisely  what  takes  place,  in  regard  to  alterations  in  the  focus  of  the  eye ;  for 
little  change  is  required,  when  the  object  is  made  to  approach  from  a  considera- 
ble distance  to  a  moderate  distance;  but,  when  it  is  brought  near  the  eye,  the 

*  The  influence  of  the  muscles  in  altering  the  form  of  the  globe  may  be  better  compre- 
hended, now  that  we  know  the  mode  in  which  this  is  kept  in  its  place  in  the  front  of  the 
orbit,  by  a  fascia  passing  behind  it,  and  attached  anteriorly  to  the  lids. 


SENSE  OF  VISIOX.  411 

focus  must  be  considerably  lengthened,  or  the  convexity  of  the  eye  increased, 
to  cause  the  rays  to  meet  on  the  retina:  and  hence  it  may  be  surmised,  that 
the  same  cause  is  acting  to  produce  both  changes.  But  that  the  convergence 
of  the  axes  is  not  itself  in  any  way  the  occasion  of  the  alteration  of  the  focus 
of  the  eye,  is  shown  by  the  fact,  that  the  adaptation  is  as  perfect,  in  a  person 
who  only  possesses  or  uses  one  eye,  as  it  is  when  both  are  employed ;  and 
also  by  the  power,  which  is  possessed  by  some  persons,  of  altering  the  focus 
of  the  eye  by  an  effort  of  the  will,  whilst  the  convergence  remains  the  same. 
In  regard  to  the  adaptation  of  the  eyes  to  varying  distances,  it  is  further  to  be 
remarked,  that,  when  an  object  is  being  viewed  as  near  to  the  eye  as  it  can  be 
distinctly  seen,  the  pupil  contracts  in  a  considerable  degree.  The  final  cause 
of  this  change,  is  evidently  to  exclude  the  outer  rays  of  the  cone  or  pencil, 
which,  from  the  large  angle  of  their  divergence,  would  fall  so  obliquely  on  the 
convex  surface  of  the  eye,  as  to  be  much  affected  by  the  spherical  aberration ; 
and  to  allow  the  central  rays  only  to  enter  the  eye,  so  as  to  preserve  the  clear- 
ness of  the  image.  The  channel  through  which  it  is  effected  is  evidently  the 
same,  as  that  by  which  the  convergence  of  the  eyes  is  produced, — namely, 
the  inferior  branch  of  the  third  pair  of  nerves;  to  the  action  of  which,  the 
sensations  upon  the  retina  form  the  stimulus,  in  the  same  manner  as  they  do 
to  the  ordinary  variation  in  the  diameter  of  the  pupil  under  the  influence  of 
light. 

538.  The  ordinary  forms  of  defective  vision,  which  are  known  under  the 
names  of  myopia  and  presbyopia,  or  short-sightedness  and  long-sightedness, 
are  entirely  attributable  to  defects  in  the  optical  adaptation  of  the  eye.  In  the 
former,  its  refractive  power  is  too  great;  the  rays  from  objects  at  the  usual 
distance  are  consequently  brought  too  soon  to  a  focus,  so  as  to  cross  one 
another  and  diverge,  before  they  fall  upon  the  retina;  whilst  the  eye  is  adapted 
to  bring  to  their  proper  focus  on  the  retina,  only  those  rays  which  were  pre- 
viously diverging  at  a  large  angle,  from  an  object  in  its  near  proximity.  Hence 
a  short-sighted  person,  whose  shortest  limit  of  distinct  vision  is  not  above  half 
that  of  a  person  of  ordinary  sight,  can  see  minute  objects  more  clearly;  his 
eyes  having,  in  fact,  the  same  magnifying  power,  which  those  of  the  other 
would  possess,  if  aided  by  a  convex  glass,  that  would  enable  him  to  see  the 
object  distinctly  at  the  shorter  distance.  But  as  the  myopic  structure  of  the 
eye  incapacitates  its  possessor  from  seeing  objects  clearly,  at  even  a  moderate 
distance,  it  is  desirable  to  apply  a  correction;  and  this  is  done,  by  simply  inter- 
posing a  concave  lens,  of  which  the  curvature  is  properly  adapted  to  compen- 
sate for  the  excess  of  that  of  the  organ  itself,  between  the  object  and  the  eye. 
On  the  other  hand,  in  the  presbyopic  eye,  the  curvature  and  refractive  power 
are  not  sufficient  to  bring  to  a  focus  on  the  retina,  rays  which  were  previously 
divergent  in  a  considerable  or  even  in  a  moderate  degree ;  and  indistinct  vision 
in  regard  to  all  near  objects  is,  therefore,  a  necessary  consequence,  whilst 
distant  objects  are  well  seen.  This  defect  is  remedied  by  the  use  of  convex 
lenses,  which  make  up  for  the  deficiency  of  the  curvature.  We  commonly 
meet  with  myopia  in  young  persons,  and  with  presbyopia  in  old;  but  this  is 
by  no  means  the  invariable  rule;  for  even  aged  persons  are  sometimes  short- 
sighted; and  long-sightedness  is  occasionally  met  with  amongst  the  young. 
In  choosing  spectacles,  for  the  purpose  of  correcting  the  errors  of  the  eye,  it 
is  of  great  consequence  not  to  make  an  over-compensation;  for  this  has  a 
tendency  to  increase  the  defect,  besides  occasioning  great  fatigue  in  the  employ- 
ment of  the  sight.  It  may  be  easily  found,  when  a  glass  of  the  right  power 
has  been  selected,  by  inquiring  of  the  individual,  whether  it  alters  the  apparent 
size  of  the  objects,  or  only  renders  them  distinct.  If  it  alter  the  size  (in- 
creasing  it  if  it  be  a  convex  lens,  and  diminishing  it  if  it  be  a  concave),  its 
curvature  is  too  great ;  whilst  if  it  do  not  disperse  the  haze,  it  is  not  sufficiently 


412 


ON  SENSATION,  AND  THE  ORGANS  OF  THE  SENSES. 


powerful.  In  general  it  is  better  to  employ  a  glass  which  somewhat  under- 
compensates  the  eye,  than  one  which  is  of  a  curvature  at  all  too  high  ;  since, 
with  the  advance  of  years  in  elderly  persons,  a  progressive  increase  in  power 
is  required ;  and,  as  young  persons  grow  up  to  adult  age,  they  should  endeavour 
to  dispense  with  the  aid  of  spectacles. 

539.  Many  other  interesting  inquiries,  respecting  the  action  of  the  eye  as 
an  optical  instrument,  suggest  themselves  to  the  physical  philosopher;  but  the 
foregoing  are  the  chief  in  which  the  Physiologist  is  concerned ;  and  we  shall 
now  proceed,  therefore,  to  consider  the  share,  which  the  Retina  and  Optic 

Fig.  175.  Fig.  176. 


Part  of  the  Retina  of  a  Frog,  seen 
from  the  outer  surface.  Magnified  300 
times. 


Distribution  of  Capillaries  in  Vascu- 
lar layer  of  Retina. 


[Fig.  177. 


Nerve  perform  in  the  phenomena  of  vision. — The  optic  nerve,  at  its  entrance 
into  the  eye,  divides  itself  into  numerous  small  fasciculi  of  ultimate  fibrils; 

and  these  appear  to  spread  themselves  out, 
and  to  inosculate  with  each  other  by  an  ex- 
change of  fibrils,  so  as  to  form  a  net-like 
plexus.  There  is  considerable  difficulty, 
however,  in  the  precise  determination  of  the 
course  of  the  nerve-fibres  in  the  Retina;  on 
account  of  their  minute  size,  and  the  absence 
of  their  distinctive  characters.  According  to 
Mr.  Bowman,  the  tubular  membrane  and  the 
white  substance  of  Schwann  are  deficient; 
and  only  the  central  part  of  the  nerve-fibre,  or 
axis-cylinder,  is  continued  into  this  expansion. 
The  plexus  of  nerve-fibres  comes  into  relation 
with  a  plexus  of  capillary  vessels,  very  minute- 
ly distributed ;  and  also  with  a  layer  of  cells, 
so  closely  resembling  those  of  the  cortical  sub- 
stance of  the  brain,  that  there  can  be  no  rea- 
sonable doubt  of  their  correspondence  in  func- 
tion. This  layer  of  cells,  constitutes  the  in- 
ternal layer  of  the  true  retina.  We  have  here, 
then,  all  "the'  elements  of  an  apparatus  for  the 
origination  of  changes  in  the  nervous  trunks, 
in  a  fully  displayed  form  ;  and  it  can  scarcely 
be  doubted  that  the  essential  parts  of  the  same 
structures  exist  in  the  papillae  of  the  cutaneous 
and  other  sensory  surfaces. — The  true  Retina 
is  covered  externally  by  a  very  peculiar  in- 
vestment, the  Membrane  of  Jacob,  which 


A  portion  of  the  Retina  of  an  Infant, 
with  its  vessels  injected  and  magnified 
25  diameters.  An  outline  of  the  natural 
size  of  this  piece  is  seen  just  below  the 
main  cut.] 


SENSE  OF  VISION. 


413 


separates  it  from  the  pigmentary  layer.     This  seems  to  be  composed  of  cells 
having  a  cylindrical  form.     These   are  sometimes  arranged  vertically  to  the 

[Fig.  178. 


Vertical  section  of  the  Human  Retina  and  Hyaloid  Membrane,  h.  Hyaloid  membrane,  h'.  Nuclei 
on  its  inner  surface,  c.  Layer  of  transparent  cells,  connecting  the  hyaloid  and  retina,  c'.  Separate 
cell  enlarged  by  imbibition  of  water,  n.  Gray  nervous  layer,  with  its  capillaries.  1.  Its  fibrous  lamina. 
2.  Its  vesicular  lamina.  1'.  Shred  of  fibrous  lamina  detached.  2'.  Vesicle  and  nucleus  detached,  g.  Granu- 
lar layer.  3.  Light  lamina  frequently  seen.  g'.  Detached  nucleated  particle  of  the  granular  layer. 
m.  Jacob's  membrane,  m'.  Appearance  of  its  particles,  when  detached,  m".  Its  outer  surface.  Mag- 
nified 320  diameters.] 


[Fig.  179. 


surface  of  the  membrane,  so  that  their  extremities  only  are  seen ;  whilst  in 
other  instances  they  are  found  to  present  an 
imbricated  arrangement,  lying  over  each  other 
obliquely,  in  which  case  they  are  of  conside- 
rable length  (Fig.  175).  They  are  remarka- 
ble for  the  rapidity  with  which  they  undergo 
alterations  after  death  ;  and  especially  for  the 
changes  in  their  form,  which  are  produced 
by  the  action  of  water. 

540.  The  following  statements  on  the 
Limits  of  Human  Vision,  in  regard  to  the 
possible  minuteness  of  the  objects  of  which 
it  can  take  cognizance,  comprehend  the  re- 
sult of  numerous  inquiries  made  by  Ehren- 
berg,  with  the  view  of  calculating  the  ulti- 
mate power  of  the  Microscope.*  In  opposi- 
tion to  the  generally-received  opinion,  Ehren- 
berg  arrived  at  the  conclusion  that,  in  regard 
to  the  extreme  limits  of  vision,  there  is  little  difference  amongst  persons  of 
ordinarily  good  sight,  whatever  may  be  the  focal  distance  of  their  eyes.  The 
smallest  square  magnitude  usually  visible  to  the  naked  eye,  either  of  white 
particles  on  a  black  ground,  or  of  black  upon  a  white  or  light-coloured  ground, 
is  about  the  l-405th  of  an  inch.  It  is  possible,  by  the  greatest  condensation 
of  light,  and  excitement  of  the  attention,  to  recognize  magnitudes  between  the 
1 -405th  and  l-540th  of  an  inch  ;  but  without  sharpness  or  certainty.  Bodies 
which  are  smaller  than  these,  cannot  be  discerned  with  the  naked  eye  when 
single ;  but  may  be  seen  when  placed  in  a  row.  Particles  which  powerfully 
reflect  light,  however,  may  be  distinctly  seen,  when  not  half  the  size  of  the 


Outer  surface  of  the  Retina,  showing 
the  membrane  of  Jacob,  partially  detach- 
ed. After  Jacob.] 


Taylor's  Scientific  Memoirs. 
35* 


Vol.  i.  p.  576. 


414 


ON  SENSATION,  AND  THE  ORGANS  OF  THE  SENSES. 


least  of  the  foregoing ;  thus,  gold  dust*  of  the  fineness  of  1-1 125th  of  an  inch, 
may  be  discerned  with  the  naked  eye  in  common  daylight.  The  delicacy  of 
vision  is  far  greater  for  lines  than  for  single  articles  ;  opaque  threads  of  1 -4900th 
of  an  inch  in  diameter  may  be  discerned  with  the  naked  eye,  when  held  to- 
wards the  light.  Such  threads  are  about  half  the  diameter  of  the  Silk-worm's 
fibre.  The  degree  in  which  the  attention  is  directed  to  them,  has  a  great 
influence  on  the  readiness  with  which  very  minute  objects  can  be  perceived; 
and  Ehrenberg  remarks  that  there  is  a  much  greater  difference  amongst  indi- 
viduals in  this  respect,  than  there  is  in  regard  to  the  absolute  limits  of  vision. 
Many  persons  can  distinctly  see  such  objects,  when  their  situation  is  exactly 
pointed  out  to  them,  who  cannot  otherwise  distinguish  them ;  and  the  same 
is  the  case  with  persons  of  acuter  perception,  with  respect  to  objects  at  dis- 
tances greater  than  those,  at  which  they  can  see  most  clearly.  "  I  myself," 
says  Ehrenberg,  "  cannot  see  l-2700th  of  an  inch,  black  on  white,  at  twelve 
inches  distance ;  but  having  found  it  at  from  four  to  five  inches  distance,  I 
can  remove  it  to  twelve  inches,  and  still  see  the  object  plainly."  Similar 
phenomena  are  well  known  in  regard  to  a  balloon,  or  a  faint  star,  in  a  clear 
sky;  or  a  ship  in  the  horizon:  we  easily  see  them  after  they  have  been 
pointed  out  to  us;  but  the  faculty  of  rapidly  descrying  depends  on  the  habit 
of  using  the  eyes  in  search  of  such  objects  (§  519). 

541.  The  sense  of  Vision  depends,  in  the  first  place,  on  the  transference 
to  our  minds  of  the  picture  which  is  formed  upon  the  retina ;  this  picture  puts 
us  in  possession  of  the  outlines,  lights  and  shades,  colours,  and  relative  posi- 
tions of  the  objects  before  us  ;  and  all  the  ideas  respecting  the  real  forms, 
distances,  &c.,  of  bodies,  which  we  found  upon  these  data,  must  be  considered 
in  the  light  of  perceptions,  either  instinctive  or  acquired.  Many  of  these  are 
derived  through  the  combination,  in  our  minds,  of  the  Visual  sensations,  with 
those  derived  from  the  sense  of  Touch.  Thus,  to  take  a  most  simple  illustra- 
tion, the  idea  of  smoothness  is  one  essentially  tactile  ;  and  yet  it  constantly 
occurs  to  us,  on  looking  at  a  surface  which  reflects  light  in  a  particular  man- 
ner. But,  if  it  were  not  for  the  association,  which  experience  leads  us  to 
form,  of  the  connection  between  polish  as  seen  by  the  eye,  and  smoothness 
as  felt  by  the  touch,  we  should  not  be  able  to  determine,  as  we  now  can  do, 
the  existence  of  both  these  qualities  from  an  impression  communicated  to  us 
through  either  sense  singly.  The  general  fact  that,  in  Man,  the  greater  part 
of  those  notions  of  the  external  world  by  which  his  actions  in  the  adult  state 
are  guided,  are  acquired  by  the  gradual  association  of  the  sensations  commu- 
nicated by  the  sight  and  by  touch,  is  substantiated  by  amply-sufficient  evidence. 
This  evidence  is  chiefly  derived  from  observations  made  upon  persons  born 
blind,  to  whom  sight  has  been  communicated  by  an  operation,  at  a  period  of  life 
which  enabled  them  to  give  an  accurate  description  of  their  sensations.  The 
case  recorded  by  Cheselden  is  one  of  the  most  interesting  of  these.  The 
youth  (about  12  years  of  age),  for  some  time  after  tolerably  distinct  vision  had 
been  obtained,  saw  everythingjtfotf,  as  in  a  picture ;  simply  receiving  the  con- 
sciousness of  the  impression  made  upon  his  retina ;  and  it  was  some  time  be- 
fore he  acquired  the  power  of  judging,  by  his  sight,  of  the  real  forms  and 
distances  of  the  objects  around  him.  An  amusing  anecdote  recorded  of  him, 
shows  the  complete  want  of  natural  or  intuitive  connection  which  there  is  in 
Man,  between  the  ideas  formed  through  visual  and  through  tactile  sensations. 
He  was  well  acquainted  with  a  Dog  and  a  Cat  by  feeling  ;  but  could  not  re- 
member their  respective  characters  when  he  saw  them.  One  day,  when  thus 
puzzled,  he  took  up  the  Gat  in  his  arms,  and  felt  her  attentively,  so  as  to  as- 

*  Ehrenbsrg  mentions  that  he  obtained  the  finest  particles  of  gold,  by  scraping  gilt  brass  ; 
by  filing  pure  gold,  he  always  obtained  much  coarser  particles. 


SENSE  OF  VISION. 


415 


sociate  the  two  sets  of  ideas ;  and  then,  setting  her  down,  said,  "  So,  puss,  I 
shall  know  you  another  time."  A  similar  instance  has  come  under  the  Au- 
thor's own  knowledge  ;  but  the  subject  of  it  was  scarcely  old  enough  to  pre- 
sent phenomena  so  striking.  One  curious  circumstance  was  remarked  of  him, 
which  fully  confirms  (if  confirmation  were  wanting)  the  view  here  given. 
For  some  time  after  the  sight  was  tolerably  clear,  the  lad  preferred  finding  his 
way  through  his  father's  house,  to  which  he  had  been  quite  accustomed  when 
blind,  by  touch  rather  than  by  sight, — the  use  of  the  latter  sense  appearing  to 
perplex  rather  than  to  assist  him  ;  but,  when  learning  a  new  locality,  he  em- 
ployed his  sight,  and  evidently  perceived  the  increase  of  facility  which  he  de- 
rived from  it. 

542.  The  question  has  been  proposed,  whether  a  person  born  blind,  who 
was  able  by  the  sense  of  Touch  to  distinguish  a  cube  from  a  sphere,  would, 
on  suddenly  obtaining  his  Sight,  be   able  to   distinguish  them  by  the  latter 
sense.     This  question  was  answered  by  Locke  in  the  negative;  and  probably 
with  justice.     It  is  no  real  objection  to  such  a  reply,  that  a  new-born  animal 
seeks  the  nipple  of  its  mother,  when  informed  of  its  proximity  by  sight ;  for 
all  that  is  indicated  by  this  fact  is,  that  the  sensation  excites  an  intuitive  feel- 
ing of  desire,  which  gives  rise  to  movements  adapted  to  gratify  it.     Such  in- 
stinctive actions,  founded  upon  intuitive  perceptions,  are,  as  already  pointed 
out,  much  more  numerous  in  the  lower  Animals  than  in  the  higher,  and  in  the 
young  of  the  Human  species  than  in  the  adult  (§  428) ;  and  they  do  not  afford 
any  proof  that  definite  notions,  such  as  we  acquire,  of  the  forms  and  proper- 
ties of  external   objects,  are   possessed  by  the   animals  which  exhibit  them. 
We  shall  now  examine,  a  little  more  in  detail,  into  the  means  by  which  we 
gain  such  notions,  and  the  data  on  which  they  are  founded. 

543.  The  first  point  to  be  determined,  is  one  which  has  been  a  fruitful 
source  of  discussion, — the  cause  of  erect  vision,  the  picture  Upon  the  retina 
being  inverted.    Many  solutions  of  it  have  been  attempted;  but  they  are  for  the 
most  part  rather  specious  than  really  satisfactory.  That  which  has  been  of  late 
years  the  most  in  vogue,  is  founded  upon  what  was  styled  the  Law  of  Visible 
Direction,  which  has  been  supported  by  Sir  D.  Brewster,  and  other  eminent 
Philosophers.     This  law  affirms,  that  every  object  is  seen  in  the  direction  of 
the  perpendicular  to  that  point  of  the  retina,  on  which  its  image  is  formed ; 
or,  in  other  words*  that,  as  all  the  perpendiculars  to  the  several  points  of  the 
inner  surface  of  a  sphere  meet  in  the  centre,  the  line  of  direction  of  any  ob- 
ject is  identical  with  the  prolonged  radius  of  the  sphere,  drawn  from  the  point 
at  which  its  image  is  made  upon  the  retina.     Upon  close  examination,  how- 
ever, it  is  found  that  this  law  cannot  be  optically  correct ;  since  the  lines  of 
direction  cross  each  other  at  a  point  much  anterior  to  the  centre  of  the  globe ; 
as  may  be  determined  by  drawing  a   diagram  upon  a  large  scale,  and  laying 
down  the  course  of  the  rays  received  by  the  eye,  according  to  the  curvatures 
and  refractive  powers  of  its  different  parts.     In  this  manner  it  has  been  deter- 
mined by  Volkraann,  that  the  lines  of  direction  cross  each  other  in  a  point  a 
little  behind  the  crystalline  lens  ;  and  that  they  will  thus  fall  at  such  differ- 
ent angles  on  different  points  of  the  retina,  that  no  general  law  can  be  laid 
down  respecting  them.     It  may  be  questioned,  moreover,  whether  such  a  law 
would  afford  any  assistance  in  explaining  the  phenomenon  ;  since,  after  all, 
it  is  requisite  to  assume  an  intuitive  application  of  it,  in  supposing  the  mind 
to  derive  its  ideas  of  the  relative  situations  of  objects,  from  the  imagined  line 
of  direction. — A  much  simpler  and  more  direct  explanation  may  be  given. 
We  must  remember  that,  which  we  have  had  occasion  to  notice  in  regard  to  all 
the  other  senses, — the  broad  line  of  distinction  between  the  sensation  and  the 
perception  or  elementary  notion;  and  this  is  still  more  clearly  shown  by  the 
complete  absence  of  any  relation,  but  such  as  experience  developes,  between 


416 


ON  SENSATION,  AND  THE  ORGANS  OF  THE  SENSES. 


the  perceptions  derived  through  the  sight,  and  those  acquired  from  the  touch. 
Hence  there  is  no  more  difficulty  in  understanding,  that  an  inverted  picture 
upon  the  retina  should  convey  to  us  a  notion  of  the  external  world,  which 
harmonizes  with  that  acquired  through  the  sense  of  touch,  than  there  is  in 
comprehending  the  formation  of  any  of  those  intuitive  perceptions  of  animals, 
which  are  so  much  more  removed  from  the  teachings  of  our  own  experience 
(§  490).  It  is  justly  remarked  by  Miiller  that,  "  if  we  do  see  objects  inverted  [or 
rather,  if  the  picture  on  the  retina  is  inverted]  the  only  proof  we  can  possibly 
have  of  it,  is  that  afforded  by  the  study  of  the  laws  of  Optics  ;  and,  if  everything 
is  seen  reversed,  the  relative  position  of  the  objects  remains  unchanged.  Hence 
it  is,  also,  that  no  discordance  arises  between  the  sensations  of  inverted  vision 
and  those  of  touch,  which  perceives  everything  in  its  erect  position  ;  for  the 
images  of  all  objects,  even  of  our  own  limbs,  on  the  retina,  are  equally  in- 
verted, and  therefore  maintain  the  same  relative  position*  Even  the  image  of 
our  hand,  wJien  used  in  touch,  is  inverted."  From  what  has  been  stated,  it 
would  appear  quite  conceivable,  that  a  person  just  endowed  with  sight,  should 
not  at  first  know  by  his  visual  powers,  whether  a  pyramid  placed  before  his 
eyes  is  the  same  body,  and  in  the  same  position,  as  one  with  which  he  has 
become  acquainted  by  the  touch ;  and,  if  this  be  admitted,  the  inference  ne- 
cessarily follows,  that  the  notion  of  erectness,  which  we  form  by  the  combined 
use  of  our  eyes  and  our  hands,  is  really  the  product  of  experience  in  ourselves, 
whilst  it  is  probably  innate  or  intuitional  in  the  lower  Animals. 

544.  The  cause  of  single  vision  with  the  two  eyes  has,  in  like  manner, 
been  the  subject  of  much  discussion;  since  the  mode  in  which  we  are  affected 
by  the  two  simultaneous  impressions,  is  quite  different  from  that,  in  which 
we  derive  our  knowledge  of  external  things  through  the  other  senses.  Some 
have  even  asserted,  that  we  do  not  really  employ  both  eyes  simultaneously, 
but  that  the  mind  is  affected  by  the  image  communicated  by  one  only;  and 
this  idea  might  seem  to  be  confirmed  by  the  fact  heretofore  mentioned  (§  519), 
respecting  the  alternate  use  of  the  two  eyes,  when  they  are  looking  through 
two  differently-coloured  media.  But  it  is  easily  disproved  in  other  ways. — 
It  will  presently  be  shown,  that  all  our  estimates  of  the  forms  of  bodies,  de- 
pend on  the  combination  by  the  mind,  of  the  images  simultaneously  transmit- 
ted by  the  two  eyes  ;  and  our  knowledge  of  distances  is  in  great  part  obtained 
in  like  manner.  The  condition  of  Single  Vision  has  been  already  stated 
(§  454)  to  be  probably  this,' — that  the  two  images  of  the  object  should  be 
formed  on  parts  of  the  two  retinae,  which  are  accustomed  to  act  in  concert ; 
and  reasons  were  given  for  the  belief,  that  habit  is  the  chief  means  by  which 
this  conformity  is  produced.  There  can  be  no  doubt,  however,  that  double 
images  are  continually  being  conveyed  to  our  minds ;  but  that,  from  their 
want  of  force  and  distinctness,  and  from  the  attention  being  fixed  on  something 
else,  we  do  not  take  cognizance  of  them.  This  may  be  shown  by  a  very 
simple  experiment.  If  two  fingers  be  held  up  before  the  eyes,  one  in  front 
of  the  other,  and  vision  be  directed  to  the  more  distant,  so  that  it  is  seen 
singly,  the  nearer  will  appear  double  ;  while,  if  the  nearer  one  be  regarded 
more  particularly,  so  as  to  appear  single,  the  more  distant  will  be  seen  double. 
A  little  consideration  will  show,  therefore,  that  our  minds  must  be  continually 
affected  with  sensations,  which  cannot  be  united  into  the  idea  of  a  single 
image  ;  since,  whenever  we  direct  the  axes  of  our  eyes  towards  any  object, 
everything  else  will  be  represented  to  us  as  double;  but  we  do  not  ordinarily 
perceive  this,  from  our  minds  being  fixed  upon  a  clear  and  distinct  image,  and 
disregarding,  therefore,  the  vague  undefined  images  formed  by  objects  at  a 
different  focus.  Of  this  it  is  very  easy  to  convince  oneself.  It  is  moreover 
evident  from  this  experiment,  that  double  vision  cannot  result  from  want  of 
symmetry  in  the  position  of  the  images  upon  the  retina,  to  which  some  have 


SENSE  OF  VISION.  417 

attributed  it ;  for  it  answers  equally  well,  if  the  line  of  the  two  fingers  be  pre- 
cisly  in  front  of  the  nose,  so  that  the  inclination  of  both  eyes  towards  either 
object  is  equal ;  the  position  of  the  images  of  the  second  object  must  then  be 
at  the  same  distance  on  each  side  from  the  central  line  of  the  retina,  and  yet 
they  are  represented  to  the  mind  as  double.  It  is,  moreover,  easily  shown, 
that,  in  the  lower  animals  whose  orbits  are  not  directed  forwards  as  in  us,  but 
sideways  in  a  greater  or  less  degree,  whenever  an  object  is  so  situated  as  to 
be  seen  by  both  eyes,  the  points  of  the  two  retinae  on  which  its  images  are 
formed,  must  be  very  far  from  possessing  this  symmetry. 

545.  Many  attempts  have  been  made  to  explain  the  phenomena  of  Single 
Vision  by  the  peculiar  decussation  of  the  Optic  nerves  (§  445) ;  and  an  inte- 
resting correspondence  between  the  varieties  in  the  degree  of  decussation,  and 
the  position  of  the  eyes,  in  several  animals,  has  been  pointed  out  by  Mr.  Solly 
and  Mr.  Mayo.     From  these  and  other  data,  it  has  been  concluded,  that  each 
nerve  is  used  in  looking  towards  the  opposite  side.    This  is  evidently  true  of 
the  Osseous  Fishes,  whose  two  eyes,  being  directed  sideways,  have  two  en- 
tirely different  spheres  of  vision.     And  it  is  also  true  of  Man,  if  Mr.  Mayo's 
account  of  the  distribution  of  the  nerve  be  correct ;  since,  when  we  look  at 
an  object  held  directly  in  front  of  the  face,  at  the  level  of  the  eyes,  and  at  the 
nearest  point  for  distinct  vision,  almost  the  whole  of  that  portion  of  the  right 
retina,  which  lies  to  the  outside  of  the  entrance  of  the  optic  nerve,  is  directed 
to  the  left;  and  the  exactly  different,  complementary,  or  inner  portion  of  the 
left  retina,  which  is  supplied  by  the  same  nerve,  is  likewise  directed  to  the 
left.     On  this  supposition,  all  the  rays  entering  the   two  eyes  from  any  one 
point,  will  be  brought  to  a  focus  on  fibrils  belonging  to  the  nerve  of  the  same 
side ;  though  these  are  in  Man,  as  in  other  animals  whose  spheres  of  vision 
are  nearly  or  partly  coincident,  distributed  to  distinct  visual  organs.*     It  is 
obvious,  however,  that  this  or  any  similar  explanation,  must  be  insufficient  to 
explain  the  phenomenon  of  single  vision ;  since  the  images  formed  upon  the 
two  retinas  are  necessarily  different,  and  must  be  combined  or  harmonized  by 
an  act  of  the  mind,  as  will  be  shown  in  the  succeeding  paragraphs. 

546.  We  shall  next  consider  the  mode,  in  which  our  notion  of  the  solid 
forms  and  relative  projection  of  objects  is  acquired  ;  on  which  great  light  has 

recently  been  thrown  by  the  interesting  experiments  of  Mr.  Wheatstone.t  It 
is  perfectly  evident,  both  from  reason  and  experience,  that  the  flat  picture  upon 
the  retina,  which  is  the  only  object  of  our  sensation,  could  not  itself  convey  to 
our  minds  any  notion,  but  that  of  a  corresponding  plane  surface.  In  fact,  any 
notion  of  solidity,  which  might  be  formed  by  a  person,  who  had  never  had 
the  use  of  more  than  one  eye,  would  entirely  depend  upon  the  combination  of 
his  visual  and  tactile  sensations.  This  idea  is  fully  confirmed  by  the  case 
already  referred  to,  as  recorded  by  Cheselden.  The  first  visual  idea  formed 
by  the  youth  was,  that  the  objects  around  him  formed  a  flat  surface,  which 
touched  his  eyes,  as  they  had  previously  been  in  contact  with  his  hands  ;  and 
after  this  notion  had  been  corrected,  through  the  education  of  his  sight  by  his 
touch,  he  fell  into  the  converse  error  of  supposing  that  a  picture,  which  was 
shown  to  him,  was  the  object  itself  represented  in  relief  on  a  small  scale. — But 
where  both  eyes  are  employed,  it  has  been  ascertained  by  Mr.  Wheatstone, 

*  The  late  Dr.  Wollaston  was  subject  to  a  curious  affection  of  vision,  which  consisted  in 
his  not  being  able  to  see  more  than  half  an  object, — the  loss  being  sometimes  on  one  side, 
and  sometimes  on  the  other.  The  Author  has  met  with  several  cases  of  this  disorder,  which 
has  been  termed  hemiopia.  Dr.  W.  thought  that  they  might  be  explained  by  the  decussation 
of  the  optic  nerve ;  but  Mr.  Mayo  states  that  he  has  known  instances  of  a  parallel  affection, 
involving  alternately  the  centre  and  the  circumference  of  the  retina,  and  therefore  not  attribut- 
able to  any  such  structural  arrangement. 

f  Philosophical  Transactions,  1838. 


418  ON  SENSATION,  AND  THE  ORGANS  OF  THE  SENSES. 

that  they  concur  in  exciting  the  perception  of  solidity  or  projection,  which 
arises  from  the  combination  of  two  different  images  in  the  mind.  It  is  easily 
shown,  that  any  near  object  is  seen  in  two  different  modes  by  the  two  eyes. 
Thus  let  the  reader  hold  up  a  thin  book,  in  such  a  manner  that  its  back  shall 
be  exactly  in  front  of  his  nose,  and  at  a  moderate  distance  from  it ;  he  will 
observe,  by  closing  first  one  eye  and  then  the  other,  that  his  perspective  view 
of  it  (or  the  manner  in  which  he  would  represent  it  on  a  plane  surface)  is  very 
different,  according  to  the  eye  with  which  he  sees  it.  With  the  right  eye  he 
will  see  its  right  side,  very  much  foreshortened ;  with  the  left,  he  will  gain  a 
corresponding  view  of  the  left  side ;  and  the  apparent  angles,  and  the  lengths 
of  the  different  lines,  will  be  found  to  be  very  different  in  the  two  views.  On 
looking  at  either  of  these  views  singly,  no  other  notion  of  solidity  can  be 
acquired  from  it,  than  that  to  which  the  mind  is  conducted,  by  the  association 
of  such  a  view  with  the  touch  of  the  object  it  represents.  But  it  is  capable  of 
proof,  that  the  mental  association  of  the  two  different  pictures  upon  the  retina*, 
does  of  itself  give  rise  to  the  idea  of  solidity.  This  proof  is  afforded  by  Mr. 
Wheatstone's  ingenious  instrument,  the  Stereoscope. 

547.  The  Stereoscope  essentially  consists  of  two  plane  mirrors,  inclined 
with  their  backs  to  one  another  at  an  angle  of  90°.  If  two  perspective  draw- 
ings of  any  solid  object,  as  seen  at  a  given  distance  with  the  two  eyes  respect- 
ively, be  placed  before  these  mirrors,  in  such  a  manner  that  their  images  shall 
be  made  to  fall  upon  the  corresponding  parts  of  the  two  retinas,  in  the  same 
manner  as  the  two  images  formed  by  the  solid  object  itself  would  have  done, 
the  mind  will  perceive,  not  a  single  representation  of  the  object,  nor  a  confused 
union  of  the  two,  but  a  body  projecting  in  relief, — the  exact  counterpart  of 
that  from  which  the  drawings  were  made.  Mr.  Wheatstone  further  shows  by 
means  of  the  Stereoscope,  that  similar  images,  differing  to  a  certain  extent  in 
magnitude,  when  presented  to  the  corresponding  parts  of  the  two  retina,  give 
rise  to  the  perception  of  a  single  object,  intermediate  in  size  between  the  two 
monocular  pictures.  Were  it  not  for  this,  objects  would  appear  single,  only 
when  at  an  equal  distance  from  both  eyes,  so  that  their  pictures  upon  the 
retina  are  of  the  same  size ;  which  will  only  happen,  when  they  are  directly 
in  front  of  the  median  line  of  the  face.  Again,  if  pictures  of  dissimilar  objects 
be  simultaneously  presented  to  the  two  eyes,  the  consequence  will  be  similar 
to  that  which  is  experienced,  when  the  rays  come  to  the  eye  through  two 
differently-coloured  media; — the  two  images  do  not  coalesce,  nor  do  they 
appear  permanently  superposed  upon  one  another :  but  at  one  time  one  image 
predominates  to  the  exclusion  of  the  other,  and  then  the  other  is  seen  alone  ; 
and  it  is  only  at  the  moment  of  change,  that  the  two  seem  to  be  intermingled. 
It  does  not  appear  to  be  in  the  power  of  the  will,  Mr.  Wheatstone  remarks, 
to  determine  the  appearance  of  either ;  but,  if  one  picture  be  more  illuminated 
than  the  other,  it  will  be  seen  during  a  larger  proportion  of  the  time.  Many 
other  curious  experiments  with  this  simple  instrument  are  related  by  Mr. 
Wheatstone  ;  and  they  all  go  to  confirm  the  general  conclusion,  that  the  com- 
bination of  the  images  furnished  by  the  two  eyes  is  a  mental  act,  resulting 
from  an  inherent  law  of  our  psychical  constitution  ;  and  that  our  perceptions  of 
the  solidity  and  projection  of  objects,  near  enough  to  be  seen  in  different  views 
with  the  two  eyes,  result  from  this  cause.  In  regard  to  distant  objects,  how- 
ever, the  difference  in  the  images  formed  by  the  two  eyes  is  so  slight,  that  it 
cannot  aid  in  the  determination ;  and  hence  it  is,  that,  whilst  we  have  no  dif- 
ficulty in  distinguishing  a  picture,  however  well  painted,  from  a  solid  object, 
when  placed  near  our  eyes,  (since  the  idea,  which  might  be  suggested  by  the 
image  formed  on  one  eye,  will  then  be  corrected  by  the  other,)  we  are  very 
liable  to  be  misled  by  a  delineation,  in  which  the  perspective,  light  and  shade, 
<fcc.,  are  faithfully  depicted,  if  we  are  placed  at  a  distance  from  it,  and  are  pre- 


SENSE  OF  VISIOX.  419 

vented  from  perceiving  that  it  is  but  a  picture.  In  this  case,  however,  a  slight 
movement  of  the  head  is  sufficient  to  undeceive  us ;  since  by  this  movement 
a  great  change  would  be  occasioned  in  the  perspective  view  of  the  object,  sup- 
posing it  to  possess  an  uneven  surface ;  whilst  it  scarcely  affects  the  image 
formed  by  a  pictiire.  In  the  same  manner,  a  person  who  only  possesses  one  eye, 
obtains,  by  a  slight  motion  of  his  head,  the  same  idea  of  the  form  of  a  body, 
which  another  would  acquire  by  the  simultaneous  use  of  his  two  eyes. 

548.  The  appreciation  of  the  distance  of  objects,  may  be  easily  shown  to 
be  principally  derived  from  the  association,  in  the  mind,  of  visual  and  tactual 
sensations  ;  assisted,  in  regard  to  near  objects,  by  the  muscular  sensations  de- 
rived from  the  convergence  of  the  eyes.     Thus,  an  infant,  or  a  person  who 
has  but  recently  acquired  sight,  evidently  forms  very  imperfect  ideas  regarding 
the  distance  of  objects  ;  and  it  is  only  after  long  experience  that  a  correct  no- 
tion is  formed.     The  assistance  which  is  given  by  the  joint  use  of  both  eyes, 
is  evident  from  the  fact,  that,  if  we  close  one  eye,  we  are  unable  to  execute 
with  certainty  many  actions,  which  require  a  precise  appreciation  of  the  dis- 
tance of  near  objects, — such  as  threading  a  needle,  or  snuffing  a  candle.     In. 
regard  to  distant  objects,  our  judgment  is  chiefly  founded  upon  their  apparent 
size,  if  their  actual  size  be  known  to  us ;  but,  if  this  is  not  the  case,  and  if  we 
are  so  situated  that  we  cannot  judge  of  the  intervening  space,  we  principally 
form  our  estimate  from  the  greater  or  less  distinctness  of  their  colour  and  out- 
line.    Hence  this  estimate  is  liable  to  be  greatly  affected  by  varying  states  of 
the  atmosphere ;  as  is  well  known  to  every  one  who  has  visited  warmer  lati- 
tudes.   The  extreme  clearness  of  the  air  sometimes  brings,  into  an  apparently 
near  proximity,  a  hill  that  rises  beyond  some  neighbouring  ridge  (the  inter- 
vening space  being  hidden,  so  as  not  to  afford  any  datum  for  the  estimate  of 
the  distance  of  the  remote  hill) ;  and  which,  by  a  slight  haziness,  is  carried  to 
three  or  four  times  the  degree  of  apparent  remoteness.     It  is  probable  that,  in 
the  lower  Animals,  the  perception  of  distance  is  much  more  intuitive  than  it  is 
in  ourselves. 

549.  Our  estimate  of  the  real  size  of  an  object  is  manifestly  connected  with 
that  of  its  distance.     The  apparent  size  is  dependent  upon  the  angle  at  which 
its  rays  diverge,  to  impinge  upon  the  cornea ;  this  angle  increases  with  the 
proximity,  and  diminishes  with  the  remoteness,  of  the  object.     Our  estimate 
of  the  comparative  size  of  near  objects,  of  whose  distances  we  can  become 
aware  by  the  inclination  of  the  optic  axes,  is  much  more  correct  than  that 
which  we  form,  when  one  or  both  are  far  removed;  since,  when  we  are  un- 
certain as  to  its  distance,  we  cannot  form  a  judgment  of  the  real  size  of  a  body, 
from  the  angle  at  which  its  rays  diverge.     Hence  our  estimate  of  the  size  of 
objects  even  moderately  distant,  is  much  influenced  by  states  of  the  atmosphere. 
Thus,  if  we  walk  across  a  common  in  a  fog,  a  child  approaching  us  appears 
to  have  the  size  of  a  man,  and  a  man  seems  like  a  giant;  since  the  indistinct- 
ness of  the  outline  excites  in  the  mind  the  idea  of  distance;  and  an  object 
seen  under  a  given  visual  angle  at  a  distance,  must  of  necessity  be  much  larger 
than  one,  of  which  the  apparent  size  is  the  same,  but  which  is  much  nearer. 
The  want  of  innate  power  in  Man  to  form  a  true  conception  of  either  size  or 
distance,  is  well  shown  by  the  effect  produced  on  the  mind  unprepared  for 
such  delusions,  by  a  skilfully-painted  picture ;  the  view  of  which  is  so  con- 
trived, that  its  distance  from  the  eye  cannot  be  estimated  in  the  ordinary  man- 
ner; the  objects  it  represents  are  invested  by  the  mind  with  their  real  sizes 
and  respective  distances,  as  if  their  peal  image  was  formed  upon  the  retina.* 

*  This  delusion  has  been  extremely  complete,  in  some  of  those  who  have  seen  the  pano- 
ramic view  of  London  in  the  Coliseum.  A  lively  and  interesting  account  of  it  is  given  in 
the  Journal  of  the  Parsee  Shipbuilders,  who  visited  England  some  time  ago. 


420  ON  SENSATION,  AND  THE  ORGANS  OF  THE  SENSES. 

550.  From  all  these  considerations,  we  are  led  to  perceive  the  truth  of  the 
quaint  observation  made  by  Dr.  Brown, — that  "vision  is,  in  fact,  the  art  of 
seeing  things  which  are  invisible ;"  that  is,  of  acquiring  information,  by  means 
of  the  eye,  which  is  neither  contained  in  the  sensations  of  sight  themselves, 
nor  logically  deducible  from  the  intimations  which  those  sensations  really 
convey.     We  cannot  too  constantly  bear  in  mind,  in  treating  of  this  subject, 
that  we  do  not  take  cognizance  by  our  optic  nerves,  as  we  do  by  the  nerves 
of  touch,  of  material  bodies  themselves,  but  of  the  pictures  or  images  formed 
by  those  objects ;  and  whatever  be  the  notions  suggested  by  the  picture,  that 
can  never  be  transformed  into  anything  else.     These  notions  appear  to  be,  in 
the  lower  Animals,  entirely  of  an  intuitional  or  instinctive  character;  in  Man 
they  are  so  in  a  much  less  degree ;  and  although  it  is  impossible  to  come  to  a 
precise  conclusion  on  the  subject,  from  the  want  of  sufficient  data,  it  is  indu- 
bitable that  a  large  part  of  the  knowledge  of  the  external  world,  which  he  de- 
rives in  the  adult  condition  from  the  use  of  his  eyes  alone,  is  really  dependent 
upon  the  early  education  of  his  perceptive  powers,  in  which  process,  the  sen- 
sations conveyed  by  .different  organs  are  brought  to  bear  upon  one  another. 

551.  The  persistence,  during  a  certain  interval,  of  impressions  made  upon 
the  retina,  gives  rise  to  a  number  of  curious  visual  phenomena.     The  pro- 
longation of  the  impression  will  be  governed,  in  part,  by  its  previous  duration. 
Thus,  when  we  rapidly  move  an  ignited  point  through  a  circle,  the  impression 
itself  is  momentary,  and  remains  but  for  a  short  time;  whilst,  if  we  have  been 
for  some  time  looking  at  a  window,  and  then  close  our  eyes,  the  impression  of 
the  dark  bars  traversing  the  illuminated  space  is  preserved  for  several  seconds. 
Such  phenomena  can  here  be  only  briefly  adverted  to.     One  of  these  is  the 
combination,  into  one  image,  of  two  or  more  objects  presented  to  the  eye  in 
successive  movements ;  but  these  must  be  of  a  kind  which  can  be  united,  other- 
wise a  confused  picture  is  produced.    Thus  in  a  little  toy,  called  the  Thauma- 
trope,  which  was  introduced  some  years  ago,  the  two  objects  were  painted  on 
the  opposite  sides  of  a  card, — a  bird,  for  instance,  on  one,  and  a  cage  on  the 
other;  and,  when  the  card  was  made  (by  twisting  a  pair  of  strings)  to  revolve 
about  one  of  its  diameters,  in  such  a  manner  as  to  be  alternately  presenting 
the  two  sides  to  the  eye  at  minute  intervals,  the  two  pictures  were  blended, 
the  bird  being  seen  in  the  cage.     A  far  more  curious  illusion,  however,  was 
that  first  brought  into  notice  by  Mr.  Faraday ;  who  showed  that,  if  two  toothed 
wheels,  placed  one  behind  the  other,  be  made  to  revolve  with  equal  velocity, 
a  stationary  spectrum  will  be  seen;  whilst  if  one  be  made  to  revolve  more 
rapidly  than  the  other,  or  the  number  of  teeth  be  different,  the  spectrum  also 
will  revolve.     The  same  takes  place  when  a  single  wheel  is  made  to  revolve 
before  a  mirror ;  the  wheel  and  its  image  answering  the  purpose  of  the  two 
wheels  in  the  former  case.     On  this  principle,  a  number  of  very  ingenious 
toys  have  been  constructed;  in  some  of  these,  the  same  figure  or  object  is 
seen  in  a  variety  of  positions ;  and  the  impressions  of  these,  passing  rapidly 
before  the  eye,  give  rise  by  their  combination  to  the  idea,  that  the  object  is 
itself  moving  through  these  positions.     Similar  illusions  may  be  produced  in 
regard  to  colour. 

552.  When  the  Retina  has  been  exposed  for  some  time  to  a  strong  im- 
pression of  some  particular  kind,  it  seems  less  susceptible  of  feebler  impres- 
sions of  the  same  kind.     Thus,  if  we  look  at  any  brightly  luminous  object, 
and  then  turn  our  eyes  on  a  sheet  of  white  paper,  we  shall  perceive  a  dark 
spot  upon  it;  the  portion  of  the  retina,  which  had  been  affected  by  the  bright 
image,  not  being  able  to  receive  an  impression  from  the  fainter  rays  reflected 
by  the  paper.     The  dark  spectrum  does  not  at  once  disappear,  but  assumes 
different  colours  in  succession, — these  being  expressions  of  the  states  through 
which  the  retina  passes,  in  its  transition  to  the  natural  condition.     If  the  eye 


SENSE  OF  VISION.  421 

has  received  a  strong  impression  from  a  coloured  object,  the  spectrum  exhibits 
the  complementary  colour;*  thus,  if  the  eye  be  fixed  for  any  length  of  time 
upon  a  bright  red  spot  on  a  white  ground,  and  be  then  suddenly  turned  so  as 
to  rest  upon  the  white  surface,  we  see  a  spectrum  of  a  green  colour. — The 
same  explanation  applies  to  the  curious  phenomenon  of  coloured  shadows. 
It  may  not  unfrequently  be  observed  at  sunset,  that,  when  the  light  of  the  sun 
acquires  a  bright  orange  colour  from  the  clouds  through  which  it  passes,  the 
shadows  cast  by  it  have  a  blue  tint.  Again,  in  a  room  with  red  curtains,  the 
light  which  passes  through  these  produces  green  shadows.  In  both  instances, 
a  strong  impression  of  one  colour  is  made  on  the  general  surface  of  the  retina; 
and  at  any  particular  spots,  therefore,  at  which  the  light  is  colourless  but  very 
faint,  that  colour  is  not  perceived,  its  complement  only  being  visible.  The 
correctness  of  this  explanation  is  proved  by  the  fact,  that,  if  the  shadow  be 
viewed  through  a  tube,  in  such  a  manner  that  the  coloured  ground  is  excluded, 
it  seems  like  an  ordinary  shadow.  It  is  not  unlikely  that,  as  Miiller  suggests, 
the  predominant  action  of  one  colour  on  the  retina  disturbs  (as  it  were)  the 
equilibrium  of  'its  condition,  and  excites  in  it  a  tendency  to  the  development 
of  a  state,  corresponding  to  that  which  is  produced  by  the  impression  of  the 
complementary  colour;  for  the  latter  is,  according  to  him,  perceived  even 
^vhere  it  does  not  exist; — as  when  the  eye,  after  receiving  a  strong  impression 
from  a  coloured  spot,  and  directed  upon  a  completely  dark  surface  or  into  a 
dark  cavity,  still  perceives  the  spectrum. — Upon  these  properties  of  the  eye 
are  founded  the  laws  of  harmonious  colouring,  which  have  an  obvious  analogy 
with  those  of  musical  harmony.  All  complementary  colours  have  an  agreeable 
effect,  when  judiciously  disposed  in  combination;  and  all  bright  colours,  which 
are  not  complementary,  have  a  disagreeable  effect,  if  they  are  predominant:  this 
is  especially  the  case  in  regard  to  the  simple  colours,  strong  combinations  of 
any  two  of  which,  without  any  colour  that  is  complementary  to  either  of  them, 
are  extremely  offensive.  Painters  who  are  ignorant  of  these  laws,  introduce 
a  large  quantity  of  dull  grey  into  their  pictures,  in  order  to  diminish  the  glaring 
effects,  which  they  would  otherwise  produce;  but  this  benefit  is  obtained  by 
a  sacrifice  of  the  vividness  and  force,  which  may  be  secured  in  combination 
with  the  richest  harmony,  by  a  proper  attention  to  physiological  principles. 

553.  Some  persons,  who  can  perfectly  distinguish   forms,  are   deficient, 
through  some  original  peculiarity  in  the  constitution   of  the  retina,  in  the 
power  of  discriminating  colours.    This  is  most  commonly  seen  in  regard  to  the 
complementary  colours,  especially  red  and  green ;  such  persons  not  being 
able  to  perceive  cherries  amidst  the  leaves  on  a  tree,  except  by  the  difference 
of  their  form.     Several  distinct  varieties  of  this  affection  may  be  distinguished, 
however.     These  have  been  classified  by  Seebeck  and  Wartmann.t 

554.  Amongst  other  curious  phenomena  of  Vision,  is  the  vanishing  of 
images  which  fall  at  the  entrance  of  the  optic  nerve  ;  as  is  shown  in  the  fol- 
lowing experiment.     Let  two  black  spots  be  made  upon  a  piece  of  paper, 
about  four  or  five  inches  apart ;  then  let  the  left  eye  be  closed,  and  the  right 
eye  be  strongly  fixed  upon  the  left-hand  spot.     If  the  paper  be  then  moved 
backwards  and  forwards,  so  as  to  change  its  distance  from  the  eye,  a  point  will 
be  found,  at  which  the  right-hand  spot  is  no  longer  visible;  though  it  is  clearly 
seen,  when  the  paper  is  brought  nearer  or  removed  further.     In  this  position 
of  the  eye  and  object,  the  rays  from  the  right-hand  spot  cross  to  the  nasal 

*  By  the  complementary  colour  is  meant  that,  which  would  be  required  to  make  white  or 
colourless  light,  when  mixed  with  the  original.  As  red,  blue,  and  yellow  are  the  primary 
or  elementary  colours,  red  is  the  complement  of  green  (which  is  composed  of  yellow  and 
blue);  blue  is  the  complement  of  orange  (red  and  yellow);  and  yellow  of  purple  (red  and  blue); 
and  vice  versa  in  all  instances. 

t  Miiller's  Physiology,  p.  1213;  Taylor's  Scientific  Memoirs,  Vol.  iv.  p.  156,  et  seq. 
3G 


422  ON  SENSATION,  AND  THE  ORGANS  OF  THE  SENSES. 

side  of  the  globe,  and  fall  upon  the  point  of  the  retina,  which  has  just  been 
mentioned.  The  phenomenon  is  not  confined  to  that  spot,  however ;  nor  is 
it  correct  to  say,  as  is  sometimes  done,  that  the  retina  is  not  sensible  to  light 
at  that  point ;  since,  if  such  were  the  case,  we  should  see  a  dark  spot  in  our 
field  of  view,  whenever  we  use  only  one  eye.  The  fact  is,  that  a  similar 
phenomenon  may  occur  under  somewhat  different  conditions,  in  any  division 
of  the  retina,  especially  in  its  lateral  parts.  Thus,  if  we  fix  the  eye  for  some 
time,  until  it  is  fatigued,  upon  a  strip  of  coloured  paper  lying  upon  a  white 
surface,  the  image  of  the  coloured  object  will  in  a  short  time  disappear,  and 
the  white  surface  will  be  seen  in  its  place  ;  the  disappearance  of  the  image, 
however,  is  only  of  a  few  seconds  duration.  The  truth  seems  to  be,  that 
there  is  a  tendency  in  the  retina,  to  the  propagation  over  neighbouring  parts, 
of  impressions  which  occupy  a  large  proportion  of  its  surface ;  and  that  this 
tendency  is  the  strongest,  around  the  point  at  which  the  optic  nerve  enters, 
so  that  the  state  of  this  part  will  generally  become  similar  to  that  of  the  sur- 
rounding portion  of  the  retina.  Hence,  when  we  are  using  one  eye  only, 
we  do  not  perceive  any  dark  spot  in  the  field,  but  only  a  certain  degree  of  in- 
distinctness in  a  portion  of  the  image. 

555.  Under  particular  circumstances,  we  may  receive  a  visual  representa- 
tion of  the  retina  itself;  as  is  shown  by  the  experiments  of  Purkinje.     "  If^ 
in  a  room  otherwise  dark,  a  lighted  candle  be  moved  to  and  fro,  or  in  a  circle, 
at  a  distance  of  six  inches  before  the  eyes,  we  perceive,  after  a  short  time,  a 
dark  arborescent  figure  ramifying  over,  the  whole  field  of  vision ;  this  appear- 
ance is  produced  by  the  vasa  centralia  distributed  over  the  retina,  or  by  the 
parts  of  the  retina  covered  by  those  vessels.     There  are,  properly  speaking, 
two  arborescent  figures,  the  trunks  of  which  are  not  coincident,  but  on  the 
contrary  arise  in  the  right  and  left  divisions  of  the  field,  and  immediately 
take  opposite  directions.     One  trunk  belongs  to  each  eye,  but  their  branches 
intersect  each  other  in  the  common  field  of  vision.     The  explanation  of  this 
phenomenon  is  as  follows  : — By  the  movement  of  the  candle  to  and  fro,  the 
light  is  made  to  act, on  the  whole  extent  of  the  retina,  and  all  the  parts  of  the 
membrane  which  are  not  immediately  covered  by  the  vasa  centralia  are  feebly 
illuminated  ;  those  parts,  on  the  contrary,  which  are  covered  with  those  vessels 
cannot  be  acted  on  by  the  light,  and  are  perceived,  therefore,  as  dark  arbore- 
scent figures.    These  figures  appear  to  lie  before  the  eye,  and  to  be  suspended 
in  the  field  of  vision."*     We  have  thus   another  demonstration  of  the  fact 
that,  in  ordinary  vision,  the  immediate  object  of  our  sensation  is  a  certain 
condition  of  the  retina,  which  is  excited  by  the  formation  of  a  luminous 
image. 

6.  Sense  of  Hearing. 

556.  In  the  Ear,  as  in  the  Eye,  the  impressions  made  upon  the  sensory 
nerve  are  not  at  once  produced  by  the  body  which  originates  the  sensation ; 
but  they  are  propagated  to  it,  through  a  medium  capable  of  transmitting  them. 
Here  too,  therefore,  we  take  cognizance  by  the  mind,  not  of  the  sonorous  ob- 
ject, but  of  the  condition  of  the  auditory  nerve ;  and  all  the  ideas  we  form  of 
sounds,  as  to  their  nature,  intensity,  direction,  &c.,  must  be  based  upon  the 
changes  which  they  produce  in  it.     The  complex  contrivances,  which  we 
meet  with  in  the  organ  of  Hearing  among  higher  animals,  are  evidently  in- 
tended to  give  them  greater  power  of  discriminating  sounds,  than  is  possessed 
by  the  lower  tribes  ;  in  which  last  it  is  reduced  to  a  form  so  simple,  that  it  may 
be  questioned  whether  they  can  be  said  to  possess  an  organ  of  hearing,  if 
by  this  term  we  imply  anything  more  than  the  mere  consciousness  of  sono- 

*  Muller's  Physiology,  p.  1163. 


SENSE  OF  HEARING.  423 

rous  vibrations.  There  is  a  considerable  difference,  however,  between  the 
Eye  and  the  Ear,  in  regard  to  the  special  purposes  for  which  they  are  respect- 
ively adapted.  In  the  former  we  have  seen,  that  the  whole  object  of  the  in- 
strument is  to  direct  the  rays  of  light  received  by  it,  in  such  a  manner,  as  to 
occasion  them  to  fall  upon  the  expansion  of  the  optic  nerve  in  a  similar  rela- 
tive position,  and  with  corresponding  proportional  intensity,  to  that  which 
they  possessed  when  issuing  from  the  object.  We  have  no  reason  to  believe 
anything  of  this  kind  to  be  the  purpose  of  the  Ear ;  indeed,  it  would  be  in- 
consistent with  the  laws  of  the  propagation  of  sound.  Sonorous  vibrations 
having  the  most  various  directions,  and  the  most  equal  rate  of  succession,  are 
transmitted  by  all  media  without  modification,  however  numerous  their  lines 
of  intersection ;  and  wherever  these  undulations  fall  upon  the  auditory  nerve, 
they  must  cause  the  sensation  of  corresponding  sounds.  Still  it  is  probable 
that  some  portions  of  the  complex  organ  of  hearing,  in  Man  and  in  the  higher 
animals,  are  more  adapted  than  others  to  receive  impressions  of  a  particular 
character  ;  and  that  thus  we  may  be  especially  informed  of  the  direction  of  "a 
sound  by  one  part  of  the  organ,  of  its  musical  tone  by  another,  and  of  some 
other  of  its  qualities  by  a  third.  In  our  inquiries  into  this  ill-understood  sub- 
ject, we  shall  commence  with  a  brief  survey  of  the  comparative  structure  of 
the  organ. 

557.  The  essential  part  of  an  Organ  of  Hearing  being  obviously  a  nerve, 
endowed  with  the  peculiar  property  of  receiving  and  transmitting  sonorous 
undulations,  it  is  by  no  means  indispensable  that  a  special  provision  should 
be  made  for  this  purpose ;  since  the  Auditory  nerve,  if  merely  in  contact  with 
the  solid  parts  of  the  head,  will  be  affected  by  the  vibrations,  in  which  it  is 
continually  participating.  Hence  we  must  not  imagine  the  sense  to  be  absent, 
wherever  we  cannot  discover  a  special  organ.  It  is  among  the  highest  only 
of  the  Invertebrate  animals,  that  any  such  special  organ  presents  itself;  and 
then  only  in  a  very  simple  form.  Thus  in  the  Crustacea  and  Cephalopoda, 

[Fig.  180. 


General  view  of  the  external,  middle,  and  internal  ear,  as  seen  in  a  prepared  section  through  a,  the 
auditory  canal,  b.  The  tympanum  or  middle  ear.  c.  Eustachian  tube,  leading  to  the  pharynx,  d.  Coch- 
lea; and  e.  Semicircular  canals  and  vestibule,  seen  on  their  exterior,  as  brought  into  view  by  dissecting 
away  the  surrounding  petrous  bone.  The  styloid  process  projects  below;  and  the  inner  surface  .of  the 
carotid  canal  is  seen  above  the  Eustachian  tube.  From  Scarpa.] 


424 


ON  SENSATION,  AND  THE  ORGANS  OF  THE  SENSES. 


the  ear  consists  of  a  small  cavity  excavated  in  the  solid  frame-work  of  the 
head ;  this  cavity  is  lined  with  a  membrane,  on  which  the  nerve  is  distri- 
buted ;  and  it  is  filled  with  a  watery  fluid.  In  some  instances,  the  cavity  is 
completely  shut  in  by  its  solid  walls  ;  and  the  sonorous  vibrations  can  then 
only  be  communicated  through  these  :  but  in  the  higher  forms  of  this  appa- 
ratus, there  is  a  small  aperture  covered  with  a  membrane,  upon  which  the 
external  medium  can  at  once  act.  In  tracing  this  most  simple  into  the  more 
complex  forms,  it  is  at  once  seen,  that  the  cavity  corresponds  with  the  vesti- 
bule of  the  ear  of  higher  animals,  and  its  opening  with  the  fenestra  ovalis. 
In  the  lowest  Cyclostome  Fishes,  the  organ  is  but  little  more  complicated  ; 
from  the  vestibule  proceeds  a  single  annular  passage,  which  may  be  consi- 
dered as  a  semicircular  canal;  and  the  auditory  nerve  is  distributed  minutely 
upon  its  lining  membrane,  as  upon  that  of  the  vestibule  itself.  In  species 
a  little  higher  in  the  scale,  two  such  canals  exist ;  these  are  present  in  the 
Lamprey.  And  in  all  the  rest  of  the  class,  three  semicircular  canals  are 
found;  holding  the  same  direction  in  regard  to  each  other,  as  they  do  in  Man. 
Within  the  vestibular  sac  of  Fishes  are  found  calcareous  concretions,  which 
are  pulverulent  in  the  Cartilaginous, but  hard  and  stony  in  the  Osseous  tribes; 
to  these  the  name  of  Otolithes  has  been  given.  Some  rudiments  of  a  tympa- 
nic cavity  may  be  found  in  Fishes ;  but  there  is  no  vestige  of  a  cochlea :  in 
several  tribes,  the  organ  of  hearing  possesses  a  peculiar  connection  with  the 
air-bladder,  which  appears  to  be  a  foreshadowing  of  the  Eustachian  tube  of 
higher  classes. 

558.  In  the  true  Reptiles,  a  considerable  advance  is  constantly  to  be  found 
in  the  character  of  the  Ear;  a  tympanic  cavity  being  added,  with  a  drum  and 
a  chain  of  bones  ;  and  a  rudiment  of  the  cochlea  being  generally  discoverable. 
Among  the  Amphibia,  however,  which  are  in  so  many  respects  intermediate 

[Fig.  181. 


Diagram  of  the  inner  wall  of  the  tympanun  after  maceration,  the  outer  wall  and  ossicles  being  re- 
moved, a.  Fenestra  ovalis.  b.  Fenestra  rotunda,  c.  Promontory,  d.  Pryramid,  with  the  orifice  at  its 
apex,  e.  Projection  of  the  aqueductus  Fallopii.  f.  Some  of  the  mastoid  <:ells  communicating  with  the 
tympanum,  g.  Processus  cochleariformis,  bounding  i,  the  canal  for  the  tensor  tympani  muscle  :  the  an- 
terior pyramid  is  broken  off,  if  it  existed,  h.  Commencement  of  the  Eustachian  tube.  j.  Jugular-fossa, 
immediately  below  the  tympanum.  &,  k.  Carotid  canal,  with  the  artery  in  outline,  to  show  its  course  in 
relation  to  the  tympanum  and  Eustachian  tube.  I  Portio  dura  of  the  seventh  pair  of  nerves,  as  it  would 
be  seen  in  the  terminal  part  of  the  aqueduct  of  Fallopius.  m.  Chorda  tympani,  leaving  the  portio  dura, 
and  entering  a  short  canal,  which  opens  in  the  tympanum,  at  the  base  of  the  pyramid,  n.  Grooves  for 
the  tympanic  plexus.] 


SENSE  OF  HEARING. 


425 


between  the  true  Reptiles  and  Fishes,  there  is  a  remarkable  variation  in  this 
respect, — some  having  a  tympanum,  and  some  being  completely  destitute  of 
it.  Wherever  a  tympanic  cavity  distinctly  exists,  there  is  an  Eustachian  tube 
connecting  it  with  the  fauces.  This  cavity,  in  the  true  Reptiles,  not  only 
possesses  ihefenestra  ovalis  (or  opening  into  the  vestibule),  but  the  fenestra 
rotunda  (or  opening  into  the  cochlea).  The  membrana  tympani  is  usually 

[Fig.  182. 


A  view  of  the  axis  of  the  Cochlea  and  the  Lamina  Spiralis,  showing  the  arrangement  of  the  three 
Zones;  theosseous  zone  and  the  membraneof  the  vestibule  have  been  removed;  1,  the  natural  size  of  the 
parts ;  the  other  figure  is  greatly  magnified ;  2,  trunk  of  the  auditory  nerve ;  3,  the  distribution  of  its  fila- 
ments in  the  zona  ossea ;  4,  the  nervous  anastomosis  of  the  zona  vesicularis ;  5,  the  zona  membranacea; 
0,  the  osseous  tissue  of  the  modiolus ;  7,  the  opening  between  the  two  scalse.] 

visible  externally ;  but  it  is  sometimes  covered  by  the  skin. — In  Birds,  the 
structure  of  the  ear  is  essentially  the  same  as  in  the  higher  Reptiles.  A  dis- 
tinct cochlea  exists,  though  its  form  is  not  spiral  but  nearly  straight :  of  its 
character,  however,  there  can  be  no  doubt ;  a  division  into  two  passages,  by 
a  membranous  partition  on  which  the  nerve  is  spread  out,  being  evident. 
Moreover  the  tympanum  communicates  with  cavities  in  the  cranial  bones, 
which  are  thus  filled  with  air ;  and  these,  by  increasing  the  extent  of  surface, 
produce  a  more  powerful  resonance.  There  is  no  external  ear,  except  in  a 
few  species  of  nocturnal  Birds. — In  Mammalia,  the  organ  of  hearing  is  usually 

[Fig.  183. 


Cochlea  of  a  pew -born  infant,  opened  tm  the  side  towards  the  apex  of  the  petrous  bone.  It  shows  the 
general  arrangement  of  the  two  scalse,  the  lamina  spiralis,  and  the  distribution  of  the  cochlear  nerve.  At 
the  apex  is  seen  the  modiolus  expanding  into  the  cupola,  where  the  spiral  canal  terminates  in  a  cul-de- 
sac.  The  helicotrema  is  not  visible  in  this  view.  From  Arnold.] 

36* 


426 


ON  SENSATION,  AND  THE  ORGANS  OF  THE  SENSES. 


formed  upon  the  same  plan,  as  it  presents  in  Man ;  in  the  Monotremata,  how- 
ever, it  more  approaches  that  of  Birds.  The  cochlea  of  the  Mammalia  in 
general  is  a  spiral,  forming  about  two  turns  and  a  half;  the  partition  which 

[Fig.  184. 


The  Cochlea  divided  parallel  with  its  axis,  through  the  centre  of  the  Modiolus ;  after  Breschet;  1,  the 
modiolus ;  2,  the  infundibulum  in  which  the  modiolus  terminates  ;  3,  3,  the  cochlear  nerve,  sending  its  fila- 
ments through  the  centre  of  the  modiolus ;  4,  4,  the  scala  tympani  of  the  first  turn  of  the  cochlea ;  5,  5,  the 
scala  vestibula  of  the  first  turn;  6,  section  of  the  lamina  spiralis,  its  zonulaossea;  one  of  the  filaments  of 
the  cochlear  nerve  is  seen  passing  between  the  two  layers  of  the  lamina  spiralis  to  be  distributed  upon  the 
membrane  which  invests  the  lamina;  7,  the  membranous  portion  of  the  lamina  spiralis;  8,  loops  formed  by 
the  filaments  of  the  cochlear  nerve ;  9, 9,  scala  tympani  of  the  second  turn  of  the  cochlea;  10, 10,  scala 
vestibula  of  the  second  turn ;  the  septum  between  the  two  is  the  lamina  spiralis;  11,  the  scala  tympani  of 
the  remaining  half  turn  ;  12,  the  remaining  half  turn  of  the  scala  vestibula;  the  dome  placed  over  this  half 
turn  is  the  cupola :  13,  the  lamina  of  bone  which  forms  the  floor  of  the  scala  vestibula  curving  spirally 
round  to  constitute  the  infundibulum  (2) ;  14,  the  helicotrema  through  which  a  bristle  is  passed ;  its  lower 
extremity  issues  from  the  scala  tympani  of  the  middle  turn  of  the  cochlea.] 

divides  its  canal  is  partly  osseous,  partly  membranous ;  and  its  two  passages 
communicate  with  the  tympanic  cavity  and  the  vestibule  respectively.  The 
cavity  of  .the  tympanum  is  very  large  in  some  species,  extending  even  into  the 
contiguous  bones.  All  the  Mammalia,  except  the  aquatic  tribes,  have  an  ex- 
ternal ear ;  and  this  is  sometimes  of  an  enormous  size  in  proportion  to  the 
dimensions  of  the  body,  as  it  is  in  the  Bats.  The  labyrinth  of  the  higher 
Vertebrata  contains  no  otolithes. 

559.  The  ultimate  terminations  of  the  fibres  of  the  Auditory  nerve,  are 


Fig.  185. 


[Fig.  186. 


Papillae  (?)  of  the  Auditory  nerve, 
on  a  segment  of  the  spiral  lamina  of 
the  cochlea  of  a  young  Mouse ;  the 
lower  portion  is  the  osseous,  and  the 
higher  the  membranous  part  of  the 
lamina.  Magnified  300  times. 


The  Auditory  Nerve  taken  out  of  the  Cochlea ;  1,  1,  1, 
the  trunk  of  the  nerve;  2, 2,  its  filaments  in  the  zona  ossea 
of  the  lamina  spiralis ;  3,  3.  its  anastomoses  in  the  zona 
vesicularis.] 


SENSE  OF  HEARING. 


427 


best  seen  in  the  lamina  spiralis  of  the  cochlea,  and  its  membranous  prolon- 
gation.    Much  diversity  exists,  however,  as  to   the  interpretation  of  the   ap- 


[Fig.  187. 


[Fig.  188. 


A  highly  magnified  view  of  a  small  piece  of  the  Lamina  Spiralis, 
showing  the  globular  structure  of  the  Nerves,  and  the  manner  in 
which  they  leave  their  Neurilemma  as  they  anastomose;  the  natural 
size  of  the  piece  is  seen  on  the  side  of  the  figure;  1,  portion  of  the 
auditory  nerve,  2,  2,  osseous  canals  in  the  zona  ossea  of  the  lamina 
spiralis;  3,  3,  anastomoses  in  the  zona  mollis;  4,  4,  the  neurilemma 
leaving  the  nervous  loops  and  interlocking  to  form  the  layer  of  the 
zona  membranacea.] 


Plexiform  arrangement  of  the 
cochlear  nerves  seen  in  the  basal 
coil  of  the  lamina  spiralis,  treated 
with  hydrochloric  acid.  There 
are  no  ganglion  globules  in  this 
plexus,  which  consists  of  tubular 
fibres,  a.  Twig  of  cochlear  nerve 
in  the  modiolus,  its  fibres  diverging 
and  reuniting  in  6,  a  band  in  the 
plexus  taking  a  direction  parallel 
to  the  zones.  From  this  other 
twigs  radiate,  and  again  and  again 
branch  and  unite  as  far  as  the  mar- 
gin of  the  osseous  zone  c,  where 
they  terminate.  From  the  sheep. 
Magnified  30  diameters.] 

pearances  there  seen ;  some  observers  affirming  that  there  are  no  free  or 
papillary  terminations,  and  that  the  nervous  fibres  all  return  by  loops ;  whilst 
others  state  that  the  papillae  are  clearly  to  be  distinguished.  The  fact  appears 
to  be  that,  as  in  the  retina,  the  fibres  do  form  a  minute  plexus;  but  that  fibres 
are  connected  with  this,  which  end,  or  rather  commence  in  papillae.  The 
Auditory  nerve  is  also  very  minutely  distributed  on  the  membrane  lining  the 
vestibule  and  semicircular  canals ;  and  in  the  ampullae  or  dilated  extremities 
of  the  latter,  there  are  little  projections  of  this  membrane  internally,  which 
are  largely  supplied  with  nerves. 

560.  In  order  to  gain  any  definite  idea  of  the  uses  of  different  parts  of  the 
Ear,  it  is  necessary  to  bear  in  mind,  that  sounds  may  be  propagated  amongst 
solid  or  fluid  bodies  in  three  ways, — by  reciprocation,  by  resonance,  and  by 
conduction. — 1.  Vibrations  of  reciprocation  are  excited  in  a  sounding  body, 
when  it  is  capable  of  yielding  a  musical  tone  of  definite  pitch,  and  another 
body  of  the  same  pitch  is  made  to  sound  near  it.  Thus  if  two  strings  of  the 
same  length  and  tension  be  placed  along  side  of  each  other,  and  one  of  them 
be  sounded  with  a  violin-bow,  the  other  will  be  thrown  into  reciprocal  vibra- 
tion ;  or  if  the  same  tone  be  produced  near  the  string  in  any  other  manner, 
as  by  a  flute,  or  a  tuning-fork,  the  same  effect  will  result. — 2.  Vibrations  of 
resonance  are  of  somewhat  the  same  character;  but  they  occur  when  a  sound- 


428 


ON  SENSATION,  AND  THE  ORGANS  OF  THE  SENSES. 
[Fig.  189. 


The  soft  parts  of  the  Vestibule  taken  out  of  their  bony  case,  so  as  to  show  the  distribution  of  the  Nerves 
in  the  Ampullae  ;  1,  the  superior  semicircular  membranous  canal  or  tube ;  2,  the  external  semicircular 
lube ;  3,  the  inferior  semicircular  tube ;  4,  the  tube  of  union  of  the  superior  and  inferior  canals ;  5,  the 
sacculus  ellipticus  ;  6,  the  sacculus  sphericus  ;  7,  the  portio  dura  nerve ;  8,  the  anterior  fasciculus  of  the 
auditory  nerve ;  9,  the  nerve  to  the  sacculus  sphericus ;  10, 10,  the  nervous  fasciculi  to  the  superior  and 
external  ampullae ;  11,  the  nerve  to  the  sacculus  ellipticus  ;  12,  the  posterior  fasciculus  of  the  auditory 
nerve,  furnishing  13,  the  filaments  of  the  sacculus  sphericus,  and  14,  the  filaments  of  the  cochlea,  cut  off.] 

[Fig.  190. 


The  Ampulla  of  the  External  Semicircular  Membranous  Canal,  showing  the  Mode  of  termination  of  its 
Nerve.] 

ing  body  is  placed  in  connection  with  any  other,  of  which  one  or  more  parts 
may  be  thrown  into  reciprocal  vibration,  even  though  the  tone  of  the  whole 
be  different,  or  it  be  not  capable  of  producing  a  definite  tone  at  all.  This  is 
the  case,  for  example,  when  a  tuning-fork  in  vibration  is  placed  upon  a  sound- 
board ;  for  even  though  the  whole  board  have  no  definite  fundamental  note,* 

*  The  fundamental  note  of  a  body  is  the  lowest  tone  which  it  will  yield,  when  the  whole 
of  it  is  in  vibration  together.     By  dividing  the  body  into  two  or  more  distinct  parts,  it  may 


SENSE  OF  HEARING.  429 

it  will  divide  itself  into  a  number  of  parts,  which  will  reciprocate  the  original 
sound,  so  as  greatly  to  increase  its  intensity;  and  the  same  sound-board  will 
act  equally  well  for  tuning-forks  of  several  different  degrees  of  pitch.  When 
a  smaller  body  is  used  for  resonance,  however,  it  is  essential  that  there  should 
be  a  relation  between  its  fundamental  note  and  that  of  the  sonorous  body ; 
otherwise  no  distinct  resonance  is  produced.  Thus,  if  a  tuning-fork  in  vibra- 
tion be  held  over  a  column  of  air  in  a  tube,  of  such  a  length  that  the  same  note 
would  be  given  by  its  vibration,  its  sound  wrill  be  reciprocated.  And  if  it  be 
held  over  a  pipe,  the  column  of  air  in  which  is  a  multiple  o,f  this,  the  column 
will  divide  itself  into  that  number  of  shorter  parts,  each  of  which  will  recipro- 
cate the  original  sound,  and  the  total  action  will  be  one  of  resonance.  But  if 
the  length  of  the  pipe  bear  no  such  correspondence  with  the  note  sounded  by 
the  tuning-fork,  no  resonance  is  given  by  the  column  of  air  it  contains. — 3. 
Vibrations  of  conduction  are  the  only  ones  by  which  sounds  can  strictly  be 
said  to  be  propagated.  These  are  distinguishable  into  various  kinds,  into 
which  it  is  not  requisite  here  to  inquire.  It  should  be  remarked,  however, 
that  all  media,  fluid,  liquid,  or  solid,  are  capable  of  transmitting  sound  in  this 
manner, — a  vacuum  being  the  only  space  through  which  it  cannot  pass. 
The  transmission  is  usually  much  more  rapid  through  solid  bodies,  than 
through  liquid  ;  and  through  liquid,  than  through  gaseous.  The  greatest 
diminution  in  the  intensity  of  sound  is  usually  perceived,  when  a  change  takes 
place  in  the  medium  through  which  it  is  propagated,  especially  from  the  aeri- 
form to  the  liquid. 

561.  The  detailed  application  of  these  principles  has  been  most  elaborately 
worked  out  by  Miiller ;  and  the  following  statement  of  what  may  be  regarded 
as  the  present  condition  of  our  knowledge  of  the  subject,  is  little  more  than 
an  abstract  of  his  results.  Considering  it  desirable,  in  the  first  place,  to  estab- 
lish the  conditions  under  which  those  animals  hear  that  are  constantly  im- 
mersed in  water,  he  made  a  series  of  experiments,  from  which  he  draws  the 
following  conclusions  : — i.  Sonorous  vibrations,  excited  in  water,  are  imparted 
with  considerable  intensity  to  solid  bodies. — n.  Sonorous  vibrations  of  solid 
bodies  are  communicated  with  greater  intensity  to  other  solid  bodies  brought 
in  contact  with  them,  than  to  water ;  but  with  much  greater  intensity  to 
water,  than  to  atmospheric  air. — in.  Sonorous  vibrations  are  communicated 
from  air  to  water  with  great  difficulty,— with  very  much  greater  difficulty 
than  they  are  propagated  from  one  part  of  the  air  to  another ;  but  their  transi- 
tion from  air  to  water  is  much  facilitated,  by  the  intervention  of  a  membrane 
extended  between  them. — iv.  Sonorous  vibrations  are  not  only  imparted  from 
water  to  solid  bodies  with  definite  surfaces,  which  are  in  contact  with  the 
water,  but  are  also  returned  with  increased  intensity  by  these  bodies  to  the 
water ;  so  that  the  sound  is  heard  loudly  in  the  vicinity  of  those  bodies,  in 
situations  where,  if  it  had  its  origin  in  the  conducting  power  of  the  water 
alone,  it  would  be  faint. — v.  Sonorous  undulations,  propagated  through  water, 
are  partially  reflected  by  Jhe  surfaces  of  solid  bodies. — vi.  Thin  membranes 
conduct  sound  in  water  without  any  loss  of  its  intensity,  whether  they  be 
tense  or  lax. — From  in.,  iv.,  and  vi.,  we  learn  the  mode  in  which  the  sound 

be  made  to  give  a  great  variety  of  sounds.  Thus,  if  a  stretched  string  be  divided  by  a  bridge 
into  two  equal  parts,  each  will  sound  the  octavo  of  the  fundamental  note,  or  the  8th  note 
above  it.  If  it  be  divided  into  three  parts,  each  will  give  the  12th  above  the  fundamental 
note;  if  into  four,  the  15th  or  double  octave  will  be  heard;  if  into  five,  the  17th;  if  into  six, 
the  19th  ;  if  into  seven,  the  20^th  (flat  seventh  above  the  second  octave);  if  into  eight,  the 
22d  or  triple  octave.  A  string  forcibly  set  in  vibration  has  a  tendency  to  sound  these  har- 
monics with  the  fundamental  note,  by  spontaneous  division  into  several  distinct  segments  of 
vibration ;  as  may  be  easily  made  evident  by  striking  one  of  the  lower  keys  of  the  piano, 
and  listening  to  the  sounds  heard  whilst  the  fundamental  note  is  dying  away. 


430  ON  SENSATION,  AND  THE  ORGANS  OF  THE  SENSES. 

is  conducted  to  the  ear,  in  aquatic  animals  not  breathing  atmospheric  air. 
The  labyrinth  of  such  is  either  entirely  inclosed  within  the  bones  of  the  head, 
as  in  the  Cephalopoda,  and  in  the  Cyclostome  and  Osseous  Fishes ;  or,  its 
cavity  being  prolonged  to  the  surface  of  the  body,  it  is  there  brought  into 
communication  with  the  conducting  medium,  by  means  of  a  membrane, — be- 
sides receiving  the  vibrations  through  the  medium  of  the  solids  of  the  body, 
as  is  the  case  in  Cartilaginous  Fishes  and  Crustacea.  It  would  seem  as  if, 
in  the  Osseous  Fishes,  the  resonance  of  the  cranial  bones,  in  which  the  laby- 
rinth is  imbedded,  were  sufficient  to  give  the  requisite  increase  of  intensity  to 
the  sound ;  whilst  in  the  Cartilaginous  orders,  the  softness  of  these  bones 
renders  some  other  means  necessary.  In  addition  to  this,  we  find  in  many 
Fishes  a  communication  with  the  air-bladder;  which  indeed  seems  to  have, 
in  these,  but  little  other  use.  The  mode  in  which  this  increases  by  resonance 
the  intensity  of  the  sounds,  will  appear  from  the  following  experimental  con- 
clusions.— vii.  When  sonorous  vibrations  are  communicated  from  water  to 
air  inclosed  in  membranes  or  solid  bodies,  a  considerable  increase  in  the  in- 
tensity of  the  sound  is  produced,  by  the  resonance  of  the  air  thus  circum- 
scribed.— vin.  A  body  of  air  inclosed  in  a  membrane,  and  surrounded  by 
water,  also  increases  the  intensity  of  the  sound  by  resonance,  when  the  sono- 
rous undulations  are  communicated  to  it  by  a  solid  body.  From  these  ob- 
servations, it  may  be  concluded,  that  the  air-bladder  of  Fishes,  in  addition  to 
other  uses,  serves  the  purpose  of  increasing  by  resonance  the  intensity  of  the 
sonorous  undulations,  communicated  from  the  water  to  the  body  of  the  Fish. 
Moreover,  as  the  conducting  and  resonant  power  of  the  air  in  the  air-bladder 
is  greater  in  proportion  to  its  density,  the  influence  of  this  organ  on  the  per- 
ception of  sounds  will,  of  course,  be  greater  in  deep  waters,  where  the  pres- 
sure upon  it  is  considerably  increased. 

562.  Most  animals  living  in  air,  are  provided  with  an  opening  into  the  ves- 
tibule, covered  by  a  thin  membrane;  and,  in  the  majority  of  cases,  with  the 
tympanic  apparatus  also.  The  following  experimental  results  bear  upon  the 
manner  in  which  the  Ear  of  such  animals  is  affected  by  sound. — ix.  Sono- 
rous undulations,  in  passing  from  air  directly  into  water,  suffer  a  considerable 
diminution  in  their  strength ;  while,  on  the  contrary,  if  a  tense  membrane 
exists  between  the  air  and  the  water,  the  sonorous  undulations  are  communi- 
cated from  the  former  to  the  latter  medium  with  great  intensity. — x.  The  so- 
norous vibrations  are  also  communicated  without  any  perceptible  loss  of  in- 
tensity, from  the  air  to  the  water  ;  when,  to  the  membrane  forming  the  me- 
dium of  communication,  there  is  attached  a  short  solid  body,  which  occupies 
the  greater  part  of  its  surface,  and  is  alone  in  contact  with  the  water. — xi.  A 
small  solid  body,  fixed  in  an  opening  by  means  of  a  border  of  membrane,  so 
as  to  be  movable,  communicates  sonorous  vibrations,  from  air  on  one  side,  to 
water  or  the  fluid  of  the  labyrinth  on  the  other,  much  better  than  solid  media 
not  so  constructed.  But  the  propagation  of  sound  to  the  fluid  is  rendered 
much  more  perfect,  if  the  solid  conductor,  thus  occupying  the  opening,  is  by 
its  other  end  fixed  to  the  middle  of  the  tense  membrane,  which  has  atmo- 
spheric air  on  both  sides. — The  fact  stated  in  ix.  is  evidently  one  of  great  im- 
portance in  the  physiology  of  hearing  ;  and  fully  explains  the  nature  of  the 
process  in  those  animals  which  receive  the  sonorous  vibrations  through  air, 
but  which  have  no  tympanic  apparatus.  In  x.  we  have  the  elucidation  of  the 
action  of  the  fenestra  ovalis,  and  of  the  movable  plate  of  the  stapes  which 
occupies  it,  in  animals  living  in  air,  but  destitute  of  tympanic  apparatus ;  this 
is  naturally  the  case  in  many  Amphibia ;  and  it  may  happen  as  the  result  of 
disease  in  the  Human  subject.  In  xi.  we  have  a  very  interesting  demonstra- 
tion of  the  purpose  and  action  of  the  tympanum,  in  the  more  perfect  forms  of 
the  auditory  apparatus.  We  are  now  prepared  to  inquire,  in  somewhat  more 


SENSE  OF  HEARING.  431 

of  detail,  into  the  action  of  the  different  parts  of  this  apparatus  ;  and  it  will  be 
better  to  commence  with  that  of  the  Internal  Ear,  the  accessory  organs  being 
afterwards  considered. 

563.  The  object  of  the  Membrana  Tympani  is  evidently  to  receive  the 
sonorous  undulations  from  the  air,  in  such  a  manner  as  to  be  thrown  by  them 
into  a  recriprocal  vibration,  which  is  to  be  communicated  to  the  chain  of  bones. 
This  membrane  is,  in  its  usual  state,  rather  lax  than  tense;  and  this  laxity  is 
found  by  experiment  to  be,  for  a  small  membrane,  the  best  condition  for  the 
propagation  of  ordinary  sounds.     This   is  easily  rendered  sensible  in  one's 
own  person  ;  for  an  increased  tension  may  be  given  to  the  membrana  tym- 
pani,  either  by  holding  the  breath  and  forcing  air  into  the  Eustachian  tube,  so 
as  to  distend  it  from  within,  or  by  exhausting  the  cavity,  so  as  to  cause  the 
external  air  to  make  increased  pressure  upon  it.     In  either  case  the  hearing  is 
found  immediately  to  become  indistinct.     It  is  observed,  however,  that  grave 
and  acute  sounds  are  not  equally  affected  by  this  action ;  for  the  experimenter 
renders  himself  deaf  to  grave  sounds,  whilst  acute  sounds  are  heard  even  more 
distinctly  than  before.     This  fact  is  easily  understood  by  referring  to  the  laws 
of  Acoustics  already  mentioned.     The  greater  the  tension  to  which  the  mem- 
brana tympani  is  subjected,  the  more  acute  will  be  its  fundamental  tone;  and 
as  no  proper  reciprocation  can  take  place  in  it,  to  any  sound  lower  than  its 
fundamental  tone,  its  power  of  repeating  perfectly  the  vibrations  proper  to  the 
deeper  notes  will  diminish.     The  nearer  a  sound  approaches  to  the  funda- 
mental note  proper  to  the  tense  membrane,  the  more  distinctly  will  it  be  heard. 
On  the  other  hand,  when  the  membrane  is  in  its  natural  lax  condition,  its  fun- 
damental note  is  very  low,  and  it  is  capable  of  repeating  a  much  greater  vari- 
ety of  sounds  ;  for,  when  it  receives  undulations  of  a  higher  tone,  than  those 
to  which  the  whole  membrane  would  reciprocate,  it  divides  itself  into  distinct 
segments  of  vibration,  which  are  separated  by  lines  of  rest;  and  every  one  of 
these  reciprocates  the  sound;*  at  the  same  time  rendering  it  more  intense  by 
multiplication.     These  facts  enable  us  to  understand  the  influence  of  the  ten- 
sor tympani  muscle,  in  modifying  the  tension  of  the  membrane,  and  thus  caus- 
ing it  to  vibrate  in  reciprocation  to  sounds  having  a  great  variety  of  funda- 
mental notes.     Moreover,  the  fact  that  some  persons  are  deaf  to  grave  sounds, 
whilst  they  readily  hear  the  more  acute,  is  thus  accounted  for.     The  tensor 
tympani,  like  the  iris,  is  probably  excited  to  operation  by  a  reflex  action ;  and 
it  is  by  no  means  improbable  that  one  of  its  functions  may  be,  to  prevent  the 
internal  ear  from  being  too  violently  affected  by  loud  sounds,  by  putting  the 
membrana  tympani  into  such  a  state  of  tension,  as  not  readily  to  reciprocate 
them. 

564.  The  uses  of  the  Tympanic  cavity  are  very  obvious.     One  of  its  pur- 
poses is,  to  render  the  vibrations  of  the  membrane  quite  free ;  and  the  other, 
to  isolate  the  chain  of  bones,  in  such  a  manner  as  to  prevent  their  vibrations 
from  being  weakened,  by  diffusion  through  the  surrounding  solid  parts.    As  to 
the  objects  of  the  Eustachian  tube,  however,  opinions  have  been  much  divided. 
From  the  experiments  of  Muller  it  appears,  that  it  does  not  increase  the  intens- 
ity of  sound,  but  that  it  prevents  a  certain  degree  of  dulness,  which  would 
attend  it,  if  the  cavity  of  the  tympanum  were  completely  closed  ;  of  this  dul- 
ness we  are  conscious,  when  any  tumefaction  of  the  fauces  causes  an  occlusion 
of  the  extremity  of  the  tube.     It  has  been  supposed  that,  among  other  uses, 

*  This  is  very  eas.ily  proved  by  experiments  on  a  membrane  stretched  over  a  resonant 
cavity  5  if  light  sand  be  strewed  upon  it,  and  a  strong  musical  tone  be  produced  in  its  vicinity, 
the  membrane  will  immediately  be  set  in  vibration,  not  as  a  whole  (unless  its  fundamental  note 
be  in  unison  with  that  sounded),  but  in  distinct  segments,  of  which  every  one  reciprocates  the 
sound ;  from  the  vibrating  parts,  the  sand  will  be  violently  thrown  off;  but  it  will  settle  on  the  in- 
termediate linesof  rest,  forming  a  variety  of  curious  figures,  which,  are  known  as  the  nodal  lines. 


432  ON  SENSATION,  AND  THE  ORGANS  OF  THE  SENSES. 

this  canal  serves  for  the  conduction  of  the  speaker's  voice  to  his  ears  ;  but  this 
is  certainly  not  the  case  in  any  considerable  degree  ;  for,  when  the  Eustachian 
tubes  are  obstructed  by  disease,  the  patient  hears  his  own  voice  well,  though 
other  sounds  are  indistinct;  and  it  is  easily  shown,  that  its  transmission  is 
chiefly  accomplished  in  other  ways.  The  common  idea  is,  that  it  serves  the 
same  purpose  with  the  hole  in  an  ordinary  drum  ;  the  effect  of  which  is  gene- 
rally supposed  to  be,  the  removal  of  the  impediment  to  the  vibrations  of  the 
membrane,  that  would  be  offered  by  the  complete  inclosure  of  the  air  within. 
It  does  not  appear,  however,  that  any  such  impediment  is  really  offered  ;  and 
the  effect  of  the  hole  in  the  drum  seems  rather  to  be  the  communication,  to 
the  ear  of  the  auditor,  of  the  sonorous  vibrations  of  the  contained  air ;  which 
are  thus  transmitted  directly  through  the  atmosphere,  instead  of  being  weak- 
ened by  transmission  through  the  walls  of  the  instrument.  Hence  there  is  no 
real  analogy  in  the  two  cases.  The  principal  object  of  the  Eustachian  tube 
(which  is  always  found  where  there  is  a  tympanic  cavity),  seems  to  be,  the 
maintenance  of  the  equilibrium  between  the  air  within  the  tympanum  and  the 
external  air ;  so  as  to  prevent  inordinate  tension  of  the  membrana  tympani, 
which  would  be  produced  by  too  great  or  too  little  pressure  on  either  side, 
and  the  effect  of  which  would  be  imperfection  of  hearing.  It  also  has  the 
office  of  conveying  away  mucus  secreted  in  the  cavity  of  the  tympanum,  by 
means  of  cilia  vibrating  on  its  lining  membrane ;  and  the  deafness,  conse- 
quent on  occlusion  of  this  tube,  is  in  part  explicable  by  the  accumulation, 
which  will  then  take  place  in  the  tympanum. 

565.  From  what  has  been  stated,  it  is  evident  that  sonorous  undulations 
taking  place  in  the  air,  will  be  propagated  to  the  fluid  contained  in  the  laby- 
rinth,— through  the  tympanum,  the  chain  of  bones,  and  the  membrane  of  the 
fenestra  ovalis  to  which  the  stapes  is  attached, — without  any  loss,  but  rather 
an  increase,  of  intensity.  Why  water  should  be  chosen  as  the  medium  through 
which  the  impression  is  to  be  made  upon  the  nerve,  it  is  impossible  for  us  to 
say  with  anything  like  certainty,  in  our  present  state  of  ignorance  as  to  the 
physical  character  of  that  impression.  But,  the  problem  being,  to  communi- 
cate to  water  the  sonorous  undulations  of  air,  the  experimental  results  already 
detailed  satisfactorily  prove  that, — whilst  this  may  be  accomplished,  in  a  de- 
gree sufficient  for  the  wants  of  the  inferior  animals,  by  the  simple  interposition 
of  a  tense  membrane  between  the  air  and  the  fluid, — the  tympanic  apparatus 
of  the  higher  classes  is  most  admirably  adapted  for  this  purpose.  The  fenes- 
tra ovalis  is  not,  however,  the  only  channel  of  communication  between  the 
tympanum  and  the  labyrinth  ;  for  there  is,  in  most  animals,  a  second  aperture, 
the  fenestra  rotunda,  leading  into  the  cochlea,  and  simply  covered  with  a  mem- 
brane. It  is  generally  supposed  that,  the  labyrinth  being  filled  with  a  nearly 
incompressible  fluid,  this  second  aperture  is  necessary  to  allow  of  the  free 
vibration  of  that  fluid, — the  membrane  of  the  fenestra  rotunda  being  made  to 
bulge  out,  as  that  of  the  fenestra  ovalis  is  pushed  in.  It  may,  however,  be 
easily  shown  by  experiment,  as  well  as  by  reference  to  comparative  anatomy, 
that  no  such  contrivance  is  necessary ;  for  sonorous  undulations  may  be  ex- 
cited in  a  non-elastic  fluid,  completely  inclosed  within  solid  walls  at  every 
part,  except  where  these  are  replaced  by  the  membrane  through  which  the 
vibrations  are  propagated ;  and  this  is  precisely  the  condition,  not  only  of  the 
Invertebrated  animals,  but  even  of  Frogs  ;  in  which  last  a  tympanic  apparatus 
exists,  without  a  second  orifice  into  the  labyrinth.  Moreover  it  is  certain,  that 
the  vibrations  of  the  air  in  the  cavity  of  the  tympanum,  must  of  themselves 
act  upon  the  membrane  of  the  fenestra  rotunda;  and  this  is  perhaps  the  most 
direct  manner  in  which  the  fluid  in  the  cochlea  will  be  affected ;  although  it 
will  ultimately  be  thrown  into  much  more  powerful  action,  by  the  transmission 
of  vibrations  from  the  vestibule.  For  it  has  been  satisfactorily  determined  by 


SENSE  OF  HEARING. 

[Fig.  191. 


433 


The  labyrinth  of  the  Left  Ear,  laid  open  in  order  to  show  its  cavities  and  the  Membranous  Labyrinth ; 
after  Breschet ;  1,  the  cavity  of  the  vestibule,  opened  from  its  anterior  aspect  in  order  to  show  the  three- 
cornered  form  of  its  interior,  and  the  membranous  labyrinth  which  it  contains ;  the  figure  rests  upon  the 
common  saccule  of  the  membranous  labyrinth— the  sacculus  communis ;  2,  the  ampulla  of  the  superior 
or  perpendicular  semicircular  canal,  receiving  a  nervous  fasciculus  from  the  superior  branch  of  the 
vestibular  nerve ;  3,  4,  the  superior  or  perpendicular  canal  with  its  contained  membranous  canal ;  5,  the 
ampulla  of  the  inferior  or  horizontal  semicircular  canal,  receiving  a  nervous  fasciculus  from  the  superior 
branch  of  the  vestibular  nerve  ;  6,  the  termination  of  the  membranous  canal  of  the  horizontal  semicircular 
canal  in  the  sacculus  communis  ;  7,  the  ampulla  of  the  middle  or  oblique  semicircular  canal,  receiving  a 
nervous  fasciculus  from  the  inferior  branch  of  the  vestibular  nerve  ;  8,  the  oblique  semicircular  canal 
with  its  membranous  canal ;  9,  the  common  canal,  resulting  from  the  union  of  the  perpendicular  with 
the  oblique  semicircular  canal ;  10,  the  membranous  common  canal  terminating  in  the  sacculus  com- 
munis ;  11,  the  otoconite  of  the  sacculus  communis  seen  through  the  membranous  parietes  of  that  sac  ;  a 
nervous  fasciculus  from  the  inferior  branch  of  the  vestibular  nerve  is  seen  to  be  distributed  to  the  saccu- 
lus communis  near  to  the  otoconite  ;  the  extremity  of  the  sacculus  above  the  otoconite  is  lodged  in  the 
superior  ventricle  of  the  vestibule,  and  that  below  it  in  the  inferior  ventricle ;  12,  the  sacculus  proprius 
situated  in  the  anterior  ventricle ;  its  otoconite  is  seen  through  its  membranous  parietes,  and  a  nervous 
fasciculus  derived  from  the  middle  branch  of  the  vestibular  nerve,  is  distributed  to  it ;  the  spaces  around 
the  membranous  labyrinth  are  occupied  by  the  aqua  labyrinthi;  13,  the  first  turn  of  the  cochlea;  the 
figure  is  situated  in' the  scala  tympani;  14,  the  extremity  of  the  scala  tympani  corresponding  with  the 
fenestra  rotunda;  15,  the  lamina  spiralis ;  the  figure  is  situated  in  the  scala  vestibuli ;  16,  the  opening  of 
the  scala  vestibuli  into  the  vestibule;  17,  the  second  turn  of  the  cochlea;  the  figure  is  placed  upon  the 
lamina  spiralis,  and,  therefore,  in  the  scala  vestibuli,  the  scala  tympani  being  beneath  the  lamina;  18, 
the  remaining  half  turn  of  the  cochlea  ;  the  figure  is  placed  in  the  scala  tympani;  19,  the  lamina  spiralis 
terminating  in  a  falciform  extremity ;  the  dark  space  included  within  the  falciform  curve  of  the  extremity 
of  the  lamina  spiralis  is  the  helicotrema;  20,  the  infundibulum.] 

experiment  (xii.),  that  vibrations  are  transmitted  with  very  much  greater  in- 
tensity to  water,  when  a  tense  membrane,  and  a  chain  of  insulated  solid  bodies 
capable  of  free  movement,  are  successively  the  conducting  media,  than  when 
the  media  of  communication  between  the  vibrating  air  and  the  water  are  the 
same  tense  membrane,  air,  and  a  second  membrane : — or,  to  apply  this  fact 
to  the  organ  of  hearing,  the  same  vibrations  of  the  air  act  upon  the  fluid  of  the 
labyrinth  with  much  greater  intensity,  through  the  medium  of  the  chain  of 
auditory  bones  and  the  fenestra  ovalis,  than  through  the  medium  of  the  air  of 
the  tympanum  and  the  membrane  closing  the  fenestra  rotunda. — The  fenestra 
rotunda  is  not  to  be  considered  as  having  any  peculiar  relation  with  the  cochlea ; 
since,  in  the  Turtle  tribe,  the  former  exists  without  the  latter. 

566.  In  regard  to  the  functions  of  particular  parts  of  the  labyrinth,  no  cer- 
tainty can  be  said  to  exist.  From  the  experimental  results  already  stated,  it 
appears  likely  that,  the  greater  the  extension  of  the  cavity  into  the  dense  sub- 
stance of  the  bone,  the  greater  will  be  the  resonance  communicated  to  the 
fluid,  and  thence  transmitted  to  the  nerves  exposed  to  its  influence. — It  is 
37 


434  ON  SENSATION,  AND  THE  ORGANS  OF  THE  SENSES. 

[Fig.  192. 


A  view  of  the  labyrinth  of  the  Left  Side,  laid  open  in  its  whole  extent  so  as  to  show  its  Structure ;  these 
figures  are  all  magnified  ;  1,  the  thickness  of  the  outer  covering  of  the  cochlea;  2,  2,  the  scala  vestibuli 
or  upper  layer  of  the  lamina  spiralis  ;  3,  3,  the  scala  tympani  or  lower  layer  of  the  lamina  spiralis ;  4,  the 
hamulus  cochleae ;  5,  centre  of  the  infundibulum ;  6,  the  foramen  rotundum  communicating  with  the  tym- 
panum ;  7,  the  thickness  of  the  outer  layer  of  the  vestibule  ;  8,  the  foramen  rotundum  ;  9,  the  fenestra 
ovalis ;  10,  the  orifice  of  the  aqueduct  of  the  vestibule  ;  11,  the  inferior  semicircular  canal ;  12.  the  superior 
semicircular  canal ;  13,  the  external  semicircular  canal ;  14,  the  ampulla  of  the  inferior  canal ;  15,  the 
ampulla  of  the  superior  canal ;  16,  the  common  orifice  of  the  superior  and  inferior  canals ;  17,  the  ampulla 
of  the  external  canal.] 

commonly  supposed  that  the  Semicircular  Canals  have  for  their  peculiar  func- 
tion, the  reception  of  the  impressions  by  which  we  distinguish  the  direction  of 
sounds;  and  it  is  certainly  a  powerful  argument  in  support  of  this  view,  that, 
in  almost  every  instance  in  which  these  parts  exist  at  all,  they  hold  the  same 
relative  position  to  each  other  as  in  Man,  their  three  planes  being  nearly  at 
right  angles  to  one  another.  The  idea,  however,  must  be  regarded  as  a  mere 
speculation,  the  value  of  which  cannot  be  decided  without  an  increased  know- 
ledge of  the  laws,  according  to  which  sonorous  vibrations  are  transmitted. — 
Regarding  the  special  function  of  the  Cochlea,  there  is  precisely  the  same  un- 
certainty. This  part  of  the  organ  is  peculiar  in  one  respect, — that  the  expan- 
sion of  the  auditory  nerve  is  here  spread  out  (upon  the  lamina  spiralis)  in 
closer  proximity  with  the  bone  itself,  than  it  is  in  any  other  part  of  the  laby- 
rinth ;  so  that  the  vibrations  of  the  bone  will  be  more  directly  communicated 
to  the  nerve.  It  is  not  easy  to  see,  however,  what  can  be  the  peculiar  object 
of  this  disposition,  in  regard  to  the  function  of  hearing.  By  M.  Duges  it  is 
surmised,  that  by  the  cochlea  we  are  especially  enabled  to  estimate  the  pitch 
of  sounds,  particularly  of  the  voice ;  and  he  adduces,  in  support  of  this  idea, 
the  fact,  that  the  development  of  the  cochlea  follows  a  very  similar  proportion 
with  the  compass  of  the  voice.  This  is  much  the  greatest  in  the  Mammalia; 
less  in  Birds  ;  and  in  Reptiles,  which  have  little  true  vocal  power,  the  cochlea 
is  reduced  to  its  lowest  form,  disappearing  entirely  in  the  Amphibia.  That 
there  should  be  an  acoustic  relation  between  the  voice  and  ear  of  each  species 
of  animal,  cannot  be  regarded  as  improbable  ;  but  the  speculation  of  M.  Duges 
can  at  present  only  be  received  as  a  stimulus  to  further  inquiry. 

567.  We  have  now  to  consider  the  functions  of  the  accessory  parts, — the 
External  Ear,  and  the  Meatus.     The  Cartilage  of  the  external  ear  may  pro- 


SENSE  OF  HEARING. 


435 


pagate  sonorous  vibrations  in  two  ways, — by  reflection,  and  by  conduction. 
In  reflection,  the  concha  is  the  most  important  part,  since  it  directs  the  reflected 
undulations  towards  the  tragus,  whence  they  are  thrown  into  the  auditory 
passage.  The  other  inequalities  of  the  external  ear  cannot  promote  hearing 
by  reflection ;  and  the  purpose  of  the  extension  of  its  cartilage  is  evidently  to 
receive  the  sonorous  vibrations  from  the  air,  and  to  conduct  them  to  its  point 
of  attachment.  In  this  point  of  view,  the  inequalities  become  of  importance  ; 
for  those  elevations  and  depressions  upon  which  the  undulations  fall  perpen- 
dicularly, will  be  affected  by  them  in  the  most  intense  degree  ;  and  in  conse- 


[Fig.  193. 


[Fig.  194. 


A  view  of  the  Left  Ear  in  its  natural  state ;  1, 2, 
the  origin  and  termination  of  the  helix  ;  3,  the  anti- 
helix  ;  4,  the  anti-tragus ;  5,  the  tragus ;  6,  the  lobus 
of  the  external  ear ;  7,  points  to  the  scapha  and  is  on 
the  front  and  top  of  the  pinna ;  8,  the  concha;  9,  the 
meatus  auditorius  externus.] 


An  anterior  view  of  the  External  Ear,  as  well 
as  of  the  Meatus  Auditorius,  Labyrinth,  &c. ;  1, 
the  opening  into  the  ear  at  the  bottom  of  the  con- 
cha ;  2,  the  meatus  auditorius  externus  or  car- 
tilaginous canal  ;  3,  the  membrana  tympani 
stretching  upon  its  ring ;  4,  the  malleus ;  5,  the 
stapes ;  6.  the  labyrinth.] 


quence  of  the  varied  form  and  position  of  these  inequalities,  sonorous  undula- 
tions, in  whatever  direction  they  may  come,  must  fall  advantageously  upon 
some  of  them. — The  functions  of  the  Meatus  appear  to  be  threefold.  The 
sonorous  undulations  entering  from  the  atmosphere  are  propagated  directly, 
without  dispersion,  to  the  membrana  tympani : — the  sonorous  undulations 
received  on  the  external  ear,  are  conveyed  along  the  walls  of  the  meatus  to 
the  membrana  tympani: — the  air  which  it  contains,  like  all  insulated  masses 
of  air,  increases  the  intensity  of  sounds  by  resonance.  That,  in  ordinary 
hearing,  the  direct  transmission  of  atmospheric  vibrations  to  the  membrana 
tympani,  is  the  principal  means  of  exciting  the  reciprocal  vibrations  of  the 
latter,  is  sufficiently  evident ;  the  undulations  which  directly  enter  the  passage, 
will  pass  straight  on  to  the  membrane ;  whilst  those  that  enter  obliquely  will 
be  reflected  from  side  to  side,  and  at  last  will  fall  obliquely  on  the  membrane, 
thus  perhaps  contributing  to  the  notion  of  direction.  The  power  of  the  lining 
of  the  meatus  to  conduct  sound  from  the  external  ear,  is  made  evident  by  the 
fact,  that,  when  both  ears  are  closely  stopped,  the  sound  of  a  pipe  having  its 
lower  extremity  covered  by  a  membrane,  is  heard  more  distinctly,  when  it  is 
applied  to  the  cartilage  of  the  external  ear  itself,  than  when  it  is  placed  in  con- 
tact with  the  surface  of  the  head.  The  resonant  action  of  the  air  in  the  tube 
is  easily  demonstrated,  by  lengthening  the  passage  by  the  introduction  of 


436  ON  SENSATION,  AND  THE  ORGANS  OF  THE  SENSES. 

another  tube ;  the  intensity  of  external  sounds,  and  also  that  of  the  individual's 
own  voice,  as  heard  by  himself,  is  then  much  increased. 

568.  Many  facts  prove,  however,  that  the  fluid  of  the  labyrinth  may  be 
thrown  into  vibration  in  other  ways,  than  by  the  tympanic  apparatus.     Thus 
in  Osseous  Fishes,  it  is  only  by  the  vibrations  transmitted  through  the  bones 
of  the  head,  that  hearing  can  take  place.     There  are  many  persons,' again, 
who  can  distinctly  hear  sounds  which  are  thus  transmitted  to  them  ;  although, 
through  some  imperfection  of  the  tympanic  apparatus,  they  are  almost  insen- 
sible to  those  which  they  receive  in  the  ordinary  way.     It  is  evident,  where 
this  is  the  case,  that  the  nerve  must  be  in  a  state  fully  capable  of  functional 
activity ;  and,  on  the  other  hand,  where  sounds  cannot  thus  be  perceived, 
there  will  be  good  reason  to  believe  that  the  nerve  is  diseased. 

569.  A  single  impulse  communicated  to  the  Auditory  nerve,  in  any  of  the 
foregoing  modes,  seems  to  be  sufficient  to  excite  the  momentary  sensation  of 
sound;  but  most  frequently  a  series  of  such  impulses  is  concerned,  there 
being  but  few  sounds  which  do  not  partake,  in  a  greater  or  less  degree,  of 
the  character  of  a  tone.     Any  continuous  sound  or  tone  is  dependent  upon  a 
succession  of  such  impulses ;  and  its  acuteness  or  depth  is  governed  by  the 
rapidity  with  which  they  succeed  one  another. 

a.  It.  is  not  difficult  to  ascertain  by  experiment,  what  number  of  such  impulses  or  undula- 
tions are  required,  to  give  every  tone  which  the  ear  can  appreciate.  Thus,  if  a  circular  plate, 
with' a  number  of  apertures  at  regular  intervals,  be  made  to  revolve  over  the  top  of  a  pipe 
through  which  air  is  propelled,  a  succession  of  short  pvffs  will  be  allowed  to  issue  from  this; 
and,  if  the  revolution  is  sufficiently  rapid,  these  impulses  will  unite  into  a  definite  tone.  In 
the  same  manner,  if  a  spring  be  fixed  near  the  edge  of  a  revolving  toothed  wheel,  in  such 
a  manner  as  to  be  caught  by  every  tooth  as  it  passes,  a  succession  of  clicks  will  be  heard ; 
and  these  too,  if  the  revolution  of  the  wheel  be  sufficiently  rapid,  will  produce  a  tone.  The 
number  of  apertures  in  the  plate,  which  pass  the  orifice  of  the  pipe  in  a  given  time,  or  the 
number  of  teeth  which  pass  the  spring,  being  known,  it  is  easy  to  see,  that  this  must  be  the 
number  of  impulses  required  to  produce  the  given  tone.  Each  impulse  produces  a  double 
vibration, — forwards  and  backwards  (as  is  seen  when  a  string  is  put  in  vibration,  by  pulling 
it  out  of  the  straight  line) ;  hence  the  number  of  impulses  is  always  half  that  of  the  single 
vibrations.  The  maximum  and  minimum  of  the  intervals  of  successive  pulses,  still  appre- 
ciable by  the  ear  as  determinate  sounds,  have  also  been  determined  by  M.  Savart,  more  satis- 
factorily and  more  accurately  than  had  previously  been  done.  If  their  intensity  is  great, 
sounds  are  still  audible  which  result  from  the  succession  of  24,000  impulses  in  a  second ; 
and  this,  probably,  is  not  the  extreme  limit  to  the  acuteness  of  sounds  perceptible  by  the  ear. 
From  some  observations  of  Dr.  Wollaston's,  it  seems  probable  that  the  ears  of  different  indi- 
viduals are  differently  constituted  in  this  respect, — some  not  being  able  to  hear  very  acute 
tones  produced  by  Insects,  or  even  Birds,  which  are  distinctly  audible  to  others.  Again,  the 
sound  resulting  from  16  impulses  per  second,  is  not,  as  has  been  usually  supposed,  the  lowest 
appreciable  note ;  on  the  contrary,  M.  Savart  has  succeeded  in  rendering  tones  distinguisha- 
ble, which  are  produced  by  only  7  or  8  impulses  in  a  second;  and  continuous  sounds  of  a 
still  deeper  tone  could  be  heard,  if  the  individual  pulses  were  sufficiently  prolonged.  In 
regard,  however,  to  the  precise  time  during  which  a  sonorous  impression  remains  upon  the 
ear,  it  is  difficult  to  procure  exact  information,  since  it  departs  more  gradually  than  do  visual 
impressions  from  the  eye.  This  is  certain,  however, — that  it  is  much  longer  than  the  interval 
between  the  successive  pulses  in  the  production  of  tones;  since  it  was  found  by  M.  Savart, 
that  one  or  even  several  teeth  might  be  removed  from  the  toothed  wheel,  without  a  percep- 
tible break  in  its  sound, — showing  that,  when  the  tone  was  once  established,  the  impression 
of  it  remained  during  an  intermission  of  some  length. 

570.  The  Ear  may,  like  the   Eye,  vary  considerably,  as  regards  general 
acuteness  amongst  different  individuals;  and  its  power  may  be  much  increased 
by  practice.     A  part  of  this  increase  depends,  however,  as  in  other  instances, 
upon  the  greater  attention  which  its  fainter  indications  receive ;  but  a  part, 
also,  upon  an  increased  use  of  the  organ.     The  power  of  hearing  very  faint 
sounds,  is  as  different  from  the  power  of  distinguishing  musical  tories,  as  the 
power  of  discerning  very  minute  objects,  or  of  seeing  with  very  faint  degrees 
of  light,  is  from  that  of  distinguishing  colours.     Many  persons  are  altogether 


SENSE  OF  HEARING.  437 

destitute  of  what  is  termed  a  musical  ear ;  whilst  others  are  endowed  with  it 
in  a  degree,  which  is  a  source  of  great  discomfort  to  them,  since  every  discord- 
ant sound  is  a  positive  torment.  The  power  of  distinguishing  the  direction 
of  sounds  appears  to  be,  in  Man,  at  least,  for  the  most  part  acquired  by  habit. 
It  is  some  time  before  the  infant  seems  to  know  anything  of  the  direction  of 
noises,  which  attract  his  attention.  Now  although  there  can  be  no  question, 
that  this  perception  is  acquired  by  attention  to  certain  variations  in  the  impres- 
sion made  upon  the  nerve,  through  the  medium  either  of  the  tympanic  appa- 
ratus, or  of  the  bones  of  the  head,  yet  it  is  equally  evident,  that  there  can  be 
nothing  in  these  variations  themselves  adequate  to  excite  the  idea,  and  that  it 
must  therefore  be  either  intuitive  or  acquired  by  habit.  This  is  a  considera- 
tion of  some  importance,  in  regard  to  the  similar  question  as  to  the  sense  of 
Visual  direction.  In  some  cases  we  are  probably  assisted  by  the  relative  in- 
tensity of  the  sensations,  communicated  by  the  two  ears  respectively.  The 
idea  of  the  distance  of  the  sonorous  body  is  another  acquired  perception,  de- 
pending principally  upon  the  loudness  or  faintness  of  the  sound,  when  we 
have  no  other  indications  to  guide  us.  In  this  respect,  there  is  a  great  simi- 
larity between  the  perception  of  the  distance  of  an  object,  through  the  Eye, 
by  its  size,  and  through  the  Ear,  by  the  intensity  of  its  sound.  When  we 
know  the  size  of  the  object,  or  are  acquainted  with  the  usual  intensity  of  its 
sound,  we  can  judge  of  its  distance  ;  and  vice  versa,  when  we  know  its  dis- 
tance, we  can  at  once  form  an  idea  of  its  real  from  its  apparent  size,  and  of 
its  real  strength  of  tone  from  that  which  affects  our  ears.  In  this  manner, 
the  mind  may  be  affected  with  corresponding  deceptions  through  both  senses ; 
thus,  in  the  Phantasmagoria,  the  figure  is  gradually  diminished  whilst  its  dis- 
tance remains  the  same,  and  it  appears  to  the  spectators  to  recede, — the  illu- 
sion being  more  complete,  if  its  brightness  be  at  the  same  time  diminished ; 
and  the  effect  of  a  distant  full  military  band  gradually  approaching,  may  be 
alike  given  by  a  corresponding  crescendo  of  concealed  instruments.  It  is  upon 
the  complete  imitation  of  the  conditions  which  govern  our  ideas  of  the  intensity 
and  direction,  as  well  as  of  the  character,  of  sounds,  that  the  deceptions  of  the 
Ventriloquist  are  founded. 

571.  Some  facts  of  much  interest  have  lately  been  ascertained,  in  regard  to 
an  occasional  variation  in  the  rapidity  of  the  perception  of  sensory  impres- 
sions, received  through  the  Eye  and  through  the  Ear.     These  facts  are  the 
result  of  comparisons  made  amongst  different  astronomical  observers,  who 
may  be  watching  the  same  visual  phenomena,  and  timing  their  observations 
by  the  same  clock ;  for  it  has  been  remarked,  that  some  persons  see  the  same 
phenomenon,  a  third  or  even  half  of  a  second  earlier  than  others.     There  is 
no  reason  to  suppose  from  this,  however,  that  there  is  any  difference  in  the 
rate  of  transmission  of  the  sensory  impressions  in  the  two  nerves.     The  fact 
seems  rather  to  be,  that  the  sensorium  does  not  readily  perceive  two  different 
impressions  with  equal  distinctness  ;  and  that,  when  several  impressions  are 
made  on  the  nerves  at  the  same  time,  the  mind  takes  cognizance  of  one  only, 
or  perceives  them  in  succession.     When,  therefore,  both  sight  and  hearing  are 
directed  simultaneously  to  one  object,  the  communication  of  the  impression 
through  one  sense  will  necessarily  precede  that  made  by  the  other.     The  in- 
terval between  the  two  sensations  is  greater  in  some  persons  than  in  others ; 
for  some  can  receive  and  be   conscious  of  many  impressions,  seemingly  at 
the  same  moment ;  whilst  in  others  a  perceptible  space  must  elapse. 

572.  Amongst  other  important  offices  of  the  power  of  Hearing,  is  that  of 
supplying  the  sensations  by  which  the  Voice  is  regulated.     It  is  well  known 
that  those  who  are  born  entirely  deaf,  are  also  dumb, — that  is,  destitute  of  the 
power  of  forming  articulate  sounds  ;  even  though  not  the  least  defect  exist  in 
their  organs  of*  voice.     Hence  it  appears  that  the  vocal  muscles  can  only  be 

37* 


438  OF  MUSCULAR  CONTRACTION. 

guided  in  their  action  by  the  sensations  received  through  the  Ears,  in  the  same 
manner  as  other  muscles  are  guided  by  the  sensations  received  through  them- 
selves (§  433).  On  this  point,  more  will  be  said  hereafter  (§  611). 


C  H APTE  R    VII. 

OF  MUSCULAR  ACTIpN. 

I.— Of  Contractility  in  General. 

573.  THE  Nervous  System  has  no  power  of  occasioning  movement  in  any 
part  of  the  body,  save  by  exciting  to  contraction  certain  structures,  to  which 
the  term  Muscular  is  given.  That  one  tissue  should  possess  within  itself  the 
property  of  Contractility  on  the  application  of  a  stimulus,  is  no  more  wonderful, 
than  that  another  should  be  capable  of  conveying  sensory  or  motor  influences, 
or  another  of  separating  a  peculiar  secretion  from  the  blood.  Such  contractile 
tissues  are  found  in  Vegetables,  as  well  as  in  Animals ;  and  they  appear  to 
consist,  in  both  instances,  of  cells,  whose  peculiar  property  it  is  to  change 
their  form,  when  subjected  to  certain  kinds  of  irritation  (§  230).  The  only 
essential  difference  in  function,  between  the  Contractility  of  the  cells  compos- 
ing the  ultimate  fibrillae  of  Muscular  Fibre,  and  that  of  the  cells  composing 
the  intumescence  of  the  Sensitive  Plant,  consists  in  the  susceptibility  of  the 
former  to  a  stimulus,  which  does  not  operate  on  the  latter.  Both  can  be  made 
to  change  their  form  by  stimuli  of  various  kinds, — mechanical,  chemical, 
electrical,  &c., — directly  applied  to  themselves ;  but  the  contractility  of  Mus- 
cular fibre  is  excited,  in  addition,  by  the  stimulus  of  Innervation,  which  has 
no  operation  in  the  Plant ;  and  it  is  when  its  peculiar  property  is  thus  excited, 
that  the  Muscular  tissue  becomes  the  instrument  of  the  operation  of  the  Nerv- 
ous system  upon  the  external  world,  and  thus  performs  an  important  part  in 
the  purely  Animal  Functions. — The  Muscular  tissue,  however,  is  not  always 
thus  called  into  activity  through  the  medium  of  the  Nervous  system  ;  for  it  is 
employed  to  execute  numerous  movements,  which  are  immediately  connected 
with  the  maintenance  of  the  Organic  functions,  and  in  which  the  influence  of 
Innervation  seems  to  be  but  little  concerned ;  its  contractility  being  excited  to 
action  by  stimuli  directly  applied  to  itself. — We  have  seen  that  there  are  two 
forms  of  Muscular  tissue,  the  striated  and  the  non-striated,  which  are  appro- 
priated to  these  two  purposes ;  the  former  being  the  kind  most  readily  acted 
on  through  the  Nervous  System,  and  invariably  employed  in  the  Muscles  that 
are  called  into  action  by  its  influence ;  whilst  the  latter  (which  seems  a  less 
perfectly-developed  form  of  the  tissue)  is  with  difficulty  excited  to  contraction 
through  the  Nervous  System,  and  is  usually  employed  in  Muscles,  whose 
action  is  altogether  uncontrollable  by  the  will  (§§  225 — 234). 

574.  The  general  property  of  Contractility  shows  itself  under  two  forms ; 
which  are  alike  distinct  in  the  mode  of  their  action,  and  in  the  conditions 
requisite  for  its  excitation. — Its  most  obvious  and  striking  manifestations  pre- 
sent themselves  in  the  Voluntary  muscles  and  in  the  Heart ;  which,  when  in 
activity,  exhibit  powerful  contractions  tending  to  alternate  with  relaxations. 
The  modification  of  contractility  which  is  concerned  in  producing  these,  is 
distinguished  as  Irritability. — On  the  other  hand,  we  find  that  the  muscles 


OF  MUSCULAR  IRRITABILITY.  439 

exhibit  a  tendency  to  a  moderate  and  permanent  contraction,  which  is  not 
shown  by  them  when  they  are  dead,  and  which  cannot,  therefore,  be  the  re- 
sult of  elasticity,  or  of  any  simple  physical  property ;  and  the  contraction, 
instead  of  being  a  result  of  stimulation  through  the  nerves,  is  especially  ex- 
cited by  changes  of  temperature  in  the  tissue  itself.  This  endowment,  which 
seems  to  exist  in  the  greatest  amount  in  certain  forms  of  the  non-striated 
muscle,  is  called  Tonicity. — These  two  modifications  of  Muscular  Contract- 
ility require  a  separate  consideration. 

2.' — Of  Muscular  Irritability. 

575.  All  Muscular  Fibres,  which  are  in  possession  of  vital  activity,  may  be 
caused  to  contract  by  stimuli  directly  applied  to  themselves  ;  and  these  stimuli 
may  be  of  different  kinds.  The  simplest  is  the  contact  of  a  solid  substance, 
especially  if  it  be  pointed ;  thus  we  may  excite  contractions  in  Muscular 
fibres,  by  simply  touching  them  with  the  point  of  a  needle  or  of  a  scalpel. 
Most  substances  of  strong  chemical  action,  such  as  acids  and  alkalies,  will  ex- 
cite the  fibres  to  contraction,  when  directly  applied  to  themselves ;  but  the 
most  powerful  agent  of  all  is  Electricity. — If  we  thus  irritate  a  portion  of  a 
muscle  composed  of  striated  fibre,  the  biceps,  for  example,  the  fasciculus  of 
fibres  which  is  touched  will  immediately  contract,  and  that  one  only ;  and  the 
contracted  fasciculus  will  soon  relax,  without  communicating  its  movements 
to  any  other.  In  fact,  the  only  way  to  call  the  entire  muscle  into  contraction 
at  once  (since  it  would  be  impossible  to  apply  direct  irritation  to  every  fasci- 
culus), is  to  stimulate  it  through  its  nerves.  On  the  other  hand,  if  we  apply 
a  similar  irritation  to  a  portion  of  non-striated  fibre,  as  that  of  the  Intestinal 
canal,  the  fasciculus  which  is  stimulated  will  contract  less  suddenly,  but  ulti- 
mately to  a  greater  amount ;  its  relaxation  will  be  less  speedy  ;  and,  before  it 
takes  place,  other  fasciculi  in  the  neighbourhood  begin  to  contract ;  their  con- 
traction propagates  itself  to  others ;  and  so  on.  In  this  manner,  successive 
contractions  and  relaxations  may  be  produced  through  a  considerable  part  of 
the  canal,  by  a  single  prick  with  a  scalpel ;  a  sort  of  wave  of  contraction  being 
transmitted  in  the  direction  of  its  length,  and  being  followed  by  relaxation. 
Again,  in  the  Muscular  structure  of  the  Bladder  and  Uterus  (which  is  of  the 
non-striated  kind),  direct  irritation  excites  immediate  and  powerful  contractions, 
which  extend  beyond  the  fasciculus  actually  irritated,  and  produce  a  great 
degree  of  shortening ;  but  they  do  not  alternate  in  the  healthy  state  with  any 
rapid  arjd  decided  elongation.  In  the  Heart,  which  is  composed  of  a  mixture 
of  striated  and  non-striated  fibre,  the  Muscular  substance  of  a  large  part  of  the 
organ  is  thrown  into  rapid  and  energetic  contraction,  by  a  stimulus  applied  at 
any  one  point ;  and  this  contraction  is  speedily  followed  by  relaxation,  which 
is  again  succeeded  by  a  number  of  alternating  contractions  and  relaxations. 
And  in  the  muscular  tissue  of  the  middle  coat  of  the  Arteries,  which  is  of  the 
non-striated  character,  the  contraction  takes  place  rather  after  the  manner  of 
that  of  the  bladder  and  uterus ;  a  considerable  degree  of  shortening  being 
effected,  by  the  contraction  of  other  fasciculi  than  those  directly  irritated,  and 
this  shortening  not  giving  way  speedily  to  relaxation  ;  but  a  prolonged  appli- 
cation of  the  stimulus  is  often  necessary  to  produce  the  effect. 

576.  On  the  other  hand,  when  the  stimuli  which  excite  Muscular  Contrac- 
tility are  applied  to  the  nerves,  which  supply  any  muscle  composed  of  striated 
fibre  (the  Heart  only  excepted),  they  produce  a  simultaneous  contraction  in  the 
whole  muscle  ;  the  effect  of  the  stimulus  being  at  once  exerted  upon  every  part 
of  it.  The  contraction  speedily  alternates  with  relaxation,  unless  the  operation 
of  the  stimulus  be  continued, — as  when  an  electric  current  is  propagated  with- 
out intermission  along  the  nerve-trunks, — in  which  case  the  contraction  lasts  as 


440  OF  MUSCULAR  CONTRACTION. 

long  as  the  stimulus  is  continuously  applied,  but  ceases  as  soon  as  it  is  with- 
drawn. But  it  has  been  lately  stated  by  Volkmann,*  that,  if  the  electric 
stimulus  be  applied  to  the  central  organs,  from  which  the  motor  nerves  arise, 
the  muscular  contraction  continues  for  some  time  after  its  renewal.  If  this 
should  prove  to  be  a  universal  fact,  it  will  afford  a  valuable  means  of  distin- 
guishing what  are  the  real  centres  of  the  motor  nerves  of  particular  organs. 
Further,  when  the  continuous  electric  current  was  passed  through  incident  or 
excitor  nerves,  it  produced  alternating  movements  of  contraction  and  relaxa- 
tion, in  the  muscles  which  were  thus  called  into  play  by  reflex  stimulation. 
The  ordinary  actions  of  the  non-striated  fibre,  on'  the  other  hand,  are  not 
easily  excitable  by  stimuli  applied  to  their  nerves ;  indeed  many  Physiologists 
have  denied  the  possibility  of  producing  them  through  this  channel.  Positive 
evidence  to  this  effect,  however,  has  been  already  given  (§  388).  The  results 
of  Volkmann's  recent  electrical  experiments  upon  the  Heart  and  the  Intesti- 
nal Canal  are  of  much  interest.  He  found  that  neither  of  these  organs  is 
thrown  into  fixed  contraction,  when  the  continuous  electric  current  is  applied 
to  the  Brain  and  Spinal  Cord;  whence  he  concludes  that  these  organs  are  not 
the  centres  of  their  motor  nerves.  On  the  other  hand,  alternating  contrac- 
tions and  relaxations  were  produced  on  applying  the  continuous  current  to 
the  spinal  cord,  the  par  vagum,  and  the  sympathetic  nerves  ;  whence  it  may 
be  concluded  that  these  parts  contain  afferent  fibres,  which  excite  motion 
through  centres  that  can  scarcely  be  any  others  than  the  ganglia  of  the  Sym- 
pathetic system.  When  the  Heart  is  removed  from  the  body,  and  is  left  en- 
tire, it  may  be  thrown  into  a  state  of  fixed  contraction,  which  lasts  after  the 
cessation  of  the  current ;  whence  it  may  be  concluded,  that  it  contains  the 
centre  of  its  own  motor  nerves.t  These  experiments,  however,  by  no  means 
warrant  the  conclusion,  that  the  ordinary  actions  of  these  muscular  organs  are 
dependent  upon  the  agency  of  their  nerves  ;  which  is  opposed  by  a  variety  of 
evidence. 

577.  The  general  fact,  that  Muscular  Contraction  alternates  with  Relaxa- 
tion at  no  longer  intervals, — is  most  evident  in  the  rhythmical  movements  of 
the  Heart,  and  in  the  peristaltic  action  of  the  Intestinal  canal ;  since  in  those 
parts,  the  whole  or  a  large  proportion  of  the  fibres  seem  to  contract  together, 
and  then  shortly  relax.     But  it  is  probably  no  less  true,  as  formerly  stated 
(§  232),  of  the  individual  fibres  of  those  muscles,  which  are  kept  in  a  state 
of  contraction  by  a  stimulus  transmitted  through  their  nerves ;  since  none  of 
them  appear,  under  ordinary  circumstances  at  least,  to  remain  in  a  contracted 
state  for  any  length  of  time, — a  constant  interchange  of  condition  taking  place 
among  the  fibres,  some  contracting  whilst  others  are  relaxing,  and  vice  versa. 
It  is  difficult  to  speak  with  confidence,  however,  in  regard  to  the  condition  of 
the  individual  fibres  of  a  muscle,  that  is  thrown  into  a  state  of  continued 
spasmodic  contraction ;  such  as  that  produced  by  the  application  of  the  elec- 
tric current  to  the  centre  of  its  motor  nerves  (§  576).     A  state  of  this  kind  is 
often  of  considerable  duration.     Thus  the  Author  has  known  a  case  of  Hys- 
teric Trismus,  in  which  the  jaws  remained  closed  with  the  greatest  violence 
during  five  days.     Whether  the  individual  fibres,  in  such  instances,  maintain 
a  state  of  contraction  without  intermission,  or  whether  the  -contraction  of  the 
entire  muscle  is  kept  up  by  a  continual  interchange  of  the  fibres  actually  en- 
gaged, is  a  very  curious  subject  for  inquiry. 

578.  Muscles  do  not  lose  their  Irritability  immediately  on  the  general 
death  of  the  system,  which  must  be  considered  as  taking  place,  when  the  cir- 
culation ceases  without  a  power  of  renewal ;  in  cold-blooded  animals  it  is  re- 

*  Muller's  Archiv.,  1844,  No.  5,  p.  407. 

t  Op.  cit.j  and  Mr.  Paget's  Report  for  1845,  in  Brit,  and  For.  Med.  Rev.,  July,  1846. 


LOSS  OF  IRRITABILITY  BY  AFFECTIONS  OF  THE  NERVOUS  SYSTEM.         441 

tained  much  longer  after  this  period  than  in  the  higher  Vertebrata,  in  some 
of  which  it  disappears  within  an  hour.  The  muscles  of  young  animals 
generally  retain  their  irritability  for  a  longer  time  than  those -of  adults  ;  on 
the  other  hand,  those  of  Birds  lose  their  irritability  sooner  than  those  of  Mam- 
malia. Hence,  as  a  general  rule,  the  duration  of  the  irritability  is  inversely 
as  the  amount  of  respiration.  From  experiments  on  the  bodies  of  executed 
criminals,  who  were  previously  in  good  health,  Nysten  ascertained  that,  in 
the  Human  subject,  the  irritability  of  the  several  muscular  structures  departs 
in  the  following  time  and  order. — The  left  ventricle  of  the  heart  first ;  the  in- 
testinal canal  at  the  end  of  45  or  55  minutes  ;  the  urinary  bladder  nearly  at 
the  same  time ;  the  right  ventricle  after  the  lapse  of  an  hour ;  the  ossophagus 
at  the  expiration  of  an  hour  and  a  half;  the  iris  a  quarter  of  an  hour  later  ; 
the  muscles  of  Animal  life  somewhat  later ;  and  lastly,  the  auricles  of  the 
heart,  especially  the  right,  which  in  one  instance  contracted  under  the  influ- 
ence of  galvanism  16£  hours  after  death. 

579.  Muscular  Irritability  is  deadened  by  many  substances,  especially  by 
those  which  have  a  narcotic  or  sedative  action  on  the  Nervous  system.     In 
carbonic  acid  gas,  hydrogen,  carbonic  oxide,  or  sulphurous  acid  gas,  muscles 
contract  very  feebly,  or  not  at  all,  when  stimulated  ;  whilst  in  oxygen  they 
retain  their  irritability  longer  than  usual.  Narcotic  substances,  such  as  a  watery 
solution  of  opium,  when  applied  directly  to  the  muscles,  have  an  immediate 
and  powerful  effect  in  diminishing  or  even  destroying  their  irritability ;  this 
effect  is  also  produced,  though  in  a  less  powerful  degree,  by  injecting  these 
substances  into  the  blood.     In  the  same  manner,  venous  blood,  charged  with 
carbonic    acid,  and  deficient  in  oxygen,  has    the   effect   of  a  poison  upon 
muscles  ;  diminishing  their  irritability,  when  it  continues  to  circulate  through 
them,  to  such  a  degree,  that  they  sometimes  lose  it  almost  as  soon  as  the  cir- 
culation ceases,  as  is  seen  in  those  who  have  died  from  gradual  and  therefore 
prolonged  Asphyxia.     The  unfavourable  influence  of  venous  blood  is  also 
shown  in  the  Morbus  Co3ruleus ;  patients  affected  with  which  are  incapable 
of  any  considerable  muscular  exertion. — Although  most  of  the  stimuli  which 
occasion  the  contraction  of  muscles,  when  directly  applied  to  their  fibres,  ope- 
rate also  when  applied  to  their  motor  nerves,  the  same  does  not  hold  good  in 
regard  to  those  agents  which  diminish  irritability.     It  is  a  fact  of  some  im- 
portance, in  relation  to  the  disputed  question  of  the  connection  of  muscular 
irritability  with  the  nervous  system,  that  when,  by  the  application  of  narcotic 
substances  to  the  Nerves,  their  vital  properties  are  destroyed,  the  irritability 
of  the  Muscle  may  remain  for  some  time  longer, — showing  that  the  latter 
must  be  independent  of  the  former. 

580.  We  find,  however,  that  sudden  and  severe  injuries  of  the  Nervous 
Centres  have  power  to  impair,  directly  and  instantaneously,  or  even  to  destroy? 
the  Contractility  of  the  whole  Muscular  system ;  so  that  death  immediately 
results,  and  no  irritability  subsequently  remains.     It  is  in  this  manner,  that 
the  sudden  destruction  of  the  Brain  anid  Spinal  Cord,  especially  of  the  latter, 
occasions  the  immediate  cessation  of  the  Heart's  action  ;  though  they  may  be 
gradually  removed,  without  any  considerable  effect  upon  it.     Severe  concus- 
sion has  the  same  effect ;  hence  the  Syncope  which  immediately  displays  it- 
self.    It  is  sometimes  an  important  question  in  Forensic  Medicine,  whether 
an  individual,  who  has  died  from  the  effects  of  a  blow  upon  the  head,  could 
have  moved  from  the  place  where  the  blow  was  inflicted.     If  there  be  found, 
as  is  frequently  the  case,  no  sensible  disorganization  of  the  Brain,  the  death 
must  be  attributed  to  the  concussion,  and  must  have  been  in  that  case  imme- 
diate.    If,  on  the  other  hand,  effusion  of  blood  has  taken  place  within  the 
cranium,  to  any  considerable  extent,  it  is  probable  that  the  first  effects  of  the 
blow  were  in  some  degree  recovered  from,  and  that  the  circulation  was  re- 


442  OF  MUSCULAR  CONTRACTION. 

established. — It  is  not  essential,  however,  that  the  impression  should  be  prima- 
rily made  upon  the  Cerebro-Spinal  system.  The  well-known  fact  of  sudden 
death  not  unfrequently  resulting  from  a  blow  on  the  stomach,  especially  after 
a  full  meal,  without  any  perceptible  lesion  of  the  viscera,  clearly  indicates  that 
an  impression  upon  the  widely-spread  coeliac  plexus  of  Sympathetic  nerves 
(which  will  be  much  more  extensively  communicated  to  them,  when  the  sto- 
mach is  full,  than  when  it  is  empty),  may  cause  the  immediate  cessation  of 
the  Heart's  action,  in  the  same  manner  as  a  violent  injury  of  the  Brain  or 
Spinal  Cord. — Now  it  is  interesting  to  remark  that,  in  all  these  cases,  the 
whole  vitality  of  the  system  appears  to  be  destroyed  at  once ;  for  the  pro- 
cesses which  would  otherwise  succeed  the  injury,  and  which,  after  other  kinds 
of  death,  less  sudden  in  their  character,  produce  evident  changes  in  the  part 
of  the  surface  that  has  immediately  received  it,  are  here  entirely  prevented. 
An  instance  is  on  record,  in  which  a  criminal  under  sentence  of  death  deter- 
mined to  anticipate  the  law  by  self-destruction.  Having  no  other  means  of 
accomplishing  his  purpose,  he  stooped  his  head  and  ran  violently  against  the 
wall  of  his  cell ;  he  immediately  fell  dead  ;  and  no  mark  of  contusion  showed 
itself  on  his  forehead.  The  same  absence  of  the  usual  results  is  to  be  noticed 
in  the  case  of  blows  on  the  stomach.  Yet  it  is  well  known,  that  many  of  the 
ordinary  vital  processes  will  take  place  in  the  injured  parts,  after  death  of  a 
more  lingering  nature  ;  the  vitality  of  the  individual  organs  not  being  destroyed 
immediately  on  the  severance  of  the  chain  which  binds  together  the  different 
functions.  Hence  the  Irritability  of  Muscle  is  not  shown,  by  the  foregoing 
facts,  to  have  any  closer  dependence  upon  the  Nervous  system,  than  have  the 
peculiar  vital  properties  of  any  other  tissue. 

581.  The  influence  of  severe  impressions  on  the  Nervous  System,  in  di- 
minishing, where  it  does  not  altogether  destroy,  Muscular  Irritability,  is  well 
seen  in  the  effect  of  severe  injuries  affecting  vital  organs,  or  extending  over  a 
large  part  of  the  surface,  in  depressing  the  Heart's  action.     This  is  a  well- 
known  result  of  severe  burns,  especially  in  children,  whose  nervous  system 
is  more  susceptible  of  such  impressions  than  that  of  the  adult;  also  of  the 
rupture  of  the  alimentary  canal,  of  the  bladder  or  uretus ;  and  of  the  shatter- 
ing of  one  of  the  extremities,  by  violence  affecting  a  large  part  of  their  sub- 
stance.    In  all  these  cases,  the  sufferer  is  in  the  same  condition  with  one  who 
has  received  a  severe  blow  on  the  head,  that  does  not  quite  stun  him  ;  the 
shock  immediately  diminishes   the  muscular  contractility  of  the  whole  sys- 
tem ;  and  its  influence  on  the  heart,  which  of  course  manifests  itself  most 
conspicuously,  produces  a  degree  of  depression  which  is  frequently  never  re- 
covered from,  and  which,  at  any  rate,  renders  necessary  the  employment  of 
stimulants,  for  the  purpose  of  counteracting  this  very  dangerous  effect.* — Ex- 
fcessive  mental  emotion,  of  a  kind  not  in  itself  depressing,  may  occasion  the 
sudden  cessation  of  the  Heart's  action,  and  a  general  loss  of  muscular  Irrita- 
bility; and  it  is  well  known  that  muscular  power  is  greatly  diminished  by 
emotions,  which  produce  no  other  direct  action. 

582.  There  is  no  evidence  that  Muscular  Irritability  can  be  increased  by 
any  cause  operating  through  the  Nervous  system.     It  is  quite  true  that,  under 

*  The  large  quantity  of  stimulus  which  can  be  borne  even  by  children,  suffering  under 
severe  burns,  is  very  extraordinary.  There  can  be  no  doubt  that  many  lives  have  been 
saved  by  the  judicious  administration  of  them,  to  an  amount  which  would,  iH>  priori,  have 
been  judged  in  itself  fatal ;  but  that  many  more  have  been  sacrificed  to  neglect,  even  on  the 
part  of  those  whose  duty  it  is  to  watch  the  indications  with  the  closest  attention.  The  Au- 
thor's observation  leads  him  to  believe,  that  Hospital-Nurses  very  commonly  make  up  their 
minds,  that  children,  who  have  met  with  severe  burns,  must  die ;  and  that,  unless  closely 
•watched,  they  neglect  the  means  of  which  Science  and  Experience  alike  dictate  the  free  em- 
ployment. 


INFLUENCE  OF  ARTERIAL  BLOOD.  443 

the  stimulus  of  alcohol,  nitrous  oxide,  &c.,  or  of  some  purely  mental  excite- 
ment, individuals  can  perform  actions  requiring  a  degree  of  strength,  which 
they  cannot  exert  under  any  other  circumstances.  But  it  does  not  hence  fol- 
low, that  the  irritability  is  increased  ;  since  the  energy  of  the  action  may  be 
due  solely  to  the  power  of  the  stimulus  by  which  it  is  excited,  and  to  the  un- 
usual number  of  fibres  called  into  simultaneous  contraction.  It  is  well  known 
that  stimulating  agents,  which  thus  temporarily  increase  Muscular  power,  pri- 
marily excite  the  Nervous  system  ;  as  is  shown  by  the  increased  mental  acti- 
vity which  results  from  the  moderate  use  of  alcohol,  nitrous  oxide,  opium, 
&c. ;  and  it  does  not  seem  necessary,  therefore,  to  go  further  in  search  of  an 
explanation  of  their  effect  on  muscular  action. — It  is  worthy  of  remark  that, 
whilst  the  influence  of  general  depressing  causes  acting  through  the  Nervous 
System,  is  primarily  manifested  on  the  muscles  of  Organic  life,  that  of  stimu- 
lants chiefly  shows  itself  in  the  muscles  subjected  to  the  Will. 

583.  There  can  be  no  question  that,  in  the  living  body,  the  energy  of  Mus- 
cular contraction  is  determined  (other  things  being  equal),  by  the  supply  of 
Arterial  Blood,  which  the  muscle  receives.  It  is  well  known  that,  when  a 
ligature  is  applied  to  a  large  arterial  trunk  in  the  Human  subject,  there  is  not 
only  a  deficiency  of  sensibility  in  the  surface,  but  also  a  partial  or  complete 
suspension  of  muscular  power,  until  the  collateral  circulation  is  established. 
The  same  result  has  been  constantly  attained,  in  experiments  upon  the  lower 
Animals ;  the  contractility  of  the  muscle  being  impaired  or  altogether  ex- 
tinguished, when  the  flow  of  blood  into  it  was  arrested ;  and  being  recovered 
again,  when  the  supply  of  blood  was  restored.  The  influence  of  this  supply 
of  arterial  blood  is  twofold  ; — it  affords  the  materials  for  the  nutrition  of  the 
tissue ; — and  it  furnishes  (what  is  perhaps  more  immediately  necessary)  the 
supply  of  oxygen  required  for  that  metamorphosis  of  the  tissue,  which  seems 
to  be  an  essential  condition  of  the  generation  of  its  contractile  force.  As  this 
oxygen  is  taken  in  through  the  lungs,  and  as  the  greater  part  of  it  is  thrown 
off — when  united  with  carbon  into  carbonic  acid — by  the  same  channel,  we 
should  expect  to  find  a  very  close  correspondence  between  the  amount  of 
muscular  power  developed  in  an  animal,  and  the  quantity  of  oxygen  consumed 
in  its  Respiration :  and  this  is  in  reality  the  case.  We  find,  for  example,  that 
in  Birds  and  Insects,  whose  respiration  is  the  highest,  the  muscular  power  is 
greater  in  proportion  to  their  size,  than  in  any  other  animals.  In  the  Mam- 
malia, and  certain  Fishes  that  might  be  almost  called  warm-blooded,  it  is  only 
in  a  degree  inferior.  But  in  the  cold-blooded  Reptiles,  Fishes,  and  Moljusca, 
the  muscular  power  is  comparatively  feeble ;  though  even  here  we  trace  gra- 
dations, which  accord  well  with  the  relative  quantities  of  oxygen  consumed. 
But  in  proportion  to  the  feebleness  of  the  power,  do  we  usually  find  its  dura- 
tion greater  (§  578) ;  so  that  it  is  not  so  immediately  dependent  upon  the 
supply  of  oxygen,  in  cold-blooded,  as  in  warm-blooded  animals.  Thus,  it  is 
found  that  Frogs  are  still  capable  of  voluntary  movement,  after  the  heart  has 
been  cut  out ;  they  can  move  limbs  which  are  connected  with  the  trunk  by 
the  nerves  alone  :  and  that  this  power  is  not  altogether  due  to  the  blood  which 
may  remain  in  the  capillary  vessels,  is  shown  by  the  experiment  of  Muller, 
who  found  the  muscles  still  contractile,  after  he  had  expelled  all  the  blood, 
by  forcing  a  current  of  water  into  an  artery,  until  it  escaped  from  the  divided 
veins. 

584.  It  seems  probable  that  the  Muscles  of  Organic  life  are  less  dependent 
upon  a  supply  of  arterialized  blood,  than  are  those  of  Animal  life  ;  for  the 
Heart  will  continue  to  contract,  when  the  blood  in  its  vessels  is  entirely  ven- 
ous, and  when  the  circulation  in  it  has  come  to  a  stand.  Still  the  dependence 
of  its  action  upon  a  constant  supply  of  arterial  blood,  is  very  close ;  and  in  all 
animals,  however  different  the  plans  of  their  circulation,  we  find  a  provision 


444  OF  MUSCULAR  CONTRACTION. 

for  this  supply,  by  a  special  arrangement  of  the  coronary  arteries.*  That  the 
heart's  action  comes  to  an  end  much  sooner,  after  the  destruction  of  animal 
life  by  pithing,  when  the  coronary  arteries  have  been  tied,  than  when  they 
are  left  untouched,  has  been  proved  by  the  experiments  of  Mr.  Erichsen.t 
In  an  animal  that  has  been  pithed,  but  whose  heart  has  been  left  intact,  artificial 
respiration  will  easily  keep  up  its  action  for  an  hour,  or  an  hour  and  a  half. 
But  when  the  coronary  arteries  were  tied,  a  mean  of  six  experiments  gave  a 
duration,  for  the  ventricular  action,  of  only  23£  minutes  after  the  ligatures 
were  applied,  and  32«|  minutes  after  the  pithing;  and  in  no  instance  was  it 
prolonged  more  than  31  minutes  after  the  application  of  the  ligature,  or  37 
minutes  after  the  pithing.  On  the  other  hand,  when  the  aorta  was  tied,  so 
that  the  coronary  arteries  were  distended  with  blood,  the  circulation  being 
carried  on  through  them  alone,  the  right  ventricle  continued  to  act  up  to  the 
82d  minute. 

585.  There  is  a  remarkable  difference  in  the  degree  of  Irritability  in  the  two 
sides  of  the  heart,  to  which  Dr.  M.  Hall  has  directed  attention.    In  the  warm- 
blooded Vertebrata,  the  right  side  of  the  heart  will  act  on  the  stimulus  of  ven- 
ous blood  ;  whilst  the  left  side  requires  the  stimulus  of  arterial.     In  Fishes, 
on  the  other  hand,  whose  heart  corresponds  to  the  right  side  only  of  that  of 
Man,  the  whole  is  put  in  action  by  venous  blood.    In  Reptiles,  one  auricle  is 
sufficiently  stimulated  by  venous  blood,  whilst  the  other  requires  arterial ;  and 
the  ventricle  is  excited  to  action  by  a  mixed  fluid.     In  all  these  cases,  there 
must  be  a  marked  difference  in  the  properties  of  the  several  parts  ;  some  being 
sufficiently  affected   by  a  stimulus,  which  is   totally  inoperative  on  others. 
This  is  still  more  remarkably  exemplified  by  the  fact,  that  the  muscular  fibre 
of  Frogs  would  be  thrown  into  a  state  of  permanent  and  rigid  contraction 
(through  the  powerful  operation  of  its  property  of  Tonicity),  by  the  stimulus 
of  a  fluid  no  hotter  than  the  blood,  which  ordinarily  bathes  the  muscles  of 
Birds.    Now  in  those  warm-blooded  animals  which  pass  the  winter  in  a  state 
of  torpidity,  the  respiration  is  very  slow  and  imperfect,  and  the  blood  is  very 
imperfectly  arterialized.    There  must,  therefore,  be  a  change  in  the  properties 
of  the  left  ventricle,  by  which  it  becomes  capable  of  action  on  a  more  feeble 
stimulus,  thus  resembling  the  ventricle  of  Reptiles. 

a.  This  change  Dr.  M.  Hall  designates  as  an  increase  of  Irritability ;  considering  that, 
if  muscular  action  be  excited  by  a  more  feeble  stimulus,  the  property  to  which  that  action  is 
due,  must  be  itself  more  exalted.  Physiologists  have  been  so  long  accustomed,  however,  to 
consider  the  irritability  of  the  muscles  in  warm-blooded  animals  as  greater  than  that  of  cold- 
blooded, on  account  of  the  greater  energy  and  rapidity  of  their  contractions  when  excited, 
that  it  seems  undesirable  to  modify  the  term  in  the  manner  proposed  by  Dr.  Hall.  No  one 
will  assert  that  the  vitality  of  the  Muscle  is  exalted,  when  it  is  reduced  to  the  condition  of  that 
of  the  Reptile;  and,  as  Irritability  is  strictly  a  vital  property,  it  cannot  be  correctly  spoken  of 
in  that  manner.  The  general  principle,  however,  laid  down  by  Dr.  M.  Hall, — that  the  facility 
with  which  the  muscular  system  may  be  excited  to  contraction,  or  in  other  words  the  feeble- 
ness of  the  stimulus  required  for  the  purpose,  is  inversely  as  the  respiration  of  the  animal, — 
is,  no  doubt,  generally  correct. 

586.  The  doctrine,  now  generally  accepted  as  a  Physiological  truth,  that  the 
active  exercise  of  the  Contractility  of  Muscle,  is  attended  with  a  waste  or  dis- 
integration of  its  tissue,  rests  upon  a  great  variety  of  evidence.    The  increase 
of  the  demand  for  food,  occasioned  by  Muscular  activity  (§  263),  is  an  indica- 
tion that  the  nutritive  operations  are  excited  by  it ;  and  the  purpose  of  these 
can  scarcely  be  anything  else,  than  the  reparation  of  the  loss  which  the  Mus- 
cle has  sustained.    Again,  it  has  been  just  shown,  that  the  presence  of  Oxygen 
is  essential  to  the  development  of  the  Contractile  force ;  and  there  is  evidence 
that,  in  this  development,  a  chemical  change  is  effected  in  the  substance  of  the 

*  Dr.  M.  Hall's  Gulslonian  Lectures,  pp.  23,  24.  t  Medical  Gazette,  July  8,  1842. 


DISINTEGRATION  AND  NUTRITION  OF  MUSCLE.  445 

Muscle,  which  is  of  a  nature  destructive  to  its  integrity  as  an  organized  tissue. 
For,  in  the  first  place,  the  researches  of  Helmholtz,  formerly  referred  to 
(§  238,  6),  indicate  such  a  change,  from  the  comparative  results  of  Chemical 
analysis  of  the  muscle,  before  and  after  the  violent  excitement  of  its  contrac- 
tility. But  it  is  still  more  decidedly  shown,  by  the  increase  in  the  excretions, 
which  is  consequent  upon  Muscular  activity ;  and  especially  by  the  augmenta- 
tion of  the  Carbonic  acid  set  free  from  the  respiratory  organs,  and  by  that  of 
the  Urea  set  free  from  the  kidneys.  The  amount  of  the  latter,  indeed,  may  be 
regarded,  casteris  paribus,  as  an  approximative  indication  of  the  quantity  of 
Muscular  tissue  which  has  undergone  disintegration ;  being  increased  or 
diminished,  in  precise  proportion  to  the  degree  of  exertion  to  which  the 
Muscular  system  has  been  subjected. — It  cannot  but  be  regarded  as  a  probable 
inference  from  these  facts,  that  the  development  of  the  Contractile  force  is  in 
some  way  dependent  upon  the  Chemical  change,  which  seems  to  be  so  essen- 
tial a  condition  of  it ;  just  as  the  development  of  the  Electric  force  of  the 
Galvanic  battery  is  dependent  upon  the  new  chemical  arrangements,  which 
take  place  between  the  bodies  brought  to  act  upon  one  another  in  its  trough. 

587.  The  frequently-renewed  exercise  of  Muscles,  by  producing  a  deter- 
mination of  blood  towards  them,  occasions  an  increase  in  their  nutrition ;  so 
that  a  larger  amount  of  new  tissue  becomes  developed,  and  the  muscles  are 
increased  in  size  and  vigour.     This  is  true,  not  only  of  the  whole  Muscular 
system  when  equally  exercised;  but  also  of  any  particular  set  of  muscles, 
which  is  more  exercised  than  another.     Of  the  former  we  have  examples  in 
those  who  practise  a  system  of  Gymnastics  adapted  to  call  the  various  mus- 
cles alike  into  play ;  and  of  the  latter,  in  the  limbs  of  individuals  who  follow 
any  calling,  that  habitually  requires  the  exertion  of  either  pair,  to  the  partial 
exclusion  of  the  other, — as  the  arms  of  the  Smith,  or  the  legs  of  the  Opera- 
dancer.     But  this  increased  nutrition  cannot  take  place,  unless  an  adequate 
supply  of  food  be  afforded ;  and  if  the  amount  of  nutritive  material  be  insuffi- 
cient, the  result  will  be  a  progressive  diminution  in  the  size  and  power  of  the 
muscles ;  which  will  manifest  itself  the  more  rapidly,  as  the  amount  of  exer- 
tion, and  consequently  the  degree  of  waste,  are  greater.    Nor  can  it  be  effected, 
if  the  exercise  be  too  constant ;  for  it  is  during  the  intervals  of  repose  that 
the  reparation  of  the  muscular  tissue  occurs;  and  the  Muscular  system,  like 
the  Nervous  (§  294),  may  be  worn  out  by  too  constant  use.    The  more  violent 
the  action,  the  longer  is  the  period  of  subsequent  repose,  which  is  required  for 
the  reparation  of  the  tissue  :  and  the  longest  will,  of  course,  be  requisite,  when 
(as  sometimes  occurs)  the  contractility  of  the  muscle  is  so  completely  ex- 
hausted by  excessive  stimulation,  that  no  new  manifestation  of  it  can  be  ex- 
cited.    Nevertheless  it  is  certain,  that  there  must  be  a  provision  in  some  Mus- 
cles, for  the  continuance  of  their  nutrition  during  their  state  of  activity;  for  in 
no  other  way  could  the  Heart  and  Respiratory  Muscles,  which  are  in  unceas- 
ing action  during  the  whole  of  life,  be  kept  in  a  state  fit  for  the  discharge  of 

•  their  functions. 

588.  On  the  other  hand,  Muscular  Irritability,  like  the  vital  properties  of 
other  parts,  is  diminished  by  want  of  action ;  and  in  this,  as  in  other  cases,  it 
is  quite  clear  that  the  cause  of  its  loss  is  to  be  found  in  the  alteration  of  the 
nutritive  processes,  which  is  the  uniform  result  of  the  cessation  of  the  usual 
operations  of  any  part.     The  Muscular  tissue,  like  all  other  soft  organized 
substances,  has  a  constant  tendency  to  spontaneous  disintegration,  especially 
at  the  high  temperature  of  the  body  in  warm-blooded  animals  ;  and  it  is  con- 
sequently subject  to  a  slow  and  regular  waste,  quite  irrespectively  of  that  pro- 
duced by  its  vital  activity.*     Now  when  a  Muscle  or  set  of  Muscles,  in  a 

*  This  does  not  occur  with  nearly  the  same  rapidity  in  cold-blooded  Animals,  nor  in  the 
38 


446  OF  MUSCULAR  CONTRACTION. 

warm-blood  animal,  is  reduced  to  a  state  of  prolonged  inactivity,  from  what- 
ever cause,  its  supply  of  blood  is  diminished,  and  its  spontaneous  decay  is 
not  compensated  by  an  equally  active  renewal ;  so  that,  in  time,  the  characters 
of  the  structure  are  changed,  and  its  distinguishing  properties  are  no  longer 
presented.  Thus  in  persons  whose  lower  extremities  have  been  long  disused, 
the  muscles  first  become  pale  and  flabby ;  their  bulk  gradually  diminishes  ; 
their  contractile  force  progressively  decreases,  and  at  last  departs  altogether ; 
and  their  proper  structure  is  replaced  by  a  deposit  of  fat,  intermixed  with 
ordinary  fibrous  tissue,  in  which  few  or  no  characteristically-striated  muscular 
fibres  can  be  detected. 

589.  The  continual  and  evident  influence  of  the  Nervous  System  upon 
Muscular  Irritability,  has  led  many  Physiologists  to  the  belief,  that  the  latter 
is  dependent  upon  the  agency  of  the  former.  Two  views  upon  this  question 
have  been  commonly  taught,  to  both  of  which  it  seems  necessary  to  devote  a 
brief  consideration. — The  first  of  these  is,  that  Muscular  Irritability  is  derived 
from  some  influence  or  energy  communicated  from  the  Brain  or  Spinal  Cord. 

a.  This  opinion  is  evidently  analogous  to  that  which  attributes  the  vital  properties  of 
other  parts  to  the  Nervous  System  alone;  and  it  is  open  to  the  same  objection,  in  famine, 
which  has  been  applied  to  the  latter, — the  improbability  that  any  one  of  the  solid  textures  of  the 
living  body,  should  haVe  for  its  office  to  give  to  any  other  the  power  of  performing  any  vital 
action.  Moreover  it  is  inconsistent  with  the  fact  that,  in  Vegetables,  tissues  endowed  with 
a  high  degree  of  contractility  exist,  and  manifest  their  property  when  a  stimulus  is  directly 
applied  to  themselves;  which,  nevertheless,  can  haVe  no  dependence  whatever  upon  a 
nervous  system.  In  the  lower  classes  of  Animals,  too,  there  is  good  reason  to  believe,  that 
the  property  is  much  more  universally  diffused  through  their  tissues,  than  nervous  agency 
can  be.  Again,  the  action  of  the  heart  may  be  kept  up,  in  the  highest  Animals,  by  taking 
care  that  the  current  of  the  circulation  be  not  interrupted,  for  a  long  time  after  the  removal 
of  the  brain  and  spinal  cord ;  it  may  even  continue  when  completely  separated  from  the 
body,  which  shows  that  the  great  centres  of  the  ganglionic  system  cannot  supply  any  influ- 
ence necessary  to  it;  and  there  are  many  instances,  in  which  the  human  fetus  has  come  to 
its  full  size,  so  that  its  heart  must  have  regularly  acted,  without  the  existence  of  a  brain  or 
spinal  cord.  Further,  the  irritability  of  muscles  of  the  first  class  continues  for  a  long  time 
after  their  nerves  are  divided,  and  may  be  called  into  action  by  stimuli  directly  applied  to 
the  parts  themselves,  or.  to  their  nerves  below  the  section,  so  long  as  their  nutrition  is  unim- 
paired. 

6.  The  loss  of  the  irritability  of  Muscles,  within  a  few  weeks  after  the  section  of  their 
nerves, — on  which  great  stress  has  been  laid  by  Miiller  in  support  of  a  modified  form  of  the 
above  doctrine,  (it  being  maintained  by  this  distinguished  physiologist,  that,  if  muscular  irri- 
tability is  not  dependent  on  the  Brain  and  Spinal  Cord,  they  supply  some  influence  essential 
to  its  exercise,) — is  clearly  due  to  the  alteration  in  their  nutrition,  consequent  upon  their  dis- 
use. This  has  been  recently  proved  to  demonstration,  by  the  very  ingenious  experiments  of 
Dr.  J.  Reid.*  "The  spinal  nerves  were  cut  across,  as  they  lie  in  the  lower  part  of  the  spinal 
canal,  in  four  frogs ;  and  both  posterior  extremities  were  thus  insulated  from  their  nervous 
connections  with  the  spinal  cord.  The  muscles  of  one  of  the  paralyzed  limbs  were  daily 
exercised  by  a  weak  galvanic  battery ;  while  those  of  the  other  limb  were  allowed  to  remain 
quiescent.  This  was  continued  for  two  months ;  and  at  the  end  of  that  time,  the  muscles  of 
the  exercised  limb  retained  their  original  size  and  firmness  and  contracted  vigorously,  while 
those  of  the  quiescent  limb  had  shrunk  to  at  least  one-half  of  their  former  bulk,  and  pre- 
sented a  marked  contrast  with  those  of  the  exercised  limb.  The  muscles  of  the  quiescent 
limb  still  retained  their  contractility,  even  at  the  end  of  two  months ;  but  there  can  be  little 
doubt  that,  from  their  imperfect  nutrition,  and  the  progressing  changes  in  their  physical 
structure,  this  would  in  no  long  time  have  disappeared,  had  circumstances  permitted  the 
prolongation  of  the  experiment."f  This  experiment  satisfactorily  explains  the  fact  ob- 

hybernating  condition  of  certain  warm-blooded  Mammalia ;  indeed,  when  the  temperature 
of  the  body  is  reduced  to  within  a  few  degrees  of  the  freezing  point,  no  chemical  change 
seems  possible  in  muscle, — its  spontaneous  decay,  and  its  vital  activity,  being  alike  checked. 

*  Edinburgh  Monthly  Journal  of  Medical  Science,  May,  1841. 

j-  A  fact  of  an  exactly  parallel  character  has  fallen  under  the  Author's  observation,  in  a 
case  of  Hysteric  Paraplegia,  in  which  one  leg  was  occasionally  affected  with  severe  cramps. 
The  muscles  of  this  leg  suffered  much  less  diminution  of  size  and  firmness,  than  those  of 


INHERENT  IRRITABILITY  OF  MUSCULAR  FIBRE.  447 

served  by  Dr.  M.  Hall,  and  heretofore  adverted  to  (§  399),  that  in  cases  in  which  the 
cause  of  the  paralysis  is  situated  in  the  Brain,  and  in  which  the  Spinal  Cord  and  its 
nerves  are  unaffected,  the  irritability  of  the  muscles  of  the  paralyzed  part  is  not  destroyed, 
even  after  a  considerable  lapse  of  time.  For,  if  the  capability  of  performing  reflex  actions 
still  exist,  on  the  part  of  the  nervous  system,  it  is  manifest  that  the  muscles  will  be  occa-" 
sionally  excited  to  action  through  this  channel;  and  that  their  nutrition  and  vital  properties 
will  thereby  be  preserved,  as  they  were  in  Dr.  Reid's  experiments  by  the  artificial  excite- 
ment of  galvanism.  Hence  Dr.  M.  Hall's  opinion,  that  the  property  of  Muscular  contrac- 
tility is  derived  from  the  Spinal  Cord,  is  no  more  tenable  than  that  which  locates  it  in  the 
Brain. 

c.  The  loss  of  irritability  from  section  of  the  nerves,  takes  place  more  speedily  in  warm- 
blooded Vertebrata,  all  whose  vital  operations  are  performed  with  a  much  greater  activity, 
than  in  Reptiles,  and  other  cold-blooded  animals.     Dr.  Reid  found  that,  in  a  Rabbit,  a  por- 
tion of  whose  sciatic  nerve  had  been  removed  on  one  side,  the  muscles  of  that  leg  were  but 
very  feebly  excited  to  contraction  by  Galvanism,  after  the  lapse  of  seven  weeks.     The  change 
in  their  nutrition  was  evident  to  the  eye,  and  was  made  equally  apparent  by  the  balance. 
The  muscles  of  the  paralyzed  limb  were  much  smaller,  paler,  and  softer,  than  the  corre- 
sponding muscles  of  the  opposite  leg;  and  they  scarcely  weighed  more  than  half, — being 
only  170  grains,  whilst  the  others  were  327  grains.     It  was  found,  also,  that  a  perceptible 
difference  existed  in  the  size  of  the  bones  of  the  leg,  even  after  so  short  an  interval  had 
elapsed;  the  tibia  and  fibula  of  the  paralyzed  limb  weighing  only  81  grains,  whilst  those  of 
the  sound  limb  weighed  89  grains.    On  examining  the  muscular  fibres  with  the  microscope, 
it  was  found  that  those  of  the  paralyzed  leg  were  considerably  smaller  than  those  of  the 
sound  limb,  and  presented  a  somewhat  shrivelled  appearance;  and  that  the  longitudinal  and 
transverse  striae  were  much  less  distinct. 

d.  Another  equally  satisfactory  proof,  that  the  loss  of  Irritability,  which  follows  the  sever- 
ance of  the  connection  between  the  Nervous  centres  and  the  Muscle,  is  not  immediately  due 
to  the  interruption  of  any  influence  communicated  by  the  former,  has  been  given  by  the  ex- 
periments of  Dr.  J.  Reid.     He  has  proved,  that  if  the  irritability  of  Muscles  be  exhausted  by 
means,  which  have  no  tendency  to  impair  their  healthy  nutrition,  and  the  other  conditions 
favour  the  normal  performance  of  the  nutrient  processes,  the  irritability  is  restored,  and  re- 
mains for  some  time.     His  first  experiments  were  on  cold-blooded  animals,  and  they  would 
in  themselves  be  sufficiently  satisfactory;  but  he  has  since  repeated  them  in  the  Rabbit,  and 
established  the  fact  beyond  all  doubt.*     "  The   sciatic  nerve  was  divided  in  the   Rabbit, 
and  a  portion  of  it  removed.     One  wire  from  two  galvanic  batteries  consisting  of  thirty 
pairs  of  plates,  was  applied  over  the  course  of  the  nerve ;  and  the  other  wire  was  applied 
over  the  foot,  which   was  kept  moist,  until  the  muscles  had  ceased  to  contract.     Three 
days  after  this,  a  weaker  battery  was  used,  and  the  muscles  of  the  limb  had  recovered 
their  contractility,  and  contracted  powerfully.     The   more  powerful  battery  was  used  as 
before,  until  the  muscles  had  ceased  to  respond  to  the  excitement ;  and  three  days  after 
this,  they  had  again  recovered  their  contractility."     It  seems  scarcely  possible  to  draw  any 
other  inference  from  these  experiments,  than  that  Irritability  is  a  property  inherent  in  Mus- 
cular tissue,  and  that  the  agency  of  the  Nervous  system  upon  it  is  merely  to  call  it  into 
active  operation. 

590.  The  second  doctrine  referred  to,  as  having  been  taught  by  some  Phy- 
siologists, is,  that  Muscles,  though  not  dependent  on  nerves  for  their  peculiar 
vital  power,  are  yet  dependent  upon  them  for  the  exercise  of  that  power; — 
all  stimuli,  which  excite  muscles  to  contraction,  operating  first  on  the  nervous 
filaments  which  enter  muscles,  and  through  them  on  the  muscular  fibres. 

a.  The  facts  which  have  been  already  stated,  in  regard  to  the  ordinary  action  of  the  Mus- 
cles of  Organic  life,  furnish  a  sufficient  answer  to  this  hypothesis.  It  is  with  great  difficulty 
that  these  can  be  made  to  display  their  irritability,  by  any  stimuli  applied  to  their  nerves; 
whilst  they  manifest  it  strongly,  when  the  stimulus  is  directly  applied  to  themselves.  Even 
in  the  Muscles  of  Animal  life,  individual  fasciculi  may  be  thrown  into  action  in  the  same 
manner;  although  the  entire  mass  cannot  be  put  into  combined  operation,  except  by  a  stimu- 
lus simultaneously  communicated  to  the  whole,  which  the  nerve  affords  the  readiest  means 
of  effecting.  Perhaps  the  most  satisfactory  disproof  of  it,  however,  is  to  be  found  in  the  ob-' 


the  other;  so  that  there  was  a  difference  of  more  than  an  inch  in  the  circumference  of  the 
limbs.  But  since  the  paraplegia  has  been  recovered  from,  voluntary  power  having  been  es- 
tablished in  both  limbs,  and  the  muscles  of  both  having  been  exercised  in  the  same  degree, 
they  have  greatly  improved  in  size  and  firmness,  and  there  is  no  longer  any  perceptible  dif- 
ference between  them.  *  Loc.  cit. 


448  OF  MUSCULAR  CONTRACTION. 

servation  of  Mr.  Bowman  already  cited  (§231),  that  a  single  fibre,  completely  isolated  from 
all  its  connections,  may  be  seen  with  the  microscope  to  pass  into  a  state  of  contraction,  under 
the  influence  of  direct  irritation.  Further,  it  has  been  experimentally  ascertained,  that  there 
are  some  chemical  stimuli,  which  will  produce  the  contraction  of  muscles  when  directly  ap- 
plied to  them,  but  of  which  the  influence  cannot  be  transmitted  through  the  nerves ;  this  is 
especially  the  case  with  regard  to  acids. 

591.  When  all  these  considerations  are  allowed  their  due  weight,  we  can 
scarcely  do  otherwise  than  acquiesce  fully  in  the  doctrine  of  Haller,  which 
involves  no  hypothesis,  and  which  is  perfectly  conformable  to  the  analogy  of 
other  departments  of  Physiology.     He  regarded  every  part  of  the  body  which 
is  endowed  with  Irritability,  as  possessing  that  property  in  and  by  itself;  but 
considered  that  the  property  is  subjected  to  excitement  and  control  from  the 
Nervous  System,  the  agency  of  which  is  one  of  the  stimuli  that  can  call  it 
into  operation. — It  may  be  desirable  briefly  to  recapitulate  the  facts,  by  which 
this  doctrine  is  supported.    1.  The  existence  in  Vegetables  of  irritable  tissues, 
which  are  excited  to  contraction  by  stimuli  directly  applied  to  themselves, 
and  which  can  be  in  no  way  dependent  upon,  or  influenced  by,  a  Nervous 
system.     2.  The  existence  in  Animals  of  a  form  of  Muscular  tissue,  which 
is  especially  connected  with  the  maintenance  of  the  Organic  functions,  and 
which  is  much  more  readily  excited  to  action  by  direct  stimulation,  than  it  is 
by  Nervous  agency.     3.  The  fact  that,  by  the  agency  of  these,  the  Organic 
functions  may  go  on  (as  long  as  their  other  requisite  conditions  are  supplied) 
after  the  removal  of  the  nervous  centres,  and  when  none  were  ever  present ; 
rendering  it  next  to  certain,  that  their  ordinary  operations  are  not  dependent 
upon  any  stimuli  received  through  the  nerves,  but  upon  those  directly  applied 
to  themselves.     4.  The  persistence  of  irritability  in  muscles,  for  some  time 
after  the  nerves  have  ceased  to  be  able  to  convey  them  the  effects  of  stimuli ; 
this  is  constantly  seen  in  regard  to  the  Sympathetic  system  of  nerves,  and 
the  muscles  of  Organic  life  upon  which  they  operate;   and   it  may  also  be 
shown  to  occur  with  respect  to  the  Cerebro-Spinal  system,  and  the  muscles 
of  Animal  life,  by  the  agency  of  narcotics.     5.  The  persistence  of  irritability 
in  the   muscles,  after  their  complete   isolation  from   the  nervous  centres,  so 
long  as  their  nutrition  is  unimpaired;  and  the  effects  of  frequent  exercise,  in 
preventing  the  impairment  of  the  nutrition  and  the  loss  of  irritability.     6. 
The  recovery  of  the  irritability  of  muscles,  when  isolated  from  the  nervous 
centres,  after  it  has  been  exhausted  by  repeated  stimulation;  this  also  depends 
upon  the  healthy  performance  of  the  nutritive  actions.     7.  The  contraction 
of  muscular  fibre  under  the  microscope,  when  completely  isolated  from  all 
other  tissues. — In  the  words  of  Dr.  Alison,  then,  "  the  only  ascertained  final 
cause  of  all  endowments  bestowed  on  Nerves  in  relation  to  Muscles,  in  the 
living  body,  appears  to  be,  not  to  make  Muscles  irritable,  but  to  subject  their 
irritability,  in  different  ways,  to  the  dominion  of  the  acts  and  feelings  of  the 
Mind," — to  its  volitions,  emotions,  and  instinctive  determinations. 

592.  A  curious  question  has  been  lately  raised,  the  decision  on  which  is  of 
some  importance  in  our  determination  of  the  nature  of  the  force,  by  which 
the  contraction  of  muscles  is  occasioned.     This  is,— whether  the  power  of  a 
muscle  is  greater  or  less  at  different  degrees  of  contraction,  the  same  stimulus 
being  applied.     This  seems  to  have  been  determined,  by  the  ingeniously-de- 
vised experiments  of  Schwann.*     He  contrived  an  apparatus,  which  should 
Accurately  measure  the  length  of  the  muscle,  and,  at  the  same  time,  the  weight 
which  it  would  balance  by  its  contraction.     Having  caused  the  muscle  of  a 
Frog  to  shorten  to  its  extreme  point,  by  the  stimulus  of  galvanism  applied  to 
the  nerve,  so  that  no  further  stimulation  could  lift  a  weight  placed  in  the  oppo- 
site scale,  he  allowed  the  muscle  to  relax  until  it  was  extended  to  a  certain 

*  Miillefs  Physiology,  p.  903. 


TONIC  CONTRACTION  OF  MUSCLES.  449 

point,  and  then  ascertained  the  weight  which  would  balance  its  power.  The 
same  was  several  times  repeated,  as  in  the  following  manner :— The  length  of 
the  muscle  in  its  extreme  state  of  contraction,  at  which  no  additional  force 
could  be  exerted  by  it,  being  represented  by  14,  it  was  found  that,  when  it 
had  been  extended  to  17,  it  would  balance  a  weight  of  60;  when  its  length 
increased  to  19'6,  it  would  balance  a  weight  of  120;  and  at  22*5,  it  would 
balance  180.  In  another  experiment,  the  muscle  at  13*5,  balanced  0;  at  18*8, 
it  balanced  100 ;  and  at  23*4,  it  balanced  200.  Hence  it  appears  that  a  uni- 
form increase  of  force  corresponds  with  a  nearly  uniform  increase  in  the 
length  of  the  muscle ;  or,  in  other  words,  that  when  the  muscle  is  nearly  at 
its  full  length,  its  contractile  power  is  the  greatest.  In  later  experiments  upon 
the  same  muscle,  this  uniform  ratio  seemed  to  be  departed  from ;  but,  by 
comparing  the  results  in  a  considerable  number  of  instances,  it  was  constantly 
found  that,  in  those  experiments  which  were  performed  the  soonest  after  the 
preparation  of  the  frog,  and  in  which,  therefore,  the  normal  conditions  of  the 
system  were  the  least  disturbed,  the  ratio  was  very  closely  maintained.  It 
has  been  ascertained  by  Valentin,  on  repeating  these  experiments,  that,  by 
repeated  equal  irritations,  the  strength  of  the  muscles  in  beheaded  frogs  de- 
creases in  a  regular  and  corresponding  ratio  ;  losing  the  same  amount  in  each 
successive  period  of  time.  He  also  found  that,  when  all  the  Irritability  has 
ceased,  the  muscles  tear  with  a  far  less  weight,  than  they  were  previously 
able,  when  galvanized,  to  draw. 

a.  It  has  been  inferred  by  Miiller,  from  Schwann's  experiments,  that  the  power  which 
causes  the  contraction  of  a  Muscle,  must  be  very  different  in  its  character,  from  any  of  the 
forces  of  attraction  known  to  us ;  since  these  all  increase  in  energy  as  the  attracted  parts  ap- 
proach each  other,  in  the  inverse  ratio  of  the  square  of  the  distance  ;  so  that  the  power  of  a 
Muscle,  if  operated  on  by  any  of  these,  ought  to  increase,  instead  of  regularly  diminishing, 
with  its  degree  of  contraction.  But  it  is  to  be  remembered  that,  as  the  observations  of  Mr. 
Bowman  have  clearly  shown,  there  must  be  a  considerable  displacement  of  the  constituents 
of  every  fibre  during  contraction  (§  231);  so  that  it  is  easy  to  understand  that,  the  greater 
the  contraction,  the  more  difficult  must  any  further  contraction  become.  If,  between  a  mag- 
net and  a  piece  of  iron  attracted  by  it,  there  were  interposed  a  spongy  elastic  tissue,  the  iron 
would  cease  to  approach  the  magnet  at  a  point,  at  which  the  attraction  of  the  magnet  would 
be  balanced  by  the  force,  needed  to  compress  still  further  the  intermediate  substance. 

3.— -Of  Muscular  Tonicity. 

593.  We  have  now  to  consider  the  other  form  of  Contractility,  which  pro- 
duces a  constant  tendency  to  contraction  (varying,  however,  as  to  its  degree) 
in  the  Muscular  fibre ;  but  which  is  so  far  different  from  simple  Elasticity, 
that  it  abates  after  death,  before  decomposition  has  taken  place.  This  Toni- 
city is  to  be  distinguished  from  the  Muscular  Tension,  which  is  the  result  of 
the  reflex  operation  of  the  nervous  centres  (§  398) ;  being  manifested  as  well 
when  the  muscle  is  altogether  removed  from  nervous  influence,  as  when  sub- 
jected to  it,  and  being,  like  Irritability,  an  inherent  property  of  the  tissue  itself, 
the  presence  of  which  is  characteristic  of  its  living  state.  It  manifests  itself 
in  the  retraction  which  takes  place  in  the  ends  of  a  living  muscle,  when  it  is 
divided  (as  is  seen  in  amputation) ;  this  retraction  being  permanent,  and 
greater  than  that  of  a  dead  muscle.  But  its  effects  are  much  more  remarkable 
in  the  non-striated,  than  in  the  striated  form  of  Muscular  Fibre ;  and  are  par- 
ticularly evident  in  the  contractile  coat  of  the  Arteries,  causing  the  almost 
entire  obliteration  of  their  tubes,  when  they  are  no  longer  distended  with 
blood.  The  disposition  to  tonic  contraction  is  increased  by  any  considerable 
change  of  temperature ;  the  power  of  Heat  is  well  seen  in  the  following  ex- 
periments of  John  Hunter's : — "  As  soon  as  the  skin  could  be  removed  from 
a  sheep  that  was  newly  killed,  a  square  piece  of  muscle  was  cut  off,  which 

38* 


450  OF  MUSCULAR  CONTRACTION. 

was  afterwards  divided  into  three  pieces,  in  the  direction  of  the  fibres ;  each 
piece  was  put  into  a  Basin  of  water,  the  water  in  each  basin  being  of  different 
temperatures,  viz.,  one  about  125°,  about  27°  warmer  than  the  animal;  an- 
other 98°,  the  heat  of  the  animal;  and  the  third  55°,  about  43°  colder  than 
the  animal.  The  muscle  in  the  water  heated  to  125°  contracted  directly,  so 
as  to  be  half  an  inch  shorter  than  the  other  two,  and  was  hard  and  stiff.  The 
muscle  in  the  water  heated  to  98°  after  six  minutes  began  to  contract  and 
grow  stiff;  and  at  the  end  of  twenty  minutes  it  was  nearly,  though  not  quite, 
as  short  and  hard  as  the  above.  The  muscle  in  the  water  heated  to  55°  after 
fifteen  minutes,  began  to  shorten  and  grow  hard ;  after  twenty  minutes  it  was 
nearly  as  short  and  as  hard  as  that  in  the  water  heated  to  98°.  At  the  end 
of  twenty-four  hours,  they  were  all  found  to  be  of  the  same  length  and  stiff- 
ness."* The  agency  of  Heat  in  producing  this  contraction  is  also  remarkably 
shown  in  the  fact,  that  if  a  Frog  be  immersed  in  water  of  the  temperature  of 
110°,  the  muscles  of  its  body  and  limbs  will  be  thrown  into  a  state  of  perma- 
nent and  rigid  contraction. — But  it  would  seem  that  these  effects  are  chiefly, 
if  not  entirely,  exerted  upon  the  striated  form  of  Muscular  fibre  ;  and  that  the 
tonicity  of  the  non-striated  fibre  is  called  into  play  by  Cold,  rather  than  by 
heat.  For  if  a  Tadpole  or  Frog  be  immersed  in  water,  the  temperature  of 
which  is  gradually  raised,  until  this  state  of  contraction  comes  on,  the  Heart 
will  be  found  to  continue  pulsating  for  many  hours  afterwards,  not  being 
affected  by  the  heat.  On  the  other  hand,  if  an  artery  in  a  living  warm-blooded 
animal  be  exposed  to  cold  air  for  some  time,  the  lowering  of  its  temperature 
occasions  its  contraction  to  such  an  extent,  that  its  cavity  becomes  almost 
obliterated.  The  influence  of  warmth  in  diminishing,  and  of  cold  in  increas- 
ing, the  tonicity  of  the  arterial  system,  will  be  adverted  to  hereafter  (Chap, 
xii.,  Sect.  3). 

594.  The  distinctness  of  the  Tonicity  of  Muscles  from  their  Irritability,  is 
further  shown  by  the  fact  that  the  former  commonly  survives  the  latter  ;  and 
that  it  is  not  destroyed  by  treatment,  which  occasions  the  complete  departure 
of  the  Irritability.     The  first  of  these  statements  finds  its  proof  in  the  pheno- 
mena of  the  Rigor  Mortis,  presently  to  be  adverted  to.     Of  the  latter,  the  fol- 
lowing remarkable  experiment  of  John  Hunter's  is  an  ample  demonstration :— 
"  From  a  straight  muscle  in  a  bullock's  neck,  a  portion,  three  inches  in  length, 
was  taken  out  immediately  after  the  animal  had  been  knocked  down,  and  was 
exposed  between  two  pieces  of  lead,  to  a  cold  below  0°,  for  fourteen  minutes  ; 
at  the  end  of  this  time  it  was  found  to  be  frozen  exceedingly  hard,  was  be- 
come white,  and  was  now  only  two  inches  long;  it  was  thawed  gradually,  and 
in  about  six  hours  after  thawing,  it  contracted  so  as  only  to  measure  one  inch 
in  length ;  but  irritation  did  not  produce  any  sensible  motion  in  the  fibres. 
Here,  then,  were  the  juices  of  muscles  frozen,  so  as  to  prevent  all  power  of 
contraction  in  their  fibres,  without  destroying  their  life ;  for  when  thawed, 
they  showed  the  same  life  which  they  had  before ;  this  is  exactly  similar  to 
the  freezing  of  blood  too  fast  for  its  coagulation,  which,  when  thawed,  does 
afterwards  coagulate,  as  it  depends  in  each  on  the  life  of  the  part  not  being 
destroyed. "t 

595.  The  Rigor  Mortis,  or  death-stiffening  of  the  muscles,  is  probably  to 
be  regarded  as  the  final  manifestation  of  this  property ;  occurring  after  all  the 
Irritability  of  the  muscles  has  departed,  but  before  any  putrefactive  change 
has  commenced.     This  phenomenon  is  rarely  absent ;  though  it  may  be  so 
slight,  and  may  last  for  so  short  a  time,  as  to  escape  observation.     The  period 
which  elapses  before  its  commencement,  is  as  variable  as  its  duration  ;  and 

*  General  Principles  of  the  Blood,  in  Hunter's  Works,  Vol.  iii.,  p.  110. 
f  Op.  tit,  p.  109. 


RIGOR  MORTIS.  451 

both  appear  to  be  in  some  degree  dependent  upon  the  vital  condition  of  the 
body  at  the  time  of  death.  When  the  fatal  termination  has  supervened  on  slow 
and  wasting  disease,  occasioning  great  general  depression  of  the  vital  powers, 
the  rigidity  usually  developes  itself  very  early,  and  lasts  for  a  short  time.  In 
diseases  which  powerfully  affect  the  nervous  energy,  such  as  Typhus,  this  is 
often  the  case  ;  even  though  they  have  not  been  of  long  duration.  Thus, 
after  death  from  Typhus,  the  limbs  have  been  sometimes  known  to  stiffen 
within  fifteen  or  twenty  minutes.  The  same  is  observed  in  infants  and  in  old 
people.  On  the  other  hand,  where  the  general  energy  has  been  retained  up 
to  a  short  period  before  death,  the  rigidity  is  much  later  in  coming  on,  and 
lasts  longer ;  this  happens,  for  example,  in  many  cases  of  Asphyxia  and  Poi- 
soning, in  which  it  has  been  said  not  to  occur  at  all.  The  commencement  of 
the  rigidity,  however,  is  not  usually  prolonged  much  beyond  seven  hours ; 
but  twenty  or  even  thirty  hours  may  elapse,  before  it  shows  itself.  Its  gene- 
ral duration  is  from  twenty-four  to  thirty-six  hours  ;  but  it  may  pass  off  much 
more  rapidly  ;  or  it  may  be  prolonged  through  several  days.  An  attempt  has 
been  made  to  connect  it  with  the  lowering  of  the  temperature  of  the  dead 
body  ;  but  with  this  it  does  not  seem  to  have  any  relation.  It  occurs  in  cold- 
blooded Vertebrata,  and  even  in  Invertebrata,  as  well  as  in  warm-blooded  ani- 
mals ;  and  it  has  frequently  been  noticed  to  commence  in  the  latter,  long  be- 
fore the  heat  has  entirely  departed  from  the  body.  Moreover,  it  appears  first 
upon  the  trunk,  which  is  the  region  last  deserted  by  the  caloric.  It  first  affects 
the  neck  and  lower  jaw,  and  seems  gradually  to  travel  downwards ;  but  ac- 
cording to  some  observers,  the  lower  extremities  are  stiffened  before  the  upper. 
In  its  departure,  which  is  immediately  followed  by  decomposition,  the  same 
order  is  observed.  It  affects  all  the  muscles  nearly  alike  ;  but  the  flexors  are 
usually  more  contracted  than  the  extensors,  so  that  the  fingers  are  somewhat 
flexed  on  the  palm,  and  the  fore-arm  on  the  arm ;  and  the  lower  jaw,  if  pre- 
viously drooping,  is  commonly  drawn  firmly  against  the  upper.  It  is  remark- 
able, that  it  is  equally  intense  in  muscles  which  have  been  paralyzed  by  He- 
miplegia;  provided  that  no  considerable  change  has  taken  place  in  their 
nutrition.  When  very  strong,  it  renders  the  muscles  prominent,  as  in  volun- 
tary contraction. 

596.  The  ordinary  Irritability  of  the  muscles  appears  to  be  almost  invaria- 
bly lost,  or  greatly  diminished,  before  the  Rigor  Mortis  commences.  This 
statement  holds  good  in  regard  to  animals  of  different  classes,  as  well  as  with 
respect  to  Man  under  various  conditions.  Thus,  in  Birds,  whose  muscles 
most  speedily  lose  their  contractility,  the  cadaveric  rigidity  is  most  quickly 
exhibited  ;  whilst  in  Reptiles  it  is  much  longer  in  commencing,  the  irritability 
of  the  muscles  being  more  persistent.  The  interval  between  the  cessation  of 
the  Irritability  and  the  accession  of  the  Rigidity,  is  sometimes  very  consider- 
able ;  and  in  such  cases,  the  rigidity,  when  it  does  occur,  is  usually  very  de- 
cided and  prolonged. — An  attempt  has  been  made  to  show  a  correspondence 
between  the  rigor  mortis,  and  the  coagulation  of  the  blood  in  the  vessels ;  and 
there  is  certainly  evidence  enough  to  make  it  appear,  that  some  analogy  exists 
between  these  two  actions,  though  they  are  far  from  being  identical.  After 
those  forms  of  death  in  which  the  blood  does  not  coagulate,  or  coagulates 
feebly,  the  rigidity  commonly  manifests  itself  least ;  but  this  is  by  no  means 
an  invariable  rule.  It  seems  probable  that,  as  the  coagulation  of  the  blood 
will  be  shown  to  be  the  last  act  of  its  vitality,  so  the  stiffening  of  the  muscles 
is  the  expiring  effort  of  theirs. 

a.  It  is  necessary  to  bear  in  mind,  when  the  phenomena  of  cadaveric  rigidity  are  brought 
into  question  in  juridical  investigations,  that  a  state  at  first  sight  corresponding  to  it  may 
supervene  immediately  upon  death,  from  some  peculiar  condition  of  the  nervous  and  muscular 
systems  at  the  moment.  This  has  been  observed  in  some  cases  of  Asphyxia;  but  chiefly 
when  death  has  resulted  from  apoplexy  following  chronic  ramottissement  of  the  brain  or  spinal 


452  OF  MUSCULAR  CONTRACTILITY. 

cord.  This  contraction,  which  is  obviously  of  a  tetanic  character,  ceases  after  a  few  hours, 
and  is  then  succeeded  by  a  state  of  flexibility,  after  which  the  ordinary  rigidity  supervenes. 
The  following  case  illustrates  the  nature  of  the  inquiries,  to  which  this  condition  may  give 
rise.*  The  body  of  a  man  was  found  in  a  ditch,  with  the  trunk  and  limbs  in  such  a  relative 
position,  as  could  only  be  maintained  by  the  stiffness  of  the  articulations.  This  stiffness  must 
have*  come  on  at  the  very  moment  when  the  body  took  that  position ;  unless  it  could  be 
imagined  that  the  body  had  been  supported  by  the  alleged  murderers,  until  the  joints  were 
locked  by  cadaveric  stiffness.  A  post-mortem  examination  showed,  that  there  was  no  neces- 
sity for  this  supposition, — obviously  a  very  improbable  one  in  itself; — by  affording  sufficient 
evidence,  that  apoplexy,  resulting  from  chronic  disease,  was  the  cause  of  death.  A  case 
occurred  a  few  years  since  in  Scotland,  in  which  the  same  plea  was  raised.  The  body  was 
found  in  a  position  in  which  it  could  have  only  been  retained  by  rigidity  of  the  joints ;  and 
it  was  pleaded  on  the  part  of  the  prisoner,  that  death  had  been  natural,  and  had  resulted 
from  fracture  of  the  processus  dentatus,  causing  sudden  pressure  upon  the  spinal  cord,  whence 
the  spasmodic  rigidity  would  naturally  result.  Proof  was  deficient,  however,  as  to  the 
existence  of  this  lesion  before  death ;  and  the  position  of  the  body  rather  resembled  that  into 
which  it  might  have  been  forced  during  the  rigidity,  than  that  in  which  it  would  probably 
have  been  at  the  moment  of  death.  There  were  also  marks  of  violence,  and  many  other 
suspicious  circumstances;  but  the  prisoner  was  acquitted,  chiefly  from  want  of  evidence 
against  him.  What  seemed  to  indicate  that  the  rigidity  was  of  the  ordinary  cadaveric  nature, 
was,  that  there  was  no  evidence  of  the  body  having  become  flexible  and  again  stiffened ;  as 
it  would  probably  have  done,  had  the  rigidity  been  of  the  spasmodic  character. 

597.  As  the  property  of  Tonicity  manifests  itself  most  decidedly  in  the  non- 
striated  muscles  in  the  living  body,  so  do  we  find  this  post-mortem  contraction 
most  remarkable  in  them.    As  soon  as  the  muscular  walls  of  the  several  cavi- 
ties lose  their  irritability,  they  begin  to   contract  firmly  upon  their  contents, 
and  thus  become  stiff  and  firm,  though  they  were  previously  flaccid.     In  this 
manner  the  ventricles  of  the  heart,  which   are  the  first  parts  to  lose  their 
irritability,  become  rigid  and  contracted  within  an  hour  or  two  after  death ; 
and  usually  remain  in  that   state  for  ten  or   twelve   hours,  sometimes  for 
twenty-four  or  thirty-six,  then   again  becoming  relaxed  and  flaccid.     This 
rigid  contracted  state  of  the  heart,  in  which  the  walls  are  thickened  and  the 
cavities   diminished,  was   formerly  supposed  to  be  a  result  of  disease,  and 
was  termed  concentric  hypertrophy;  but  it  is  now  known,  from  the  inquiries 
of  Mr.  Paget,  to  be  the  natural  condition  of  the  organ,  at  the  period  when  the 
rigor  mortis  occurs  in  it. — The  contraction  of  the  arterial  tubes  is  so  great,  as 
to  produce  for  the  time  a  great  diminution  in  their  calibre ;  and  this  doubtless 
contributes  to  the  passage  of  the  blood  from  the  arterial  into  the  venous  sys- 
tem, which  almost  invariably  takes  place  within  a  few  hours  after  death.    The 
arteries,  then  enlarge  again,  and  become  quite  flaccid,  their  tubes  being  emptied 
of  their  previous  contents  ;  and  it  was  from  this  circumstance,  that  the  ancient 
Physiologists  were  led  to  imagine,  that  the  arteries  are  not  destined  to  carry 
blood,  but  air. 

4. — Energy  and  Sapidity  of  Muscular  Contraction. 

598.  The  energy  of  Muscular  contraction  is  of  course  to  be  most  remarkably 
observed  in  those  instances  in  which  the  continual  exercise  of  particular  parts 
has  occasioned  an  increased  determination  of  blood  towards  them,  and  in  con- 
sequence a  permanent  augmentation  in  their  bulk.     This  has  been  the  case, 
for  example,  with  persons  who  have  gained  their  livelihood  by  exhibiting 
feats  of  strength.    Much  will,  of  course,  depend  on  the  mechanically-advantage- 
ous application  of  muscular  power ;  and  in  this  mariner,  effects  may  be  pro- 
duced, even  by  persons  of  ordinary  strength,  which  would  not  have  been 
thought  credible.    In  lifting  a  heavy  weight  in  each  hand,  for  example,  a  per- 
son who  keeps  his  back  perfectly  rigid,  so  as  to  throw  the  pressure  vertically 
upon  the  pelvis,  and  only  uses  the  powerful  extensors  of  the  thigh  and  calf, 
by  straightening  the  knees  (previously  somewhat  flexed),  and  bringing  the  leg 
to  a  right  angle  with  the  foot,  will  have  a  great  advantage  over  one  who  uses 

*  Annales  d'Hygiene,  torn.  vii. 


ENERGY  AND  RAPIDITY  OF  MUSCULAR  CONTRACTION.  453 

his  lumbar  muscles  for  the  purpose.  A  still  greater  advantage  will  be  gained, 
by  throwing  the  weight  more  directly  upon  the  loins,  by  means  of  a  sort  of 
girdle,  shaped  so  as  to  rest  upon  the  top  of  the  sacrum  and  the  ridges  of  the 
ilia ;  and  by  pressing  with  the  hands  upon  a  frame,  so  arranged  as  to  bring 
the  muscles  of  the  arms  to  the  assistance  of  those  of  the  legs :  in  this  manner, 
a  single  Man  of  ordinary  strength  may  raise  a  weight  of  2000  Ibs. ;  whilst  few 
who  are  unaccustomed  to  such  exertions,  can  lift  more  than  300  Ibs.  in  the 
ordinary  mode.  A  man  of  great  natural  strength,  however,  has  been  known 
to  lift  800  Ibs.  with  his  hands ;  and  the  same  individual  performed  several 
other  curious  feats  of  strength,  which  seem  deserving  of  being  here  noticed. 
"  1.  By  the  strength  of  his  fingers,  he  rolled  up  a  very  large  and  strong  pewter 
dish.  2.  He  broke  several  short  and  strong  pieces  of  tobacco-pipe,  with  the 
force  of  his  middle  finger,  having  laid  them  on  the  first  and  third  finger.  3. 
Having  thrust  in  under  his  garter  the  bowl  of  a  strong  tobacco-pipe,  his  legs 
being  bent,  he  broke  it  to  pieces  by  the  tendons  of  his  hams,  without  altering 
the  bending  of  the  knee.  4.  He  broke  such  another  bowl  between  his  first 
and  second  fingers,  by  pressing  them  together  sideways.  5.  He  lifted  a  table 
six  feet  long,  which  had  half  a  hundred-weight  hanging  at  the  end  of  it,  with 
his  teeth,  and  held  it  in  that  position  for  a  considerable  time.  It  is  true,  the 
feet  of  the  table  rested  against  his  knees ;  but,  as  the  length  of  the  table  was 
much  greater  than  its  height,  that  performance  required  a  great  strength  to  be 
exerted  by  the  muscles  of  his  loins,  neck,  and  jaws.  6.  He  took  an  iron 
kitchen  poker,  about  a  yard  long,  and  three  inches  in  circumference,  and,  hold- 
ing it  in  his  right  hand,  he  struck  it  on  his  bare  left  arm  between  the  elbow 
and  the  wrist,  till  he  bent  the  poker  nearly  to  a  right  angle.  7.  He  took  such 
another  poker,  and,  holding  the  ends  of  it  in  his  hands,  and  the  middle  of  it 
against  the  back  of  his  neck,  he  brought  both  ends  of  it  together  before  him  ; 
and,  what  was  yet  more  difficult,  he  pulled  it  straight  again."*  Haller  men- 
tions an  instance  of  a  man,  who  could  raise  a  weight  of  300  Ibs.  by  the  action 
of  the  elevator  muscles  of  his  jaw:  and  that  of  a  slender  girl,  affected  with 
tetanic  spasm,  in  whom  the  extensor  muscles  of  the  back,  in  the  state  of  tonic 
contraction  or  opisthotonos,  resisted  a  weight  of  800  Ibs.,  laid  on  the  abdomen 
with  the  absurd  intention  of  straightening  the  body.  It  is  to  be  recollected, 
that  the  mechanical  application  of  the  power  developed  by  muscular  contrac- 
tion, to  the  movement  of  the  body,  is  very  commonly  disadvantageous  as  re- 
gards force;  being  designed  to  cause  the  part  moved  to  pass  over  a  much 
greater  space,  than  that  through  which  the  muscle  contracts.  Thus  the  tem- 
poral muscle  is  attached  to  the  lower  jaw,  at  about  one-third  of  the  distance 
between  the  condyle  and  the  incisors ;  so  that  a  shortening  of  the  muscle  to 
the  amount  of  half  an  inch,  will  draw  up  the  front  of  the  jaw  through  an  inch 
and  a  half;  but  a  power  of  900  Ibs.  applied  by  the  muscle,  would  be  required 
to  raise  300  Ibs.  bearing  on  the  incisors.  In  the  case  of  the  forearm  and  leg, 
the  disproportion  is  much  greater ;  the  points  of  attachment  of  the  muscles, 
by  which  thfe  knee  and  elbow-joints  are  flexed  and  extended,  being  much 
closer  to  the  fulcrum,  in  comparison  with  the  distance  of  the  points  on  which 
the  resistance  bears. 

599.  The  energy  of  muscular  contraction  appears  to  be  greater  in  Insects, 
in  proportion  to  their  size,  than  it  is  in  any  other  animals.  Thus  a  Flea  has 
been  known  to  leap  sixty  times  its  own  length,  and  to  move  as  many  times 
its  own  weight.  The  short-limbed  Beetles,  however,  which  inhabit  the 
ground,  manifest  the  greatest  degree  of  muscular  power.  The  Lucanus  cer- 
vi&  (Stag  Beetle)  has  been  known  to  gnaw  a  hole  of  an  inch  diameter,  in  the 
side  of  an  iron  canister  in  which  it  had  been  confined.  The  Geotrupes  ster- 
corarius  (Dung  or  shard-born  Beetle)  can  support  uninjured,  and  even  elevate 

*  Desaguliers'  Philosophy,  Vol.  ii. 


454  OF  MUSCULAR  CONTRACTILITY. 

a  weight  equal  to  at  least  500  times  that  of  its  body.  And  a  small  Carabus 
has  been  seen  to  draw  a  weight  of  85  grains  (about  24  times  that  of  its  body) 
up  a  plane  of  25°  ;  and  a  weight  of  125  grains  (36  times  that  of  its  body) 
up  a  plane  of  5°  ;  and  in  both  these  instances  the  friction  was  considerable, 
the  weights  being  simply  laid  upon  a  piece  of  paper,  to  which  the  insect  was 
attached  by  a  string. 

600.  The  rapidity  of  the  changes  of  position  of  the  component  particles 
of  muscular  fibres,  may,  as  Dr.  Alison  justly  remarks,*  be  estimated,  though 
it  can  hardly  be  conceived  from  various  well-known  facts.  The  pulsations  of 
the  heart  can  sometimes  be  distinctly  numbered  in  children,  at  more  than  200 
in  the  minute;  and  as  each  contraction  of  the  ventricles  occupies  only  one- 
third  of  the  time  of  the  whole  pulsation,  it  must  be  accomplished  in  l-600th 
of  a  minute,  or  l-10th  of  a  second.  Again,  it  is  certain  that,  by  the  move- 
ments of  the  tongue  and  other  organs  of  speech,  1500  letters  can  be  distinctly 
pronounced  by  some  persons  in  a  minute  :  each  of  these  must  require  a  sepa- 
rate contraction  of  muscular  fibres  ;  and  the  production  and  cessation  of  each 
of  the  sounds,  imply  that  each  separate  contraction  must  be  followed  by  a 
relaxation  of  equal  length ;  each  contraction,  therefore,  must  have  been  ef- 
fected in  l-1000th  part  of  a  minute,  or  in  the  l-10th  of  a  second.  Haller 
calculated  that,  in  the  limbs  of  a  dog  at  full  speed,  muscular  contractions  must 
take  place  in  less  than  the  l-200th  of  a  second,  for  many  minutes  at  least  in 
succession.-^All  these  instances,  however,  are  thrown  into  the  shade,  by  those 
which  may  be  drawn  from  the  class  of  Insects.  The  rapidity  of  the  vibra- 
tions of  the  wings  may  be  estimated  from  the  musical  tone  which  they  pro- 
duce ;  it  being  easily  ascertained  by  experiments,  what  number  of  vibrations 
are  required  to  produce  any  note  in  the  scale.  From  these  data,  it  appears 
to  be  the  necessary  result,  that  the  wings  of  many  Insects  strike  the  air  many 
hundred,  or  even  many  thousand,  times  in  every  second. — The  minute  pre- 
cision with  which  the  degree  of  muscular  contraction  can  be  adapted  to  the 
designed  effect,  is  in  no  instance  more  remarkable  than  in  the  Glottis.  The 
musical  pitch  of  the  tones  produced  by  it,  is  regulated  by  the  degree  of  ten- 
sion of  the  chordae  vocales,  which  are  possessed  of  a  very  considerable  de- 
gree of  elasticity  (§  603).  According  to  the  observations  of  Miiller,t  the 
average  length  of  these,  in  the  male,  in  a  state  of  repose,  is  about  73-100ths 
of  an  inch ;  whilst,  in  the  state  of  greatest  tension,  it  is  about  93-100ths ;  the 
difference  being  therefore  20-100ths,  or  one-fifth  of  an  inch  :  in  the  female 
glottis,  the  average  dimensions  are  about  51-100ths,  and"  63-100ths  respect- 
ively ;  the  difference  being  thus  about  one-eighth  of  an  inch.  Now  the  natu- 
ral compass  of  the  voice,  in  most  persons  who  have  cultivated  the  vocal 
organ,  may  be  stated  at  about  two  octaves,  or  24  semitones.  Within  each 
semitone,  a  singer  of  ordinary  capability  could  produce  at  least  ten  distinct 
intervals  ;  so  that  of  the  total  number,  240  is  a  very  moderate  estimate.  There 
must,  therefore,  be  at  least  240  different  states  of  tension  of  the  vocal  cords, 
every  one  of  which  is  producible  by  the  will,  without  any  previous  trial ;  and 
the  whole  variation  in  the  length  of  the  cords  being  not  more  than  one-fifth 
of  an  inch  even  in  man,  the  variation  required  to  pass  from  one  interval  to 
another,  will  not  be  more  than  one  twelve-hundredth  of  an  inch.  And  yet 
this  estimate  is  much  below  that  which  might  be  truly  made  from  the  per- 
formances of  a  practised  vocalist.^ 

*  Cyclopaedia  of  Anatomy  and  Physiology,  Art.  Contractility. 

t  Physiology,  1018. 

J  It  is  said  that  the  celebrated  Made.  Mara  was  able  to  sound  100  different  intervals*e- 
tween  each  tone.  The  compass  of  her  voice  was  at  least  three  octaves,  or  22  tones ;  so  that 
the  total  number  of  intervals  was  2200,  all  comprised  within  an  extreme  variation  of  one- 
eighth  of  an  inch  5  so  that  it  might  be  said  that  she  was  able  to  determine  the  contractions 
of  her  vocal  muscles  to  the  seventeen-thousandth  of  an  inch. 


4  OF  THE  VOICE  AND  SPEECH.  455 

601.  Of  the  different  associations  of  Muscular  actions,  which  are  em- 
ployed for  various  purposes  in  the  living  body,  it  would  be  out  of  place  here 
to  speak ;  since  these  associations  depend  upon  the  Nervous  rather  than  upon 
the  muscular  system  ;  and  the  most  important  of  them  have  already  been  con- 
sidered in  detail.  It  may  be  mentioned,  however,  that  the  aptitude  which  is 
acquired  by  practice,  for  the  performance  of  particular  actions,  that  were  at 
first  accomplished  with  difficulty,  seems  to  result  as  much  from  a  change, 
which  the  continual  repetition  of  them  occasions  in  the  Muscle,  as  in  the 
habit  which  the  Nervous  system  acquires,  of  exciting  their  performance. 
Thus  almost  every  person  learning  to  play  on  a  musical  instrument,  finds  a 
difficulty  in  causing  the  two  shorter  fingers  to  move  independently  of  each 
other  and  of  the  rest ;  this  is  particularly  the  case  in  regard  to  the  ring-finger. 
Any  one  may  satisfy  himself  of  the  difficulty,  by  laying  the  palm  of  the  hand 
flat  on  a  table,  and  raising  one  finger  after  the  other,  when  it  will  be  found, 
that  the  ring-finger  cannot  be  lifted  without  disturbing  the  rest, — evidently 
from  the  difficulty  of  detaching  the  action  of  that  portion  of  the  extensor 
communis  digitorum,  by  which  the  movement  is  produced,  from  that  of  the 
remainder  of  the  muscle.  Yet  to  the  practised  musician,  the  command  of  the 
will  over  all  the  fingers  becomes  nearly  alike  ;  and  it  can  scarcely  be  doubted 
that  some  change  takes  place  in  the  structure  of  the  muscle,  which  favours  the 
isolated  operation  of  its  several  divisions. 


CHAPTER    VIII. 

OF  THE  VOICE  AND  SPEECH. 

1.  The  Larynx,  and  its  Actions. 

602.  THE  sounds  produced  by  the  organ  of  Voice  constitute  the  most  im- 
portant means  of  communication  between   Man  and   his   fellows  ;  and  the 
power  of  speech  has,  therefore,  a  primary  influence,  as  well  on  his  physical 
condition,  as  on  the  development  of  his  mental  faculties.     Hence,  although  it 
only  depends  on  one  particular   application  of  muscular  force,  comparable 
to  that  by   which  other  volitional  or  emotional  movements  are  effected,  it 
seems  right,  in  treating  of  the  Physiology  of  man,  to  make  it  an  object  of 
special  consideration.     In  order  to  understand  the  nature  of  the  Organ  of 
Voice  as  a  generator  of  Sound,  it  is  requisite  to  inquire,  in  the  first,  instance, 
into  the  sources  from  which  sounds  at  all  corresponding  to  the  human  voice 
are  elsewhere  obtained.     It  is  necessary  to  bear  in  mind,  that  Vocal  Sounds, 
and  Speech  or  Articulate  Language,  are  two  things  entirely  different;  and 
that  the  former  may  be  produced  in  great  perfection,  where  there  is  no  ca- 
pability for  the  latter.     Hence  we  should  at  once  infer,  that  the  instrument 
for  the  production  of  Vocal  Sounds  was  distinct  from  that  by  which  these 
sounds  are  modified  into  articulate  speech  ;  and  this  we  easily  discover  to  be 
the  case, — the  Voice  being  unquestionably  produced  in  the  Larynx,  whilst 
the  modifications  of  it,  by  which  language  is  formed,  are  effected  for  the  most 
part  in  the  Oral  cavity.     The  structure  and  functions  of  the  former,  then,  first 
claim  our  attention. 

603.  It  will  be  remembered  that  the  Windpipe  is  surmounted  by  a  stout 
cartilaginous  annulus,  termed  the  Cricoid  cartilage ;  which  serves  as  a  founda- 


456 


OF  THE  VOICE  AND  SPEECH. 


tion  for  the  super] acent  mechanism.  This  is  embraced  (as  it  were)  by  the 
Thyroid,  which  is  articulated  to  its  sides  by  its  lower  horns,  round  the  ex- 
tremities of  which  it  may  be  regarded  as  turning,  as  on  a  pivot.  In  this  man- 


External  and  sectional  views  of  the  Larynx.  A  n  B,  the  cricoid  cartilage ;  E  c  G,  the  thyroid  cartilage ; 
G,  its  upper  horn  ;  c,  its  lower  horn,  where  it  is  articulated  with  the  cricoid ;  F,  the  arytenoid  cartilage  ; 
E,  F,  the  vocal  ligament ;  A.  K,  crico-thyroideus  muscle  ;  F  e  m,  thyro-arytenoideus  muscle ;  x  e,  crico-ary- 
tenoideus  lateralis ;  s,  transverse  section  of  arytenoideus  transversus ;  m  n,  space  between  thyroid  and 
cricoid ;  B  L,  projection  of  axis  of  articulation  of  arytenoid  with  thyroid, 

ner  the  lower  front  border  of  the  thyroid  cartilage,  which  is  ordinarily  sepa- 
rated by  small  intervals  from  the  upper  margin  of  the  cricoid,  may  be  made  to 
approach  it  or  recede  from  it ;  as  any  one  may  easily  ascertain,  by  placing 
his  finger  against  the  little  depression  which  may  be  readily  felt  externally, 
and  observing  its  changes  of  size,  whilst  a  range  of  different  tones  is  sounded ; 
it  will  then  be  observed  that,  the  higher  the  note,  the  more  the  two  cartilages 
are  made  to  approximate, — whilst  they  seperate  in  proportion  to  the  depth  of 
the  tones.*  Upon  the  upper  surface  of  the  back  of  the  cricoid,  are  seated 
the  two  small  Arytenoid  cartilages ;  these  are  fixed  in  one  direction  by  a 
bundle  of  strong  ligaments,  which  tie  them  to  the  back  of  the  cricoid  ;  but 
they  have  some  power  of  moving  in  other  directions  upon  a  kind  of  articulat- 
ing surface.  The  direction  of  the  surface,  and  the  mode  in  which  these  car- 
tilages are  otherwise  attached,  cause  their  movement  to  be  a  sort  of  rotation 
in  a  plane,  which  is  nearly  horizontal,  but  partly  downwards ;  so  that  their 
vertical  planes  may  be  made  to  separate  from  each  other,  and  at  the  same 
time  to  assume  a  slanting  position.  This  change  of  place  will  be  better  un- 
derstood, when  the  action  of  the  muscles  is  described.  To  the  summit  of 
the  arytenoid  cartilages  are  attached  the  chordss  vocales  or  Vocal  Ligaments, 
which  stretch  across  to  the  front  of  the  thyroid  cartilage ;  and  it  is  upon  the 
condition  and  relative  situation  of  these  ligaments,  that  their  action  depends.  It 

*  In  making  this  observation,  it  is  necessary  to  put  out  of  view  the  general  movement  to 
the  larynx  itself,  which  the  finger  must  be  made  to  follow  up  and  down. 


STRUCTURE  AND  ACTIONS  OF  THE  LARYNX. 


457 


Bird's-eye  view  of  larynx  from  above.    G  E  H, 
the  thyroid  cartilage,  embracing  the  ring  of  the 


is  evident  that  they  may  be  rendered  more  or  less  tense  by  the  movement  of 
the  Thyroid  cartilage  just  described; 

being  tightened  by  the    depression  of  Fig.  196. 

its  front  upon  the  Cricoid  cartilage,  and 
slackened  by  its  elevation.  On  the 
other  hand,  they  may  be  brought  into 
more  or  less  close  apposition,  by  the 
movement  of  the  Arytenoid  cartilages  ; 
being  made  to  approximate  closely,  or 
to  recede  in  such  manner  as  to  cause 
the  rima  glottidis  to  assume  the  form 
of  a  narrow  V,  by  the  revolution  of 
these  cartilages.  We  shall  now  in- 
quire into  the  actions  of  the  muscles 
upon  the  several  parts  of  this  apparatus; 
and  first  into  those  of  the  larynx  alone. 
604.  The  depression  of  the  front  of 
the  Thyroid  cartilage,  and  the  conse- 
quent tension  of  the  Vocal  Ligaments, 
are  occasioned  by  the  conjoint  action  of 
the  Crico-thyroidei  on  both  sides  ;  and 
the  chief  antagonists  to  these  are  the 
Thyro-arytenoidei,  which  draw  the 

front  of  the  Thyroid   back  towards  the  cricoid  r  u  x  w,  and  turning  upon  the  axis  x  z, 

Arytenoid  Cartilages,  and  thus  relax  the  which  passes  through  the  lower  horns,  c,  Fig.  113, 

VOCal   Hp-amentS.      These    tWO    pairs    of  N  F'  N  F'  the  aiTtenoid  cartilages,  connected  by 

muscles  may  be    regarded    as    the    prin-  ^  arytenoideus  transversus ;  T  v,  x  v  the  vocal 

f  „    P       .     ,       r  ,  ligaments;  N  x,  the  right  cnco-arytenoideus  late- 

cipal  governors  of  the  pitch  of  the  notes,  ralis  (the  left  being  removed) .  v  kf)  the  left  thyro. 

which,  as  we  shall    hereafter  see,  is  al-    arytenoideus  (the  right*being  removed) ;  N  I,  N  ?, 
most   entirely  regulated   by  the    tension    the  crico-arytenoidei  posticij   B,  B,  the  crico-ary- 

of  the   ligaments ;    their  action   is  as-  tenoid  ligaments, 
sisted,  however,  by  that  of  other  muscles 

presently  to  be  mentioned. — The  Arytenoid  cartilages  are  made  to  diverge 
from  each  other,  by  means  of  the  Crico-arytenoideus  posticus  of  each  side, 
which  proceeds  from  their  outer  corner,  and  turns  somewhat  round  the  edge 
of  the  Cricoid,  to  be  attached  to  the  lower  part  of  its  back  ;  its  action  is  to 
draw  the  outer  corner  backwards  and  downwards,  so  that  the  points  to  which 
the  vocal  ligaments  are  attached,  are  separated  from  one  another,  and  the 
Rima  Glottidis  is  thrown  open.  This  will  be  at  once  seen  from  the  succeed- 
ing diagram,  in  which  the  direction  of  traction  of  the  several  muscles  is  laid 
down. — The  action  of  this  muscle  is  partly  antagonized  by  that  of  the  Crico- 
arytenoideus  lateralis,  which  runs  forwards  and  downwards  from  the  outer 
corner  of  the  Arytenoid  cartilage ;  and  its  action,  with  that  of  its  fellow,  will 
be  to  bring  the  anterior  points  of  the  Arytenoid  cartilages  into  the  same 
straight  line,  at  the  same  time  depressing  them,  and  thus  to  close  the  Glottis. 
This  muscle  is  assisted  by  the  Arytenoideus  transversus,  which  connects 
the  posterior  faces  of  the  Arytenoid  cartilages,  and  which,  by  its  contraction* 
will  draw  them  together.  By  the  conjoint  action,  therefore,  of  the  Crico-ary- 
tenoideus lateralis,  and  of  the  Arytenoideus  transversus,  the  whole  of  the  ad- 
jacent faces  of  the  Arytenoid  cartilages  will  be  pressed  together;  and  the 
points  to  which  the  vocal  ligaments  are  attached,  will  be  depressed.— But  if 
the  Arytenoideus  be  put  in  action  in  conjunction  with  the  Crico-arytenoidei 
postici,  the  tendency  of  the  latter  to  separate  the  Arytenoid  cartilages  being 
antagonized  by  the  former,  its  backward  action  only  will  be  exerted  ;  and  thus 
it  maybe  caused  to  aid  the  Crico-thyroideus  in  rendering  tense  the  vocal 
39 


458 


OF  THE  VOICE  AND  SPEECH. 


ligaments.  This  action  will  be  further  assisted  by  the  Sterno-thyroideus, 
which  tends  to  depress  the  Thyroid  cartilage,  by  pulling  from  a  fixed  point 
below  ;*  and  the  Thyro-hyoideus  will  be  the  antagonist  of  this,  when  it  acts 


Part  of  Fig.  196  enlarged,  to  show  the  direction  of  the  muscular  forces,  which  act  on  the  Arytenoid 
cartilage.  Q  N  v  s,  the  right  Arytenoid  cartilage ;  T  v,  its  vocal  ligament ;  B  R  s,  bundle  of  ligaments  unit- 
ing it  to  Cricoid ;  o  p,  projection  of  its  axis  of  articulation ;  h  g,  direction  of  the  action  of  the  Thyro-ary- 
tenoideus;  N  x,  direction  of  Crico-arytenoideus  lateralis  ;  N  w,  direction  of  Crico-arytenoideus  posticus; 
N  y,  direction  of  Crytenoideus  transversus. 

from  a  fixed  point  above,  the  Os  Hyoides  being  secured  by  the  opposing  con- 
traction of  several  other  muscles. — The  respective  actions  of  these  muscles 
will  be  best  comprehended  by  the  following  Table. 


Govern  the  pitch  of  the  notes. 


CRICO-THYROIDEI 
STERNO-THYBOIDEI 

THYRO-ARYTENOIDEI 
THTHO-HTOIDEI 


!•• 

b 


Depress  the  front  of  the  Thyroid  cartilage  on  the 
Cricoid,  and  stretch  the  vocal  ligaments;  assisted 
by  the  Arytenoideus  and  Crico-arytenoidei  postici. 

Elevate  the  front  of  the  Thyroid  cartilage,  and  draw 
it  towards  the  Arytenoids,  relaxing  the  vocal  liga- 
ments. 


Govern  the  Aperture  of  the  Glottis. 
CHICO-ARYTEHOIDEI  PosTici Open  the  Glottis. 


C  CRICO-ARYTElfOIDEI  LATEHA1ES 
ARYTETSTOIDEUS 


C  Press  together  the  inner  edges  of  the  Ary- 
£      tenoid  cartilages,  arid  dose  the  Glottis. 


605.  The  muscles  which  stretch  or  relax  the  Vocal  ligaments,  are  entirely 
concerned  in  the  production  of  Voice ;  those  which  govern  the  aperture  of 
the  Glottis  have  important  functions  in  connection  with  the  Respiratory 
actions  in  general,  and  stand  as  guards  (so  to  speak)  at  the  entrance  to  the 
lungs.  Their  separate  actions  are  easily  made  evident.  We  can  close  the 
aperture,  of  the  Glottis,  by  an  exertion  of  the  will,  either  during  inspiration  or 
expiration ;  and  it  is  a  kind  of  spasmodic  movement  of  this  sort,  which  is 

*  This  is  not  usually  reckoned  as  one  of  the  principal  muscles  concerned  in  regulating  the 
voice ;  but  that  it  is  so,  any  one  may  convince  himself  by  placing  his  finger  just  above  the 
sternum,  whilst  he  is  sounding  high  notes ;  a  strong  feeling  of  muscular  tension  is  then  at 
once  perceived. 


STRUCTURE  AND  ACTIONS  OF  THE  LARYNX.  459 

concerned  in  the  acts  of  Coughing  and  Sneezing  (§  381),  as  well  as  in  the 
more  prolonged  impediments  to  the  ingress  and  egress  of  air,  which  have  been 
already  noticed  as  resulting  from  disordered  states  of  the  Nervous  system 
(§  504).  A  slight  examination  of  the  recent  Larynx  is  sufficient  to  make  it 
evident  that,  when  once  the  borders  of  the  Rima  Glottidis  are  brought  toge- 
ther by  muscular  action,  the  effect  of  strong  aerial  pressure  on  either  side, — 
whether  produced  by  an  expulsory  blast  from  below,  or  by  a  strong  inspiratory 
effort,  occasioning  a  partial  vacuum  below,  and  consequently  an  increased 
pressure  above, — will  be  to  force  them  into  closer  apposition.  With  this 
action,  then,  the  muscles  which  regulate  the  tension  of  the  vocal  ligaments 
have  nothing  to  do.  In  the  ordinary  condition  of  rest,  it  seems  probable  that 
the  Arytenoid  cartilages  are  considerably  separated  from  each  other ;  so  as  to 
cause  a  wide  opening  to  intervene  between  their  inner  faces,  and  between  the 
vocal  ligaments,  through  which  the  air  freely  passes ;  and  the  vocal  ligaments 
are  at  the  same  time  in  a  state  of  complete  relaxation.  In  order  to  produce 
a  vocal  sound,  it  is  not  sufficient  to  put  the  ligaments  into  a  state  of  tension ; 
they  must  also  be  brought  nearer  to  each  other.  That  the  aperture  of  the 
Glottis  is  greatly  narrowed  during  the  production  of  sounds,  is  easily  made 
evident  to  one's  self,  by  comparing  the  time  occupied  by  an  ordinary  expiration, 
with  that  required  for  the  passage  of  the  same  quantity  of  air  during  the  sus- 
tenance of  a  vocal  tone.  Further,  the  size  of  the  aperture  is  made  to  vary  in 
accordance  with  the  note  which  is  being  produced ;  of  this,  too,  any  one  may 
convince  himself,  by  noting  the  time  during  which  he  can  hold  out  a  low  and 
a  high  note ;  from  which  it  will  appear,  that  the  aperture  of  the  Glottis  is  so 
much  narrowed  in  producing  a  high  note,  as  to  permit  a  much  less  rapid  pas- 
sage of  air,  than  is  allowed  when  a  low  one  is  sounded.  This  adjustment  of 
the  aperture  to  the  tension  of  the  Vocal  Ligaments,  is  a  necessary  condition 
for  the  production  of  a  clear  and  definite  tone.  It  further  appears  that,  in  the 
narrowing  of  the  Glottis,  which  is  requisite  to  bring  the  vocal  ligaments  into 
the  necessary  approximation,  the  upper  points  of  the  Arytenoid  cartilages  are 
caused  to  approximate,  not  only  by  being  made  to  rotate  horizontally  towards 
each  other,  but  also  by  a  degree  of  elevation ;  so  that  the  inner  faces  of  the 
Vocal  Ligaments  are  brought  into  parallelism  with  each  other, — a  condition 
which  may  be  experimentally  shown  to  be  necessary,  for  their  being  thrown 
into  sonorous  vibration. 

606.  We  have  now  to  inquire  what  is  the  operation  of  the  Vocal  Ligaments 
in  the  production  of  sounds ;  and  in  order  to  comprehend  this,  it  is  necessary 
to  advert  to  the  conditions  under  which  tones  are  produced,  by  instruments  of 
various  descriptions,  having  some  analogy  with  the  Larynx. 

a.  These  are  chiefly  of  three  kinds, — strings,  flute-pipes,  and  reeds  or  tongues.  The  Vocal 
Ligaments  were  long  ago  compared  by  Ferrein  to  vibrating  Strings ;  and  at  first  sight  there 
might  seem  a  considerable  analogy,  the  sounds  produced  by  both  being  elevated  by  increased 
tension.  This  resemblance  disappears,  however,  on  more  accurate  comparison ;  for  it  may 
be  easily  ascertained  by  experiment,  that  no  string  so  short  as  the  vocal  ligaments  could  give 
a  clear  tone,  at  all  to  be  compared  in  depth  with  that  of  the  lowest  notes  of  the  human  voice ; 
and  also,  that  the  scale  of  changes  produced  by  increased  tension  is  fundamentally  different. 
When  strings  of  the  same  length,  but  of  different  tension,  are  made  the  subject  of  comparison, 
it  is  found  that  the  number  of  vibrations  is  in  proportion  to  the  square  roots  of  the  extending 
forces.  Thus,  if  a  string  extended  by  a  given  weight  produce  a  certain  note,  a  string  extended 
by  four  times  that  weight  will  give  a  note,  in  which  the  vibrations  are  twice  as  rapid, — and 
this  will  be  the  octave  of  the  other.  If  nine  times  the  original  weight  be  employed,  the 
vibrations  will  be  three  times  as  rapid  as  those  of  the  fundamental  note,  producing  the 
twelfth  above  it.  Now  by  fixing  the  larynx  in  such  a  manner,  that  the  vocal  ligaments  can 
be  extended  by  a  known  weight,  Miiller  has  ascertained  that  the  sounds  produced  by  a  varia- 
tion of  the  extending  force  will  not  follow  the  same  ratio ;  and  therefore  the  condition  of 
these  ligaments  cannot  be  simply  that  of  vibrating  ,cords.  Further,  a  cord  of  a  certain  length, 
which  is  adapted  to  give  out  a  clear  and  distinct  note,  equal  in  depth  to  the  lowest  of  the 


460  OF  THE  VOICE  AND  SPEECH. 

human  voice,  may  be  made  by  increased  tension  to  produce  all  the  superior  notes,  which, 
in  stringed  instruments,  are  ordinarily  obtained  by  shortening  the  strings.*  But  it  does  not 
follow  that  a  short  string,  which,  with  moderate  tension,  naturally  produces  a  high  note, 
should  be  able,  by  a  diminution  of  the  tension,  to  give  out  a  deep  one;  for,  although  this 
might  be  theoretically  possible,  yet  it  cannot  be  accomplished  in  practice ;  since  the  vibrations 
become  irregular  on  account  of  the  diminished  elasticity .j"  These  considerations  are  in  them- 
selves sufficient  to  destroy  the  supposed  analogy ;  and  to  prove  that  the  Chordae  Vocales  can- 
not be  reduced  to  the  same  category  with  vibrating  strings. 

b.  The  next  kind  of  instrument,  with  which  some  analogy  might  be  suspected,  is  the 
Flute-pipe,  in  which  the  sound  is  produced  by  the  vibration  of  an  elastic  column  of  air  con- 
tained in  the  tube ;  and  the  pitch  of  the  note  is  determined  almost  entirely  by  the  length  of  the 
column,  although  slightly  modified  by  its  diameter,  and  by  the  nature  of  the  embouchure  or 
mouth  from  which  it  issues.     This  is  exemplified  in  the  German  Flute,  and  in  the  English 
Flute  or  Flageolet;  in  both  of  which  instruments,  the  acting  length  of  the  pipe  is  determined, 
by  the  interval  between  the  embouchure  and  the  nearest  of  the  side  apertures ;  by  opening 
or  closing  which,  therefore,  a  modification  of  the  tone  is  produced.     In  the  Organ,  of  which 
the  greater  number  of  pipes  are  constructed  upon  this  plan,  there  is  a  distinct  pipe  for  every 
note ;  and  their  length  increases  in  a  regular  scale.     It  is,  in  fact,  with  flute-pipes  as  wim 
strings, — that  a  diminution  in  length  causes  an  increase  in  the  number  of  vibrations,  in  an 
inverse  proportion ;  so  that  of  two  pipes,  one  being  half  the  length  of  the  other,  the  shorter 
will  give  a  tone  which  is  the  octave  above  the  other,  the  vibrations  of  its  column  of  air  being 
twice  as  rapid.     Now  there  is  nothing  in  the  form  or  dimensions  of  the  column  of  air  be- 
tween the  larynx  and  the  mouth,  which  can  be  conceived  to  render  it  at  all  capable  of  such 
vibrations,  as  are  required  to  produce  the  tones  of  the  Human  voice ;  though  there  is  some 
doubt,  whether  it  is  not  the  agent  in  the  musical  tones  of  certain  Birds.     The  length  of  an 
open  pipe  necessary  to  give  the  lowest  G  of  the  ordinary  bass  voice,  is  nearly  six  feet ;  and 
the  conditions  necessary  to  produce  the  higher  notes  from  it,  are  by  no  means  those  which 
we  find  to  exist  in  the  process  of  modulating  the  human  voice. 

c.  We  now  come  to  the  third  class  of  instruments,  in  which  sound  is  produced  by  the 
vibration  of  Reeds  or  Tongues;  these  may  either  possess  elasticity  in  themselves,  or  be  made 
elastic  by  tension.     The  reeds  of  the  Mouth-Eolina,  Accordion,  Seraphine,  &c.,  are  examples 
of  instruments  of  this  character,  in  which  the  lamina  vibrates  freely  in  a  sort  of  frame,  that 
allows  the  air  to  pass  out  on  all  sides  of  it  through  a  narrow  channel,  thus  increasing  the 
strength  of  the  blast :  whilst  in  the  Hautboy,  Bassoon,  &c.,  and  in  Organ-pipes  of  similar  con- 
struction, the  reed  is  attached  to  one  end  of  a  pipe.     In  the  former  kind,  the  sound  is  pro- 
duced by  the  vibration  of  the  tongue  alone,  and  is  regulated  entirely.by  its  length  and  elasti- 
city; whilst  in  the  latter,  its  pitch  is  dependent  upon  this  conjointly  with  the  length  of  the 
tube,  the  column  of  air  contained  in  which  is  thrown  into  simultaneous  vibration.     Some 
interesting  researches  on  the  effect  produced  on  the  pitch  of  a  sound  given  by  a  reed,  through 
the  union  of  it  with  a  tube,  have  been  made  by  M.  W.  Weber ;  and,  as  they  are  important 
in  furnishing  data,  by  which  the  real  nature  of  the  vocal  organ  may  be  determined,  their 
chief  results  will  be  here  given. — i.  The  pitch  of  a  reed  may  be  lowered,  but  cannot  be 
raised,  by  joining  it  to  a  tube.     u.  The  sinking  of  the  pitch  of  the  reed  thus  produced,  is  at 
the  utmost  not  more  than  an  octave,    in.  The  fundamental  note  of  the  reed  thus  lowered,  may 
be  raised  again  to  its  original  pitch,  by  a  further  lengthening  of  the  tube :  and  by  a  further 
increase  is  again  lowered,     iv.  The  length  of  tube,  necessary  to  lower  the  pitch  of  the  in- 
strument to  any  given  point,  depends  on  the  relation  which  exists  between  the  frequency  of 
the  vibrations  of  the  tongue  of  the  reed,  and  those  of  the  column  of  air  in  the  tube,  each 
taken  separately. — From  these  data,  and  from  those  of  the  preceding  paragraph,  it  follows 
that,  if  a  wind-instrument  can,  by  the  prolongation  of  its  tube,  be  made  to  yield  tones  of  any 
depth  in  proportion  to  the  length  of  the  tube,  it  must  be  regarded  as  a  flute-pipe ;  whilst,  if 
its  pitch  can  only  be  lowered  an  octave  or  less  (the  embouchure  remaining  the  same)  by 
lengthening  the  tube,  we  may  be  certain  that  it  is  a  reed  instrument.     The  latter  proves  to 
be  the  case  in  regard  to  the  Larynx. 

607.  It  is  evident  from  the  foregoing  considerations,  that  the  action  of  the 
Larynx  has  more  analogy  to  that  of  reed  instruments,  than  it  has  to  that  either 

*  Thus  in  the  Piano-forte,  where  there  are  strings  for  each  note,  a  gradual  shortening  is 
seen  from  the  lowest  to  the  highest;  and  in  the  Violin  the  change  of  tone  is  produced  by 
stopping  the  strings  with  the  finger,  so  as  to  diminish  their  acting  length. 

f  Thus  it  would  be  impossible  to  produce  good  Bass  notes  on  the  strings  of  a  Violin,  by 
diminishing  their  tension;  the  length  afforded  by  the  Violoncello  or  Double  Bass  is  requisite. 
The  striking  difference  between  the  tone  of  the  Bass  strings  in  the  Grand  Piano-forte  and  the 
small  upright  Piccolo,  is  another  exemplification  of  the  same  principle ;  being  chiefly  due  to 
the  length  and  tension  of  the  former,  as  contrasted  with  the  shortness  and  slackness  of  the 
latter. 


ACTIONS  OF  THE  LARYNX. 


461 


of  vibrating  strings,  or  of  flute,  pipes.  There  would  seem,  at  first  sight,  to  be 
a  marked  difference  in  character,  between  the  Chords  Vocales,  and  the  tongue 
of  any  reed  instrument ;  but  this  difference  is  really  by  no  means  considera- 
ble. In  a  reed,  elasticity  is  a  property  of  the  tongue  itself,  when  fixed  at  one 
end,  the  other  vibrating  freely ;  but  by  a  membranous  lamina,  fixed  in  the 
same  manner,  no  tone  would  be  produced.  If  such  a  lamina,  however,  be 
made  elastic  by  a  moderate  degree  of  tension,  and  be  fixed  in  such  a  manner 
as  to  be  advantageously  acted  on  by  a  current  of  air,  it  will  give  a  distinct 
tone.  It  is  observed  by  Miiller,  that  membranous  tongues  made  elastic  by 
tension,  may  have  either  of  three  different  forms,  i.  That  of  a  band  extended 
by  a  cord,  and  included  between  two  firm  plates,  so  that  there  is  a  cleft  for 
the  passage  of  air  on  each  side  of  the  tongue,  n.  The  elastic  membrane 
may  be  stretched  over  the  half  or  any  portion  of  the  end  of  a  short  tube,  the 
other  part  being  occupied  by  a  solid  plate,  between  which  and  the  elastic 
membrane  a  narrow  fissure  is  left.  in.  Two  elastic  membranes  may  be  ex- 
tended across  the  mouth  oY  a  short  tube,  each  covering  a  portion  of  the  opening, 
and  having  a  chink  left  open  between  them. — This  last  is  evidently  the  form 
most  allied  to  the  Human  Glottis ;  but  it  may  be  made  to  approximate  still  more 
closely,  by  prolonging  the  membranes  in  a  direction  parallel  to  that  of  the  cur- 
rent of  air,  so  that  not  merely  their  edges,  but  their  whole  planes,  shall  be 
thrown  into  vibration.  Upon  this  principle,  a  kind  of  artificial  Glottis  has 
been  constructed  by  Mr.  Willis ;  the  conditions  of  action,  and  the  effects  of 
which,  are  so  nearly  allied  to  that  of  the  real  instrument,  that  the  similar  cha- 
racter of  the  two  can  scarcely  be  doubted.  The  following  is  his  description 
of  it.  "Let  a  wooden  pipe  be  prepared  of  the  form  of  Fig.  198  a,  having  a 
foot,  c,  like  that  of  an  organ-pipe,  and  an  upper  opening,  long  and  narrow,  as 
at  B,  with  a  point  A,  rising  at  one 

end  of  it.     If  a  piece  of  leather,  or  Fig.  198. 

still  better,  of  sheet  India-rubber,  be  a  & 

doubled  round  this  point,  and  secur- 
ed by  being  bound  round  the  pipe 
at  D  with  strong  thread,  as  in  Fig. 
198,  &,  it  will  give  us  an  artificial 
glottis,  with  its  upper  edges  G  H, 
which  may  be  made  to  vibrate  or 
not,  at  pleasure,  by  inclining  the 
planes  of  the  edges.  A  couple  of 
pieces  of  cork,  E,  F,  may  be  glued 
to  the  corners,  to  make  them  more 
manageable.  From  this  machine, 
various  notes  may  be  obtained,  by 
stretching  the  edges  in  the  direction 
of  their  length,  G  H  ;  the  notes  rising 
in  pitch  with  the  increased  tension, 
although  the  length  of  the  vibrating 
edge  is  increased.  It  is  true,  that  a 
scale  of  notes  equal  in  extent  to  that 
'of  the  human  voice,  cannot  be  ob-  Artificial  Glottis. 

tained  from   edges  of  leather;  but 

this  scale  is  much  greater  in  India-rubber  than  in  leather ;  and  the  elasticity 
of  them  both  is  so  much  inferior  to  that  of  the  vocal  ligaments,  that  we  may 
readily  infer  that  the  great  scale  of  the  latter  is  due  to  its  greater  elastic  pow- 
ers." By  other  experimenters,  the  tissue  forming  the  middle  coat  of  the  arte- 
ries has  been  used  for  this  purpose,  in  the  moist  state,  with  great  success  ; 
with  this,  the  tissue  of  the  vocal  ligaments  is  nearly  identical.  It  is  worthy 

39* 


462  OF  THE  VOICE  AND  SPEECH. 

of  remark  that,  in  all  such  experiments,  it  is  found  that  the  two  membranes 
may  be  thrown  into  vibration,  when  inclined  towards  each  other  in  various 
degrees,  or  even  when  they  are  in  the  same  plane,  and  their  edges  only  ap- 
proximate ;  but  that  the  least  inclination  from  each  other  (which  is  the  posi- 
tion the  vocal  ligaments  have  during  the  ordinary  state  of  the  glottis,  §  605,) 
completely  prevents  any  sonorous  vibrations  from  being  produced. 

608.  The  pitch  of  the  note  produced  by  membranous  tongues,  may  be 
affected  in  several  ways.    Thus,  an  increase  in  the  strength  of  the  blast,  which 
has  little  influence  on  metallic  reeds,  raises  their  pitch  very  considerably ; 
and  in  this  manner  the  note  of  a  membranous  reed  may  be  raised  by  semitones, 
to  as  much  as  a  fifth  above  the  fundamental.     The  addition  of  a  pipe  has 
nearly  the  same  effect  on  their  pitch,  as  on  that  of  metallic  reeds  ;  but  it  can- 
not easily  be  determined  with  the  same  precision.     The  effect  of  the  junction 
of  a  pipe  with  a  double  membranous  tongue,  is  well  shown  in  the  Trumpet, 
Horn,  and  other  instruments  ;  which  require  the  vibration  of  the  lips,  as  well 
as  a  blast  of  air,  for  the  production  of  their  sound,' having  no  reed  of  their 
own.     By  some,  these  instruments  have  been  classed  with  Flute-pipes  ;  but 
the  conditions  of  their  action  are  entirely  different.     The  mouth-piece  of  the 
horn  or  trumpet  is  incapable  of  yielding  any  tone,  when  a  current  of  air  is 
merely  blown  through  it ;  and  the  lips  are  necessary  to  convert  it  into  a  musi- 
cal reed,  being  rendered  tense  by  the  contraction  of  their  sphincter,  partly 
antagonized  by  the  slightly-dilating  action  of  other  muscles.     The  variation 
of  the  tension  of  the  lips  is  effected  by  muscular  effort ;  and  several  different 
notes  may  be  produced  with  a  pipe  of  the  same  length  ;  but  there  is  a  certain 
length  of  the  column  of  air,  which  is  the  one  best  adapted  for  each  tone  ;  and 
different  instruments  possess  various  contrivances  for  changing  this.     It  has 
been  recently  ascertained,  that  the  length  of  the  pipe  prefixed  to  the  reed,  has 
also  a  considerable  influence  on  its  tone,  rendering  it  deeper  in  proportion  as 
it  is  prolonged,  down  to  nearly  the  octave  of  the  fundamental  note ;  but  the 
pitch  then  suddenly  rises  again,  as  in  the  case  of  the  tube  placed  beyond  the 
reed.    The  researches  of  Miiller,  however,  have  not  succeeded  in  establishing 
any  very  definite  relation  between  the  length  of  the  two  tubes,  in  regard  to 
their  influence  on  the  pitch  of  the  reed  placed  between  them. 

609.  From  the  foregoing  statements  it  appears,  that  the  true  theory  of  the 
Voice  may  now  be  considered  as  well  established,  in  regard  to  this  essential 
particular, — that  the  sound  is  the  result  of  the  vibrations  of  the  vocal  ligaments, 
which  take  place  according  to  the  same  laws  with  those  of  metallic  or  other 
elastic  tongues :  and  that  the  pitch  of  the  notes  is   chiefly  governed  by  the 
tension  of  these  laminae.     With  respect,  however,  to  the  modifications  of  these 
tones,  induced  by  the  shape  of  the  air-passages,  both  above  and  below  the 
larynx,  by  the  force  of  the  blast,  and  by  other  concurrent  circumstances,  little 
is  certainly  known.     Hence  it  is,  that  on  the  theory  of  the  production  of  what 
are  called  falsetto  notes,  there  is  much  difference  of  opinion  amongst  Physi- 
ologists.    Some  have  contended,  that  these  tones  are  produced  by  the  vibra- 
tion of  the  vocal  ligaments  along  only  a  part  of  their  length ;  but  this  is  cer- 
tainly untrue.     By  Miiller  it  is  believed,  that  in  the  falsetto  notes  merely  the 
thin  border  of  the  glottis  vibrates,  so  that  the  fissure  remains  distinctly  visible ; 
whilst  in  the  production  of  the  ordinary  vocal  tones,  the  whole  breadth  of  the 
vocal  ligaments  is  thrown  into  strong  vibrations,  which  traverse  a  wider  sphere, 
so  that  a  confused  motion  is  seen  in  the  lips  of  the  glottis,  rendering  its  fissure 
obscure.     That  the  tension  of  the  vocal  cords  is  not  diminished  (as  it  ought 
to  be  if  only  a  part  of  their  length  were  being  used),  but  is  progressively  in- 
creased, as  we  pass  from  the  ordinary  to  the  falsetto  scale,  any  one  may  con- 
vince himself,  by  placing  his  finger  on  the  interval  between  the  thyroid  and 


ACTIONS  OF  THE  LARYNX.  463 

cricoid  cartilages,  as  formerly  described  (§  603).*— A  very  important  adjunct 
to  the  production  of  the  higher  notes,  has  been  pointed  out  by  Miiller,  as 
being  afforded  by  the  modification  in  the  space  included  between  the  two 
sides  of  the  thyroid  cartilage,  which  is  effected  by  the  thyro-arytenoidei.  He 
had  experimentally  ascertained,  that  the  introduction  of  a  hollow  plug  into  the 
upper  end  of  the  pipe  beneath  his  artificial  larynx  (and  therefore  just  below 
the  reed),  by  diminishing  its  aperture,  produced  a  considerable  elevation  of 
the  tone.  The  action  may  be  imitated  in  the  human  larynx,  when  made  the 
subject  of  experiment,  by  compressing  the  thyroid  cartilage  laterally;  and  in 
this  manner,  the  natural  voice  could  be  made  to  extend  through  a  range,  that 
could  otherwise  be  only  reached  by  a  falsetto. 

610.  The  strength  of  the  tone  produced  in  the  larynx,  is  much  increased 
by  the  resonance  of  the  elastic  tissue,  which  it  contains  in  various  other  parts  ; 
but  still  more,  perhaps,  by  that  produced  by  the  air  in  the  trachea,  bronchi, 
and  pulmonary  cells.  This  comes  to  be  of  great  importance  in  the  pheno- 
mena of  auscultation.  The  aerial  resonance  is  loudest  where  any  large  body 
of  air  is  collected  together,  as  in  the  trachea,  the  larger  bronchi,  an  emphyse- 
matous  dilatation,  or  a  cavity  resulting  from  tubercular  softening.  On  the 
other  hand,  solidification  of  the  pulmonary  tissue  will  produce  a  resonance  of 
a  somewhat  different  kind.  The  influence  of  the  prefixed  and  superadded 
tubes,  in  modifying  the  tones  produced  by  the  Human  larynx,  has  been  found 
by  Prof.  Miiller  not  to  be  at  all  comparable  to  that  which  they  exercised 
over  the  artificial  larynx ;  the  reason  of  which  difference  does  not  seem  very 
apparent.  It  appears,  however,  that  there  is  a  certain  length  of  the  prefixed 
tube, — as  there  is  a  certain  distance  of  the  vibrating  lamina?,  and  a  certain 
length  or  form  of  the  tube  above, — which  is  most  favourable  to  the  produc- 
tion of  each  note ;  and  the  downward  movement  of  the  whole  vocal  organ, 
which  takes  place  when  we  are  sounding  deep  notes,  and  its  rise  during  the 
elevation  of  the  tones,  have  been  supposed  to  have  the  purpose  of  making  this 
adjustment  in  the  length  of  the  trachea;  but  this  requires  the  supposition, 
that  the  real  length  of  the  trachea  is  shortened  whilst  it  appears  extended, — • 
for  which  there  seems  no  foundation.  It  is  considered  by  Mr.  Wheatstone, 
that  the  column  of  air  in  the  trachea  may  divide  itself  into  harmonic  lengths, 
and  may  produce  a  reciprocation  of  the  tone  given  by  the  vocal  ligaments 
(§  560) ;  and  in  this  manner  he  considers  that  the  falsetto  notes  are  to  be 
explained.  It  may  be  added,  that  the  partial  closing  of  the  epiglottis  seems 
to  assist  in  the  production  of  deep  notes,  just  as  the  partial  covering  of  the 
top  of  a  short  pipe  fixed  to  a  reed  will  lower  its  tone ;  and  that  something  of 
this  kind  takes  place  during  natural  vocalization,  would  appear,  from  the  re- 
traction and  depression  of  the  tongue  which  accompany  the  lowering  of  the 
front  of  the  head,  when  the  very  lowest  notes  are  being  sounded.  The  arches 
of  the  palate  and  uvula  become  contracted  during  the  formation  of  the  higher 
tones ;  but  no  difference  can  be  perceived  in  their  state,  whether  these  tones 
be  falsetto  or  not;  hence  it  would  appear  that  they  have  no  concern  in  this 
peculiarity ;  and  the  purpose  of  their  increased  tension  is  probably  to  main- 
tain their  power  of  resonance.  The  experiments  of  Savart  have  shown,  that 
a  cavity  which  only  responds  to  a  shrill  note,  when  its  walls  are  firm  and  dry, 
may  be  made  to  afford  a  great  variety  of  lower  tones,  when  its  walls  are 

*  That  the  falsetto  voice  differs  in  some  essential  particular  from  the  natural,  is  evident 
from  this, — that  many  persons  who  possess  a  considerable  range  of  both,  are  yet  unable  to 
unite  them,  so  as  to  sing  through  the  whole  scale  without  a  marked  interruption.  Thus  a 
gentleman  of  the  Author's  acquaintance  has  a  bass  voice,  ranging  from  the  lowest  D  of  the 
Square  Piano  to  the  second  D  above;  and  a  falsetto  ranging  from  the  A  below  this  to  the  E 
of  the  octave  above,  so  as  to  give  a  compass  of  more  than  three  octaves  on  the  whole ;  yet . 
the  two  registers  cannot  be  smoothly  blended. 


464  OF  THE  VOICE  AND  SPEECH. 

moistened  and  relaxed  in  various  degrees.     This  observation  may  probably 
be  applied  also  to  the  trachea. 

611.  These  and  numerous  other  muscular  actions,  which  are  employed  in 
the  production  and  regulation  of  the  voice,  are  effected  by  an  impulse  which 
can  scarcely  be  termed  Voluntary,  and  the  nature  of  which  is  a  curious  sub- 
ject for  inquiry.     It  may  be  safely  affirmed,  that  the  production  of  sounds  is 
in  itself  an  Instinctive  action;  although  the  combination  of  these,  whether  into 
music  or  articulate  language,  is  a  matter  of  acquirement.     Now  it  might  be 
supposed  that  the  Will  has  sufficient  power  over  the  vocal  muscles,  to  put 
them  into  any  state  requisite  for  its  purposes,  without  any  further  condition  : 
but  a  little  self-experiment  will  prove  that  this  is  not  the  case.     No  definite 
tone  can  be  produced  by  a  Voluntary  effort,  unless  that  tone  be  present  to  the 
mind,  during  however  momentary  an  interval,  either  as  immediately  conveyed 
to  it  by  an  act  of  Sensation,  recalled  by  an  act  of  Conception,  or  anticipated 
by  an  effort  of  the  imagination.     When  thus  present,  the  Will  can  enable  the 
muscles  to  assume  the  condition  requisite  to  produce  it;  but  under  no  other 
circumstances  does  this  happen,  except  by  a  particular  mode  of  discipline 
presently  to  be  adverted  to.     The  action  itself,  therefore,  must  be  reduced  to 
the  class  of  consensual  movements ;  and  we  must  suppose  that  the  will  is 
exercised  in  preparing  the  conditions  requisite  for  it,  rather  than  in  directly 
exciting  it. — That  those  who  are  unfortunately  labouring  under  congenital 
deafness,  are  thence  debarred  from  learning  the  use  of  Voice  in  the  ordinary 
manner,  is   well   known;  the  consensual  action  cannot  be  excited,   either 
through  sensations  of  the  present,  or  conceptions  of  the  past ;  and  the  imagi- 
nation is  entirely  destitute  of  power  to  suggest  that  which  has  been  in  no 
shape  experienced.     But  such  persons  may  be  taught  to  speak  in  an  imperfect 
manner,  by  causing  them  to  imitate  particular  muscular  movements,  which 
they  may  be  made  to  see;  and  it  is  evident,  that  they  must  be  guided  in  the 
imitation  and  ordinary  performance  of  those  movements,  by  the  common 
muscular  sensations  which  accompany  them,  and  not  by  the  sensations  con- 
veyed through  the  Auditory  nerve,  which  are  ordinarily  by  far  the  most  pre- 
cise guides.     Many  instances,  indeed,  are  on  record,  in  which  persons  entirely 
deaf  were  enabled  to  carry  on  a  conversation  in  the  regular  way;  judging  of 
what  was  said,  by  the  movements  of  the  lips  and  tongue,  which  they  haol 
learned  to  connect  with  particular  syllables ;  and  regulating  their  own  voices 
in  reply,  by  their  voluntary  power,  guided  by  muscular  sensation.* 

[In  the  foregoing  account  of  the  Physiology  of  Voice,  the  author  has  been  chiefly  guided 
by  the  excellent  paper  by  Mr.  Willis  in  the  Transactions  of  the  Cambridge  Philosophical 
Society,  vol.  iv. ;  and  by  the  elaborate  investigations  of  Miiller  and  his  coadjutors,  as  detailed 
in  the  Fourth  Book  of  his  Physiology.] 

%>—Of  Articulate  Sounds. 

612.  The  larynx,  as  now  described,  is  capable  of  producing  those  tones  of 
which   Voice  fundamentally  consists,  and  the   sequence  of  which  becomes 
Music :  but  Speech  consists  in  the  modification  of  the  laryngeal  tones,  by 
other  organs,  intervening  between  the  Glottis  and  the  Os  Externum  ;  so  as 
to  produce  those  articulate  sounds,  of  which  Language  is  formed.    It  cannot 
be  questioned  that  Music  has  its  language  ;  and  that  it  is  susceptible  of  ex- 
pressing the  emotional  states  of  the  mind,  among  those  at  least  who  have 
been  accustomed  to  associate  these  with  its  varie4  modes,  to  even  a  higher 
degree  than  articulate  speech.     But  it  is  incapable  of  addressing  the  intellect, 
by  conveying  definite  ideas  of  objects,  properties,  actions,  &c,,  in  any  other 

*  See  Johnstone  on  Sensation,  p.  128. 


OF  ARTICULATE  SOUNDS.  465 

way  than  by  a  kind  of  imitation,  which  may  be  compared  to  the  signs  used 
in  hieroglyphic  writing.  These  ideas  it  is  the  peculiar  province  of  articulate 
language  to  convey ;  and  we  find  that  the  vocal  organ  is  adapted  to  form  a 
large  number  of  simple  sounds,  which  may  be  readily  combined  into  groups, 
forming  words.  The  number  of  combinations  which  can  be  thus  produced, 
is  so  inexhaustible,  that  every  language  has  its  own  peculiar  series  ;  no  dif- 
ficulty being  found  in  forming  new  ones  to  express  new  ideas.  There  is  con- 
siderable diversity  in  different  languages,  even  with  regard  to  the  use  of  the 
simplest  of  these  combinations  ;  some  of  them  are  more  easy  of  formation 
than  others,  and  these  accordingly  enter  into  the  composition  of  all  languages ; 
whilst  of  the  more  difficult  ones,  some  are  employed  in  one  language,  some 
in  another, — no  one  language  possessing  them  all.  Without  entering  into  any 
detailed  account  of  the  mechanism  required  to  produce  each  of  these  simple 
sounds,  a  few  general  considerations  will  be  offered  in  regard  to  the  classifi- 
cation of  them ;  and  the  peculiar  defect  of  Articulation,  termed  Stammering, 
will  be  briefly  treated  of. 

613.  Vocal  sounds  are  divided  into  Vowels  and  Consonants ;  and  the  dis- 
tinctive characters  of  these  are  usually  considered  to  be,  that  the  Vowels  are 
produced  by  the  Voice  alone,  whilst  the  sound  of  the  Consonants  is  formed 
by  some  kind  of  interruption  to  the  voice,  so  that  they  cannot  be  properly 
expressed,  unless  conjoined  with   a  vowel.     The  distinction  may  be  more 
correctly  laid  down,  however,  in  this  manner  : — the  Vowel  sounds  are  con- 
tinuous tones,  modified  by  the  form  of  the  aperture  through  which  they  pass 
out ;  whilst  in  sounding  Consonants,  the  breath  suffers  a  more  or  less  com- 
plete interruption,  in  its  passage  through  parts  anterior  to  the  larynx.    Hence 
the  really  simple  Vowel  sounds  are  capable  of  prolongation  during  any  time 
that  the  breath  can  sustain  them  ;  this   is  not  the   case,  however,  with  the 
real  Diphthongal  sounds  (of  which  it  will  presently  appear  that  the  English  i 
is  one)  ;  whilst  it  is  true  of  some  Consonants.     It  seems  to  have  been  for- 
gotten by  many  of  those  who  have  written  upon  this  subject,  that  the  laryn- 
geal  voice  is  not  essential  to  the  formation  of  either  vowels  or  consonants;  for 
all  may  be  sounded  in  a  whisper.     It  is  very  evident,  therefore,  that  the 
larynx  is  not  primarily  concerned  in  their  production  ;  and  this  has  been  fully 
established  by  the  following  experiment.     A  flexible  tube  was  introduced  by 
M.  Deleau  through  his  nostril  into  the  pharynx,  and  air  was  impelled  by  it 
into  the  fauces  ;  then,  closing  the  larynx,  he  threw  the  fauces  into  the  differ- 
ent positions  requisite  for  producing  articulate  sounds,  when  the  air  impelled 
through  the  tube  became  an  audible  whisper.     The  experiment  was  repeated, 
with  this  variation, — that  laryngeal  sounds  were  allowed  to   pass   into  the 
fauces ;  and  each  articulated  letter  was  then  heard  double,  in  a  proper  voice 
and  in  a  whisper. 

614.  That  the  Vowels  are  produced  by  simple  modifications  in  the  form 
of  the  external  passages,  is  easily  proved,  both  by  observation  and  by  imita- 
tive experiment.     When  the  mouth  is  opened  wide,  the  tongue  depressed, 
and  the  velum  palati  elevated,  so  as  to  give  the  freest  possible  exit  to  the 
voice,  the  vowel  a  in  its  broadest  form  (as  in  ah)  is  sounded.*    On  the  other 
hand,  if  the  oral  aperture  be  contracted,  the  tongue  being  still  depressed,  the 
sound  oo  (the  continental  u)  is  produced.     If  attention  be  paid  to  the  state  of 
the  buccal  cavity,  during  the  pronunciation  of  the  different  vowel  sounds,  it 
will  be  found  to  undergo  a  great  variety  of  modifications,  arising  from  varieties 
of  position  of  the  tongue,  the  cheeks,  the  lips,  and  velum  palati.     The  posi- 

*  Thi^  sound  of  the  vowel  a  is  scarcely  used  in  our  language,  though  very  common  in 
most  of  the  continental  tongues ;  the  nearest  approach  to  it  in  English  is  the  a  in  far  :  but 
this  is  a  very  perceptible  modification,  tending  towards  au. 


466  OF  THE  VOICE  AND  SPEECH. 

tion  of  the  tongue  is,  indeed,  one  of  the  primary  conditions  of  the  variation 
of  the  sound  ;  for  it  may  be  easily  ascertained  that,  by  peculiar  inflexions  of 
this  organ,  a  great  diversity  of  vowel  sounds  may  be  produced,  the  other  parts 
remaining  the  same.  Still  there  is  a  certain  position  of  all  the  parts,  which 
is  most  favourable  to  the  formation  of  each  of  these  sounds  ;  but  this  could 
not  be  expressed  without  a  lengthened  description.  The  following  table, 
slightly  altered  from  that  of  Kempelen,  expresses  the  relative  dimensions  of 
the  buccal  cavity  and  of  the  oral  orifice,  for  some  of  the  principal  of  these ; 
the  number  5  expressing  the  largest  size,  and  the  others  in  like  proportion : — 

Vowel.  Sound.  Size  of  oral  opening.  Size  of  buccal  cavity. 

a  as  in  ah  5  5 

a  as  in  name  4  2 

e  as  in  theme  3  1 

o  as  in  cold  2  4 

oo  as  in  cool  1  5 

These  are  the  sounds  of  the  five  vowels,  a,  e,  i,  o,  u,  in  most  Continental 
languages  ;  an(J  it  cannot  but  be  admitted,  that  the  arrangement  is  a  much  more 
natural  one  than  that  of  our  own  vowel  series.  The  English  a  has  three  dis- 
tinct sounds  capable  of  prolongation:* — the  true  broad  a  of  ah,  slightly  modi- 
fied in  far;  the  a  of  fate,  corresponding  to  the  e  of  French;  and  the  a  of  fall, 
which  should  be  really  represented  by  au.  This  last  is  a  simple  sound,  though 
commonly  reckoned  as  a  diphthong.  In  Kempelen's  scale,  the  oral  orifice 
required  to  produce  it  would  be  about  3,  and  the  size  of  the  buccal  cavity  4.t 
On  the  other  hand,  the  sound  of  the  English  i  cannot,  like  that  of  a  true  vowel, 
be  prolonged  ad  libitum;  it  is  in  fact  a  sort  of  Diphthong,  resulting  from  the 
transition  from  a  peculiar  indefinite  murmur  to  the  sound  of  e,  which  takes 
its  place  when  we  attempt  to  continue  it.  The  sound  oy  or  oi,  as  in  oil, 
is  a  good  example  of  the  true  diphthong;  being  produced  by  the  transition 
from  au  to  e.  In  the  same  manner,  the  diphthong  ou,  which  is  the  same  with 
ow  in  owl,  is  produced  in  the  rapid  transition  from  the  broad  a  of  ah,  to  the 
oo  of  cool. — Much  discussion  has  taken  place  as  to  the  true  character  of  y, 
when  it  commences  a^  word,  as  in  yet,  yawl,  &c. ;  some  having  maintained 
that  it  is  a  consonant,  (for  the  very  unsatisfactory  reason,  that  we  are  in  the 
habit  of  employing  a  rather  than  an,  when  we  desire  to  prefix  the  indefinite 
article  to  such  words,)  whilst  others  regard  it  as  a  peculiar  vowel.  A  slight 
attention  to  the  position  of  the  vocal  organs  during  its  pronunciation,  makes  it 
very  clear,  that  its  sound  in  such  words  really  corresponds  with  that  of  the 
long  (English)  e;  the  pronunciation  of  the  word  yawl  being  the  same  as  that 
of  eaul,  when  the  first  sound  is  not  prolonged,  but  rapidly  transformed  into 
the  second. — The  sound  of  the  letter  tu,  moreover,  is  really  of  the  vowel 
character,  being  formed  in  the  rapid  transition  from  oo  to  the  succeeding 
vowel ;  thus  wall  might  be  spelt  ooall.  Many  similar  difficulties  might  be 
removed,  and  the  conformity  between  spoken  and  written  language  might  be 
greatly  increased  («o  as  to  render  far  more  easy  the  acquirement  of  the  former 
from  the  latter),  by  due  attention  to  the  state  of  the  vocal  organs  in  the  pro- 
duction of  the  simple  sounds. 

*  The  short  vowel  sounds,  as  a  in  fat,  e  in  met,  o  in  pot,  &c.,  are  not  capable  of  prolonga- 
tion. 

•f"  The  mode  of  making  a  determination  of  this  kind  may  here  be  given,  for  the  sake  of 
example.  If  the  broad  a  be  sounded,  the  mouth  and  fauces  being  opened  wide,  and  we 
contract  the  oral  orifice  by  degrees,  at  the  same  time  slightly  elevating  the  point  of  the 
tongue,  we  gradually  come  to  the  sound  of  au;  by  still  further  contracting  the  orifice,  and 
again  depressing  the  tongue,  we  form  oo.  On  the  other  hand,  in  sounding  e,  the  tongue  is 
raised  nearly  to  the  roof  of  the  mouth ;  if  it  be  depressed,  without  the  position  of  the  lips 
being  altered,  au  is  given. 


OF  ARTICULATE  SOUNDS.  467 

615.  It  is  not  very  difficult  to  produce  a  tolerably  good  artificial  imitatijp 
of  the  Vowel  sounds.    This  was  accomplished  by  Kempelen,  by  means  of  an 
India-rubber  ball,  with  an  orifice  at  each  end,  of  which  the  lower  one  was 
attached  to  a  reed;  by  modifying  the  form  of  the  ball,  the  different  vowels 
could  be  sounded  during  the  action  of  the  reed.     He  also  employed  a  short 
funnel-like  tube,  and  obtained  the  different  sounds  by  covering  its  wide  open- 
ing to  a  greater  or  less  extent.     This  last  experiment  has  been  repeated  by 
Mr.  Willis ;  who  has  also  found  that  the  vowel  sounds  might  be  imitated,  by 
drawing  out  a  long  straight  tube  from  the  reed.    In  this  experiment  he  arrived 
at  a  curious  result: — with  a  tube  of  a  certain  length,  the  series  of  vowels,  i,  e, 
a,  o,  u,  was  obtained,  by  gradually  drawing  it  out;  but,  if  the  length  was  in- 
creased to  a  certain  point,  a  further  gradual  increase  would  produce  the  same 
sequence  in  an  inverted  order,  w,  o,  «,  c,  i;  a  still  further  increase  would  pro- 
duce a  return  to  the  first  scale,  and  so  on.     When  the  pitch  of  the  reed  was 
high,  and  the  pipe  short,  it  was  found  that  the  vowels  o  and  u  could  not  be 
distinctly  formed, — the  proper  tone  being  injured  by  the  elongation  of  the 
pipe  necessary  to  produce  them ;  and  this,  Mr.  Willis  remarks,  is  exactly  the 
case  in  the  Human  voice,  most  singers  being  unable  to  pronounce  u  and  o 
upon  their  highest  notes. 

616.  The  most  natural  primary  division  of  the  Consonants  is  into  those 
which  require  a  total  stoppage  of  the  breath  at  the  moment  previous  to  their 
being  pronounced,  and  which,  therefore,  cannot  be  prolonged ;  and  those  in 
pronouncing  which  the  interruption  is  partial,  and  which  can,  like  the  vowel 
sounds,  be  prolonged  ad  libitum.     The  former  have  received  the  designation 
of  explosive;  and  the  latter  of  continuous. — In  pronouncing  the  explosive 
consonants,  the  posterior  nares  are  completely  closed,  so  that  the  exit  of  air 
through  the  nose  is  altogether  prevented;  and  the  current  may  be  checked  in 
the  mouth  in  three  ways, — by  the  approximation  of  the^lips, — by  the  approxi- 
mation of  the  point  of  the  tongue  to  the  front  of  the  palate, — and  by  the  ap- 
proximation of  the  middle  of  the  tongue  to  the  arch  of  the  palate.     In  the  first 
of  these  modes,  we  pronounce  the  letters  6,  and  p;  in  the  second,  d  and  t; 
in  the  third,  the  hard  g,  and  k.     The  difference  between  6,  </,  and  g,  on  the 
one  hand,  and  p,  /,  and  &,*  on  the  other,  seems  to  depend  on  this ; — that  in 
the  former  group  the  approximating  surfaces  are  larger,  and  the  breath  is  sent 
through  them  more  strongly  at  the  moment  of  opening,  than  in  the  latter. — 
The  continuous  consonants  may  be  again  subdivided,  according  to  the  degree 
of  freedom  with  which  the  air  is  allowed  to  make  its  exit,  and  the  compression 
which  it  consequently  experiences,    i.  The  first  class  includes  those,  in  which 
no  passage  of  air  takes  place  through  the  nose,  and  in  which  the  parts  of  the 
mouth  that  produce  the  sound  are  nearly  approximated  together,  so  that  the 
compression  is  considerable.     This  is  the  case  with  v  andjf,  which  are  pro- 
duced by  approximating  the  upper  incisors  to  the  lower  lip;  and  which  stand 
in  nearly  the  same  relation  to  each  other,  as  that  which  exists  between  d  and 
/,  or  b  and/?.     The  sibilant  sounds  z  and  s,  stand  in  nearly  the  same  relation 
to  each  other;  they  are  produced  by  the  passage  of  air  between  the  point  of 
the  tongue  and  the  front  of  the  palate,  the  teeth  being  at  the  same  time  nearly 
closed.     The  simple  sound  sh  is  formed,  by  narrowing  the  channel  between 
the  clorsum  of  the  tongue  and  the  palate ;  the  former  being  elevated  towards 
the    latter,   through   a  considerable   part  of  its  length.      If,  in  sounding  s, 
we  raise  the  point  of  the  tongue  a  very  little,  so  as  to  touch  the  palate,  the 
sound  of  /  is  evolved;  and  in  the  same  manner  d  is  produced  from  z.     This 
class  also  includes  the  th;  which,  being  a  perfectly  simple  sound,  ought  to  be 
expressed  by  a  single  letter,  as  in  Greek;  instead  of  by  two,  of  which  the 

*  For  the  sake  of  proper  comparison,  this  letter  should  be  sounded  not  as  kay  but  as  key. 


468  OP  THE  VOICE  AND  SPEECH. 

combination  does  not  really  produce  anything  like  it.  For  producing  this 
sound,  the  point  of  the  tongue  is  applied  to  the  back  of  the  incisors,  or  to  the 
front  of  the  palate,  as  in  sounding  t;*  but,  whilst  there  is  complete  contact  of 
the  tip,  the  air  is  allowed  to  pass  out  around  it.  n.  In  the  second  class  of 
continuous  consonants,  including  the  letters  ra,  n,  /,  and  r,  the  nostrils  are  not 
closed;  and  the  air  thus  undergoes  very  little  compression,  even  though  the 
passage  of  air  through  the  oral  cavity  is  almost  or  completely  checked.  In 
pronouncing  m  and  n,  the  breath  passes  through  the  nose  alone;  and  the  dif- 
ference of  the  sound  of  these  two  letters,  must  be  due  to  the  variation  in  the 
form  of  the  cavity  of  the  mouth,  which  acts  by  resonance.  The  letter  m  is  a 
labial,  like  b ;  and  the  only  difference  between  the  two  is,  that  in  the  former 
the  nasal  passage  is  open,  whilst  the  mouth  remains  closed;  whilst  in  the 
latter,  the  nose  is  entirely  closed,  and  the  sound  is  formed  at  the  moment  of 
opening  the  mouth.  The  same  correspondence  exists  between  n  and  t,  or  n 
and  g  (the  particular  part  of  the  tongue  approximated  to  the  palate  not  being 
of  much  consequence  in  the  pronunciation  of  n}\  and  hence  it  is  that  the 
transition  from  n  to  t,  or  from  n  to  g,  is  so  easy,  that  the  combinations  nt  and 
ng  are  found  abundantly  in  most  languages.  The  sound  of  /  is  produced,  by 
bringing  the  tip  of  the  /tongue  into  contact  with  the  palate,  and  allowing  the 
air  to  escape  around  it,  at  the  same  time  that  a  vocal  tone  is  generated  in  the 
larynx ;  it  differs,  therefore,  from  th  in  the  position  at  which  the  obstruction 
is  interposed,  as  well  as  in  the  slight  degree  of  the  compression  of  the  air 
which  it  involves.  The  sound  of  the  letter  r  depends  on  an  absolute  vibration 
of  the  point  of  the  tongue,  in  a  narrow  current  of  air  forced  between  the  tongue 
itself  and  the  palate,  m.  The  sounds  of  the  third  class  are  scarcely  to  be 
termed  consonants,  since  they  are  merely  aspirations,  caused  by  an  increased 
force  of  breath.  These  are  A,  and  the  cAt  of  most  foreign  languages  (the 
Greek  %).  The  first  i$  a  simple  aspiration  ;  the  second,  an  aspiration  modified 
by  the  elevation  of  the  tongue,  causing  a  slight  obstruction  to  the  passage  of 
air,  and  an  increased  resonance  in  the  back  of  the  mouth.  This  sound  would 
become  either  g  or  A;,  if  the  tongue,  whilst  it  is  being  produced,  were  carried 
up  to  touch  the  palate.^ 

617.  These  distinctions  come  to  be  of  much  importance,  when  we  apply 
ourselves  to  the  treatment  of  defects  of  articulation.     Great  as  is  the  number 
of  muscles  employed  in  the  production  of  definite  vocal  sounds,  the  number 
is  much  greater  for  those  of  articulate  language  ;  and  the  varieties  of  combina- 
tion, which  we  are  continually  forming  unconsciously  to  ourselves,  would  not 
be  suspected,  without  a  minute  analysis  of  the  separate  actions.     Thus,  in  ut- 
tering the  explosive  sounds,  we  check  the  passage  of  air  through  the  posterior 
nares,  in  the  very  act  of  articulating  the  letter ;  and  yet,  this  important  move- 
ment commonly  passes  unobserved.     We  must  regard  the  power  of  forming 
the  several  articulate  sounds  which  have  been  adverted  to,  and   their  simple 
combinations,  as  so  far  resulting  from  intuition,  that  it  can  in  general  be  more 
readily  acquired  by  early  practice,  than  other  actions  of  the  same  complexity  ; 
so  that  we  may  consider  these  movements  as  having  somewhat  of  the  same 
consensual  character  as  that  which  has  been  attributed  to  the  purely  vocalizing 
actions  (§  611).     But  there  is  in  many  individuals  a  deficiency  of  the  power 
of  rightly  combining  them ;  from  which  Stammering  and  other  imperfections 
result. 

618.  Many  theories  regarding  the   nature  of  Stammering  have  been   pro- 
posed ;  and  there  can  be  little  doubt,  that  the  impediment  may  be  attributed  to 

*  Hence  it  is  easy  to  understand  the  substitution  of  t  or  d,  for  the  English  th,  by  foreigners, 
f  The  English  ch  is  merely  a  combination  of  t  with  sh;  thus  chime  might  be  spelt  tshime. 
j  The  general  classification  proposed  by  Dr.  M.  Hall  is  here  adopted,  with  some  modifica- 
tion as  to  the  details. 


OF  ARTICULATE  SOUNDS.  469 

a  great  variety  of  exciting  causes.  A  disordered  action  of  the  nervous  cen- 
tres must,  however,  be  regarded  as  the  proximate  cause ;  though  this  may  be 
(to  use  the  language  of  Dr.  M.  Hall)  either  of  centric  or  of  excentric  origin, 
— that  is,  it  may  result  from  a  morbid  condition  of  the  ganglionic  centre,  or 
from  an  undue  excitement  conveyed  through  its  afferent  nerves.  When  of 
centric  origin  (and  this  is  probably  the  most  general  case),  the  phenomena  of 
Stammering  and  Chorea  have  a  close  analogy  to  each  other  ;  in  fact,  stammer- 
ing is  frequently  one  of  the  modes  in  which  the  disordered  condition  of  the 
nervous  system  in  Chorea  manifests  itself.  It  is  in  the  pronunciation  of  the 
Consonants  of  the  explosive  class,  that  the  stammerer  experiences  the  greatest 
difficulty.  The  total  interruption  to  the  breath  which  they  occasion,  frequently 
becomes  quite  spasmodic  ;  and  the  whole  frame  is  thrown  into  the  most  dis- 
tressing semi-convulsive  movement,  until  relieved  by  expiration.*  In  the  pro- 
nunciation of  the  continuous  Consonants  of  the  first  class,  the  stammerer 
usually  prolongs  them,  by  a  spasmodic  continuance  of  the  same  action;  and 
there  is,  in  consequence,  an  impeded,  but  not  a  suspended  respiration.  The 
same  is  the  case  with  the  /  and  r  in  the  second  class.  In  pronouncing  the  m 
and  n,  on  the  other  hand,  as  well  as  the  aspirates  and  vowels,  it  is  sometimes 
observed  that  the  stammerer  prolongs  the  sound,  by  a  full  and  exhausting  ex- 
piration. In  all  these  cases,  then,  it  seems  as  if  the  muscular  sense,  resulting 
from  each  particular  combination  of  actions,  became  the  stimulus  to  the  invo- 
luntary prolongation  of  that  action.  In  some  instances,  it  is  possible  that  the 
defect  may  result  from  malformation  of  the  parts  about  the  fauces,  producing 
an  abnormal  stimulus  of  this  kind,  in  some  particular  positions  of  the  organ ; 
and  such  cases  may  be  really  benefited  by  an  operation  for  the  removal  of 
these  parts.  But  the  effect  of  the  operation  is  evidently  for  the  most  part  upon, 
the  Nervous  System  ;  and  it  coincides  with  what  may  be  frequently  observed, 
— that  the  Stammering  is  increased  under  any  unusual  excitement,  especially 
of  the  Emotional  kind. 

619.  The  method  proposed  by  Dr.  Arnott  for  the  prevention  of  Stammer- 
ing, consists  in  the  connection  of  all  the  words  by  a  vocal  intonation,  in  such 
a  manner,  that  there  shall  never  be  an  entire  stoppage  of  the  breath.  It  is 
justly  remarked  by  Miiller,  however,  that  this  plan  may  afford  some  benefit, 
but  cannot  do  everything;  since  the  main  impediment  occurs  in  the  middle  of 
words  themselves.  One  important  remedial  means,  on  which  too  much  stress 
cannot  be  laid,  is  to  study  carefully  the  mechanism  of  the  articulation  of  the 
difficult  letters,  and  to  practise  their  pronunciation  repeatedly,  slowly,  and 
analytically.  The  patient  would  at  first  do  well  to  practise  sentences,  from 
which  the  explosive  consonants  are  omitted ;  his  chief  difficulty,  arising  from 
1he  spasmodic  suspension  of  the  expiratory  movement,  being  thus  avoided. 
Having  mastered  these,  he  may  pass  on  to  others,  in  which  the  difficult  letters 
are  sparingly  introduced ;  and  may  finally  accustom  himself  to  the  use  of 
ordinary  language.  One  of  the  chief  points  to  be  aimed  at,  is  to  make  the 
patient  feel  that  he  has  command  over  his  muscles  of  articulation ;  and  this 
is  the  best  done,  by  gradually  leading  him  from  that  which  he  finds  he  can 
do,  to  that  which  he  fears  he  cannot.  The  fact  that  stammering  people  are 
able  to  sing  their  words  better  than  to  speak  them,  has  been  usually  explained 
on  the  supposition  that,  in  singing,  the  glottis  is  kept  open,  so  that  there  is 
less  liability  to  spasmodic  action ;  if,  however,  as  here  maintained,  the  spas- 
modic action  is  not  in  the  larynx,  but  in  the  velum  palati  and  the  muscles  of 
articulation,  the  difference  must  be  due  to  the  direction  of  the  attention  rather 

*  By  Dr.  Arnott  this  interruption  is  represented  as  taking  place  in  the  larynx ;  that  such  is 
not  the  case,  the  Author  believes  that  a  little  attention  to  the  ordinary  phenomena  of  voice  will 
satisfactorily  prove. 

40 


470  INFLUENCE  OF  THE  NERVOUS  SYSTEM 

to  the  muscles  of  the  larynx  than  to  those  of  the  mouth.  Every  one  must 
have  noticed  how  much  the  impediment  of  Stammerers  is  increased,  when 
they  are  particularly  anxious  to  speak  fluently. 


CHAPTER    IX. 

INFLUENCE  OF  THE  NERVOUS  SYSTEM  ON  THE  ORGANIC  FUNCTIONS. , 

620.  OF  the  modes  in  which  the  Nervous  System  influences  the  Organic 
Functions,  a  part  have  been  already  considered.     It  has  been  shown  (§  183) 
that  it  is  concerned  in  providing  the  conditions,  either  immediate  or  remote, 
under  which  alone  these  functions  can  be   performed ;  so  that,  when  its  ac- 
tivity ceases,  they  cannot  be  much  longer  maintained.     The*  first  mode  in 
which  it  operates  upon  them  is,  therefore,  by  producing  sensible  movements 
in  the  Muscles  or  other  contractile  organs,  which  can  be  stimulated  to  action 
through  it ;  and  the  contractions  thus  induced  have  usually  an  important  effect 
upon  them,  which  varies,  however,  in  each  individual  case.     Thus,  the  pro- 
cess of  Nutritive  Absorption,  which  is  the  very  first  stage  in  the  operations  of 
Vegetative  Life,  and  which  is  accomplished  in  Plants  by  the  accidental  con- 
tact of  the  alimentary  materials  with  the  radical  fibres,  cannot  take  place  in 
Animals,  until  the  muscular  apparatus  of  prehension  has  been  set  in  action  by 
the  Will,  that  of  deglutition  by  the  Reflex  Function,  and  that  of  the  intestinal 
canal  by  direct  stimulation, — the  two  former  kinds  of  contraction  being  ac- 
complished entirely  through  the  Nervous  System,  and  the  latter  being  influ- 
enced by  it.     The  Circulation  of  Blood,  too,  is  chiefly  effected,  in  the  higher 
Animals  at  least,  by  the  contractions  of  a  muscular  organ  of  impulsion ;  which 
contractions,  though  not  essentially  dependent  upon   Nervous    action,  are 
nevertheless  greatly  influenced  by  it.     The  function  of  Respiration,  again, 
cannot  be  maintained  even  for  a  short  time,  without  muscular  movement,  ex- 
cited through  the  Nervous  System.     The  functions  of  Nutrition  and  Secre- 
tion are  more  independent  of  it ;  taking  place,  as  in  Plants,  so  long  as  the 
conditions  are  supplied  by  other  functions,  without  any  sensible  movements 
being  actually  concerned  in  them.     We  shall  presently  see,  however,  that 
they  are  subject  to   a  peculiar  kind  of  Nervous  influence,  which  does  not 
manifest  itself  in  obvious  movement,  but  in  altered  performance  of  the  inti- 
mate processes  themselves ;  showing  itself  in  the  character  of  the  organized 
tissue,  or  of  the  secreted  product.     The  act  of  Excretion  is,  like  ingestion, 
entirely  performed  by  Muscular  movement,  dependent  upon  Nervous  agency. 
Now,  wherever  such  movements  of  distant  organs  are  usually  performed  in 
connection  with  each  other,  there  is  an  obvious  channel  for  one  kind  of  sym- 
pathy between  them ;  an  interesting  example  of  this,  is  the  contraction  of  the 
Uterus,  which  may  be  frequently  made  to  occur,  when  that  organ  is  in  a  re- 
laxed state  at  the  conclusion  of  labour,  by  applying  suction  or  other  irritation 
to  the  nipple. 

621.  Sympathetic  movements  of  this  kind  may  be  excited  either  through 
the  Cerebro-Spinal,  or  the  Ganglionic  systems ;  and  we  shall  be  guided  in 
our  determination  of  their  channel  in  each  particular  case,  by  the  distribution 
of  these  systems  respectively  to  the  organ  affected.     The  sympathetic  move- 
ments of  the  Muscles  of  Animal  life  appear  to  be  chiefly,  if  not  entirely,  ex- 


ON  THE  ORGANIC  FUNCTIONS.  471 

cited  through  the  Cerebro-Spinal  system ;  whilst  those  of  the  contractile  tis- 
sues of  the  Viscera  (§  234)  are  probably  excited  through  nerves,  which, 
though  connected  with  the  Cerebro-Spinal  system,  act  under  peculiar  condi- 
tions, and  are  commonly  spoken  of  as  forming  part  of  the  Sympathetic 
system.  It  has  been  shown  (§§  388 — 393)  that  all  the  contractile  organs, 
which  may  be  excited  through  the  Sympathetic  or  Visceral  system  of  nerves, 
may  also  be  made  to  act  by  stimuli  applied  to  the  roots  of  the  Spinal  nerves ; 
but  that  each  Cerebro-Spinal  fibre  appears  to  pass  through  several  Ganglia, 
before  being  distributed  to  the  organs  which  it  supplies. 

a.  Many  speculations  have  been  hazarded,  as  to  the  reasons  why  the  Visceral  nerves 
are  destitute  of  sensibility ;  and,  at  the  time  when  the  Sympathetic  was  supposed  to  be 
merely  an  offset  from  the  Cerebro-Spinal  system,  it  was  imagined  that  the  use  of  the  gan- 
glia upon  the  roots  of  the  spinal  nerves  was  to  "  cut  off  sensation"  from  those  concerned  in 
the  "  vital  and  involuntary  motions."  The  influence  of  Bichat's  ingenious  hypothesis, — that 
the  Sympathetic  system  is  complete  and  independent,  ministering  to  the  functions  of  Or- 
ganic Life,  as  the  Cerebro-Spinal  does  to  those  of  Animal  Life — for  a  time  caused  this  idea 
to  be  abandoned.  Since,  however,  it  has  been  anatomically  proved,  that  a  large  proportion 
of  the  filaments  of  the  visceral  nerves  are  derived  from  the  Spinal  cord,  this  opinion  has 
been  revived,  in  a  somewhat  modified  form.*  Nevertheless  the  evidence  in  its  support  is 
somewhat  vague ;  especially  if  the  truth  of  the  doctrine  formerly  urged, — that  the  Spinal 
Cord  is  not  itself  a  centre  of  sensation, — be  admitted.  For  it  is  only  necessary  to  suppose, 
that  the  white  fibres  of  the  Sympathetic  nerve  terminate  in  the  true  Spinal  Cord,  without 
proceeding  to  the  Brain,  to  have  an  explanation  of  the  absence  of  sensory  endowments  in 
the  organs  to  which  they  are  distributed,  and  of  the  complete  removal  of  the  muscles  sup- 
plied by  their  motor  nerves,  from  voluntary  control.  That  a  few  fibres,  of  which  the  actions 
cannot  be  excited  under  ordinary  circumstances,  pass  on  to  the  Brain,  would  seem  probable 
from  the  fact  of  the  sensibility  of  some  parts,  in  disease,  which  are  totally  insensible  in  their 
normal  condition  j — a  fact  in  the  explication  of  which,  the  hypothesis  just  alluded  to  affords 
no  assistance. 

622.  It  appears,  then,  that  it  may  be  stated  as  a  general  proposition,  that 
all  the  evident  movements  which  can  be  excited,  by  irritation  applied  to  one 
part  of  the  body,  in  the  contractile  organs   or  tissues  of  another,  are  really 
effected  through  the  true  Spinal  Cord ;  whether  the  contractile  organ  be  a 
powerful  muscle,  or  a  thin  and  feeble  layer  of  fibres  around  a  blood-vessel  or 
duct.     Upon  the  reasons  why  the  fibres  of  the  Visceral  nerves  should  be  so 
peculiarly  separated  from  the  rest,  we  can  at  present  only  speculate ;  but  it 
may  not  be  considered  improbable  that,  by  their  peculiar  plexiform  arrange- 
ment in  the  various  ganglia  through  which  they  pass,  connections  are  estab- 
lished between  remote  organs,  which  tend  to  bring  their  actions  into  closer 
relation  with  each  other,  than  would  otherwise  be  the  case.     The  existence 
of  such  connections  for  the  purpose  of  harmonizing  the  several  movements 
of  the  Viscera,  which  are  concerned  in  the  various  and  complex  operations  of 
Digestion  and  its  attendant  processes,  may  be  inferred  from  the  perfect  con- 
formity which  exists  between  them,  during  all  their  different  states  of  regular 
action ;  and  still  more,  perhaps,  from  the  phenomena  of  their  disordered  con- 
ditions.    The  study  of  these  Sympathies  is  one  of  those  departments  of  Phy- 
siology, in  which  it  maybe  expected  that  much  will  be  gained  by  patient  and 
well-directed  investigation. 

623.  The  movements  immediately  concerned  in  the  Organic  Functions,  how- 
ever, are  not  influenced  by  Reflex  action  alone,  but  also  by  Emotional  condi- 
tions of  the  mind.     This  is  most  obvious  in  regard  to  the  Heart.     Every  one 
must  have  experienced  the  disturbance  of  its  pulsations,  consequent  upon  ex- 
citement of  the  feelings,  of  almost  any  description.    But  other  organs  probably 
experience  similar  changes,  although  of  a  less  manifest  character.     It  is  well 
known  that  the  Sympathetic  system  is  largely  distributed  upon  the  trunks  of 

*  See  Dr.  Alison  on  the  Nerves  of  the  Orbit;  Edin.  Phil.  Trans.,  vol.  xv.;  and  Med.  Gaz. 
vol.  xxviii.  p.  378. 


472  INFLUENCE  OF  THE  NERVOUS  SYSTEM 

the  blood-vessels,  accompanying  them  to  their  minutest  ramifications ;  and  it 
will  be  hereafter  shown  (§  732),  that  the  fibrous  tissue  of  the  walls  of  the  ar- 
teries is  probably  susceptible  of  influence  from  these  nerves.  There  can  be 
little  doubt,  therefore,  that  they  constitute  the  channel  through  which  Emo- 
tions operate,  in  producing  sudden  distension  of  particular  parts  of  the  vascu- 
lar system,  as  in  blushing,  erection,  &c.  And  to  the  same  kind  of  influence, 
more  gradually  exerted,  we  may  very  probably  attribute  the  regulation  of  the 
supply  of  blood  which  passes  to  different  secreting  organs,  in  varying  condi- 
tions of  the  system. 

624.  But  the  Sympathetic  System  does  not  consist  of  Cerebro-Spinal  fila- 
ments alone ;  nor  is  its  influence  exerted  only  upon  the  motor  or  contractile 
tissues  of  the  body.  There  is  good  evidence,  that  the  Nervous  System  has 
an  immediate  action  upon  the  molecular  changes,  which  constitute  the  func- 
tions of  Nutrition,  Secretion,  &c. ;  and  the  channel  of  such  influence  is  pro- 
bably to  be  found  in  that  system  of  peculiar  fibres  formerly  described  (§  244), 
which  constitutes  a  considerable  proportion  of  the  Visceral  nerves,  existing 
much  more  sparingly  in  most  of  the  Cerebro-Spinal,  but  being  abundant  in 
the  Fifth  pair.  There  is  no  valid  reason,  however,  to  believe  that  any  of  the 
processes  of  Nutrition  and  Secretion  are  dependent  upon  this,  or  any  other, 
kind  of  Nervous  agency.  These  processes  go  on  with  great  rapidity  and 
energy  in  the  Vegetable  kingdom,  in  which  nothing  approaching  to  a  Nervous 
System  exists ;  and  in  the  Animal  kingdom  they  take  place  with  equal  vigour, 
long  before  the  least  vestige  of  it  appears.  The  Embryological  researches 
of  Dr.  Barry  have  fully  proved,  that  in  the  earliest  condition  of  foetal  life,  the 
germ  consists  but  of  a  congeries  of  cells,  which  have  all  originated  in  a  single 
one ;  and  from  this  mass,  the  several  tissues  are  gradually  generated,  by  a 
process  which  is  technically  called  histological*  transformation, — one  set  of 
cells  being  converted  into  muscular  tissue,  anther  into  nervous  tissue,  another 
into  mucous  membrane,  and  so  on.  Now  since  this  is  the  case,  it  is  evident 
that  all  these  processes  of  development  must  take  glace,  in  virtue  of  the  inhe- 
rent properties  of  the  primary  tissue  itself;  since  no  nervous  influence  can  be 
supposed  to  operate,  before  nerves  are  called  into  existence.  Throughout  the 
Animal  body,  it  may  be  observed  that,  the  more  Vegetative  the  nature  of  any 
function,  the  less  is  it  connected  with  the  Nervous  System ;  and  all  the  ex- 
periments, which  have  been  regarded  as  proving  that  the  Organic  functions 
are  dependent  upon  Nervous  influence,  are  really  explicable,  fully  as  well, 
upon  the  supposition  that  they  are  capable  of  being  affected  by  it,  either  in 
the  way  of  excitement  or  retardation  (see  §  415).  Moreover,  there  is  abundant 
evidence,  that  Secretion  may  take  place  after  the  death  of  the  general  system, 
through  the  persistence  of  certain  molecular  changes,  of  which  the  essential 
conditions  are  not  immediately  altered;  thus  Mr.  T.  Bell  mentions  that,  in 
dissecting  the  poison  apparatus  of  a  Rattle-snake,  which  had  been  dead  for 
some  hours,  the  poison  continued  to  be  secreted,  so  fast  as  to  require  being 
occasionally  dried  off.  This  is  precisely  what  might  have  been  anticipated, 
from  the  independent  power  of  growth  in  the  secreting  cells  ;  and  other  acts 
of  Nutrition  are  recorded  to  have  occurred  under  similar  circumstances.  In 
such  a  case,  the  Animal  body  is  reduced  to  the  condition  of  a  Plant ;  since 
the  influence  of  the  Nervous  system  must  then  be  entirely  extinct.  Upon 
those  who  maintain  that  Nervous  agency  is  a  condition  essential  to  those  mo- 
lecular actions,  of  which  Nutrition  and  Secretion  consist,  it  is  incumbent, 
therefore,  to  offer  some  more  unexceptionable  proof  of  their  position  than  has 
yet  been  given ;  since  their  doctrine  is  opposed  by  so  many  considerations  of 
great  weight. 

*  This  term  is  used  in  contradistinction  to  morphological,  which  applies  to  the  alterations 
in  the  form  of  the  several  parts  of  the  embryo. 


ON  THE  ORGANIC  FUNCTIONS.  473 

625.  That  many  of  the  Organic  Functions,  however,  are  directly  influenced 
by  the  Nervous  System,  is  a  matter  which  does  not  admit  of  dispute  ;  and 
this  influence,  exerted  sometimes  in  exciting,  sometimes  in  checking,  and 
sometimes  in  otherwise  modifying  them,  may  well   be    compared   to  that, 
which  the  hand  and  heel  of  the  rider  have  upon  his  horse,  or  which  the  en- 
gine-driver exerts  over  a  locomotive.    It  is  most  remarkably  manifested  in  the 
result  of  severe  injury  of  the  Nervous  centres, — such  as  concussion  of  the 
Brain,  or  of  the  Solar  plexus  (§  580) ;  for  this  does  not  merely  produce  a  sus- 
pension of  the  respiratory  and  other  movements,  which  minister  to  the  or- 
ganic functions,  and  hence  a  gradual  stagnation  of  the  latter, — but  a  sudden 
and  complete  cessation  of  the  whole  train  of  action  ;  which  cannot  be  attri- 
buted to  any  other  cause  than  a  positive  depressing  influence  of  some  kind, 
propagated  through  the  Nervous   System.     It  will  hereafter  appear  (§  701), 
that  in  such  cases  even  the  vitality  of  the  Blood  is  often  affected;  the  usual 
coagulation  not  taking  place  after  death,  so  long,  at  least,  as  the  blood  remains 
within  the  vessels.     A  similar  general  depression  may  result  from  Mental 
Emotion,  operating   through    the  same  channel ;  but  this  more  commonly 
has  rather  a  local  action,  or  operates  more  gradually. — The  influence  of  the 
Nervous  System  is  often  especially  exerted,  in  giving  temporary  excitement 
to  a  Secreting  process ;  which  need  not  be  kept  in  constant  activity,  or  of 
which  circumstances  may  occasionally  require   an   increase.     This-   is  the 
case,  for  example,  in  regard  to  the  secretions  connected  with  the  process  of 
digestion, — the  Saliva,  Gastric  fluid,  Bile,  Pancreatic  fluid,  &c. ;  all  of  these 
being  excited  by  the  contact  of  the  substances   on  which  they  act,  with  the 
surfaces  on  which  their  respective  ducts  open.     The  secretion  of  Milk,  again, 
in  a  nursing  female,  may  be  excited  by  irritation  of  the  nipple  ;  and  the  de- 
termination of  blood  to  the  Mammae  during  pregnancy,  must  be  due  to  in- 
creased action  in  the  part,  excited  by  the  changes  occurring  in  the  Uterus, 
which  can  scarcely  operate  otherwise  than  through  the  Nervous  System.    No 
other  channel  of  influence  can  be  well  imagined  for  most  of  these  operations, 
than  the  Sympathetic  system  of  Nerves  ;  since  the  organs  in  question  are  for 
the  most  part  supplied  by  it.     There  is   an  apparent  exception,  however,  in 
the  case  of  the  Salivary  and  Lachrymal  glands,  which  are  supplied  by  the 
Fifth  pair ;  but  this  nerve  contains  so  many  organic  filaments,  and  is  so  inti- 
mately connected  with  the  Sympathetic,  as  evidently  to  supply  (in  the  head) 
the  place  of  a  separate  ganglionic  system.     It  is  by  Nervous  influence,  that 
the  mucous  secretion  covering  the  membranes  is  caused  to  be  regularly  formed 
for  their  protection  ;  for  it  is  shown,  by  pathological  facts,  that,  when  this 
influence  is  interrupted,  and  the  secretion  is  no  longer  supplied,  the  membrane 
losing  its  protection,  is  irritated  by  the  air  or  the  fluids  with  which  it  may  be 
in  contact,  and  passes  into  an  inflammatory  condition.     This  is  the  explana- 
tion of  the  fact,  which  has  been  well  ascertained,  that  the  Eye  is  liable  to 
suppurate  when  the  Fifth  pair  has  been  divided ;  and  that  the  mucous  Mem- 
brane of  the  bladder  becomes  diseased  in  Paraplegia. 

626.  The  influence  of  particular  conditions  of  the  mind,  in  exciting  various 
Secretions,  is  a  matter  of  daily  experience.     The  flow  of  Saliva,  for  exam- 
ple, is  stimulated  by  the  idea  of  food,  especially  that  of  a  savoury  character. 
The  Lachrymal  secretion,  again,  which  is  continually  being  formed  to  a  small 
extent,  for  the  purpose  of  bathing  the  surface  of  the  eye,  is  poured  out  in 
great  abundance  under  the  moderate  excitement  of  the  emotions,  either  of 
joy,  tenderness,  or  grief.    It  is  checked,  however,  by  violent  emotions  ;  hence 
in  intense  grief  the  tears  do  not  flow.     It  is  a  well-known  proof  of  moderated 
sorrow,  when  this  takes  place ;  tears,  however,  do  not  bring  relief,  as  is  com- 
monly believed,  but  they  indicate  that  it  has  been  brought.     Violent  emotion 
may  also  suspend  the  Salivary  secretion ;  as  is  shown  by  the  well-known  test, 

40* 


474  INFLUENCE  OF  THE  NERVOUS  SYSTEM 

often  resorted  to  in  India,  for  the  discovery  of  a  thief  amongst  the  servants  of 
a  family, — that  of  compelling  all  the  parties  to  hold  a  certain  quantity  of  rice 
in  the  mouth  during  a  few  minutes, — the  offender  being  generally  distin- 
guished by  the  comparative  dryness  of  his  mouthful,  at  the  end  of  the  ex- 
periment. The  influence  of  the  emotion  of  love-of-offspring,  in  increasing 
the  secretion  of  Milk,  is  well  known.  The  formation  of  this  fluid  is  con- 
tinually going  on  during  the  period  of  lactation  ;  but  it  is  greatly  increased 
by  the  sight  of  the  infant,  or  even  by  the  thought  of  him,  especially  when  as- 
sociated with  the  idea  of  suckling  :  this  gives  rise  to  the  sudden  rush  of  blood 
to  the  gland,  which  is  known  by  nurses  as  the  draught,  and  which  occasions 
a  greatly-increased  secretion.  The  strong  desire  to  furnish  milk,  together 
with  the  irritation  of  the  gland  through  the  nipple,  has  often  been  effectual 
in  producing  the  secretion  in  girls  and  old  women,  and  even  in  men  (§  853,  d). 
The  quantity  of  the  Gastric  secretion  is  increased  by  exhilaration ;  at  least 
if  we  may  judge  from  the  increase  of  the  digestive  powers,  under  such  cir- 
cumstances. Freedom  from  mental  anxiety  favours  the  secretion  of  fat ; 
whilst  continual  solicitude  effectually  checks  the  disposition.  It  has  been 
stated  that  total  despair  has  an  equal  tendency,  with  absence  of  care,  to  pro- 
duce this  effect ;  persons  left  long  to  pine  in  condemned  cells,  without  a  shadow 
of  hope,  frequently  becoming  remarkably  fat  in  spite  of  their  slender  fare.* 
The  odoriferous  secretion  of  the  Skin,  which  is  much  more  powerful  in  some 
individuals  than  in  others,  is  increased  under  the  influence  of  certain  mental 
emotions  (as  fear  or  bashfulness),  and  commonly  also  by  sexual  desire.  The 
Sexual  secretions  themselves  are  strongly  influenced  by  the  condition  of  the 
mind.  When  it  is  frequently  and  strongly  directed  towards  objects  of  passion, 
these  secretions  are  increased  in  amount  to  a  degree  which  may  cause  them 
to  be  a  very  injurious  drain  on  the  powers  of  the  system.  On  the  other  hand, 
the  active  employment  of  the  mental  powers  on  other  objects,  has  a  tendency 
to  render  less  active,  or  even  to  check  altogether,  the  processes  by  which  they 
are  elaborated.! 

*  Fletcher's  Physiology,  Part  II.,  6,  p.  11. 

•}•  This  is  a  simple  physiological  fact,  but  of  high  moral  application.  The  Author  would 
say  to  those  of  his  younger  readers,  who  urge  the  wants  of  Nature  as  an  excuse  for  the  il- 
licit gratification  of  the  sexual  passion:  "  Try  the  effects  of  close  mental  application  to  some 
of  those  ennobling  pursuits,  to  which  your  profession  introduces  you,  in  combination  with 
vigorous  bodily  exercise  (for  the  effects  of  which  see  §  470),  before  you  assert  that  the  ap- 
petite is  unrestrainable,  and  act  upon  that  assertion.  Nothing  tends  so  much  to  increase 
the  desire,  as  the  continual  direction  of  the  mind  towards  the  objects  of  its  gratification.  The 
following  observations,  which  the  Author  believes  to  be  strictly  correct,  are  extracted  from 
a  valuable  little  work  (anonymous)  entitled,  "Be  not  deceived,"  addressed  to  Young  Men; 
they  are  directed  to  those  who  maintain  that,  the  married  state  being  natural  to  Man,  illicit 
intercourse  is  necessary  for  those  who  are  prevented  by  circumstances  from  otherwise  grati- 
fying the  sexual  passion.  "  When  the  appetite  is  naturally  indulged,  that  is,  in  marriage,  the 
necessary  energy  is  supplied  by  the  nervous  stimulus  of  its  natural  accompaniment  of  love 
before  referred  to,  which  prevents  the  injury  which  would  otherwise  arise  from  the  in- 
creased expenditure  of  animal  power :  and  in  like  manner,  also,  the  function  being  in  itself 
grateful,  this  personal  attachment  performs  the  further  necessary  office  of  preventing  im- 
moderate indulgence,  by  dividing  the  attention,  through  the  numerous  other  sources  of  sym- 
pathy and  enjoyment  which  it  simultaneously  opens  to  the  mind.  But,  when  the  appetite 
is  irregularly  indulged,  that  is  in  fornication,  for  want  of  the  healthful  vigour  of  true  love, 
its  energies  become  exhausted ;  and  from  the  want  of  the  numerous  other  sympathetic 
sources  of  enjoyment  in  true  love,  in  similar  thoughts,  common  pursuits,  and  above  all  in 
common  holy  hopes,  the  mere  gross  animal  gratification  of  lust  is  resorted  to  with  unnatural 
frequency,  and  thus  its  powers  become  still  further  exhausted,  and,  therefore,  still  more 
unsatisfying,  while,  at  the  same  time,  a  habit  is  thus  created,  and  these  jointly  cause  an 
increased  craving;  and  the  still  greater  deficiency  in  the  satisfaction  experienced  in  its  indulg- 
ence further,  continually,  ever  in  a  circle,  increases — the  habit,  demand,  indulgence,  conse- 
quent exhaustion,  diminished  satisfaction,  and  again  demand, — till  the  mind  and  body  alike 
become  disorganized."  Such  considerations  as  these  may,  to  some  persons,  appear  misplaced 


ON  THE  ORGANIC  FUNCTIONS.  475 

627.  No  secretion  so  evidently  exhibits  the  influence  of  the  depressing 
Emotions,  as  that  of  the  Mammae  ;  but  this  may  be  partly  due  to  the  fact,  that 
the  digestive  system  of  the  Infant  is  a  more  delicate  apparatus  for  testing  the 
qualities  of  that  secretion,  than  any  which  the  Chemist  can  devise ;  affording 
proof,  by  disorder  of  its  function,  of  changes  in  the  character  of  the  Milk, 
which  no  examination  of  its  physical  properties  could  detect.  The  following 
remarks  on  this  subject  are  abridged  from  Sir  A.  Cooper's  valuable  work  on 
the  Breast.  "  The  secretion  of  milk  proceeds  best  in  a  tranquil  state  of 
mind,  and  with  a  cheerful  temper  :  then  the  milk  is  regularly  abundant,  and 
agrees  well  with  the  child.  On  the  contrary,  a  fretful  temper  lessens  the 
quantity  of  milk,  makes  it  thin  and  serous,  and  causes  it  to  disturb  the  child's 
bowels,  producing  intestinal  fever  and  much  griping.  Pits  of  anger  produce 
a  very  irritating  milk,  followed  by  griping  in  the  infant,  with  green  stools. 
Grief  has  a  great  influence  on  lactation,  and  consequently  upon  the  child. 
The  loss  of  a  near  and  dear  relation,  or  a  change  of  fortune,  will  often  so 
much  diminish  the  secretion  of  milk,  as  to  render  adventitious  aid  necessary 
for  the  support  of  the  child.  Anxiety  of  mind  diminishes  the  quantity,  and 
alters  the  quality  of  the  milk.  The  reception  of  a  letter  which  leaves  the 
mind  in  anxious  suspense,  lessens  the  draught,  and  the  breast  becomes  empty. 
If  the  child  be  ill,  and  the  mother  is  anxious  respecting  it,  she  complains  to 
her  medical  attendant  that  she  has  little  milk,  and  that  her  infant  is  griped, 
and  has  frequent  green  and  frothy  motions.  Fear  has  a  powerful  influence 
on  the  secretion  of  milk.  I  am  informed  by  a  medical  man  who  practices 
much  among  the  poor,  that  the  apprehension  of  the  brutal  conduct  of  a 
drunken  husband,  will  put  a  stop  for  a  time  to  the  secretion  of  milk.  When 
this  happens,  the  breast  feels  knotted  and  hard,  flaccid  from  the  absence  of 
milk,  and  that  which  is  secreted  is  highly  irritating,  and  some  time  elapses 
before  a  healthy  secretion  returns.  Terror,  which  is  sudden  and  great  fear, 
instantly  stops  this  secretion."  Of  this,  two  striking  instances,  in  which  the 
secretion,  although  previously  abundant,  was  completely  arrested  by  this  emo- 
tion, are  detailed  by  Sir  A.  C.  "  Those  passions  which  are  generally  sources 
of  pleasure,  and  which,  when  moderately  indulged,  are  conducive  to  health, 
will,  when  carried  to  excess,  alter,  and  even  entirely  check  the  secretion  of 
milk." 

a.  The  following  is  perhaps  the  most  remarkable  instance  on  record,  of  the  effect  of  strong 
mental  excitement  on  the  Mammary  secretion ;  the  event  could  hardly  be  regarded  as  more 
than  a  simple  coincidence,  if  it  were  not  borne  out  by  the  less  striking,  but  equally  decisive 
facts  already  mentioned.  "A  Carpenter  fell  into  a  quarrel  with  a  Soldier  billeted  in  his  house, 
and  was  set  upon  by  the  latter  with  his  drawn  sword.  The  wife  .of  the  carpenter  at  first 
trembled  from  fear  and  terror,  and  then  suddenly  threw  herself  furiously  between  the  combat- 
ants, wrested  the  sword  from  the  soldier's  hand,  broke  it  in  pieces,  and  threw  it  away.  During 
the  tumult,  some  neighbours  came  in  and  separated  the  men.  While  in  this  state  of  strong 
excitement,  the  mother  took  up  her  child  from  the  cradle,  where  it  lay  playing,  and  in  the 
most  perfect  health,  never  having  had  a  moment's  illness;  she  gave  it  the  breast,  and  in  so 


in  a  Physiological  Treatise — yet  the  Author  feels  sure  that,  by  his  well-judging  readers,  he 
will  not  be  blamed  for  adverting  to  this  subject,  or  for  the  introduction  of  the  above  quota- 
tion from  a  writer,  of  whom  he  has  no  personal  knowledge,  but  whose  object  must  be  con- 
fessed by  all  to  be  laudable.  There  seems  to  be  something  in  the  process  of  training  young 
men  for  the  Medical  Profession,  which  encourages  in  them  a  laxity  of  thought  and  expres- 
sion on  these  matters,  that  generally  ends  in  a  laxity  of  action  and  of  principle.  It  might 
have  been  expected  that  those  who  are  so  continually  witnessing  the  melancholy  conse- 
quences of  the  violation  of  the  Divine  law  in  this  particular,  "would  be  the  last  to  break  it 
themselves :  but  this  is  unfortunately  very  far  from  being  the  case.  The  Author  regrets  to 
be  obliged  further  to  remark,  that  some  recent  works  which  have  issued  from  the  Medical 
press,  contain  much  that  is  calculated  to  excite,  rather  than  to  repress,  the  propensity ;  and 
that  the  advice  sometimes  given  by  practitioners  to  their  patients  is  immoral  as  well  as  un- 
scientific. 


476       INFLUENCE  OF  THE  NERVOUS  SYSTEM  ON  THE  ORGANIC  FUNCTIONS. 

doing  sealed  its  fate.  In  a  few  minutes  the  infant  left  off  sucking,  became  restless,  panted, 
and  sank  dead  upon  its  mother's  bosom.  The  physician  who  was  instantly  called  in,  found 
the  child  lying  in  the  cradle,  as  if  asleep,  and  with  its  features  undisturbed ;  but  all  his  re- 
sources were  fruitless.  It  was  irrecoverably  gone."*  In  this  interesting  case,  the  milk  must 
have  undergone  a  change,  which  gave  it  a  powerful  sedative  action  upon  the  susceptible 
nervous  system  of  the  infant. 

b.  The  following,  which  occurred  within  the  Author's  own  knowledge,  is  perhaps  equally 
valuable  to  the  Physiologist,  as  an  example  of  the  similarly-fatal  influence  of  undue  emotion 
of  a  different  character;  and  both  should  serve  as  a  salutary  warning  to  mothers,  not  to 
indulge  either  in  the  exciting  or  depressing  passions.     A  Lady  having  several  children,  of 
which  none  had  manifested  any  particular  tendency  to  cerebral  disease,  and  of  which  the 
youngest  was  a  healthy  infant  a  few  months  old,  heard  of  the  death  (from  acute  hydroce- 
phalus)  of  the  infant  child  of  a  friend  residing  at  a  distance,  with  whom  she  had  been  on, 
terms  of  close  intimacy,  and  whose  family  had  increased  almost  contemporaneously  with 
her  own.     The  circumstance  naturally  made  a  strong  impression  on  her  mind ;  arid  she 
dwelt  upon  it  the  more,  perhaps,  as  she  happened,  at  that  period,  to  be  separated  from  the 
rest  of  her  family,  and  to  be  much  alone  with  her  babe.     One  morning,  shortly  after  having 
nursed  it,  she  laid  the  infant  in  its  cradle,  asleep  and  apparently  in  perfect  health ;  her  atten- 
tion was  shortly  attracted  to  it  by  a  noise;  and,  on  going  to  the  cradle,  she  found  her  infant 
in  a  convulsion,  which  lasted  for  a  few  minutes,  and  then  left  it  dead. — Now,  although  the 
influence  of  the  mental  emotion  is  less  unequivocally  displayed  in  this  case  than  in  the  last, 
it  can  scarcely  be  a  matter  of  doubt ;  since  it  is  natural  that  no  feeling  should  be  stronger  in 
the  mother's  mind  under  such  circumstances,  than  the  fear  that  her  own  beloved  child 
should  be  taken  from  her,  as  that  of  her  friend  had  been ;  and  it  is  probable  that  she  had 
been  particularly  dwelling  on  it,  at  the  time  of  nursing  the  infant  on  that,  morning. 

c.  Another  instance,  in  which  the  maternal  influence  was  less  certain,  but  in  which  it  was 
not  improbably  the  immediate  cause  of  the  fatal  termination,  occurred  in  a  family  nearly 
related  to  the  Author's.     The  mother  had  lost  several  children  in  early  infancy,  from  a  con- 
vulsive disorder;  one  infant,  however,  survived  the  usually- fatal  period;  but  whilst  nursing 
him,  one  morning,  she  had  been  strongly  dwelling  on  the  fear  of  losing  him  also,  although 
he  appeared  a  very  healthy  child.     In  a  few  minutes  after  the  infant  had  been  transferred 
into  the  arms  of  the  nurse,  and  whilst  she  was  urging  her  mistress  to  take  a  more  cheerful 
view,  directing  her  attention  to  his  thriving  appearance,  he  was  seized  with  a  convulsion-fit 
and  died  almost  instantly.     Now  although  there  was  here  unquestionably  a  predisposing 
cause,  of  which  there  is  no  evidence  in  the  other  cases,  it  can  scarcely  be  doubted  that  the 
exciting  cause  of  the  fatal  disorder  is  to  be  referred  to  the  mother's  anxiety.     This  case  offers 
a  valuable  suggestion, — which,  indeed,  would  be  afforded  by  other  considerations, — that  an 
infant,  under  such  circumstances,  should  not  be  nursed  by  its  mother,  but  by  another  woman 
of  placid  temperament,  who  had  reared  healthy  children  of  her  own. 

628.  Other  Secretions  are  in  like  manner  vitiated  by  mental  Emotions,  al- 
though the  influence  is  not  always  so  manifest.  Thus,  the  halitus  from  the 
lungs  is  sometimes  almost  instantaneously  affected  by  bad  news,  so  as  to  pro- 
duce foetid  breath.  A  copious  secretion  of  foetid  gas  not  unfrequently  takes 
place  in  the  intestinal  canal,  under  the  influence  of  any  disturbing  emotion ; 
or  the  usual  fluid  secretions  from  its  walls  are  similarly  disordered.  The 
tendency  to  defecation  which  is  commonly  excited  under  such  circumstances, 
is  not,  therefore,  due  simply  to  the  relaxation  of  the  sphincter  ani  (as  com- 
monly supposed)  ;  but  is  partly  dependent  on  the  unusually  stimulating  cha- 
racter of  the  faeces  themselves.  The  same  may  be  said  of  the  tendency  to 
micturition,  which  is  experienced  under  similar  conditions :  the  change  in  its 

*  Dr.  Von  Ammon,  in  his  treatise  "  Die  ersten  Mutterpflichten  und  die  erste  Kindespflege," 
quoted  in  Dr.  Combe's  excellent  little  work  on  the  Management  of  Infancy.  Similar  facts 
are  recorded  by  other  writers.  Mr.  Wardrop  mentions  (Lancet,  No.  516),  that  having  re- 
moved a  small  tumour  from  behind  the  ear  of  a  mother,  all  went  well,  until  she  fell  into  a 
violent  passion;  and  the  child,  being  suckled  soon  afterwards,  died  in  convulsions-.  He  was 
sent  for  hastily,  to  see  another  child  in  convulsions,  after  taking  the  breast  of  a  nurse  who 
had  just  been  severely  reprimanded;  and  he  was  informed  by  Sir  Richard  Croft,  that  he  had 
seen  many  similar  instances.  Three  others  are  recorded  by  Burdach  (Physiologic,  §  522)  ; 
in  one  of  them,  the  infant  was  seized  with  convulsions  on  the  right  side,  and  hemiplegia  on 
the  left,  on  sucking  immediately  after  its  mother  had  met  with  some  distressing  occurrence. 
Another  case  was  that  of  a  puppy,  which  was  seized  with  epilepsy,  on  sucking  its  mother 
after  a  fit  of  rage. 


SOURCES  OF  DEMAND  FOR  ALIMENT.  477 

character  becomes  perceptible  enough  among  many  animals,  in  which  it  ac- 
quires a  powerfully-disagreeable  odour  under  the  influence  of  fear;  and  thus 
answers  the  purpose,  which  is  effected  in  others  by  a  peculiar  secretion.  It 
is  a  prevalent,  and  perhaps  not  an  ill-founded  opinion,  that  melancholy  and 
jealousy  have  a  tendency  to  increase  the  quantity,  and  to  vitiate  the  quality, 
of  the  biliary  fluid ;  perhaps  the  disorder  of  the  organic  function  is  more  com- 
monly the  source  of  the  former  emotion,  than  its  consequence ;  but  it  is  cer- 
tain that  the  indulgence  of  these  feelings  has  a  decidedly  morbific  effect,  by 
disordering  the  digestive  processes,  and  thus  reacts  upon  the  nervous  system 
by  impairing  its  healthy  nutrition.  On  the  influence  of  mental  emotion  in 
the  Mother,  on  the  Foetus  in  utero,  some  remarks  will  be  offered  hereafter 
(§  938). 


CHAPTER    X. 

OF  FOOD,  AND  THE  DIGESTIVE  PROCESS. 

1.— Sources  of  the  Demand  for  .Aliment. — Hunger  and  Thirst. 

629.  THE  dependence  of  all  Organized  beings  upon  a  supply  of  aliment,—- 
in  the  first  place  for  the  development  of  their  fabric,  and  in  the  second  for  the 
maintenance  of  their  activity, — is  a  circumstance  of  such  a  familiar  character, 
that  it  might  not  seem  worth  while  to  dwell  upon  it.     Nevertheless  the  in- 
quiry into  the  purposes  which  the  aliment  serves  in  the  economy,  and  into 
the  relative  values  of  different  articles  of  food,  cannot  be  advantageously  pro- 
secuted, until  we  have   first  determined,  with  more   precision,  the   causes 
which  occasion  the  demand  to  be  set  up.     These  will  be  now  briefly  enume- 
rated. 

630.  In  the  first  place,  a  due  supply  of  aliment  is  required,  for  the  first 
development  of  the  germ  into  the  adult  fabric.     In  all  instances,  the  essen- 
tial character  of  the  act  of  Reproduction  appears  to  be  the  liberation  or  setting- 
free  of  a  cell-germ  ;  which,  according  to  the  character  of  the  being  that  gave 
origin  to  it,  may  be  destined  to  evolve,  either  a  simple  cell  (as  in  the  lowest 
Cryptogamic  Plants),  a  congeries  of  cells  having  a  certain  degree  of  variety 
of  form  and  of  difference  of  function  (as  in  the  higher  classes  of  the  Vegetable 
kingdom),  or  a  complex  fabric,  composed  of  an  immense  variety  of  parts, 
most  of  them  departing  widely,  in  appearance  at  least,  from  the  original  cellu- 
lar type,  and  destined  to  perform  a  vast  variety  of  actions, — as  we  see  in  the 
perfectly  developed  organism  of  the  higher  Animals.     The  materials  which 
are  subservient  to  this  evolution,  are   all  derived  from  the  external  world ; 
either  immediately,  or  through  the  medium  of  the  parent.     The  germs  of  the 
lowly  Cryptogamia  are  thrown  at  once  upon  the  world  (so  to  speak),  to  obtain 
their  own  livelihood ;  and  they  themselves  occasion  the  combination  of  the 
inorganic  elements,  which  they  there  meet  with,  into  the  organic  compounds, 
which  are  to  be  applied  to  the  development  of  their  simple  organisms.     In 
the  Flowering  Plants,  on  the  other  hand,  the  germ  is  at  first  supplied  with  a 
store  of  nutriment,  which  has    already  undergone  this   preparation,  by  the 
agency  of  the  parent ;  and  this  store,  laid  up  in  thesseed,  is  employed  in  the 
development  of  the  fabric  of  the  young  plant,  until  its  organs  are  sufficiently 
evolved  to  enable  it  to  perform  the  same  processes  for  itself.     The  same  plan 


478  OF  FOOD,  AND  THE  DIGESTIVE  PROCESS. 

is  invariably  followed  in  the  development  of  the  Animal ;  the  nutriment  stored 
up  in  the  ovum  being  usually  sufficient  for  the  evolution  of  the  fabric,  until  it 
acquires  the  power  of  ingesting  food  for  itself ;  and  where  this  is  not  the 
case  (as  in  the  Mammalia),  a  further  provision  being  adopted,  by  which  the 
supply  is  continued  during  a  lengthened  period.  Even  when  thrown  upon 
its  own  resources,  the  young  Animal  is  often  far  from  having  attained  even 
the  form  of  its  parent;  much  less  its  size;  and  in  the  progress  of  its  evolu- 
tion, a  greater  or  less  degree  of  metamorphosis  or  change  of  form  is  observa- 
ble. This  is  not  usually  so  much'  the  case  in  the  higher  animals,  as  in  the 
lower;  because  the  supply  of  nutriment  is  proportionally  greater  in  the 
former,  and  serves  to  carry  on  the  development  to  a  later  period ;  but  the 
changes  of  condition  which  their  germinal  structure  undergoes  within  the 
ovum,  are  really  as  remarkable  as  those  which  are  presented  in  the  early  em- 
bryos of  the  latter  after  their  emersion  from  the  egg. 

a.  The  phenomena  of  metamorphosis  are  most  familiarly  known  in  the  case  of  Insects, 
and  Frogs,  which  were  formerly  thought  to  be  exceptions  to  all  general  rules ;  the  Insect 
coming  forth  from  the  egg  in  the  state  of  a  Worm;  and  the  Frog  in  the  condition  of  a  Fish. 
But  it  is  now  known  that  changes  of  form,  as  complete  as  these,  occur  in  a  large  proportion 
of  the  lower  tribes  of  Animals ;  so  that  the  absence  of  them  is  the  exception.  -  The  true 
mode  of  viewing  these  early  aspects  of  Animals  of  the  inferior  groups,  seems  to  be  to  re- 
gard them  as  foetal  or  embryonic ;  thus,  the  Insect,  in  its  larva  state,  is  essentially  a  foetus, 
as  regards  the  grade  of  development  of  its  several  tissues  and  organs ;  but  it  is  a  fostus 
capable  of  obtaining  its  own  nourishment.  In  this  condition  it  attains  its  full  growth  as  re- 
gards size,  though  its  form  remains  the  same ;  but  it  then,  in  passing  into  the  Chrysalis  state, 
re-assumes  (as  it  were)  the  condition  of  the  embryo  within  the  egg, — the  development  of 
various  new  parts  takes  place,  at  the  expense  of  the  nutriment  stored  up  in  its  tissues,— 
and  it  comes  forth  in  the  state  of  the  perfect  Insect,  which  henceforth  takes  no  more  food 
than  is  requisi4e  for  the  maintenance  of  the  fabric  thus  evolved,  or  for  the  preparation  of  the 
stores  to  be  imparted  to  the  offspring. — In  many  of  the  lower  tribes,  the  animal  quits  the 
egg  at  a  still  earlier  period  in  comparison ;  thus  it  has  been  lately  shown  by  M.  Milne  Ed- 
wards, that  some  of  the  long  Marine  Worms  consist  only  of  a  single  segment,  forming  a 
kind  of  head,  when  they  leave  the  egg ;  and  that  the  other  segments,  to  the  number  it  may 
be  of  several  hundred,  are  gradually  developed  from  this ;  the  evolution  continuing  in  some 
instances  during  a  considerable  part  of  life.  In  some  of  the  Radiated  tribes,  propagation 
actually  takes  place  whilst  the  animal  is  yet  in  its  first  or  imperfect  form  ;  thus  the  Medusae 
begin  life  as  Polypes,  and  in  this  condition  they  increase  by  germination  or  budding,  in  the 
manner  of  the  true  or  permanent  Polypes. 

631.  It  is  desirable  to  bear  in  mind,  that  the  function  of  the  Germ  is  sim- 
ply that  of  occasioning  the  combination  of  the  materials  supplied  by  the 
external  world,  and  of  directing  the  appropriation  of  those  materials.  The 
several  parts  of  the  complex  fabric  of  the  higher  Animals,  contain  a  great 
variety  of  materials ;  and  it  is  therefore  requisite  for  its  development,  that  it 
should  be  duly  supplied  with  all  these. — The  demand  set  up  by  the  fabric, 
whilst  in  course  of  development  or  evolution,  for  the  materials  of  its  growth, 
constitutes,  therefore,  the  primary  source  of  the  requirement  of  food  ;  and  the 
nature  of  this  must  be  adapted  to  the  wants  of  the  being.  Thus,  the  fabric 
of  Plants  is  essentially  composed  of  Cellulose,  a  compound  of  Oxygen,  Hy- 
drogen, and  Carbon ;  and  the  materials  required  for  the  production  of  this  are 
simply  Carbonic  Acid  and  Water.  But  nearly  all  Plants  form  some  azotized 
compound  in  the  interior  of  their  cells  ;  for  the  production  of  which,  Ammo- 
nia also  is  required.  And  in  those  species,  which,  like  the  Cerealia,  form  a 
large  quantity  of  azotized  compounds,  and  store  them  up  in  their  seeds,  a  free 
supply  of  Ammonia  is  requisite  for  the  production  of  the  greatest  proportion 
which  they  are  capable  of  generating. — In  Animals,  again,  whose  tissue  chiefly 
consists  of  these  very  azotized  compounds,  or  of  modifications  of  them,  a 
constant  supply  of  such  is  required  during  the  whole  period  of  the  develop- 
ment of  the  fabric,  as  well  as  subsequently ;  and  if  they  be  not  afforded  in 


SOURCES  OF  DEMAND  FOR  ALIMENT.  479 

sufficient  amount,  the  evolution  of  the  organism  is  either  retarded  or  checked 
altogether.*  But  there  is  one  tissue,  namely,  Fat,  the  peculiar  characters  of 
which  are  derived  from  the  presence  of  a  non-azotized  substance  in  its  cells ; 
and  this  cannot  be  developed,  unless  there  be  in  the  food  either  oily,  saccha- 
rine, or  amylaceous  matters,  from  any  of  which  the  fatty  compounds  may  be 
generated. 

632.  The  full  development  of  the  Animal  fabric,  however,  does  not  by  any 
means  involve  the  cessation  of  the  demand  for  food ;  in  fact,  during  the  whole 
period  of  that  development,  it  may  be  observed  that  the  amount  of  nutriment 
ingested  is  far  greater  than  that  which  is  applied  to  the  simple  extension  of 
the  structure  (§  269).     One  source  of  this  constant  demand  is  to  be  found  in 
the  continual  waste  or  disintegration  of  the  fabric,  which  goes  on  to  a  certain 
extent  under  all  circumstances,  but  which  varies  in  degree  according  to  cer- 
tain conditions  not  difficult  to  be  understood. — All  organized  substances  are 
liable,  from  the  peculiarity  of  their  chemical  composition,  to  interstitial  de- 
cay ;  and  this  operates  in  the  living  organism,  as  much  as  in  the  dead  body 
(§  268).     The  difference  is,  that,  in  the  living  fabric,  there  is  a  provision  for 
at  once  removing  the  products  of  decay,  so  that  they  may  be  cast  out  of  the 
system  as  soon  as  possible  ;   whilst  in  the  dead  body  they  remain,  and  act  as 
ferments,  accelerating  the  decomposition  of  other  parts.     Now  the  amount  of 
this  interstitial  decay  varies  with  the  temperature  ;  being  increased  by  warmth, 
and  retarded  by  cold.     It  is  consequently  greatest  in  warm-blooded  animals, 
the  temperature  of  whose  bodies  is  constantly  sustained  at  a  high  standard ; 
it  is  reduced  to  its  minimum  in  the  torpid  condition  of  cold-blooded  animals, 
which  is  brought  on  by  the  agency  of  cold ;  and  will  be  lowered  to  nearly 
the  same  degree  in  the  hybernating  state  of  certain   Mammalia. — There  is 
another  source  of  waste  and  decay,  which  is  common  to  Animals,  and  all  but 
the  simplest  Plants  ;  this  results  from  the  limited  duration  of  life  in  the  indi- 
vidual parts,  which  are  most  actively  concerned  in  the  Vegetative  Functions. 
We    have   seen  that  the    essential  instruments  in  the  various  functions  of 
Absorption,  Assimilation,  Respiration,  Secretion,  and  Reproduction,  are  cells; 
each  of  which  goes  through  a  certain  series  of  processes  and  then  dies  and 
decays, — just  as  do  the  isolated  cells,  which  compose  the  entire  fabric  of  the 
simplest  Cryptogamic  Plants.    This  is  evidenced  to  us  in  the  Vegetable  king- 
dom by  the  "  fall  of  the  leaf;"  which  is  nothing  else  than  the  result  of  the 
death  and  decay  of  the  component  cells  of  that  organ,  after  having  fulfilled 
their  peculiar  functions  ;  these  consisting  in  the  preparation  or  elaboration  of 
the  nutritious  sap,  from  which  the  various  tissues  and  secretions  of  the  plant 
are  subsequently  generated.     The  same  process  is   continually  taking  place, 
though  in  a  less  obvious  manner,  in  the  Animal  body  ;  the  rate  of  death  and 
renewal  of  each  group  of  cells  being  greater,  as  the  functions  to  which  it 
ministers  are  energetically  performed  ;  whilst  the  energy  of  these  operations 
is  mainly  dependent  upon  the  demand  set  up  by  the  exercise  of  the  Jlnimal 
functions,  for  the  reparation  of  the  Nervous  and  Muscular  tissues. 

633.  The  great  source  of  waste  and  decay  in  the  Animal  body,  and  con- 
sequently the  chief  source  of  the  demand  for  food,  is  the  disintegration  of  the 
Nervous  and  Muscular  tissues,  which  has  been  shown  to  be  a  necessary  con- 
dition of  their  functional  activity.     Every  manifestation  of  Nervous  power, 
of  whatever  kind,  seems  to  require  the  combination  of  Oxygen  with  the  ele- 
ments of  Nervous  matter ;  the  normal  composition  of  which  is  thus  destroyed, 

*  The  very  curious  discovery  has  lately  been  made,  in  regard  to  the  integuments  of  the 
Tunicated  or  Ascidian  Mollusca  (the  lowest  class  of  that  sub-kingdom),  that  they  contain  a 
considerable  quantity  of  Cellulose  ;  a  substance  which  had  not  been  previously  supposed  to 
be  a  normal  constituent  of  the  Animal  Fabric.  See  Annales  des  Sciences  Naturelles ;  3me 
Serie,  Zool.,  torn.  v.  p.  193  et  seq. 


480  OF  FOOD,  AND  THE  DIGESTIVE  PROCESS. 

so  that  it  ceases  to  be  fit  to  form  part  of  the  body,  and  is  cast  out  by  the  va- 
rious processes  of  excretion.  The  same  is  the  case  in  regard  to  the  Muscu- 
lar substance  ;  the  waste  of  which  is  conformable  to  the  use  made  of  it.  The 
demand  for  the  materials  of  reparation  will  follow  the  same  proportion ;  and 
as  the  preparation  of  these  materials  can  only  be  effected  by  the  agency  of 
the  Vegetative  or  nutritive  functions,  the  rate  at  which  these  are  performed 
will  be  greatly  influenced  by  the  activity  of  the  Animal  functions.  Hence 
we  see  the  necessity  of  regulating  the  supply  of  food,  in  accordance  with  the 
state  of  the  latter ;  since  a  diet  which  would  be  superfluous  and  injurious  to 
an  individual  of  inert  habits,  is  suitable  and  beneficial  to  one  who  is  leading  a 
life  of  continual  exertion.  This  difference  manifests  itself  remarkably  in  the 
contrast  between  Animals  of  different  tribes,  whose  natural  instincts  lead  them 
to  different  modes  of  life.  The  Birds  of  most  active  flight,  and  the  Mammals 
which  are  required  to  put  forth  the  greatest  efforts  to  obtain  their  food,  need 
the  largest  and  most  constant  supplies  of  nutriment ;  but  even  the  least  active 
of  these  classes  stand  in  remarkable  contrast  with  the  inert  Reptiles,  whose 
slow  and  feeble  movements  are  attended  with  so  little  waste,  that  they  can 
sustain  life  for  weeks  and  even  months,  with  little  or  no  diminution  of  their 
usual  activity,  without  a  fresh  supply  of  food.* 

634.  Finally,  there  is  a  most  important  cause  of  demand  for  food,  amongst 
the  higher  Animals,  which  does  not  exist  either  amongst  the  lower  Animals,  or 
in  the  Vegetable  kingdom,  at  least  to  any  great  degree.  In  the  classes  of 
Mammals  and  Birds,  and  in  that  of  Insects  also,  we  find  a  capability  of  sus- 
taining the  heat  of  the  body  at  a  fixed  standard  ;  which  is  usually  far  above 
that  of  the  surrounding  medium.  This  they  are  enabled  to  do,  as  will  be 
explained  hereafter,  by  a  process  strictly  analogous  to  ordinary  combustion  ; 
the  Carbon  and  Hydrogen,  which  are  directly  supplied  by  their  food,  or  which 
have  been  employed  for  a  time  in  the  composition  of  their  living  tissues  and 
then  set  free,  being  made  to  combine  with  Oxygen  introduced  by  the  respira- 
tory process,  and  thus  giving  out  the  same  heat,  as  if  the  same  materials  were 
burned  in  a  furnace.  It  will  be  hereafter  shown  that  the  immediate  cause  of 
death  in  a  warm-blooded  animal,  from  which  the  food  has  been  entirely  with- 
held, is  the  inability  any  longer  to  sustain  the  temperature  which  is  requisite  for 
the  performance  of  its  vital  operations  (Chap.  XVI.,  Sect.  2).  Hence  we  see 
the  necessity  for  a  constant  supply  of  aliment,  in  the  case  of  warm-blooded 
animals,  for  this  purpose  alone ;  and  the  demand  will  be  regulated  by  the 
external  temperature.  When  the  heat  is  rapidly  carried  off  from  the  surface 
by  the  chilling  influence  of  the  surrounding  air  or  water,  a  much  greater 
amount  of  Carbon  and  Hydrogen  must  be  consumed  within  the  body,  to  main- 
tain its  proper  heat,  than  when  the  medium  is  nearly  as  warm  as  the  body 
itself;  so  that  a  diet,  which  is  appropriate  in  the  former  circumstances,  is 
superfluous  and  injurious  in  the  latter;  and  the  food  which  is  amply  sufficient 
in  a  warm  climate,  is  utterly  destitute  of  powrer  to  enable  it  to  resist  the  influ- 
ence of  severe  cold.  Substances  rich  in  carbon  and  hydrogen,  and  having 
little  or  no  oxygen,  afford  the  most  efficient  heat-sustaining  materials ;  but  it 
is  an  essential  condition  of  their  due  action,  that  they  should  be  of  a  kind 
that  renders  them  capable  of  being  reduced  by  the  solvent  action  of  the  sto- 
mach, and  of  being  absorbed  into  the  system. 

635.  The  demand  for  food  is  -increased  by  any  cause  which  creates  an 
unusual  drain  or  waste  in  the  system.  Thus  an  extensive  suppurating  action 

*  The  materials  which  are  required  for  the  reparation  of  the  Muscular  tissue,  are  chiefly 
of  a  fibrinous  nature ;  those  employed  for  the  renovation  of  the  Nervous  substance,  would 
seem  to  be  fatty  matter  with  Phosphorus.  But  from  the  peculiar  composition  of  the  fatty 
matters  of  the  Nervous  substance  (especially  the  presence  of  Azote  in  them),  it  seems  quite 
uncertain  from  which  of  the  constituents  of  the  food  they  are  really  formed, 


DEMAND  FOR  ALIMENT. — SENSE  OF  HUNGER.  481 

can  be  sustained  only  by  a  large  supply  of  highly  nutritious  food.  The 
mother  who  has  to  furnish  the  daily  supply  of  milk,  which  constitutes  the 
sole  support  of  her  offspring,  needs  an  unusual  sustenance  for  this  purpose. 
And  there  are  states  of  the  system,  in  which  the  solid,  tissues  seem  to  possess 
an  unusual  tendency  to  decomposition,  and  in  which  an  increased  supply  of 
aliment  is  therefore  required.  This  is  the  case,  for  example,  in  Diabetes  ;  one 
of  the  first  symptoms  of  which  disease  is  the  craving  appetite,  that  seems  as 
if  it  would  be  never  satisfied.  And  there  can  be  no  doubt  that,  putting  aside 
all  the  other  circumstances  which  have  been  alluded  to,  there  is  much  differ- 
ence amongst  individuals,  in  regard  to  the  rapidity  of  the  changes  which  their 
organism  undergoes,  and  the  amount  of  food  consequently  required  for  its 
maintenance. 

636.  The  want  of  solid  aliment  is  indicated  by  the  sensation  of  Hunger  ; 
and  that  of  liquid  by  thirst.     The  former  of  these  sensations  is  referred  to 
the  stomach  ;  and  the  latter  to  the  fauces  :  but  although  certain  conditions  of 
these  parts  may  be  the  immediate  cause  of  the  sensations  in  question,  they 
are  really  indicative  of  the  requirements  of  the  system  at  large.     For  the  in- 
tensity of  the  feelings  bears  no   constant  relation  to  the  amount  of  solid  or 
liquid  aliment  in  the  stomach  ;  whilst,  on  the  other  hand,  it  does  correspond 
with  the  excess  of  demand  in  the  system,  over  the   supply  afforded  by  the 
blood;  and  it  is  caused  to  abate  by  the  introduction  of  the  requisite  materials 
into  the  circulating  fluid,  even  though  this  be  not  accomplished  in  the  usual 
manner  by  the  ingestion  of  food  into  the  stomach. 

637.  That  the  sense  of  Hunger,  however,  is  immediately  dependent  upon 
some  condition  of  the  Stomach,  seems  to  follow  from  the  fact,  that  it  is  abated, 
if  not  arrested,  by  section  of  the  Par  Vagum  (§  412)  ;  and  that  it  may  be 
temporarily  alleviated,  by  introducing  into  the  digestive  cavity,  matter  which 
is  not  alimentary.     Of  the  precise  nature  of  that  condition,  however,  we  have 
no  certain  knowledge.     It  is  easy  to  prove  that  many  of  the  causes  which 
have  been  assigned  for  the  sensation,  are  but  little,  if  at  all,  concerned  in  pro- 
ducing it.     Thus,  mere  emptiness  of  the  stomach  cannot  occasion  it ;  since, 
if  the  previous  meal  have  been  ample,  the  food  passes  from  its  cavity  some 
time  before  a  renewal  of  the  uneasy  feeling ;  and  this  emptiness  may  continue 
(in  certain  disordered  states  of  the  system)  for  many  hours  or  even  days,  with- 
out a  return  of  desire  for  food.     It  cannot  be  due,  as  some  have  supposed,  to 
the  action  of  the  gastric  fluid  upon  the  coats  of  the  stomach  themselves  ;  since 
this  fluid  is  not  poured  into  the  Stomach,  except  when  the  production  of  it  is 
stimulated  by  the  irritation  of  its  secreting  follicles.     By  Dr.  Beaumont  it  is 
thought,  that  the  distension  of  these  follicles  with  the  secreted  fluid  is  the 
proximate  cause  of  hunger;  but  there  is  no  more  reason  to  believe  that  the 
secretion  of  Gastric  fluid  is  accumulating  during  the  intervals  when  it  is  not 
required,  than  there  is  in  regard  to  Saliva,  the  Lachrymal  fluid,  or  any  other 
secretions,  which  are  occasionally  poured  out  in  large  quantities  under  the  in- 
fluence of  a  particular  stimulus;  and,  moreover,  it  is  difficult  to  imagine  how 
mental  emotion,  or  any  impression  on  the  nervous  system  alone  (which  is 
able,  as  is  well  known,  to  dissipate  the  keenest  appetite  in  a  moment),  can  re- 
lieve such  distension. — It  may,  perhaps,  be  a  more  probable  supposition,  that 
there  is  a  certain  condition  of  the  Capillary  circulation  in  the  Stomach,  which 
is  preparatory  to  the  secretion,  and  which  is  excited  by  the  influence  of  the 
Sympathetic  nerves,  that  communicate  (as  it  were)  the  wants  of  the  general 
system.     This  condition  may  be  easily  imagined  to  be  the  proximate  cause 
of  the  sensation  of  hunger,  by  acting  on  the  Par  Vagum.     When  food  is  in- 
troduced into  the  stomach,  the  act  of  secretion  is  directly  excited  ;  the  capil- 
lary vessels  are  gradually  unloaded  ;  and  the  immediate  cause  of  the  impres- 
sion on  the  par  vagum  is  withdrawn.     By  the  conversion  of  the  alimentary 

41 


482  OF  FOOD,  AND  THE  DIGESTIVE  PROCESS. 

matter  into  materials  fit  for  the  nutrition  of  the  system,  the  remote  de- 
mand also  is  satisfied;  and  thus  it  is  that  the  condition  of  the  stomach  just 
referred  to,  is  permanently  relieved  by  the  ingestion  of  substances  that  can 
serve  as  food.  But  if  the  ingested  matter  be  not  of  a  kind  capable  of  solution 
and  assimilation,  the  feeling  of  hunger  is  only  temporarily  relieved,  and  soon 
returns  in  greater  force  than  before. — The  theory  here  given  seems  reconcile- 
able  with  all  that  has  been  said  of  the  conditions  of  the  sense  of  hunger  ;  and 
particularly  with  what  is  known  of  the  effect  produced  upon  it  by  nervous 
impressions,  which  have  a  peculiar  influence  upon  the  capillary  circulation. 
It  also  corresponds  exactly  with  what  we  know  of  the  influence  of  the  nerv- 
ous system,  and  of  mental  impressions,  upon  other  secretions  (§  624). 

638.  The  sense  of  Hunger,  like  other  sensations,  may  not  be  taken  cogni- 
zance of  by  the  Mind,  if  its  attention  be  strongly  directed  towards  other  ob- 
jects; of  this  fact,  almost  every  one  engaged  in  active  occupations,  whether 
mental  or  bodily,  is  occasionally  conscious.  The  nocturnal  student,  who  takes 
a  light  and  early  evening  meal,  and,  after  devoting  himself  to  his  pursuits  for 
several  hours  uninterruptedly,  retires  to  rest  with  a  wearied  head  and  an  empty 
stomach,  but  without  the  least  sensation  of  hunger,  is  frequently  prevented 
from  sleeping  by  an  indescribable  feeling  of  restlessness  and  deficiency ;  and 
the  introduction  of  a  small  quantity  of  food  into  the  stomach  will  almost  in- 
stantaneously allay  this,  and  procure  comfortable  rest.     Many  persons,  again, 
who  desire  to  take  active  exercise  before  breakfast,  are  prevented  from  doing 
so  by  the  lassitude  and  even  faintness  which  it  induces, — the  bodily  exercise 
increasing  the  demand  for  food,  whilst  it  draws  off  the  attention  from  the  sen- 
sation of  hunger. 

a.  The  Author  may  be  excused  for  mentioning  the  following  circumstance,  which  some 
years  ago  occurred  to  himself;  and  which  seems  to  him  a  good  illustration  of  the  principle, 
that  the  sense  of  hunger  originates  in  the  condition  of  the  general  system,  and  that  its  mani- 
festation through  a  peculiar  action  in  the  stomach,  is  to  be  regarded  as  a  secondary  pheno- 
menon,— adapted,  under  ordinary  circumstances,  to  arouse  the  mind  to  the  actions  necessary 
for  the  supply  of  the  physical  wants, — but  capable  of  being  overlooked  if  the  attention  of 
the  mind  be  otherwise  directed.  He  was  walking  alone  through  a  beautiful  country,  and 
with  much  to  occupy  his  mind ;  and,  having  expected  to  meet  with  some  opportunity  of  ob- 
taining refreshment  on  his  road,  he  had  taken  no  food  since  his  breakfast.  This  expectation, 
however,  was  not  fulfilled  ;  but,  as  he  felt  no  hunger,  he  thought  little  of  the  disappointment. 
It  was  evening  before  he  approached  the  place  of  his  destination,  after  having  walked  about 
twenty  miles,  resting  frequently  by  the  way  ;  and  he  then  began  to  feel  a  peculiar  lassitude, 
differing  from  ordinary  fatigue,  which  rapidly  increased,  so  that  during  the  last  mile  he  could 
scarcely  support  himself.  The  "  stimulus  of  necessity,"  however,  kept  him  up ;  but  on  ar- 
riving at  his  temporary  home,  he  immediately  fainted.  It  is  obvious  that,  in  this  case,  the 
occupation  of  the  mind  on  the  objects  around,  and  on  its  own  thoughts,  had  prevented  the 
usual  warning-  of  hunger  from  being  perceived ;  and  the  effect  which  succeeded  was  ex- 
actly what  was  to  be  anticipated,  from  the  exhaustion  of  the  supply  of  food  occasioned  by 
the  active  and  prolonged  exertion. 

639.  The  conditions  of  the  sense  of  Thirst  appear  to  be  very  analogous  to 
those  of  hunger.     This  sense  is  not  referred,  however,  to  the  stomach,  but  to 
the  fauces.     It  is  generally  considered  that  it  immediately  results  from  an  im- 
pression on  the  nerves  of  the  stomach  ;  since,  if  liquids  are  introduced  into 
the  stomach  through  an  oesophagus-tube,  they  are  just  as  effectual  in  allaying 
thirst,  as  if  they  are   swallowed  in  the  ordinary  manner.     It  may,  however, 
be  doubted,  whether  the  sense  of  thirst  is  not  even  more  immediately  connect- 
ed with  the  state  of  the  general  system,  than  that  of  hunger ;  for  the  imme- 
diate relief  afforded  by  the  introduction  of  liquid  into  the  stomach,  is  fully  ac- 
counted for  by  the  instantaneous  absorption  of  the  fluid  into  the  veins,  which 
is  known  to  take  place  when  there  is  a  demand  for  it,  not  only  from  Dr.  Beau- 
mont's observations,  but  from  many  experiments  made  with  reference  to  this 
particular  question.     This  demand  is  increased  with  almost  equal  rapidity, 


NATURE  AND  DESTINATION  OF  FOOD.  483 

by  an  excess  in  the  amount  of  the  fluid  excretions  ;  and  it  may  be  satisfied 
without  the  introduction  of  water  into  the  stomach*  (§  677).  Thirst  may  also 
be  produced,  however,  by  the  impression  made  by  peculiar  kinds  of  food  or 
drink  upon  the  walls  of  the  alimentary  canal ;  thus  salted  or  highly-spiced 
meat,  fermented  liquors  when  too  little  diluted,  and  other  similarly  irritating 
agents,  excite  thirst ;  the  purpose  of  which  is  obviously  to  cause  ingestion  of 
fluid,  by  which  they  may  be  diluted. 

2. — Nature  and  Destination  of  the  Food  of  Animals. 

640.  The  substances  which  are  required  by  Animals  for  the  development 
and  maintenance  of  their  fabric,  are  of  two  kinds ; — the  Organic  and  the  In- 
organic.    The  former  alone  are  commonly  reckoned  as  aliments ;  but  the  lat- 
ter are  really  not  less  requisite  for  the  sustenance  of  the  body,  which  speedily 
disintegrates,  if  the  attempt  be  made  to  support  it  upon  any  organic  com- 
pounds in  a  state  of  purity.     In  all  ordinary  articles  of  diet,  however,  the  in- 
organic matters  are  present  in  the  requisite  proportion ;  and  hence  they  have 
very  commonly  escaped  notice.     The  nature  of  these  substances,  and  the 
mode  in  which  they  are  introduced  into  the  body,  will  be  considered  here- 
after (§  648).     The  Organic  matters,  used  as  food  by  Animals,  are  partly 
derived  from  the  Animal,  and  partly  from  the  Vegetable  kingdom ;  and  they 
may  be  conveniently  arranged   under  the  four  following   heads:! — 1.  The 
Saccharine  group,  including  all  those  substances,  derived  from  the  Vegetable 
kingdom,  which  are  analogous  in  their  composition  to  Sugar ; — consisting  of 
oxygen,  hydrogen,'  arid  carbon,  alone  \  and  having  the  two  first  present  in  the 
proportions  to  form  water.     To  this  group  belong  starch,  gum,  woody  fibre, 
and  the  various  tissues  of  Plants ;  which  closely  resemble  each  other  in  the 
proportion  of  their  elements,  and  which  may  be  converted  into  Sugar  by  che- 
mical processes  of  a  simple  kind. — 2.  The  Oleaginous  group,  including  oily 
matters,  whether  derived  from  the  Vegetable  kingdom,  or  from  the  fatty  por- 
tions of  Animal  bodies.     The  characteristic  of  this  class,  is  the  great  pre- 
dominance of  hydrogen  and  carbon,  the  small  proportion  of  oxygen,  and  the 
entire  absence  of  nitrogen. — 3.  The  Albuminous  group,  comprising  all  those 
substances,  whether  derived  from  the  Animal  or  Vegetable  kingdom,  which 
are  closely  allied  to  Albumen,  and  therefore  to  the  majority  of  the  Animal 
tissues,  in  their  chemical  composition.     In  this  group,  a  large  proportion  of 
azote  is  united  with  the  oxygen,  hydrogen,  and  carbon  of  the  preceding. — 
4.  The  Gelatinous  group,  consisting  of  substances  derived  from  Animal  bodies 
only,  which  are  closely  allied  to  Gelatine  in  their  composition.     These  also 
contain  azote ;  but  the  proportion  of  their  components  differs  from  that  of  the 
preceding. 

641.  The  compounds  of  the  Saccharine  group  cannot,  without  undergoing 
a  metamorphosis,  form  part  of  any  Animal  tissue ;  as  there  is  none  which 
they  resemble  in  composition.     It  will  be  shown,  however,  that  they  are  con- 
vertible, within  the  Animal  body,  into  those  of  the  Oleaginous  group ;  and, 
like  them,  may  be  deposited  in  the  form  of  Adipose  matter.     There  is  no 
other  tissue  in  the  body,  into  which  they  can  enter  without  considerable  change ; 
for  all  others  are  azotized;  and  it  seems  extremely  improbable  that  non-azo- 
tized  compounds  can,  under  any  circumstances,  be  converted  within  the  body 
into  compounds  of  the  albuminous  or  gelatinous  groups. 

*  This  was  among  the  remarkable  results  of  the  injection  of  fluid  into  the  veins,  in  the 
Asiatic  Cholera. 

t  Dr.  Prout's  classification  of  alimentary  substances  is  here  adopted,  with  a  slight  modifi- 
cation; not  as  being  altogether  unexceptionable,  but  as  being,  in  the  Author's  opinion,  the 
most  convenient  hitherto  proposed. 


484  OF  FOOD,  AND  THE  DIGESTIVE  PROCESS. 

642.  The  application  of  the  substances  forming  the  Albuminous  group*  to 
the  support  of  the  Animal  body,  by  affording  the  materials  for  the  nutrition 
and  re-formation  of  its  tissues,  needs  little  explanation.     The  proportions  of 
the  four  ingredients  of  which  they  are  all  composed,  are  so  nearly  the  same, 
that  no  essential  difference  appears  to  exist  among  them ;  and  it  is  a  matter  of 
little  consequence,  except  as  far  as  the  gratification  of  the  palate  is  concerned, 
whether  we  feed  upon  the  flesh  of  animals  (fibrine),  upon  the  white  of  egg 
(albumen),  the  curd  of  milk  (caseine),  the  grain  of  wheat  (gluten),  or  the  seed 
of  the  pea  (legumin).     All  these  substances  are  reduced  in  the  stomach  to  the 
form  of  albumen;  which  resembles  the  gum  of  Plants,  in  being  the  raw  ma- 
terial, as  it  were,  out  of  which  the  various  fabrics  of  the  body  are  constructed. 
But  the  rule  holds  good,  with  regard  to  these  also,  that  by  being  made  to 
feed  constantly  on  the  same  substance,— boiled  white  of  egg,  for  instance,  or 
meat  deprived  of  the  principle  (osmazome)  that  gives  it  flavour, — an  animal 
may  be  effectually  starved ;  its  disgust  at  the  food  being  such,  that  even  if  it 
be  swallowed,  it  is  not  digested.     It  is  very  interesting  to  remark  that,  in  the 
only  instance  in  which  Nature  has  provided  a  single  article  of  food  for  the 
support  of  the  animal  body,  she  has  mingled  articles  from  the  three  first  of 
the  preceding  groups.     This  is  the  case  in  Milk,  which  contains  a  conside- 
rable quantity  of  an  albuminous  substance,  caseine,  which  forms  its  curd ;  a 
good  deal  of  oily  matter,  the  butter ;  and  no  inconsiderable  amount  of  sugar, 
which  is  dissolved  in  the  whey.     The  proportions  of  these  vary  in  different 
Mammalia ;  and  they  depend  in  part  upon  the  nature  of  the  food  supplied 
to  the  Animal  that  forms  the  milk  ;  but  the  substances  are  thus  combined  in 
every  instance. — Although  the  greater  part  of  the  organized  tissue  of  Animals 
is  formed  at  the  expense  of  the  Albumen  and  Fibrine  of  their  blood,  yet 
many  of  them  also  contain  a  large  quantity  of  Gelatine.     It  seems  certain 
that  this  gelatine  may  be  produced  out  of  fibrine  and  albumen ;  since  in  ani- 
mals that  are  supported  on  these  alone,  the  nutrition  of  the  gelatinous  tissues 
does  not  seem  to  be  impaired.     But  it  also  appears,  that  gelatine  taken  in  as 
food  may  be  applied  to  this  purpose;  for  ordinary  experience  shows,  that  be- 
nefit is  derived  from  jelly,  soup,  broth,  &c. ;  peculiarly  by  persons  who  have 
been  suffering  under  exhausting  diseases,  such  as  fevers.     But  it  also  ap- 
pears certain,  that  it  cannot  be  applied  to  the  nutrition  of  the  Albuminous 
tissues.     Some  important  experiments  have  been  recently  made  in  Paris  on 
this  subject,  with  a  view  of  determining  how  far  the  soup  made  from  crushed 
bones,  which  constituted  a  principal  article  of  diet  in  the  hospitals  of  Paris, 
was  adequate  for  the  support  of  the  patients.     The  result  of  these  has  been 
quite  confirmatory  of  previous  conclusions, — namely,  that   Gelatine  may  be 
advantageously  mixed  with  albumen,  fibrine,  gluten,  &c.,  and  those  other  in- 
gredients which  exist  in  meat-soup  and  bread ;  but  that,  when  taken  alone,  it 
has  little  more  power  of  sustaining  life   than  sugar  or  starch  possesses ;   and 
that,  even  when  bread  is  united  with  gelatine-soup,  it  does  not  give  it  the  re- 
quisite power  of  nutrition. 

643.  If  the  non-azotized  compounds  which  exist  so  largely  in  the  food  of 
Herbivorous  animals,  be  not  destined  to  form  part  (in  any  considerable  degree 
at  least)  of  their  tissues,  the  question  arises, — what  becomes  of  them?     It  is 
not  enough  to  say  that  they  are  deposited  as  Fat;  since  it  is  only  when  a  large 
quantity  of  them  is  taken  in,  that  there  is  any  increase  in  the  quantity  of  fat 
already  in  the  body.     We  shall  hereafter  see,  that  they  are  used  up  in  the 
process  of  Respiration ;  being  burned-off  within  the  body,  for  the  purpose  of 
keeping  up  its  temperature.     The  process  will  be  hereafter  considered  more 
in  detail ;  and  at  present  we  need  only  stop  to  remark  upon  the  adaptation 
between  the  food  provided  for  animals  in  different  climates,  and  the  amount 
of  heat  which  it  is  necessary  for  them  to  produce.    Thus  the  bears,  and  seals, 


NATURE  AND  DESTINATION  OF  FOOD.  485 

and  whales,  from  which  the  Esquimaux  and  the  Greenlander  derive  their  sup- 
port, have  an  enormous  quantity  of  fat  in  their  massive  bodies :  this  fat  is  as 
much  esteemed  as  an  article  of  food  among  these  people,  as  it  would  be  thought 
repulsive  by  the  inhabitants  of  southern  climates ;  and  by  the  large  quantity  of 
it  they  consume,  they  are. able  to  support  the  bitterness  of  an  Arctic  winter, 
without  appearing  to  suffer  more  from  the  extreme  cold,  than  do  the  residents 
in  more  temperate  climates  during  their  winter.  On  the  other  hand,  the  ante- 
lopes, deer,  and  wild  cattle,  which  form  a  large  proportion  of  the  animal  food 
of  savage  or  half-cultivated  nations  inhabiting  temperate  or  tropical  regions,  pos- 
sess very  little  fat;  and  the  comparatively  small  supply  of  carbon  and  hydro- 
gen, whose  combustion  is  required  to  keep  up  the  bodily  temperature  of  the 
inhabitants  of  those  regions,  is  derived  from  the  flesh  of  those  animals,  in  the 
manner  that  will  be  presently  explained.  Every  one  knows  how  much  less 
vigorous  the  appetite  becomes,  during  the  heat  of  summer,  than  it  is  during 
the  colder  portion  of  the  year;  and  this  is  a  natural  result  of  the  diminished 
demand  for  the  fuel  required  to  maintain  the  temperature.  And  one  great 
means  of  preserving  the  health,  during  a  prolonged  residence  in  a  hot  climate, 
is  to  attend  to  the  dictates  of  Nature,  in  regard  to  the  quantity  of  food  ingested ; 
instead  of  endeavouring  (as  is  the  prevalent  practice)  to  stimulate  the  appetite 
by  artificial  provocatives. 

644.  The  maintenance  of  the  bodily  temperature  in  Carnivorous  animals, 
appears  to  depend  upon  the  combustion  of  the  carbon  and  hydrogen  set  free 
by  the  Disintegration  of  their  Nervous  and  Muscular  tissues:  this  disintegra- 
tion taking  place  with  much  more  rapidity,  in  consequence  of  their  almost 
unceasing  activity,  than  it  does  in  the  Herbivorous  animals,  which  lead  com- 
paratively inactive  lives.  Every  one  who  has  visited  a  menagerie,  must  have 
noticed  the  continual  restlessness  of  the  Tigers,  Leopards,  Hyenas,  &c.,  which 
keep  pacing  from  one  end  of  their  narrow  cages  to  the  other ;  and  it  would 
seem  as  if  this  restlessness  were  a  natural  instinct,  impelling  them  to  use  mus- 
cular exertion  sufficient  for  the  metamorphosis  of  an  adequate  amount  of  tissue, 
that  enough  carbon  and  hydrogen  may  be  set  free  for  the  support  of  the  respi- 
ratory process.  And  we  see  a  corresponding  activity  in  the  Human  hunters 
of  the  swift-footed  Antelope  and  agile  Deer,  which  answers  a  similar  purpose; 
and  which  is  remarkably  contrasted  with  the  stupid  inertness  of  the  inhabitants 
of  the  frigid  zone,  which  is  only  occasionally  interrupted  by  the  necessity  of 
securing  the  supplies  of  food  afforded  by  the  massive  tenants  of  their  seas. — 
The  nutrition  of  the  Carnivorous  races  may,  then,  be  thus  described.  The 
bodies  of  the  animals  upon  which  they  feed  contain  flesh,  fat,  &c.,  in  nearly 
the  same  proportion  as  their  own ;  and  all,  or  nearly  all,  the  aliment  they  con- 
sume, goes  to  supply  the  waste  in  the  fabric  of  their  own  bodies,  being  con- 
verted into  its  various  forms  of  tissue.  After  having  remained  in  this  condition 
for  a  certain  time,  varying  according  to  the  use  that  is  made  of  them,  these 
tissues  undergo  another  metamorphosis,  which  ends  in  restoring  them  to  inor- 
ganic matter ;  and  thus  give  back  to  the  Mineral  world  the  materials  which 
were  drawn  off  from  it  by  Plants.  Of  these  Materials,  part  are  burned  off,  as 
it  were,  within  the  body,  by  union  with  the  oxygen  of  the  air,  taken  in  through 
the  lungs  ;  and  are  discharged  from  these  organs,  in  the  form  of  carbonic  acid 
and  water:  the  remainder  are  carried  off  in  the  liquid  form  by  other  channels. 
Hence  we  may  briefly  express  the  destination  of  their  food  in  the  following 
manner : — 

Food  consisting  oH  (    T .   .         .       .     ,    ,.       f  Carbonic    acid   and    Water 

albumen,    fibrine,  I  Convert- S  lg  .  /     An'  thrown  off  by  respiration, 

and  other  azotized  f   ed  into  )  Or8anized  >    metamor-  ±  Urea  &nd  bmary  matter>  &c §> 
compounds  }  \  thrown  off  by  other  excretions. 

41* 


486  OF  FOOD,  AND  THE  DIGESTIVE  PROCESS. 

645.  But  in  regard  to  the  Herbivorous  animals,  the  case  is  different.    They 
perspire  much  more  abundantly,  and  their  temperature  is  thus  continually  kept 
down.     They  consequently  require  a  more  active  combustion,  to  develope 
sufficient  bodily  heat;  and  the  materials  for  this  are  supplied,  as  we  have 
seen,  by  the  non-azotized  portions  of  their  food,  rather  than  by  the  metamor- 
phosis of  their  own  tissues,  which  takes  place  with  much  less  rapidity  than  in 
the  Carnivorous  tribes.     Hence  we  may  thus  express  the  destination  of  this 
part  of  their  food ;  that  of  the  azotized  matter,  here  much  smaller  in  amount, 
will  be  the  same  as  in  the  preceding  case : — 

Starch,   toil,     and  }       partly       C    .  , .  }   but  chiefly   C   Carbonic  acid  and  Water,  dis- 

other  non-azotized  >   converted    ?      .  lpc   J   >   thrown  off  <    engaged  by  the   respiratory 
compounds  ;        into         (  )    directly  as   (   process. 

The  proportion  of  the  food  deposited  as  fat,  will  depend  in  part  upon  the  sur- 
plus which  remains,  after  the  necessary  supply  of  materials  has  been  afforded 
to  the  respiratory  process.  Hence,  the  same  quantity  of  food  being  taken,  the 
quantity  of  fat  will  be  increased  by  causes  that  check  the  perspiration,  and 
otherwise  prevent  the  temperature  of  the  body  from  being  lowered,  so  that 
there  is  need  of  less  combustion  within  the  body  to  keep  up  its  heat.  This  is 
consistent  with  the  teachings  of  experience  respecting  the  fattening  of  cattle ; 
for  it  is  well  known  that  this  may  be  accomplished  much  sooner,  if  the  animals 
are  shut  up  in  a  warm  dwelling  and  covered  with  cloths,  than  if  they  are  freely 
exposed  in  the  open  air. 

646.  Now  the  condition  of  Man  may  be  regarded  as  intermediate  between 
these  two  extremes.     The  construction  of  his  digestive  apparatus,  as  well  as 
his  own  instinctive  propensities,  point  to  a  mixed  diet  as  that  which  is  best 
suited  to  his  wants.     It  does  not  appear  that  a  diet  composed  of  ordinary 
vegetables  only,  is  favourable  to  the  full  development  of  either  his  bodily  or 
mental  powers;  but  this  cannot  be  said  in  regard  to  a  diet  of  which  bread  is 
the  chief  ingredient,  since  the  gluten  it  contains  appears  to  be  as  well  adapted 
for  the  nutrition  of  the  animal  tissues,  as  does  the  flesh  of  animals.     On  the 
other  hand,  a  diet  composed  of  animal  flesh  alone  is  the  least  economical  that 
can  be  conceived ;  for,  since  the  greatest  demand  for  food  is  created  in  him 
(taking  a  man  of  average  habits,  in  regard  to  activity  and  the  climate  he  in- 
habits), by  the  necessity  for  a  supply  of  carbon  and  hydrogen  to  support  his 
respiration,  this  want  may  be  most  advantageously  fulfilled  by  the  employment 
of  a  certain  quantity  of  non-azotized  food,  in  which  these  ingredients  predomi- 
nate.    Thus  it  has  been  calculated,  that,  since  fifteen  pounds  of  flesh  contain 
no  more  carbon  than  four  pounds  of  starch,  a  savage  with  one  carcass  and  an 
equal  weight  of  starch,  could  support  life  for  the  same  length  of  time,  during 
which  another  restricted  to  animal  food  would  require  five  such  carcasses,  in 
order  to  procure  the  carbon  necessary  for  respiration.     Hence  we  see  the  im- 
mense advantage  as  to  economy  of  food,  which  a  fixed  agricultural  population 
possesses  over  those  wandering  tribes  of  hunters,  which  still  people  a  large 
part  both  of  the  old  and  new  continents.     The  mixture  of  the  azotized  and 
non-azotized  compounds  (gluten  and  starch),  that  exists  in  wheat  flour,  seems 
to  be  just  that  which  is  most  useful  to  Man ;  and  hence  we  see  the  explanation 
of  the  fact,  that,  from  very  early  ages,  bread  has  been  regarded  as  the  "  staff 
of  life."    In  regard  to  the  nutritious  properties  of  different  articles  of  vegetable 
food,  these  may  be  generally  estimated  by  the  proportion  of  azote  they  con- 
tain ;  which  is  in  almost  every  instance  less  than  that  existing  in  good  wheat 
flour. 

647.  The  following  table  represents  the   relative  quantity  of  Nitrogen  in 
different  articles  used  as  food ;  and  thus  shows  their  relative  applicability  to 


NUTRITIVE  POWER  OF  DIFFERENT  KINDS  OF  FOOD. 


487 


the  maintenance  and  reparation  of  the  body.*  Those  which  are  poorest  in 
nitrogen,  are  richest  in  Carbon  and  Hydrogen ;  and  are,  therefore,  the  best 
adapted  to  serve  as  the  pabulum  for  the  heat-sustaining  process.  It  is  to  be 
borne  in  i^nd,  however,  that  no  table  of  this  kind,  founded  simply  upon  the 
Chemical  composition  of  the  various  substances,  can  indicate  their  respective 
fitness  as  articles  of  diet ;  since  this  depends  also  upon  the  facility  with  which 
they  are  reduced  by  the  digestive  process,  and  afterwards  assimilated.  Thus 
an  aliment,  abounding  in  nutritive  matter,  may  be  inferior  to  one  which  really 
contains  a  much  smaller  proportion,  if  only  a  part  in  the  first  case,  and  the 
whole  in  the  second,  be  readily  taken  up  by  the  system.— In  the  following 
table,  Human  Milk  is  taken  as  the  standard ;  and  the  quantity  of  Nitrogen  it 
contains  is  expressed  by  100.  But  it  must  be  borne  in  mind  that  this  sub- 
stance is  intended  for  the  nourishment  of  a  being  that  passes  nearly  the  whole 
of  its  time  in  a  quiescent  state ;  and  must  not  be  supposed  to  be  adapted  for 
the  sole  maintenance  of  the  Human  body  in  a  state  of  activity.  In  fact,  it  is 
inferior  in  its  proportion  of  Caseine  (the  substance  of  which  alone  the  azote 
forms  a  part)  to  the  milk  of  most,  if  not  all,  other  Mammalia  ;  their  young 
bringing  their  animal  functions  into  exercise  at  a  much  earlier  period  than  the 
Human  infant. 


Rice 
Potatoes 
Turnips 
Rye    . 
Maize     . 
Barley 


Human  milk 

Cow's  milk     . 

Oyster 

Yolk  of  eggs   . 

Cheese 

Eel,  raw 

boiled 

Liver  of  crab 
Mussel,  raw 

boiled 

Ox  liver,  Yaw 
Pork-ham,  raw 
boiled 


Vegetable. 

.  .  81  Oats  .  .  .  138 

.  ^84  White  bread  .  .  .  142 

.  .  106  Wheat  .  .  119-144 
.  106  Carrots  .  .  .  150 

100-125         Brown  Bread  .  166 


.  125         Agaricus  cantharellus     201         Beans 


.  239 

Agaricus  russula  .  264 
Lentils  .  .  .276 
Haricot  beans  .  .  283 
Agaricus  deliciosus  289 


Animal. 


.  100 

Salmon,  raw 

.     .  237 

•  boiled 

.  305 

Liver  of  Pigeon 

.     .  305 

Portable  soup 

331-447 

White  of  Egg 

.     .  434 

Crab,  boiled     . 

.  428 

Skate,  raw 

.     .  471 

boiled     . 

.  528 

Herring,  raw 

.     .  660 

boiled 

.  570 

milt  of 

.     .  539 

Haddock,  raw 

.  807 

boiled 

776 
610 
742 
764 
845 
859 
859 
956 
910 
808 
924 
920 
816 


Flounder,  raw 

•  boiled 

Pigeon,  raw 

boiled 

Lamb,  raw 
Mutton,  raw     . 

boiled 

Veal,  raw 

boiled 

Beef,  raw 

boiled 

Ox  lung 


.     .  320 


898 
954 
756 
827 
833 
773 
852 
873 
911 
880 
942 
931 


648.  Besides  these  substances,  there  are  certain  Mineral  ingredients,  which 
may  be  said  to  constitute  part  of  the  food  of  Animals  ;  being  necessary  to  their 
support,  in  the  same  manner  as  other  mineral  substances  are  necessary  to  the 
support  of  Plants.  Of  this  kind  are  common  salt,  and  also  phosphorus,  sul- 
phur, and  lime,  either  in  combination  or  separate.  The  uses  of  Salt  are  very 
numerous  and  important.  It  consists  of  two  substances  of  opposite  qualities, 
muriatic  acid  and  soda ;  and  the  former  is  the  essential  ingredient  in  the  gastric 
juice ;  whilst  the  latter  performs  a  very  important  part  in  the  production  of 
bile.  Phosphorus  is  chiefly  required  to  be  united  with  fatty  matter,  to  serve 
as  the  material  of  the  nervous  tissue;  and  to  be  combined  with  oxygen  and 
lime,  to  form  the  bone-earth,  by  which  the  bone  is  consolidated.  Sulphur 
exists  in  small  quantities  in  several  animal  tissues  ;  but  its  part  is  by  no 
means  so  important,  as  that  performed  by  phosphorus.  Lime  is  required  for 
the  consolidation  of  the  bones ;  and  for  the  production  of  the  shells  and  other 


*  Schlossberger  and  Kemp,  in  Philosophical  Magazine.     Nov.  1845. 


488  OF  FOOD,  AND  THE  DIGESTIVE  PROCESS. 

hard  parts,  that  form  the  skeletons  of  the  Invertebrata.  To  these  ingredients 
we  may  also  add  Iron,  which  is  a  very  important  element  in  the  red  blood  of 
Vertebrated  animals. — These  substances  are  contained,  more  or  less  abund- 
antly, in  most  articles  generally  used  as  food;  and  where  they  aft  deficient, 
the  animal  suffers  in  consequence,  if  they  are  not  supplied  in  any  other  way. 
Thus  common  Salt  exists,  in  no  inconsiderable  quantity,  in  the  flesh  and 
fluids  of  animals,  in  milk,  and  in  the  egg :  it  is  not  so  abundant,  however,  in 
plants  ;  and  the  deficiency  is  usually  supplied  to  herbivorous  animals  by  some 
other  means.  Thus  salt  is  purposely  mingled  with  the  food  of  domesticated 
animals  ;  and  in  most  parts  of  the  world  inhabited  by  wild  cattle,  there  are  spots 
where  it  exists  in  the  soil,  and  to  which  they  resort  to  obtain  it.  Such  are  the 
"  buffalo  licks"  of  North  America.  Phosphorus  exists  also  in  the  yolk  and  white 
of  the  Egg,  and  in  Milk, — the  substances  on  which  the  young  animal  subsists 
during  the  period  of  its  most  rapid  growth  ;  and  it  abounds,  not  only  in  many 
animal  substances  used  as  food,  but  also  (in  the  state  of  phosphate  of  lime  or 
bone-earth)  in  the  seeds  of  many  plants,  especially  the  grasses.  In  smaller 
quantities  it  is  found  in  the  ashes  of  almost  every  plant.  When  flesh,  bread, 
fruit,  and  husks  of  grain,  are  used  as  the  chief  articles  of  food,  more  phosphorus 
is  taken  into  the  body  than  it  requires  ;  and  the  excess  has  to  be  carried  out  in 
the  excretions.  Sulphur  is  derived  alike  from  vegetable  and  animal  substances. 
It  exists  in  flesh,  eggs,  and  milk ;  also  in  the  azotized  compounds  of  plants ; 
and  (in  the  form  of  sulphate  of  lime)  in  most  of  the  river  and  spring-water  that 
we  drink.  Iron  is  found  in  the  yolk  of  egg,  and  in  milk,  as  well  as  in  animal 
flesh;  it  also  exists  in  small  quantities  in  most  vegetable  substances  used  as 
food  by  Man, — such  as  potatoes,  cabbage,  peas,  cucumbers,  mustard,  &c. ; 
and  probably  in  most  articles,  from  which  other  animals  derive  their  support. 
Lime  is  one  of  the  most  universally  diffused  of  all  mineral  bodies ;  for  there 
are  very  few  animal  or  vegetable  substances,  in  wfiich  it  does  not  exist.  It 
is  most  commonly  taken  in,  among  the  higher  animals,  combined  with  Phos- 
phoric acid ;  and  in  this  state  it  exists  largely  in  the  seeds  of  most  grasses, 
especially  in  wheat  flour.  If  it  were  not  for  their  deficiency  in  Phosphate 
of  lime,  some  of  the  Leguminous  seeds  would  be  more  nutritious  than  wheaten 
flour ;  the  proportion  of  azotized  matter  they  contain  being  greater.  A  con- 
siderable quantity  of  lime  exists,  in  the  state  of  carbonate  and  sulphate,  in  all 
hard  water. 

649.  The  absolute  quantity  of  food,  required  for  the  maintenance  of  the 
Human  body  in  health,  varies  so  much  with  the  age,  sex,  and  constitution 
of  the  individual,  and  with  the  circumstances  in  which  he  may  be  placed, 
that  it  would  be  absurd  to  attempt  to  fix  any  standard  which  should  apply  to 
every  particular  case.  The  appetite  is  the  only  sure  guide  for  the  supply  of 
the  wants  of  each ;  but  its  indications  must  not  be  misinterpreted.  To  eat 
when  we  are  hungry,  is  an  evidently  natural  disposition ;  but  to  eat  as  long 
as  we  are  hungry,  may  not  always  be  prudent.  Since  the  feeling  of  hunger 
does  not  depend  so  much  upon  the  state  of  fulness  or  emptiness  of  the  sto- 
mach, as  upon  the  condition  of  the  general  system,  it  appears  evident  that  the 
ingestion  of  food  cannot  at  once  produce  the  effect  of  dissipating  it,  though 
it  will  do  so  after  a  short  time  ;  so  that,  if  we  eat  with  undue  rapidity,  we 
may  continue  swallowing  food  long  after  we  have  taken  as  much  as  will  really 
be  required  for  the  wants  of  the  system  ;  and  every  superfluous  particle  is 
not  merely  useless,  but  injurious.  Hence,  besides  its  other  important  ends, 
the  process  of  thorough  mastication  is  important,  as  prolonging  the  meal, 
and  giving  time  to  the  system  to  become  acquainted  (as  it  were)  that  the  sup- 
ply of  its  wants  is  in  progress  ;  sovthat  its  demand  may  be  abated  in  due  time 
to  prevent  the  ingestion  of  more  than  is  required.  It  is  very  justly  remarked 
by  Dr.  Beaumont,  that  the  cessation  of  this  demand,  rather  than  the  positive 


REQUISITE  AMOUNT  OF  FOOD.  489 

sense  of  satiety,  is  the  proper  guide.  "  There  appears  to  be  a  sense  of  per- 
fect intelligence  conveyed  to  the  encephalic  centre,  which,  in  health,  invariably 
dictates  what  quantity  of  aliment  (responding  to  the  sense  of  hunger  and  its 
due  satisfaction)  is  naturally  required  for  the  purposes  of  life ;  and  which,  if 
noticed  and  properly  attended  to,  would  prove  the  most  salutary  monitor  of 
health,  and  effectual  preventive  of  disease.  It  is  not  the  sense  of  satiety, 
for  this  is  beyond  the  point  of  healthful  indulgence,  and  is  Nature's  earliest 
indication  of  an  abuse  and  overburden  of  her  powers  to  replenish  the  system. 
It  occurs  immediately  previous  to  this  ;  and  may  be  known  by  the  pleasurable 
sensations  of  perfect  satisfaction,  ease  and  quiescence  of  body  and  mind.  It 
is  when  the  stomach  says,  enough  ;  and  it  is  distinguished  from  satiety  by 
the  difference  of  sensations, — the  latter  saying  too  much"  Every  medical 
man  is  well  aware  how  generally  this  rule  is  transgressed ;  some  persons 
making  a  regular  practice  of  eating  to  repletion  ;  and  others  paying  far  too 
little  attention  to  the  preliminary  operations,  and  thus  ingesting  more  than  is 
good  for  them,  even  though  they  may  actually  leave  off  with  an  appetite. 

650.  Although  no  universal  law  can  be  laid  down  for  individuals,  however, 
it  is  a  matter  of  much  practical  importance  to  be  able  to  form  a  correct  ave- 
rage estimate.  It  is  from  the  experience  afforded  by  the  usual  consumption 
of  food  by  large  bodies  of  men,  that  our  data  are  obtained  ;  and  these  data 
are  sufficient  to  enable  us  to  predict  with  tolerable  accuracy  what  will  be  re- 
quired by  similar  aggregations,  though  they  can  afford  no  guide  to  the  con- 
sumption of  individuals. — We  shall  first  consider  the  quantity  sufficient  for 
men  in  regular  active  exercise  ;  and  then  inquire  how  far  that  may  be  safely 
reduced  for  those  who  lead  a  more  sedentary  life. — The  Diet-scale  of  the 
British  Navy  may  be  advantageously  taken  as  a  specimen  of  what  is  required 
for  the  first  class.  It  is  well  known  that  an  extraordinary  improvement  has 
taken  place  in  the  health  of  seamen  during  the  last  80  years ;  so  that  three 
ships  can  now  be  kept  afloat  with  only  the  same  number  of  men,  which  were 
formerly  required  for  two.  This  is  due  to  the  improvement  in  the  quality  of 
the  food,  in  combination  with  other  prophylactic  means.  At  present  it  may 
safely  be  affirmed,  that  it  would  not  be  easy  to  conceive  of  any  diet-scale 
more  adapted  to  answer  the  required  purpose.  The  health  of  crews  that 
have  been  long  afloat,  and  have  been  exposed  to  every  variety  of  external 
conditions,  appears  to  be  preserved  (at  least  when  they  are  under  the  direc- 
tion of  judicious  officers),  to  the  full  as  well  as  that  of  persons  subject  to 
similar  vicissitudes  on  shore  ;  and  there  can  be  no  complaint  of  insufficiency 
of  food,  although  the  allowance  cannot  be  regarded  as  superfluous.  It  con- 
sists of  from  31  to  35|  ounces  of  dry  nutritious  matter  daily ;  of  this  26  oz. 
are  vegetable  ;  and  the  rest  animal ;  9  toz.  of  salt  meat,  or  4<|  oz.  fresh, 
being  the  allowance  of  the  latter.  This  is  found  to  be  amply  sufficient 
for  the  support  of  strength  ;  and  considerable  variety  is  produced,  by  ex- 
changing various  parts  of  the  diet  for  other  articles.  This,  however,  is  some- 
times done  erroneously ;  thus  8  oz.  of  fresh  vegetables,  which  contain  only 
1%  oz.  of  solid  nutriment,  are  exchanged  for  12  oz.  of  flour,  which  is  almost 
all  nutritious.  Sugar  and  Cocoa  are  also  allowed  ;  partly  in  exchange  for  a 
portion  of  the  Spirits  formerly  served  out,  the  diminution  of  which,  especially 
in  the  case  of  boys,  has  been  attended  with  great  benefit. 

651.  A  considerable  reduction  in  this  amount  is  of  course  admissible, 
where  little  bodily  exertion  is  required,  and  where  there  is  less  exposure  to 
low  temperatures.  In  the  case  of  Prisoners,  the  diet  should  of  course  be  as 
spare  as  possible,  consistently  with  health ;  but  it  should  be  carefully  modi- 
fied, in  individual  cases,  according  to  several  collateral  circumstances,  such 
as  depression  of  mind,  compulsory  labour,  previous  intemperate  habits,  and 
.  especially  the  length  of  confinement.  It  has  been  supposed  by  some,  that 


490  OF  FOOD,  AND  THE  DIGESTIVE  PROCESS. 

prisoners  require  a  fuller  diet  than  persons  at  large ;  this  is  probably  erro- 
neous ;  but  more  variety  is  certainly  desirable,  to  counteract,  as  far  as  possi- 
ble, the  depressing  influence  of  their  condition  upon  the  digestive  powers. 
The  circumstances  which  occurred  at  the  Milbank  Penitentiary  in  1823,  form 
a  lamentable  warning  against  the  reduction  of  the  diet-scale  to  an  insufficient 
amount.  The  allowance  to  the  prisoners  had  formerly  been  from  31  to  33 
oz.  of  dry  nutriment  daily,  and  the  prison  was  considered  healthy ;  but  in 
1822,  it  was  reduced  to  21  oz.  The  health  of  the  prisoners  continued  un- 
broken for  nearly  six  months  ;  but  scurvy  then  showed  itself  unequivocally, 
and  out  of  860  prisoners,  437,  or  52  per  cent.,  were  affected  with  it.  The 
effect  of  previous  confinement  here  became  remarkable ;  for  those  were  chiefly 
attacked,  who  had  been  in  the  prison  for  two  years,  a' year,  or  six  months. 
Again,  the  prisoners  employed  in  the  kitchen,  who  had  8  oz.  of  bread  addi- 
tional per  day,  were  not  attacked,  except  three  who  had  only  been  there  a 
few  days.  After  the  epidemic  had  spread  to  a  great  extent,  it  was  found  that 
the  addition  of  8  oz.  to  the  daily  allowance  of  vegetable  food,  and  |  oz.  to 
the  animal,  facilitated  the  operation  of  the  remedies  which  were  used  for  the 
restoration  of  the  health  of  the  prisoners. — The  effects  of  confinement  have 
been  further  shown  in  the  experience  of  the  Edinburgh  House  of  Refuge, 
which  was  first  established  in  1832,  for  the  reception  of  beggars  during  the 
cholera,  and  which  has  been  continued  to  the  present  time.  The  diet  was  at 
first  a  quart  of  oatmeal  porridge  for  each  person,  morning  and  evening  ;  and 
at  dinner  1  oz.  of  meat,  in  broth,  with  7  oz.  of  bread  ;  making  altogether 
about  23  oz.  of  solid  food  a  day.  During  some  months,  this  diet  seemed  to 
answer  very  well ;  the  people  went  out  fatter  than  they  came  in,  owing  to 
the  diet  being  better  than  that  to  which  they  had  been  accustomed ;  but  after- 
wards a  proneness  to  disease  manifested  itself  in  those  who  had  been  resi- 
dents there  for  a  considerable  time,  and  the  diet  was  therefore  somewhat  in- 
creased, with  good  effect.  The  quantity  of  animal  food  was  probably  here 
too  small ;  and  the  total  weight  might  still  have  been  sufficient,  if  it  had 
been  differently  apportioned. — In  a  Convict-ship,  which  took  out  433  prison- 
ers to  New  Holland  in  1802,  the  mortality  was  very  trifling,  and  the  general 
health  good ;  although  these  prisoners  were  supported  on  16  oz.  of  vegetable 
food,  and  7k  oz.  of  animal  food  per  day ;  a  quantity  which  was  found  to  be 
perfectly  sufficient  for  them. — The  aged  inmates  of  work-houses,  especially 
those  who  have  been  accustomed  to  poor  food  during  their  whole  lives,  re- 
quire much  less  than  this  ;  their  vital  functions  being  comparatively  inactive, 
and  their  amount  of  labour  or  exercise  small.  In  the  Edinburgh  work-house, 
of  which  the  inmates  usually  have  good  health,  they  are  fed  upon  oatmeal- 
porridge  morning  and  evening,  with  barley-broth  at  dinner ;  the  total  allow- 
ance of  dry  nutriment  is  about  17  oz.  ;  namely  13  oz.  vegetable,  and  4  oz. 
animal. 

652.  It  is  a  curious  effect  of  insufficient  nutriment,  as  shown  by  the  recent 
inquiries  of  Chossat,*  that  it  produces  an  incapability  of  digesting  even  the 
limited  amount  supplied.  He  found  that,  when  turtle-doves  were  supplied 
with  limited  quantities  of  corn,  but  with  water  at  discretion,  the  whole  amount 
of  food  taken  was  scarcely  ever  actually  digested  ;  a  part  of  it  being  rejected  by 
vomiting,  or  passing  off  by  diarrhea,  or  accumulating  in  the  crops.  It  seems 
as  if  the  vital  powers  were  not  sufficient  to  furnish  the  requisite  supply  of 
gastric  fluid,  when  the  body  began  to  be  enfeebled  by  insufficient  nutrition ; 
or  perhaps  we  might  well  say,  the  materials  of  the  gastric  fluid  were  wanting. 
Hence  the  loathing  of  food,  which  is  often  manifested  by  those  who  have 
been  subjected  to  the  influence  of  an  insufficient  diet-scale  in  our  prisons  and 

*  Recherches  Experimentales  sur  1'Inanition,  1843. 


REQUISITE  AMOUNT  OF  FOOD.  491 

poor-houses,  and  which  has  been  set  down  to  caprice  or  obstinacy,  and  pun- 
ished accordingly,  may  be  actually  a  proof  of  the  deficiency  of  the  supply 
which  we  might  expect  to  have  been  voraciously  devoured,  if  really  less  than 
the  wants  of  the  system  require. 

653.  The  smallest  quantity  of  food  upon  which  life  is  known  to  have  been 
supported  with  vigour,  during  a  prolonged  period,  is  that  on  which  Cornaro 
states  himself  to  have  subsisted.  This  was  no  more  than  12  oz.  a  day, 
chiefly  of  vegetable  matter,  for  a  period  of  58  years.  There  is  only  one  in- 
stance on  record,  in  which  his  plan  was  followed  ;  and  there  are  probably  few 
who  could  long  persevere  in  it,  at  least  among  those  whose  avocations  require 
much  mental  or  bodily  exertion.  It  is  certain,  however,  that  life  with  a  mode- 
rate amount  of  vigour  may  be  preserved  for  some  time,  with  a  very  limited 
amount  of  food ;  this  appears  from  the  records  of  shipwreck  and  similar  dis- 
asters. In  regard,  however,  to  those  who  have  been  stated  to  fast  for  a  period 
of  months  or  even  years,  taking  no  nutriment,  but  maintaining  an  active  con- 
dition, it  may  be  safely  asserted  that  they  were  impostors, — probably  possess- 
ing unusual  powers  of  abstinence,  which  they  took  care  to  magnify.  The 
instances  in  which  the  life  of  Man,  or  of  other  Mammalia,  has  been  prolonged 
to  the  greatest  extent  without  water,  are  those  in  which,  from  the  peculiarity 
of  the  circumstances,  the  cutaneous  exhalation  must  have  been  reduced  to  a 
very  small  amount,  or  in  which  there  may  have  been  an  actual  absorption  of 
water  by  the  skin  and  lungs.  Thus,  Fodere  mentions  that  some  workmen 
were  extricated  alive,  after  fourteen  days'  confinement  in  a  cold  damp  cavern, 
in  which  they  had  been  buried  under  a  ruin.  And  there  is  a  well-known  case 
of  a  Hog,  which  was  buried  in  its  sty  for  160  days,  under  thirty  feet  of  the 
chalk  of  Dover  cliff,  and  was  dug  out  alive  at  the  end  of  that  time,  reduced  in 
weight  from  160  Ibs.  to  40  Ibs. :  here  the  temperature  would  be  kept  up  by  the 
non-conducting  power  of  the  chalk  around;  and  the  air  surrounding  the  ani- 
mal would  soon  become  sufficiently  charged  with  fluid,  to  resist  further  evapo- 
ration. The  time  during  which  life  can  be  supported  under  total  abstinence, 
is  usually  stated  to  vary  from  8  to  10  days  :  the  period  may  be  greatly 
prolonged,  however,  by  the  occasional  use  of  water,  and  still  more  by  a  very 
small  supply  of  food.  In  a  case  recorded  by  Dr.  Willan,  of  a  young  gentle- 
man who  starved  himself,  under  the  influence  of  a  religious  delusion,  life  was 
prolonged  for  60  days ;  during  the  whole  of  which  time  nothing  else  was 
taken  than  a  little  orange-juice.  In  a  somewhat  similar  case  which  occurred 
under  the  Author's  notice,  in  the  person  of  a  young  French  lady,  more  than 
15  days  elapsed  between  the  time  that  she  ceased  to  eat  regularly,  and 
the  time  of  her  being  compelled  to  take  nourishment ;  during  this  period  she 
took  a  great  deal  of  exercise,  and  her  strength  seemed  to  suffer  but  little,  al- 
though she  swallowed  solid  food  only  once,  and  then  in  small  quantity.  If 
the  cessation  of  muscular  exertion  be  complete,  it  seems  that  life  is  usually 
more  prolonged  than  where  exercise  of  any  kind  is  performed  ;  and  this  is 
what  might  naturally  be  expected. — In  certain  states  of  the  system  commonly 
known  as  Hysterical,  there  is  frequently  a  very  remarkable  disposition  for  ab- 
stinence, and  power  of  sustaining  it.  In  a  case  of  this  kind  which  occurred 
under  the  Author's  own  notice,  a  young  lady,  who  had  suffered  severely  from 
the  tetanic  form  of  Hysteria,  was'unable  to  take  food  for  three  weeks.  The 
slightest  attempt  to  introduce  a  mcfrspl  of  solid  matter  into  the  stomach,  oc- 
casioned very  severe  vomiting  and  retching ;  and  the  only  nourishment  taken 
during  the  period  mentioned,  was  a  cup  of  tea  once  or  twice  a  day, — on  many 
days  not  even  this  being  swallowed.  Yet  the  strength  of  the  patient  rather 
increased  than  diminished,  during  this  period ;  her  muscles  became  firmer, 
and  her  voice  more  powerful. — It  may  be  well  to  remark  that,  under  such 
circumstances,  the  continual  persuasions  of  anxious  friends  are  very  injurious 


492  OF  FOOD,  AND  THE  DIGESTIVE  PROCESS. 

to  the  patient ;  whose  return  to  her  usual  state  will  probably  take  place  the 
earlier,  the  more  completely  she  is  left  to  herself. 

654.  Of  the  quantity  which  can  be   devoured  at  a  time,  it  is  scarcely  the 
place  to  speak;  since  such  feats  of  gluttony  only  demonstrate  the  extraordi- 
nary capacity,  which  the  stomach  may  be  made  to  attain  by  continual  practice. 
Many  amusing  instances  are  related  by  Captain  Parry  in  his  Arctic  Voyages ; 
in  one  case,  a  young  Esquimaux,  to  whom  he  had  given  (for  the  sake  of  cu- 
riosity) his  full  tether,  devoured  in  four-and-twenty  hours,  no  less  than  35lbs. 
of  various  kinds  of  aliment,  including  tallow  candles.     A  case  has  recently 
been  published  of  a  Hindoo,  who  can  eat  a  whole  sheep  at  a  time  ;  this  pro- 
bably surpasses  any  other  instance  on  record.     The  half-breed  voyageurs  of 
Canada,  according  to  Captain  Franklin,  and  the  wandering  Cossacks  of  Sibe- 
ria, as   testified  by  Capt.  Cochrane,  habitually  devour  a  quantity  of  animal 
food,  which  would  be  soon  fatal  to  any  one  unused  to  it.     The  former  are 
spoken  of  as  very  discontented,  when  put  on  a  short  allowance  of  81bs.  of 
meat  a  day;  their  usual  consumption  being  from  12  to  20lbs. — That  a  much 
larger  quantity  of  food  than  that  formerly  specified,  may  be  taken,  with  per- 
fect freedom  from  injurious  consequences,  under  a  particular  system  of  exer- 
cise, &c.,  appears  from  the  experience  of  those  who  are  trained  for  feats  of 
strength,  pugilistic  encounters,  &c.     The   ordinary  belief,  that  the   Athletic 
constitution  cannot  be  long  maintained,  appears  to  have  no  real  foundation ; 
nor  does  it  appear  that  any  ultimate  injury  results  from  the  system  being  per- 
severed in  for  some  time.     That  trained  men  often  fall  into  bad  health,  on 
the  cessation  of  the  plan,  is  probably  owing  in  part  to  the  intemperance  and 
other  bad  habits  of  persons  of  the  class  usually  subjected  to  this  discipline. 
The  effects  of  trainers'  regimen  are   hardness  and  firmness  of  the  muscles, 
clearness  of  the  skin,  capability  of  bearing  continued  severe  exercise,  and  a 
feeling  of  freedom  and  lightness  (or  "  corkiness")  in  the  limbs.     During  the 
continuance  of  the  system,  it  is  found  that  the  body  recovers  with  wonderful 
facility  from  the   effects  of  injuries  ;  wounds  heal  very  rapidly ;  cutaneous 
eruptions  usually  disappear.     Clearness  and  vigour  of  mind,  also,  are  stated 
to  be  results  of  this  plan  ;  and  it  is  probable  that,  where  persevering  attention 
and  intense  application  are  necessary,  a  modification  of  this  system,  in  which 
due  allowance  should  be  made  for  the  diminished  quantity  of  exercise,  would 
be  found  advantageous.* 

3. — Of  the  Passage  of  Food  along  the  Alimentary  Canal. 

655.  The  introduction  of  alimentary  matter  into  the  system,  is  accomplished 
in  Animals  by  the  reception  of  the  food  into  an  internal  cavity,  where  it  is 
subjected  to  a  preparatory  process,  to  which  nothing  analogous  exists  in  Plants, 
and  which  is  termed  Digestion.     This  process  may  be  said  to  have  three  dif- 
ferent purposes  in  view  ; — the  reduction  of  the  alimentary  matter  to  a  fluid 
form,  so  that  it  may  become  capable  of  absorption ; — the  separation  of  that 

*  The  method  of  training  employed  by  Jackson  (a  celebrated  trainer  of  prize-fighters  in 
modern  times),  as  deduced  from  his  answers  to  questions  put  to  him  by  John  Bell,  was  to 
begin  on  a  clear  foundation,  by  an  emetic  and  two  or  three  purges.  Beef  and  mutton, 
the  lean  of  fat  meat  being  preferred,  constituted  the  principal  food ;  veal,  lamb,  and  pork 
were  said  to  be  less  digestible  ("  the  last  purges  some  men").  Fish  was  said  to  be  a  "  wa- 
tery kind  of  diet:"  and  is  employed  by  jockeys  who  wish  to  reduce  weight  by  sweating. 
Stale  bread  was  the  only  vegetable  food  allowed.  The  quantity  of  fluid  permitted  was  3£ 
pints  per  diem  ;  but  fermented  liquors  were  strictly  forbidden.  Two  full  meals,  with  a  light 
supper,  were  usually  taken.  The  quantity  of  exercise  employed  was  very  considerable,  and 
such  as  few  men  of  ordinary  strength  could  endure.  This  account  corresponds  very  much 
with  that  which  Hunter  gave  of  the  North  American  Indians,  when  about  to  set  out  on  a  long 
march. 


DIGESTIVE  APPARATUS. 


493 


portion  of  it  which  is  fit  to  be  assimilated  or  converted  into  organized  texture, 
from  that  which  cannot  serve  this  purpose,  and  which  is  at  once  rejected  ; — 
and  the  alteration  (when  required)  of  the  chemical  constitution  of  the  former, 


[Fig.  199. 


A  view  of  the  Organs  of  Digestion,  opened  in  nearly  their  whole  length;  a  portion  of  the  cesophagus 
has  been  removed  on  account  of  want  of  space  in  the  figure  ;  the  arrows  indicate  the  course  of  sub- 
stances along  the  canal ;  1,  the  upper  lip,  turned  off  the  mouth ;  2,  its  frasnum  ;  3,  the  lower  lip,  turned 
down;  4,  its  frsenum;  5,  5,  inside  of  the  cheeks,  covered  by  the  lining  membrane  of  the  mouth  ;  6,  points 
to  the  opening  of  the  duct  of  Steno ;  7,  roof  of  the  mouth;  8,  lateral  half  arches  ;  9,  points  to  the  tonsils; 
10,  velum  pendulum  palati ;  11,  surface  of  the  tongue  ;  12,  papillae  near  its  point ;  13,  a  portion  of  the 
trachea ;  14,  the  oesophagus ;  15,  its  internal  surface  ;  16,  inside  of  the  stomach;  17,  its  greater  extremity 
or  great  cul-de-sac  ;  18,  its  lesser  extremity  or  smaller  cul-de-sac ;  19,  its  lesser  curvature ;  20,  its  greater 
curvature;  21,  the  cardiac  orifice;  22,  the  pyloric  orifice;  23,  upper  portion  of  duodenum;  24,  25,  the 
remainder  of  the  duodenum  ;  26,  its  valvulae  conniventes  ;  27,  the  gall  bladder;  28,  the  cystic  duct;  29, 
division  of  hepatic  ducts  in  the  liver;  30,  hepatic  duct;  31,  ductus  communis  choledochus  ;  32,  its  open- 
ing into  the  duodenum  ;  33,  ductus  Wirsungii,  or  pancreatic  duct ;  34,  its  opening  into  the  duodenum J 
35,  upper  part  of  jejunum ;  36,  the  ileum ;  37,  some  of  the  valvuloe  conniventes ;  38,  lower  extremity 
of  the  ileum  ;  39,  ileo-colic  valve  ;  40,  41,  cfficum,  or  caput  coli ;  42,  appendicula  vermiformis ;  43.  44, 
ascending  colon ;  45,  transverse  colon ;  46,  47,  descending  colon ;  48,  sigmoid  flexure  of  the  colon ; 
49,  upper  portion  of  the  rectum ;  50,  its  lower  extremity ;  51,  portion  of  the  levator-ani  muscle ;  52, 
the  anus.] 

42 


494  OF  FOOD,  AND  THE  DIGESTIVE  PROCESS. 

which  prepares  it  for  the  important  changes  it  is  subsequently  to  undergo. 
The  simplest  conditions  requisite  for  the  accomplishment  of  these  purposes 
are  the  following: — a  fluid  capable  of  performing  the  solution  and  of  effecting 
the  required  chemical  changes ; — a  fluid  capable  of  separating  the  unorganiz- 
able  matter,  by  a  process  analogous  to  chemical  precipitation ; — and  a  cavity 
or  sac,  in  which  these  operations  may  be  performed.  In  the  lowest  Animals, 
we  find  this  cavity  formed  on  a  very  simple  plan  ;  being  evidently  nothing 
else  than  an  inversion  of  the  external  integument,  communicating  with  the 
exterior  by  one  orifice  only,  through  which  the  food  is  drawn  in  and  the  ex- 
crementitious  matter  rejected.  The  fluid  necessary  to  dissolve  the  food,  which 
is  known  by  the  name  of  gastric  fluid  or  juice,  and  that  required  to  separate 
the  portion  which  is  to  be  thrown  off,  which  is  known  as  the  bile,  are  secreted 
in  the  walls  of  the  stomach.  In  the  Sea-Anemone,  which  affords  a  very  charac- 
teristic example  of  this  type  of  structure,  it  cannot  be  ascertained  that  the  very 
rapid  solution  of  food,  which  takes  place  in  the  digestive  cavity,  is  assisted 
by  any  movement  of  its  walls.  In  Polypes  of  a  higher  conformation,  how- 
ever, the  digestive  cavity  is  provided  with  a  second  orifice  ;  the  stomach  opens 
into  an  intestinal  tube,  through  which  the  excrement  is  rejected  in  little  pellets  ; 
and  the  food,  before  entering  the  true  digestive  cavity,  is  submitted  to  a  pow- 
erful gizzard  or  triturating  apparatus.  Still,  .the  bile,  like  the  gastric  juice,  is 
secreted  in  the  walls  of  the  stomach;  as  may  be  distinctly  perceived  in  many 
of  these  animals,  on  account  of  their  transparency,  and  the  bright  yellow  co- 
lour of  the  fluid.  As  we  ascend  the  animal  series,  we  find  no  essential  change 
in  the  character  of  the  digestive  apparatus.  The  biliary  follicles  are  gradu- 
ally collected  into  a  glandular  mass,  which  is  altogether  removed  from  the 
walls  of  the  stomach,  and  which  pours  its  secretion  into  the  intestinal  tube, 
at  a  short  distance  from  its  commencement;  the  gastric  juice,  however,  is  still 
secreted  in  minute  sacs  imbedded  in  the  substance  of  the  membrane.  Several 
accessory  glands  are  added,  the  uses  of  which  are  not  accurately  known;  and 
particular  modifications  of  the  apparatus  are  adapted  to  peculiarities  in  the 
nature  of  the  food,  or  in  the  mode  of  its  ingestion.  As  a  general  rule  it  may 
be  stated,  that  the  digestive  apparatus  is  most  simple  in  Carnivorous  animals, 
in  which  it  has  to  effect  little  change  upon  the  aliment  except  solution,  in  or- 
der to  bring  it  to  the  state  fit  for  absorption  ;  whilst  it  is  most  complex  in  those 
that  feed  upon  Vegetable  matter,  Which  needs  to  undergo  a  greater  change, 
both  in  its  chemical  composition  and  in  the  mechanical  arrangement  of  its 
components,  before  it  can  be  rendered  subservient  to  animal  nutrition. 

656.  Mastication  and  Deglutition. — The  first  step  in  the  process  of  reduc- 
tion, is  the  Mastication  of  the  food,  and  the  impregnation  of  its  comminuted 
particles  with  the  Salivary  secretion.  Mastication  is  evidently  of  great  im- 
portance, in  preparing  the  substances  to  be  afterwards  operated  on,  for  the 
action  of  their  solvent;  and  it  exactly  corresponds  with  the  trituration  to 
which  the  Chemist  would  submit  any  solid  matter,  that  he  might  present  it  in 
the  most  advantageous  form  to  a  digestive  menstruum.  The  complete  disin- 
tegration of  the  alimentary  matter,  therefore,  is  of  great  consequence ;  and,  if 
imperfectly  effected,  the  subsequent  processes  are  liable  to  derangement.  This 
derangement  we  continually  meet  with:  for  there  is  not,  perhaps,  a  more  fre- 
quent source  of  Dyspepsia  than  imperfect  mastication,  whether  resulting  from 
the  haste  with  which  the  food  is  swallowed,  or  from  the  want  of  the  proper 
instruments.  The  disintegration  of  the  food  by  mechanical  reduction,  is  mani- 
festly aided  by  Insalivation:  and  the  admixture  of  Saliva  appears  further  to 
have  the  effect  of  commencing  the  transformation  of  the  amylaceous  or  starchy- 
particles  into  sugar.  From  recent  experiments  it  would  seem  that  Saliva,  if 
acidulated,  possesses  the  same  power  of  acting  on  azotized  compounds,  as  that 
which  characterizes  the  gastric  juice;  and  consequently,  when  introduced  into 


MASTICATION  AND  DEGLUTITION. 


495 


the  stomach,  the  Saliva  may  afford  important  aid  in  the  digestive  process. 
(See  §§  668  and  863.)  When  the  reduction  of  the  food  in  the  mouth  has 
been  sufficiently  accomplished,  it  is  carried  into  the  oesophagus  by  the  action 
of  Deglutition.  The  share  which  the  nervous  system  has  in  this  action  has 
been  already  stated  (§  382) ;  and  it  here  only  remains  to  define  more  pre 
cisely  the  different  movements  which  are  concerned  in  it.  These  were  first 
described  in  detail  by  Magendie;  but  his  account  requires  some  modification, 
through  the  more  recent  observations  of  DzondL*  The^rsJ  stage  in  the  pro- 
cess is  the  carrying  back  of  the  food,  until  it  has  passed  the  anterior  palatine 
arch ;  this,  which  is  effected  by  the  approximation  of  the  tongue  and  the 

[Fig.  200. 


A  view  of  the  Muscles  of  the  Tongue,  Palate,  Larynx  and  Pharynx— as  well  as  the  position  of  the 
upper  portion  of  the  CEsophagus,  as  shown  by  a  vertical  section  of  the  head;  1,  1.  the  vertical  section  of 
the  head  ;  2,  points  to  the  spinal  canal ;  3,  section  of  the  hard  palate ;  4,  inferior  spongy  bone  ;  5.  middle 
spongy  bone  ;  6,  orifice  of  the  right  nostril ;  7,  section  of  the  inferior  maxilla ;  8,  section  of  the  os  hyoides ; 
9,  section  of  the  epiglottis;  10,  section  of  the  cricoid  cartilage;  11,  the  trachea,  covered  by  its  lining  mem- 
brane; 12,  section  of  sternum;  13,  inside  of  the  upper  portion  of  the  thorax;  14,  genio-hyo-glossus  muscle; 
15,  its  origin  ;  16, 17,  the  fan-like  expansion  of  the  fibres  of  this  muscle  ;  18,  superficial  linguae  muscle ; 
19,  verticales  linguse  muscle;  20,  genio-hyoideus  muscle;  21,  mylo-hyoideus  muscle;  22,  anterior  belly 
of  digastricus ;  23,  section  of  platysmamyoides;  24,  levator  menti ;  25,  orbicularis  oris;  26,  orifice  of  Eus- 
tachian  tube  ;  27,  levator  palati ;  28,  internal  pterygoid  ;  29,  section  of  velum  pendulum  palati,  and  azy- 
gos  uvulae  muscle;  30,  sty lo-pharyngeus  ;  31,  constrictor  pharyngis  superior  ;  32.  constrictor  pharyngis 
medius>  33,  insertion  stylo-pharyngeus;  34,  constrictor  pharyngis  inferior ;  35,  36,  37,  muscular  coat  of 
ossophagus;  38,  thyreo-arytenoid  muscle  and  ligaments,  and  above  is  the  ventricle  of  Galen:  39,  section 
of  arytenoid  cartilage  ;  40,  border  of  sterno-hyoideus.] 

palate,  is  a  purely  voluntary  movement.  In  the  second  stage,  the  tongue  is 
carried  still  further  backwards,  and  the  larynx  is  drawn  forwards  under  its 
root,  so  that  the  epiglottis  is  depressed  down  over  the  rima  glottidis.  The 
muscles  of  the  anterior  palatine  arch  contract  after  the  morsel  has  passed  it, 
and  assist  its  passage  backwards;  these,  with  the  tongue,  cut  off  completely 
the  communication  between  the  fauces  and  the  mouth.  At  the  same  time,  the 
muscles  of  the  posterior  palatine  arch  contract  in  such  a  manner,  as  to  cause 

*  Muller's  Physiology,  p.  501. 


496  OF  FOOD,  AND  THE  DIGESTIVE  PROCESS. 

the  sides  of  the  arch  to  approach  each  other  like  a  pair  of  curtains ;  so  that 
the  passage  from  the  fauces  into  the  posterior  nares  is  nearly  closed  by  them ; 
and  to  the  cleft  between  the  approximated  sides,  the  uvula  is  applied  like  a 
valve.  A  sort  of  inclined  plane,  directed  obliquely  downwards  and  backwards, 
is  thus  formed;  and  the  morsel  slides  along  it  into  the  pharynx,  which  is 
brought  up  to  receive  it.  Some  of  these  acts  may  be  performed  voluntarily; 
but  the  combination  of  the  whole  is  automatic.  The  third  stage  of  the  pro- 
cess,— the  propulsion  of  the  food  down  the  oesophagus, — then  commences. 
This  is  accomplished  in  the  upper  part  by  means  of  the  constrictors  of  the 
pharynx;  and  in  the  lower  by  the  muscular  coat  of  the  oesophagus  itself. 
When  the  morsels  are  small,  and  are  mixed  with  much  fluid,  the  undulating 
movements  from  above  downwards  succeed  each  other  very  rapidly;  this 
may  be  well  observed  in  Horses  whilst  drinking;  large  morsels,  however,  are 
frequently  some  time  in  making  their  way  down.  Each  portion  of  food  and 
drink  is  included  in  the  contractile  walls,  which  are  closely  applied  to  it  during 
the  whole  of  its  transit.  The  gurgling  sound,  which  is  observed  when  drink 
is  poured  down  the  throat  of  a  person  in  articulo  mortis,  is  due  to  the  want 
of  this  contraction.  The  whole  of  the  third  stage  is  completely  involuntary. 
At  the  point  where  the  oesophagus  enters  the  stomach, — the  cardiac  orifice  of 
the  latter, — there  is  a  sort  of  sphincter,  which  is  usually  closed.  This  opens 
when  there  is  a  sufficient  pressure  on  it,  made  by  accumulated  food;  and  after- 
wards closes,  so  as  to  retain  the  food  in  the  stomach.  The  opening  of  the 
cardiac  is  one  of  the  first  acts  which  takes  place  in  vomiting.  When  the 
sphincter  is  paralyzed  by  division  of  the  pneumogastric  nerve,  the  food  regur- 
gitates into  the  oesophagus. 

657.  Action  of  the  Stomach. — A  remarkable  opportunity  of  ascertaining  the 
condition  of  the  Stomach  during  Digestion,  presented  itself,  some  time  since, 
in  a  case  in  which  a  large  fistulous  aperture  remained  after  a  wound  that  laid 
open  the  cavity,  but  in  which  the  general  health  was  completely  recovered; 
so  that  the  process  may  be  considered  as  having  been  normally  performed.* 
"  The  inner  coat  of  the  stomach,  in  its  natural  and  healthy  state,  is  of  a  light 
or  pale  pink  colour,  varying  in  its  hues,  according  to  its  full  or  empty  state. 
It  is  of  a  soft  or  velvet-like  appearance,  and  is  constantly  covered  with  a  very 
thin,  transparent,  viscid  mucus,  lining  the  whole  interior  of  the  organ.  By 
applying  aliment  or  other  irritants,  to  the  internal  coat  of  the  stomach,  and 
observing  the  effect  through  a  magnifying  glass,  innumerable  lucid  points,  and 
very  fine  nervous  or  vascular  papillae,  can  be  seen  arising  from  the  villous 
membrane,  and  protruding  through  the  mucous  coat,  from  which  distils  a  pure, 
limpid,  colourless,  slightly  viscid  fluid.  The  fluid  thus  excited  is  invariably 
distinctly  acid.  The  mucus  of  the  stomach  is  less  fluid,  more  viscid  or  albu- 
minous, semi-opaque,  sometimes  a  little  saltish,  and  does  not  possess  the  slight- 
est character  of  acidity.  The  gastric  fluid  never  appears  to  be  accumulated  in 
the  cavity  of  the  stomach  while  fasting;  and  is  seldom,  if  ever,  discharged 
from  its  proper  secerning  vessels,  except  when  excited  by  the  natural  stimulus 
of  aliment,  mechanical  irritation  of  tubes,  or  other  excitants.  When  aliment 
is  received,  the  juice  is  given  out  in  exact  proportion  to  its  requirements  for 
solution,  except  when  more  food  has  been  taken  than  is  necessary  for  the 
wants  of  the  system."  That  the  quantity  of  the  Gastric  Juice  secreted  from 

*  See  the  case  of  Alexis  St.  Martin,  with  the  observations  and  experiments  of  Dr.  Beau- 
mont, republished  in  this  country  by  Dr.  A.  Combe.  [A  very  extended  examination  of  the 
phenomena  of  gastric  digestion  has  been  made  by  M.  Blondlot.  The  chief  subject  of  ex- 
periment was  a  dog,  in  which  he  maintained,  without  affecting  the  health,  a  fistulous  opening 
into  the  stomach  for  more  than  two  years.  His  examinations  have  furnished  many  new 
and  important  facts,  and  have  confirmed  those  of  Dr.  Beaumont  made  on  Alexis  St.  Martin 
in  nearly  every  point. — Traite  Analytique  de  la  Digestion,  Paris,  1844. — M.  C.] 


ACTION  OF  THE  £TOMACH.  497 

the  walls  of  the  stomach  depends  rather  upon  the  general  requirements  of  the 
system,  than  upon  the  quantity  of  food  introduced  into  the  digestive  cavity,  is 
a  principle  of  the  highest  practical  importance,  and  cannot  be  too  steadily  kept 
in  view  in  Dietetics.  A  definite  proportion  only  of  aliment  can  be  perfectly 
digested  in  a  given  quantity  of  the  fluid;  the  action  of  which,  like  that  of 
other  chemical  operations,  ceases  after  having  been  exercised  on  a  fixed  and 
definite  amount  of  matter.  "  When  the  juice  has  become  saturated,  it  refuses 
to  dissolve  more ;  and,  if  an  excess  of  food  has  been  taken,  the  residue  remains 
in  the  stomach,  or  passes  into  the  bowels  in  a  crude  state,  and  becomes  n. 
source  of  nervous  irritation,  pain,  and  disease,  for  a  long  time."  The  unfa- 
vourable effect  of  an  undue  burthen  of  food  upon  the  stomach  itself,  interferes 
with  its  healthy  action ;  and  thus  the  quantity  really  appropriate  is  not  dis- 
solved. The  febrile  disturbance  is  thus  increased;  and  the  mucous  membrane 
of  the  stomach  exhibits  evident  indications  of  its  morbid  condition.  The  de- 
scription of  these  indications,  given  by  Dr.  Beaumont,  is  peculiarly  graphic, 
as  well  as  Hygienically  important. 

658.  "In  disease,  or  partial  derangement  of  the  healthy  function,  the  mu- 
cous membrane  presents  various  and  essentially-different  appearances.  In 
febrile  conditions  of  the  system,  occasioned  by  whatever  cause, — obstructed 
perspiration,  undue  excitement  by  stimulating  liquors,  overloading  the  sto- 
mach with  food;  fear,  anger,  or  whatever  depresses  or  disturbs  the  nervous 
system, — the  villous  coat  becomes  sometimes  red  and  dry,  at  other  times  pale 
and  moist,  and  loses  its  smooth  and  healthy  appearance ;  the  secretions  be- 
come vitiated,  greatly  diminished,  or  even  suppressed ;  the  coat  of  mucus 
scarcely  perceptible,  the  follicles  flat  and  flaccid,  with  secretions  insufficient 
to  prevent  the  papillae  from  irritation.  There  are  sometimes  found,  on  the 
internal  coat  of  the  stomach,  eruptions  of  deep-red  pimples,  not  numerous, 
but  distributed  here  and  there  upon  the  villous  membrane,  rising  above  the 
surface  of  the  mucous  coat.  These  are  at  first  sharp-pointed,  and  red,  but 
frequently  become  filled  with  white  purulent  matter.  At  other  times,  irre- 
gular, circumscribed  red  patches,  varying  in  size  and  extent  from  half  an  inch 
to  an  inch  and  a  half  in  circumference,  are  found  on  the  internal  coat. 
These  appear  to  be  the  effects  of  congestion  in  the  minute  blood-vessels  of  the 
stomach.  There  are  also  seen  at  times  small  aphthous  crusts,  in  connection 
with  these  red  patches.  Abrasion  of  the  lining  membrane,  like  the  rolling  up 
of  the  mucous  coat  into  small  shreds  or  strings,  leaving  the  papillae  bare  for 
an  indefinite  space,  is  not  an  uncommon  appearance.  These  diseased  appear- 
ances, when  very  slight,  do  not  always  affect  essentially  the  gastric  apparatus. 
When  considerable,  and  particularly  when  there  are  corresponding  symptoms 
of  disease, — as  dryness  of  the  mouth,  thirst,  accelerated  pulse,  &c. — no  gas- 
tric juice  can  be  extracted  by  the  alimentary  stimulus.  Drinks  are  imme- 
diately absorbed  or  otherwise  disposed  of;  but  food  taken  in  this  condition  of 
the  stomach  remains  undigested  for  twenty-four  or  forty-eight  hours,  or  more, 
increasing  the  derangement  of  the  alimentary  canal,  and  aggravating  the  gene- 
ral symptoms  of  disease.  After  excessive  eating  or  drinking,  chymification  is 
retarded ;  and,  though  the  appetite  be  not  always  impaired  at  first,  the  fluids 
become  acrid  and  sharp,  excoriating  the  edges  of  the  aperture,  and  almost 
invariably  producing  aphthous  patches  and  the  other  indications  of  a  diseased 
state  of  the  internal  membrane.  Vitiated  bile  is  also  found  in  the  stomach 
under  these  circumstances,  and  flocculi  of  mucus  are  more  abundant  than  in 
health.  Whenever  this  morbid  condition  of  the  stomach  occurs,  with  the 
usual  accompanying  symptoms  of  disease,  there  is  generally  a  corresponding 
appearance  of  the  tongue.  When  a  healthy  state  of  the  stomach  is  restored, 
the  tongue  invariably  becomes  clean." 

42* 


498  OF  FOOD,  AND  THE  DIGESTIVE  PROCESS. 

a.  Dr.  A.  Combe's  commentary  on  the  above  passage  is  too  apposite  to  be  omitted. 
"  Many  persons  who  obviously  live  too  freely,  protest  against  the  fact,  because  they  feel  no 
immediate  inconvenience,  either  from  the  quantity  of  food,  or  the  stimulants  in  which  they 
habitually  indulge ;  or,  in  other  words,  because  they  experience  no  pain,  sickness,  or  head- 
ache^— nothing,  perhaps,  except  slight  fulness  and  oppression,  which  soon  go  off.     Observa- 
tion extended  over  a  sufficient  length  of  time,  however,  shows  that  the  conclusion  drawn  is 
entirely  fallacious,  and  that  the  real  amount  of  injury  is  not  felt  at  the  moment,  merely  be- 
cause, for  a  wise  purpose,  nature  has  deprived  us  of  any  consciousness  of  either  the  exist- 
ence or  the  state  of  the  stomach  during  health.     In  accordance  with  this,  Dr.  Beaumont's 
experiments  prove,  that  extensive  erythematic  inflammation  of  the  mucous  coat  of  the  sto- 
mach was  of  frequent  occurrence  in  St.  Martin  after  excesses  in  eating,  and  especially  in 
drinking,  even  when  no  marked  general  symptom  was  present  to  indicate  its  existence. 
Occasionally,  febrile  heat,  nausea,  headache,  and  thirst  were  complained  of,  but  not  always. 
Had  St.  Martin's  stomach,  and  its  inflamed  patches,  not  been  visible  to  the  eye,  he  too  might 
have  been  pleased  that  his  temporary  excesses  did  him  no  harm;  but,  when  they  presented 
themselves  in  such  legible  characters,  that  Dr.  Beaumont  could  not  miss  seeing  them,  argu- 
ment and  supposition  were  at  an  end,  and  the  broad  fact  could  not  be  denied." 

b.  The  observations  of  Dr.  Beaumont  have  been  confirmed  by  those  of  M.  Blondlot  (Traite 
Analytique  de  la  Digestion),  and  of  M.  Ch.  Bernard  (Archiv.  d'Anat.  Gen.  et  de  Physiol., 
Jan.  1846);  which  were  made  upon  Dogs,  in  whose  stomachs  fistulous  openings  were  main- 
tained for  a  length  of  time. — They  found  that,  although  a  slight  mechanical  irritation,  applied 
directly  to  the  mucous  surface  of  the  stomach,  excites  at  once  an  abundant  flow  of  gastric 
fluid,  yet  if  this  irritation  be  carried  beyond  certain  limits,  so  as  to  produce  pain,  the  secre- 
tion, instead  of  being  more  abundant,  diminishes  or  ceases  entirely;  whilst  a  ropy  mucus  is 
poured  out  instead,  and  the  movements  of  the  stomach  are  considerably  increased.     The 
animal  at  the  same  time  appears  ill  at  ease,  is  agitated,  has  nausea,  and,  if  the  irritation  be 
continued,  actual  vomiting;  and  bile  has  been  observed  to  flow  into  the  stomach,  and  es- 
cape by  the  fistulous  opening.     Similar  disorders  of  the  functions  of  the  stomach  result  from 
violent  pain  in  other  parts  of  the  body ;  the  process  of  digestion  in  such  cases  being  sus- 
pended, and  sometimes  vomiting  excited.     When  accidulated  substances,  as  food  rendered 
acid  by  the  addition  of  a  little  vinegar,  were  introduced  into  the  stomach,  the  quantity  of 
gastric  fluid  poured  out  was  much  smaller,  and  the  digestive  process  consequently  slower, 
than  when  similar  food,  rendered  alkaline  by  a  weak  solution  of  carbonate  of  soda,  was  in- 
troduced.    If,  however,  instead  of  a  weak  solution,  carbonate  of  soda,  in  crystal  or  in  pow- 
der, was  introduced  into  the  stomach,  a  large  quantity  of  mucus  and  bile,  instead  of  gastric 
fluid,  flowed  into  the  stomach  ;  and  vomiting  and  purging  very  often  followed.     When  very 
cold  water,  or  small  pieces  of  ice,  were  introduced  into  the  stomach,  the  mucous  membrane 
was  at  first  rendered  very  pallid ;  but  soon  a  kind  of  reaction  followed,  the  membrane  be- 
came turgid  with  blood,  and  a  large  quantity  of  gastric  fluid  was  secreted.     If,  however,  too 
much  ice  was  employed,  the  animal  appeared  ill,  and  shivered ;  and  digestion,  instead  of 
being  rendered  more  active,  was  retarded.     Moderate  heat,  applied  to  the  mucous  surface  of 
the  stomach,  appeared  to  have  no  particular  action  on  digestion;  but  a  high  degree  of  heat 
produced  most  serious  consequences.     Thus,  the  introduction  of  a  little  boiling  water  threw 
the  animal  at  once  into  a  kind  of  adynamic  state,  which  was  followed  by  death  in  three  or 
four  hours ;  the  mucous  membrane  of  the  stomach  was  found  red  and  swollen,  whilst  an 
abundant  exudation  of  blackish  blood  had  taken  place  into  the  cavity  of  the  organ.     Similar 
injurious  effects  resulted  in  a  greater  or  less  degree,  from  the  introduction  of  other  irritants, 
such  as  nitrate  of  silver  or  ammonia ;  the  digestive  functions  being  at  once  abolished,  and 
the  mucous  surface  of  the  organ  rendered  highly  sensitive. 

659.  The  food  which  is  propelled  along  the  resophagus,  enters  the  Stomach 
through  its  cardiac  orifice,  in  successive  waves ;  and  it  is  immediately  sub- 
jected to  a  peculiar  peristaltic  movement,  which  has  for  its  object  to  produce 
the  thorough  intermixture  of  the  gastric  fluid  with  the  alimentary  mass,  and 
also  to  aid  the  solution  of  the  latter  by  the  gentle  trituration  to  which  it  is  thus 
subjected.  The  fasciculi  composing  the  muscular  wall  of  the  human  stomach, 
are  so  disposed  as  to  shorten  its  diameter  in  every  direction  ;  and  by  the  al- 
ternate contraction  and  relaxation  of  these  bands,  a  great  variety  of  motion  is 
induced  in  this  organ,  sometimes  transversely,  and  at  other  times  longitudi- 
nally. "  These  motions,"  Dr.  Beaumont  remarks,  "  not  only  produce  a  con- 
stant disturbance  or  churning  of  the  contents  of  the  stomach,  but  they  compel 
them,  at  the  same  time,  to  revolve  about  the  interior  from  point  to  point,  and 
from  one  extremity  to  the  other."  In  addition  to  these  movements,  there  is 


ACTION  OF  THE  STOMACH. 


499 


A  front  view  of  the  Stomach,  distended  by  flatus,  with  the  Peritoneal  Coat  turned  off;  1,  anterior  face 
of  the  cesophagus  ;  2,  the  cul-de-sac,  or  greater  extremity  ;  3,  the  lesser  or  pyloric  extremity  ;  4,  the  duo- 
denum ;  5,  5,  a  portion  of  the  peritoneal  coat  turned  back  ;  6,  a  portion  of  the  longitudinal  fibres  of  the 
muscular  coat ;  7,  the  circular  fibres  of  the  muscular  coat;  8,  the  oblique  muscular  fibres,  or  muscle  of 
Gavard ;  9.  a  portion  of  the  muscular  coat  of  the  duodenum,  where  its  peritoneal  coat  has  been  removed.] 


A  view  of  the  interior  of  the  Stomach,  as  given  by  the  removal  of  its  anterior  parietes  ;  1,  oesophagus ; 
2,  cardiac  orifice  of  the  stomach ;  3,  its  greater  extremity,  or  cul-de-sac ;  4,  the  greater  curvature ,  5,  line 
of  the  attachment  of  the  omentum  majus;  6,  the  muscular  coat ;  7,  the  anterior  cut  edge  of  the  mucous 
coat ;  8,  the  rugae  of  the  mucous  coat;  9,  the  lesser  curvature  ;  10,  the  beginning  of  the  duodenum  ;  11, 
pyloric  orifice,  or  valve  ;  12,  the  first  turn  of  the  duodenum  downwards.] 

a  constant  agitation  of  the  stomach,  produced  by  the  respiratory  muscles. 
The  motions  of  the  stomach  itself  are  not  performed  on  any  very  exact  plan, 
and  are  much  influenced  by  the  character  of  the  ingesta,  the  state  of  the 
general  system,  and  by  other  circumstances.  The  following  is  the  ordinary 
course,  however,  of  the  revolutions  of  the  food.  "  After  passing  the  oesopha- 
geal  ring,  it  moves  from  right  to  left,  along  the  small  arch  ;  thence,  through  the 
large  curvature,  from  left  to  right.  The  bolus,  as  it  enters  the  cardia,  turns  to 
the  left,  passes  the  aperture,*  descends  into  the  splenic  extremity,  and  follows 
the  great  curvature  towards  the  pyloric  end.  It  then  returns,  in  the  course  of 
the  smaller  curvature,  makes  its  appearance  again  at  the  aperture  in  its  descent 

*  The  fistulous  orifice  in  St.  Martin's  stomach,  through  which  these  observations  were 
made. 


500  OF  FOOD,  AND  THE  DIGESTIVE  PROCESS. 

[Fig.  203. 


A  view  of  the  interior  of  the  Stomach  and  Duodenum  in  situ,  the  inferior  portion  of  each  having  been 
removed;  1, 1,  the  under  side  of  the  liver;  2,  the  gall  bladder;  3,  3,  the  lesser  curvature  and  anterior 
faces,  as  seen  from  below  ;  4,  the  rugae,  about  the  cardiac  orifice;  5,  the  pyloric  orifice ;  6,  the  rugae,  and 
thickness  of  this  orifice  ;  7,  7,  the  duodenum ;  8,  lower  end  of  the  right  kidney.] 

into  the  great  curvature,  to  perform  similar  revolutions.  These  revolutions 
are  completed  in  from  one  to  three  minutes.  They  are  probably  induced  in 
a  great  measure,  by  the  circular  or  transverse  muscles  of  the  stomach.  They 
are  slower  at  first,  than  after  chymification  has  considerably  advanced ;"  at 
which  time  also  there  is  an  increased  impulse  towards  the  pylorus.  It  is 
probable  that,  from  the  very  commencement  of  chymification,  until  the  organ 
becomes  empty,  portions  of  chyme  are  continually  passing  into  the  duode- 
num ;  for  the  bulk  of  the  alimentary  mass  progressively  diminishes,  and  this 
the  more  rapidly  as  the  process  is  nearer  its  completion.  The  accelerated 
expulsion  appears  to  be  effected  by  a  peculiar  action  of  the  transverse  mus- 
cles ;  and  especially  of  that  portion  of  them  which  surrounds  the  stomach  at 
about  four  inches  from  its  pyloric  extremity.  This  band  is  so  forcibly  con- 
tracted in  the  latter  part  of  the  digestive  process,  that  it  almost  separates  the 
two  portions  of  the  stomach,  into  a  sort  of  hour-glass  form  ;  and  Dr.  B.  states 
that,  when  he  attempted  to  introduce  a  long  thermometer  tube  into  the  pyloric 
portion  of  the  stomach,  the  bulb  was  at  first  gently  resisted,  then  allowed  to 
pass,  and  then  grasped  by  the  rriuscular  parietes  beyond,  so  as  to  be  drawn 
in :  whence  it  is  evident  that  the  contraction  has  for  its  object,  to  resist  the 
passage  of  solid  bodies  into  the  pyloric  extremity  of  the  stomach,  at  this  stage 
of  digestion  ;  whilst  the  matter  which  has  been  reduced  to  the  fluid  form  is 
pumped  away  (as  it  were)  by  the  action  of  that  portion  of  the  viscus.  These 
peculiar  motions  continue,  until  the  stomach  is  perfectly  empty,  and  not  a  par- 
ticle of  food  or  chyme  remains.  Of  the  degree  in  which  they  are  dependent 
upon  the  influence  of  the  Nervous  System,  some  idea  has  been  already  given 
(§  387) ;  there  is  yet  much  to  be  learned,  however,  especially  in  regard  to  the 
degree  in  which  the  movements  may  be  checked  or  altered,  by  impressions 
transmitted  through  the  nervous  system.  It  is  stated  by  Brachetthat,  in  some 
of  his  experiments  upon  the  Par  Vagum  some  hours  after  section  of  the  nerve 
on  both  sides,  the  surface  only  of  the  alimentary  mass  was  found  to  have  un- 
dergone solution,  the  remainder  of  the  mass  remaining  in  the  condition  in 
which  it  was  at  first  ingested  ;  and  if  this  statement  can  be  relied  on,  it  would 
appear  that  the  movements  of  the  stomach,  like  those  of  the  heart,  can  be 
readily  affected  by  a  strong  nervous  impression.  It  may  be  partly  in  this 
manner,  therefore,  and  not  by  acting  upon  the  secretions  alone,  that  strong 
Emotions  influence  the  digestive  process,  as  they  are  well  known  to  do.  On 
the  other  hand,  the  moderate  excitement  of  pleasurable  emotions  may  be  fa- 


ACTION  OF  THE  INTESTINAL  TUBE.  501 

vourable  to  the  operation ;  not  only  by  giving  firmness  and  regularity  to  the 
action  of  the  heart,  and  thence  promoting  the  circulation  of  the  blood,  and  the 
increase  of  the  gastric  secretion  ;  but  also  in  imparting  firmness  and  regularity 
to  the  muscular  contractions  of  the  stomach. 

660.  Action  of  the  Intestinal  Tube. — The  pulpy  substance  to  which  the 
aliment  is  reduced,  by  the  mechanical  reduction  and  chemical  solution  it  has 
undergone  in  the  mouth  and  stomach,  is  termed  chyme.     The  consistence  of 
this  will  of  course  vary  in  some  degree  with   the  quantity  of  fluid  ingested ; 
in  general  it  is  greyish,  semifluid,  and  homogeneous  ;  and  possesses  a  slightly 
acid  taste,  but  is  otherwise  insipid.     Dr.  Beaumont  describes  it  as  varying  in 
its  aspect, — from  that  of  cream,  which  it  presents  when  the  food  has  been  of 
a  rich  character, — to  that  of  gruel,  which  it  possesses  when  the  diet  has  been 
farinaceous.     The  passage  of  the  chyme  through  the  pyloric  orifice  is  at  first 
slow ;  but  when  the  digestive  process  is  nearly  completed,  it  is  transmitted  in 
much  larger  quantities.     From  the  time  that  the  ingested   matter  enters  the 
intestinal  canal,  it  is  propelled  by  the  simple  peristaltic  action  of  its  muscular 
coat,  which  is  directly  excited  by  the  contact  either  of  this  matter,  or  of  the 
secretions  which  are  mingled  with  it  ;*  and   all  that  is  not  absorbed  is  thus 
conducted  to  the  rectum,  its  expulsion  from  which  is  due   to  an  action  of  a 
distinctly  reflex  kind,  excited  through  the  nervous  centres  (§  391).     During 
its  progress  through  the   intestinal  tube,  the  product  of  the  gastric   operation 
undergoes  very  important  changes.     The  chyme  is  mingled  in  the  duodenum 
with  the  biliary  and   pancreatic  secretions,  which  effect  an  immediate  altera- 
tion both  in  its  sensible  and  chemical  properties.     The  nature  of  this  altera- 
tion can  be  best  estimated,  by  mingling  bile  with  chyme  removed  from  the 
body.     This  has  been  done  by  several  experimenters  on  the  lower  animals ; 
and  by  Dr.  Beaumont  in  the  case  already  referred  to,  which  afforded  him  the 
means  of  obtaining  not  only  chyme,  but  bile  and  pancreatic  fluid.     The  effect 
of  this  admixture  was  to  separate  the  chyme  into  three  distinct  parts, — a  red- 
dish brown  sediment  at  the  bottom, — a  whey-coloured  fluid  in  the  centre, — 
and  a  creamy  pellicle  at  the  top.     The  central  portion,  with  the  creamy  pelli- 
cle, seems  to  constitute  the  chyle  absorbed  by  the  lacteals  ;  the  creamy  matter 
being  chiefly  composed  of  oily  particles ;  and  the  wheyey  fluid  having  pro- 
teine-compounds,  saccharine  and  saline   matters,  in   solution :  the   sediment, 
partly  consisting  of  the  insoluble  portion  of  the  food,  and  partly  of  the  biliary 
matter  itself,  is  evidently  excrementitious.     It  is  not  until  the  food  has  passed 
the  orifice  of  the  Ductus  Choledochus,  that  the  absorption  of  chyle  begins, — 
the  lacteals  not  being  distributed  upon  the  Stomach,  or  the  higher  part  of  the 
Duodenum. 

661.  By4he  gradual  withdrawal  of  their  fluid  portion,  the  contents  of  the 
alimentary  canal  are  converted  into  a  mass  of  greater  consistence ;  and  this, 
as  it  advances  through  the  small  intestines,  assumes  more  and  more  of  a  faecal 
character.     A  part  of  the  faeces,  however,  may  be  derived  from  the  secretions 
of  the  enteritic  mucous  membrane,  and  of  its  glandulae  ;  the  surface  of  the  for- 
mer, with  its  simple  follicles,  probably  secretes  nothing  else  than  mucus ;  but 
the  glandulsSj  with  which  it  is  so  thickly  studded,  appear  to  serve  as  the 
channel  for  the  elimination  of  putrescent  matter  from  the  blood.     There  can 
be  no  doubt,  that  a  large  quantity  of  fluid  is  poured  out  by  these  glandulae, 
when  they  are  in  a  state  of  irritation  from  disease,  or  from  the  stimulus  of  a 
purgative  medicine;  since  the  amount  of  water  discharged  from  the  bowels  is 

*  The  bile  seems  to  have  an  important  share  in  producing  this  effect;  since,  when  the 
ductus  choledochus  is  tied,  constipation  always  occurs.  The  action  of  mercury  as  a  purgative 
appears  to  take  place  through  the  increase  of  the  hepatic  and  other  secretions  which  it  in- 
duces. 


502  OF  FOOD,  AND  THE  DIGESTIVE  PROCESS. 

often  much  greater  than  that  which  has  heen  ingested,  and  must  be  derived 
from  the  blood. — The  secretion  of  the  caecum  has  been  ascertained  to  be,  in 
herbivorous  animals,  distinctly  acid  during  digestion ;  and  there  is  reason  to 
believe,  that  the  food  there  undergoes  a  second  process,  analogous  to  that  to 
which  it  has  been  submitted  in  the  stomach,  and  fitted  to  extract  from  it  what- 
ever undissolved  alimentary  matter  it  may  still  contain.  There  is  no  evi- 
dence, however,  that  this  is  the  case  in  Man,  whose  co3cum  (commonly  termed 
the  appendix  coeci  vermiformis)  is  very  small,  compared  to  that  of  most  her- 
bivorous animals. 

662.  The  act  of  Defecation  having  been  already  sufficiently  considered 
(§  391),  it  only  remains  to  notice  the  composition  of  the  Faeces.  These  are 
made  up  of  certain  parts  of  the  food,  which  have  not  been  reduced  and  ab- 
sorbed ;  together  with  that  portion  of  the  secretions  poured  into  the  aliment- 
ary canal  between  the  mouth  and  the  anus,  which  has  not  been  taken  back 
again  into  the  system.  Of  the  former  portion,  the  constituents  may  be  in 
great  part  determined  by  the  Microscope.  Thus  the  cell-walls  of  the  Vegeta- 
ble tissues  whose  contents  have  be.en  extracted,  the  entire  woody  fibres  (on 
which  the  digestive  process  has  no  influence),  the  granules  of  starch,  when 
they  have  undergone  no  preparation  before  being  swallowed, — portions  of 
tendon,  ligament,  adipose  tissue,  and  even  of  muscular  fibre, — with  other 
substances  constituting  the  undigested  residue  of  the  food,  may  be  readily 
detected.  Besides  these,  the  microscope  enables  us  to  recognize  the  brown 
colouring-matter  of  the  bile,  epithelium-cells  and  mucus-corpuscles,  and  various 
saline  particles,  especially  those  of  the  ammoniaco-magnesian  phosphate,  whose 
crystals  are  well-defined ;  most  of  which  .are  derived  from  the  secretions. — 
The  following  is  the  result  of  the  proximate  analysis  of  the  faeces  of  an  in- 
dividual in  good  health,  who  had  taken  the  ordinary  diet  of  this  country,  as 
given  by  Dr.  Percy  : — 

Substances  soluble  in  ether  (brownish  yellow  fat)  .  .  .       11-95 

"  alcohol  of  -830  .  .  .  .  .       10-74 

"  "  water  (brown  resinoid  matter)         .  .  .       31-61     ' 

Organic  matter  insoluble  in  the  above  menstrua     ....       49  33 

Salts  soluble  in  water          .  .  .  .  .  .  4-76 

Salts  insoluble  in  water    .,  .  .  .  .  .  .11*61 

Ultimate  analysis  of  the  same  faeces  gave  the  following  as  the  proportion  of 
the  components  of  the  Organic  constituents ;  Carbon  46*20,  Hydrogen  6*72, 
Nitrogen  and  Oxygen  30*71. — The  mineral  ash  of  faecal  matter  has  been  ex- 
amined by  Enderlin  ;  who  has  given  the  following  as  the  proportion  of  its 
ingredients : — 


Chloride  of  sodium  and  alkaline  sulphates  .  1*3677 

Bibasic  phosphate  of  soda                .              .  .  2-633  5 

Phosphates  of  lime  and  magnesia               .  .  80-372  "j 

Phosphate  of  iron  ....  .  2-090  i 


Sulphate  of  lime 
Silica 


4-530  f 
7-940  J 


Soluble  in  water. 


Insoluble  in  water. 


It  further  appears  from  the  inquiries  of  Enderlin,  that  a  portion  of  the  or- 
ganic matter  taken  up  by  alcohol,  sometimes  (but  not  constantly)  consists  of 
Choleate  of  soda,  the  characteristic  ingredient  of  bile  ;  and  he  thinks  that  this 
is  more  likely  to  be  present,  when  the  faeces  have  remained  for  only  a  short 
period  in  the  large  intestine,  and  when  there  has  been  less  time  for  its  re- 
absorption. — In  the  faecal  discharges  which  result  from  the  action  of  mercu- 
rials, large  quantities  of  biliary  matter  may  be  detected,  very  little  changed. 


NATURE  OF  CHYMIFICATION.  503 


4.  Nature  of  Chymification  and  Chylificdtion. 

663.  The  causes  of  the  reduction  of  the  food  in  the  Stomach,  have  long 
been  a  fruitful  source  of  discussion  amongst  physiologists  ;  and  various  hy- 
potheses have  been  devised  to  account  for  it.     Some  have  compared  the  Sto- 
mach of  Man  to  the  Gizzard  of  a  fowl,  and  have  supposed  that  the  trituration 
of  the  food  between  its  walls  was  the  essential  element  in  the  process  ;  but 
this  doctrine  is  completely  incompatible  with  the  fact,  that  digestible  substances, 
inclosed  in  metallic  balls  with  perforations  in  their  sides,  are  still  dissolved  by 
the  power  of  the  gastric  fluid,  though  the  walls  of  the  stomach  do  not  come 
in  contact  with  them.     Others,  again,  have   imagined  that  the  process  of  di- 
gestion is  one  of  putrefaction;  but  this   idea,  putting  aside  its   inherent  ab- 
surdity, is  proved  to  be  incorrect  by  the  fact  that  the  gastric  juice  has  a  de- 
cidedly antiseptic  quality.     Others,  in  despair  of  obtaining  any  other  solution, 
have  attributed  the  operation  to  the  direct  agency^of  the  vital  principle  ;  for- 
getting that,  as  long  as  the  aliment  remains  within  the  stomach  and  intestinal 
canal,  it  can  no  more  be  the  subject  of  any  peculiarly  vital  process,  than  if  it 
were  in  contact  with  the  skin,  of  which  the  mucous  membranels  but  an  inter- 
nal reflexion.     The  theory  of  chemical  solution,  which  was  at  first  regarded 
by  many  as  quite  untenable,  has  been  of  late  years  so  much  strengthened  by 
new  facts  arid  arguments,  that  there  now  appears  no  valid  reason   for  with- 
holding our  assent  from  it;  even  though  it  cannot  yet  give  a  complete  expla- 
nation of  the  complex  phenomena  in  question.     The  chief  opposition  to  this 
theory  has  arisen  from  the  difficulty  of  imagining,  that  any  simply-chemical 
solvent  should  have  the  power  of  acting  on  so  great  a  variety  of  substances, 
and  of  reducing  them  to  a  state  so  homogeneous.     This  difficulty,  however, 
seems  now  in  a  great  degree  removed,  by  the  discovery  of  the  close  Chemical 
relation  that  subsists,  between  the  various  substances  of  each  of  the  groups 
already  enumerated  (§  639)  ;   which   renders    it  easy    to   conceive,  that  the 
changes  involved  in  their  reduction  may  be  of  a  very  simple  character. 

664.  The  first  series  offsets  which  will  be  here  adduced,  as  throwing  light 
on  the  process  of  Chymification,  is  that  which  has  been  obtained  by  the  ex- 
periments of  Dr.  Beaumont  upon  the  individual  already  alluded  to  (§  658.) 
By  introducing  a  tube  of  India-rubber  into  the  empty  stomach,  he  was  able 
to  obtain  a  supply  of  Gastric   Juice  whenever  he  desired  it ;  for  the  tube 
served  the  purpose  of  stimulating  the   follicles  to  pour  forth   their  secretion, 
and  at  the  same  time  conveyed  it  away.     This  fluid,  of  which  the  existence 
has  been  denied  by  some  physiologists,  is  not  very  unlike  saliva  in  its  appear- 
ance ;  it  is,  however,  distinctly  acid  to  the  taste  ;  and  chemical  analysis  shows 
that  it  contains  a  considerable  proportion  of  free  muriatic  acid,  and  also  some 
acetic  acid.     The  former  must  evidently  be  derived  from  the  decomposition 
of  the  muriate  of  soda  contained  in  the  blood,  the  remote  source  of  which  is 
the  salt  ingested  with  the  food.     The  latter  is  an  organic  compound,  probably 
formed  at  the  expense  of  some  of  the  saccharine  matter  of  the  previous  ali- 
ment.    Of  equal  importance  with  the  free  acids,  is  an  animal  matter,  soluble 
in  cold  water,  but  insoluble  in  hot,  bearing  considerable  resemblance  to  albu- 
men.    Of  this  more  will  be  said  hereafter.     Besides  these  principal  ingre- 
dients, the  gastric  fluid  contains   muriates   and  phosphates  of  potass,  soda, 
magnesia,  and  lime.     It  possesses  the   power  of  coagulating  albumen  in  an 
eminent  degree  ;  it  is  powerfully  antiseptic,  checking  the  putrefaction  of  meat ; 
and  it  is   effectually  restorative  of  healthy  action,  when  applied  to  old  fetid 
sores  and  foul  ulcerating  surfaces.     It  may  be  kept  for  many  months,  if  ex- 
cluded from  the  air  without  becoming  foetid. 

a.  The  Chemistry  of  the  Gastric  Juice  has  been  greatly  unsettled  by  the  results  of  recent 


504  OF  FOOD,  AND  THE  DIGESTIVE  PROCESS. 

inquiries;  which  seem  inconsistent  with  the  statement  just  given,  especially  in  regard  to  the 
presence  of  free  muriatic  acid.  It  may  be  well,  in  the  first  instance,  to  quote  Professor 
Dunglison's  account  of  the  analysis  of  the  gastric  fluid  drawn  from  the  stomach  of  Alexis 
St.  Martin,  and  supplied  to  him  by  Dr.  Beaumont.  "  The  quantity  of  free  hydrochloric  add 
was  surprising  ;  on  distilling  the  gastric  fluid,  the  acids  passed  over,  the  salts  and  animal  mat- 
ter remaining  in  the  retort ;  the  amount  of  chloride  of  silver  thrown  down,  on  the  addition 
of  nitrate  of  silver  to  the  distilled  fluid,  was  astonishing.  The  author  had  many  opportu- 
nities of  examining  the  gastric  secretion  obtained  from  the  case  in  question.  At  all  times, 
when  pure  or  unmixed,  except  with  a  portion  of  the  mucus  of  the  lining  membrane  of  the 
digestive  tube,  it  was  a  transparent  fluid,  having  a  marked  smell  of  hydrochloric  add ;  and  of 
a  slightly  salt,  and  very  perceptibly  acid,  taste."  (Human  Physiology,  Sixth  Edition,  Vol.  I., 
p.  546.) 

b.  From  the  experiments  of  MM.  Blondlot,  Bernard,  and  Barreswill,  and  Dr.  R.  D.  Thom- 
son, on  the  other  hand,  it  would  seem  that  no  free  hydrochloric  acid  is  present  in  the  gastric 
fluid;  since  the  fluid  which  comes  over,  on  distillation  at  a  low  temperature,  contains  none; 
whilst  the  matter  remaining  in  the  retort  becomes  more  and  more  acid  with  the  progress  of 
the  distillation,  and  may  be  subjected  to  a  high  temperature  (300°)  without  giving  off  acid 
fumes.  It  is  difficult  to  account  for  the  discrepancy  between  these  carefully  conducted  ex- 
periments, and  the  positive  statement  of  Professor  Dunglison.  otherwise  than  by  supposing 
that  the  Human  gastric  fluid  differs  from  that  of  the  Dog  and  the  Pig,  which  were  employed 
in  the  analyses  last  quoted. — The  acid  reaction  was  referred  by  Blondlot  to  the  presence  of 
super-phosphate  of  lime ;  but  this  seems  incorrect.  Professor  Thomson  agrees  with  MM. 
Bernard  and  Barreswill  in  attributing  it  chiefly  to  Lactic  acid  ;  which,  contrary  to  previous 
opinions,  they  regard  as  generally  if  not  universally  present  in  the  stomach  during  healthy 
digestion,  and  it  would  seem  that  this  acid  may  partially  decompose  the  phosphates  and 
muriates,  which  are  contained  in  the  secretion  :  and  may  thus  occasion  the  phosphoric  'and 
muriatic  acids  to  be  set  free.  The  presence  of  a  small  quantity  of  free  Acetic  acid,  also, 
seems  to  have  been  recognized  by  them. 

665.  The  Gastric  Juice  obtained  from  the  stomach,  was  found  by  Dr. 
Beaumont  to  possess  the  power  of  dissolving  various  kinds  of  alimentary  sub- 
stances, when  these  were  submitted  to  its  action  at  a  constant  temperature  of 
100°,  (which  is  about  that  of  the  stomach,)  and  were  frequently  agitated. 
The  solution  appeared  to  be  in  all  respects  as  perfect  as  that  which  naturally 
takes  place  in  the  stomach  ;  but  required  a  longer  time.  This  is  readily  ac- 
counted for  when  we  remember,  that  no  ordinary  agitation  can  produce  the 
same  effect  with  the  curious  movements  of  the  stomach  ;  and  that  the  conti- 
nual removal  from  its  cavity,  of  the  matter  which  has  been  already  dissolved, 
must  aid  the  operation  of  the  solvent  on  the  remainder.  The  following  is 
one  out  of  many  experiments  detailed  by  Dr.  Beaumont.  "At  ll£  o'clock, 
A.  M.,  after  having  kept  the  lad  fasting  for  17  hours,  I  introduced  a  gum-elastic 
tube,  and  drew  off  one  ounce  of  pure  gastric  liquor,  unmixed  with  any  other 
matter,  except  a  small  proportion  of  mucus,  into  a  three-ounce  vial.  I  then 
took  a  solid  piece  of  boiled  recently-salted  beef,  weighing  three  drachms,  and 
put  it  into  the  liquor  in  the  vial ;  corked  the  vial  tight,  and  placed  it  in  a 
saucepan  filled  with  water,  raised  to  the  temperature  of  100°,  and  kept  at  that 
point  on  a  nicely-regulated  sand-bath.  In  forty  minutes,  digestion  had  dis- 
tinctly commenced  over  the  surface  of  the  meat.  In  fifty  minutes,  the  fluid 
had  become  quite  opaque  and  cloudy ;  the  external  texture  began  to  separate 
and  become  loose.  In  sixty  minutes,  chyme  began  to  form.  At  1  o'clock, 
P.M.,  (digestion  having  progressed  with  the  same  regularity  as  in  the  last  half- 
hour),  the  cellular  texture  seemed  to  be  entirely  destroyed,  leaving  the  mus- 
cular fibres  loose  and  unconnected,  floating  about  in  fine  small  shreds,  very 
tender  and  soft.  At  3  o'clock,  the  muscular  fibres  had  diminished  one-half, 
since  the  last  examination.  At  5  o'clock,  they  were  nearly  all  digested  ;  a 
few  fibres  only  remaining.  At  7  o'clock,  the  muscular  texture  was  completely 
broken  down,  and  only  a  few  of  the  small  fibres  could  be  seen  floating  in  the 
fluid.  At  9  o'clock,  every  part  of  the  meat  was  completely  digested.  The 
gastric  juice,  when  taken  from  the  stomach,  was  as  clear  and  transparent  as 
water.  The  mixture  in  the  vial  was  now  about  the  colour  of  whey.  After 


NATURE   OF  CHYMIFICATION.  505 

standing  at  rest  a  few  minutes,  a  fine  sediment,  of  the  colour  of  the  meat,  sub- 
sided to  the  bottom  of  the  vial. — A  piece  of  beef,  exactly  similar  to  that  placed 
in  the  vial,  was  introduced  into  the  stomach,  through  the  aperture,  at  the  same 
time.  At  12  o'clock  it  was  withdrawn,  and  found  to  be  as  little  affected  by 
digestion  as  that  in  the  vial ;  there  was  little  or  no  difference  in  their  appear- 
ance. It  was  returned  to  the  stomach ;  and,  on  the  string  being  drawn  out  at 
1  o'clock  P.M.,  the  meat  was  found  to  be  all  completely  digested  and  gone. 
The  effect  of  the  gastric  juice  on  the  piece  of  meat  suspended  in  the  stomach, 
was  exactly  similar  to  ihat  in  the  vial,  only  more  rapid  after  the  first  half 
hour,  and  sooner  completed.  Digestion  commenced  on,  and  was  confined  to, 
the  surface  entirely  in  both  situations.  Agitation  accelerated  the  solution  in  the 
vial,  by  removing  the  coat  that  was  digested  on  the  surface,  enveloping  the 
remainder  of  the  meat  in  the  gastric  fluid,  and  giving  this  fluid  access  to  the 
undigested  portions."*  Many  variations  were  made  in  other  experiments  ; 
some  of  which  strikingly  displayed  the  effects  of  thorough  mastication,  in 
aiding  both  natural  and  artificial  digestion. 

666.  The  attempt  was  made  by  Dr.  Beaumont,  to  determine  the  relative 
digestibility  of  different  articles  of  diet,  by  observing  the  length  of  time  re- 
quisite for  their  solution.  But,  as  he  himself  points  out,  the  rapidity  of  diges- 
tion varies  so  greatly,  according  to  the  quantity  eaten,  the  nature  and  amount 
of  the  previous  exercise,  the  interval  since  the  preceding  meal,  the  state  of 
health,  the  condition  of  the  mind,  and  the  nature  of  the  weather,  that  a  much 
more  extended  inquiry  would  be  necessary  to  arrive  at  results  to  be  depended 
on.  Some  important  inferences  of  a  general  character,  however,  may  be 
drawn  from  his  inquiries. — It  seems  to  be  a  general  rule,  that  the  flesh  of 
wild  animals  is  more  easy  of  digestion  than  that  of  the  domesticated  races 
which  approach  them  most  nearly.  This  may,  perhaps,  be  partly  attributed 
to  the  small  quantity  of  fatty  matter  that  is  mixed  up  with  the  flesh  of  the 
former,  whilst  that  of  the  latter  is  largely  pervaded  by  it.  For  it  appears  from 
Dr.  B.'s  experiments,  that  the  presence  in  the  stomach  of  any  substance  which 
is  difficult  of  digestion,  interferes  with  the  solution  of  food  that  would  other- 
wise be  soon  reduced.  It  seems  that,  on  the  whole,  Beef  is  more  speedily 
reduced  than  Mutton,  and  Mutton  sooner  than  either  Veal  or  Pork.  Fowls 
are  far  from  possessing  the  digestibility  that  is  ordinarily  imputed  to  them  ; 
but  Turkey  is,  of  all  kinds  of  flesh  except  Venison,  £he  most  soluble.  Dr. 
B.'s  experiments  further  show,  that  bulk  is  as  necessary  for  healthy  digestion, 
as  the  presence  of  the  nutrient  principle  itself.  JMiis  fact  has  been  long  known 
by  experience  to  uncivilized  nations.  The  Kamschatdales,  for  example,  are 
in  the  habit  of  mixing  earth  or  saw-dust  with  the  train-oil,  on  which  alone 
they  are  frequently  reduced  to  live.  The  Veddahs  or  wild  hunters  of  Ceylon, 
on  the  same  principle,  mingled  the  pounded  fibres  of  soft  and  decayed  wood 
with  the  honey,  on  which  they  feed  when  meat  is  not  to  be  had  ;  and  on  one 
of  them  being  asked  the  reason  of  the  practice,  he  replied,  "  I  cannot  tell  you, 
but  I  know  that  the  belly  must  be  filled."  It  is  further  shown  by  Dr.  B., 
that  soups  and  fluid  diet  are  not  more  readily  chymified  than  solid  aliment, 
and  are  not  alone  fit  for  the  support  of  the  system  ;  and  this,  also,  is  conform- 
able to  the  well-known  results  of  experience  ;  fpr  a  dyspeptic  patient  will 
frequently  reject  chicken-broth,  when  he  can  retain  solid  food  or  a  richer 
soup.  Perhaps,  as  Dr.  A.  Combe  remarks,  the  little  support  gained  from 
fluid  diet,  is  due  to  the  rapid  absorption  of  the  watery  part  of  it ;  so  that  the 
really  nutritious  portion  is  left  in  too  soft  and  concentrated  a  state,  to  excite 
the  healthy  action  of  the  stomach. — Dr.  Beaumont  also  ascertained  that 
moderate  exercise  facilitates  digestion,  though  severe  and  fatiguing  exercise 

*  Experiments  2  and  3  of  First  Series. 
43 


506  OF  FOOD,  AND  THE  DIGESTIVE  PROCESS. 

retards  it.  If  even  moderate  exercise  be  taken  immediately  after  a  full  meal, 
however,  it  is  probably  rather  injurious  than  beneficial ;  but  if  an  hour  be  per- 
mitted to  elapse,  or  if  the  quantity  of  food  taken  have  been  small,  it  is  of  de- 
cided benefit.  The  influence  of  temperature  on  the  process  of  solution,  is 
remarkably  shown  in  some  of  Dr.  B.'s  experiments.  He  found  that  the  gas- 
tric juice  had  scarcely  any  influence  on  the  food  submitted  to  it,  when  the 
bottle  was  exposed  to  the  cold  air,  instead  of  being  kept  at  a  temperature  of 
100°.  He  observed  on  one  occasion,  that  the  injection  of  a  single  gill  of 
water  at  50°  into  the  stomach,  sufficed  to  lower  its  temperature  upwards  of 
30°  ;  and  that  its  natural  heat  was  not  restored  for  more  than  half  an  hour. 
Hence  the  practice  of  eating  ice  after  dinner,  or  even  of  drinking  largely  of 
cold  fluids,  is  very  prejudicial  to  digestion. 

667.  From  the  foregoing  statements  we  may  conclude,  that  the  process  by 
which  the  food  is  dissolved  in  the  Gastric  fluid  is  of  a  purely  Chemical  na- 
ture, since  it  takes  place  out  of  the  living  body  as  well  as  in  it, — allowance 
being  made  for  the  difference  in  its  physical  condifoon.  That  the  natural  pro- 
cess of  digestion  is  imitated,  when  the  food  is  submitted  to  the  action  of  the 
gastric  juice  in  a  vial,  not  only  in  regard  to  the  disintegration  of  its  particles, 
but  as  to  the  change  of  character  which  they  are  made  to  undergo,  is  proved 
by  the  fact,  that  the  artificial  chyme  thus  formed  exhibits  the  same  changes  as 
the  real  chyme,  when  submitted  to  the  action  of  the  bile  (§  658).  The  pro- 
cess of  digestion,  however,  may  be  freely  conceded  to  be  vital,  in  so  far  as  it 
is  dependent  upon  the  agency  of  a  secreted  product,  which  vitality  alone  (so 
far  at  least  as  we  at  present  know)  can  elaborate ;  and  all  for  which  it  is  here 
contended  is,  that,  when  this  product  is  once  formed,  it  has  an  agency  upon 
the  alimentary  matter,  which,  though  not  yet  fully  understood,  is  conformable, 
in  all  that  is  known  of  its  operation,  to  the  ordinary  laws  of  chemistry.  Thus, 
Digestion  is  conformable  to  Chemical  solution, — -first,  in  the  assistance  which 
both  derive  from  the  minute  division  of  the  solids  submitted  to  it ; — secondly, 
in  the  assistance  which  both  derive  from  the  successive  addition  of  small  por- 
tions of  the  comminuted  solid  to  the  solvent  fluid,  and  from  the  thorough  in- 
termixture of  the  two  by  continual  agitation ; — thirdly,  in  the  limitation  of  the 
quantity  of  food  on  whic'h  a  given  amount  of  gastric  juice  can  operate,  which 
is  precisely  the  case  with  chemical  solvents ;— -fourthly,  in  the  assistance  which 
both  derive  from  an  elevation  of  temperature, — the  beneficial  influence  of  heat 
being  only  limited,  in  the  case  of  digestion,  by  its  tendency  to  produce  decom- 
position of  the  gastric  fluid  ; — -fifthly,  in  the  different  action  of  the  same  solvent 
upon  the  various  solids  submitted  to  it. 

668.  It  may  be  considered  a  well-established  fact,  that  diluted  acids  alone 
have  no  power  of  chymifying  alimentary  substances,  although  capable  of 
partially  dissolving  some  of  them ;  but  that  their  presence  in  the  gastric  fluid 
is  essential  to  its  effectual  action.  The  active  agent  in  the  process  appears  to 
be  an  Organic  compound,  to  which  the  name  of  pepsin  has  been  given.  The 
properties  of  this  have  been  investigated  by  Wasmann,  who  first  succeeded  in 
obtaining  it  in  an  isolated  state ;  his  observations  were  made  upon  the  mucous 
membrane  of  the  stomach  of  the  Pig,  which  greatly  resembles  that  of  Man. 

a.  When  this  membrane  is  digested  in  a  large  quantity  of  water  at  from  85°  to  95°,  many 
other  matters  are  removed  from  it  besides  pepsin ;  but  if  this  water  be  removed,  and  the 
digestion  be  continued  with  fresh  water  in  the  cold,  very  little  but  pepsin  is  then  taken  up. 
Pepsin  appears  to  be  but  sparingly  soluble  in  water ;  when  its  solution  is  evaporated  to  dry- 
ness,  there  remains  a  brown,  grayish,  viscid  mass,  with  the  odour  of  glue,  and  having  the 
appearance  of  an  extract.  The  solution  of  this  in  water  is  turbid,  and  still  possesses  a  por- 
tion of  the  characteristic  power  of  pepsin,  but  greatly  reduced.  When  strong  alcohol  is  added 
to  a  fresh  solution  of  pepsin,  the  latter  is  precipitated  in  white  flocks,  which  may  be  collected 
on  a  filter,  and  produce  a  grey  compact  mass  when  dried.  Pepsin  enters  into  chemical  com- 


NATURE  OF  CHYMIFICATION PEPSIN.  507 

bination  with  many  acids,  forming  compounds  which  still  redden  litmus  paper ;  and  it  is 
when  thus  united  with  acetic  and  muriatic  acids,  that  its  solvent  powers  are  the  greatest. 

b.  "In  regard  to  the  solvent  power  of  pepsin  for  coagulated  albumen,  it  was  observed  by 
M.  Wasmann  that  a  liquid  which  contains  17-lO,OOOths  of  acetate  of  pepsia,  and  6  drops 
of  hydrochloric  acid  per  ounce,  possesses  a  very  sensible  solvent  power,  so  that  it  will  dis- 
solve a  thin  slice  of  coagulated  albumen  in  the  course  of  6  or  8  hours'  digestion.  With  12 
drops  of  hydrochloric  acid  per  ounce,  the  white  of  egg  is  dissolved  in  2  hours.  A  liquid 
which  contains  ^  gr.  of  acetate  of  pepsin,  and  to  which  hydrochloric  acid  and  white  of  egg 
are  alternately  added,  so  long  as  the  latter  dissolves,  is  capable  of  raking  up  210  grains  of 
coagulated  white  of  egg  at  a  temperature  between  95°  and  104°.  It  would  appear,  from 
such  experiments,  that  the  hydrochloric  acid  is  the  true  solvent,  and  that  the  action  of  the 
pepsin  is  limited  to  that  of  disposing  the  white  of  egg  to  dissolve  in  hydrochloric  acid.  The 
acid  when  alone  dissolves  white  of  egg  by  ebullition,  just  as  it  does  under  the  influence  of 
pepsin;  from  which  it  follows  that  pepsin  replaces  the  effect  of  a  high  temperature,  which 
is  not  possible  in  the  stomach.  The  same  acid  with  pepsin  dissolved  blood,  fibrine,  meat 
and  cheese;  while  the  isolated  acid  dissolved  only  an  insignificant  quantity  at  the  same 
temperature;  but  when  raised  to  the  boiling  point,  it  dissolved  nearly  as  much,  and  the  part 
dissolved  appeared  to  be  of  the  same  nature.  The  epidermis,  horn,  the  elastic  tissue  (such 
as  the  fibrous  membrane  of  arteries)  do  not  dissolve  in  a  dilute  acid  containing  pepsin.  M . 
Wasmann  has  remarked  that  the  pepsin  of  the  stomach  of  the  pig  is  entirely  destitute  of  the 
power  to  coagulate  milk,  although  the  pepsin  of  the  stomach  of  the  calf  possesses  it  in  a  very 
high  degree ;  from  which  he  is  led  to  suppose,  that  the  power  of  the  latter  depends  upon  a 
particular  modification  of  pepsin,  or  perhaps  upon  another  substance  accompanying  it,  which 
ceases  to  be  formed  when  the  young  animal  is  no  longer  nourished  by  the  milk  of  its  mother."* 

669.  It  is  considered  by  Liebig,  however,  that  Pepsin  has  no  proper  ex- 
istence as  such ;  and  that  it  is  nothing  else  than  a  proteine-compound  in  a 
state  of  change, — being,  when  obtained  after  the  method  of  Wasmann,  the 
result  of  the  partial  decomposition  of  the  membrane  of  the  stomach,  which 
has  been  induced  in  it  by  exposure  to  air.     This  view  accords  well  with  the 
fact,  recently  ascertained  by  MM.  Bernard  and  Barreswill,  that  the  Saliva  and 
Pancreatic  fluid  have  an  equal  solvent  power  when  acidulated.     In  their  alka- 
line condition,  their  action  appears  limited  to  starchy  matters  ;  of  which  they 
effect  the  conversion  into  sugar.     In  their  acid  state,  they  act,  like  the  gastric 
fluid,  upon  azotized  matters ;  and,  in  common  with  it,  they  are  destitute  of 
power  to  act  upon  starch. — We  are  further  led,  by  this  remarkable  fact  (the 
knowledge  of  which  enables  us  to  harmonize  many  previous  results,  which 
were  apparently  discordant),  to  a  better  understanding  of  the  nature  of  the 
action  of  this  Organic  compound  in  the  Digestive  process.     Its  operation  on 
starch  is  precisely  that  of  the  substance  termed  Diastase,  which  is  found  in 
Plants,  and  which  is   the  agent  employed  for  the  conversion  of  starch  into 
sugar,  in  various  processes  of  the  Vegetable  economy.     In  so  doing,  it  acts  as 
a  sort  of ferment ;  having  the  power  of  exciting  a  change  in  another  substance, 
in  which  it  does  not  itself  participate.     This  appears  to  be  precisely  the 
nature  of  its  operation  upon  azotized  matters  ;  in  which  it  produces  an  in- 
cipient change,  that  so  alters  their  condition,  as  to  dispose  them  to  solution  in 
hydrochloric  and  acetic  acids,  'with  which  they  form  definite  chemical  com- 
pounds.— The  analogy  of  the  action  of  Pepsin  to  that  of  a  ferment,  is  further 
shown  in  the  power  possessed  by  a  very  small  quantity  of  it,  to  excite  the 
required  change  in  an  almost  unlimited  amount  of  alimentary  matters ;  whilst 
only  a  definite  quantity  of  these  matters,  when  thus  prepared,  can  be  dissolved 
in  a  limited  amount  of  dilute  acid;  which  is  precisely  analogous  to  the  pro- 
cess of  chemical  solution.     The  agency  of  Pepsin,  in  preparing  them  for  that 
process,  resembles  that  of  Heat ;  by  which  it  may  be  replaced, — the  dilute 
acids  alone,  at  a  high  temperature,  having  the  power  of  dissolving  azotized 
compounds. 

670.  We  have,  in  the  last  place,  to  consider  the  changes  which  are  effected 

*  Graham's  Elements  of  Chemistry,  [Am.  ed.  p.  695.] 


508  OF  FOOD,  AND  THE  DIGESTIVE  PROCESS. 

in  the  nutritive  materials,  by  the  admixture  of  the  biliary  and  pancreatic  secre- 
tions ;  and  to  inquire  into  the  form  in  which  they  are  received  into  the  absorb- 
ent vessels. — The  substances  of  the  first  or  saccharine  group  consist  chiefly 
of  Sugar  and  Starch.  It  appears  from  the  late  researches  of  MM.  Bouchardat 
and  Sandras,  that  Sugar  is  gradually  converted,  during  its  passage  along  the 
alimentary  canal,  into  lactic  acid  ;  and  that  it  is  absorbed  in  this  form  alone, 
unless  it  have  been  administered  in  considerable  quantity  or  for  a  long  period. 
The  conversion  of  sugar  into  lactic  acid,  appears  to  be  preliminary  to  the 
elimination  of  that  substance  by  the  respiratory  process.  The  particles  of 
Starch,  as  already  mentioned,  are  but  very  little  acted  on  by  the  digestive  pro- 
cess, at  least  in  Man  and  the  Mammalia,  unless  their  envelopes  have  been 
previously  ruptured  by  heat  or  chemical  agents ;  but  the  triturating  power  of 
the  gizzard  in  granivorous  Birds,  aided  by  the  high  temperature  and  the  more 
alkaline  character  of  the  secretions,  enables  them  to  act  with  more  energy  upon 
amylaceous  substances.  The  products  of  the  digestive  action  upon  starch, 
are  dextrine  and  grape-sugar;  and  this  is  gradually  converted  into  lactic  acid, 
in  which  state  it  is  absorbed.  If  sugar  be  introduced  into  the  blood-vessels 
unchanged,  it  is  drawn  off  by  the  urine  ;  and  its  heat-sustaining  agency,  there- 
fore, is  not  exerted.  It  is  probably  to  avoid  its  too  rapid  introduction  that 
the  conversion  of  amylaceous  into  saccharine  matter  is  so  slowly  effected  in 
the  alimentary  canal ;  this  conversion  seems  to  begin  in  the  mouth,  to  cease 
in  the  stomach  during  the  operation  of  the  acid  solvent,  and  to  recommence 
after  the  neutralization  of  the  acid  by  the  biliary  and  pancreatic  fluids, — sub- 
sequently continuing  during  nearly  the  whole  of  the  passage  of  the  alimentary 
matter  along  the  intestinal  tube. — It  is  now  quite  certain,  that  the  substances 
of  this  class  may  be  converted,  in  the  living  body,  into  oleaginous  matter.  Of 
the  mode  and  the  situation  in  which  this  conversion  takes  place,  nothing 
whatever  is  certainly  known ;  but  a  clue  to  an  acquaintance  with  the  former 
seems  to  be  given  by  the  recently-discovered  fact,  that  the  continued  contact 
of  bile  with  saccharine  matter  occasions  the  conversion  of  a  portion  of  the 
sugar  into  an  adipose  compound  (§  835). 

671.  The  substances  forming  the  Oleaginous  class  do  not  seem  to  undergo 
any  change,  except  minute  division  of  their  particles,  until  the  Chyme  is  min- 
gled with  bile;  which  substance  acts  as  a  soap,  and  renders  the  oily  matters 
soluble,  or  at  any  rate  reduces  them  to  a  condition  in  which  they  can  be  ab- 
sorbed by  the  lacteals.  This,  indeed,  seems  to  be  the  main  purpose  of  that 
admixture  of  the  bile  with  the  mass  in  process  of  digestion,  which  experiments 
and  pathological  observation  abundantly  prove,  to  be  requisite  for  the  due  per- 
formance of  that  function.  Thus,  it  has  been  shown  by  the  experiments  of 
Schwann,  that,  if  the  bile-duct  be  divided,  and  be  made  to  discharge  its  con- 
tents externally  through  a  fistulous  orifice  in  the  walls  of  the  abdomen,  instead 
of  into  the  intestinal  canal,  those  animals  which  survive  the  immediate  effects 
of  the  operation,  subsequently  die  from  inanition,  almost  as  soon  as  if  they 
had  been  entirely  deprived  of  food.  In  like  manner,  if  the  flow  of  the  biliary 
secretion  into  the  intestine  be  prevented  by  disease, — such  as  obstruction  of 
the  gall-duct, — the  digestive  function  is  evidently  disordered,  the  peristaltic 
action  of  the  intestine  is  not  duly  performed,  the  faeces  are  white  and  clayey ; 
and  there  is  an  obvious  insufficiency  in  the  supply  of  nutriment  prepared  for 
the  absorbent  vessels.  This  deficiency  seems  partly  due  to  the  want  of  power 
to  absorb  the  oleaginous  particles  of  the  food,  which  is  the  result  of  the  non- 
intermixture  of  the  bile  with  the  chyme;  and  partly  to  the  suspension  of  the 
supply  of  combustible  matter,  that  is  afforded  by  certain  constituents  of  the 
bile  itself,  which  are  destined,  not  to  be  carried  out  of  the  system,  but  to  be 
re-absorbed. — The  presence  of  bile  in  the  stomach  has  the  effect  of  suspend- 


ABSORPTION  FROM  THE  DIGESTIVE  CAVITY.  509 

ing  the  solution  of  the  various  azotized  principles,  and  in  regard  to  them, 
therefore,  it  is  injurious;  but  it  seems,  from  the  observations  of  Dr.  Beaumont, 
to  be  a  spontaneous  occurrence,  whenever  the  diet  has  been  for  a  long  time, 
and  in  great  part,  of  an  oleaginous  nature ;  and  it  then  appears  destined  to  aid 
in  the  reducing  process,  which  is  the  proper  function  of  the  stomach.  It  is 
suggested  by  Dr.  A.  Combe,  whether  the  peculiar  digestibility  of  a  piece  of 
fat  bacon,  in  certain  forms  of  Dyspepsia,  may  not  be  due  to  the  abnormal 
presence  of  bile  in  the  stomach.  The  power  of  precipitating  the  proteine- 
compounds  from  their  acid  solutions,  which  has  been  shown,  by  the  recent 
experiments  of  Platner,  to  belong  to  the  peculiar  principles  of  bile,  fully  ex- 
plains its  injurious  effects  upon  the  solvent  processes,  which  normally  take 
place  in  the  stomach. — In  regard  to  the  Albuminous  and  Gelatinous  articles 
of  food,  there  is  no  evidence  that  any  other  change  is  effected  in  them,  than 
one  of  simple  solution  ;  and  they  appear  to  be  absorbed  in  the  same  condition 
as  that  to  which  they  are  reduced  by  the  action  of  the  stomach. 


CHAPTER    XI. 

OF    ABSORPTION    AND    SANGUIFICATION. 

1. — Absorption  from  the  Digestive  Cavity. 

672.  So  long  as  the  Alimentary  matter  is  contained  in  the  digestive  cavity, 
it  is  as  far  from  being  conducive  to  the  nutrition  of  the  system,  as  if  it  were  in 
contact  with  the  external  surface.  It  is  only  when  absorbed  into  the  vessels, 
and  carried  by  the  circulating  current  into  the  remote  portions  of  the  body, 
that  it  becomes  capable  of  being  appropriated  by  its  various  tissues  and  organs. 
Among  the  Invertebrata,  we  find  the  reception  of  alimentary  matter  into  the 
Circulating  system  to  be  entirely  accomplished  through  the  medium  of  the 
blood-vessels," which  are  distributed  upon  the  walls  of  the  digestive  cavity. 
But  in  the  Vertebrata,  we  find  an  additional  set  of  vessels  interposed  between 
the  walls  of  the  intestine  and  the  sanguiferous  system ;  for  the  purpose,  as  it 
would  seem,  of  taking  up  that  portion  of  the  nutritive  matter  which  is  not  in 
a  state  of  perfect  solution,  and  of  preparing  it  for  being  introduced  into  the 
current  of  the  blood.  These  are  the  lacteals,  or  absorbents  of  the  intestinal 
walls.  That  their  special  office  is  to  take  up  the  product  of  the  admixture  of 
the  chyme  with  the  biliary  and  pancreatic  fluids,  appears  from  the  fact,  that 
they  are  not  distributed  at  all  upon  the  walls  of  the  stomach,  nor  upon  those  of 
the  duodenum  above  the  point  of  entrance  of  the  hepatic  and  pancreatic  ducts; 
but  that  they  are  copiously  distributed  upon  the  walls  of  the  remainder  of  the 
small  intestine,  and  more  sparingly  upon  those  of  the  large.  Each  lacteal 
tube  originates  in  the  interior  of  one  of  the  villous  processes  of  the  mucous 
membrane  lining  the  intestinal  tube.  The  accompanying  figure  represents  the 
appearance  offered  by  the  incipient  lacteals,  in  a  villus  of  the  jejunum  of  a 
young  man,  who  had  been  hung  soon  after  taking  a  full  meal  of  farinaceous 
food.  The  trunk  that  issues  from  the  villus  is  formed  by  the  confluence  of 

43* 


510  OF  ABSORPTION  AND  SANGUIFICATION. 

Pig.  204.  several  smaller  branches,  whose  origin  it  is  difficult  to 

trace ;  but  it  is  probable  that  they  form  loops  by  anasto- 
mosis with  each  other,  so  that  there  is  no  proper  free 
extremity  in  any  case.     It  is  quite  certain  that  the  lac- 
teals  never  open  by  free  orifices  upon  the  surface  of  the 
intestine,  as  was  formerly  imagined.   From  the  researches 
of  Mr.  J.  Goodsir,  already  referred  to  (§  181),  it  appears 
that  these  loops  are  imbedded  in  a  mass  of  cells,  which 
are  the  real  agents  in  the  selection  of  the  materials  that 
are  destined  to  be  conveyed  into  the  lacteals.     When 
these  cells  have  distended  themselves,  by  their  inherent 
one  of  the  intestinal  viiii,    POWCT  of  growth,  with  the  materials  which  are  adapted 
with  the  commencement  of    to  tnelr  selecting  function,  and  have  reached  their  full 
a  lacteal.  term  of  maturity,  they  appear  to  yield  their  contents  to 

the  absorbent  vessels,  either  by  bursting  or  by  deli- 
quescence.— It  is  thought  by  Prof.  E.  Weber,  that  the  epithelial  cells,  which 
cover  the  villus,  perform  a  preliminary  office;  the  nutrient  matter  being  first 
absorbed  and  partially  prepared  by  them ;  and  then  being  drawn,  through  the 
basement  membrane  of  the  villus,  into  the  special  absorbent  cells  which  form 
part  of  its  substance.  This  seems  the  more  likely,  as  we  shall  hereafter 
find  that  the  epithelial  cells  of  the  placental  tufts  appear  to  perform  a  like 
function. 

673.  The  villi  are  also  furnished  with  a  minute   plexus  of  blood-vessels  ; 
of  which  the  larger  branches  may  be  seen  with  the  naked  eye,  when  they  are 
distended  with  blood,  or  with  coloured  injection  (Figs.  205,  206).     'The  par- 
ticular arrangement  of  the  capillaries  of  which  the  plexus  is  formed,  varies  in 
different  animals;  but  in  all  they  seem  to  be  most  copiously  distributed  upon 
the  surface  of  the  villus.    The  purpose  of  these  may  be  partly  to  afford  some 
of  the  materials  for  the  development  of  the  absorbent  cells ;  and  this  would 
seem  probable  from  the  recent  experiments  of  Mr.  Fenwick,*  which  show 
that  the  lacteals  will  not  absorb  alimentary  matter  from  any  part  of  the  intes- 
tinal canal,  in  which  the  blood  is  not  circulating.     But  there  can  be  no  reason- 
able doubt,  that  the  blood-vessels  of  the  mucous  membrane  lining  the  digestive 
cavity,  and  especially  those  of  the  villi,  perform  an  important  part  in  the  func- 
tion of  Absorption.     This  is  established  by  the  fact,  that  soluble  substances 
introduced  into  the  stomach,  and  prevented  from  passing  beyond  its  pyloric 
orifice,  are  absorbed  from  its  walls. 

674.  In  regard  to  the   degree  in  which  the  function  of  Nutritive  Absorp- 
tion is  performed  by  the  Lacteals,  and  by  the  Sanguiferous  System,  respect- 
ively, considerable  difference  of  opinion  has  prevailed.     When  the  Absorbent 
vessels  were  first  discovered,  and  their  functional  importance  perceived,  it 
was  imagined  that  the  introduction  of  alimentary  fluid  into  the  vascular  sys- 
tem took  place  by  them  alone.    A  slight  knowledge  of  Comparative  Anatomy, 
however,  might  have  sufficed  to  correct  this  error;  since  no  lacteals  exist  in 
the  Invertebrated  animals,  the  function  of  Absorption  being  performed  by  the 
Mesenteric  blood-vessels  only ;  from  which  it  is  evident,  that  these  do  pos- 
sess the  power  of  absorption :   and   it  is   scarcely  to  be  supposed   that  they 
should  not  exercise  this  power  in  Vertebrated  animals  also,  since  their  dis- 
position on  the  walls  of  the  intestinal  cavity  is  evidently  favourable  to  it.    On 
the  other  hand,  the  introduction  of  a  new  and  distinct  system  of  vessels  would 
seem  to  indicate,  that  they  must  have  some  special  purpose ;  and  there  can 
be  no  doubt  that  the  absorption  of  certain  kinds  of  nutritive  matter  is  that 
for  which  they  are  peculiarly  designed.     The  fluid  found  in  the  lacteals  is 

*  Lancet,  Jan.  and  Feb.  1845. 


ABSORPTION  BY  BLOOD-VESSELS  OF  VILLI. 

Fig.  205. 


511 


Vessels  of  an  intestinal  villus 
of  a  Hare,  from  a  dry  prepara- 
tion by  DSHinger;  1,  1,  veins 
rilled  with  white  injection  ;  2,  2, 
arteries  injected  red.  Magnified 
about  45  diameters. 


A,  apex  of  intestinal  vil- 
lus from  the  duodenum  of 
Human  female  ;  B,  a  mesh  of 
the  vascular  net-work,  1,  1, 
filled  up  with  delicate  cellu- 
lar tissue,  2,  magnified  about 
45  diameters. 


almost  invariably  the  same;  being  that  to  which  the  name  chyle  has  been 
applied.  It  appears  from  the  uniformity  of  its  composition,  which  forms  a 
striking  contrast  with  the  diversity  of  the  food  from  which  it  is  obtained,  that 
the  lacteals  (or  rather  the  absorbent  cells,  amongst  which  they  originate)  have 
in  some  degree  the  power  of  selecting  the  particles  of  which  it  is  composed  ; 
and  that,  whilst  they  take  up  such  a  proportion  of  each  class  of  alimentary 
materials  as  will  rightly  blend  with  the  rest  in  the  nutritious  fluid,  they  reject 
not  only  the  remainder,  but  also  (for  the  most  part  at  least)  any  other  ingre- 
dients which  may  be  contained  in  the  fluid  of  the  intestines.  Such  may  be 
stated  as  the  general  result  of  the  experiments  that  have  been  made  to  de- 
termine their  function ;  though  it  is  unquestionable  that  extraneous  substances, 
especially  of  a  saline  nature,  occasionally  find  their  way  into  this  system  of 
vessels.  This  may  not  improbably  be  due  to  a  correspondence  in  the  size 
and  form  of  the  ultimate  particles  of  such  substances,  with  those  of  the  mate- 
rials normally  absorbed  by  the  lacteals.* 

675.  On  the  other  hand,  the  Blood-vessels  seem  to  be  less  concerned  in 
nutritive  absorption,  but  take  up  from  the  alimentary  canal  a  portion  of  almost 
any  fluid  matters  which  it  may  contain.  This  seems  to  have  been  established 
by  the  carefully-conducted  experiments  of  MM.  Tiedemann  and  Gmelin,  who 

*  Experiments  upon  the  function  of  Absorption  in  Plants,  whose  radical  vessels  have  a 
corresponding  power  of  selection,  appear  likely  to  assist  in  elucidating  this  interesting  subject. 
By  the  experiments  of  Dr.  Daubeny  it  has  been  ascertained,  that  if  a  plant  absorb  any  par- 
ticular saline  compound,  it  can  also  be  made  to  absorb  those  which  are  isomorphous  with  it, 
though  it  will  reject  most  others. — See  Princ.  of  Gen.  and  Comp.  Phys.  ,§  294. 


512  OF  ABSORPTION  AND  SANGUIFICATION. 

mingled  with  the  food  of  animals  various  substances,  which,  by  their  colour, 
odour,  or  chemical  properties,  might  be  easily  detected  in  the  fluids  of  the 
body.  After  some  time  the  animal  was  examined ;  and  the  result  was,  that 
unequivocal  traces  of  the  substances  were  not  unfrequently  detected  in  the 
venous  blood  and  in  the  urine ;  whilst  it  was  only  in  a  very  few  instances, 
that  any  indication  of  them  could  be  discovered  in  the  chyle.  The  colouring 
matters  employed  were  various  vegetable  substances ;  such  as  gamboge,  mad- 
der, and  rhubarb :  the  odorous  substances  were  camphor,  musk,  assafostida, 
&c. ;  while,  in  other  cases,  various  saline  bodies,  such  as  muriate  of  barytes, 
acetate  of  lead  and  of  mercury,  and  some  of  the  prussiates,  which  might  easily 
be  detected  by  chemical  tests,  were  mixed  with  the  food.  The  colouring 
matters,  for  the  most  part,  were  carried  out  of  the  system,  without  being  re- 
ceived either  into  the  veins  or  lacteals ;  the  odorous  substances  were  gene- 
rally detected  in  the  venous  blood  and  in  the  urine,  but  not  in  the  chyle ; 
whilst  of  the  saline  substances,  many  were  found  in  the  blood  and  in  the 
urine,  and  a  very  few  only  in  the  chyle.  A  similar  conclusion  might  be 
drawn  from  the  numerous  instances  in  which  various  substances  introduced 
into  the  intestines  have  been  detected  in  the  blood,  although  the  thoracic  duct 
had  been  tied ;  but  these  results  are  less  satisfactory,  because  even  if  there  is 
no  direct  communication  (as  maintained  by  many)  between  the  lacteals  and 
the  veins  in  the  mesenteric  glands,  the  partitions  which  separate  their  respect- 
ive contents  are  evidently  so  thin,  that  transudation  may  readily  take  place 
through  them. — It  would  seem  probable,  that  substances  perfectly  dissolved 
in  the  fluids  of  the  stomach,  are  taken  into  the  blood-vessels  so  copiously  dis- 
tributed on,  its  walls,  by  the  simple  and  necessary  process  of  Endosmose ;  in 
this  manner  we  may  account  for  the  fact,  that  saline  substances  are  for  the 
most  part  readily  absorbed  into  the  blood ;  and  there  seems  reason  to  believe 
that  the  Albuminous  portion  of  the  chyme,  together  with  the  Saccharine  prin- 
ciples or  the  products  of  their  transformation,  may  thus  be  introduced  directly 
into  the  circulating  current,  without  passing  through  the  lacteals. — On  this 
subject  there  is  much  need  of  further  information. 

2. — Absorption  from  the  Body  in  general. 

676.  The  Mucous  Membrane  of  the  alimentary  canal  is  by  no  means  the 
only  channel,  through  which  nutritive  or  other  substances  may  be  introduced 
into  the  circulating  apparatus.  The  Lymphatic  system  is  present  in  all  animals 
which  have  a  lacteal  system  ;  and  the  two  evidently  constitute  one  set  of  ves- 
sels. The  lymphatics,  however,  instead  of  commencing  on  the  intestinal 
walls,  are  distributed  through  the  greater  part  of  the  body,  especially  on  the 
Skin  ;  their  origins  cannot  be  clearly  traced  ;  but  they  seern  in  general  to  form 
a  plexus  in  the  substance  of  the  tissues,  from  which  the  convergent  trunks 
arise.  After  passing,  like  the  lacteals,  through  a  series  of  glandular  bodies 
(the  precise  nature  of  which  will  be  presently  considered,  §  682),  they  empty 
their  contents  into  the  same  receptacle  with  the  lacteals;  and  the  mingled 
products  of  both  pass  into  the  Sanguiferous  system. — We  find  in  the  Skin, 
also,  a  most  copious  distribution  of  capillary  blood-vessels,  the  arrangement  of 
which  is  by  no  means  unlike  that  of  the  blood-vessels  of  the  alimentary  canal ; 
and  its  surface  is  further  extended  by  the  elevations  that  form  the  sensory 
papillae,  which  are  in  many  points  comparable  to  the  intestinal  villi,  although 
their  special  function  is  so  different. — In  the  lowest  tribes  of  animals,  and  in 
the  earliest  condition  of  the  higher,  it  would  seem  as  if  Absorption  by  the  ex- 
ternal surface  is  almost  equally  important  to  the  maintenance  of  life,  with 
that  which  takes  place  through  the  internal  reflexion  of  it  forming  the  walls 
of  the  Digestive  cavity.  In  the  adult  condition  of  the  higher  animals,  how- 


ABSORPTION  THROUGH  THE  CUTANEOUS  SURFACE.  513 

ever,  the  special  function  of  the  latter  is  so  much  exalted,  that  itusually  super- 
sedes the  necessity  of  any  other  supply  ;  and  the  function  of  the  cutaneous 
and  pulmonary  surfaces  may  be  considered  as  rather  that  of  exhalation,  than 
of  absorption.  But  there  are  peculiar  conditions  of  the  system,  in  which  the 
imbibition  of  fluid  through  these  surfaces  is  performed  with  great'  activity, 
supplying  what  would  otherwise  be  a  most  important  deficiency.  It  may 
take  place  either  through  the  direct  application  of  fluid  to  the  surface,  or  even 
through  the  medium  of  the  atmosphere,  in  which  a  greater  or  less  proportion 
of  watery  vapour  is  usually  dissolved.  This  absorption  occurs  most  vigour- 
ously,  when  the  system  has  been  drained  of  its  fluid,  either  by  an  excess  of 
the  excretions,  or  by  a  diminution  of  the  regular  supply. 

677.  It  may  be  desirable  to  adduce  some  individual  cases,  which  will  set 
this  function  in  a  striking  point  of  view;  and  those  may  be  first  noticed,  in 
which  the  absorption  took  place,  through  the  contact  of  liquids  with  the  skin. 
It  is  well  known  that  shipwrecked  sailors,  and  others,  who  are  suffering  from 
thirst,  owing  to  the  want  of  fresh  water,  find  it  greatly  alleviated,  or  altogether 
relieved,  by  dipping  their  clothes  into  the  sea,  and  putting  them  on  whilst  still 
wet,  or  by  frequently  immersing  their  own  bodies. — Dr.  Currie  relates  the 
case  of  a  patient  labouring  under  dysphagia  in  its  most  advanced  stage;  the 
introduction  of  any  nutriment,  whether  solid  or  fluid  into  the  stomach',  having 
become  perfectly  impracticable.     Under  these  melancholy  circumstances,  an 
attempt  was  made  to  prolong  his  existence,  by  the  exhibition  of  nutritive  ene- 
mata,  and  by  immersion  of  the  body,  night  and  morning,  in  a  bath  of  milk  and 
water.     During  the  continuance  of  this  plan,  his  weight,  which  had  previously 
been  rapidly  diminishing,  remained  stationary,  although   the  quantity  of  the 
excretions  was  increased.     How  much  of  the  absorption,  which  must  have 
been  effected  to  replace  the  amount  of  excreted  fluid,  is  to  be  attributed  to  the 
baths,  and  how  much  to  the  enemata,  it  is  not  easy  to  say  ;  but  it  is  important 
to  remark  that  "  the  thirst,  which  was  troublesome  during  the  first  days  of  the 
patient's  abstinence,  was  abated,  and,  as  he  declared,  removed  by  the  tepid 
bath,  in  which  he  had  the  most  grateful  sensations."     "It  cannot  be  doubted," 
Dr.  Currie  observes,  "that  the  discharge  by  stool  and  perspiration  exceeded 
the  weight  of  the  clysters ;"  and  the  loss  by  the  urinary  excretion,  which  in- 
creased from  24  oz.  to  36  oz.  under  this  system,  is  only  to  be  accounted  for 
by  the  cutaneous  absorption. — Dr.  S.  Smith  mentions  that  a  man,  who  had 
lost  nearly  3  Ibs.  by  perspiration,  during  an  hour  and  a  quarter's  labour  in  a 
very  hot  atmosphere,  regained  8  oz.  by  immersion  in  a  warm  bath  at  95°,  for 
half  an  hour. — The  experiments  of  Dr.  Madden*  show  that  a  positive  increase 
usually  takes  place  in  the  weight  of  the  body,  during  immersion  in  the  warm 
bath,  even  though  there  is  at  the  same  time  a  continual  loss  of  weight  by  pul- 
monary exhalation,  and  by  transudationt  from  the  skin.     This  increase  was, 
in  some  instances,  as  much  as  5  drachms  in  half  an  hour ;  whilst  the  loss  of 
weight  during  the  previous  half  hour  had  been  65  drachms :  so  that,  if  the 
same  rate  of  loss  were  continued  in  the  bath,  the  real  gain  by  absorption  must 
have  been  nearly  an  ounce  and  a  half.     Why  this  gain  was   much  less  than 
in  the  cases  just  alluded  to,  is  at  once  accounted  for  by  the  fact  that  there  was 
no  deficiency,  in  the  latter  case,  of  the  fluids  naturally  present  in  the  body. 

678.  The  quantity  of  water  which  may  be  imbibed  from  the  vapour  of  the 
atmosphere,  would  exceed  belief,  were  not  the  facts  on  which  the  assertion 
rests,  beyond   all   question.     Dr.  Dill  relates  the  case  of  a  diabetic  patient, 

*  Prize  Essay  on  Cutaneous  Absorption,  pp.  59 — 63. 

t  That  part  of  the  function  of  cutaneous  transpiration,  which  consists  in  simple  exhalation , 
is  of  course  completely  checked  by  such  immersion  ;  but  that  which  is  the  result  of  an  actual 
secreting  process  in  the  cutaneous  glands  (CHAP,  xv.,  Sect.  8)  is  increased  by  heat,  even 
though  this  be  accompanied  with  moisture, 


514  OF  ABSORPTION  AND  SANGUIFICATION. 

who  for  five  weeks  passed  24  Ibs.  of  urine  every  twenty-four  hours  ;  his  in- 
gesta  during-  the  same  period  amounted  to  22  Ibs.  At  the  commencement  of 
the  disease  he  weighed  145  Ibs. ;  and  when  he  died,  27  Ibs.  of  loss  had  been 
sustained.  The  daily  excess  of  the  excretions  over  the  ingesta  could  not  have 
been  less*  than  4  Ibs. ;  making  140  Ibs.  for  the  thirty-five  days  during  which 
the  complaint  lasted.  If  from  this  we  deduct  the  amount  of  diminution  which 
the  weight  of  the  body  sustained  during  the  time,  we  shall  still  have  113  Ibs. 
to  be  accounted  for,  which  can  only  have  entered  the  body  from  the  atmo- 
sphere.— A  case  of  ovarian  dropsy  has  been  recorded,  in  which  it  was  ob- 
served that  the  patient,  during  eighteen  days,  drank  692  oz.  or  43  pints  of 
fluid,  and  that  she  discharged  by  urine  and  by  paracentesis,  1298  oz.  or  91 
pints,  which  leaves  a  balance  of  606  oz.  or  38  pints,  to  be  similarly  accounted 
for.* — The  following  remarkable  fact  is  mentioned  by  Dr.  Watson  in  his  Che- 
mical Essays.  "  A  lad  at  Newmarket,  having  been  almost  starved,  in  order 
that  he  might  be  reduced  to  a  proper  weight  for  riding  a  match,  was  weighed 
at  9  A.  M.,  and  again  at  10  A.  M.  ;  and  he  was  found  to  have  gained  nearly  30 
oz.  in  weight  in  the  course  of  this  hour,  though  he  had  only  drunk  half  a 
glass  of  wine  in  the  interim." — A  parallel  instance  was  related  to  the  Author 
by  the  late  Sir  G.  Hill,  then  Governor  of  St.  Vincent.  A  jockey  had  been 
for  some  time  in  training  for  a  r.ace,  in  which  that  gentleman  was  much  inte- 
rested ;  and  had  been  reduced  to  the  proper  weight.  On  the  morning  of  the 
trial,  being  much  oppressed  with  thirst,  he  took  one  cup  of  tea ;  and  shortly 
afterwards  his  weight  was  found  to  have  increased  6  Ibs. ;  so  that  he  was  in- 
capacitated for  riding. — Nearly  the  whole  of  the  increase  in  the  former  case, 
and  at  least  three-fourths  of  it  in  the  latter,  must  be  attributed  to  cutaneous 
absorption  ;  which  function  was  probably  stimulated  by  the  wine  that  was 
taken  in  the  one  case,  and  by  the  tea  in  the  other. 

679.  Not  only  water,  but  substances  dissolved  in  it,  may  be  thus  introduced. 
It  has  been  found  that,  after  bathing  in  infusions  of  madder,  rhubarb,  and  tur- 
meric, the  urine  was  tinged  with  these  substances;  and  that  a  garlic  plaster 
affected  the  breath,  when  every  care  was  taken,  by  breathing  through  a  tube 
connected  with  the  exterior  of  the  apartment,  that  the  odour  should  not  be  re- 
ceived into  the  lungs.t  Gallic  acid  has  been  found  in  the  urine,  after  the  ex- 
ternal application  of  a  decoction  of  a  bark  containing  it;  and  the  soothing  influ- 
ence in  cases  of  neuralgic  pain,  of  the  external  application  of  cherry-laurel 
water,  is  well  known.  Many  saline  substances  are  absorbed  by  the  skin, 
when  applied  to  it  in  solution ;  and  it  is  interesting  to  remark,  that,  contrary 
to  what  happens  in  regard  to  the  absorption  of  these  from  the  alimentary  ca- 
nal, they  are  for  the  most  part  more  readily  discoverable  in  the  absorbents 
than  in  the  veins.  This  is  probably  due  to  the  fact,  that  the  imbibition  of 
them  is  governed  entirely  by  physical  laws ;  in  obedience  to  -which,  they  pass 
most  readily  into  the  vessels  which  present  the  thinnest  walls  and  the  largest 
surface.  In  the  intestines,  the  vascular  plexus  on  each  villus  is  far  more  ex- 
tensive than  the  ramifying  lacteal  which  originates  in  it;  and  as  the  walls  of 
the  veins  are  thin,  there  is  considerable  facility  for  the  entrance  of  saline  and 
other  substances  into  the  general  current  of  the  circulation  ;  but  in  the  skin, 
the  lymphatics  are  distributed  much  more  minutely  and  extensively  than  the 
veins ;  and  soluble  matters,  therefore,  enter  them  in  preference  to  the  veins. 
The  absorbent  power  of  the  Lymphatics  of  the  Skin  is  well  shown  by  the 
following  experiment.  A  bandage  having  been  tied  by  Schreger  round  the 
hind-leg  of  a  Puppy,  the  limb  was  kept  for  twenty-four  hours  in  tepid  milk ; 

*  Madden,  loc.  cit. — In  this  case,  however,  something  is  to  be  allowed  for  the  quantity  of 
water  contained  in  the  solid  food  ingested. 

t  Dunglison'g  Physiology,  [Gth.  ed.,  vol.  i.  p.  647.] 


ABSORPTION  FROM  THE  BODY  IN  GENERAL.  515 

fct  the  expiration  of  this  period,  the  lymphatics  were  found  full  of  milk,  whilst 
the  veins  contained  none.  In  repeating  this  experiment  upon  a  young  man, 
no  milk  could  be  detected  in  the  blood  drawn  from  a  vein.  It  has  been  shown 
by  Miiller  that,  when  the  posterior  extremities  of  a  Frog  were  kept  for  two 
hours  in  a  solution  of  prtissiate  of  potass,  the  salt  had  freely  penetrated  the 
lymphatics,  but  had  not  entered  the  veins. — It  does  not  follow,  however,  from 
these  and  similar  experiments,  that  in  all  tissues  the  lymphatics  absorb  more 
readily  than  the  veins  ;  for  as  the  capillary  blood-vessels  in  the  lungs  are  much 
more  freely  exposed  to  the  surface  of  the  air-cells,  than  are  the  lymphatics, 
we  should,  on  the  principles  just  now  stated,  expect  the  former  to  absorb  more 
readily.  This  appears  from  experiment  to  be  the  fact ;  for  when  a  solution 
of  prussiate  of  potass  was  injected  by  Mayer  into  the  lungs,  the  salt  could  be 
detected  in  the  serum  of  the  blood  much  sooner  than  in  the  lymph,  and  in 
the  blood  of  the  left  cavities  of  the  heart,  before  it  had  reached  that  of  the 
right. 

680.  Our  inferences  with  regard  to  the  ordinary  functions  of  the  Lymphatic 
system,  however,  must  be  rather  drawn  from  the  nature  of  the  fluid  which  it 
contains,  and  from  the  uses  subsequently  made  of  it,  than  from  experiments 
such  as  the  preceding.     We  shall  presently  see,  that  there  is  a  close  corre- 
spondence in  composition  between  the  Chyle  of  the  Lacteals,  and  the  Lymph 
of  the  Lymphatics ;  the  chief  difference  being  the  presence  in  the  former,  of 
a  considerable  quantity  of  fatty  matter,  and  of  a  larger  proportion  of  the  as- 
similable substances  (albumen  and  fibrine)  which  are  equally  characteristic  of 
both  (§  691).     This  evident  conformity  in  the  nature  of  the  fluid  which  these 
two  sets  of  vessels  transmit,  joined  to  the  fact  of  the  fluid  Lymph,  like  the 
Chyle,  being  conveyed  into  the  general  current  fof  the  circulation,  just  before 
the  blood  is  again  transmitted  to  the  system  at  large,  almost  inevitably  leads 
to  the  inference,  that  the  lymph  is,  like  the  chyle,  a  nutritious  fluid,  and  is.  not 
of  an  excrementitious  character,  as  formerly  supposed.     On  the  other  hand, 
the  close  resemblance  between  the  contents  of  the  Lymphatics,  and  diluted 
Liquor  Sanguinis,  seems  to  indicate  that  'the  former  are  partly  derived  from 
the  fluid  portion  of  the  Blood,  which  has  transuded  through  the  walls  of  the 
Capillary  vessels  ;  and  we  shall  presently  see  reason  to   believe  that  this 
transudation  is  for  the  purpose  of  subjecting  certain  crude  materials,  that  have 
been  taken  up  direct  into  the  blood-vessels,  to  an  elaborating  or  preparatory 
agency,  which  it  seems  to  be  the  especial  object  of  the  Absorbent  system  to 
exert  upon  certain  of  the  nutritive  components  of  the  circulating  fluid. 

681.  But  it  seems  not  improbable  that  there  may  be  another  source  for  the 
contents  of  the  Lymphatics.     We  have  already  had  to  allude,  on  several  oc- 
casions, to  the  disintegration  which  is  continually  taking  place  within  the  living 
body;  whether  as  a  result  of  the  limited  duration  of  the  life  of  its  component 
parts,  or  as  a  consequence  of  the  decomposing  action  of  Oxygen.     Now  the 
death  of  the  tissues  by  no  means  involves  their  immediate  and  complete  de- 
struction ;  and  there  seems  no  more  reason  why  an  animal  should  not  derive 
support  from  its  own  dead  parts  than  from  the  dead  body  of  another  indi- 
vidual.    Whilst,  therefore,  the  matter,  which  has  undergone  too  complete  a 
disintegration  to  be  again  employed  as  nutrient  material,  is  carried  off  by  the 
excreting  processes  that  portion  which  is  capable  of  being  again  assimilated, 
may  be  taken  up  by  the  Lymphatic  system.     If  this  be  the  case,  we  may  say, 
with  Dr.  Prout,  that  "  a  sort  of  digestion  is  carried  on  in  all  parts  of  the  body." 
It  may  be  stated,  then,  as  a  general  proposition,  that  the  function  of  the  Ab- 
sorbent System  is  to  take  up,  and  to  convey  into   the   Circulating  apparatus, 
such  substances  as  are  capable   of  appropriation  to   the  nutritive  process ; 
whether  these  substances  be  directly  furnished  by  the  external  world,  or  be 
derived  from  the  disintegration  of  the  organism  itself.     We  have  seen  that, 


516  OF  ABSORPTION  AND  SANGUIFICATION. 

in  the  Lacteals,the  selecting  power  is  such,  that  these  vessels  are  not  disposed 
to  convey  into  the  systejn  any  substances  but  such  as  are  destined  for  this 
purpose ;  and  that  extraneous  matters  are  absorbed  in  preference  by  the  Me- 
senteric  Blood-vessels.  The  case  is  different,  however,  with  regard  to  the 
Lymphatics ;  for  there  is  reason  to  believe,  that  they  are  more  disposed  than 
the  veins  to  the  absorption  of  other  soluble  matters ;  especially  when  these 
are  brought  into  relation  with  the  skin,  through  which  the  lymphatic  vessels 
are  very  profusely  distributed. 

a.  Since  the  time  of  Hunter,  who  first  brought  prominently  forward  the  doctrine  alluded 
to,  it  has  been  commonly  supposed  that  the  function  of  the  Lymphatics  is  to  remove,  by  in- 
terstitial absorption,  the  effete  matter,  which  is  destined  to  be  carried  out  of  the  system ;  and 
any  undue   activity  in  this  process  (such  as  exists  in  ulceration),  or  any  deficiency  in  its 
energy  (such  as  gives  rise  to  dropsical  effusions,  and  other  collections  of  the  same  kind), 
have  been  attributed  to  excess  or  diminution  in  the  normal  operation  of  the  Absorbent  Sys- 
tem.— From  what  has  been  stated,  however,  it  appears  that  the  special  function  of  the 
Lymphatics,  like  that  of  the  Lacteals,  is  'nutritive  absorption;*  and  that  the  reception  of  any 
other  substances  into  their  interior,  must  be  looked  upon  as  resulting  simply  from  the  per- 
meability of  their  walls.     This  statement  applies  to  the  not  unfrequent   occurrence  of  the 
absorption  of  bile,  and  other  fluids,  from  the  walls  of  the  cavities  in  which  they  were  col- 
lected: with  regard  to  the  absorption  of  pus,  however,  which  has  been  occasionally  noticed 
to  take  place,  both  from  internal  collections,  and  from  open  ulcers,  it  may  be  remarked,  that 
the  lymphatic  vessels  were  not  improbably  laid  open  by  ulceration ;  since  in  no  other  way 
can  be  understood  the  entrance  of  globules  so  large  as  those  of  pus,  into  their  interior. 

b.  If  this  view  of  the  function  of  the  Lymphatics  be  correct,  it  follows  that  we  must  at- 
tribute to  the  Blood-vessels  the  absorption  of  the  truly  effete   particles ;  and  in  this  there 
would  seem  no  improbability.     We  know  that  Venous  blood  contains  the  elements  of  two 
important  excretions,  that  of  the  lungs  and  that  of  the  bile,  in  a  far  higher  amount  than  does 
arterial  blood ;  and  we  shall  hereafter  see,  that  there  is  a  certain  portion  of  the  fluid,  which 
consists  of  "  ill  defined  animal  principles"  that  seem  ready  to  be  thus  thrown  off. 

c.  It  may  be  further  remarked,  that  the  reciprocal  part  which  Hunter  imagined  the  Ar- 


*  The  Author,  at  the  time  of  the  publication  of  the  First  Edition  of  this  work,  believed 
this  view  to  be  altogether  novel ;  he  has  since  learned,  however,  that  a  similar  doctrine  had 
been  put  forward  by  Dr.  Moultrie,  of  South  Carolina,  in  the  American  Journal  of  the  Medi- 
cal Sciences,  for  the  year  1827. 

[In  the  American  Journal  of  the  Medical  Sciences,  for  1827,  Dr.  James  Moultrie  pub- 
lished an  essay  on  the  "  Uses  of  the  Lymph,"  in  which,  amongst  other  things  attempted  to 
be  sustained,  will  be  found  the  following  views. 

1.  The  lacteals  and  lymphatics  do  not  constitute,  as  they  are  supposed  to  do,  the  absorbent 
system  of  the  animal  economy;  they  do  not,  as  the  absorbent  theory  supposes,  remove  from 
the  organs  the  "cast  off  molecules"  of  which  they  are  composed,  or  carry/out  of  the  body 
the  "  effete"  particles  disintegrated  by  the  act  of  the  assimilative  function.  The  one  is  en- 
gaged in  the  preparation  and  introduction  of  chyle,  and  chyle  only  into  the  blood  ;  the  other 
in  elaborating  an  organizable  product — a  recrementitious  secretion  destined  to  unite  with  it 
for  objects  of  a  common  and  nutritious  nature.  2.  The  primary  object  of  the  lymph,  and 
that  for  which  it  is  made  to  commingle  with  the  chyle  in  the  thoracic  duct,  is  the  vitalization 
of  the  latter  fluid.  3.  The  truly  "effete"  matter  of  the  body  is  the  carbonaceous  element 
of  the  venous  blood,  to  which  may  be  added  the  urea  or  azotic  element  of  the  urine.  Than 
these,  we  know  of  nothing  to  which  that  term  can  be  applied.  4.  The  venous  and  not  the 
lacteal  or  lymphatic  system,  therefore,  is  the  "absorbent  system,"  in  any  disintegratory  or 
effete  sense  of  the  phrase.  5.  Nature,  in  effecting  the  elimination  of  excrementitious  mat- 
ter from  the  constituency  of  the  solid  or  fluid  parts,  appears  to  aim  at  restoring  to  the  physi- 
cal universe,  the  matter  temporarily  borrowed  for  subsistence,  in  a  state  of  elementary  sim- 
plicity, or  an  approximation  thereto;  that  is,  the  carbon  as  carbon,  the  azote  as  azote,  and 
hydrogen  and  oxygen  as  hydrogen  and  oxygen.  The  lungs  she  uses  as  one  medium  of  es- 
cape ;  the  kidneys  as  a  second ;  and  the  skin  as  a  third,  &c.  Hence,  the  carbonic  acid  gas 
of  respiration ;  the  urea  of  the  kidneys,  and  the  aqueous  exhalations  of  the  skin,  pulmonary 
transpiration  and  urine. 

These  doctrines  have  been  regularly  taught  by  Dr.  M.,  in  his  course  of  lectures  on  physi- 
ology, delivered  in  the  Medical  College  of  the  State  of  South  Carolina,  since  the  establish- 
ment of  the  College  in  1833.  They  have  also  been  recently  enforced  in  a  brochure  published 
by  Dr.  M.,  in  which  he  asserts  and  vindicates  his  claim  to  their  paternity.  On  the  Organic 
Functions  of  Jlnimals.  By  JAMES  MOVLTBIE,  M.D.,  etc.,  Charleston,  S.  C.  1844. — M.  C.] 


STRUCTURE  OF  ABSORBENT  GLANDULE. 


517 


teries  and  Lymphatics  to  perform  in  the  function  of  Nutrition,  is  quite  inconsistent  with 
what  is  now  known  of  the  nature  of  that  process:  for,  as  will  subsequently  appear,  it  en- 
tirely consists  in  a  reaction  between  the  tissues  and  the  nutritious  fluid,  in  which  the  vessels 
have  no  share  save  as  the  channels  of  supply.  When  these  channels  are  obstructed,  or  the 
supply  of  new  matter  is  cut  off  in  any  other  way,  the  removal  of  the  old  by  interstitial  ab- 
sorption becomes  evident;  and  that  this  is  accomplished  at  least  as  much  by  the  veins  as  by 
the  lymphatics,  appears  from  the  fact  that  in  some  tissues,  in  which  it  may  take  place  with, 
rapidity,  lymphatics  do  not  exist. 

3. — Of  the  Elaboration  of  the  Nutrient  Materials. 

682.  The  alimentary  substances,  taken  up  by  the  Absorbent  vessels,  seem 
very  far  from  being  capable  of  immediate  application  to  the  nutrition  of  the 
body;  for  we  find  that  they  are  not  conveyed  by  any  means  directly  into  the 
Circulating  current,  but  that  they  first  traverse  a  long  series  of  tubes,  convo- 
luted at  intervals  into  ganglia  or  knots  ;*  and  that,  in  the  course  of  this  pas- 
sage, they  undergo  considerable  changes,  which  tend  to  bring  the  fluid  into 
closer  relationship  with  the  Blood.  It  seems  probable  that  the  materials, 
which  are  directly  received  into  the  Blood-vessels,  are  equally  far  from  being 
immediately  applicable  to  the  Nutritive  processes ;  for  we  find,  in  connection 
with  the  vascular  system,  certain  bodies  having  the  essential  structure  of 
glands,  but  destitute  of  efferent  ducts ;  which  must  restore  to  the  circulating 
current  any  substances  which  they  withdraw  from  it;  and  which  there  are 
various  reasons  (as  will  presently  appear)  for  placing  in  the  same  category 
with  the  glandulae  of  the  Absorbent  system. — The  Absorbent  Glandulae,  whe- 
ther placed  upon  the  Lacteals  in  the  Mesentery,  or  upon  the  Lymphatics  in 
various  parts  of  the  body,  have  the  same  general  structure.  They  are  made 
up  of  convoluted  knots  of  absorbent  vessels,  the  simple  cylindrical  canals  of 
which,  however,  are  usually  dilated  into  larger  .cavities,  or  cells;  and  amongst 
these,  capillary  blood-vessels  are  minutely  distributed.  These  blood-vessels 
have  no  direct  communication  with  the  interior  of  the  absorbents  and  the 
cavities  of  the  glandulae,  being  separated  from  them  by  the  membranous  walls 
of  both  sets  of  tubes  ;  but  there  can  be  no  doubt  that  transudation  readily 
takes  place  from  one  set  of  canals  to  the  other.  The  epithelium,  which 
lines  the  absorbent  vessel,  undergoes  a  marked  change  where  the  vessel  en- 
ters the  gland ;  and  becomes  more  like  that  of  the  proper  glandular  follicles 
in  its  character.  Instead  of  being  flat  and  scale-like,  and  forming  a  single 
layer  in  close  apposition  with  the  basement-membrane,  as  it  does  in  the  ab- 
sorbents previous  to  their  entrance  into  the  gland  and  after  their  emergence 
from  it,  we  find  it  cornj)osed  of  numerous  layers  of  spherical  nucleated  cells, 
of  which  the  superficial  ones  are  easily  detached,  and  appear  to  be  identical 


Fig.  207. 


Fig.  208. 


©< 


Diagram  of  a  lymphatic  gland,  showing  the 
intra-glandular  network,  and  the  transition 
from  the  scale-like  epithelia  of  the  extra-glan- 
dular lymphatics,  to  the  nucleated  cells  of  the 
intra-glandular. 


Portion  of  intra-glandular  lymphatic, 
showing  along  the  lower  edge  the  thick- 
ness of  the  germinal  membrane,  and  upon, 
it,  the  thick  layer  of  glandular  epithelial 
cells. 


*  In  Reptiles,  in  which  there  are  no  glands  or  ganglia  in  the  Absorbent  system,  the  tubes 
are  immensely  extended  in  length. 
44 


518  OF  ABSORPTION  AND  SANGUIFICATION. 

with  the  cells  found  floating  in  the  Chyle.*    Their  purpose  will  be  considered 
hereafter. 

683.  To  the  class  of  Vascular  Glands  belong  the  Spleen,  the  Thymns 
and  Thyroid  Glands,  and  the  supra-Renal  Capsules.  With  the  exception  of 
the  first,  they  all  have  their  origin  (as  recently  ascertained  by  Mr.  J.  Good- 
sirt)  in  involuted  portions  of  the  Germinal  membrane ;  and,  at  an  early  period 
of  embryonic  life,  they  are  in  actual  continuity  with  each  other.  Their'original 
identity  of  function,  therefore,  cannot  be  doubted ;  and  the  probability  of  the 
inference,  which  rests  on  other  grounds,  that  this  function  is  to  assimilate  or 
elaborate  the  nutrient  materials  (in  the  manner  in  which  the  cells  of  the 
leaves  of  Plants  prepare  their  elaborated  sap),  is  strengthened  by  its  exact 
conformity  with  the  original  function  of  the  Germinal  membrane.  But  there 
is  no  improbability  that  they  may  severally  have  some  subsidiary  or  supple- 
mentary function  to  perform ;  varying  according  to  their  respective  structure, 
position,  and  connections.  This  seems  peculiarly  the  case  in  regard  to  the 
Spleen;  the  origin  of  which  body  is  not  the  same  with  that  of  the  other  three. 

a.  According  to  the  account  of  Dr.  Julian  Evans,£  whose  researches  appear  to  have  been 
more  successful  than  those  of  any  other  Anatomist,  the  Spleen  essentially  consists  of  a  fibrous 
membrane,  which  constitutes  its  exterior  envelope,  and  which  sends  prolongations  in  all 
directions  across  its  interior,  so  as  to  divide  it  into  a  number  of  minute  cavities  or  lacunas 
of  irregular  form.      These  Splenic  lacunae,  communicate  freely  with  each  other,  and  with 
the  Splenic  vein ;  and  they  are  lined  by  a  continuation  of  the  lining  membrane  of  the  latter, 
which  is  so  reflected  upon  itself,  as  to  leave  oval  or  circular  foramina,  by  which  each  lacuna 
opens  into  others,  or  into  the  splenic  vein.     The  lacunae,  whose  usual  diameter  is  estimated 
by  Dr.  Evans  at  from  half  to  one-third  of  a  line,  are  generally  traversed  by  filaments  of 
elastic  tissue,  imbedded  in  which  a  small  artery  and  vein  may  be  frequently  observed ;  over 
these  filaments,  the  lining  membrane  is  reflected  in  folds ;  and  in  this  manner  each  lacuna 
is  incompletely  divided  into  two  or  more  smaller  compartments.     There  is  no  direct  com- 
munication between  the  splenic  artery  and  the  interior  of  the  lacunae ;  but  its  branches  are 
distributed  through  the  intercellular  parenchyma  (which  will  be  presently  described);  and 
the  small  veins,  which  collect  the  blood  from  the  capillaries  of  the  organ,  convey  it  into 
these  cavities,  from  which  it  is  conveyed  away  by  the  splenic  vein.     The  lacunae  may  be 
readily  injected  from  the  splenic  vein  with  either  air  or  liquid, — provided  they  are  not  filled 
with  coagulated  blood ;  and  they  are  so  distensible,  that  the  organ  may  be  made  to  dilate  to 
many  times  its  original  size,  with  very  little  force.     This  is  especially  the  case  in  the  Spleen 
of  the  Herbivora;  lor  the  Spleen  of  a  Sheep,  weighing  4  ounces,  may  be  easily  made  to  con- 
tain 30  ounces  of  water.  That  of  Man,  however,  is  less  capable  of  this  kind  of  enlargement. 
— According  to  Dr.  Evans,  the  lacunae  of  the  spleen  never  contain  anything  but  blood  ;§  and 
he  notices  that  a  frequent  condition  of  the  Human  Spleen  after  death,  which  is  sometimes 
described  as  »  morbid  appearance,  consists  in  the  filling  of  the  lacunae  with  firmly-coagulated 
blood,  which  gives  a  granular  appearance  to  the  organ. 

b.  The  partitions  between  the  lacunae  are  formed,  not  only  by  the  membranes  already 
mentioned,  but  by  the  peculiar  parenchyma  of  the  Spleen;  which  constitutes  a  larger  part 
of  the  organ  in  Man  than  in  the  Herbivorous  Mammalia.     It  presents  a  half  fluid  appear- 
ance to  the  eye;  but  when  an  attempt  is  made  to  tear  it,  considerable  resistance  is  expe- 
rienced in  consequence  of  its  being  intersected  by  what  appear  to  be  minute  fibres.    When 
a  small  portion  of  it  is  pressed,  a  liquid  is  separated;  which  is  that  commonly  known  as  the 
Liquor  Lienis,  or  Splenic  blood;  and  which  is  usually  described  (but  erroneously,  according 
to  Dr.  E.)  as  filling  the  lacunae  of  the  Spleen      This  liquid,  when  diluted  with  serum  and 
examined  under  the  Microscope,  is  found  to  contain  two  kinds  of  corpuscles,— one  sort  being 
apparently  identical  with  ordinary  blood-corpuscles — and  the  other  with  the  globules  cha- 


*   See  Mr.  J.  Good  sir's  Anatomical  and  Pathological  Researches,  p.  46. 

t  Proceedings  of  the  Royal  Society,  1846. 

J  Lancet,  April  6,  1 844. 

§  "It  differs  in  no  respect  from  venous  blood  taken  out  of  any' other  part  of  the  portal 
system.  I  have  found  it  fluid  or  coagulated,  as  in  other  parts  of  the  venous  system ;  and  I 
have  frequently  pulled  out  from  the  splenic  vein  colourless  coagula.  Occasionally  a  number 
of  globules  may  be  distinguished  in  it,  resembling  those  found  in  the  parenchyma;  but  in 
these  cases  the  organ  appears  to  have  suffered  injury,  and  these  matters  appear  to  have  got 
into  the  cells  and  vein  in  consequence."  Loc.  cit. 


STRUCTURE  AND  FUNCTIONS  OF  THE  SPLEEN.  519 

racteristic  of  the  lymph  and  abundant  in  the  lymphatic  glands.  The  remaining  fibrous 
substance  consists  entirely  of  capillary  blood-vessels  and  lymphatics,  with  minute  corpuscles, 
much  smaller  than  blood-corpuscles,  varying  in  size  from  about  1-GOOOth  to  l-7000th  of  an 
inch,  of  spherical  form,  and  usually  corrugated  on  the  surface.  These  lie  in  great  numbers 
in  the  meshes  of  the  sanguiferous  capillaries;  and  the  minute  lymphatics  are  described  by 
Dr.  E.  as  connected  with  the  splenic  corpuscles,  and  apparently  arising  from  them. — Lying 
in  the  midst  of  the  parenchyma  are  found  a  large  number  of  bodies,  of  about  a  third  of  a  line 
in  diameter,  which  are  evidently  in  close  connection  with  the  vascular  system :  these  have 
long  been  known  as  the  Malpighian  bodies  of  the  spleen,  after  the  name  of  their  discoverer; 
but  since  his  time,  their  existence  has  been  denied,  or  other  appearances  have  been  mistaken 
for  them.  According  to  Dr.  E.,  they  in  all  respects  resemble  the  mesenteric  or  lymphatic 
glands  in  miniature, — consisting  as  they  do  of  convoluted  masses  of  blood-vessels  and  lym- 
phatics, united  together  by  elastic  tissue,  so  as  to  possess  considerable  firmness :  and  they 
further  correspond  with  them  in  this, — that  the  lymph  they  contain,  which  was  quite  trans- 
parent in  their  afferent  lymphatics,  now  becomes  somewhat  milky,  from  containing  a  large 
number  of  Lymph-globules. 

684.  In  regard  to  the  functions  of  the  Spleen,  great  uncertainty  exists.     It 
appears  from  the  foregoing  account  of  its  structure,  that  it  may  be  regarded 
as  an  organ  of  duplex  character,  and  probably  of  double  function.     The  eel- 
lated  structure  maybe  considered  as  a  multilocular  reservoir,  capable  of  great 
distention,  and  lined  with  a  continuation  of  the  inner  membrane  of  the  veinj 
receiving  blood,  on  the  one  hand,  from  the  veins  of  the  interior  of  the  organ, 
and  transmitting  it  onward  to  the  Vena  Porire ;  and  on  the  other  hand,  acting 
as  a  reservoir  for  the  venous  blood  of  the  abdomen,  when,  from  any  cause, 
its  passage  into  the  Vena  Cava  is  obstructed.     The  splenic  parenchyma,  on 
the  other  hand,  must  be  regarded  as  a  complex  Lymphatic  tissue,  essentially 
resembling  that  of  the  lymphatic  glands,  but  differently  arranged.     In  those 
animals  in  which  it  predominates,  as  in  Man,  the  artery  is  large  ;  on  the  other 
hand,  where  the  cellated  structure  is  most  developed,  as  in  the  Herbivora,  the 
Vein  is  very  large,  and  the  artery  comparatively  small. — Nothing  completely 
analogous  to  a  Spleen  is  found  in  Invertebrated  animals  ;  and  from  the  absence 
of  the  Lymphatic  system  in  them,  it  is  evident  that  the  parenchymatous  por- 
tion can  have  no  existence  as  such.    Something  analogous  to  the  cellated  por- 
tion of  the  Spleen,  however,  exists  in  the  venous  system  of  many  Cephalopoda: 
and  this  circumstance  is  an  additional  proof  of  the  duplicity  of  the  character 
of  this  remarkable  organ. 

685.  Out  of  the  numberless  theories  of  its  operation,  which  have  been  at 
different  times  brought  forwards,  the  one  which  seems  best  to  account  for  its 
cellated  structure,  is  that  which  regards  it  as  a  sort  of  diverticulum  or  reser- 
voir; which  may  serve  to  relieve  the  Portal  Venous  system  from  undue  dis- 
tention, under  a  great  variety  of  circumstances.     This  system  is  well  known 
to  be  destitute  of  valves ;   so  that  the  Splenic  vein  has   free  communication 
with  the  whole  of  it.     Hence  the  Spleen  will  be  a  ready  diverticulum  for  the 
venous  blood,  when  the  secreting  action  of  the  Liver  is   feeble,  so  that  the 
Portal  circulation  receives  a  partial  check  (§  832).     That  any  cause  of  con- 
gestion of  the  Portal  system  peculiarly  affects  the  Spleen,  has  been  proved  by 
experiment ;  for  after  the  Portal  Vein  has  been  tied,  the  Spleen  of  an  animal, 
which  previously  weighed  only  2  ounces,  has  been  found  to  weigh  a  pound 
and  a  quarter,  or  ten  times  as  much.     Now  it  is  evident  that  congestion  of 
the  Portal  system  is  liable  to  occur,  when  the  alimentary  canal  is  distended 
with  food  ;  and  this  from  two  causes, — the  pressure  on  the  Intestinal  veins, 
and  the  quantity  of  fluid  absorbed  by  these  veins.  Hence  it  may  be  conceived, 
thaf  the  Spleen,  by  affording  a  reservoir  into  which  the  superfluous  Venous 
blood  may  be  directed,  serves  an  important  purpose  in  preventing  congestion 
of  other  organs.     From  the  observations  of  Mr.  Dobson,*  it  appears  that  the 

*  London  Med.  and  Phys.  Journal,  Oct.  1820. 


520  OF  ABSORPTION  AND  SANGUIFICATION. 

Spleen  has  its  maximum  volume,  at  the  time  when  the  process  of  chymifica- 
tion  is  at  an  end, — namely,  about  five  hours  after  food  is  taken  ;  and  that  it 
is  small  and  contains  little  blood  seven  hours  later,  when  no  food  has  been 
taken  in  the  interval.  Hence  he  inferred,  that  this  organ  is  the  receptacle  for 
the  increased  quantity  of  Blood,  which  the  system  acquires  from  the  food,  and 
which  cannot,  without  danger,  be  admitted  into  the  blood-vessels  generally ; 
and  that  it  regains  its  previous  dimensions,  after  the  volume  of  the  circulat- 
ing fluid  has  been  reduced  by  secretion.  This  view  is  confirmed  by  the  fact 
noticed  by  several  observers, — that  the  Spleen  rapidly  increases  in  bulk  after 
the  ingestion  of  a  large  quantity  of  fluid,  which  is  absorbed  rather  by  the 
Veins  than  by  the  Lacteals.  It  has  been  further  stated  in  support  of  this 
theory,  that  animals  from  which  the  Spleen  has  been  removed,  are  very  lia- 
ble to  die  of  apoplexy,  if  they  take  a  large  quantity  of  food  at  a  time  ;  but 
that,  if  they  eat  moderately  and  frequently,  they  do  not  suffer  in  this  manner. 
The  use  of  the  Spleen  as  a  diverticulum  for  the  internal  Venous  circulation, 
is  further  borne  out  by  its  liability  to  become  enlarged  in  consequence  of  in- 
termittent fever  ;  during  the  cold  stage  of  which,  a  great  quantity  of  blood  is 
driven  from  the  surface  towards  the  internal  organs ;  and  it  may  be  easily 
imagined  that,  if  there  were  no  such  reservoir,  the  congestions  in  these  would 
be  much  more  dangerous  than  those  which  actually  do  occur.  The  perma- 
nent enlargement  of  the  organ  is  of  course,  on  this  idea  of  its  use,  a  result  of 
its  frequent  distention.  But  besides  this  safety-valve  function,  there  can  be 
little  doubt  that  the  Spleen  performs  another,  in  virtue  of  the  parenchymatous 
portion  of  its  structure  ;  and  that  this  function  corresponds  with  that  of  the 
Absorbent  Glands  in  general.  The  identity  in  structure  between  its  Malpi- 
ghian  bodies  and  the  ordinary  Lymphatic  glands,  is  such  as  clearly  points  to 
this  inference ;  which  is  confirmed  by  the  remarkable  fact,  determined  by  the 
recent  experiments  of  Prof.  Mayer,  that,  after  the  Spleen  has  been  extirpated, 
the  lymphatic  glands  of  the  neighbourhood  increase  in  size,  and  cluster  toge- 
ther as  they  enlarge,  so  as  to  form  an  organ  which  at  least  equals  the  original 
spleen  in  volume.*  This  circumstance  explains  the  reason  of  the  almost  in- 
variable negative  result  of  the  extirpation  of  the  Spleen ;  for  although  the 
operation  has  been  frequently  practised,  with  the  view  of  determining  the 
functions  of  the  organ  by  the  symptoms  presented  by  animals  after  its  removal, 
no  decided  change  in  the  ordinary  course  of  their  vital  phenomena  has  ever 
been  observed  ;  and  the  health,  if  at  all  disturbed  for  a  time,  is  afterwards  re- 
gained. Now  if  the  functions  of  the  Spleen, — putting  aside  the  safety-valve 
action  of  its  distensible  cavities, — be  the  same  with  that  of  the  Lymphatic 
Glands  in  general,  it  is  easy  to  understand,  how  its  loss  may  be  at  once  com- 
pensated by  an  increased  action  on  their  part,  and  how  it  may  be  permanently 
replaced  by  an  increased  development  of  some  of  those  bodies. — Thus,  then, 
we  may  fairly  regard  the  Spleen  as  concurring  in  function  with  the  glands  of 
the  Absorbent  system,  in  the  Assimilating  process,  by  which  the  crude  nutri- 
tive materials  are  rendered  fit  to  circulate  through  the  system  ;  the  difference 
between  them  appearing  to  be  chiefly  this, — that,  whilst  the  latter  operate  upon 
the  nutritive  substances  taken  up  by  the  Lacteals,  the  Spleen  exerts  its  influ- 
ence upon  those  which  have  been  received  into  the  Veins ;  separating  them 
from  the  mass  of  the  blood,  and  delivering  them  to  the  lymphatic  system  to 
be  further  elaborated. 

686.  The  Suprarenal  Capsules  seem  to  correspond  with  the  Spleen  in 
their  general  structure,  and  in  their  connection  with  the  Lymphatic  system; 
whilst,  in  the  arrangement  of  their  component  parts,  they  bear  more  resem- 
blance to  the  Kidney. 

*  Medical  Times,  March  29,  1845. 


SUPRA-RENAL  CAPSULES. THYMUS  GLAND. 


521 


a.  In  the  Supra-Renal  Capsules,  as  in  the  Kidneys,  there  is  an  obvious  difference  between 
the  cortical  and  the  medullary  substances.  The  former  is  of  a  yellowish  colour ;  and  presents 
an  appearance,  when  cut  into,  as  if  it  were. made  up  of  straight  parallel  fibres,  arranged  side 
by  side.  Of  these  straight  fibres,  however,  a  part  are  branches  of  arteries,  which  enter  this 
body  at  every  point  of  its  exterior,  from  a  capillary  network  covering  its  surface;  and  others 
are  corresponding  branches  of  veins,  that  receive  the  blood  from  these  arteries,  and  convey 
it  into  a  venous  plexus  which  forms  the  centre  of  the  organ.  Between  the  radiating  blood- 
vessels, there  are  found  lying,  in  the  cortical  substance,  numerous  parallel  cylinders  or  elongat- 
ed cones,  formed  by  closed  sacs  of  basement-membrane,  including  nuclei  and  cells  in  various 
stages  of  development,  with  fat-cells. — The  medullary  substance  is  partly  wiade  up  of  the  ve- 
nous plexus,  dilated  into  a  sort  of  cavernous  texture,  together  with  empty  cavities  or  lacunae, 
that  seem  destitute  of  a  lining  membrane,  and  contain  only  a  thick  grayish-white  fluid ;  and 
partly  of  an  intervening  parenchyma,  consisting  of  cells  in  various  stages  of  development. 
In  the  Human  adult,  there  is  a  great  predominance  of  nuclei,  which  seem  as  if  they  did  not 
attain  their  full  development ;  but  in  Ruminant  animals,  and  in  the  Human  subject  in  early 
life,  the  cells  are  more  or  less  developed,  and  then  resemble  the  ordinary  lymph-corpuscles 
in  size  and  appearance.  The  Lymphatics  are  of  large  size,  like  those  of  the  Spleen ;  and 
probably  convey  away  the  matter  which  has  been  elaborated  by  these  organs,  that  it  may  be 
mingled  with  that  which  is  being  taken  up  and  prepared  by  other  parts  of  the  Absorbent 
system.  The  Supra-Renal  capsules  attain  a  very  large  size  early  in  fcetal  life,  surpassing 
the  true  Kidneys  in  dimension,  up  to  the  tenth  or  twelfth  week :  but  they  afterwards  dimi- 
nish relatively  to  the  latter,  and  are  evidently  subordinate  organs  during  the  whole  remainder 
of  life. 

It  does  not  seem  unlikely  that  these  bodies,  like  the  Spleen,  have  a  double 
function ;  and  that,  besides  participating  in  the  general  actions  of  the  Absorb- 
ent glandulse,  they  may  serve  as  a  diverticulum  for  the  Renal  circulation,  when 
from  any  cause  the  secreting  function  of  the  Kidneys  is  retarded  or  checked, 
and  the  movement  of  bloocj  through  them  is  stagnated. 

687.  The  Thymus  Gland  is  another  body  which  seems  referrible  to  the 
same  group  ;  having  all  the  essential  characters  of  a  true  gland,  save  an  excre- 
tory duct ;  and  its  function  being  evidently  connected,  during  the  early  period 
of  life  at  least,  with  the  elaboration  of  nutritive  matter,  which  is  to  be  re- 
introduced  into  the  circulating  current. 

a.  Its  elementary  structure  may  be  best  understood  from  the  simple  form  it  presents  when 
it  is  first  capable  of  being  distinguished  in  the  embryo.  It  then  consists  of  a  single  tube, 
closed  at  both  ends,  and  filled  with  granular  matter  j  and  its  subsequent  development  consists 

[Fig.  209. 


A  section  of  the  Thymus  gland  at  the  eighth  month,  showing  its  anatomy ;  from  a  preparation  of 
Sir  A.  Cooper's ;  1,  the  cervical  portions  of  the  gland;  the  independence  of  the  two  lateral  glands  is 
well  marked ;  2,  secretory  follicles  seen  upon  the  surface  of  the  section ;  these  are  observed  in  all 
parts  of  the  section ;  3,  3,  the  pores  or  openings  of  the  secretory  follicles  and  pouches  ;  they  are  seen 
covering  the  whole  internal  surface  of  the  great  central  cavity  or  reservoir.  The  continuity  of  the 
reservoir  in  the  lower  or  thoracic  portion  of  the  gland  with  the  cervical  portion,  is  seen  in  the  figure.] 

44* 


522  ,  OF  ABSORPTION  AND  SANGUIFICATION. 

in  the  lateral  growth  of  branching  off-shoots  from  this  central  tubular  axis.  In  its  mature 
state,  therefore,  it  consists  of  an  assemblage  of  glandular  follicles,  which  are  surrounded  by 
a  plexus  of  blood-vessels;  and  these  follicles  all  communicate  with  the  central  reservoir,  from 
which,  however,  there  is  no  outlet.  The  Lymphatics  are  large,  and  communicate  directly 
with  the  Vena  Cava ;  but  their  immediate  connection  with  the  cavity  of  the  Thymus  body 
has  not  yet  been  demonstrated.  The  cavities  of  the  follicles  contain  a  fluid  in  which  a 
number  of  corpuscles  are  found,  giving  it  a  granular  appearance.  These  corpuscles  are,  for 
the  most  part,  in  the  condition  of  nuclei;  but  fully  developed  cells  are  found  among  them,  at 
the  period  when  the  function  of  this  body  seems  most  active.  The  chemical  nature  of  the 
.contents  at  this  period,  closely  resembles  that  of  the  ordinary  proteine-compounds. — It  has 
been  commonly  stated,  that  the  Thymus  attains  its  greatest  development,  in  relation  to  the 
rest  of  the  body,  during  the  latter  part  of  foetal  life ;  and  it  has  been  considered  as  an  organ 
peculiarly  connected  with  the  embryonic  condition.  But  this  is  a  mistake ;  for  the  greatest 
activity  in  the  growth  of  this  organ  manifests  itself  in  the  Human  infant,  soon  after  birth; 
and  it  is  then,  too,  that  its  functional  energy  seems  the  greatest.  This  rapid  state  of  growth, 
however,  soon  subsides  into  one  of  less  activity,  which  merely  serves  to  keep  up  its  propor- 
tion to  the  rest  of  the  body :  and  its  increase  usually  ceases  altogether  at  the  age  of  about 
two  years.  From  that  time,  during  a  variable  number  of  years,  it  remains  stationary  in 
point  of  size ;  but,  if  the  individual  be  adequately  nourished,  it  gradually  assumes  the  cha- 
racter of  a  mass  of  fat,  by  the  development  of  the  corpuscles  of  its  interior  into  fat-cells,  which 
secrete  adip'ose  matter  from  the  blood.  This  change  in  its  function  is  most  remarkable  in 
hybernating  Mammals ;  in  which  the  development  of  the  organ  continues,  even  in  an  in- 
creasing ratio,  until  the  animal  reaches  adult  age,  when  it  includes  a  large  quantity  of  fatty 
matter.  The  same  is  the  case,  generally  speaking,  among  Reptiles.  It  is  an  important  fact 
in  the  history  of  this  organ,  that  it  is  not  to  be  detected  in  Fishes ;  and  does  not  appear  to 
exist,  either  in  the  tadpole  state  of  the  Batrachian  reptiles,  or  in  the  Perennibranchiate  group ; 
so  that  we  may  regard  it  as  essentially  connected  with  pulmonic  respiration.* 

688.  Various  facts  lead  to  the  conclusion,  that  the  function  of  the  Thymus, 
at  the  period  of  its  highest  development,  is  that  of  elaborating  and  storing  up 
nutritive  materials,  to  supply  the  demand  which  is  peculiarly  active  during  the 
early  period  of  extra-uterine  life.    The  elaborating  action  probably  corresponds 
with  that  which  is  exerted  by  the  glands  of  the  Absorbent  system  ;  and  the 
product,  as  in  the  preceding  cases,  seems  to  be  conveyed  away  by  the  lymph- 
atics.    The  provision  of  a  store  of  nutritive  matter  seems  a  most  valuable  one, 
under  the  circumstances  in  which  it  is  met  with ;  the  waste  being  more  rapid 
and  variable  than  in  adults,  and  the  supply  not  constant.     Thus  it  has  been 
noticed  that,  in  over-driven  lambs,  the  thymus  soon  shrinks  remarkably  ;  but 
that  it  becomes  as  quickly  distended  again,  during  rest  and  plentiful  nourish- 
ment.    As  the  demand  becomes  less  energetic,  and  as  the  supplies  furnished 
by  other  organs  become  more  adequate  to  meet  it,4 the  Thymus  diminishes  in 
size,  and  no  longer  performs  the  same  function.     It  then  obviously  serves  to 
provide  a  store  of  material,  not  for  the  nutrition  of  the  body,  but  for  the  re- 
spiratory process,  when  this  has  to  be  carried  on  for  long  periods — as  in  hy- 
bernating Mammals  and  in  Reptiles— without  a  fresh  supply  of  food. — It  is 
possible,  that  the  Thymus  gland  may  further  stand  in  the  same  relation  to  the 
Lungs,  as  the  Spleen  to  the  Liver,  and  the  Supra-Renal  capsules  to  the  Kid- 
neys ;  that  is,  as  a  diverticulum  for  the  blood  transmitted  through  the  bron- 
chial arteries  (which  are  the  nutritive  vessels  of  the  Lungs),  before  the  Lungs 
acquire  their  full  development  in  comparison  with  other  organs,  or  when  any 
cause  subsequently  obstructs  the  circulation  through  their  capillaries. 

689.  The  Thyroid  Gland  bears  a  general  analogy  to  the  Thymus ;  but  its 
vesicles  are  distinct  from  each  other,  and  do  not  communicate  with  any  com- 
mon reservoir.     They  are   surrounded,  like  the  vesicles  of  the  true  glands, 
with  a  minute  capillary  plexus ;  and  in  the  fluid  they  contain,  numerous  cor- 
puscles are  found  suspended,  which  appear  to   be   cell-nuclei,  in  a  state  of 
more  or  less  advanced  development.     This  body  is  supplied  with  arteries  of 
considerable  size ;  and  with  peculiarly  large  lymphatics.     Though  propor- 

*  See  Mr.  Simon's  admirable  Prize  Essay  on  the  Thymus  Gland. 


THYROID  GLAND. ASSIMILATING  GLANDS  IN  GENERAL.  523 

tionably  larger  in  the  foetus  than  in  the  adult,  it  remains  of  considerable  size 
during  the  whole  of  life.  It  appears,  from  the  recent  inquiries  of  Mr.  Simon,* 
that  a  Thyroid  gland,  or  some  organ  representing  it  in  place  and  office,  exists 
in  all  Vertebrated  animals.  It  presents  its  simplest  form  in  the  class  of  Fishes  ; 
in  some  of  which  it  appears  to  consist  merely  of  a  plexus  of  capillary  ves- 
sels, connected  with  the  origin  of  the  cerebral  vessels,  and  capable,  by  its  dis- 
tensibility,  of  relieving  the  latter,  in  case  of  any  obstruction  to  the  proper 
movement  of  blood  through  them.  In  the  higher  forms  of  this  organ,  the 
glandular  structure, — consisting  of  closed  vesicles  over  which  the  capillary 
plexus  is  distributed,  and  of  their  cellular  contents, — is  superadded  ;  and  the 
organ  then  appears,  like  the  Spleen,  to  be  destined  for  two  different  uses  ; 
namely,  to  serve  as  a  diverticulum  to  the  Cerebral  circulation ;  and  to  aid  in 
the  elaboration  of  nutritive  matter,  which  is  taken  up  by  the  Absorbent  sys- 
tem, and  which  is  again  poured  by  it  into  the  general  current  of  the  circula- 
tion. 

690.  Thus  the  Spleen,  the  Supra-Renal  Capsules,  the  Thymus  Gland,  and 
the  Thyroid  Gland,  all  seem  to  share  in  the  preparation  of  the  nutritive  ma- 
terials of  the  blood,  along  with  the  ordinary  glandulae  of  the  Absorbent  system. 
In  fact,  we  may  regard  them  all  as  together  constituting  an  apparatus,  which 
is  precisely  analogous  to  that  of  the  ordinary  glands,  but  of  which  the  element- 
ary parts  are  scattered  through  the  body,  instead  of  being  collected  into  one 
compact  structure.  Thus  if  we  could  imagine  any  tubular  gland,  such  as  the 
Kidney  or  the  Testis,  to  be  unravelled,  and  its  convoluted  tubuli  to  be  spread 
through  the  system,  yet  all  discharging  their  contents  by  a  common  outlet,  we 
should  have  no  unapt  representation  of  the  Lymphatic  portion  of  the  Absorb- 
ent system.  Its  function  appears  to  be,  .to  separate  the  crude  Albuminous 
matter  from  the  blood,  to  subject  it  to  an  elaborating  action  performed  by  the 
epithelium-cells  lining  the  tubes,  and  then  to  pour  forth  this  elaborated  pro- 
duct,— not  as  an  excretion  to  be  carried  out  of  the  body, — but  (in  conjunction 
with  that,  which  has  been  newly  taken  in  by  the  Lacteal  portion  of  the  sys- 
tem, and  which  has  undergone  elaboration  by  its  glandulae),  into  the  blood- 
vessels, which  are  to  convey  it  to  the  different  parts  of  the  body  where  it  is 
to  be  appropriated.  The  four  bodies  we  have  been  just  considering,  appear 
to  be,  so  far  as  their  glandular  function  is  concerned,  appendages  to  this  sys- 
tem. Their  uses  as  diverticula  to  the  circulation  through  other  organs,  render 
them  liable  to  occasional  distention  with  blood ;  and  it  seems  determined  that 
this  blood  shall  not  lie  useless,  but  shall  be  subservient  to  the  action  in  ques~ 
tion ;  the  gland-cells  that  line  the  cavities  of  the  organ  withdrawing  certain 
constituents  of  the  blood,  to  restore  them,  through  the  Lymphatic  system,  in 
a  state  of  more  complete  preparation  for  the  operations  of  Nutrition.  Their 
function  is  very  probably  vicarious;  that  is,  the  determination  of  blood  is 
greatest  (through  the  state  of  the  other  organs)  at  one  time  to  one  of  these  bodies, 
and  at  another  time  to  another.  Hence  the  effects  of  the  loss  of  any  one  of 
them  are  not  serious ;  as  the  others  are  enabled  in  great  degree  to  discharge 
its  duty. 

4. — Composition  and  Properties  of  the  Chyle  and  Lymph. 

691.  The  chief  chemical  difference  between  the  Chyle  and  the  Lymph, 
consists  in  the  much  smaller  proportion  of  solid  matter  in  the  latter,  and  in  the 
almost  entire  absence  of  fat,  which  is  an  important  constituent  of  the  former. 
This  is  well  shown  in  the  following  comparative  analyses,  performed  by  Dr. 
G.  0.  Rees,  of  the  fluids  obtained  from  the  lacteal  and  lymphatic  vessels  of  a 

*  Philosophical  Transactions,  1844. 


524  OF  ABSORPTION  AND  SANGUIFICATION. 

donkey,  previously  to  their  entrance  into  the  thoracic  duct:  the  animal  having 
had  a  full  meal  seven  hours  before  its  death. 

CHYLE.  LYMPH. 

Water       . 90-237  95-536 

Albuminous  matter  (coagulable  by  heat)           .         .         .           3-516  1*200 

Fibrinous  matter  (spontaneously  coagulable)      .         .         .           0-370  0-120 

Animal  extractive  matter,  soluble  in  water  and  alcohol      .            0-332  0*240 

Animal  extractive  matter,  soluble  in  water  only         .         .            1-233  1.319 

Fatty  matter 3-601  a  trace. 

Salts; — Alkaline  chloride,  sulphate  and  carbonate,  with  traces  of 

alkaline  phosphate,  oxide  of  iron         ....           0-711  0*585 

100-000         100-000 

The  Lymph  obtained  from  the  neck  of  a  horse  has  been  recently  analyzed  by 
Nasse,  with  nearly  the  same  result.  He  found  it  to  contain  95  per  cent,  of 
water;  and  the  5  per  cent,  of  solid  matter  was  chiefly  composed  of  albumen 
and  fibrine,  with  watery  extractive, — scarcely  a  trace  of  fat  being  to  be  found. 
The  proportions  of  saline  matter  were  found  to  be  remarkably  coincident  with 
those  which  exist  in  the  serum  of  the  blood;  as  might  be  expected  from  the 
fact,  that  the  fluid  portion  of  the  lymph  must  have  its  origin  in  that  which  has 
transuded  through  the  blood-vessels  :  the  absolute  quantity,  however,  is  rather 
less. — A  similar  analysis  of  the  Chyle  of  a  cat  by  Nasse,  has  given  results 
very  closely  correspondent  with  that  of  Dr.  Rees;  for  the  proportion  of  water 
was  90'5  per  cent.  ;  and  of  the  9*5  parts  of  solid  matter,  the  albumen,  fibrine, 
and  extractive  amounted  to  more  than  5,  and  the  fat  to  more  than  3  parts. — 
Dr.  Rees  has  also  analyzed  the  fluid  of  the  Thoracic  duct  of  Man;  and  found 
it  to  consist  of  90*48  per  cent,  of  water,  7'08  parts  of  albumen  and  fibrine, 
1*08  parts  of  aqueous  and  alcoholic  extractive,  and  0*92  of  fatty  matter,  with 
0*44  per  cent,  of  salines.  Thus  the  composition  of  this  fluid  would  seem  to 
resemble  that  of  the  Lymph,  rather  than  that  of  the  Chyle ;  the  proportion  of 
the  fatty  to  that  of  the  albuminous  matter  being  very  small.  This,  however, 
might  have  been  very  probably  due  to  the  circumstance,  that  the  subject  from 
which  the  fluid  was  obtained  (an  executed  criminal)  had  eaten  but  little  for 
some  hours  before  his  death. 

692.  The  characters  of  the  Chyle  drawn  from  the  larger  absorbent  trunks, 
near  their  entrance  into  the  Receptaculum  Chyli,  are  very  different,  however, 
from  those  of  the  fluid  as  first  absorbed  into  the  Lacteals  ;  for  during  its 
passage  through  these  vessels,  and  their  ganglia  or  glands,  it  undergoes 
important  alterations,  which  gradually  assimilate  it  to  Blood.  The  chyle 
drawn  from  the  lacteals  that  traverse  the  intestinal  walls,  contains  Albumen  in 
a  state  of  complete  solution;  but  it  is  generally  destitute  of  the  power  of  co- 
agulation, no  Fibrine  being  present  in  it.  The  Salts,  also,  are  completely 
dissolved  ;  but  the  Oily  matter  presents  itself  in  the  form  of  globules  of  varia- 
ble size.*  It  is  generally  supposed,  that  the  milky  colour  of  the  chyle  is 
owing  to  these ;  but  Mr.  Gulliver  has  recently  pointed  outt  that  it  is  really  due 
to  an  immense  multitude  of  far  more  minute  particles,  which  he  describes  as 
forming  the  molecular  base  of  the  chyle.  These  molecules  are  most  abundant 
in  rich,  milky,  opaque  chyle ;  and  in  poorer  chyle,  which  is  semi-transparent 
or  opaline,  the  particles  float  thinly  or  separately  in  the  transparent  fluid,  and 
often  exhibit  the  vivid  motions  common  to  the  most  minute  molecules  of  vari- 
ous substances.  Such  is  their  minuteness,  that,  even  with  the  best  instru- 

*  These  oily  globules  are  more  abundant  in  the  Chyle  of  Man  and  of  the  Carnivora,  than 
in  that  of  the  Herbivora :  their  diameter  has  been  observed  to  vary  from  l-25,000th  to  l-2000th 
of  an  inch. 

•f  Dublin  Medical  Press,  Jan.  1,  1840,  and  Gerber's  General  Anatomy,  Appendix,  p.  88. 


CHARACTERS  AND  COMPOSITION  OF  CHYLE.  525 

ments,  it  is  impossible  to  form  an  exact  appreciation  either  of  their  form  or 
their  dimensions.  They  seem,  however,  to  be  generally  spherical ;  and  their 
diameter  may  be  estimated  at  between  l-36,000th  and  l-24,000th  of  an  inch. 
Their  chemical  nature  is  as  yet  uncertain :  they  are  remarkable  for  their  un- 
changeableness,  when  subjected  to  the  action  of  numerous  re-agents;  which 
quickly  affect  the  proper  Chyle-corpuscles;  and  they  are  readily  soluble  in 
Ether,  the  addition  of  which  causes  the  whole  molecular  base  instantly  to  dis- 
appear, not  a  particle  of  it  remaining;  whence  it  may  be  inferred  that  they 
consist  of  oily  or  fatty  matter.  The  milky  colour,  which  the  serum  of  blood 
sometimes  exhibits,  is  due  to  an  admixture  of  this,  molecular  base  with  the 
circulating  fluid  ;  it  is  most  common  in  young  animals  that  are  suckling  ;  but 
it  is  not  uncommon  in  adults,  and  is  not  to  be  attributed  to  an  absorption  of 
milk  into  the  chyle,  as  the  physical  properties  of  the  two  are  quite  different. 
(See  §  697,  e.) 

693.  During  the  passage  of  the  Chyle  through  the  absorbents  on  the  intes- 
tinal edge  of  the  Mesentery,  towards  the  Mesenteric  Glands,  its  character 
changes  in  several  important  particulars.  The  presence  of  Fibrine  begins  to 
manifest  itself,  by  the  slight  coagulability  of  the  fluid  when  withdrawn  from 
the  vessels ;  and  while  this  ingredient  increases,  the  Albumen  and  the  Oil- 
globules  gradually  diminish  in  amount.  The  Chyle  drawn  from  the  neigh- 
bourhood of  the  mesenteric  glands  exhibits  the  Corpuscles  regarded  as  cha- 
racteristic of  that  fluid ;  these  are  peculiarly  abundant  in  the  fluid  drawn  from 
the  glands  themselves  ;  and  they  are  constantly  found  in  it,  through  its  whole 
subsequent  course.  The  Chyle-corpuscles  are  much  larger  than  the  mole- 
cules just  described,  and  an  examination  of  their  character  presents  no  diffi- 
culty. Their  diameter  varies  from  1-7 11  Oth  to  l-2600th  of  an  inch ;  the 
average  being  about  l-4600th.  They  are  usually  minutely  granulated  on  the 
surface,  seldom  exhibiting  any  nuclei,  even  when  treated  with  acetic  acid  ;  but 
sometimes  three  or  four  central  particles  may  be  distinguished  within  them. 
— During  the  passage  of  the  Chyle  through  the  mesenteric  glands,  a  further 
increase  in  the  proportion  of  Fibrine  takes  place ;  and  the  resemblance  of 
the  fluid  to  Blood  becomes  more  apparent.  The  Chyle  drawn  from  the  vessels 
intermediate  between  these  and  the  central  duct,  possesses  a  pale  reddish- 
yellow  colour;  and,  when  allowed  to  stand  for  a  time,  undergoes  a  regular 
coagulation,  separating  into  clot  and  serum.  The  former  is  a  consistent  gela- 
tinous mass,  which,  when  examined  with  the  microscope,  is  found  to  include 
the  Chyle-corpuscles,  each  of  them  being  surrounded  by  a  delicate  film  of 
oil:  the  Fibrine  of  which  it  is  principally  composed,  differs  remarkably  from 
that  of  the  blood,  in  its  inferior  tendency  to  putrefaction  ;  whence  it  may  be 
inferred  that  it  has  not  yet  undergone  its  complete  vitalization.  The  serum 
contains  the  Albumen  and  Salts  in  solution,  and  a  proportion  of  the  Chyle- 
corpuscles  suspended  in  it.  It  is  curious,  however,  that  considerable  differ- 
ences in  the  perfection  of  the  coagulation,  and  in  its  duration,  should  present 
themselves  in  different  experiments.  Sometimes  the  chyle  sets  into  a  jelly- 
like  mass,  which,  without  any  separation  into  coagulum  and  serum,  liquefies 
again  at  the  end  of  half  an  hour,  and  remains  in  this  state.  This  change  takes 
place  in  the  true  coagulum  also,  if  it  be  kept  moist  for  a  sufficient  length  of 
time.  The  Chyle  from  the  Receptacnlum  and  Thoracic  J)uct  coagulates 
quickly,  often  almost  instantaneously;  and  few  or  none  of  the  corpuscles  re- 
main in  the  serum. — It  is  to  be  remembered  that  the  Lacteals  are  the  Lym- 
phatics of  the  intestinal  walls  and  mesentery ;  performing  that  function  of 
Interstitial  Absorption  which  is  elsewhere  accomplished  by  vessels  that  are 
not  concerned  in  the  introduction  of  alimentary  substances  from  without. 
During  the  intervals  of  digestion,  they  contain  a  fluid  which  is  in  all  respects 
conformable  to  the.  Lymph  of  the  Lymphatic  trunks. 


526  OF  ABSORPTION  AND  SANGUIFICATION. 

a.  The  fluid  drawn  from  the  Thoracic  Duct,  and  from  the  Absorbent  vessels  which  empty 
their  contents  into  it,  is  frequently  observed  to  present  a  decided  red  tinge,  which  increases 
on  exposure  to  the  air.  This  tinge  is  due  to  the  presence  of  true  Blood-corpuscles;  but 
these  are  somewhat  modified  in  form  and  size,  being  a  little  smaller  than  the  ordinary  Blood- 
discs,  and  frequently  angular,  granulated,  or  indented  at  the  edges.  By  Mr.  Lane*  it  is  stated 
that  this  intermixture  is  accidental ;  and  that  it  results  from  the  absorption  of  Blood-particles 
into  the  Lymphatics,  at  the  points  where  the  latter  are  divided,  in  making  the  sections  ne- 
cessary to  expose  the  centres  of  the  Absorbent  system;  and  he  mentions  a  striking- fact  in 
illustration  of  his  view.  He  considers  that  the  alteration  in  the  character  of  the  corpuscles 
is  due  to  the  action  of  the  Chyle  on  the  Blood,  since  many  other  fluids  will  produce  analogous 
effects;  and  he  states  that,  shortly  after  a  flow  of  chyle  into  the  blood,  a  large  number  of  such 
altered  discs  may  be  seen  in  the  circulating  fluid.  On  the  other  hand,  Mr.  Gulliver  and 
several  eminent  observers,  regard  these  blood-discs  as  true  constituents  of  the  fluid  of  the 
absorbents ;  and  suppose  that  they  are  in  process  of  formation.  Reasons  have  been  given, 
however,  for  the  belief,  that  the  red  Blood-discs  are  not  formed  from  the  Chyle-corpuscles; 
so  that  Mr.  Lane's  view  is  probably  the  correct  one.  Even  if  the  Blood-discs  are  not  intro- 
duced into  the  Lymphatics  during  the  operation  of  exposing  the  Thoracic  Duct,  it  may  not 
be  considered  as  improbable  that,  in  those  animals  in  which  the  Lymphatics  have  several 
communications  with  the  veins,  they  should  naturally  obtain  an  entrance  in  various  parts  of 
the  system.  Such  communications,  -according  to  Gerber,  decidedly  exist  in  the  Horse ;  and 
it  is  in  the  Chyle  of  that  animal,  that  the  rosy  tint,  and  the  Blood-corpuscles  which  occasion 
it,  have  been  chiefly  observed. — The  following  table,  slightly  modified  from  that  of  Gerber, 
presents  in  a  concise  form,  a  view. of  the  relative  proportions  of  the  three  chief  ingredients 
in  the  Chyle,  in  different  parts  of  the  absorbent  system,  and  thus  gives  an  idea  of  its  advance 
in  the  process  of  assimilation. 

In  the  afferent  or  peripheral  f  Fat,  in  maximum  quantity  (numerous  fat  or  oil  globules). 
Lacteals  (from  the    Intes- J  Albumen  in  minimum  quantity, 
tines    to    the    Mesenteric  j  Few  or  no  Chyle-corpuscles, 
glands).  (Fibrine  almost  entire  wanting. 

In    the    efferent    or    central  ["Fat,  in  medium  quantity  (fewer  oil  globules). 
Lacteals  (from  the  Mesen- j  Albumen,  in  maximum  quantity. 

teric  glands  to  the  Thoracic  j  Chyle-corpuscles  very  numerous,  but  imperfectly  developed. 
Duct).  (Fibrine  in  medium  quantity. 

(Tat,  in  minimum  quantity  (fewer  or  no  oil-globules). 
T     ti      Ti         •     T»  J  Albumen,  in  medium  quantity. 

1  Chyle-corpuscles  numerous,  and  more  distinctly  cellular. 
(Fibrine  in  maximum  quantity. 

694.  The  aspect  of  the  Lymph  greatly  differs  from  that  of  the  Chyle,  the 
former  being  nearly  transparent,  whilst  the  latter  is  opaque  or  opalescent;  and 
this  difference  is  readily  accounted  for,  when  the  assistance  of  the  microscope 
is  sought,  by  the   entire  absence  from  the   Lymph  of  that  molecular  base 
which  is  so  abundant  in  the  Chyle.     A  considerable  number  of  corpuscles 
are  generally  present  in  it;  and  these  seem  to  correspond  in  all  respects  with 
the   white  or  colourless   corpuscles  of  the  Blood  (§  151).     Their  amount, 
however,  is  extremely  variable ;  as  is   also  that  of  the  oil-globules,  which 
sometimes  occur,  whilst  in  other  instances  none  can  be  discovered.     Lymph 
coagulates  like   chyle;  a  colourless   clot  being  formed,  which  incloses  the 
greater  part  of  the  corpuscles. 

695.  The  fluid  drawn  from  the  Thoracic  Duct,  consisting  as  it  does  of  an 
admixture  of  Chyle  and  Lymph,  will  probably  vary  in  its  character  and  com- 
position, according  to  the  predominance  of  the  former,  or  of  the  latter,  of  these 
fluids.     It  may  be  noticed,  however,  that  the  floating  corpuscles  have  a  more 
distinctly  cellular  character  than  have  those  of  the  chyle  and  lymph ;  and 
that  they  are  of  larger  size,  their  diameter  usually  ranging  from  about  1 -2600th 
to  l-2900th  of  an  inch.     In  these  particulars,  they  correspond  with  the  Colour- 
less corpuscles  of  the  Blood;  as  also  in  the  change  they  exhibit  on  the  action 
of  acetic  acid,  which  brings  into  view  three  or  four  large  central  particles. 
Some  observations  have  been  recently  made  by  Bidder,  on  the  amount  of 

*  Cyclopaedia  of  Anatomy  and  Physiology,  vol.  iii.  p.  220. 


PHYSICAL  AND  VITAL  PROPERTIES  OF  THE  BLOOD.  527 

Jiquid  which  flows  through  the  Thoracic  duct  into  the  venous  system ;  and  if 
any  inference  can  be  fairly  drawn  from  the  measurement  of  the  quantity  de- 
livered in  the  course  of  a  few  minutes,  it  would  appear  that  the  total  amount 
thus  transmitted  in  one  day  is  nearly  or  quite  equal  to  the  entire  mass  of  the 
blood.  At  any  rate,  it  so  far  exceeds  the  amount  of  liquid  ingested,  that  we 
must  believe  a  large  portion  of  it  to  be  derived  from  the  circulating  current, — 
having  been  withdrawn  from  it  for  a  time,  to  be  again  delivered  into  its  stream, 
after  having  undergone  the  requisite  elaboration. 

5. — Physical  and  Vital  Properties  of  the  Blood. 

696.  Having  now  traced  the  steps,  by  which'  the  Blood  is  elaborated  and 
prepared  for  circulation  through  the  body,  and  having  formerly  inquired  into 
the  characters  of  its  chief  constituents  (Chap,  in.),  we  have  now  to  consider 
the  fluid  as  a  whole,  to  study  the  usual  proportions  of  these  constituents,  and 
the  properties  which  they  impart  to  it. — The  Blood,  whilst  circulating  in  the 
living  vessels,  may  be  seen  to  consist  of  a  transparent,  nearly  colourless, 
liquid,  termed  Liquor  sanguinis ;  in  which  the  Red  Corpuscles,  from  which 
the  Blood  of  Vertebrated  animals  derives  its  peculiar  hue,  as  well  as  the  White 
or  Colourless  corpuscles,  are  freely  suspended  and  carried  along  by  the  cur- 
rent.— On  the  other  hand,  when  the  Blood  has  been  drawn  from  the  body, 
and  is  allowed  to  remain  at  rest,  a  spontaneous  coagulation  takes  place,  sepa- 
rating it  into  Crassamenlum  and  Serum.  The  Crassamentum  or  Clot  is 
composed  of  a  network  of  Fibrine,  in  the  meshes  of  which  the  Corpuscles, 
both  red  and  colourless,  are  involved,  together  with  a  certain  amount  of  serous 
fluid.  The  Serum,  which  is  the  same  with  the  Liquor  Sanguinis  deprived  of 
its  Fibrine,  coagulates  by  heat,  and  is  therefore  known  to  contain  Albumen ; 
and  if  it  be  exposed  to  a  high  temperature,  sufficient  to  decompose  the  animal 
matter,  a  considerable  amount  of  earthy  and  alkaline  Salts  remains. — Thus 
we  have  four  principal  components  in  the  Blood;  namely,  Fibrine,  Mbumen, 
Corpuscles,  and  Saline  matter.  In  the  circulating  blood,  they  are  thus  com- 
bined : — 

Fibrine       } 

Albumen    >  In  solution,  forming  Liquor  Sanguinis. 

Salts  ) 

Corpuscles, — suspended  in  Liquor  Sanguinis. 

But  in  coagulated  blood,  they  are  combined  as  follows:— 

Fibrine        ) 
Corpuscles  $ 

c  -  >  Remaining  in  solution,  forming  Serum. 

In  the  blood  of  Man  and  the  higher  Vertebrata,  the  Colourless  Corpuscles 
usually  bear  so  small  a  proportion  to  the  Red,  that  they  have  until  recently 
escaped  notice.  In  Reptiles,  however,  they  attract  attention,  from  their 
marked  difference  in  size  and  form,  even  whilst  the  blood  is  moving  through 
the  capillaries ;  and  they  are  the  more  easily  watched,  owing  to  the  compara- 
tively small  number  of  the  Red  Corpuscles  in  those  animals.  The  blood  of 
the  Invertebrata  is  usually  pale,  and  contains  very  few  red  corpuscles;  indeed 
they  would  seem  to  be  absent  altogether  in  the  lower  Articulata  and  Mollusca. 
On  the  other  hand,  the  colourless  corpuscles  are  frequently  very  numerous, 
especially  during  the  periods  of  most  active  growth.  The  blood  of  these 
animals  may  be  likened,  therefore,  in  many  respects  to  the  Lymph  and  Chyle 
of  the  Vertebrata ;  and  the  resemblance  is  the  more  close,  as  there  is  no 


528 


OF  ABSORPTION  AND  SANGUIFICATION. 


distinction  among  the  Invertebrata  between  the  absorbent  and  sanguiferoits 
vessels. 

697.  The  proportion  of  the  several  components  of  Blood  is  subject  to  con- 
siderable variations,  within  the  limits  of  health.  Some  of  these  variations 
may  be  habitual,  depending  upon  the  constitution  of  the  individual,  his  diet, 
mode  of  life,  &c.;  whilst  others  are  probably  referrible  to  the  period  at  which 
the  last  meal  was  taken,  and  the  amount  of  bodily  exertion  made  within  a 
short  time  previous  to  the  analysis. 

a.  The  discordance  in  the  results  obtained  by  different  experimenters  is  doubtless  owing 
in  part  to  the  diversity  in  their  methods  of  analysis;*  but  even  where  the  same  method  is 
employed,  a  wide  diversity  is  apparent ;  as  in  the  analysis  of  MM.  Becquerel  and  Rodier. 
As  there  is  a  tolerably  constant  difference  between  the  Male  and  the  Female,  it  will  be  de- 
sirable to  class  them  separately  ;  and  the  results  of  some  of  the  most  recent  and  trustworthy 
analyses  of  each  will  be  brought  together  for  the  sake  of  comparison. — The  analyses  of  M. 
Lecanu  were  made  on  the  blood  of  two  stout  and  healthy  men ;  whilst  those  of  MM.  Bec- 
querel and  Rodier  give  the  maximum,  minimum,  and  mean  amount,  of  each  ingredient  in 
the  blood  of  eleven  healthy  men,  between  the  ages  of  21  and  66  years. 


Lecanu. 


Water    .     .     .     . 

Fibrine   .     .     . 

Corpuscles  .     . 

Albumen     .     . 

Extractive  mat- 
ters, Salts,  and 
loss 

Fatty  matters  .     . 


I. 

780-2 

2-1 

133-0 

66-3 

14-6 
3-8' 


ii. 

785-6 

3-6 

119-6 

71-5 

13-1 
66 


MM.  Eecquerel  and  Rodier. 

Mean. 

Maxima. 

Minima. 

779-0 

8(5b-0 

760-0 

2-2 

3-5 

1-5 

141-1 

152-0 

131-0 

69-4 

73-0 

62-0 

6-8 

8-0 

5-0 

1-5 

3-2 

1-6 

Simon.        Nasse. 


791-9 

2-0 

114-3 

75-6 

14-2 
2-0 


798-4 

2-3 

116-5 

74-2 

6-6 
2-0 


1000-0       1000-0       1000.0 


1000-0         1000-0 


The  following  table  gives  the  results  of  similar  analyses  on  the  blood  of  Females;  those 
of  MM.  Becquerel  and  Rodier  being  made  upon  eight  healthy  subjects  between  the  ages  of 
22  and  58  years. 


MM.  Becquerel  and  Rodier.         Simon. 
Mean.    Maxima.     Minima. 


Water 

Fibrine     .... 

Corpuscles    .         .         . 
Albumen  .... 
Extractive  matters  and  Salts 
Fatty  matters 


791-1 

813-0 

773'0 

801-4 

2-2 

2-5 

1-8 

2-2 

127-2 

137-5 

113-0 

106.1 

70-5 

75-5 

65-0 

77-6 

7-4 

8-5 

6.2 

100 

1-6 

2-9 

1-0 

2-7 

1000-0 


1000-0 


b.  Of  the  Fatty  matters  of  the  Blood,  a  portion  seems  to  correspond  with  the  constituents 
of  ordinary  Fat;  another  portion  seems  identical  with  the  Cholesterine,  or  Biliary  Fat;  whilst 
another  contains  Phosphorus,  and  seems  allied  to  the  fatty  acids  of  Nervous  matter  (§  249). 

c.  Of  the  nature  of  the  substances  classed  under  the  head  of  Extractive,  very  little  is 
known.     It  has  been  lately  asserted,  that  a  portion  of  them  consists  of  binoxide  of  proteine 
(§  116,  a)  ;  but  as  to  the  actual  existence  of  this  substance,  there  is  still  much  doubt    Under 
the  general  designation  of  extractive  are  arranged  the  "  ill-defined  animal  principles,"  which 
may  include  various  substances  in  a  state  of  change  or  disintegration,  that  are  being  elimi- 
nated from  the  blood  by  the  processes  of  Excretion. 

d.  The  Saline  constituents  of  the   Blood,  obtained  by  drying  and  incinerating  the  whole 
mass,  usually  amount  to  between  6  and  7  parts  in  1000.     More  than  half  their  total  quan- 
tity  is  composed  of  the  Chlorides  of  Sodium  and  Potassium ;  and  the  remainder  is  made  up 
of  the  tribasic  Phosphate  of  Soda,  the  Phosphates  of  Lime  and  Magnesia,  Sulphate  of  Soda, 


*  Thus  the  small  amount  of  Salts,  in  the  analysis  of  Nasse  and  of  MM.  Becquerel  and 
Rodier,  as  compared  with  those  of  MM.  Lecanu  and  Simon,  appears  due  to  the  fact  that  the 
former  express  only  the  free  salts,  whilst  the  latter  include  those  which  are  in  combination 
with  the  organic  constituents. 


USES  OF  THE  SEVERAL  CONSTITUENTS  OF  THE  BLOOD.          529 

and  a  little  Phosphate  and  Oxide  of  Iron.  Of  these,  the  chief  part  are  dissolved  in  the 
Serum  ;  but  the  Earthy  Phosphates,  which  are  insoluble  by  themselves,  are  probably  com- 
bined with  the  Proteine-compounds  (§  113);  and  the  iron  is  contained,  chiefly  or  entirely, 
in  the  red  corpuscles. — It  is  difficult  to  speak  with  certainty,  from  the  examination  of  the 
ashes  of  the  blood,  as  to  the  state  of  the  Saline  constituents  of  the  circulating  fluid.  Thus 
the  Serum  has  an  alkaline  reaction ;  and  this  has  been  supposed  to  be  due  to  the  presence 
of  alkaline  Carbonates.  Moreover  the  presence  of  the  Lactates  of  potass  and  soda  has  been 
usually  asserted.  On  the  other  hand,  the  recent  analyses  of  Enderlin,  which  have  been  con- 
firmed by  Liebig,  would  indicate  that  the  alkaline  reaction  is  entirely  due  to  the  presence  of 
the  tribasic  Phosphate  of  soda ;  and  that  no  alkaline  carbonates  or  lactates  exist  in  the  blood. 
This  discrepancy  seems  partly  due  to  the  mode  of  analysis  employed;  for  it  has  been  lately 
pointed  out  by  Dr.  G.  O.  Rees,*  that  although  the  ashes  of  the  entire  mass  of  blood  do  not 
effervesce  on  the  addition  of  an  acid,  effervescence  takes  place  when  acid  is  added  to  the 
ashes  of  the  serum,  showing  the  existence  in  it,  either  of  alkaline  Carbonates,  or  of  Lactates, 
which  have  been  reduced  to  the  state  of  Carbonates  by  incineration. — It  appears  that,  when 
the  entire  mass  of  blood  is  incinerated,  enough  phosphoric  acid  is  produced  from  the  phos- 
phorized  fats,  to  neutralize  the  alkaline  carbonates,  and  thus  to  prevent  their  presence  from 
being  recognized.  There  can  be  no  doubt,  however,  that  the  tribasic  Phosphate  of  Soda 
exists  as  such  in  the  blood,  and  contributes  to  its  alkaline  reaction ;  and  it  appears  to  confer 
upon  the  liquid  a  special  power  of  absorbing  Carbonic  Acid. 

e.  Some  very  interesting  observations  upon  the  state  of  the  blood  soon  after  a  meal,  have 
been  recently  made  by  Drs.  Buchanan  and  R.  D.  Thompson.  They  are  confirmatory  of  the 
belief  generally  entertained,  that  the  milky  appearance,  sometimes  presented  by  the  Serum, 
is  due  to  the  admixture  of  Chyle.  When  a  full  meal  containing  oily  matter  is  taken  after 
a  long  fast,  and  a  small  quantity  of  blood  is  drawn  previously  to  the  meal  and  at  intervals 
subsequently,  the  Serum,  though  quite  Jimpid  in  the  blood  first  drawn,  shows  an  incipient 
turbidity  about  half  an  hour  afterwards ;  this  turbidity  increases  for  about  six  hours  subse- 
quently, after  which  it  usually  begins  to  disappear.  The  period  at  which  the  discoloration 
is  the  greatest,  however,  and  the  length  of  time  during  which  it  continues,  vary  according 
to  the  kind  and  quality  of  the  food,  and  the  state  of  the  digestive  functions.  Neither  starch, 
nor  sugar,  nor  proteine-compounds,  alone  or  combined,  occasion  this  opacity  in  the  chyle ; 
but  it  seems  entirely  dependent  upon  an  admixture  of  oleaginous  matter  with  the  food. 
There  are  few  ordinary  meals,  however,  from  which  such  matter  is  altogether  excluded. 
When  such  milky  serum  is  examined  with  the  Microscope,  the  opacity  is  found  to  be  due 
to  the  presence  of  an  immense  number  of  exceedingly  minute  granules,  resembling  in  ap- 
pearance those  which  form  the  "  molecular  base"  of  the  chyle.  They  seem  to  be  composed 
of  two  chemically-distinct  substances;  for  when  the  milky  serum  is  agitated  with  ether,  a 
part  is  dissolved,  whilst  another  portion  remains  suspended  ;  and  this  latter  is  soluble  in 
caustic  potass.  The  former,  therefore,  appears  to  be  identical  with  the  "  molecular  base"  of 
the  Chyle,  and  to  be  of  an  oily  or  fatty  nature  ;  whilst  the  latter  belongs  to  the  proteine- 
compounds.  The  Crassarnentum  of  such  blood  often  exhibits  a  pellucid  fibrinous  crust, 
sometimes  interspersed  with  white  dots ;  and  this  seems  to  consist  of  an  imperfectly-assi- 
milated proteine-compound,  analogous  to  that  found  in  the  serum.  The  quantity  of  this  varies 
according  to  the  amount  of  the  proteine-compounds  present  in  the  food  ."f" — It  is  evident  from 
these  experiments,  that  the  assimilating  process  is  by  no  means  completed,  at  the  time  of 
the  passage  of  the  Chyle  into  the  Blood  ;  and  it  would  seem  that  the  return  of  the  trans- 
parency of  the  serum  is  due  to  the  gradual  removal  of  the  superfluous  fatty  matter  through 
the  respiratory  process,  whilst  the  proteine-compound,  of  which  part  of  the  granules  are 
composed,  is  gradually  reduced  to  a  state  of  perfect  solution. 

/.  The  occasional  presence  of  Sugar,  even  in  healthy  blood,  when  a  large  quantity  of 
saccharine  matter  exists  in  the  food,  appears  to  be  now  well  established.  But  it  seems  to 
be  commonly  transformed,  either  into  lactic  acid,  or  into  fatty  matter,  previously  to  its  recep- 
tion into  the  circulating  current,  This  last  transformation  is  partly  effected  through  the 
agency  of  the  Bile  ;  as  will  be  shown  hereafter  (§  835). 

698.  It  cannot  be  doubted  that,  upon  the  due  admixture  in  the  Blood  of  all 
these  elements,  the  regular  performance  of  its  actions  is  dependent.  In  regard 
to  its  physical  properties  merely,  it  is  easily  shown  that  a  slight  alteration  may 
produce  the  most  injurious  consequences;  for  a  certain  degree  of  viscidity  has 
been  found  (by  the  experiments  of  Poisseuille)  to  favour  the  passage  of  fluid 
through  capillary  tubes  ;  and  thus,  if  the  viscidity  of  the  blood  be  diminished 
by  a  loss  of  part  of  its  fibrine,  stagnation  of  the  current,  and  extravasation  of  a 

*  On  the  Analysis  of  the  Blood  and  Urine,  p.  30. 
|  Medical  Gazette,  Oct.  10,  1845. 
45 


530  OF  ABSORPTION  AND  SANGUIFICATION. 

portion  of  the  contents  of  the  vessels,  will  be  the  result.  This  has  been  fully 
proved  by  the  numerous  experiments  of  Magendie  ;  and  the  fact-is  one  of  very 
important  Pathological  applications  (§  707,  b}.  But  the  vital  properties  of  the 
fluid  are  still  more  immediately  dependent  upon  the  Fibrine  it  contains;  since, 
as  we  have  seen  reason  to  believe,  it  is  the  material  which  is  most  completely 
prepared  for  organization,  and  which  supplies  what  is  requisite  for  the  nutri- 
tion of  the  larger  proportion  of  the  solid  tissues  of  the  body.  It  is,  therefore, 
continually  being  withdrawn  from  the  blood  by  the  nutritive  operations;  and 
the  demand  appears  to  be  supplied,  in  part  by  the  influx  of  Fibrine  that  has 
been  prepared  in  the  Absorbent  system,  and  in  part  by  the  continued  trans- 
formation of  Albumen,  which  takes  place  during  the  circulation  of  the  Blood, 
and  of  which  we  have  seen  reason  to  believe  that  the  Colourless  Corpuscles 
are  the  instruments  (§§  153 — 159). — The  Albumen  of  the  Blood  is  the  raw 
material,  at  the  expense  of  which  not  only  the  Fibrine,  but  many  other  sub- 
stances, are  generated  during  the  nutritive  process.  All  the  Albuminous  com- 
pounds of  the  Secretions,  the  Horny  matter  of  the  Epidermic  tissues,  the 
Gelatine  of  the  simple  Fibrous  tissues,  and  the  Haematine  of  the  Red  Cor- 
puscles, may  be  regarded  as  almost  certainly  produced  by  the  transformation 
of  the  Albumen  of  the  Blood  ;  and  a  continual  supply  of  this  from  the  food 
is  therefore  requisite  to  preserve  the  due  proportion  in  the  circulating  fluid. — 
The  Red  Corpuscles  appear  to  be  more  connected  with  the  function  of  Respira- 
tion than  with  that  of  Nutrition  (§  150) ;  and  the  stimulating  action  of  Arterial 
blood,  especially  upon  the  Nervous  and  Muscular  tissues,  appears  to  depend 
upon  their  presence.  It  is  by  no  means  impossible  that  their  peculiar  con- 
nection with  the  activity  of  the  latter  may  be  dependent  upon  an  actual 
Chemical  relation  between  their  contents  and  the  red  matter  of  the  Ganglionic 
corpuscles  (§  245) ;  and  that  a  part  of  their  function  may  be,  to  prepare  the 
substance  which  is  afterwards  to  be  appropriated  as  a  peculiar  nutritive  prin- 
ciple, by  the  active  instruments  of  Nervous  operations.  It  appears  from  the 
experiments  of  Dieff'enbach  on  transfusion,  that  the  Red  Corpuscles  are  more 
effectual  as  stimuli  to  the  Heart's  action,  than  is  any  other  constituent  of  the 
blood.  The  rapidity  with  which  they  may  be  decomposed  and  reconstituted, 
is  made  remarkably  evident  by  the  experiments  of  Magendie;  who  found  that, 
when  the  Blood  of  one  animal  was  injected  into  the  veins  of  another  having 
discs  of  very  different  size  and  form  (care  being  taken  to  prevent  the  coagula- 
tion of  the  Fibrine  during  the  operation),  the  original  Red  particles  soon  dis- 
appeared, and  were  replaced  by  those  characteristic  of  the  species,  in  whose 
veins  the  fluid  was  circulating. — The  use  of  the  Saline  matter  is  evidently  in 
part  to  supply  the  mineral  materials,  requisite  for  the  generation  of  the  tissues, 
and  for  the  production  of  the  various  secretions.  It  is  by  the  Saline  and 
Albuminous  matters  in  conjunction,  that  the  specific  gravity  of  the  Liquor 
Sanguinis  is  kept  up  to  the  point,  at  which  it  is  equivalent  to  that  of  the  con- 
tents of  the  Red  corpuscles;  and  it  is  only  in  this  condition  that  the  latter 
present  their  proper  characters.  Thus  it  has  been  shown  by  Dr.  G.  O.  Rees, 
that  when  the  quantity  of  water  in  the  Liquor  Sanguinis  has  been  reduced  by 
copious  perspirations  or  other  similar  causes,  the  corpuscles  are  thin,  and  very 
like  those  whose  contents  have  exuded  by  exosmose  into  a  denser  liquid 
around  (§  143).  On  the  other  hand,  if  the  Liquor  Sanguinis  be  diluted  by  the 
withdrawal  of  blood  and  the  injection  of  an  equivalent  quantity  of  water,  the 
serum  speedily  becomes  tinged  with  the  colouring  matter  of  the  corpuscles ; 
apparently  in  consequence  of  a  rupture  of  some  of  the  cells,  by  endosmose 
from  the  circumambient  liquid,  now  reduced  to  a  lower  specific  gravity  than 
that  of  their  contents. — The  Fatty  matters  of  the  Blood  are  evidently  derived 
from  the  food,  either  directly,  or  by  the  transformation  of  its  farinaceous  in- 
gredients;  and  they  are  chiefly  appropriated  to  the  maintenance  of  the  com- 


COAGULATION  OF  THE  BLOOD.  531 

bustive  process.  That  which  may  be  superfluous,  is  either  deposited  in  the 
cells  of  Adipose  tissue,  or  it  is  eliminated  by  the  Liver,  the  Sebaceous  follicles 
of  the  Skin,  and  (in  the  nursing  female)  by  the  Mammary  glands.  How  the 
peculiar  Phosphorized  Fats  of  the  Blood  are  formed, — whether  by  the  con- 
tinuation of  the  azotized  and  phosphorized  materials  with  ordinary  fat,  or 
by  the  metamorphosis  of  albuminous  matter, — cannot  be  said  to  be  yet  de- 
termined. 

699.  When  the  Blood  is  drawn  from  the  body,  and  left  to  itself,  its  organic 
elements  speedily  undergo  a  new  arrangement.     The  Fibrine  coagulates,  and 
separates  itself  from  the  fluid  in  which  it  was  previously  dissolved  ;  and  during 
its  coagulation   it  attracts   the  Red  particles  ;  these  are  included  in  areolae  or 
meshes  of  the  Clot,  the  substance  of  which  has  a  tendency  to  assume  a  fibrous 
arrangement  (§  118)  ;  and  they  usually  group  themselves  together  in  columnar 
masses,  resembling  piles  of  money.   '  The  Coagulum  or  clot  becomes  dense, 
in  proportion  to  the  amount  of  the  Fibrine  it  contains  ;  and  the  Albuminous  and 
Saline  matter  still  dissolved  in  the  water  are  separated  from  it,  constituting  the 
Serum.     This   separation  will   not  occur,  however,  if  the   coagulation    take 
place  in  a  shallow  vessel ;   nor  if  the   amount  of  Fibrine  should  be  small,  or 
its  vitality  low.     A  homogeneous  mass,  deficient  in  firmness,  presents  itself 
under  such  circumstances ;  though  the  solid  part  of  this  may  pass  into  a  state 
of  more  complete  condensation,  after  the  lapse  of  a  certain  time. — That  the 
coagulation  is  due  to  the  Fibrine,  and  that  the  Red  particles  are  merely  passive 
in  the  process,  appears  from  several  considerations.     A  microscopical  exami- 
nation of  the  Clot  shows,  that  it  has   the  same   texture  with  Fibrine,  when 
coagulating  by  itself;  the  Corpuscles  clustering  together  in  the  interspaces  of 
the  network,  and  not  being  uniformly  diffused  through  the  whole  mass.     Their 
Specific  Gravity  being  greater  than  that  of  the  Fibrine,  they  are  usually  most 
abundant  at  the  lower  part  of  the   clot ;   and   the  upper  surface  is  sometimes 
nearly  colourless,  especially  when  the  coagulation  has  taken  place  slowly ;  yet 
this  upper  part  is  much  firmer  than  the  under,  showing  that  the  Fibrine  alone 
is  the  consolidating  agent. — This  has  been  proved  to   demonstration  by  an 
experiment  of  Miiller's.     He  placed  the  blood  of  a  Frog,  diluted  with  water 
(or  still  better  with  a  very  thin  syrup)  on  a  paper  filter,  of  sufficiently  fine 
texture  to  keep  back  the  Corpuscles  ;  and  the  Liquor  Sanguinis,  having  passed 
through  the  filter  completely  unmixed  with  them,  presented  a  distinct  coagu- 
lum,  although  from  the  diluted  state  of  the  fluid,  this  did  not  possess  much 
consistency.     Owing  to  the  more  minute  size  of  the  Blood-discs  of  warm- 
blooded animals,  this  experiment  cannot  be  so  readily  performed  with  their 
blood.     The  sole  agency  of  the  Fibrine  in  coagulation  is  very  easily  proved 
in  another  way.     If  fresh  drawn  blood  be  continually  stirred  with  a  stick,  the 
Fribrine  will  adhere  to  it  in  strings  during  its  coagulation  ;  and  the  Red  parti- 
cles will  be  left  suspended  in   the  serum,  without  the  slightest  tendency  to 
coagulate.     Moreover,  if  a  solution  of  any  salt,  that  has  the  property  of  re- 
tarding the  coagulation  (such  as  carbonate  of  potash  or  sulphate  of  soda),  be 
added  to  the  blood,  the  Corpuscles  will  have  time  to  sink  to  the  lower  stratum 
of  the  fluid,  before  the  clot  is   formed ;   the  greater  part  of  the  Coagulum  is 
then  entirely  colourless,  and  is  found  by  the  microscope  to  contain  few  or  no 
red  particles. 

700.  That  the  Coagulation  of  the  Blood  is  not,  as  some   have  supposed,  a 
proof  of  its  death,  but  is  rather  an  act  of  vitality,  appears  evident  from  what 
has   been  already  stated  (§  118)  of  the  incipient  organization  which  may  be 
detected  even  in  an  ordinary  clot ;  and  still  more  from  the  fact  that,  if  the 
effusion  of  Fibrine  take  place  upon  a  living  surface,  its  coagulation  is  the  first 
act  of  its  conversion  into  solid  tissues  possessing  a  high  degree  of  vitality.     It 
is  absurd  to  suppose  that  the  Blood  dies,  in  order  to  assume  a  higher  form. 


532 


OF  ABSORPTION  AND  SANGUIFICATION. 


A  complete  demonstration  of  the  truth  of  the  Hunterian  doctrine,  that  the 
Blood  might  become  organized,  like  plastic  exudations  of  "  coagulable  lymph," 
has  been  lately  afforded  by  the  researches  of  Dr.  Zwicky,  on  the  changes 
occurring  in  the  clots  of  blood  which  form  in  blood-vessels,  above  the  points 
where  they  have  been  tied.  He  has  traced  the  successive  stages  of  the  meta- 
morphosis of  the  coagulum  into  fibro-cellular  tissue,  and  the  formation  of  ves- 
sels in  its  substance ;  the  whole  process  taking  place  exactly  as  in  an  inflam- 
matory exudation,  and  the  blood-corpuscles  exerting  no  other  influence  upon 
it,  than  that  of  slightly  retarding  it. 

701.  When  the  Blood  is  withdrawn  from  the  body,  however,  its  Coagula- 
tion is  the  last  act  of  its  life  ;  for,  if  not  within  the  influence  of  a  living  sur- 
face, it  soon  passes  into  decomposition.  Instances  occasionally  present 
themselves,  in  which  the  Blood  does  not  coagulate  after  death  ;  and  in  most 
of  these,  there  has  been  some  sudden  and  violent  shock  to  the  Nervous  sys- 
tem, which  has  destroyed  the  vitality  of  solids  and  fluids  alike.  This  is 
generally  the  case  in  men  and  animals  killed  by  lightning,  or  by  strong  elec- 
tric shocks ;  and  in  those  poisoned  by  prnssic  acid,  or  whose  life  has  been 
destroyed  by  a  blow  on  the  epigastrium.  It  has  also  been  observed  in  some 
instances  of  rupture  of  the  heart,  or  of  a  large  aneurism  near  it ;  and  a  very 
interesting  phenomenon  then  not  unfrequently  presents  itself, — the  coagulation 
of  the  Blood  which  has  been  effused  into  the  pericardium  (the  effusion  having 
taken  place  during  the  last  moments  of  life),  whilst  that  in  the  vessels  has  re- 
mained fluid.  In  several  of  the  instances  in  which  the  blood  has  been  found 
uncoagulated  in  the  vessels,  many  hours  after  death,  a  portion  withdrawn  from 
the  body  has  clotted;  and  Dr.  Polli  asserts  that  the  complete  absence  of 
coagulability  is  a  phenomenon  which  has  no  real  occurrence.  During  a  long 
course  of  researches  on  this  subject,  he  has  never  yet  met  with  an  instance, 
in  which  the  blood,  when  left  to  itself,  and  duly  protected  from  external 
destructive  influences,  did  not  coagulate  before  becoming  putrid.  He  has 
even  more  than  once  caused  blood  to  coagulate,  which  had  been  taken  in  a 
fluid  state  from  the  veins,  thirty-six  or  forty-eight  hours  after  death.* — It  ap- 
pears that  simple  arrestment  of  Nervous  influence  favours  the  coagulation  of 
the  blood  in  the  vessels  ;  clots  being  found  in  their  trunks,  within  a  few 
minutes  after  the  Brain  and  Spinal  marrow  have  been  broken  down. 

702.  The  length  of  time  which  elapses  before  Coagulation,  and  the  degree 
in  which  the  clot  solidifies,  vary  considerably ;  in  general,  they  are  in  the 
inverse  proportion  to  each  other.  Thus,  if  a  large  quantity  of  blood  be  with- 
drawn from  the  vessels  of  an  animal  at  the  same  time,  or  within  short  inter- 
vals, the  portions  that  last  flow  coagulate  much  more  rapidly,  but  much  less 
firmly,  than  those  first  obtained.  In  blood  drawn  during  Inflammatory  states, 
again,  the  coagulation  is  usually  slow,  but  the  clot  is  preternaturally  firm  ;  espe- 
cially at  its  upper  part,  where  the  Buffy  coat  (§  704)  or  colourless  stratum 
of  Fibrine,  gradually  contracts,  and  produces  the  cup,  which  is  usually  re- 
garded as  indicative  of  a  high  degree  of  Inflammation.  Except  under  the 
peculiar  circumstances  just  stated,  the  Blood  withdrawn  from  the  body  always 
coagulates  ;t  whether  it  be  kept  at  rest  or  in  motion  ;  whether  its  temperature 
be  high  or  low  ;  and  whether  it  be  excluded  from  the  air,  or  be  admitted  to 
free  contact  with  the  atmosphere.  The  Coagulation  may  be  accelerated  or 
retarded,  however,  by  variation  in  these  conditions.  Thus,  if  the  blood  be 
continually  agitated  in  a  bottle,  its  coagulation  is  delayed,  though  it  will  at  last 

*  Banking's  Half- Yearly  Abstract,  vol.  ii.  p.  337. 

f  Some  diseases  may  perhaps  be  an  exception ;  non-coagulation  of  the  Blood  is  said  to  be 
characteristic  of  the  Scurvy,  but  this  is  erroneous.  In  very  severe  forms  of  Typhus,  the  same 
has  been  stated  to  occur. 


COAGULATION  OF  THE  BLOOD. BUFFY  COAT.  533 

take  place  in  shreds  or  insulated  portions ;  but  that  rest  is  not  the  cause  of  its 
coagulation  (as  some  have  supposed),  is  proved  by  the  fact  that,  if  a  portion 
of  blood  be  included  between  two  ligatures  in  a  living  vessel,  it  will  remain 
fluid  for  a  long  time.  Again,  the  coagulation  is  accelerated  by  moderate  heat, 
and  retarded  by  cold;  but  it  is  not  prevented  by  even  extreme  cold;  for,  if 
blood  be  frozen  immediately  that  it  is  drawn,  it  will  coagulate  on  being  thawed. 
Moreover  it  is  accelerated  by  exposure  to  air,  but  it  is  not  prevented  by  com- 
plete exclusion  from  it,  as  is  proved  by  its  taking  place  in  a  vacuum,  or  in  a 
shut  sac  within  the  dead  body :  complete  exclusion  from  the  air,  however, 
retards  the  change ;  as  has  been  shown  by  causing  Blood  to  flow  into  a  ves- 
sel containing  oil,  which  will  form  an  impervious  coating  on  its  surface,  and 
will  occasion  the  coagulation  to  take  place  so  slowly,  that  the  Red  particles 
have  time  to  subside,  and  the  upper  stratum  of  the  clot  is  colourless.*  A  re- 
markable case  has  been  put  on  record  by  Dr.  Polli,  in  which  complete  coagu- 
lation of  the  blood  did  not  take  place  until  fifteen  days  after  it  had  been  with- 
drawn from  the  body ;  and  fifteen  days  more  elapsed  before  putrefaction 
commenced.  The  upper  four-fifths  of  the  clot  were  colourless;  the  red  cor- 
puscles occupying  only  the  lowest  fifth.  It  is  additionally  remarkable,  that 
the  patient  (who  was  suffering  under  acute  pneumonia)  being  bled  very  fre- 
quently during  the  succeeding  week,  the  blood  gradually  lost  its  indisposition 
to  coagulate.!  An  extrication  of  Carbonic  acid  usually  takes  place  to  a  slight 
degree  during  coagulation ;  but  this  is  not  a  constant  occurrence ;  and  the 
process  is  not  prevented,  even  by  agitating  Carbonic  acid  with  the  Blood. 

703.  The  proportions  of  Serum  and  Clot  which  present  themselves  after 
coagulation,  are  liable  to  great  variation,  independently  of  the  amount  of  the 
several  ingredients  characteristic  of  each ;  for  the  Coagulum  may  include  not 
only  the  Fibrine  and  Red  particles,  but  also  a  large  proportion  of  the  Serum, 
entangled  as  it  were  in  its  substance.     This  is  particularly  the  case  when  the 
coagulation  is  rapid  ;  and  the  clot  then  expels  little  or  none  of  it  by  subse- 
quent contraction.     On  the  other  hand,  if  the  coagulation  be  slow,  the  parti- 
cles of  Fibrine  seem  to  become  more  completely  aggregated,  the  coagulum  is 
denser  at  first,  and  its  density  is  greatly  increased  by  subsequent  contraction. 
When  a  firm  fresh  clot  is  removed  from  the  fluid  in  which  it  is  immersed,  its 
concretion  is  found  to  continue  for  24  or  even  48  hours,  serum  being  squeezed 
out  in  drops  upon  its  surface;  and  in  order,  therefore,  to  form  a  proper  esti- 
mate of  the  relative  proportions  of  Crassamentum   and  Serum,  the  former 
should  be  cut  into  slices,  and  laid  upon  bibulous  paper,  that  the  latter  may  be 
pressed  from  it  as  completely  as  possible. — According  to  the  experiments  of 
Mr.  Thrackrah,  Coagulation  takes  place  sooner  in  metallic  vessels   than  in 
those  of  glass  or  earthenware,  and  the  quantity  of  Serum  separated  is  much 
less ;  in  one  instance,  the  proportion  of  Serum  to  Clot  was  as   10  to  24£, 
when  the  blood  coagulated  in  a  glass  vessel ;  whilst  a  portion  of  the  same 
Blood,  coagulating  in  a  pewter  vessel,  gave  only  10  of  Serum  to  175  of  Clot. 
The  Specific  Gravity  of  Blood  is  no  measure  of  its  coagulating  power ;  for  a 
high  specific  gravity  may  be  due  to  an  excess  in   the  amount  of  globules, 
which  form  the  heaviest  part  of  the  blood ;  and  may  be  accompanied  by  a 
diminution  in  the  quantity  of  fibrine,  which  is  the  coagulating  element. 

704.  The  Crassamentum  not  unfrequently  exhibits,  in  certain  disordered 
conditions  of  the  Blood,  a  layer  of  Fibrine  nearly  free  from  colour;  and  this  is 
known  as  the  Bvffy  Coat.     The  presence  of  this  has  been  frequently  re- 
garded as  a  sign  of  the  existence  of  Inflammation,  occasioning  an  undue  pre- 
dominance of  Fibrine ;  but  this  idea  is  far  from  being  correct,  since,  as  will  pre- 

*  Babington  in  Medico-Chirurgicnl  Transactions,  vol.  xvi. 
f  Mr.  Paget's  Report,  in  Brit,  and  For.  Med.  Rev.,  xix.p.  252. 

45* 


534 


OF  ABSORPTION  AND  SANGUIFICATION. 


Fig.  210. 


sently  appear  (§  705),  it  may  result  from  a  very  opposite  condition  of  the 
Blood.  A  similar  colourless  layer  of  Fibrine  is  always  observable,  when  the 
Coagulation  of  the  blood  is  retarded  by  the  addition  of  agents  that  have  the 
power  of  delaying  it  (§  699)  ;  and  since,  in  Inflammatory  states  of  the  system, 
the  blood  is  generally  long  in  coagulating,  it  has  been  supposed  that  the  sepa- 
ration of  the  red  particles  is  due  to  this  cause  alone.  Dr.  Alison,*  however, 
maintains  that  there  must  be  an  absolute  tendency  to  separation  between  the 
two  components  of  the  clot,  in  order  to  account  for  the  phenomena  sometimes 
presented  by  it;  and  he  adduces  the  two  following  reasons  in  support  of  this 
view.  "  1.  The  formation  of  the  Buffy  coat,  though  no  doubt  favoured  or 
rendered  more  complete  by  slow  coagulation,  is  often  observed  in  cases  where 
the  coagulation  is  more  rapid  than  usual;  and  the  colouring  matter  is  usually 
observed  to  retire  from  the  surface  of  the  fluid  in  such  cases,  before  any 
coagulation  has  commenced.  2.  The  separation  of  the  Fibrine  from  the 
colouring  matter  in  such  cases  takes  place  in  films  of  blood,  so  thin  as  not  to 
admit  of  a  stratum  of  the  one  being  laid  above  the  other;  they  separate  from 
each  other  laterally,  and  the  films  acquire  a  speckled  or  mottled  appearance, 
equally  characteristic  of  the  state  of  the  blood  with  the  buffy  coat  itself."  — 
It  appears  from  the  observations  of  Mr.  Wharton  Jones,  that  the  red  corpus- 

cles of  Inflammatory  Blood  have  an 
unusual  attraction  for  each  other,  which 
occasions  their  coalescence  in  piles  and 
masses;  so  that  by  this  character,  the 
state  of  the  Blood  may  be  detected, 
from  the  examination  of  no  more  than 
a  single  drop  of  the  fluid.  Now  if  we 
consider,  in  connection  with  this  in- 
crease in  the  mutual  attraction  of  the 
Blood-discs,  the  increase  in  the  mutual 
attraction  of  the  particles  of  Fibrine 
(which  causes  the  coagulum  of  Inflam- 
matory blood  to  be  so  much  firmer  and 
more  decidedly  fibrous  than  that  of  the 
healthy  fluid),  we  have  a  cause  suffi- 
cient to  explain  the  phenomena  noticed 
by  Dr.  Alison;  without  the  necessity 
of  resorting  to  the  idea  of  an  absolute 
repulsion  being  present  between  the  two 
constituents.  —  It  is  in  the  Buffy  Coat 
of  Inflammatory  Blood,  that  we  see 
the  clearest  indications  of  organization 
ever  presented  by  the  circulating  fluid. 
The  fibrous  network  is  frequently  extremely  distinct  ;  and  it  commonly  in- 
cludes a  large  number  of  White  Corpuscles  in  its  meshes.  Sometimes, 
indeed,  according  to  the  observations  of  Mr.  Addison,  it  almost  entirely  con- 
sists of  these  bodies.  In  its  Chemical  Composition,  the  buffy  coat  of  Inflam- 
matory blood  appears  to  be  peculiar  ;  containing  a  larger  or  smaller  amount 
of  the  substance,  readily  soluble  in  boiling  water,  which  is  considered  by 
Mulder  to  be  the  Tritoxide  of  Proteine  (§  116,  a). 

705.  When  the  Buff  arises  from  other  causes,  however,  its  appearance  is 
less  characteristic.  It  appears  from  the  researches  of  Andral,  that  the  usual 
condition  of  its  production  is  an  increase  in  the  quantity  of  Fibrine  in  propor- 
tion to  the  Red  Corpuscles;  and  not  a  simple  increase  of  Fibrine.  When  the 


The  microscopic  appearance  of  a  drop  of  blood 
in  the  inflammatory  condition.  The  red  corpus- 
cles lose  their  circular  form  and  adhere  together ; 
the  white  corpuscles  remain  apart,  and  are  more 
abundant  than  usual. 


*  Outlines  of  Physiology,  3d  edition,  p.  S9. 


BUFFY  COAT. PATHOLOGICAL  CHANGES  IN  THE  BLOOD.  535 

Blood  contains  an  excessive  quantityofFibrine.it  coagulates  slowly;  thus 
the  blood  of  a  patient  labouring  under  Rheumatism  coagulates  more  slowly 
than  that  of  one  affected  with  Typhoid  fever.  The  increase  may  occur  in. 
two  ways ; — either  by  an  absolute  increase  in  the  Fibrine,  the  amount  of  the 
corpuscles  remaining  unchanged,  or  not  being  augmented  in  the  same  pro- 
portion ; — or  by  a  diminution  of  the  Corpuscles,  the  quantity  of  Fibrine  re- 
maining the  same,  or  not  diminishing  in  the  same  proportion.  Hence  in 
severe  Chlorosis,  in  which  the  latter  condition  is  strongly  developed,  the  buffy 
coat  may  be  as  well  marked,  as  in  the  severest  Inflammation.  Unless  the 
composition  of  the  blood  be  altered  in  one  of  these  two  ways,  it  is  stated  by 
Andral  that  the  buffy  coat  is  never  formed ;  the  influence  of  circumstances 
which  favour  it,  not  being  sufficient  to  produce  it  when  acting  alone.  The 
absence  of  these  circumstances  may  prevent  it,  however,  when  it  would  other- 
wise have  been  formed ;  thus,  when  the  Blood  flows  slowly,  the  buff  is  not 
properly  produced;  because  the  slow  discharge  gives  one  portion  time  to 
coagulate  before  another;  and  only  the  blood  last  drawn  furnishes  the  Fibrine 
at  the  upper  part  of  the  vessel.  Again,  in  a  deep  narrow  vessel,  the  buff  will 
form  much  more  decidedly  than  in  a  broad  shallow  one ;  because  the  thick- 
ness of  the  Fibrinous  crust  will  be  greater. 

6. — Pathological  Changes  in  the  Blood. 

706.  From  the  part  which  the  Blood  performs  in  the  ordinary  processes  of 
Nutrition,  it  cannot  be  doubted  that  it  undergoes  important  alterations,  when 
these  processes  take  place  in  an  abnormal  manner.  These  alterations  must 
be  sometimes  the  causes,  and  sometimes  the  effects,  of  the  morbid  phenomena, 
which  constitute  what  we  term  the  Disease.  Thus,  when  some  local  cause, 
affecting  the  solid  tissues  of  a  certain  part  of  the  body,  produces  Inflammation 
in  them,  their  normal  relation  to  the  blood  is  altered ;  the  consequence  is,  that 
the  Blood,  in  passing  through  them,  undergoes  a  different  set  of  changes  from 
those  for  which  it  is  originally  adapted ;  and  thus  its  own  character  under- 
goes an  alteration,  which  soon  becomes  evident  throughout  the  whole  mass  of 
the  circulating  fluid,  and  is,  in  its  turn,  the  cause  of  morbid  phenomena  in 
remote  parts  of  the  system.  On  the  other  hand,  the  strong  analogy  between 
many  Constitutional  diseases,  and  the  effects  of  poisonous  agents  introduced 
into  the  Blood,  appears  clearly  to  point  to  the  inference,  that  these  diseases 
are  due  to  the  action  of  some  morbific  matter,  which  has  been  directly  intro- 
duced into  the  current  of  the  circulating  fluid,  and  which  has  affected  both  its 
physical  and  its  vital  properties.*  Here,  then,  is  a  wide  field  for  investiga- 
tion, of  which  the  surface  can  scarcely  be  said  to  be  yet  broken  up,  and 
which  must  yield  an  abundant  harvest  to  those  who  shall  cultivate  it  with  in- 
telligence and  zeal.  The  first  and  most  complete  series  of  connected  re- 
searches, which  have  been  yet  published,  on  the  changes  which  the  blood  un- 
dergoes in  disease,  are  those  of  MM.  Andral  and  Gavarret  ;t  these  are  confined 

*  This  doctrine  has  been  brought  prominently  forward,  in  a  paper  on  Symmetrical  Dis- 
eases, read  by  Dr.  William  Budd  before  the  Medico-Chirurgical  Society,  Dec.  16,  1841.  The 
Author  ingeniously  proves,  that  the  symmetry  of  many  diseases  (such  as  certain  forms  of 
cutaneous  eruptions,  rheumatism,  &c.)  which  do  not  immediately  depend  upon  external 
causes,  necessarily  involves  the  idea  of  the  conveyance  of  the  morbific  agent  in  the  circulating 
fluid;  the  palsy  produced  by  lead  is  a  very  interesting  example,  in  which  the  agent  is  known 
to  be  mingled  with  the  blood,  and  to  be  deposited  in  the  parts  affected,  which  are  generally, 
if  not  always,  symmetrical. 

t  An  account  of  these  inquiries  will  be  found  in  the  Provincial  Medical  and  Surgical 
Journal  for  May,  June,  and  July  1841;  in  the  Annales  des  Sciences  Naturelles,  Dec.  1840, 
and  March  1841;  and  in  the  Ann.  de  Chimie,  torn.  Ixxv.  They  have  since  been  published 


536  OF  ABSORPTION  AND  SANGUIFICATION. 

to  the  alterations  which  take  place  in  the  proportions  of  the  Organic  elements 
of  the  fluid.  Another  series  of  researches  of  great  value,  and  in  almost  every 
point  confirmatory  of  the  preceding,  has  been  since  made  by  MM.  Becquerel 
and  Rodier  ;*  and  another  by  Dr.  Karl  Popp.t  Numerous  other  less  systematic 
analyses  have  been  made  by  various  Chemists  and  Pathologists.  The  follow- 
ing outline  contains  the  general  results  of  these. — It  is,  of  course,  necessary  to 
determine, in  the  first  instance,  what  are  the  usual  or  normal  proportions;  and 
the  following  may  be  estimated  as  the  ordinary  quantity  of  each  element,  in 
1000  parts  of  healthy  Blood: — 

Fibrine from     2  to       3£ 

Corpuscles "    110   "    100 

Solid  matter  of  Serum          .         .         .         .   "      72   "      85 

707.  Before  entering  upon  the  consideration  of  the  alterations  in  the  Blood, - 
which  are  effected  by  particular  morbid  states,  it  is  requisite  to  notice  the 
results  of  two  extraneous  causes,  usually  operating  in  disease,  which  may  affect 
the  proportions  of  its  components.  These  are,  Abstinence  from  food,  and 
Loss  of  Blood,  as  by  Hemorrhage  or  Venesection.  It  has  been  commonly 
supposed,  that  these  causes  have  a  tendency  to  diminish  the  proportion  of  all 
the  solid  elements  of  the  blood;  but  this  is  not  the  case;  for  they  affect  the 
Corpuscles,  chiefly  or  exclusively,  the  quantity  of  Fibrine  and  of  the  solids  of 
the  Serum  remaining  nearly  the  same,  unless  the  abstinence  has  been  pro- 
longed, or  the  loss  of  blood  very  considerable. — It  is  probably  to  the  effects 
of  abstinence,  that  we  are  to  attribute  the  general  diminution  of  the  solids  of 
the  blood,  which  presents  itself  in  most  acute  diseases;  thus,  on  the  average 
of  120  cases,  MM.  Becquerel  and  Rodier  found  the  average  Specific  Gravity 
of  defibrinated  blood  reduced  from  1060  (in  Men)  and  1057*5  (in  Women),  to 
1056  (in  Men),  and  1055  (in  Women).  The  diminution,  in  the  proportion  of 
Corpuscles  was  well  marked;  that  of  the  Albumen  was  much  slighter;  there 
was  on  the  whole  a  slight  augmentation  of  Cholesterine  and  Phosphorized 
Fat;  and  a  marked  increase  in  the  Phosphates.  The  increase  or  diminution 
of  the  Fibrine  is  entirely  dependent  (as  we  shall  presently  see)  on  the  nature 
of  the  disease. — The  influence  of  Venesection  in  impoverishing  the  blood  is 
well  shown  in  the  following  table  of  the  mean  composition  of  the  fluid,  at  three 
successive  Venesections  in  ten  persons  : — 

First  Second  Third 

Bleeding.  Bleeding.  Bleeding. 
Specific  Gravity  of  defibrinated 

Blood 1056  1053  1049-6 

Water 793  807-7  823-1 

Fibrine 3-5  3-8  3-4 

Corpuscles 129'2  116-3  99-2 

Albumen          ....          65-0  63-7  64-6 
Extractive,  free  salts,  and  fatty 

matters 9'4  8'5  9'5 

Thus  we  see  that  repeated  venesections  render  the  blood  more  watery;  but 
this,  chiefly  by  the  diminution  they  produce  in  the  amount  of  Corpuscles. 
They  slightly  diminish  the  albumen  and  fatty  matters ;  but  they  exert  no  per- 
ceptible influence  on  the  amount  of  Fibrine; — a  point  of  the  highest  practical 
importance. 

a.  The  most  important  fact  substantiated  by  Andral,  is  one  that  had  been  previously  sus- 
pected,— the  invariable  increase  in  the  quantity  of  Fibrine  during  acute  Inflammatory  affec- 
tions;  the  increase  being  strictly  proportional  to  the  intensity  of  the  Inflammation,  and  to  the 


in  a  separate  form,  under  the  title  of  "  Essai  d'Hematologie  Pathologique.-'     [See  Transla- 
tion by  Drs.  Meigs  and  Stille,  Phil.  1844.] 

*  Gazette  Medicale,  1844,  Nos.  47 — 57.  f  Banking's  Abstract,  vol.  iii.  p.  306. 


PATHOLOGICAL  CHANGES  IN  THE  BLOOD.  537 

degree  of  symptomatic  Fever  accompanying  it.  "The  augmentation  of  the  quantity  of 
Fibrine  is  so  certain  a  sign  of  Inflammation,  that,  if  we  find  more  than  5  parts  of  fibrine  in. 
1000,  in  the  course  of  any  disease,  we  may  positively  affirm  that  some  local  inflammation 
exists."  Several  cases  are  mentioned,  in  which  an  increase  to  7  or  7^  parts  took  place, 
without  any  apparent  cause;  but.in  which  it  afterwards  proved  that  severe  local  inflamma- 
tion was  present;  and  thus  we  are  furnished  with  a  pathognomonic  sign  of  great  importance. 
The  average  proportion  of  Fibrine  in  Inflammation  may  be  estimated  at  7;  the  minimum 
at  5;  the  maximum  at  13*3.  The  greatest  augmentation  is  seen  in  Pneumonia  and  Acute 
Rheumatism.  It  does  not  appear  that  in  robust  athletic  persons,  the  proportion  of  Fibrine  is 
greater  than  in  those  of  feeble  constit\ition ;  in  the  latter  it  is  the  Corpuscles  that  are  deficient; 
and  it  is  rather  from  this  disproportion,  than  from  an  absolute  excess  of  Fibrine,  that  their 
greater  liability  to  Inflammatory  affections  arises.  Diseases  which  commence  at  the  same 
time  as  the  Inflammation,  or  co-exist  with  it,  do  not  prevent  the  characteristic  increase  of  the 
Fibrine;  thus  in  Chlorotic  females,  the  proportion  rises  to  6  or  7,  under  this  influence.  The 
augmentation  is  observed  at  the  very  outset  of  the  affection ;  the  quantity  increases  with  its 
progress;  and  a  decrease  shows  itself  when  the  disease  begins  to  abate.*  When  the  dis- 
ease presents  alternations  of  increase  and  decline,  these  are  marked  by  precisely  correspond- 
ing changes  in  the  quantity  of  Fibrine.  It  is  a  curious  fact,  that  an  augmentation  is  commonly 
observable  during  the  advanced  stage  of  Phthisis,  in  spite  of  the  deterioration  which  the 
blood  must  then  have  undergone;  this  is  probably  dependent  upon  the  development  of  local 
inflammation  around  the  tubercular  deposits.  In  one  of  Popp's  observations,  the  proportion 
of  Fibrine  in  the  blood  of  a  Phthisical  patient  was  not  less  than  10-7.  Some  experiments 
performed  by  M.  Andral  on  the  blood  of  pregnant  women,  seem  to  lead  to  the  conclusion 
that,  during  the  first  six  months,  the  Fibrine  is  below  the  normal  standard ;  and  that  it  sub- 
sequently varies,  usually  undergoing  an  augmentation  between  the  sixth  and  seventh,  and 
the  eighth  and  ninth  months.  There  is  also  a  diminution  in  the  Corpuscles;  and  these  circum- 
stances combined  favour  the  production  of  the  buffy  coat  (§  704).  These  observations  are 
confirmed  by  those  of  MM.  Becquerel  and  Rodier. 

b.  It  appears  obvious,  from  what  has  been  just  stated,  that  the  increase  in  the  quantity  of 
Fibrine  is  not  dependent  upon  the  febrile  condition,  which  is  secondary  to  the  local  inflamma- 
tion, but  upon  the  Inflammation  itself.  This  conclusion  is  confirmed  by  the  interesting  fact 
that,  in  idiopathic  Fever,  the  proportion  of  Fibrine  is  diminished,  instead  of  undergoing  an 
increase.  This  diminution  was  constantly  observed  by  Andral  in  the  premonitory  stage  of 
Continued  Fever;  in  some  instances  the  amount  was  no  more  than  T6  parts  in  1000.  The 
proportion  of  Corpuscles  was  found  to  have  usually,  but  not  constantly,  undergone  an  increase ; 
as  had  also  that  of  the  solid  parts  of  the  Serum.  In  ordinary  Continued  Fever,  in  which 
there  was  no  evident  complication  from  local  disease,  the  quantity  of  Fibrin  varied  from  4-2 
to  2-2;  that  of  the  Corpuscles  from  185-1  to  103-6  (excluding  a  case  in  which  their  amount 
was  only  82-5,  which  was  that  of  a  Chlorotic  female);  that  of  the  solid  matter  of  the  Serum, 
from  98-7  to  90'9;  and  that  of  the  Water  from  725-6  to  851-9.  Hence  the  quantity  of  solid 
matter  appears  to  be  usually  increased ;  but  the  peculiar  condition  of  the  disease  may  proba- 
bly be  stated  to  be,  an  increase  in  the  proportion  of  the  Corpuscles  to  the  Fibrine.  When, 
however,  a  local  Inflammatory  affection  developes  itself  during  the  course  of  the  Fever,  the 
amount  of  Fibrine  increases;  but  its  augmentation  seems  to  be  kept  down  by  the  febrile 
condition. — In  Typhoid  Fever,"}"  the  decrease  in  the  proportion  of  Fibrine  is  much  more  de- 
cidedly marked;  this  does  not  depend  upon  abstinence;  for  it  ceases  as  soon  as  a  favourable 
change  occurs  in  the  disease,  long  before  the  effect  of  food  could  show  itself.  In  the  various 
cases  examined  by  Andral,  the  blood  furnished  a  maximum  of  3-7  of  Fibrine,  and  a  minimum 
of  0'9;  in  this  last  case,  the  Typhoid  condition  existed  in  extreme  intensity,  yet  the  patient 
recovered.  The  proportion  of  Corpuscles  varies  considerably;  in  an  early  stage  of  the  disease 
it  is  usually  found  to  be  absolutely  high ;  and  it  always  remains  high  relatively  to  the  amount 
of  Fibrine.  In  Typhoid  fever,  then,  the  abnormal  condition  of  the  Blood,  in  regard  to  the 


*  By  experiments  on  animals,  M.  Andral  has  ascertained  that  no  circumstance  of  pre- 
vious debility  or  privation  prevents  this  characteristic  change.  Having  ascertained  the 
amount  of  Fibrine  in  the  blood  of  three  dogs  to  be  2-3,  2'2,  and  1-8  (the  natural  range  for 
these  animals),  he  deprived  them,  completely  or  partially,  of  food.  On  the  fourteenth  day, 
the  proportion  of  fibrine  had  risen,  in  the  first  to  4-5 :  and  in  the  second,  to  4 :  these  animals 
had  no  food.  In  the  third  dog,  which  was  supplied  with  a  very  small  quantity  of  food 
daily,  the  same  condition  developed  itself  at  a  later  period ;  the  blood  on  the  fourteenth  day 
exhibiting  only  1'8  parts  of  fibrine:  but  on  the  twenty-second  day  presenting  3-3  parts — -In 
all  these  instances,  the  elevation  in  the  proportion  of  Fibrine  was  coincident  with  Inflamma- 
tory changes  in  the  stomach. 

f  M.  Andral  confines  this  term  to  the  species  characterized  by  ulceration  of  the  mucous 
follicles  of  the  intestinal  canal. 


538  OF   ABSORPTION  AND  SANGUIFICATION. 

disproportion  between  the  Corpuscles  and  the  Fibrine,  is  more  strongly  marked  than  in  ordi- 
nary Continued  Fever :  yet  the  usual  augmentation  of  Fibrine  will  take  place,  if  a  local  in- 
flammation developes  itself. — In  the  Eruptive  Fevers,  it  does  not  appear  that  the  proportion 
between  the  Fibrine  and  the  Corpuscles  undergoes  so  striking  a  change,  as  in  ordinary  Con- 
tinued Fever;  but  the  number  of  cases  examined  was  too-small  to  admit  of  decided  conclu- 
sions. It  was  evident,  however,  that  the  specific  Inflammations  proper  to,  and  characteristic 
of,  these  Fevers,  have  not  the  same  effect  in  occasioning  an  increase  of  the  Fibrine,  as  an 
intercurrent  Inflammation  of  an  extraneous  character. — By  the  experiments  of  Magendie  it 
has  been  ascertained  that  one  of  the  effects  of  a  diminution  in  the  proportion  of  Fibrine,  is  a 
tendency  to  the  occurrence  of  Hemorrhage  or  of  Congestion,  either  in  the  parenchymatous 
tissue,  or  on  the  surface  of  membranes :  these  conditions  are  well  known  to  be  of  frequent 
occurrence,  as  complications  of  febrile  disorders.  A  marked  diminution  of  Fibrine  was 
noticed  also  in  many  cases  of  the  disorder  termed  Cerebral  Congestion,  which  commences 
with  headache,  vertigo,  and  tendency  to  epistaxis,  and  not  unfrequently  passes  into  coma 
and  apoplexy.  In  Apoplexy,  the  diminution  of  Fibrine  was  still  more  striking ;  and  in  gene- 
ral, there  was  found  to  be  an  increase  of  the  Corpuscles.  In  one  instance,  the  quantity  of 
Fibrine  on  the  second  day  of  the  attack  was  found  to  have  fallen  to  1-9,  whilst  that  of  the 
Corpuscles  had  risen  to  175'5;  but  on  the  third  day,  when  the  patient's  consciousness  began 
to  return  the  quantity  of  Fibrine  was  3'5,  whilst  that  of  the  Corpuscles  had  fallen  to  ]  37  7. 
It  would  seem  from  the  great  change  in  the  character  of  the  Blood,  which  was  noticed  in 
this  and  in  other  instances,  that  the  want  of  due  proportion  between  the  Fibrine  and  the 
Corpuscles  was  the  cause,  rather  than  the  effect,  of  the  Apoplectic  attack. 

c.  The  amount  of  Red  Corpuscles  seems  to  be  subject  to  greater  variation  within  the  limits 
of  ordinary  health,  than  is  that  of  Fibrine.     In  the  condition  which  is  ordinarily  termed  a 
highly  sanguineous  temperament,  or  Plethora,  it  is  chiefly  the  entire  mass  of  the  blood  that 
undergoes  an  increase ;  but  whatever  excess  there  may  be  in  the  proportion  of  its  solid  con- 
stituents, affects  the  Corpuscles  rather  than  the  Fibrine.     Plethoric  persons  are  not  more 
prone  to  Inflammation,  than  are  those  of  weaker  constitution ;  but  they  are  liable  to  Conges- 
tion, especially  of  the  brain,  and  to  Apoplexy  or  other  Hemorrhage.     The  effect  of  Bleeding 
in  diminishing  this  tendency  is  now  intelligible;  since  we  know  that  loss  of  blood  reduces 
the  proportion  of  Corpuscles. — On  the  other  hand,  in  that  temperament,*  which,  when  ex- 
aggerated, becomes  Anaemia,  there  is  a  marked  diminution  of  the  Corpuscles;  this  tempera- 
ment may  lead  to  two  different  conditions  of  the  system.     In  Chlorosis,  the  Red  Corpuscles 
are  diminished,  whilst  the  Fibrine  remains  the  same;  so  that  the  clot,  though  small,  is  firm, 
and  not  unfrequently  exhibits  the  bufty  coat;  in  some  extreme  cases  of  this  disease,  the  Cor- 
puscles have  been  found  as  low  as  27.     The  influence  of  the  remedial  administration  of 
Iron,  in  increasing  the  quantity  of  Corpuscles,  was  rendered  extremely  perceptible  by  An- 
dral's  analyses;  in  one  instance,  after  iron  had  been  taken  for  a  short  time,  the  proportion 
of  Corpuscles  was  found  to  have  risen  from  49-7  to  64'3  ;  whilst  in  another,  in  which  it  had 
been  longer  continued,  it  had  risen  from  46'6  to  95*7.     On  the  other  hand,  Bleeding  reduced 
still  lower  the  proportion  of  Corpuscles ;  thus  in  one  instance,  their  amount  was  found,  on  a 
second  bleeding,  to  have  sunk  from  62*8  to  49.     The  full  proportion  of  Fibrine  in  the  blood 
of  Chlorotic  patients  accounts  for  the  infrequency  of  Hemorrhage  in  them ;   whilst  it  also 
leads  us  to  perceive  that  they  may  be,  equally  with  others,  the  subjects  of  acute  Inflamma- 
tion, which  we  know  to  be  the  fact.     A  diminution  of  Corpuscles  may  also  co-exist  with  a 
diminution  in  the  amount,  or  in  the  degree  of  elaboration,  of  the  Fibrine;  and  this  condition 
seems  to  be  characteristic  of  Scrofula.     Andral  has  noticed  a  diminution  in  the  proportion  of 
Corpuscles  in  other  Cachectic  states,  resulting  from  the  influence  of  various  depressing  causes 
on  the  nutritive  powers ;  as  in  the  case  of  Diabetes  Mellitus,  in  which  the  patient  was  much 
exhausted; — a  case  of  Aneurismal  dilatation  of  the  Heart  inducing  Dropsy; — and  in  several 
cases  of  Cachexia  Saturnina. — The  increase  in  the  proportion  of  Colourless  Corpuscles,  in 
Inflammatory  affections,  has  been  particularly  noticed  by  Popp ;  he  has  found  them  espe- 
cially abundant  in  Pneumonia  and  in  Phthisis, — in  the  former  of  which  diseases  the  Fibrine 
is  invariably,  and  in  the  latter  generally,  increased. 

d.  The  chief  class  of  cases,  in  which  any  marked  change  has  been  observed  in  the 
amount  of  solid  matter  in  the  Serum,  is  that  of  Albuminuria,  or  Bright's  disease  of  the  Kid- 
ney.    The  diminished  Specific  Gravity  of  the  Serum  was  long  ago  pointed  out  by  Dr.  Christi- 
son;  but  Andral  remarks  that  this  is  not  an  accurate  criterion,  since,  if  there  be  a  diminished 
amount  of  Corpuscles  (as  is  not  unfrequently  the  case  in  this  disease),  the  proportion  of 
water  in  the  whole  will  be  increased,  and  the  specific  gravity  of  the  serum  thus  lowered, 
without  any  alteration  in  its  proper  quantity  of  solid  matter.     According  to  Andral,  the 
diminution  in  the  amount  of  Albumen  in  the  Serum  is  exactly  proportional  to  the  quantity 


*  The  term  lymphatic  has  been  applied  to  this  temperament;  by  which  term  was  meant 
a  predominance  of  lymph  in  the  absorbent  vessels. 


PATHOLOGICAL  CHANGES  IN  THE  BLOOD.  539 

contained  in  the  urine.  A  case  is  related  by  him,  under  this  head,  which  affords  an  interest- 
ing exemplification  of  the  general  facts  that  have  been  already  attained  by  his  investigations. 
A  woman  who  had  been  suffering  from  Erysipelas  of  the  face,  and  who  had  lost  blood  both 
by  venesection  and  by  leeches,  became  the  subject  of  Albuminuria.  The  blood  drawn  at 
this  time  exhibited  a  considerable  diminution  in  the  proportion  of  Corpuscles,  as  well  as  of 
Albumen, — a  fact  which  the  previous  loss  of  blood  fully  accounted  for.  After  a  short  period, 
during  which  she  had  been  allowed  a  fuller  diet,  another  experimental  bleeding  exhibited 
an  increase  in  the  proportion  of  Corpuscles.  Some  time  afterwards,  when  the  Albumen  had 
disappeared  from  the  Urine,  some  more  blood  was  drawn ;  and  it  was  then  observed  that 
the  Albumen  of  the  Serum  had  returned  to  its  due  proportion,  but  that  the  Corpuscles  had 
again  diminished,  whilst  there  was  a  marked  increase  in  the  quantity  of  Fibrine.  This  altera- 
tion was  fully  accounted  for  by  the  fact,  that,  in  the  interval,  several  Lymphatic  ganglia  in 
the  neck  had  been  inflamed  and  had  suppurated;  and  that  the  patient  had  been  again  placed: 
on  very  low  diet.  "Thus,"  observes  Andral,  "we  were  enabled  to  give  a  complete  explana- 
tion of  the  remarkable  oscillations  which  were  presented,  in  the  proportion  of  the  different 
elements  of  the  blood  drawn  at  three  different  times  from  the  same  individual;  and  thus  it 
is  that,  the  more  extended  are  our  inquiries,  the  more  easy  does  it  become  to  refer  to  general 
principles  the  causes  of  all  those  changes  in  the  composition  of  the  blood,  which,  from  the 
frequency  and  rapidity  with  which  they  occur,  seem  at  first  sight  to  baffle  all  rules,  and  to 
take  place,  as  it  were,  at  random.  In  the  midst  of  this  apparent  disorder,  there  is  but  the 
fulfilment  of  laws ;  and  in  order  to  obtain  these,  it  is  only  necessary  to  strip  the  phenomena 
of  their  complications,  and  to  reduce  them  to  their  simplest  form." 

708.  That  the  Blood  is  subject  to  a  great  variety  of  other  morbid  altera- 
tions, which  are  sometimes  the  causes,  and  sometimes  the  results,  of  Disease, 
cannot  be  for  a  moment  doubted.  But  our  knowledge  of  the  nature  of  these 
changes  is  as  yet  very  insufficient.  The  great  amount  of  attention  which  is 
being  directed  by  Chemical  Pathologists  to  the  subject,  however,  will  doubt- 
less ere  long  produce  some  important  results. — Among  the  most  frequent 
causes  of  depravation  in  the  character  of  this  fluid,  we  must  undoubtedly  rank 
the  retention,  in  the  Circulating  current,  of  matters  which  ought  to  be  re- 
moved by  the  Excreting  processes.  We  shall  presently  see,  that  a  total 
interruption  to  the  excretion  of  Carbonic  Acid  by  the  lungs,  will  occasion 
death  in  the  course  of  a  very  few  minutes ;  and  even  when  only  a  slight  im- 
pediment is  offered  it,  so  that  the  quantity  of  Carbonic  Acid  always  contained 
in  arterial  blood  is  augmented  to.  but  a  small  degree,  a  feeling  of  discomfort 
and  oppression,  increasing  with  the  duration  of  the  interruption,  is  speedily 
produced.  The  results  of  the  retention  of  the  materials  of  the  Biliary  and 
Urinary  excretions  will  be  hereafter  considered  (Chap,  xv.) ;  and  at  present 
it  will  be  only  remarked,  that  such  retention  is  a  most  fertile  source  of  slight 
disorders  of  the  system,  that  it  is  largely  concerned  in  producing  many  severe 
diseases,  and  that  if  complete  it  will  most  certainly  and  rapidly  produce  a 
fatal  result. — The  most  remarkable  cases  of  depravation  of  the  Blood,  by  the 
introduction  of  matters  from  without,  are  those  in  which  these  substances  act 
as  ferments?— exciting  such  Chemical  changes  in  the  constitution  of  the  fluid, 
that  its  whole  character  is  speedily  changed,  and  its  vital  properties  are  alto- 
gether destroyed.  Of  such  an  occurrence,  we  have  characteristic  examples  in 
the  severe  forms  of  Typhoid  fever,  commonly  termed  malignant;  in  Plague, 
Glanders,  Pustule  Maligne,  and  several  other  diseases;  in  some  of  uijhich  we 
can  trace  the  direct  introduction  of  the  poison  into  the  blood,  whilst  in  others 
we  must  infer  from  the  similarity  of  result)  that  it  has  been  introduced  through 
some  obscure  channel, — probably  the  lungs.  The  final  symptoms  which  are 
common  to  all  these  diseases  have  been  well  described  by  Dr.  Williams,* 
under  the  title  of  Necrcemia,  or  Death  by  depravation  of  the  blood.  "  Almost 
simultaneously,  the  heart  loses  its  power,  the  pulse  becomes  very  weak, 
frequent,  and  unsteady :  the  vessels  lose  their  tone,  especially  the  capil- 
laries of  the  most  vascular  organs,  and  congestions  occur  to  a  great  amount; 

*  Principles  of  Medicine,  [Am.  Ed.  by  Dr.  Clymer,  p.  373.] 


540  OF  THE  CIRCULATION  OF  BLOOD. 

the  brain  becomes  inactive,  and  stupor  ensues ;  the  medulla  is  torpid,  and  the 
powers  of  respiration  and  excretion  are  imperfect:  voluntary  motion  is  almost 
suspended  ;  secretions  fail ;  molecular  nutrition  ceases ;  and  at  a  rate  much 
more  early  than  in  other  modes  of  death,  molecular  death  follows  close  on 
somatic  death, — that  is,  structures  die  and  begin  to  run  into  decomposition  as 
soon  as  the  pulse  and  breath  have  ceased  ;  nay,  a  partial  change  of  this  kind 
may  even  precede  the  death  of  the  whole  body ;  and  parts  running  into  gan- 
grene, as  in  the  carbuncle  of  plague,  the  sphacelous  throat  of  malignant  scarla- 
tina, and  the  sloughy  sores  of  the  worst  forms  of  typhus,  pr  the  putrid  odour 
exhaled  even  before  death  by  the  bodies  of  those  who  are  the  victims  of  simi- 
lar pestilential  disease,  are  so  many  proofs  of  the  early  triumph  of  dead  over 
vital  chemistry." — "The  appearance  of  petechiae  and  vibices  on  the  external 
surface,  the  occurrence  of  more  extensive  hemorrhage  in  internal  parts,  the 
general  fluidity  of  the  blood,  and  frequently  its  unusually  dark  or  otherwise 
altered  aspect,  its  poisonous  properties  as  exhibited  in  its  deleterious  operation 
on  other  animals,  and  its  proneness  to  pass  into  decomposition,  point  out  the 
Blood  as  the  first  seat  of  disorder;  and  by  the  failure  of  its  natural  properties 
and  offices  as  the  vivifier  of  all  structure  and  function,  it  is  plainly  the  medium 
by  which  death  begins  in  the  body." 


CHAPTER    XII. 

OF  THE  CIRCULATION  OF  BLOOD. 

1. — Of  the  Circulation  in  General. 

709.  THE  Circulation  of  nutritive  fluid  through  the  body  has  for  its  object, 
on  the  one  part,  to  convey  to  every  portion  of  the  organism  the  materials  for 
its  growth  and  renovation,  together  with  the  supply  of  Oxygen  which  is  re- 
quisite for  its  vital  actions,  especially  those  of  the  Muscular  and  Nervous 
systems  ;  and  at  the  same  time  to  carry  off  the  particles,  which  are  set  free  by 
the  disintegration  or  waste  of  the  tissues,  and  which  are  to  be  removed  from 
the  body  by  the  Excreting  processes.  Of  these  processes,  the  one  most  con- 
stantly in  operation,  as  well  as  most  necessary  for  the  maintenance  of  the 
purity  of  the  blood,  is  the  extrication  of  Carbonic  acid,  through  the  Respira- 
tory organs;  and  this  is  made  subservient  to  the  introduction  of  Oxygen  into 
the  system.  The  extent,  therefore,  to  which  a  Circulating  apparatus  is  de- 
veloped in  the  Animal  kingdom,  is  partly  dependent  upon  the  degree  in  which 
the  function  of  nutritive  Absorption  is  limited  to  one  part  of  the  body;  and 
partly  upon  the  arrangement  of  the  Excreting  surfaces,  and  especially  of  the 
Respiratory  apparatus.  Where  the  Digestive  cavity  extends  itself  through 
the  whole  system,  so  that  every  part  can  absorb  at  once  from  its  parietes,— 
and  where  the  whole  external  surface  is  adapted,  by  its  softness  and  permeability, 
to  expose  the  fluids  of  the  body  to  the  aerating  medium  around, — there  is  no 
necessity  for  any  transmission  of  fluid  from  one  part  to  another ;  and  accord- 
ingly, in  the  lowest  animals,  which  are  thus  formed,  no  true  Circulation  exists. 
Again,  in  the  Insect  tribes,  in  whose  bodies  the  absorption  of  fluids  can  only 
take  place  at  fixed  points,  there  is  a  Circulation,  for  the  purpose  of  transmit- 
ting the  absorbed  matter  to  the  remote  portions  of  the  body ;  but  as  every  part 
of  the  interior  is  permeated  by  air,  the  second  of  the  above-named  purposes 


OF  THE  CIRCULATION  IN  GENERAL. 


541 


is  already  answered ;  and  the  circuit  of  the  blood  through  the  vessels,  there- 
fore, is  not  accomplished  with  the  energy  and  activity  which,  from  the  vigor- 
ous movements  performed  by  these  little  beings,  might  have  been  supposed 
necessary.  On  the  other  hand,  among  the  Mollusca,  in  which  the  absorption 
of  fluid  and  the  respiratory  action  are  alike  limited,  we  find  the  circulating 
apparatus  almost  as  extensive,  and  the  movement  of  blood  as  vigorous,  as  it  is 
in  the  lower  Vertebrata.  It  is  in  those  animals,  in  which  there  is  the  greatest 
activity  in  the  other  functions,- — which  live,  in  fact,  the  fastest, — that  the  Cir- 
culation is  most  energetic ;  thus  the  rapid  and  energetic  movement  of  the 
blood  in  Birds  contrasts  most  strongly  with  its  slow  and  feeble  propulsion  in 
Reptiles.  The  movement  may  vary  considerably,  however,  in  the  same  ani- 
mal at  different  times,  according  to  its  state  of  repose  or  activity ;  and  in  dif- 
ferent organs  of  the  same  animal,  according  to  the  energy  with  which  their 
functions  are  being  respectively  performed. 

710.  In  Man,  as  in  other  Vertebrated  animals,  there  is  a  regular  and  con- 
tinuous movement  of  the  nutritive  fluid  through  the  vascular  system ;  and  upon 
the  maintenance  of  this,  the  activity  of  all  parts  of  the  organism  is  dependent. 
The  course  of  the  Blood  may  be  likened  to  the  figure  8 ;  for  there  are  two 
distinct  circles  of  vessels,  through  which  it  is  transmitted ;  and  the  Heart  is 
placed  at  the  junction  of  these.  The  Systemic  and  Pulmonary  circulations 
are  entirely  separate,  and  might  be  said  to  have  distinct  hearts ;  for  the  left 
and  right  sides  of  the  heart,  which  are  respectively  appropriated  to  these, 
have  no  direct  communication  with  each  other  (in  the  perfect  adult  condition, 
at  least),  and  are  merely  brought  together  for  economy  of  material.  At  an 
early  period  of  foetal  life,  as  in  the  permanent  state  of  the  Dugong,  the  heart  is 
so  deeply  cleft,  from  the  apex  towards  the  base,  as  almost  to  give  the  idea  of 
two  separate  organs.  Each  system  has  its  own  set  of  Arteries  or  efferent 
vessels,  and  Veins  or  afferent  trunks ;  these  communicate  at  their  central  ex- 
tremity by  the  Heart ;  and  at  their  peripheral  extremity  by  the  Capillary  ves- 
sels, which  are  nothing  else  than  the  minutest  ramifications  of  the  two  systems, 
inosculating  into  a  plexus  (§  219). 

Fig.  211. 


Web  of  Frog's  foot,  stretching  between  two  toes,  magnified  3  diam. ;  showing  the  blood-vessels,  and 
their  anastomoses :  1, 1,  veins;  2,  2,  2,  arteries. 

46 


542 


OF  THE  CIRCULATION  OF  BLOOD. 


a.  Although  the  diameters  of  the  branches,  at  each  subdivision,  together  exceed  that  of 
the  trunk,  yet  there  is  but  little  real  difference  in  their  size.  For,  according  to  a  well-known 
geometrical  law,  the  areas  of  circles  are  as  the  squares  of  their  diameters  ;  and,  as  the  calibre 
of  a  tube  is  estimated  by  its  area,  not  by  its  diameter,  it  follows  that,  in  comparing  the  size 
of  a  trunk  with  that  of  its  branches,  we  are  to  square  the  diameter  of  the  former,  and  com- 
pare the  result  with  the  sum  of  the  squares  of  the  diameters  of  the  branches.  When  this  is 
done,  there  is  found  to  be  a  very  close  correspondence.  The  following  table  gives  the  re- 
sult of  eight  measurements,  taken  with  a  view  to  determine  the  question.  The  first  three 
were  taken  from  the  mesenteric  artery  of  a  Sheep  5  the  next  three  from  the  aorta  and  iliac 
arteries :  the  last  two  from  the  Horse.* 


TRUNK. 

DIAMETER. 

I. 

9 

II. 

7.2 

III. 

3.5 

IV. 

7.0 

V. 

17 

VI. 

10 

VII. 

4.5 

VIII. 

8 

sq.tr  ARE. 

81 

51.64 
12.25 

49 
289 
100 
20.25 

64 


BRANCHES. 


DIAMETERS. 
7.5+5 

6+4 
3+2 
5+5 

10+10+9.5 

7+7+2 

3.5+3 

4+7 


SUM    OF    SQ.tr ARES. 

81.25 

52 

13 

50 
290.25 

102 
21.25 

65 


The  discrepancy  between  the  two  results  must  be  considered  extremely  small,  when  it  is 
stated  that  the  unit,  in  the  above  measurements,  is  no  more  than  one-fortieth  of  an  inch; 
and  when  it  is  remembered  that  any  error  in  the  measurement  is  greatly  increased  in  the 
calculation. 

b.  From  Mr.  Paget's  observations,  however,  it  appears  that  there  is  seldom  an  exact 
equality  between  the  area  of  the  trunk  and  that  of  its  branches,  but  the  area  sometimes  in- 
creases, and  sometimes  diminishes; — the  former  being  the  general  rule  for  the  subdivision 
of  the  aorta  and  its  principal  branches  in  the  upper  extremities; — the  latter  in  the  lower. 
The  following  Table  shows  the  relative  areas  of  several  arterial  trunks,  and  of  the  branches 
proceeding  from  them. 


Arch  of  Aorta         .... 
Innominata         ..... 
Common  carotid,     .... 
External  carotid          .... 

Subclavian 

Abdominal  Aorta,  to  last  lumbar  art. 

,  just  before  dividing 

Common  Iliac 

External  Iliac 


TRUNK. 
1 
1 

1 
1 
1 
1 
1 
1 
1 


BRANCHES. 

1-055 

1-147 

1-013 

1-190 

1-055 

1-183 

•893 

•982 

1-150 


711.  That  the  movement  of  the  Blood  through  the  Arterial  trunks  and  the 
Capillary  tubes  is,  in  Man,  and  in  other  warm-blooded  animals,  chiefly  de- 
pendent upon  the  action  of  the  Heart  there  can  be  no  doubt  whatever.  It  can 
be  easily  shown  by  experiment,  that,  if  the  Arterial  current  be  checked,  the 
Capillaries  will  immediately  cease  almost  entirely  to  deliver  the  blood  into 
the  veins,  and  the  Venous  circulation  will  be  instantaneously  arrested.  And 
it  has  also  been  proved,  that  the  usual  force  of  the  Heart  is  sufficient  to  propel 
the  blood,  not  only  through  the  Arterial  tubes,  but  through  the  Capillaries, 
into  the  Veins ;  since  even  a  less  force  will  serve  to  propel  warm  water  through 
the  vessels  of  an  animal  recently  dead.t  But  there  are  certain  "residual  phe- 
nomena" even  in  Man,  which  clearly  indicate  that  this  is  not  the  whole  truth  ; 
and  that  forces  existing  in  the  Blood-vessels  have  a  considerable  influence,  in 
producing  both  local  and  general  modifications  of  the  effects  of  the  Heart's 
action.  There  are  also  indications  of  the  nature  of  an  influence,  in  which  the 
blood-vessels  do  not  partake,  arising  from  those  changes  occurring  between 
the  Blood  and  the  Tissues,  that  constitue  the  processes  of  Nutrition,  Secretion, 

*  Ferneley  in  Medical  Gazette,  Dec.  7,  1839. 

|  See  Dr.  Williams'  Principles  of  Medicine,  p.  143,  note. 


MOTION  OF  THE  BLOOD  IN  THE  VESSELS.  543 

<fcc.  Such,  for  instance,  would  appear  to  be  the  interpretation  of  the  fact, 
that  whilst  any  variations  in  the  action  of  the  Heart  affect  the  whole  system 
alike,  there  are  many  variations  in  the  Circulation,  which,  being  very  limited 
in  their  extent,  cannot  be  attributed  to  such  central  disturbances,  and  must 
therefore  be  dependent  on  causes  purely  local. — Of  the  nature  of  these  in- 
fluences, and  of  the  mode  of  their  operation,  we  shall  probably  arrive  at  a 
more  correct  knowledge,  if  we  examine  the  phenomena  of  the  Circulation  in 
those  beings,  in  which  the  moving  power  is  less  concentrated  than  it  is  in  the 
higher  Animals ;  for  just  as  we  find  in  the  latter,  that  the  development  of 
special  absorbent  vessels  does  not  exclude  the  function  of  absorption  from 
being  still  performed  by  the  general  vascular  system  (§  675),  so  may  we  here 
be  led  to  perceive,  that  there  is  a  generally-diffused  force,  to  which  alone  the 
Circulation  of  the  nutritious  fluid  in  the  lowest  organisms  is  due,  and  which 
is  not  altogether  replaced  by  the  special  organ  of  impulsion,  that  is  developed 
in  the  centre  of  the  system  in  the  higher. 

712.  The  ascent  of  the  sap  in  Vegetables  is  probably  to  be  regarded  as  due, 
in  part,  to  the  vis  a  tergo  occasioned  by  the  action   of  Endosmose  at  the 
roots;  and  in  part,  to  the  demand  for  fluid,  occasioned  by  the  vital  processes 
taking  place  in  the  leaves.     For  if  the  stem  of  the  Vine,  in  which  the  sap  is 
rising,  be  cut  across,  the  sap  will  continue  to  flow  for  some  time  from  the  top 
of  the  lower  portion ;  and  its  force  of  ascent  may  be  shown  to  be  very  con- 
siderable, by  tying  over  the  cut  surface  a  piece  of  bladder,  which  will  be 
speedily  burst, — or  by  affixing  to  it  a  bent  tube,  containing  a  column  of  mer- 
cury, which  will  be  raised  to   the  height  of  forty  inches  or  more.     On  the 
other  hand,  the  attractive  force  of  the  leaves  is  shown  by  the  fact,  that  if  the 
lower  end  of  the  upper  division  be  put  into  water,  it  will  continue  to  absorb, 
as  long  as  the  vital  actions  of  the  leaves  are  being  performed  with  vigour; 
but,  if  the  branch  be  carried  into  a  dark  room,  the  exhalation  from  the  leaves 
is  immediately  checked,  and  absorption  is  checked  also.     The  influence  of 
the  actions  at  the  periphery  of  the  circulating  system,  in  maintaining  the  flow 
of  fluid  towards  the  part,  is  further  shown  by  the  fact,  that,  if  a  shoot  of  an 
evergreen  species  be  grafted  on  a  stock  of  one  with  deciduous  leaves,  a  con- 
tinual and  unwonted  ascent  of  sap  will  be  kept  up  in  the  latter  through  the 
winter;  this  being  evidently  due  to  the  demand  occasioned  at  its  summit. 
Again,  the  recommencement  of  the  annual  flow  of  sap  in  an  ordinary  tree,  has 
been  found  to   take   place  in  the  first  instance,  not  at  its  roots,  but  in  the 
neighbourhood  of  the  buds ;  for  their  expansion,  under  the  influence  of  the 
returning  warmth,  exhausts  the  fluid  from  the  vessels  of  their  neighbourhood; 
this,  again,  occasions  a  demand  from  below;  and  thus  the  motion  is  gradually 
propagated  to  the  roots.     Now  it  has  been  experimentally  ascertained,  that  if 
a  branch  of  a  vine  growing  in  the  open  air  be  trained  into  a  hot-house,  it  may 
be   made  to  vegetate  during  the  winter,  and   to  draw  up  fluid  through  the 
stems  and  roots,  whose  condition  has  not  been  changed.     It  is  evident,  then, 
that  in  Plants,  the  demand  for  fluid,  in  the  organs  to  which  it  is  distributed  by 
the  vascular  system,  is  one  of  the  chief  forces  by  which  the  supply  is  obtained. 

713.  This  is  still  more  evidently  the  case,  in  regard  to  the  Circulation  of 
nutritious  or  elaborated  sap,  which  takes  place  in  the  under  surface  of  the 
leaves  and  in  the  bark.     The  object  of  this  movement  is  not  to  convey  the 
fluid  in  a  direct  line  from  one  point  to   another  (as   in   the  case  with  the 
ascending  current),  but  to  supply  every  part  with  materials  for  its  growth,  or 
for  the  production  of  its  peculiar  secretions.     Hence  the  vessels  in  which  it 
takes  place,  form  a  minutely-anastomosing  net-work,  instead  of  consisting  of  a 
system  of  straight  and  distinct  tubes.     Through  this  net-work,  the  latex  or 
elaborated  sap  is  seen  to  move,  exactly  as  does  the  blood  through  the  capil- 
lary vessels  of  animals.     The  movement  takes  place,  under  favourable  circum- 


544  OF  THE  CIRCULATION  OF  BLOOD. 

stances,  with  considerable  rapidity  ;  it  is  accelerated  by  heat,  and  retarded  by 
cold;  and  it  is  subject  to  all  those  minor  irregularities  (such  as  the  cessation 
of  movement,  or  change  in  the  direction  of  the  current,  in  a  particular  chan- 
nel), which  are  so  constantly  to  be  noticed  by  any  one  who  attentively  watches 
the  capillary  circulation  of  Animals,  and  which  clearly  prove  the  operation  of 
some  causes  independent  of  the  heart's  action  (§  734).  The  general  direction 
of  the  elaborated  sap,  through  this  capillary  system,  is  downwards ;  but  that 
the  force  of  gravity  cannot  have  much  to  do  with  the  movement,  is  shown  by 
the  fact  that,  in  dependent  branches,  it  has  to  ascend  towards  the  stem,  which 
it  will  do  without  interruption  from  this  cause.  Moreover  it  may  be  noticed 
that  this  circulation  takes  place  most  actively,  in  parts  which  are  undergoing  a 
rapid  developement;  and  that  its  energy  corresponds  with  the  vitality  of  the 
part.  Further ;  it  may  be  observed  to  continue  for  some  time  in  parts  that 
have  been  completely  detached  from  the  rest;  and  on  which  neither  vis  a 
tergo,  nor  vis  a  fronte,  can  have  any  influence.  It  is  evident,  then,  that  the 
force, — whatever  be  its  nature, — by  which  this  continued  movement  is  kept 
up,  must  be  developed  by  the  processes  to  which  that  movement  is  subserv- 
ient ;  in  other  words,  that  the  changes  involved  in  the  acts  of  nutrition  and 
secretion  are  the  real  source  of  the  motor  power.  The  manner  in  which  they 
become  so,  is  the  next  object  of  our  inquiry:  and  on  this  subject,  some  new 
views  have  recently  been  put  forth  by  Prof.  Draper,*  which  seem  to  account 
well  for  the  phenomena. 

a.  It  is  capable  of  being  shown,  by  experiments  on  inorganic  bodies,  that,  if  two  liquids 
communicate  with  each  other  through  a  capillary  tube,  for  the  walls  of  which  they  both 
have  an  affinity,  and  if  this  affinity  is  stronger  in  the  one  liquid  than  in  the  other,  a 
movement  will  ensue;  the  liquid  which  has  the  greatest  affinity  being  absorbed  most  ener- 
getically into  the  tube,  and  driving  the  other  before  it.  The  same  result  occurs  when  the 
lluid  is  drawn,  not  into  a  single  tube,  but  into  a  net-work  of  tubes,  permeating  a  solid 
structure;  for  if  this  porous  structure  be  previously  saturated  with  the  fluid,  for  which  it  has 
the  less  degree  of  attraction,  this  will  be  driven  out  and  replaced  by  that  for  which  it  has 
the  greater  affinity,  when  the  latter  is  permitted  to  enter  it.  Now  if,  in  its  passage  through 
the  porous  solid,  the  liquid  undergo  such  a  change,  that  its  affinity  be  diminished,  it  is  ob- 
vious that,  according  to  the  principle  just  explained,  it  must  be  driven  out  by  a  fresh  supply 
of  the  original  liquid;  and  that  thus  a  continual  movement  in  the  same  direction  would  be 
produced. 

b.  Now  this  is  precisely  that  which  seems  to  take  place  in  the  organized  tissue,  per- 
meated by  nutritious  fluid.  The  particles  of  this  fluid,  and  the  solid  matter  through  which 
it  is  distributed,  have  a  certain  affinity  for  each  other ;  which  is  exercised  in  the  nutritive 
changes,  to  which  the  fluid  becomes  subservient  during  the  course  of  its  circulation.  Cer- 
tain matters  are  drawn  from  it,  in  one  part,  for  the  support  and  increase  of  the  woody  tis- 
sue ;  in  another  part,  the  secreting  cells  demand  the  materials  which  are  requisite  for  their 
growth, — as  starch,  oil,  resin,  &c.;  and  thus  in  every  portion  that  is  traversed  by  the  vessels, 
there  are  certain  affinities  between  the  solids  and  the  fluids,  which  are  continually  being 
newly  developed  by  acts  of  growth,  as  fast  as  those  which  previously  existed  are  satisfied 
or  neutralized  by  the  changes  that  have  already  occurred.  Thus  in  the  circulation  of  the 
elaborated  sap,  there  is  a  constant  attraction  of  its  particles  towards  the  walls  of  the  vessels, 
and  a  continual  series  of  changes  produced  in  the  fluid  as  the  result  of  that  attraction.  The 
fluid,  which  has  given  up  to  a  certain  tissue  some  of  its  materials,  no  longer  has  the  same 
attraction  for  that  tissue;  and  it  is  consequently  driven  from  it  by  the  superior  attraction  then 
possessed  by  the  tissue  for  another  portion  of  the  fluid,  which  is  ready  to  undergo  the  same 
changes,  to  be  in  its  turn  rejected  for  a  fresh  supply.  Thus  in  a  growing  part,  there  is  a 
constantly-renewed  attraction  for  the  nutritive  fluid,  which  has  not  yet  traversed  it ;  whilst 
on  the  other  hand,  there  is  a  diminished  attraction  for  the  fluid,  which  has  yielded  up  the 
nutritive  materials  required  by  the  particular  tissues  of  the  part ;  and  thus  the  former  is  con- 
tinually driving  the  latter  before  it. 

c.  But  the  fluid,  which  is  thus  repelled  from  one  part,  may  still  be  attracted  towards  ano- 
ther ;  because  that  portion  of  its  contents,  which  the  latter  requires,  may  not  yet  have  been 
removed  from  it.  And  in  this  manner,  it  would  seem  that  the  flow  of  sap  is  maintained 


*  On  the  Forces  which  produce  the  Organization  of  Plants,  Chap.  in. 


MOTION  OF  THE  BLOOD  IN  THE  VESSELS.  545 

through  the  whole  capillary  net-work,  untili  t  is  altogether  exhausted  of  its  nutritive  matter. 
The  source  of  the  movement  is  thus  entirely  to  be  looked  for  in  the  changes  which  take  place 
in  the  act  of  growth;  and  the  influence  of  heat,  cold,  and  other  agents,  upon  the  movement 
is  exercised  through  their  power  of  accelerating  or  retarding  those  changes. 

714.  The  fluid  which  thus  descends  through  the  stem  and  roots,  seems  to 
be  at  last  almost  entirely  exhausted ;  a  portion  of  it  appears  to  find  its  way 
into  the  ascending  current,  and  to  be  mingled  with  it ;  but  all  the  rest  seems 
to  have  been  entirely  appropriated  by  the  different  tissues,  through  which  it 
has  circulated.     Thus  there  is  no  need  of  any  general  receptacle,  into  which 
it  may  be  collected,  and  from  which  it  may  take  a  fresh  departure ; — such  as 
is  afforded  by  the  heart  of  the  higher  animals.     And  as  the  purpose  of  this 
circulation  is  only  to  supply  the  nutritive  materials,  and  not  to  convey  oxy- 
gen,— this  element  being  but  little  required  in  the  vegetative  processes,  and 
being  supplied  by  other  means, — the  same  energy  and  rapidity  are   not  re- 
quired in  it,  as  need  to  be  provided  for  in  the  higher  animals. 

715.  In  the  lowest  Animals,  the  movement  of  the  circulating  fluid  seems 
as  independent  of  any  central  organ  of  impulsion,  as  it  has  been  shown  to  be 
in  Plants.     Thus,  in  the  living  Sponge,  a  current  of  water  is  continually 
flowing  through  the  tubes  and  channels,  by  which  its  substance  is  traversed, 
the  fluid  being  taken  in  by  the  small  orifices,  and  ejected  in  powerful  streams 
from  the  large  ones;  and  yet  the  most  attentive  examination  has  not  revealed 
any  mechanical  cause  for  this  movement.     In  some  of  the  compound  Polypi- 
fera,  a  similar  current  may  be  seen ;  and  it  is  curious  that,  in  many  species, 
its  direction  undergoes  a  periodical  change ;  being  reversed  at  intervals  of  a 
certain  number  of  seconds.     In  the  Star-Fish  and  Sea-Urchin  tribe,  a  com- 
plex circulation  of  blood  takes  place,  through  regular  vessels ;  and  here  we 
find  some  indication  of  a  contractile  cavity,  by  the  power  of  which  it  may  be, 
in  some  degree,  kept  up ;  but  its  feeble  pulsations  can  scarcely  be  regarded, 
as  having  any  great  share  in  the  movement  of  the  fluid  which  passes  through 
it. — In  the  Articulated  series,  there  is,  with  a  few  exceptions,  an  absence  of 
any  central  organ  of  impulsion,  possessed  of  power  sufficient  to   carry  the 
blood  through  the  vascular  system,  by  its  contractions  alone.     In  many  of  the 
aquatic  worms  and  larvae,  the  movement  of  the  blood,  and  the  pulsations  of 
the  dorsal  vessel,  may  be  distinctly  seen :  and  the  thinness  of  the  walls  of  the 
latter,  and  the  character  of  its  movements,  seem   clearly  to  show,  that  these 
can  scarcely  be  regarded  as  propulsive,  but  that  they  merely  result  from  the 
variations  in  the  current  which  passes  through  it, — the  sides  flapping  together 
when  there  is  an  outward  flow,  and  bulging  out  when  there  is  an  influx.     It 
is  in  these  Articulata,  in  which  there  is  a  provision  for  respiration  throughout 
the  whole  structure,  as  is  especially  the  case  in  Insects,  that  the  absence  of 
any  central  impulsive  power  is  most  remarkable. — In  the  Crustacea,  and  in 
the  Mollusca  in  general,  the  respiration  is  aquatic,  and  is    restricted  to  a  par- 
ticular organ  ;  and  in  these,  the  heart  is  found  to  be  more  muscular,  and  the 
circulation  to  be  more  under  its  control.     It  is  curious  to  remark,  however, 
that,  in  som'e  of  the  lower  Mollusca,  which  exhibit  a  tendency  to  aggregation 
into  compound  structures,  like  those  of  the  Polypifera,  there  is  the  same  want 
of  definiteness  in  the  course  of  the  circulation,  as  has  been  just  stated  to  exist 
in  the  latter  group; — the  flow  of  blood,  through  their  complex  apparatus  of 
nutritive  organs,  being  arrested  at  regular  intervals,  and  then  recommencing 
in  the  reverse  direction. 

716.  Even  in  Vertebrated  animals,  we  find  indications  of  the  same  defi- 
ciency of  central  power,  over  the  peripheral  circulation.     When  we  look  at 
the  simple,  thin-walled  heart  of  Fishes,  for  example,  it  seems  impossible  that 
it  should  have  much  power  over  the  current  of  blood  flowing  back  to  it  by 
the  veins ;  for  of  this  blood,  a  considerable  portion  has  to  pass  through  three 

46* 


546  OF  THE  CIRCULATION  OF  BLOOD. 

sets  of  capillaries,  between  its  ejection  from  the  heart,  and  its  return  to  it.  It 
is  first  transmitted  through  the  respiratory  capillaries,  for  the  purpose  of  aera- 
tion ;  the  confluent  vessels,  which  collect  the  arterial  blood  from  these,  ter- 
minate in  the  general  systemic  trunk  or  Aorta,  in  which,  as  in  the  veins  of 
Man,  there  is  an  absence  of  pulsation,  and  by  these,  it  is  distributed  to  the 
systemic  capillaries ;  and  the  blood  which,  after  passing  through  these,  re- 
turns from  the  posterior  part  of  the  body,  and  from  the  viscera,  passes  through 
another  set  of  capillaries,  those  of  the  liver  and  kidneys,  before  it  returns  to 
the  heart. — Even  in  the  warm-blooded  Vertebrata,  in  which  the  respiratory 
circulation  is  separately  performed,  the  blood  which  is  returned  from  the  in- 
testines, passes  into  a  trunk,  the  Vena  Portse,  which  again  subdivides  into 
capillary  ramifications,  being  transmitted  over  the  plexus  of  biliary  ducts,  of 
which  the  liver  is  chiefly  composed  ;  and  thus  the  Vena  Portae,  as  Hunter 
justly  observed,  should  be  considered  rather  in  the  light  of  an  artery,*  re- 
sembling as  it  does  the  aorta  of  Fishes.  Considering  the  small  amount  of 
pressure  which  is  exerted  by  the  blood,  upon  the  sides  of  the  vessels  that  are 
formed  by  the  reunion  of  capillaries,  it  seems  impossible  to  imagine  that  the 
vis  a  tergo  derived  from  the  impulsive  action  of  the  Heart,  can  be  alone  suf- 
ficient to  maintain  the  portal  circulation. 

2.— .fiction  of  the  Heart. 

717.  The  Heart  is  endowed  in  an  eminent  degree  with  the  property  of 
irritability ;  by  which  is  meant,  the  capability  of  being  easily  excited  to 
movements  of  contraction  alternating  with  relaxation  (§  574).  Thus,  after 
the  Heart  has  been  removed  from  the  body,  and  has  ceased  to  contract,  a 
slight  irritation  Mrill  cause  it  to  execute,  not  one  movement  only,  but  a  series 
of  alternate  contractions  and  dilatations,  gradually  diminishing  in  vigour  until 
they  cease.  The  contraction  begins  in  the  part  irritated,  and  then  extends  to 
the  rest.  It  appears  from  Mr.  Paget's  experiments,!  that  it  is  necessary  for 
the  propagation  of  this  irritation,  that  the  parts  should  be  connected  by  mus- 
cular tissue,  of  which  a  very  narrow  isthmus  will  suffice  ;  and  that  the  pro- 
pagation will  not  take  place,  if  the  connecting  isthmus  be  composed  of  ten- 
don, even  though  this  be  a  portion  of  the  auriculo-ventricular  ring,  which  has 
been  supposed  by  some  to  be  peculiarly  efficacious  in  this  conduction. — That 
the  irritability  of  the  heart  is  not  dependent  upon  the  Cerebro-spinal  system, 
appears  not  merely  from  the  manifestation  of  it,  when  the  organ  is  altogether 
removed  from  the  body,  but  also  from  the  fact,  that  if  the  flood  of  blood 
through  the  lungs  be  kept  up  by  artificial  respiration,  the  heart's  action  will 
continue  for  a  lengthened  period,  even  after  the  Brain  and  Spinal  Cord  have 
been  removed,  and  when  animal  life  is,  therefore,  completely  extinct.  Hence 
we  see  that  the  Irritability  of  this  organ  must  be  an  endowment  properly  be- 
longing to  it,  and  not  derived  from  that  portion  of  the  Nervous  System.  Like 
the  contractility  of  other  muscles,  it  can  only  be  sustained  for  any  great  length 
of  time,  by  a  supply  of  Arterial  blood  to  its  own  tissue  (§  584).  It  is  much 
less  speedily  lost  in  cold-blooded  animals,  however,  than  in  warm-blooded ; 
the  heart  of  the  Frog,  for  example,  will  go  on  pulsating  for  many  hours  after 
its  removal  from  the  body  ;  and  it  is  stated  by  Dr.  MitchellJ  that  the  heart  of 
a  Sturgeon,  which  he  had  inflated  with  air,  continued  to  beat,  until  the  auricle 

*  That  it  conveys  venous  blood,  is  no  reason  to  the  contrary ;  since  this  is  the  case  with 
the  pulmonary  artery.  The  character  of  an  artery  is  derived  from  the  division  of  its  current 
into  several  divergent  streams. 

f  Brit,  and  For.  Med.  Review,  vol.  xxi.  p.  551. 

J  American  Journal  of  the  Medical  Sciences,  vol.  vii.  p.  58. 


ACTION  OF  THE  HEART.  547 

had  absolutely  become  so  dry,  as  to  rustle  during  its  movements.  It  has 
lately  been  shown  by  Mr.  Todd,  that  the  irritability  of  the  heart  is  of  long 
duration  after  death  in  very  young  animals  :  which,  as  long  since  demonstrated 
by  Dr.  Edwards,  agree  with  the  cold-blooded  Vertebrata  in  their  power  of 
sustaining  life,  for  a  lengthened  period,  without  oxygen. — It  is  difficult  to  ac- 
count for  the  long  continuance  of  the  alternate  contractions  and  relaxations  of 
the  muscular  parietes  of  the  heart,  after  all  evident  stimuli  have  ceased  to  act 
upon  it;  and  many  theories  have  been  offered  on  the  subject,  none  of  which 
afford  an  adequate  explanation.  The  extraordinary  tendency  to  rhythmical 
action,  which  distinguishes  the  heart  from  all  other  muscles,  is  shown  by  the 
fact  that  not  only  do  the  entire  hearts  of  cold-blooded  animals  continue  to  act, 
long  after  their  removal  from  the  body,  but  even  separated  portions  of  them 
will  contract  and  relax  with  great  regularity  for  a  long  time.  Thus  the  auri- 
cles will  persist  in  their  rhythmical  action,  when  cut  off  above  the  auriculo- 
ventricular  rings ;  and  the  apex  of  the  heart  will  do  the  same,  when  separated 
from  the  rest  of  the  ventricle.  The  stimulus  of  the  contact  of  blood  with  the 
lining  membrane  of  the  heart,  to  which  its  regular  actions  have  been  com- 
monly referred,  can  have  no  influence  in  producing  these  movements ;  nor 
does  it  appear  that  the  contact  of  air  can  take  its  place ;  since,  as  Dr.  J.  Reid 
has  shown,  the  rhythmical  contractions  of  the  heart  of  a  frog  will  continue 
in  vacua.  Nor  is  there  any  evidence  that  the  flow  of  blood  through  the 
cavities  has  the  effect  of  securing  the  regularity  of  their  successive  contrac- 
tions in  the  living  body ;  for  this  regularity  is  equally  marked  in  the  contrac- 
tions of  the  excised  heart,  when  perfectly  emptied  of  blood,  so  long  as  its 
movements  continue  vigorous.  But  when  its  irritability  is  nearly  exhausted, 
the  usual  rhythm  is  often  a  good  deal  disturbed,  so  that  the  contractions  of 
the  auricles  and  ventricles  do  not  regularly  alternate  with  each  other ;  and  one 
set  frequently  ceases  before  the  other. 

a.  It  was  formerly  supposed,  that  the  movements  of  the  Heart  were  dependent  upon  its 
connection  with  the  centres  of  the  Cerebro-Spinal  nervous  system ;  and  the  experiments  of 
Lcgallois  and  others,  who  found  that  they  were  arrested  by  crushing,  or  otherwise  suddenly 
destroying,  large  portions  of  these  centres,  appeared  to  favour  the  supposition.     But  it  has 
been  shown  by  Dr.  Wilson  Philip  and  his  successors  in  the  same  inquiry,  that  the  whole 
Cerebro-Spinal  axis  might  be  gradually  removed,  without  any  such  consequence ;  which 
fact  harmonizes  perfectly  with  the  "experiments  prepared  for  us  by  Nature,"  in  the  pro- 
duction of  monsters  destitute  of  these  centres,  which  nevertheless  possessed  a   regularly- 
pulsating  heart.     As  already  mentioned  (§  416),  it  is  difficult  to  obtain  any  distinct  evidence, 
that  the  actions  of  the  heart  are  affected  by  any  ordinary  irritation  of  the  Par  Vagum ;  but 
the  recent  experiments  of  MM.  Weber  have  shown  that  its  movements  may  be  immediately 
arrested,  by  the  transmission  of  the  electric  current  from  a  rotating  magnet,  either  through 
the  Spinal  Cord,  or  through  the  Vagi  nerves  divided  at  their  origin.     The  same  irritation, 
however,  applied  to  a  single  one  of  the  Vagi,  produced  no  effect.* 

b.  It  has  latterly  been  the  fashion  with  many,  however,  to  attribute  the  action  of  the  Heart 
to  the  Sympathetic  system  ;  but  of  this  there  is  no  sufficient  evidence.     The  possibility  of 
exciting  the  action  of  the  heart  through  the  Sympathetic  nerve  (§  576),  shows  that  this  may 
have  an  influence  on  its  movements;  whilst  the  great  difficulty  with  which  any  evidence 
to  this  effect  can  be  procured,  seems  a  sufficient  proof,  as  in  the  case  of  the  Muscular  coat  of 
the  intestines  (§  388),  that  this  influence  cannot  be  nearly  adequate  to  the  constant  main- 
tenance of  a  function  so  energetic.     Some  have  more  recently  maintained,  that  the  move- 
ments are  of  a  strictly  reflex  nature,  and  that  they  are  effected  through  the  agency  of  certain 
minute  ganglia,  belonging  to  the  Sympathetic  system,  and  scattered  through  the  substance  of 
the  heart ; — in  this  way  endeavouring  to  account  for  the  persistence  of  the  motions  of  the 
organ  after  its  complete  removal  from  the  body,  and  under  circumstances  which  suspend  all 
reflex  movements  that  have  their  centre  in  the  cerebro-spirial  system.     But  this  attempt  at 
explanation  affords  no  aid  in  the  solution  of  the  cause  of  the  continued  rhythmical  move- 
ments of  the  organ,  or  of  its  separated  portions,  after  the  withdrawal  of  all  stimuli  that  can 
be  supposed  to  operate  in  exciting  them;  and  the  phenomena  are  just  as  fully  explained  by 

*  Archives  d'Anat.  Gener.  et  de  Physiol.,  Janv.  1846. 


548  OF  THE  CIRCULATION  OF  BLOOD. 

attributing  them  to  the  independent  irritability  of  the  muscular  fibre,  as  by  supposing  the 
nervous  system  to  be  concerned  in  them. 

c.  It  would  appear,  however,  that  changes  in  the  Ganglionic  nerves,  like  strong  impres- 
sions upon  the  Cerebro-spinal  system  (§  580),  may  have  the  effect  of  impeding  or  even 
checking  the  Heart's  action ;  for  a  case  has  lately  been  recorded,  in  which  the  movements 
were  occasionally  checked  for  an  interval  of  from  4  to  6  beats,  its  cessation  of  action  giving 
rise  to  the  most  fearful  sensations  of  anxiety,  and  to  acute  pain  passing  up  to  the  head  from 
both  sides  of  the  chest, — these  symptoms  being  connected,  as  it  proved  on  a  post-mortem 
examination,  with  the  pressure  of  an  enlarged  bronchial  gland  upon  the  great  cardiac  nerve.* 
It  may  be  surmised,  that  in  many  cases  of  angina  pectoris,  in  which  no  lesion  sufficient  to 
account  for  death  could  be  discovered,  some  affection  of  the  cardiac  plexus  might  have  been 
traced  on  a  more  careful  examination. 

718.  When  the  Heart  is  exposed  in  a  living  animal,  and  its  movements  are 
attentively  watched,  they  are  seen  to  follow  each  other  with  great  regularity. 
In  an  active  and  vigorous  state  of  the  circulation,  however,  they  are  so  linked 
together,  that  it  is  not  easy  to  distinguish  them  into  periods.  A  case  has 
fallen  under  the  notice  of  Prof.  Cruveilhier,  in  which  the  heart  was  exterior 
to  the  chest,  having  escaped  from  it  by  a  perforation  in  the  superior  part  of 
the  sternum  ;  and  his  observations  upon  it  may  be  perhaps  regarded  as  more 
satisfactory  than  such  as  are  made  after  the  very  severe  operation  required  for 
the  artificial  exposure  of  the  organ ;  although  they  are  liable  to  some  excep- 
tion, from  the  very  early  age  of  the  subject  of  them,  which  had  only  been 
born  nine  hours.  His  conclusions  will  be  here  adopted  ;  with  such  addi- 
tional remarks  as  are  suggested  by  the  experimental  researches  of  others, 
who  have  made  this  question  a  subject  of  special  attention.!  It  is  universally 
admitted,  that  both  Auricles  contract,  and  also  dilate  simultaneously  ;  and  that 
both  Ventricles  do  the  same : — also  that  the  systole  or  contraction  of  the  ven- 
tricles corresponds  with  the  projection  of  blood  into  the  arteries,  causing  the 
pulse ;  whilst  the  diastole  or  dilatation  of  the  ventricles  coincides  with  the 
collapse  of  the  arteries.  It  is  further  admitted,  that  the  contraction  of  the 
Ventricles,  and  that  of  the  Auricles,  alternate  with  one  another ;  each  taking 
place  (for  the  most  part,  at  least),  during  the  dilatation  of  the  other.  But  it 
is  a  question  whether  there  is  any  interval  between  them.  In  the  case  just 
alluded  to,  the  contraction  of  the  Ventricles  is  stated  to  have  been  precisely 
synchronous  with  the  dilatation  of  the  Auricles ;  and  the  dilatation  of  the 
Ventricles  to  have  been  performed  at  the  same  time  with  the  contraction  of 
the  Auricles,  no  period  of  repose  intervening  between  the  two  sets  of  actions. 
It  appears,  however,  from  the  concurrent  testimony  of  numerous  experiment- 
ers, that,  whilst  the  contraction  of  the  Ventricle  immediately  succeeds  that  of 
the  Auricle,  an  interval,  which  is  usually,  however,  extremely  brief,  may  elapse 
between  the  partial  dilatation  of  the  Ventricles  and  the  succeeding  systole  of 
the  Auricles.  The  Ventricular  dyastole  may  be  distinguished  into  two  stages, 
of  which  the  first  immediately  succeeds  its  systole,  and  manifests  itself  in  the 
recession  of  the  Heart's  apex  from  the  front  of  the  chest ;  whilst  the  second 
is  attended  with  an  enlargement  of  the  heart  in  all  its  dimensions,  and  is 
synchronous  with  the  Auricular  contraction.  It  is  between  these  two,  that 
the  interval  of  repose  occurs,  where  it  can  be  observed.  The  following 
tabular  view  will,  perhaps,  make  this  account  more  intelligible ;  it  is  framed 
in  such  a  manner  as  to  commence  with  the  Auricular  contraction ;  but,  when 
considering  the  Sounds  of  the  heart,  it  will  be  necessary  to  commence  with 
the  Ventricular  systole. 

*  Muller's  Archiv.  1841,  heft  iii.;  and  Brit,  and  For.  Med.  Rev.,  Oct.  1841. 
•f-  See  also  another  case,  recently  observed  by  M.  Monod,  in  Bullet,  de  1'Acad.  de  Med., 
Fevr.  1843  ;  and  Edinb.  Med.  and  Surg.  Journ.,  July  1843. 


ACTION  OF  THE  HEART.  549 

Auricles.  Ventricles. 

Contraction.  2d  stage  of  dilatation. 

Dilatation.  Contraction. — Pulse. 

1st  stage  of  dilatation. 
Brief  interval  of  Repose. 
Contraction.  2d  stage  of  dilatation. 

Dilatation.  Contraction. — Pulse. 

719.  The  duration  of  the  Contraction  of  the  Ventricles  is,  according  to 
Cruveilhier,  double  that  of  their  Dilatation ;  and  the  same  holds  good  of  the 
Auricles.     In  the  Systole  of  the  Ventricles,  their  surface  becomes  rugous  ;  the 
superficial  veins  swell ;  the  carneae  columnar  of  the  left  ventricle  are  delineated  ; 
and  the  curved  fibres  of  the  conical  termination  of  the  left  ventricle,  which 
alone  constitutes  the  apex  of  the  heart,  become  more  manifest.     During  their 
contraction,  every  diameter  of  the  Ventricles  is  lessened  ;   their  shortening  is 
the  most  sensible  change ;  but  this  is  owing  to  the  vertical  diameter  being  the 
greatest.     The  lower  extremity  of  the  left  ventricle,  or,  in  other  words,  the 
apex  of  the  heart,  describes  a  spiral  movement  from  right  to  left,  and  from  be- 
hind forwards.     It  is  to  this  slow,  gradual,  and  as  it  were  successive  spiral 
contraction,  that  the  forward  movement  of  the  apex  of  the  heart  is  owing,  and 
its  consequent  percussion  against  the  thoracic  parietes.     The  ventricular  sys- 
tole is  not  accompanied  by  a  projection  of  the  entire  heart  forwards  (as  some 
have  maintained) ;  for  it  is  exclusively  the  spiral  contraction,  which  determines 
the  approach  of  the  apex  of  the  heart  to  the  thoracic  parietes.     The  Diastole 
of  the  heart,  according  to  Cruveilhier,  has  the  rapidity  and  energy  of  an  active 
movement:   triumphing  over  pressure  exercised  upon  the  organ,  so  that  the 
hand  closed  upon  it  is  opened  with  violence.     This  is  an  observation  of  great 
importance ;  but  of  the  cause  to  which  this  active  dilatation  is  due,  no  definite 
account  can  be  given.     It  may  partly  be  explained,  perhaps,  by  the  elasticity 
of  the  tissue,  interwoven  with  muscular  fibre  in  the  substance  of  the  heart; 
and  this  may  be  the  cause  of  the  first  Ventricular  dilatation,  the  second  being 
produced  by  the  ingress  of  blood  occasioned  by  the  auricular  systole.     But 
the  dilatation  of  the  Auricles  appears  to  be  much  greater  than  can  be  accounted 
for  by  any  vis  a  tergo  (which,  as  will  hereafter  appear,  is  extremely  small  in 
the  venous  system),  or  by  the  elasticity  of  its  substance  ;  for  it  was  observed 
in  this  case  to  be  so  great,  that  the  right  auricle  seemed  ready  to  burst,  so  great 
was  its  distension,  and  so  thin  were  its  walls.     Moreover,  the  large  Veins 
near  the  heart  contract  simultaneously  with  the  auricular  Systole,  and  not  with 
its  Diastole ;  so  that  they  can  have  no  influence  in  causing  its  dilatation.     The 
Ventricular  diastole  is  accompanied  with  a  projection  of  the  heart  downwards ; 
this  motion  was  at  its  maximum  when  the  child  was  placed  vertically,  and 
was  very  strongly  marked. 

720.  When  the  ear  is  applied  over  the  cardiac  region,  during  the  natural 
movements  of  the  Heart,  two  successive  sounds  are  heard;  each  pair  of  which 
corresponds  with  one  pulsation.     The  whole  interval  between  one  beat  of  the 
the  Heart,  and  the  next,  may  be  divided  into  four  parts ;   of  which  the  two 
first  are  occupied  by  what  is  commonly  known  as  the  first  sound ;  the  third, 
by  the  second  sound  ;  whilst  the  fourth  is  a  period  of  repose. — The  first  sound 
is  dull  and  prolonged ;  it  is  evidently  synchronous  with   the  impulse  of  the 
Heart  against  the  parietes  of  the  chest,  and  also  with  the  pulse,  as  felt  near 
the  heart ;  it  must,  therefore,  be  produced  during  the  Ventricular  Systole. — 
The  second  sound  follows  so  immediately  upon  the  conclusion  of  the  first, 
that  it  can  scarcely  be  imagined  to  take  place  during  the  auricular  systole  as 
some  have  supposed,  but  must  be  assigned  to  the  period  of  the  first  stage  of 
the  Ventricular  Diastole.     This,  indeed,  may  now  be  regarded  as  clearly  esta- 
blished; for  it  has  been  fully  demonstrated,  that  the  second  sound  is  due  to 


550  OF  THE  CIRCULATION  OF  BLOOD. 

the  sudden  filling-out  of  the  Semilunar  valves  of  the  aorta  and  pulmonary 
artery,  with  blood ;  when  the  outward  current  through  them  has  ceased,  and 
the  incipient  dilatation  of  the  ventricles  occasions  a  vacuum  behind  them.  If 
one  of  these  valves  be  hooked  back  by  a  curved  needle  against  the  side  of  the 
artery,  so  that  a  reflux  of  blood  is  permitted,  the  sound  is  entirely  suppressed. 
The  first  sound  cannot  be  so  readily  or  satisfactorily  accounted  for.  That  it 
is  partly  due  to  the  Impulse  of  the  apex  of  the  Heart,  seems  proved  by  the 
fact,  that,  when  this  impulse  is  prevented,  the  sound  is  much  diminished  in 
intensity ;  and  also  by  the  circumstance  that,  when  the  Ventricles  contract 
with  vigour,  the  greatest  intensity  of  the  sound  is  over  the  point  of  percussion. 
But  that  it  is  not  entirely  due  to  this  cause  is  also  evident  from  the  fact,  that 
a  sound  may  still  be  heard,  when  the  Heart  is  contracting  out  of  the  body;  as 
in  the  case  observed  by  Prof.  Cruveilhier.  This  sound  has  been  attributed, 
by  some  experimenters,  to  the  flapping-back  of  the  auriculo-ventricular  valves  ; 
by  others  to  the  muscular  contraction  of  the  walls  of  the  ventricles  ;  by  others 
again  to  the  rush  of  blood  along  the  irregular  walls  of  the  ventricles,  and 
through  the  comparatively  narrow  orifices  of  the  aorta  and  pulmonary  artery. 
This  last  is  probably  the  most  consistent  with  truth ;  as  would  appear  from 
the  following  interesting  observations  made  by  Cruveilhier.  By  applying  the 
finger  to  the  origin  of  the  pulmonary  artery  (which  is  situated  in  front  of  the 
aorta,  and  completely  conceals  it),  a  perfectly  distinct  vibratory  fremissement 
corresponding  with  the  ventricular  diastole,  was  perceived;  but  no  such  vibra- 
tory thrill  could  be  felt  by  the  finger,  when  applied  to  any  part  of  the  base  of 
the  ventricles :  whence  it  was  evident,  that  no  action  takes  place  in  the  mitral 
and  tricuspid  valves,  which  can  give  rise  to  the  same  palpable  effects,  as  those 
produced  by  the  semilunar  valves.  The  same  was  ascertained  regarding  the 
valvular  sound,  which  could  be  distinctly  heard,  by  laying  the  finger  against 
the  origin  of  the  pulmonary  artery,  and  applying  the  ear  to  it  as  to  a  stetho- 
scope :  whilst  nothing  of  the  kind  could  be  perceived  in  the  region  of  the 
auriculo-ventricular  valves.  Hence  it  seems  quite  certain,  that  the  natural  first 
sound  cannot  be  dependent  in  any  way  upon  the  action  of  the  mitral  and  tri- 
cuspid valves.  It  appeared,  on  the  contrary,  that  the  maximum  intensity  of 
ihe  first  sound  was  in  precisely  the  same  situation  as  the  maximum  intensity 
of  the  second, — namely,  at  the  origin  of  the  large  arteries ;  and  that  it  dimin- 
ished, as  the  ear  was  carried  from  the  base,  towards  the  apex  of  the  heart. 
Moreover,  the  first  sound  was  observed  to  be  of  exactly  the  same  character 
with  the  second  (the  complicating  effect  of  the  impulse  being  here  withdrawn) ; 
except  as  to  its  intensity,  which  was  less, — and  its  duration,  which  was  greater. 
721.  Hence,  although  these  observations  do  not  entitle  us  to  deny  the  par- 
ticipation of  the  muscular  contraction,  and  of  the  movement  of  the  blood  over 
the  ventricular  walls,  in  the  production  of  the  first  sound,  they  establish  (if 
correct),  that  the  principal  cause  of  it  exists  at  the  entrances  to  the  arterial 
trunks ;  and  it  does  not  seem  that  any  other  reason  can  be  assigned  for  it,  than 
the  prolonged  rush  of  blood  through  their  orifices,  and  the  throwing  back  of  the 
Semilunar  valves ;  which,  in  suddenly  flapping  down  again,  produce  the  second 
sound. — That  an  exaggeration  of  the  first  sound,  not  essentially  differing  from 
it  in  character,  is  often  produced  by  disease  of  the  sigmoid  valves,  which 
causes  an  obstruction  of  their  orifice,  has  long  been  known  ;  and  in  such 
cases,  the  character  of  the  second  sound  is  also  changed.  Indeed,  M.  Cru- 
veilhier states  it  as,  in  his  opinion,  an  uniform  occurrence,  that  disease  of  the 
Semilunar  valves  alters  both  sounds.  When  this  disease  is  such  as  to  prevent 
the  valves  from  effectually  closing,  a  reflux  of  blood  takes  place  into  the  ven- 
tricle at  the  time  of  its  diastole;  causing  a  rushing  sound,  more  or  less  pro- 
longed, to  be  heard  in  the  intervals  of  the  pulse,  instead  of  with  it.  These 
considerations  appear  to  prove  almost  incontestably,  that  the  cause  of  the  first 


ACTION  OF  THE  HEART. 


551 


sound,  and  that  of  the  second,  are  very  closely  allied ;  and  this  view,  which  if 
correct  is  of  great  importance  in  the  explanation  of  numerous  morbid  phe- 
nomena, harmonizes  well  with  the  known  effect  of  a  slight  obstruction  in  a 
tube,  through  which  fluid  is  being  rapidly  forced,  in  producing  a  prolonged 
sound,  very  analogous  to  the  first  sound  of  the  heart.  The  following  table 
may  assist  the  student  in  connecting  the  sounds  of  the  Heart  with  its  move- 
ments. 

FIRST   SOUWD.         Ventricular  Systole,  and  Auricular  Diastole.      Impulse  of  apex  against 

parietes  of  chest.     Pulsation  in  arteries. 
SECOND   SOUND.       First  stage  of  Ventricular  Diastole. 
INTERVAL  Short  repose ;  then  Auricular  Systole,  and  second  stage  of  Ventricular 

Diastole. 

722.  The  course  of  the  circulating  fluid  through  the  Heart,  and  the  action 
of  its  different  valves,  will  now  be  briefly  described.  The  Venous  blood, 
which  is  returned  by  the  ascending  and  descending  Vepa  Cava,  enters  the 
right  Auricle  during  its  diastole  ;  and,  when  it  contracts,  is  forced  between 
the  Tricuspid  valves,  into  the  Ventricle.  The  reflux  of  blood  into  the  veins, 
during  the  auricular  systole,  is  prevented  by  the  valves  with  which  they  are 
furnished  ;  but  these  valves  are  so  formed,  as  not  to  close  accurately,  espe- 

[Fig.  212. 


The  Anatomy  of  the  Heart;  1,  the  right  auricle;  2,  the  entrance  of  the  superior  venacava;  3,  the 
entrance  of  the  inferior  cava ;  4,  the  opening  of  the  coronary  vein,  half  closed  by  the  coronary  valve  ; 
5,  the  Eustachian  valve  ;  6,  the  fossa  ovalis,  surrounded  by  the  annulis  ovalis  ;  7,  the  tuberculum  Low- 
eri  ;  8,  the  musculi  pectinati  in  the  appendix  auriculae;  9,  the  auriculo-ventricular  opening;  10,  the 
cavity  of  the  right  ventricle;  11,  the  tricuspid  valve,  attached  by  the  chordae  tendinece  to  the  carneae 
columnse  (12);  13,  the  pulmonary  artery,  guarded  at  its  commencement  by  three  semilunar  valves;  14, 
the  right  pulmonary  artery,  passing  beneath  the  arch  and  behind  the  ascending  aorta;  15,  the  left  pulmo- 
nary artery,  crossing  in  front  of  the  descending  aorta;  *,  the  remains  of  the  ductus  arteriosus,  acting  as 
a  ligament  between  the  pulmonary  artery  and  arch  of  the  aorta;  the  arrows  mark  the  course  of  the 
venous  blood  through  the  right  side  of  the  heart;  entering  the  auricle  by  the  superior  and  inferior  cava, 
it  passes  through  the  auriculo-ventricular  opening  into  the  ventricle,  and  thence  through  the  pulmonary 
artery  to  the  lungs  ;  16,  the  left  auricle  ;  17,  the  openings  of  the  four  pulmonary  veins  ;  18,  the  auriculo- 
ventricular  opening ;  19,  the  left  ventricle ;  20,  the  mitral  valve,  attached  by  its  chordae  tendineae  to  two 
large  columnse  carneee,  which  project  from  the  walls  of  the  ventricle ;  21,  the  commencement  and  course 
of  the  ascending  aorta  behind  the  pulmonary  artery,  marked  by  an  arrow;  the  entrance  of  the  vessel 
is  guarded  by  three  semilunar  valves  ;  22,  the  arch  of  the  aorta.  The  comparative  thickness  of  ihe  two 
ventricles  is  shown  in  the  diagram.  The  course  of  the  arterial  blood  through  the  left  side  of  the  heart 
is  marked  by  arrows.  The  blood  is  brought  from  the  lungs  by  the  four  pulmonary  veins  into  the  left 
auricle,  and  passes  through  the  auriculo-ventricular  opening  into  the  left  ventricle,  whence  it  is  con- 
veyed by  the  aorta  to  every  part  of  the  body.] 


552  OF  THE  CIRCULATION  OF  BLOOD. 

cially,  when  the  tubes  are  distended  ;  so  that  a  small  amount  of  reflux  usually 
takes  place,  and  this  is  much  increased  when  there  is  any  obstruction  to  the 
pulmonary  circulation.  Whilst  the  right  Ventricle  is  contracting  upon  the 
blood  that  has  entered  it,  the  carnese  columns,  which  contract  simultaneously 
with  its  proper  walls,  put  the  chordae  tendinese  upon  the  stretch ;  and  these 
draw  the  flaps  of  the  Tricuspid  valve  into  the  auriculo-ventricular  axis.  The 
blood  then  getting  behind  them,  and  being  compressed  by  the  contraction  of 
the  ventricle,  forces  the  flaps  together  in  such  a  manner  as  to  close  the  orifice  ; 
but  they  do  not  fall  suddenly  against  each  other,  as  is  the  case  with  the  semi- 
lunar  valves,  since  they  are  restrained  by  the  chordae  tendine.se. ;  whence  it  is, 
that  no  sound  is  produced  by  their  closure.  The  blood  is  expelled  by  the 
ventricular  systole  into  the  Pulmonary  Artery,  which  it  distends,  passing 
freely  through  the  Semilunar  valves ;  but  as  soon  as  the  vis  d  tergo  ceases, 
and  reflux  might  take  place  by  the  contraction  of  the  arterial  walls,  the  valves 
are  filled  out  by  the  backward  tendency  of  the  blood,  and  completely  check 
the  return  of  any  portion  of  it  into  the  ventricle.  The  blood,  after  having  cir- 
culated through  the  lungs,  returns  as  Arterial  blood,  by  the  Pulmonary  Veins, 
to  the  left  Auricle ;  whence  it  passes  through  the  mitral  valves  into  the  left 
Ventricle,  and  thence  into  the  Aorta, — in  the  same  manner  with  that  on  the 
other  side,  as  just  described. 

723.  There  are,  however,  some  important  differences  in  the  structure  and 
functional  actions  of  the  two  divisions  of  the  Heart,  which  should  be  here 
adverted  to. 

a.  The  walls  of  the  left  Ventricle  are  considerably  thicker  than  those  of  the  right;  and 
its  force  of  contraction  is  much  greater.     The  following  are  the  comparative  results  of  M. 
Bizot's  recent  measurements,  taking  the  average  of  males  from  16  to  89  years. 

BASE.  MIDDLE.  APEX. 

Left  Ventricle  4£  lines  5£  lines  3|  lines 

Right  Ventricle  Ijf  lines  1|  lines  1^  lines 

In  the  female,  the  average  thickness  is  somewhat  less.  It  will  be  seen  that  the  point  of 
greatest  thickness  in  the  left  Ventricle  is  near  its  middle ;  while  in  the  right,  it  is  nearer  the 
base.  The  thickness  of  the  former  goes  on  increasing  during  all  periods  of  life,  from  youth 
to  advanced  age  ;  whilst  that  of  the  right  is  nearly  stationary.  The  left  Auricle  is  somewhat 
thicker  than  the  right ;  the  average  thickness  of  the  former  being,  according  to  Bouillaud, 
a  Jine  and  a  half;  whilst  that  of  the  latter  is  only  a  line.  In  regard  to  the  refttive  capaci- 
ties of  the  right  and  left  cavities,  much  difference  of  opinion  has  prevailed.  The  right  Au- 
ricle is  generally  allowed  to  be  more  capacious  than  the  left ;  and  the  same  is  commonly- 
taught  of  the  right  Ventricle.  So  much  fallacy  may  arise,  however,  from  the  peculiar  condi- 
tion of  the  animal  at  the  moment  of  death,  that  this  is  not  easily  proved,  and  is,  indeed,  by 
no  means  certain. 

b.  Many  eminent  Anatomists  maintain,  that  the  two  cavities  are  equal.     The  capacity  of 
each  of  the  cavities  may  be  estimated,  in  the  full-sized  Heart,  at  about  two  ounces ;  that  of 
the  Auricles  being  probably  a  little  less ;  and  that  of  the  Ventricles  a  little  greater.     That 
the  Ventricles  receive  more  blood  from  the  Auricles,  than  the  latter  could  transmit  to  them 
by  simply  emptying  themselves  once,  seems,  therefore,  probable ;  and  may  be  accounted  for 
by  the  fact  already  stated,  regarding  the  slight  intermission  in  the  Ventricular  Diastole,  during 
which  more  blood  may  enter  the  Auricle  from  the  veins. 

c.  There  is  a  well-known  anatomical  difference  between  the  Auriculo- Ventricular  valves, 
on  the  two  sides,  which  has  given  rise  to  the  diversity  of  name.     This  seems,  from  the  re- 
searches of  Mr.  King,*  to  be  connected  with  an  important  functional  difference.     The  Mitral 
valve  closes  much  more  perfectly  than  the  Tricuspid :  and  the  latter  is  so  constructed,  as  to 
allow  of  considerable  reflux,  when  the  cavities  are   greatly  distended.     Many  occasional 
causes  tend  to  produce  an  accumulation  of  blood  in  the  venous  system,  and  in  the  right  side 
of  the  Heart;  thus,  any  obstruction  to  the  pulmonary  circulation,  cold,  compression  of  the 
venous  system  by  muscular  action.  &c.,  are  known  to  favour  such  a  condition.     This  is  a 
state  of  peculiar  danger,  from  the  liability  which  over-distension  of  the  Ventricular  cavity 
has,  to  produce  a  state  of  muscular  paralysis ;  and  in  the  structure  of  the  Heart  itself,  there 
seems  to  be  a  provision  against  it.     For,  when  the  ventricle  is  thus  distended,  the  Tricuspid 

*  Guy's  Hospital  Reports,  vol.  ii. 


ACTION  OF  THE  HEART.  553 

valves  do  not  close  properly;  and  a  reflux  of  blood  is  permitted,  not  only  into  the  Auricle, 
but  also  (through  the  imperfect  closure  of  their  valves  under  the  same  circumstances),  into 
the  large  veins.  This  is  proved  by  the  fact,  several  times  observed  by  Dr.  J.  Reid,  in  his 
experiments  upon  Asphyxia,  &c.,  that,  when  the  action  of  the  Right  Ventricle  had  ceased 
from  over-distension,  he  could  frequently  re-excite  it,  not  merely  by  puncturing  its  walls,  but 
by  making  an  opening  in  the  jugular  vein.  This  fact  evidently  affords  an  indication  of  great 
importance  in  the  treatment  of  Asphyxia ;  and  it  explains  the  reflux  of  blood,  or  venous 
pulse,  which  is  frequently  observed  in  cases  of  pulmonary  disease,  and  which,  according  to 
Mr.  King,  always  exists,  though  in  a  less  striking  degree. 

724.  It  is  not  quite  certain  whether  the  Ventricles  empty  themselves  com- 
pletely .at  each  contraction  ;  but  it  seems  probable  that  the  blood  which  they 
contain,  is  not  entirely  forced  into  the  arteries.     The  quantity  which  is  pro- 
pelled by  each  Ventricle,  at  every  stroke,  maybe  estimated,  therefore,  at  from 
l£  oz.  to  2  oz.     If  we  adopt  the  lower  of  these  numbers,  we  shall  find  that, 
reckoning  75  pulsations  of  the  Heart  to  a  minute,  112  oz.,  or  7  Ibs.,  of  blood 
pass  through   each  ventricle  in  that  time;  and,  on  the   higher  estimate,  150 
oz.,  or  9  Ibs.  6  oz.,  would  pass  through  in  the  same  period.     Now  the  whole 
quantity  of  blood  contained  in  the  human  body,  according  to  the  estimate  of 
Haller  (which  is  considered  by  Dr.  Allen  Thomson  to  be  near  the  truth),  is 
about  one-fifth  of  the  weight  of  the  body,  or  28  Ibs.  in  a  person  weighing 
140  Ibs.*     This  quantity  would  pass  through  the  Heart,  therefore,  in  four 
minutes,  on  the  lower  of  the  two  preceding  estimates,  or  in  three  minutes  on 
the  higher;  and  would  circulate  afresh,  fifteen  or  twenty  times  in  an  hour.    It 
would  appear,  however,  that  this  estimate  of  the  rapidity  of  the  circulation  is 
very  far  from  the  truth  ;  for  recent  experiments  have  shown,  that  substances 
introduced  into  the  Venous  circulation,  may  be  detected  in  the  remotest  parts 
of  the  Arterial  circulation,  even  in  animals  larger  than  Man,  in  less  than  half' 
a  minute. — The  earliest  of  such  experiments  were  those  of  Hering,t  who  en- 
deavoured to  ascertain  the  rapidity  of  the  circulation,  by  introducing  Prussiate 
of  Potash  into  one  part  of  the  system,  and  drawing  blood  from  another.     He 
states  that  he  detected  this  salt,  in  blood  drawn  from  one  of  the  Jugular  veins 
of  the  Horse,  within  20  or  30  seconds  after  it  had  been  introduced  into  the 
other ;  in  which  brief  space  the  blood  must  have  been  received  by  the  Heart, 
must  have  been  transmitted  through  the  Lungs,  have  returned  to  the  Heart 
again,  have  been  sent  through  the  Carotid  artery,  and  have  traversed  its  ca- 
pillaries.    From  experiments  of  a  similar  nature  upon  other  veins,  he  states 
that  the  salt  passed  from  the  Jugular  vein  into  the   Saphena  in  20  seconds ; 
into  the  Masseteric  artery  in  from  15  to  20  seconds ;  into  the  External  Max- 
illary artery  in  from  10  to  25  seconds  ;  and  into  the  Metatarsal  artery  in  from 
20  to  40  seconds.     An  attempt  has  been  made   to  invalidate  the  inference 
which  seems  inevitably  to  flow  from  these  experiments,  in  regard  to  the  rate 
of  the  circulation,  by  attributing  the  transmission  of  the  salt  to  the  permea- 
bility of  the  animal  tissues  ;J  but  it  has  never  been  shown,  that  even  Prussiate 
of  Potash  (which  is  probably  more  transmissible  through  this  channel  than 
any  other  salt),  can  be  carried  from  one  part  to  another,  with  a  rapidity  at  all 
proportional  to  this.     The  only  mode  in  which   this  property  can  be  con- 
ceived materially  to  facilitate  the  transmission  of  the  salt  through  the  vascular 
system,  would  be  by  allowing  it  to  pass  through  the  septum  of  the  auricles, 
and  thus  to  make  its  way  from  the  right  to  the  left  side  of  the  heart,  without 
passing  through  the  pulmonary  circulation ;  and  this  it  could  scarcely  do,  to 
the  large  amount  which  is  evidently  transmitted,  in  so  short  a  time. 

725.  The  experiments  of  Hering  have  been  recently  fully  confirmed  by 

*  Valentin's  estimate,  founded  upon  different  data,  closely  corresponds  with  this, 
t  Tiedemann's  Zeitschrift,  vol.  iii.  p.  85. 
j  See  Dr.  Allen  Thomson,  loc.  tit. 

47 


554  OF  THE  CIRCULATION  OF  BLOOD. 

those  of  Mr.  Blake;*  who  varied  them  by  employing  different  substances, 
and  took  other  precautions  against  sources  of  fallacy.  Ten  seconds  after 
having  injected  a  solution  of  Nitrate  of  Baryta  into  the  Jugular  vein  Of  ahorse, 
he  drew  blood  from  the  Carotid  artery  of  the  opposite  side ;  after  allowing 
this  to  flow  for  five  seconds,  he  substituted  another  vessel,  which  received  the 
blood  that  flowed  during  the  five  ensuing  seconds ;  and  the  blood  that  flowed 
after  the  twentieth  second,  by  which  time  the  action  of  the  Heart  had  stopped, 
was  received  into  a  third  vessel.  These  different  specimens  were  carefully 
analyzed.  No  trace  of  Baryta  could  be  detected  in  the  blood,  which  had 
escaped  from  the  artery  between  the  tenth  and  fifteenth  second  after  the  in- 
jection of  the  poison  ;  but  in  that  which  was  drawn  between  the  fifteenth  and 
the  twentieth  second,  the  salt  was  found  to  be  present,  and  in  greater  abun- 
dance than  in  the  blood  which  had  subsequently  flowed.  Moreover,  the 
coincidence  between  the  cessation  of  the  Heart's  action,  and  the  diffusion  of 
the  salt  through  the  arterial  blood,  bear  a  striking  correspondence  ;  and  it  may 
be  hence  inferred,  that  the  arrestment  of  its  muscular  movement  is  due  to  the 
effect  of  this  agent  upon  its  tissue,  when  immediately  operating  upon  it, 
through  the  capillaries  of  the  coronary  artery.  This  conclusion  is  borne  out 
by  a  variety  of  other  experiments ;  which  show  that  the  time  of  the  agency 
of  other  poisons,  that  suddenly  check  the  Heart's  action  (which  is  the  espe- 
cial property  of  mineral  poisons),  nearly  coincides,  in  different  animals,  with 
that  which  is  required  to  convey  them  into  the  Arterial  capillaries.  And  it 
seems  to  derive  full  confirmation  from  the  fact,  that  poisons,  which  act  locally 
on  other  parts,  give  the  first  indications  of  their  operation,  in  the  same  period 
after  they  have  been  introduced  into  the  Venous  circulation.  Thus,  in  the 
•  Horse,  the  time  that  is  required  for  the  blood  to  pass  from  the  Jugular  vein 
into  the  capillary  terminations  of  the  Coronary  arteries,  is  16  seconds ;  as  is 
shown  by  the  power  of  Nitrate  of  Potass  to  arrest  the  Heart's  action  within 
that  time  :  and  Nitrate  of  Strychnia,  injected  into  a  vein,  gave  the  first  mani- 
festation of  its  action  on  the  Spinal  Cord,  in  precisely  the  same  number  of 
seconds.  In  the  Dog,  the  Heart's  action  was  arrested  by  the  Nitrate  of  Potass 
in  11  or  12  seconds;  and  the  tetanic  convulsions  occasioned  by  Strychnia, 
also  commenced  in  12  seconds.  In  the  Fowl,  the  former  period  was  6 
seconds,  and  the  latter  65  ;  in  the  Rabbit,  the  first  was  4,  and  the  other  4£ 
seconds.  From  these  experiments,  it  seems  difficult  to  resist  the  conclusion, 
that  the  rapidity  of  the  Circulation  is  very  much  underrated,  in  any  estimate 
that  we  found  upon  the  capacity  of  the  Heart,  and  its  number  of  pulsations  in 
a  given  time ;  and  that  some  other  force,  than  its  contractions,  must  have  a 
share  in  producing  the  movement  of  the  blood  through  the  vessels. 

726.  The  force  with  which  the  Heart  propels  the  Blood,  may  be  estimated 
in  two  ways; — either  by  ascertaining  the  height  of  the  column  of  that  fluid, 
which  its  contractile  action  will  support ; — or  by  causing  the  blood  to  act 
upon  a  shorter  column  of  mercury. — The  former  method  was  the  one  adopted 
by  Hales,  who  introduced  a  long  pipe  into  the  Carotid  artery  of  a  Horse,  and 
found  that  the  blood  would  sometimes  rise  in  it  to  the  height  of  10  feet.  From 
parallel  experiments  upon  Sheep,  Oxen,  Dogs,  and  other  animals,  and  by 
comparing  the  calibre  of  their  respective  vessels  with  that  of  the  Human  aorta, 
Hales  concluded,  that  the  usual  force  of  the  Heart  in  Man  would  sustain  a 
column  of  blood  7£  feet  high,  the  weight  of  which  would  be  about  4  Ibs.  6 
oz. — The  second  method  is  that  more  recently  adopted  by  Poisseuille ;  and 
the  instrument  which  he  contrived  for  carrying  it  into  practice  (termed  by  him 
the  Haemadynamometer)  has  been  the  means  of  aiding  many  valuable  inqui- 
ries on  the  physiology  of  the  Circulation.  The  result  of  his  experiments  is 

*  Edinb.  Med.  and  Surg.  Journal,  Oct.  1841. 


ACTION  OF  THE  HEART. 


555 


very  nearly  the  same  as  that  of  Hales  ;  his  estimate  of  the  force,  with  which 
the  blood  is  propelled  into  the  Aorta,  being  4 


Ibs.  3  oz.  The  backward  pressure  upon  the 
walls  of  the  Heart,  or  in  other  words  the 
force  which  they  have  to  overcome  in  pro- 
pelling the  blood,  is  properly  estimated,  by 
multiplying  the  pressure  of  blood  in  the  aorta, 
into  the  surface  of  a  plane  passing  through 
the  base  and  apex  of  the  left  ventricle  ;  by 
which  calculation  it  is  found  to  be  about  13 
Ibs.*  The  pressure  appears,  from  the  experi- 
ments of  Poisseuille,  to  be  very  nearly  equal 
for  equal  surfaces,  throughout  the  larger  arte- 
rial branches ;  since  it  diminishes  regularly 
in  proportion  to  their  calibre;  in  the  radial 
artery  at  the  wrist,  it  was  estimated  by  him 
at  4  drachms. 

727.  The  number  of  contractions  of  the 
Heart  in  a  given  time,  is  liable  to  great  varia- 
tion, within  the  limits  of  ordinary  health, 
from  several  causes  ;  the  chief  of  these  are, 
diversities  of  Age,  of  Sex,  of  Muscular  exer- 
tion, of  the  condition  of  the  Mind,  of  the  state 
of  the  Digestive  system,  and  of  the  Period  of 
the  day. 

a.  Putting  aside  the  other  causes  of  uncertainty,  the 
following  table  may  be  regarded  as  an  approximation 
to  the  average  frequency  of  the  Pulse,  at  the  several 
ages  specified  in  it. 


[Fig.  213. 


In  the  foetus  in  utero 
Newly -born  infant 
During  the  First  year 
During  the  Second  year 
During  the  Third  year    , 
About  the  Seventh  year 
Age  of  Puberty 
Manhood   . 


BEATS  PER  MINUTE. 

.  140  —  150 

.  .  130  —  140 

.  115—130 

.  .  100  —  115 

90  —  100 

.  '  .   85—90 

80—  85 

.  .   70—80 

50—  65 


Hsemadynamometer  of  Poisseuille.  A 
bent  glass  tube,  filled  with  mercury  in 
the  lower  part,  a  d  e.  The  horizontal 
part  6,  is  provided  with  a  brass  head, 
which  fits  into  the  artery.  A  small 
quantity  of  a  solution  of  the  carbonate 
of  soda  is  interposed  between  the  mer- 
cury and  the  blood,  to  prevent  its  coagu- 
lation. When  the  blood  presses  on  the 
fluid  in  the  horizontal  limb,  the  rise  of 
the  mercury  towards  e,  measured  from 
the  level  to  which  it  has  fallen  towards 
a,  gives  the  pressure  under  which  the 
blood  moves.] 


Old  age  .... 

b.  The  difference  caused  by  sex  is  very  considerable, 
especially  in  adult  age;  it  appears  from  the  inquiries 
of  Dr.  Guy,t  that  the  pulse  of  the  adult  Female  ex- 
ceeds in  frequency  the  pulse  of  the  adult  Male,  at  the 
same  mean  age,  by  from  10  to  14  beats  in  a  minute. 

c.  The  effect  of  muscular  exertion  in  raising  the  pulse  is  well  known ;  as  is  also  the  fact, 
which  is  one  exemplification  of  it,  that  the  pulse  varies  considerably  with  the  posture  of  the 
body.     The  amount  of  this  variation  has  been  made  the  subject  of  extensive  inquiry  by  Dr. 
Guy ;  and  the  following  are  his  results.     In  100  healthy  Males,  of  the  mean  age  of  27  years, 
in  a  state  of  rest,  the  average  frequency  of  the  pulse  was,  when  standing,  79, — when  sitting, 
70, — and  when  lying,  67  per  minute.     Several  exceptions  occurred,  however,  to  the  general 
law;  and  when  these  were  excluded,  the  average  numbers  were, — standing,  81, — sitting, 
71, — and  lying',  66;   so  that  the  difference  between  standing  and  sitting  was  10  beats,  or 
l-8th  of  the  whole;  the  difference  between  sitting  and  lying  was  5  beats,  or  1-1 3th  of  the 
whole;  and  the  difference  between  standing  and  lying  was  15  beats,  or  l-5th  of  the  whole. 
In  50  healthy  Females,  of  the  same  mean  age,  the  average  pulse,  when  standing,  was  89, — 


*  The  extreme  latitude  of  the  estimates  which  have  been  made  of  this  force,  has  been  a 
subject  of  not  undeserved  ridicule.  Borelli imagined  it  to  be  180,000  Ibs.;  whilst  by  Keill  it 
was  supposed  to  be  no  more  than  from  5  to  8  ounces. 

f  Guy's  Hospital  Reports,  vol.  iii.  p.  312. 


556  OF  THE  CIRCULATION  OF  BLOOD. 

when  sitting,  81, — and  when  lying,  80.  When  the  exceptions  (which  were  more  numerous 
in  proportion  than  in  males)  were  excluded,  the  averages  were,  standing,  91, — sitting,  84, — 
lying,  79;  the  difference  between  standing  and  sitting  was  thus  7  beats,  or  1-1 3th  of  the 
whole;  that  between  sitting  and  lying  was  4,  or  1-2 1st  of  the  whole;  and  that  between 
standing  and  lying  was  11,  or  1 -8th  of  the  whole.  In  both  sexes,  the  effect  produced  by 
change  of  posture  increases  with  the  usual  frequency  of  the  pulse;  whilst  the  exceptions  to 
the  general  rule  are  more  numerous,  as  the  pulse  is  less  frequent.  The  variation  is  tem- 
porarily increased  by  the  muscular  effort,  involved  in  the  absolute  change  of  the  posture ; 
and  it  is  only  by  the  use  of  a  revolving  board,  by  which  the  position  of  the  body  can  be 
altered,  without  any  exertion  on  the  part  of  the  subject  of  the  observation,  that  correct  results 
can  be  obtained.  That  the  difference  between  standing  and  sitting  should  be  greater  than 
that  between  sitting  and  lying,  is  just  what  we  should  expect ;  when  we  compare  the 
amount  of  muscular  effort  required  in  the  maintenance  of  the  two  former  positions  respect- 
ively. 

d.  The  Pulse  is  well  known  to  be  much  accelerated  by  Mental  excitement,  especially  by 
that  of  the  Emotions;  it  is  also  quicker  during  Digestion;  but  on  neither  of  these  points  can 
any  exact  numerical  statement  be  given. 

e.  The  diurnal  variation  of  the  pulse,  however,  has  been  made  the  subject  of  observation 
by  Dr.  Guy  ;*  and,  as  the  results  of  his  inquiries  have  much  interest,  although  (from  having 
been  made  only  on  his  own  person)  they  may  ultimately  require  some  modification,  they 
will  be  here  stated.     "  1 .  The  pulse  of  a  healthy  male  in  a  state  of  rest,  unexcited  either  by 
food  or  exercise,  is  most  frequent  in  the  morning,  and  gradually  diminishes  as  the  day  ad- 
vances.    2.  The  pulse  diminishes  in  frequency  more  rapidly  in  the  evening,  than  in  the 
morning.     3.  The  diminution  in  the  frequency  of  the  pulse  (after  excitement)  is  more  regu- 
lar and  progressive  in  the  evening  than  in  the  morning.     4.  The   effect  of  food  is  greater 
and  more  lasting  in  the  morning,  than  in  the  evening ;  and  in  some  instances,  the  same  food, 
which  in  the  morning  produces  an  effect  considerable  both  in  amount  and  duration,  has  no 
effect  whatever  in  the  evening."     It  may  be  hoped  that,  ere  long,  this  interesting  and  im- 
portant subject  will  receive  further  elucidation. 

[/.  Dr.  Valleix  has  recently  published  a  series  of  interesting  observations  on  the  fre- 
quency of  the  pulse  in  newly-born  infants,  and  in  children  aged  from  seven  months  to  six 
years.  He  obtained  the  following  results:  1.  At  birth  the  pulse  is  less  frequent  than  at  six 
months;  the  number  of  beats  in  a  minute  may  be  stated  with  considerable  exactness  to  be 
between  90  and  100.  2.  Increase  of  temperature,  even  in  the  slightest  degree,  invariably 
produces  a  notable  acceleration  of  the  pulse.  The  exact  ratio  between  the  degree  of  eleva- 
tion of  temperature  and  the  increase  in  the  frequency  of  the  pulse,  is  not  yet  accurately 
ascertained.  3.  Although  the  observations  of  Dr.  Valleix  show  a  progressive  diurnal  diminu- 
tion in  the  frequency  of  the  pulse,  still,  he  thinks,  it  would  be  premature  to  conclude  that 
these  facts  support  those  of  Dr.  Guy.  Dr.  Valleix  examined  his  patients  in  the  morning 
after  they  had  been  eating,  and  to  this  fact,  he  thinks,  should  be  attributed  the  acceleration 
of  the  pulse  in  the  early  part  of  the  day,  and  its  subsequent  diminution  towards  evening. 
4.  The  slightest  muscular  effort  in  children  is  sufficient  to  augment  considerably  the  number 
of  pulsations.  The  same  is  true  of  any  moral  emotion.  5.  The  influence  of  sex  on  the 
pulse  is  very  marked  in  young  children.  The  pulse  is  much  more  frequent  in  young  girls 
than  in  boys  of  the  same  age.  6.  During  sleep  there  is  a  decided  diminution  in  the  number 
of  beats.  7.  Between  7  and  27  months  there  is  no  sensible  change  in  the  frequency  of  the 
pulse.  Its  mean  may  be  stated  at  126  beats  in  the  minute,  without  distinction  of  sex.  If 
sex  be  considered,  it  would  be  121  for  males  and  128  for  females.  These  numbers  express 
the  frequency  of  the  pulse  at  this  age  under  ordinary  circumstances,  but  if  a  state  of  perfect 
calm  is  supposed,  the  numbers  would  be  119  for  the  males,  and  124  for  females.  8.  After 
some  observations,  not  very  numerous,  however,  the  pulse  would  appear  to  range  a  little 
above  100  till  six  years  of  age.  9.  The  mean  number  of  inspirations  in  a  minute  in  chil- 
dren aged  from  7  months  to  two  years  and  a  half,  is  between  30  and  32,  and  is  to  number 
of  pulsations  :  :  1  :  4. — M.  C.J 

3. — Movement  of  the  Blood  in  the  Arteries  and  Capillaries. 

728.  We  have  next  to  consider  the  influence  of  the  Arterial  tubes  on  the 
flow  of  Blood  through  them.  This  influence  is  exerted  by  the  middle  or 
fibrous  coat,  which  alone  is  possessed  of  contractile  properties.  We  find  in 
this  coat,  a  layer  of  annular  fibres,  possessing  no  small  resemblance  to  that 
of  which  the  muscular  coat  of  the  alimentary  canal  is  composed.  On  the  out- 

*  Op.  cit,  vol.  iv.  p.  69. 


MOTION  OF  THE  BLOOD  IN  THE  ARTERIES.  557 

side  of  this,  is  a  layer  of  yellow  elastic  tissue,  which  is  much  thicker  in  the 
larger  arteries,  in  proportion  to  their  size,  than  in  the  smaller.  To  this  last 
tissue  is  due  the  simple  elasticity  of  the  arterial  walls,  which  is  a  physical 
property  that  persists  after  death,  until  a  serious  change  takes  place  in  their 
composition  :  whilst  to  the  one  first  mentioned,  we  are  to  attribute  the  property 
which  they  unquestionably  possess — in  common  with  proper  muscular  tissue, 
— of  contracting  on  the  application  of  a  stimulus,  so  long  as  their  vitality  re- 
mains. These  two  endowments  exist,  in  various  proportional  degrees,  in  the 
different  parts  of  the  Arterial  system.  Thus  it  was  justly  remarked  by  Hun- 
ter, that  elasticity,  being  the  property  by  which  the  interrupted  force  of  the 
Heart  is  made  equable  and  continuous,  is  most  seen  in  the  large  vessels  more 
immediately  connected  with  that  organ.  On  the  other  hand,  the  contractility 
is  most  observable  in  the  smaller  vessels,  where  it  is  more  required  for  regu- 
lating the  flow  of  blood  towards  particular  organs. 

729.  It  is  easily  shown  that  the  action  of  the  Elasticity  of  the  Arterial 
tubes,  is  one  of  a  purely  physical  character;  and  that  its  purpose  is  to  con- 
vert the  intermitting  impulses,  which  the  fluid  receives  from  the  heart,  into  a 
continuous  current.     The  former  are  very  evident  in  the  larger  trunks ;  but 
they  diminish  with  the  subdivision  of  these,  until  they  entirely  disappear  in 
the  capillaries,  in  which  the  stream  is  usually  equable  or  nearly  so.     We  may 
imagine  a  powerful  forcing-pump  injecting  water,  by  successive  strokes,  into 
a  system  of  tubes  with  unyielding  walls  ; — the  flow  of  fluid  at  the  farther  ex- 
tremities of  these  tubes,  would  be  as  much  interrupted  as  its  entrance  into 
them.     But  if  an   air-vessel  (like  that  of  a  fire-engine)  were  placed  at  their 
commencement,  the  flow  would  be  in  a  great  degree  equalized;  since  a  part 
of  the  force  of  each  stroke  would  be  spent  upon  the  compression  of  the  air 
included  in  it;  and  this  force  would  be  restored  by  the  elasticity  of  the  air, 
during  the  interval,  which  would  propel  the  stream,  until  directly  renewed  by 
the  next  impulse.     A  much  closer  imitation  of  the  natural  apparatus  would 
be   afforded,  by  a  pipe  which  had  elastic  walls  of  its   own ;  if  water  were 
forced  by  a  syringe  into  a  long  tube  of  caoutchouc,  for  example,  the  stream 
would  be  equalized  before  it  had  proceeded  far.     This  effect  is  found  to  be 
accomplished,  at  any  point  of  the  Arterial  circulation,  in  a  degree  proportionate 
to  its  distance  from  the  Heart;  and  it  is  another  effect  of  the  same  cause,  that 
the  pressure  of  the  blood  upon  the  wall  of  the  arteries  (as  shown  by  the  ex- 
periments of  Poisseuille)  is  nearly  the  same  all  over  the  system.     It  is  to  the 
distension   of  the  arterial  tubes,  both  in  their  length  and  calibre,  that  their 
pulsation  is  due.     Their  elongation  is  the  more  considerable  of  the  two  effects ; 
and  it  causes  the  artery  to  be  lifted  from  its  seat  and  to  become  curved.    The 
transverse  dilatation  has  been  denied  by  some  physiologists ;  but  it  has  been 
recently  proved  to  take  place,  by  an  ingenious  experiment  of  Poisseuille's. 
The  increase  of  capacity,  however,  is  not  more  than  l-10th ;  so  that  the  in- 
crease of  diameter  will  not  be  so  much  as  l-20th, — a  quantity  scarcely  per- 
ceptible  to    ordinary  measurement.      The  transmission   of  the   pulse-wave 
through  the  whole  system  is  not  instantaneous,  but  takes  place  in  an   appre- 
ciable time.     The  pulsation  of  the  large  arteries  near  the  Heart,  is  synchron- 
ous with  the  Ventricular  systole  ;  but  that  of  other  arteries  is  somewhat  later, 
— the  difference  varying  with  their  distance,  and  amounting  in  some  instances 
to  between  l-6th  and  l-7th  of  a  second. 

730.  It  has  been  denied  by  many  Physiologists,  that  the  middle  coat  of  the 
Arteries  possesses  any  property  which  can  be  likened  to  Muscular  Contrac- 
tility;  and  it  will  therefore  be  desirable  to  enter  somewhat  in  detail  into  the 
question.     That  it  cannot  be  readily  stimulated  to  contraction,  through  the 
medium  of  its  nerves,  is  universally  admitted ;  but  the  same  is  the  case  in 
regard  to  the   Muscular  coat  of  the  alimentary  canal,  which  contracts  most 

47* 


558  OF  THE  CIRCULATION  OF  BLOOD. 

vigorously  on  the  direct  application  of  stimuli  to  itself;  and  Valentin  and 
others  have  recently  succeeded  in  producing  evident  contractions  in  the  Aorta, 
by  irritation  of  the  Sympathetic  nerve,  and  of  certain  roots  of  the  Spinal 
nerves.  Further,  although  many  experiments  have  failed  in  producing  con- 
tractions of  this  tissue,  by  stimuli  directly  applied  to  itself,  yet  others  have 
distinctly  witnessed  them;  and,  in  any  question  of  this  kind,  the  positive 
evidence  must  be  held  to  outweigh  the  negative.  Thus  Verschuir  states,  that 
he  has  seen  arteries  contract,  when  stimulated  by  the  mineral  acids,  by  elec- 
tricity, and  by  the  application  of  the  point  of  a  scalpel.  Dr.  Thomson  also 
saw  them  contract,  on  the  application  of  ammonia,  and  when  punctured  with 
the  point  of  a  fine  needle,  in  the  living  body.  It  has  been  ascertained  by  the 
direct  and  careful  experiments  of  Poisseuille,  that,  when  the  artery  is  dilated 
by  the  blood  injected  into  it  from  the  heart,  it  reacts  with  a  force  superior  to 
the  impressing  impulse ;  and  he  has  also  shown  that,  if  a  portion  of  an  artery 
from  an  animal  recently  dead  (in  which  the  vital  contractility  seems  to  be 
preserved),  and  one  from  an  animal  that  has  been  dead  some  days  (in  which 
nothing  but  the  elasticity  remains),  be  distended  with  an  equal  force,  the  for- 
mer becomes  much  more  contracted  than  the  latter,  after  the  distending  force 
is  removed. 

731.  Several  experiments  also  indicate  the  existence  of  that  power  of  slow 
contraction  in  the  arteries,  which  has  been  distinguished  by  the  appellation 
Tonicity  ;  but  which  does  not  seem  anything  else  than  a  particular  manifesta- 
tion of  the  general  property  of  vital  contractility,  and  is  certainly  of  a  nature 
quite  distinct  from  ordinary  elasticity.  Thus,  when  a  ligature  is  placed  upon 
an  artery  in  a  living  animal,  the  part  of  the  artery  beyond  the  ligature  becomes 
gradually  smaller,  and  is  emptied  to  a  certain  degree,  if  not  completely,  of  the 
blood  it  contained.  Again,  when  part  of  an  artery  in  a  living  animal  is  isolated 
by  means  of  two  ligatures,  and  is  punctured,  the  blood  issues  from  the  orifice, 
and  the  inclosed  portion  of  the  artery  is  almost  completely  emptied  of  its 
contents.  The  exposure  of  arteries  to  the  air  was  found  by  Hunter  to  occa- 
sion their  contraction,  to  such  an  extent,  that  obliteration  of  their  tube  was 
the  result ;  and  this  statement  has  been  subsequently  confirmed.  Further, 
every  Surgeon  knows,  that  the  contraction  of  divided  arteries  is  an  efficient 
means  of  the  arrest  of  hemorrhage  from  them,  especially  when  they  are  of 
small  calibre ;  so  that,  in  the  case  of  the  temporal  artery,  for  example,  the 
complete  division  of  the  tube  is  often  the  readiest  means  of  checking  the  flow 
of  blood  from  it,  when  it  has  been  once  wounded.  This  contraction  is  much 
greater  than  could  be  accounted  for  by  the  simple  elasticity  of  the  tissue  ;  and 
is  more  decided  in  small,  than  in  large  vessels.  The  empty  condition  of  the 
arteries,  generally  found  within  a  short  time  after  death,  seems  to  be  in  part 
due  to  the  same  cause ;  since  their  calibre  is  usually  much  diminished,  and  is 
sometimes  completely  obliterated.  A  remarkable  example  of  the  same  slow 
contraction,  is  that  which  takes  place  in  the  end  of  the  upper  portion  of  an 
arterial  trunk,  when  the  passage  of  blood  through  it  is  interrupted  by  a  liga- 
ture ;  for  the  current  of  blood  then  passes  off  by  the  nearest  large  lateral 
branch  ;  and  the  tube  of  the  artery  shrivels,  and  soon  becomes  impervious, 
from  the  point  at  which  the  ligature  is  applied,  back  to  the  origin  of  that 
branch.  This  last  fact  is  important,  as  proving  how  little  influence  the  vis  a 
tergo  possesses  over  the  calibre  of  arterial  tubes  ;  since,  without  any  interrup- 
tion to  the  pressure  of  blood  occasioned  by  it,  the  tube  becomes  impervious. — 
It  is  to  the  moderate  action  of  the  Tonicity  of  arteries,  that  their  contraction 
upon  the  stream  of  blood  passing  through  them  (which  serves  to  keep  the 
tubes  always  full)  is  due.  If  the  tonicity  be  excessive,  the  pulse  is  hard  and 
wiry ;  but  if  it  be  deficient,  the  pulse  is  very  compressible,  though  bounding, 
and  the  flow  of  blood  through  the  arteries  is  retarded.  Dr.  Williams  has 


MOTION  OF  THE  BLOOD  IN  THE  ARTERIES.  559 

performed  some  ingenious  experiments,  which  prove  that  the  force  required 
to  propel  fluid  through  a  tube,  whose  sides  are  yielding,  is  very  much  greater 
than  that  which  will  carry  it  through  a  tube  of  even  smaller  size,  with  rigid 
parietes ;  consequently,  a  loss  of  tonicity  in  the  blood-vessels  retards  the  flow 
of  blood  through  them  ;  whilst  an  increase  hastens  it.  The  Tonicity  of  the 
arteries  differs  from  their  ordinary  Contractility,  in  being  augmented  by  cold, 
and  diminished  by  warmth.  Hence  cold  and  heat  are  two  most  valuable 
remedial  agents,  when  this  property  is  deficient  or  in  excess. 

732.  It  is  still  to  be  inquired,  in  what  manner  the  Contractility  of  the  Arte- 
ries is  to  be  regarded  as  influencing  the  flow  of  Blood  through  them.  It  is  at 
once  evident,  that  any  general  contraction  of  the  arterial  tubes  would  have 
rather  the  effect  of  opposing,  than  of  assisting  the  flow ;  but  if  the  fibrous 
coat  of  the  Arteries  is  in  some  degree  disposed  to  the  alternate  contraction  and 
relaxation,  which  are  so  remarkable  in  the  Heart,  they  may  exert  a  force  which 
shall  be  supplementary  to  that  of  the  Heart's  impulse, — relaxing  to  receive 
the  blood  from  it,  and  contracting  upon  their  contents,  with  a  power  superior 
to  that  by  which  they  were  distended.  It  is  difficult  to  say  whether  or  not 
this  be  the  case  ;  though  there  would  certainly  appear  some  evidence  in  favour 
of  the  supposition.  The  loss  of  the  Heart's  power  over  the  currents  of  blood, 
in  proportion  to  their  degree  of  subdivision,  occasioned  by  the  increased  fric- 
tion to  which  they  will  be  subjected,  would  seem  to  require  some  compensat- 
ing power,  in  order  that  the  perfect  equality  of  pressure  may  be  obtained 
which  has  been  spoken  of  as  existing  in  all  parts  of  the  arterial  system.  In 
no  other  way  than  this  can  the  fibrous  coat  of  the  Arteries  be  regarded  as 
having  any  propulsive  power  over  their  contents ;  except  by  a  peristaltic  or 
vermicular  movement,  resembling  that  which  takes  place  in  the  alimentary 
canal ;  and  of  such  there  is  no  evidence  whatever. — A  very  important  use 
may  be  assigned  to  this  muscular  coat,  which  has  been  generally  overlooked 
by  Physiologists, — that  of  regulating  the  diameter  of  the  tubes,  in  accord- 
ance with  the  quantity  of  blood  to  be  conducted  through  them  to  any  part ; 
which  will  depend  upon  its  peculiar  circumstances  at  the  time.  Such  local 
changes  are  continually  to  be  observed,  in  the  various  phases  of  normal  life, 
as  well  as  in  diseased  states ;  and  they  will  be  found  to  be  constantly  in  har- 
mony with  the  particular  condition  of  the  processes  of  Nutrition,  Secretion, 
&c.,  to  which  the  Capillary  circulation  ministers.  Of  this  kind  are  the  en- 
largement of  the  trunks  of  the  Uterine  and  Mammary  arteries,  at  the  epochs 
of  pregnancy  and  lactation  ; — the  enlargement  and  strongly-increased  pulsa- 
tion of  the  Radial  artery,  when  there  is  any  active  inflammation  in  the  thumb  ; 
— the  enormous  diameter  which  the  Spermatic  artery  will  attain,  when  the 
testicle  is  greatly  increased  in  size  by  diseased  action ;  and  many  other  simi- 
lar phenomena.  In  such  cases,  it  cannot  be  the  action  of  the  Heart  that  in- 
creases the  calibre  of  the  vessels ;  since  this  is  commonly  unaltered,  and  is 
itself  unable,  as  we  have  just  seen,  even  to  maintain  their  permeability.  It 
must,  therefore,  be  by  a  power  inherent  in  themselves,  that  their  dilatation  is 
effected.  The  minute  distribution  of  the  Sympathetic  nerve  upon  the  walls 
of  the  arteries, — the  known  power  which  this  has  of  producing  contractions, 
alike  in  their  fibrous  coat,  and  in  the  muscular  tunic  of  the  intestinal  canal, — 
and  various  phenomena,  which  indicate  the  power  of  certain  states  of  mind 
over  the  dimensions  of  the  arteries,  in  particular  parts  of  the  body  at  least, — 
render  it  highly  probable  that  the  calibre  of  the  arteries  is  regulated  in  no  in- 
considerable degree  through  its  intervention.*  The  permanent  dilatation, 
however,  which  is  seen  in  the  arteries  supplying  parts  that  are  undergoing 

*  For  Anatomical  evidence  to  this  effect,  see  Henle  on  the  Contractility  of  the  Blood- 
vessels, in  Casper's  Wochenschrift,  May  1840,  and  Brit,  and  For.  Med.  Rev.,  vol.  x.  p.  551. 


560  OF  THE  CIRCULATION  OF  BLOOD. 

enlargement,  must  be  due,  not  to  simple  dilatation  merely,  but  to  increased 
nutrition ;  since  we  find  that  their  walls  are  thickened  as  well  as  extended. 
And,  on  the  other  side,  when  slow  contraction  occurs  in  these  tubes,  as  a 
consequence  of  disease,  it  must  be  in  part  occasioned  by  atrophy;  since 
their  nutrition  is  so  much  diminished,  that  in  time  they  almost  entirely  disap- 
pear,— a  portion  of  a  large  artery  occasionally  shriveling  into  a  ligamentous 
band. 

733.  We  now  come  to  the  last  head  of  the  inquiry  into  the  powers  which 
convey  the  blood  through  the  capillary  system ; — that,  namely,  which  con- 
cerns the  agencies  existing  in  the  Capillaries  themselves.     Many  discussions 
on  this  subject  may  be  found  in  Physiological  writings  ;  and  it  has  so  imme- 
diate a  bearing  on  one  of  the  most  important  questions  in  Pathology, — the 
nature  of  Inflammation, — that  it  deserves  the  fullest  attention.     The  chief 
question  in  debate,  is  the  degree  in  which  the  Capillary  circulation  is  influ- 
enced by  any  other  agency  than  the  contractile  power  of  the  Heart  and  Arte- 
rial system ; — some  Physiologists   maintaining  that  this  alone  is   sufficient 
to  account  for  all  the  phenomena  of  the  Capillary  circulation; — and  others 
asserting  that  it  is  necessary  to  admit  some  supplementary  force,  which  may 
be  exerted  either  to  assist,  retard,  or  regulate  the  flow  of  blood  from  the  Arte- 
ries into  the  Veins.     We  shall  first  consider  what  evidence  there  is  of  the 
existence  of  any  such  force;  and,  when  led  to  an  affirmative  conclusion,  we 
shall  examine  into  its  nature. — No  physiological  fact  is  more  clearly  proved 
than  the  existence,  in  the  lower  classes  of  Animals,  as  well  as  in  Plants,  of 
some  power  independent  of  a  vis  a  tergo,  by  which  the  circulating  fluid  is 
caused  to  move  through  their  vessels  (§§  712 — 716).     This  power  seems  to 
originate  in  themselves,  and  to  be  closely  connected  with  the  state  of  the 
Nutritive  and  Secreting  processes  :  since  anything  which  stimulates  these  to 
increased  energy,  accelerates  the  circulation ;  whilst  any  check  to  them  occa- 
sions a  corresponding  stagnation.     It  may  be  convenient  to  designate  this 
motor  force  by  the  name  of  capillary  power;  it  being  clearly  understood, 
however,  that  no  mechanical  propulsion  is  thence  implied.    On  ascending  the 
Animal  scale,  we  find  the  power  which,  in  the  lower  organisms,  is  diffused 
through  the  whole  system,  gradually  concentrated  in  a  single  part ;  a  new 
force,  that  of  the  Heart,  being  brought  into  operation,  and  the  Circulation 
placed,  in  a  greater  or  less  degree,  under  its  control.     Still  there  is  evidence, 
that  the  movement  of  blood  through  the  capillaries  is  not  entirely  due  to  this  ; 
since  it  may  continue  after  the  cessation  of  the  Heart's  action, — may  itself 
cease  in  particular  organs  when  the  Heart  is  still  acting  vigorously, — and  is 
constantly  being  affected  in  amount  and  rapidity,  by  causes  originating  in  the 
part  itself,  and  in  no  way  affecting  the   Heart.     The  chief  proofs  of  these 
statements  will  now  be  adverted  to. 

734.  When  the  flow  of  blood  through  the  Capillaries  of  a  transparent  part, 
such  as  the  web  of  a  Frog's  foot,  is  observed  with  the  Microscope,  it  appears 
at  first  to  take  place  with  great  evenness  and  regularity.     But  on  watching  the 
movement  for  some  time,  various  changes  may  be  observed,  which  cannot  be 
attributed  to  the  Heart's  influence,  and  which  show  that  a  certain  regulating 
or  distributive  power  exists  in  the  walls  of  the  capillaries,  or  in  the  tissues 
which  they  traverse.     Some  of  these  changes,  involving  variations  in  the  size 
of  the  Capillary  tubes,  have  been  already  referred  to  (§  219).     Others,  how- 
ever, are  manifested  in  great  and  sudden  alterations  in  the  velocity  of  the  cur- 
rent ;  which  cause  a  marked  difference  in  the  rates  of  the  movement  of  the 
blood  through  the  several  parts  of  the  area  under  observation.     Sometimes 
this  variation  extends  even  to  the  entire  reversion,  for  a  time,  of  the  direction 
of  the  movement,  in  certain  of  the  transverse  or  communicating  branches  ;  the 
flow  always  taking  place,  of  course,  from  the  stronger  towards  the  weaker  cur- 


MOTION  OF  THE  BLOOD  IN  THE  ARTERIES.  561 

rent.  Not  unfrequently  an  entire  stagnation  of  the  current,  in  some  particular 
tube,  precedes  this  reversal  of  its  direction.  Irregularities  of  this  kind,  how- 
ever, are  more  frequent  when  the  Heart's  action  is  partially  interrupted  ;  as 
it  usually  is  by  the  pressure,  to  which  the  Tadpole  or  other  animal  must  be 
subjected,  in  order  to  allow  microscopic  observations  to  be  made  upon  its  cir- 
culation. Under  such  circumstances,  the  varieties  in  the  capillary  circulation, 
induced  by  causes  purely  local,  become  very  conspicuous ;  for  when  the 
•whole  current  has  nearly  stagnated,  and  a  fresh  impulse  from  the  heart  re- 
news it,  the  movement  is  not  by  any  means  uniform  (as  it  might  have  been 
expected  to  be)  through  the  whole  plexus  supplied  by  one  arterial  trunk,  but 
is  much  greater  in  some  of  the  tubes  than  it  is  in  others  ;  the  variation  being 
in  no  degree  connected  with  their  size,  and  being  very  different  at  short  in- 
tervals. 

735.  The  movement  of  the  blood  in  the   Capillaries  of  cold-blooded  ani- 
mals, after  complete  excision  of  the  Heart,  has  been  repeatedly  witnessed. 
In  warm-blooded  animals,  this  cannot  be  satisfactorily  established  by  experi- 
ment, since  the  shock  occasioned  by  so  severe  an  operation  much  sooner  de- 
stroys the  general  vitality  of  the  system  ;  but  it  may  be  proved^in  other  ways 
to  take  place.      After  most  kinds  of  natural  death,  the  arterial  system  is 
found,  subsequently  to  the  lapse  of  a  few  hours,  almost  or  completely  emptied 
of  blood  ;  this  is  partly,  no  doubt,  the  effect  of  the  tonic  contraction  of  the 
tubes  themselves  ;  but  the  emptying  is  commonly  more  complete  than  could  be 
thus  accounted  for,  and  must,  therefore,  be  partly  due  to  the  continuance  of 
the  capillary  circulation.     Moreover,  when  death   has  taken  place  suddenly 
from  some  cause  (as,  for  instance,  a  violent  electric  shock),  that  destroys  the 
vitality  of  the  whole  system  at  once,  the  arterial  tubes   are  found  to  contain 
their  due  proportion  of  blood.     Further,  it  has  been  well  ascertained  that  a 
real  process  of  secretion  not  unfrequently  continues   after  general  or  somatic 
death  ;  urine  has  been  poured   out   by  the  ureters,  sweat  excluded  from  the 
skin,  and  other  peculiar  secretions  formed  by  their  glands;  and  these  changes 
could  not  have  taken  place  unless  the  capillary  circulation  were  still  continu- 
ing.    In  the  early  embryonic  condition  of  the  highest  animals,  the  movement 
of  blood  seems  to  be  unquestionably  due  to  some  diffused  power,  independent 
of  any  central  impulsion ;  for  it  may  be  seen  to  commence  in  the   Vascular 
Area,  before  the  development  of  the  Heart.     The  first  movement  is  towards 
instead  of  from,  the  centre  ;  and  even  for  some  time  after  the   circulation  is 
fairly  established,  the  walls  of  the  Heart  consist  merely  of  cells  loosely  at- 
tached together,  and  can  hardly  be  supposed  to  have  any  great  contractile 
power. 

736.  The  last  of  these  facts  may  be  said  not  to  have  any  direct  bearing  on 
the  question,  whether  the  Capillary  power  has  any  existence  in  the  adult  con- 
dition ;  but  the  phenomena   occasionally  presented  by  the  Foetus,  at  a  later 
stage,  appear  decisive.    Cases  are  of  no  very  unfrequent  occurrence,  in  which 
the  heart  is  absent  during  the  whole  of  embryonic  life,  and  yet  the  greater  part 
of  the  organs  are  well  developed.     In  most  or  all  of  these  cases,  however,  a 
perfect  twin  foetus  exists  ;  of  which  the  placenta  is  in  some  degree  united  with 
that  of  the  imperfect  one ;  and  it  has  been  customary  to  attribute  the  circula- 
tion in  the  latter,   to  the  influence   of  the  heart  of  the  former,  propagated 
through    the    placental    vessels.     This    supposition  has  not  been  disproved 
(however  improbable  it  might   seem)   until  recently;  when   a   case  of  this 
kind  occurred,  which  was  submitted  to  the  most  careful  examination  by  an 
accomplished  anatomist  ;*  and  this  decisive  result  was  obtained,  that  it  seemed 

*  See  Dr.  Houston  in  the  Dublin  Medical  Journal,  1837.     An   attempt  has  been  recently 
made  by  Dr.  M.  Hall  (Edinb.  Monthly  Journal,  1843)  to  disprove  Dr. Houston's  inferences; 


562  OF  THE  CIRCULATION  OF  BLOOD. 

impossible  for  the  heart  of  the  twin  foetus  to  have  occasioned  the  movement 
of  blood  in  the  imperfect  one ;  and  that  some  cause  present  in  the  latter,  must 
have  been  sufficient  for  the  propulsion  of  blood  through  its  vessels.  It  was 
a  very  curious  anomaly  in  this  case,  that  the  usual  functions  of  the  Arteries 
and  Veins  must  have  been  reversed;  for  the  Vena  Cava,  receiving  its  blood 
from  the  Umbilical  Vein  nearly  as  usual,  had  no  communication  with  the 
Arterial  system  (the  Heart  being  absent),  except  through  the  Systemic  Capil- 
laries ;  to  which,  therefore,  the  blood  must  have  next  proceeded,  returning  to 
the  placenta  by  the  Umbilical  Artery.  This  view  of  the  course  of  the  blood 
was  confirmed  by  the  fact,  that  the  veins  were  everywhere  destitute  of  valves. 
— It  is  evident,  that  a  single  case  of  this  kind,  if  unequivocally  demonstrated, 
furnishes  all  the  proof  that  can  be  needed,  of  the  existence,  even  in  the  high- 
est animals,  of  a  capillary  power;  which,  though  usually  subordinate  to  the 
Heart's  action,  is  sufficiently  strong  to  maintain  the  circulation  by  itself,  when 
the  power  of  the  central  organ  is  diminished.  In  this,  as  in  many  other  cases, 
we  may  observe  a  remarkable  power  in  the  living  system,  to  adapt  itself  to 
exigencies.  In  the  acardiac  Foetus,  the  capillary  power  supplies  the  place 
of  the  Heart,  up  to  the  period  of  birth  ;  after  which,  of  course,  the  circula- 
tion ceases,  for  want  of  due  aeration  of  the  blood.  It  has  occasionally  been 
noticed,  that  a  gradual  degeneration  in  the  structure  of  the  Heart  has  taken 
place  during  life,  to  such  an  extent  that  scarcely  any  muscular  tissue  could  at 
last  be  detected  in  it ;  without  any  such  interruption  to  the  circulation,  as 
must  have  been  anticipated,  if  it  furnished  the  sole  impelling  force. 

737.  Further,  it  is  a  general  principle,  unquestioned  by  any  Physiologist, 
and  embodied  in  the  ancient  aphorism  Ubi  stimulus,  ibi  fluxus,  that,  when 
there  is  any  local  excitement  to  the  processes  of  Nutrition,  Secretion,  &c.,  a 
determination  of  blood  towards  the  part  speedily  takes  place,  and  the  motion 
of  blood  through  it  is  increased  in  rapidity;  and  although  it  might  be  urged, 
that  this  increased  determination  may  not  be  the  effect,  but  the  cause,  of  the 
increased  local  action,  such  an  opinion  could  not  be  sustained,  without  many 
inconsistencies  with  positive  facts.     For  it  is  known  that  such  local  determi- 
nations may  take  place,  not  only  as  a  part  of  the  regular  phenomena  of  growth 
and  development  (as  in  the   case  of  the  entire  genital  system  at  the  time  of 
puberty  and  of  periodical  heat,  the  uterus  after  conception,  and  the  mammae 
after  parturition),  but  also  as  a  consequence  of  a  strictly  local  cause.     Thus, 
the  student  is  well  aware  that,  after  several  hours'  close  application,  there  is 
commonly  an  increased  determination  of  blood  to  the  brain,  causing  a  sense 
of  oppression,  a  feeling  of  heat,  and  frequently  a  diminished  action  in  other 
parts ;  and,  again,  when  the  capillary  circulation  is  being  examined  under  the 
microscope,  it  is  seen  to  be  quickened  by  moderate   stimuli,  and  equally  re- 
tarded by  depressing  agents.     All  these  facts  harmonize  completely  with  the 
phenomena,  which  are  yet  more  striking  in  the  lower  classes  of  organized 
beings,  and  which  are  evidently  the  results  of  the  same  laws. 

738.  It  is   equally  capable  of  proof,  on  the  other  hand,  that  an  influence 
generated  in  the  Capillaries   may  afford  a  complete  check  to  the  circulation 
in  the  part ;  even  when  the  Heart's  action  is  unimpaired,  and  no  mechanical 
impediment  exists  to  the  transmission  of  blood.     Thus,  cases  of  spontaneous 
gangrene  of  the  lower  extremities  are  of  no  unfrequent  occurrence,  in  which 
the  death  of  the  solid  tissues  is  clearly  connected  with  a  local  decline  of  the 
circulation ;  and  in  which  it  has  been  shown,  by  examination  of  the  limb  after 
its  removal,  that  both  the  larger  tubes  and  the  capillaries  were  completely 

but  a  most  satisfactory  reply  has  been  made  by  Dr.  Houston,  at  the  Meeting  of  the  British 
Association,  August  1843,  and  published  in  the  Dublin  Journal,  Jan.  1844.  See  also  Edinb. 
Med.  and  Surg.  Journ.  July  1844. 


MOTION  OF  THE  BLOOD  IN  THE  CAPILLARIES.  563 

pervious ;  so  that  the  cessation  of  the  flow  of  blood  could  not  be  attributed  to 
any  impediment,  except  that  arising  from  the  cessation  of  some  power  which 
exists  in  the  capillaries,  and  which  is  necessary  for  the  maintenance  of  the 
current  through  them.  The  influence  of  the  prolonged  application  of  Cold 
to  a  part,  may  be  quoted  in  support  of  the  same  general  proposition  ;  for,  al- 
though the  calibre  of  the  vessels  may  be  diminished  by  this  agent,  yet  their 
contraction  is  not  sufficient  to  account  for  that  complete  cessation  of  the  flow 
of  blood  through  them  which  is  well  known  to  occur,  and  to  terminate  in  the 
loss  of  their  vitality.  The  most  remarkable  evidence  on  this  point,  however, 
is  derived  from  the  phenomena  of  Asphyxia,  which  will  be  more  fully  ex- 
plained in  the  succeeding  Chapter.  At  present  it  may  be  stated  as  a  fact, 
which  has  now  been  very  satisfactorily  ascertained,  that,  if  admission  of  air 
into  the  lungs  be  prevented,  the  circulation  through  them  will  be  brought  to  a 
stand,  as  soon  as  the  air  which  they  contain  has  been  to  a  great  degree  de- 
prived of  its  oxygen,  or  rather  has  become  loaded  with  carbonic  acid;  and 
this  stagnation  will,  of  course,  be  communicated  to  all  the  rest  of  the  system. 
Yet,  if  it  have  not  continued  sufficiently  long,  to  cause  the  loss  of  vitality  in 
the  nervous  centres,  the  movement  may  be  renewed  by  the  admission  of  air 
into  the  lungs.  Now,  although  it  has  been  asserted  that  the  stagnation  is  due 
to  a  mechanical  impediment,  resulting  from  the  contracted  state  of  the  lungs  in 
such  cases,  this  has  been  clearly  proved  not  to  be  the  fact,  by  causing  animals 
to  breathe  a  gas  destitute  of  oxygen,  so  as  to  produce  Asphyxia  in  a  different 
manner;  the  same  stagnation  results  as  in  the  other  case. 

739.  If  the  phenomena  which  have  been  here  brought  together,  be  con- 
sidered as  establishing  the  existence,  in  all  classes  of  beings  possessing  a  cir- 
culating apparatus,  of  a  Capillary  power,  which  affords  a  necessary  condition 
for  the  movement  of  the  nutritious  fluid,  through  those  parts  in  which  it  comes 
.into  more  immediate  relation  with  the  solids, — the  question  still  remains 
open,  as  to  its  nature.  That  the  Capillaries  possess  a  contractile  power,  far 
higher  in  degree  than  that  of  the  large  Arteries,  and  more  easily  excited  than 
that  of  the  smaller,  appears  scarcely  to  admit  of  doubt;  though  to  what  it  is 
due,  may  be  reasonably  questioned.  It  has  been  recently  asserted  by 
Schwann,  that  they  possess  the  same  kind  of  fibrous  tissue  in  their  walls,  as 
do  the  large  vessels :  and  this  cannot  be  regarded  as  improbable.  It  is  not 
possible,  however,  that  their  contractility  could  have  any  influence  in  aiding 
the  continuous  motion  of  blood  through  them  ;  unless  it  were  exercised  in  a 
very  different  manner  from  that  of  which  observation  affords  us  evidence. 
For,  when  we  are  microscopically  examining  the  Capillary  circulation  of  any 
part,  it  is  at  once  seen,  that  the  vessels  present  no  obvious  movement ;  and 
that  the  stream,  now  rendered  continuous  by  the  elasticity  of  the  arteries, 
passes  through  them,  as  through  unelastic  tubes.  The  only  method,  in  which 
the  contractility  of  the  Capillaries  could  produce  a  regular  influence  on  the 
current  of  blood,  would  be  an  alternate  contraction  and  dilatation,  or  a  peri- 
staltic movement ;  and  of  neither  of  these  can  the  least  traces  be  discerned. 
Hence  we  should  altogether  dismiss  from  our  minds  the  idea  of  any  mechani- 
cal assistance,  afforded  by  the  action  of  the  Capillaries,  to  the  movement  of 
the  blood.  That^the  contractile  coat  of  the  Capillaries  has  for  its  office,  to 
regulate  the  calibre  of  the  vessels,  can  scarcely  be  doubted ;  but  any  general 
permanent  contraction  would  only  occasion  an  obstacle  to  the  circulation, — 
as  is  shown  by  the  effects  of  stimulating  injections,  which,  if  thrown  into  the 
vessels  before  their  vitality  has  been  lost,  will  not  pass  through  the  capillaries. 
It  would  appear,  therefore,  to  be  through  their  action  on  this  coat,  that  local 
stimuli  occasion  a  contraction  of  the  capillaries  ;  their  effect,  however,  is  dif- 
ferent from  what  might  have  been  anticipated ;  for,  instead  of  the  capillary 
circulation  being  retarded,  it  is  accelerated,  at  least  until  an  abnormal  condition 


564  OF  THE  CIRCULATION  OF  BLOOD. 

results  from  their  continued  operation.  Here,  again,  is  another  evidence,  that 
something  different  from  mechanical  power  must  be  the  agent,  that  operates 
in  all  the  foregoing  cases. 

740.  It  appears,  from  the  preceding  facts,  that  the  conditions,  under  which 
the  power  in  question  uniformly  operates,  may  be  thus  simply  and  definitely 
expressed: — Whilst  the  injection  of  blood  into  the  Capillary  vessels  of  every 
part  of  the  system,  is  due  to  the  action  of  the  Heart,  its  rate  of  passage 
through  those  vessels  is  greatly  modified  by  the  degree  of  activity  in  the  pro- 
cesses, to  which  it  should  normally  be  subservient  in  them  ; — the  current 
being  rendered  more  rapid  by  an  increase  in  their  activity,  and  being  stagnated 
by  their  depression  or  total  cessation.— Thus  it  seems  that  "  the  capillaries 
possess  a  distributive  power  over  the  blood,  regulating  the  local  circulation, 
independently  of  the  central  organ,  in  obedience  to  the  necessities   of  each 
part."     If  this  be  true,  it  is   evident  that  the  dilatation  or  contraction  of  the 
Capillaries  will  only  have  a  secondary  influence  on  the  movement  of  the  blood 
through  them.     The  former  condition  is  usually  an  indication  of  diminished 
vital  energy ;  and  when  it  is  observed,  it  is  almost  invariably  accompanied  by 
a  retardation  or  partial  stagnation  of  the  current ;  on  the  other  hand,  the  ap- 
plication of  a  moderate  stimulus,  which  excites  the  contractility,  accelerates 
for  a  time  the  motion  of  the  blood,  by  rendering  more  energetic  that  reaction 
between  the  fluids  and  the   surrounding  tissues,  which  is  the  condition  that 
really  has  the  most  influence  over  the  current. — That  alterations  in  the  chemi- 
cal state  of  the  blood  (involving,  of  course,  important  changes  in  its  vital  pro- 
perties) are  capable  of  exercising  a  most  important  effect  on  the  Capillary  cir- 
culation, is  shown,  not  merely  by  the  stagnation  of  the  Pulmonary  Circulation 
in  Asphyxia  (§  780),  but  by  the  curious  fact  ascertained  by  Dr.  J*.  Reid, — that 
the  blood,  when  imperfectly  arterialized,  is  retarded  in   the  systemic  capilla- 
ries, causing  an  increased  pressure  on  the  walls  of  the  arteries.'   He  found  that, 
when  the  ingress  of  air  through  the  trachea  of  a  Dog  was  prevented,  and  the 
Asphyxia  was  proceeding  to  the  stage  of  insensibility, —  the  attemps  at  inspi- 
ration being  few  and  laboured,  and  the  blood  in  an  exposed  artery  being  quite 
venous  in  its  character, — the  pressure  upon  the  Arterial  walls,  as  indicated  by 
the  haemadynamometer  applied  to  the  Femoral  artery,  was  much  greater  than 
usual.     Upon  applying  a  similar  test  to  a  Vein,  however,  it  was  found  that 
the  pressure  was  proportionably  diminished ;  whence  it  became  apparent,  that 
there  was  an  unusual  obstruction  to  the  passage  of  venous  blood  through  the 
systemic  capillaries.     After  this  period,  however,  the  mercury  in  the  haema- 
dynamometer applied  to  the  artery  began  to  fall  steadily,  and  at  last  rapidly, 
in  consequence  of  the  diminished  force  of  the  heart,  and  the  retardation  of  the 
blood  in  the  pulmonic  capillaries ;   but,  if  atmospheric  air  was   admitted,  the 
mercury  rose  very  speedily,  showing  that  the  renewal  of  the  proper  chemical 
state  of  the  blood,  restored  the  condition  necessary  for  its  circulation  through 
the  Capillaries. 

741.  The  principles  already  noticed  (§  713)  as  put  forth  by  Prof.  Draper, 
seem  fully  adequate  to  explain  these  phenomena. 

a.  The  arterial  blood, — containing  oxygen  with  which  it  is  ready  to  part,  and  being  pre- 
pared to  receive  in  exchange  the  carbonic  acid  which  the  tissues  set  free, — must  obviously 
have  a  greater  affinity  for  the  tissues,  than  venous  blood;  in  which  both  these  changes  have 
already  been  effected.    Consequently  upon  mere  physical  principles,  the  arterial  blood  which 
enters  the  systemic  Capillaries  on  one  side,  must  drive  before  it,  and  expel  on  the  other  side 
of  the  net-work,  the  blood  which  has  become  venous  whilst  traversing  it.     But  if  the  blood 
which  enters  the  Capillaries  have  no  such  affinity,  no  such  motor  power  can  be  developed. 

b.  On  the  other  hand,  in  the  Capillaries  of  the  lungs  the  opposite  affinities  prevail.     The 
venous  blood  and  the  air  in  the  pulmonary  cells  have  a  mutual  attraction,  which  is  satisfied 
by  the  exchange  of  oxygen  and  carbonic  acid  that  takes  place  through  the  walls  of  the  capil- 
laries; and  when  the  blood  has  become  arterialized,  it  no  longer  has  any  attraction  for  the 


MOTION  OF  THE  BLOOD  IN  THE  CAPILLARIES.  565 

air.  Upon  the  very  same  principle,  therefore,  the  venous  blood  will  drive  the  arterial  before 
it,  in  the  pulmonary  capillaries,  whilst  respiration  is  properly  going  on :  but  if  the  supply  of 
oxygen  be  interrupted,  so  that  the  blood  is  no  longer  aerated,  no  change  in  the  affinities  takes 
place  whilst  it  traverses  the  capillary  net-work;  the  blood  continuing  venous,  still  retains  its 
need  of  a  change,  and  its  attraction  for  the  walls  of  the  capillaries ;  and  its  egress  into  the 
pulmonary  veins  is  thus  resisted,  rather  than  aided,  by  the  force  generated  in  the  lungs. 

c.  The  change  in  the  condition  of  the  blood,  in  regard  to  the  relative  proportions  of  its 
oxygen  and  carbonic  acid,  is  the  only  one  to  which  the  Pulmonary  Circulation  is  subservient; 
but  in  the  Systemic  Circulation,  the  changes  are  of  a  much  more  complex  nature ; — every 
distinct  organ  attracting  to  itself  the  peculiar  substances  which  it  requires  as  the  materials 
of  its  own  nutrition ;  and  the  nature  of  the  affinities  thus  generated  being  consequently  differ- 
ent in  each  case.  But  the  same  law  holds  good  in  all  instances.  Thus  the  blood  conveyed 
to  the  liver  by  the  portal  vein,  contains  the  materials  at  the  expense  of  which  the  bile-secret- 
ing cells  are  developed;  consequently  the  tissue  of  the  liver,  which  is  principally  made  up 
of  these  cells,  possesses  a  certain  degree  of  affinity  or  attraction  for  blood  containing  these 
materials ;  and  this  is  diminished,  so  soon  as  they  have  been  drawn  from  it  into  the  cells 
around.  Consequently  the  blood  of  the  portal  vein  will  drive  before  it,  into  the  hepatic  vein, 
the  blood  which  has  traversed  the  capillaries  of  the  portal  system,  and  which  has  given  up, 
in  doing  so,  the  elements  of  bile  to  the  solid  tissues  of  the  liver. — The  same  principle  holds 
good  in  every  other  case. 

742.  It  can  be  scarcely  doubted,  that  it  is  by  some  influence  exercised  over 
the  molecular  actions,  to  which  the  Blood  is  subject  in  the  Capillaries,  that 
the  Nervous  system  can  operate  on  the  functions  of  Nutrition,  Secretion,  &c.» 
in  the  manner  already  alluded  to  (Chap,  vii.) ;  and  this  influence  may  be  not 
improperly  termed  vital,  if  by  so  designating  it  we  merely  imply  that  its 
nature  and  mode  of  operation  are  unknown,  but  that  it  is  closely  connected 
with  those  actions  which  are  altogether  peculiar  to  living  beings.  The  follow- 
ing experiment,  made  by  Dr.  Wilson  Philip,  exhibits  in  a  convincing  manner 
the  possibility  of  such  an  influence.  "  The  web  of  one  of  the  hind  legs  of  a 
frog  was  brought  before  the  microscope ;  and  while  Dr.  Hastings  observed  the 
circulation,  which  was  vigorous,  the  brain  was  crushed  by  the  blow  of  a  ham- 
mer. The  vessels  of  the  web  instantly  lost  their  power,  the  circulation  ceas- 
ing ;  an  effect  which  cannot  arise,  as  we  have  seen,  from  the  ceasing  of  the 
action  of  the  heart.  [Dr.  P.  here  refers  to  experiments,  by  which  it  was  ascer- 
tained, that  the  circulation  in  the  capillary  vessels  of  the  frog  will  continue  for 
several  minutes,  after  the  interruption  of  the  heart's  action.]  In  a  short  time 
the  blood  again  began  to  move,  but  with  less  force.  This  experiment  was 
repeated,  with  the  same  result.  If  the  brain  is  not  completely  crushed,  although 
the  animal  is  killed,  the  blow,  instead  of  destroying  the  circulation,  increases 
its  rapidity."*  We  are  not  hence  to  conclude,  however,  that  the  Nervous 
system  supplies  any  influence,  which  is  essential  to  the  continuance  of  the 
Circulation  ;  since  it  is  only  by  such  sudden  and  severe  injuries  to  the  nervous 
centres,  as  instantaneously  destroy  the  vitality  of  the  whole  system  (§  735), 
that  the  movement  of  the  blood  is  arrested.  The  experiments  of  Muller  and 
others  satisfactorily  prove,  that  mere  action  of  the  Nerves  does  not  produce 
any  direct  effect  upon  the  Capillary  circulation;  and  this  corresponds  with  the 
well-known  fact,  that  the  Nutritive  processes  may  continue  as  usual,  after  this 
action  has  been  suspended.  All  the  facts,  which  bear  upon  the  question  of 
the  connection  between  Nervous  agency  and  the  forces  maintaining  the 
Capillary  Circulation,  have  an  equal  relation  to  the  functions  of  Nutrition  and 
Secretion  in  general;  and  as  already  shown,  the  Nervous  System  also  influ- 
ences these,  by  the  control  it  exerts  over  the  diameter  of  the  blood-vessels 
(§  730). 

*  Experimental  Inquiry  into  the  Laws  of  the  Vital  Functions,  4th  edition,  p.  52. 
48 


566  OF  THE  CIRCULATION  OF  BLOOD. 


4. — Of  the  Venous  Circulation. 

743.  The  Venous  system  takes  its  origin  in  the  small  trunks  that  are 
formed  by  the  re-union  of  the  Capillaries;  and  it  returns  the  blood  from  these 
to  the  Heart.     The  structure  of  the  Veins  is  essentially  the  same  with  that  of 
the  Arteries ;  but  the  fibrous  tissue,  of  which  their  middle  coat  is  made  up, 
bears  more  resemblance  to  the  areolar  tissue  of  the  skin,  than  it  does  either 
to  muscular  fibre,  or  to  the  true  elastic  tissue.     The  Elasticity  of  the  Veins, 
however,  is  shown  by  the  jet  of  blood,  which  at  first  spouts  out  in  ordinary 
venesection;  when,  by  means  of  the  ligature,  a  distension  has  been  occasioned 
in  the  tubes  below  it.     A  slight  Contractility  on  the  application  of  stimuli, 
and  on  irritation  of  the  Sympathetic  nervous  fibres,  has  been  observed  ;  but 
this  is  not  so  decided  as  in  the  Arteries.     The  whole  capacity  of  the  Venous 
system  is  considerably  greater  than  that  of  the  Arterial ;  the  former  is  usually 
estimated  to  contain  from  2  or  3  times  as  much  blood  as  the  latter,  in  the 
ordinary  condition  of  the  circulation ;  and  when  we  consider  the  great  pro- 
portion, which  the  Veins  in  almost  every  part  of  the  body  bear  to  the  arteries, 
we  shall  scarcely  regard  even  the  larger  of  these  ratios  as  exaggerated.     Of 
course  the  rapidity  of  the  movement  of  the  blood  in  the  two  systems,  will 
bear  an  inverse  ratio  to  their  respective  capacities ;  thus  if,  in  a  given  length, 
the  Veins  contain  three  times  as  much  blood  as  the  Arteries,  the  fluid  will 
move   with  only  one-third  of  the  velocity.      Even  at  their  origins  in  the 
Capillary  plexus,  the  Veins  are  larger  than  the  Arteries  which  terminate  in 
the  same  plexus ;   so  that,  wherever  the  arterial  and  venous  net-works  form 
distinct  strata,  they  are  readily  distinguished  from  each  other.     The  Veins 
are  remarkable  for  the  number  of  valves  which  they  contain,  formed  of  dupli- 
catures  or  loose  folds  of  the  internal  tunic,  between  the  component  laminae  of 
which,  contractile  fibres  are  interposed ;  and  also  for  the  dilatations  behind 
these,  which,  when  distended,  give  them  a  varicose  appearance.     The  valves 
are  single  in  the  small  veins,  the  free  edge  of  the  flap  closing  against  the 
opposite  wall  of  the  vein ;  in  the  larger  trunks  they  are  double  ;  and  in  a 
few  instances  they  are  composed  of  three  flaps.     The  object  of  these  valves 
is  evidently  to  prevent  the  reflux  of  blood ;  and  we  shall  presently  see  that 
they  are  of  important  use  in  assisting  in  the  maintenance  of  the  venous  circu- 
lation.    They  are  most  numerous  in  those  Veins  which  run  among  parts 
affected  by  muscular  movement ;  and  they  are  not  found  in  the  veins  of  the 
lungs  of  the  abdominal  viscera  or  of  the  brain. 

744.  The  movement  of  the  blood   through  the  Veins   is,  without  doubt, 
chiefly  effected  by  the  vis  a  tergo  or  propulsive  force  ;  which  results  from 
the  action  of  the  Heart  and  Arteries,  and  from  the  additional  power  generated 
in  the  Capillary  vessels.     This  is  shown  by  the  immediate  arrestment  of  it, 
which  takes  place  when  these  forces  are  suspended.     There  are  some  con- 
current causes,  however,  which  are  supposed  by  some  to  have  much  influence 
upon  it,  and  of  which  the  consideration  must  not  be  neglected. 

a:  One  of  these  is  the  suction-power  attributed  to  the  Heart ;  acting  as  a  vis  a  fronte,  in 
drawing  the  blood  towards  it.  It  is  very  doubtful  how  far  the  Auricles  have  such  a  power 
of  active  dilatation,  as  that  which  would  be  required  for  this  purpose;  and  no  sufficient 
evidence  has  been  given,  that  the  current  of  blood  at  any  distance  from  the  Heart  is  affected 
by  it.  Indeed,  for  a  reason  to  be  presently  stated,  this  may  be  regarded  as  impossible. 

b.  Another  important  agency  has  been  found  by  some  Physiologists  in  the  Inspiratory 
movement;  this  is  supposed  to  draw  the  blood  of  the  Veins  into  the  chest,  in  order  to  sup- 
ply the  vacuum  which  is  created  there,  at  the  moment  of  the  descent  of  the  Diaphragm. 
That  the  movement  in  question  has  some  influence  on  the  flow  of  Venous  blood  into  the 
chest,  is  evident  from  the  occurrence  of  the  respiratory  pulse,  long  ago  described  by  Haller ; 
which  may  be  seen  in  the  veins  of  the  neck  and  shoulder  in  thin  persons,  and  in  those 
especially  who  are  suffering  from  pulmonary  diseases.  During  Inspiration,  the  Veins  are 


VENOUS  CIRCULATION.  567 

seen  to  be  partially  emptied ;  whilst  during  Expiration  they  become  turgid,  partly  in  con- 
sequence of  the  accumulation  from  behind,  and  of  the  check  in  front ;  and  partly  (it  may 
be)  in  some  cases,  through  an  absolute  reflux  from  the  veins  within  the  chest  (§  723,  c). 
The  fact  that,  in  the  immediate  neighbourhood  of  the  chest,  the  flow  of  blood  towards  the 
heart  is  aided  by  Inspiration  and  impeded  by  Expiration,  is  further  proved  by  Sir  D.  Barry  s 
experiment,  which  consisted  in  introducing  one  extremity  of  a  tube  into  the  Jugular  vein  of 
a  Horse,  and  the  other  into  water,  which  exhibited  an  alternate  elevation  and  depression 
with  inspiration  and  expiration ;  this  has  been  repeated  and  confirmed  by  several  Physiolo- 
gists. On  the  other  hand,  the  expiratory  movement,  while  it  directly  causes  accumulation 
in  the  Veins,  will  assist  the  Heart  in  propelling  the  blood  into  the  Arteries ;  and  by  the  com- 
bined action  of  these  two  causes  are  produced,  among  other  effects,  the  rising  and  sinking  of 
the  Brain,  synchronously  with  expiration  and  inspiration,  which  are  observed  when  a  por- 
tion of  the  cranium  is  removed.  Several  considerations,  however,  agree  in  pointing  to  the 
conclusion,  that  no  great  efficacy  can  be  rightly  attributed  to  the  Respiratory  movements,  as 
exerting  any  general  influence  over  the  Venous  circulation.  The  Pulmonary  circulation, 
being  entirely  within  the  chest,  cannot  be  affected  by  variations  in  atmospheric  pressure  ; 
and  it  may  be  further  remarked,  that  the  whole  mechanism  of  respiration  is  so  different  in 
Birds,  from  that  which  exists  in  Mammalia,  that  no  vacuum  can  ever  be  said  to  exist  in 
their  chests,  although  the  venous  circulation  is  performed  as  actively  as  usual.  The  Venous 
circulation  of  the  foetus,  also,  is  independent  of  any  such  agency.  Again,  it  has  been  shown 
experimentally  by  Dr.  Arnott  and  others,  that  no  suction-power  exerted  at  the  farther  end 
of  a  long  tube,  whose  walls  are  so  deficient  in  firmness  as  are  those  of  the  Veins,  can  oc- 
casion any  acceleration  in  a  current  of  fluid  transmitted  through  it;  for  the  effect  of  the 
suction  is  destroyed,  at  no  great  distance  from  the  point  at  which  it  is  applied,  by  the  flap- 
ping together  of  the  sides  of  the  vessel. 

c.  One  of  the  most  powerful  of  the  general  causes  which  influence  the  Venous  circula- 
tion, is  doubtless  the  frequently-recurring  action  of  the  Muscles  upon  their  trunks.  In  every 
instance  that  Muscular  movement  takes  place,  a  portion  of  the  Veins  of  the  part  will  undergo 
compression ;  and  as  the  blood  is  prevented,  by  the  valves  in  the  veins,  from  being  driven 
back  into  the  small  vessels,  it  is  necessarily  forced  on  towards  the  Heart.  As  each  set  of 
muscles  is  relaxed,  the  Veins  compressed  by  it  fill  out  again, — to  be  again  compressed  by 
the  renewal  of  the  force.  That  the  general  Muscular  movement  is  an  important  agent  in 
maintaining  the  Circulation,  at  a  point  above  that,  at  which  it  would  be  kept  by  the  action 
of  the  Heart  and  Capillaries  alone,  appears  from  several  considerations.  The  pulsations 
are  diminished  in  frequency  by  rest,  accelerated  by  exertion,  and  very  much  quickened  by 
violent  effort.  In  all  kinds  of  exercise,  and  in  almost  every  sort  of  effort,  there  is  that 
alternate  contraction  and  relaxation  of  particular  groups  of  Muscles,  which  has  been  just 
mentioned,  as  effecting  the  flow  of  blood  through  the  Veins;  and  there  can  be  little  doubt, 
that  the  increased  rapidity  of  the  return  of  blood';through  them,  is  of  itself  a  sufficient  cause 
for  the  accelerated  movements  of  the  Heart.  When  a  large  number  of  Muscles  are  put  in 
action  after  repose,  as  is  the  case  when  we  rise  up  from  a  recumbent  or  a  sitting  posture, 
the  blood  is  driven  to  the  Heart  with  a  very  strong  impetus ;  and  if  that  organ  should  be 
diseased,  it  may  arrive  there  in  a  quantity  larger  than  can  be  disposed  of;  so  that  sudden 
death  may  be  the  result.  Hence  the  necessity  for  the  avoidance  of  all  sudden  and  violent 
movements,  on  the  part  of  those  who  labour  under  either  a  functional  or  structural  disease  of 
the  centre  of  the  circulation. 

745.  The  Venous  circulation  is  much  more  liable  than  the  Arterial,  to  be 
influenced  by  the  force  of  Gravity ;  and  this  influence  is  particularly  notice- 
able, when  the  tonicity  of  the  vessels  is  deficient. 

a.  The  following  experiments  performed  by  Dr.  Williams,  to  elucidate  the  influence  of 
deficient  firmness  in  the  walls  of  the  vessels,  and  of  gravitation,  over  the  movement  of  fluids 
through  tubes,  throw  great  light  on  the  causes  of  Venous  Congestion. — A  tube  with  two 
equal  arms  having  been  fitted  to  a  syringe,  a  brass  tube  two  feet  long,  having  several  right 
angles  in  its  course,  was  adapted  to  one  of  them,  whilst  to  the  other  was  tied  a  portion  of  a 
rabbit's  intestine  four  feet  long,  and  of  calibre  double  that  of  the  brass  tube,  this  being 
arranged  in  curves  and  coils,  but  without  angles  and  crossings.  When  the  two  tubes  were 
raised  to  the  same  height,  the  small  metal  tube  discharged  from  two  to  five  times  the  quan- 
tity of  water  discharged  in  a  given  time  by  the  larger  but  membranous  tube;  the  difference 
being  greatest,  when  the  strokes  of  the  piston  were  most  forcible  and  sudden,  by  which  the 
intestine  was  much  dilated  at  its  syringe  end,  but  conveyed  very  little  more  water.  When 
the  discharging  ends  were  raised  a  few  inches  higher,  the  difference  increased  considerably, 
the  amount  of  fluid  discharged  by  the  gut  being  much  diminished ;  and  when  the  ends  were 
raised  to  the  height  of  eight  or  ten  inches,  the  gut  ceased  to  discharge,  each  stroke  only 
moving  the  column  of  water  in  it,  and  this  subsiding  again,  without  rising  high  enough  to 


568  OF  THE  CIRCULATION  OF  BLOOD. 

overflow.     When  the  force  of  the  stroke  increased,  the  part  of  the  intestine  nearest  the 
syringe  burst. 

b.  From  these  experiments  it  is  easy  to  understand,  how  any  deficiency  of  tone  in  the 
Venous  System  will  tend  to  prevent  the  "ascent  of  the  blood  from  the  depending  parts  of  the 
body,  and  will  consequently  occasion  an  increased  pressure  on  the  walls  of  the  vessels,  and 
an  augmentation  in  the  quantity  of  blood  they  contain.  All  these  conditions  are  peculiarly 
favourable  to  the  escape  of  the  watery  part  of  the  blood  from  the  small  vessels;  and  this 
may  either  infiltrate  into  the  areolar  tissue,  or  it  may  be  poured  into  some  neighbouring 
serous  cavity,  producing  dropsy.  Thus  it  happens,  that  such  effusions  may  often  be  traced, 
to  that  state  of  deficient  vigour  of  the  system,  which  peculiarly  manifests  itself  in  want  of 
tone  of  the  blood-vessels ;  and  that  it  is  relieved  by  remedies  which  restore  this.  In  many 
young  females  of  leuco-phlegmatic  temperament,  for  example,  there  is  a  tendency  to  swell- 
ing of  the  feet,  by  cedematous  effusion  into  the  areolar  tissue,  in  consequence  of  the  depend- 
ing position  of  the  limbs;  the  oedema  disappears  during  the  night, but  returns  during  the  day, 
and  is  at  its  maximum  in  the  evening.  And  the  congestion  which  frequently  manifests 
itself  in  the  posterior  parts  of  the  body,  towards  the  close  of  exhausting  diseases,  in  which 
the  patient  has  lain  much  upon  his  back,  is  attributable  to  a  similar  cause;  of  such  conges- 
tion, effusions  into  the  various  serous  cavities  are  frequent  results ;  and  such  effusions,  taking 
place  during  the  last  hours  of  life,  are  often  erroneously  regarded  as  the  cause  of  death.  To 
the  same  cause  we  are  to  attribute  the  varicose  state  of  the  veins  of  the  leg,  which  is  so 
common  amongst  persons  of  relaxed  fibre,  and  especially  in  those  whose  habits  require 
them  to  be  much  in  the  erect  posture  ;  and  this  distension  occasionally  proceeds  to  complete 
rupture,  the  causes  of  which  are  fully  elucidated  by  the  experiments  just  cited. 

5. — Peculiarities  of  the  Circulation  in  different  Parts. 

746.  In  several  portions  of  the  Human  body,  there  are  certain  varieties  in 
the  distribution  and  in  the  functional  actions  of  the   Blood- Vessels,  which 
should  not  be  omitted  in  a  general  account  of  the  Circulation.     Of  these,  we 
have  in  the  first  place  to  notice  the  apparatus  for  the  Pulmonary  circulation  ; 
the  chief  peculiarity  of  which  is,  that  venous  blood  is  sent  from  the  heart, 
through  a  tube  which  is  Arterial  in  its  structure,  whilst  arterial  blood  is  re- 
turned to  the  heart,  through  a  vessel  whose  entire  character  is  that  of  a  Vein. 
The  movement  of  the   blood  through  these  is  considerably  affected  by  the 
physical  state  of  the  Lungs  themselves  ;  being  retarded  by  any  causes,  which 
can  occasion  pressure  on  the  vessels  (sach  as  over-distension  of  the  cells  with 
air,  obstruction  of  their  cavity  by  solid  or  fluid  depositions,  or  by  foreign  sub- 
stances injected  into  them,  &c.);  and  proceeding  with  the  greatest  energy  and 
regularity,  when  the  respiratory  movements  are  freely  performed. — The  Por- 
tal circulation,  again,  is  peculiar,  in  being  a  kind  of  offset  from  the  general  or 
systemic  circulation ;  and  also  in  being  destitute  of  valves ;  and  it  may  be 
surmised  with  much  probability,  that  the  purpose  of  their  absence  is,  to  allow 
of  an  unusually  free  passage  of  blood  from  one  part  of  that  system  to  another, 
during  the  very  varying  conditions  to  which  it  is  subjected  (§  685). 

747.  Another  very  important  modification  of  the  Circulating  system,  is  that 
which  presents  itself  within  the  Cranium.     From   the  circumstance  of  the 
cranium  being  a  closed  cavity,  which  must  be  always  filled  with  the  same 
total  amount  of  contents,  the  flow  of  blood  through  its  vessels  is  attended  with 
some  peculiarities.     The  pressure  of  the  atmosphere  is  here  exerted,  rather 
to  keep  the  blood  in  the  head,  than  to  force  it  out ;  and  it  might  accordingly 
be  inferred  that,  whilst  the  quantity  of  cerebral  matter  remains  the  same,  the 
amount  of  blood  in  the  cranial  vessels  must  also  be  invariable.     This  infer- 
ence appeared  to  derive  support  from  the  experiments  of  Dr.  Kellie.*     On 
bleeding  animals  to  death,  he  found  that,  whilst  the  remainder  of  the  body  was 
completely  exsanguine,  the  usual  quantity  of  blood  remained  in  the  arteries 
and  veins  of  the  cranium  ;  but  that,  if  an  opening  was  made  in  the  skull,  these 
vessels  were  then  as  completely  emptied  as  the  rest.     It  is  not  to  be  hence 

*  Edinburgh  Medico-Chirurgical  Transactions,  vol.  i. 


PECULIARITIES  OF  CIRCULATION.  569 

i 

inferred,  however,  that  the  absolute  quantity  of  blood  within  the  cranium  is 
not  subject  to  variation;  and  that  in  the  states  of  inflammation,  congestion,  or 
other  morbid  affections,  there  is  only  a  disturbance  of  the  usual  balance  of 
the  arterial  and  venous  circulation.  The  fact  in  all  probability  is  rather,  that 
the  softness  of  the  Cerebral  tissue,  and  its  varying  functional  activity,  render 
it  peculiarly  liable  to  undergo  alterations  in  bulk ;  and  that  the  amount  of  the 
cerebro-spinal  fluid  varies  considerably  at  different  times  (§  476) ;  so  that  the 
quantity  of  blood  may  thus,  even  in  the  healthy  condition,  be  continually 
changing.  Moreover,  in  disordered  states  of  the  circulation,  the  quantity  of 
blood  in  the  vessels  of  the  cranium  may  be  for  a  time  diminished  by  a  sudden . 
extravasation,  either  of  blood  or  serum,  into  the  cerebral  substance;  and  the 
amount  of  interior  pressure  upon  the  walls  of  the  vessels  may  also  be  con- 
siderably altered,  even  when  there  is  no  difference  in  the  quantity  of  fluid 
contained  in  them.* 

748.  The  Erectile  tissues  constitute  another  curious  modification  of  the 
ordinary  vascular  apparatus.  The  chief  of  these  are  the  Corpora  Cavernosa 
in  the  penis  of  the  male,  and  in  the  clitoris  of  the  female ;  the  collection  of 
similar  tissues  round  the  vagina,  and  in  the  nymphae,  of  the  female ;  and  the 
nipple  in  both  sexes.  In  all  these  situations,  erection  may  be  produced  by 
local  irritation ;  or  it  may  take  place  as  a  result  of  certain  emotional  conditions 
of  the  mind ;  the  influence  of  which  is  probably  transmitted  through  the 
Sympathetic  nerve,  as  it  may  be  experienced  even  in  cases  of  paraplegia. 
The  erectile  tissue  appears  essentially  to  consist  of  a  plexus  of  varicose  Veins, 
inclosed  in  a  fibrous  envelope.  According  to  Gerber,t  this  plexus  is  traversed 
by  numerous  contractile  fibres,  which  are  analogous  to  those  that  form  the 
dartos ;  and  to  the  contraction  of  these  is  probably  to  be  attributed  that  ob- 
struction to  the  return  of  blood  by  the  Veins,  which  is  the  occasion  of  the 
turgescence.  The  proximate  cause  of  the  erection  of  the  Penis,  has  been 
stated  by  some  to  be  the  action  of  the  Ischio-Cavernosi  muscles  ;  and  by  others 
it  has  been  attributed  to  the  compression  of  the  Vena  dorsalis  penis  against 
the  Symphysis  pubis.  But  it  is  obvious  that  nothing  analogous  to  this  can 
apply  to  the  other  erectile  organs,  especially  to  the  Nipple.  In  the  Penis, 
according  to  Muller,  there  are  two  sets  of  arteries ;  of  which  one,  destined  for 
the  nutrition  of  the  tissues,  communicates  with  the  veins  in  the  usual  way, 
through  a  capillary  net-work  ;  whilst  the  others  pass  off  as  large  branches,  and 
penetrate  the  cavernous  substance  in  a  helicine  manner,  communicating  ab- 
ruptly with  the  venous  cells.  It  would  seem  not  improbable,  that  these  last 
are  not  ordinarily  pervious  to  blood ;  but  that  the  same  change  in  the  contrac- 
tile fibres,  which  impedes  the  return  of  the  blood  by  the  veins,  may  also 
permit  it  to  enter  more  freely  from  the  helicine  arteries.  This  double  com- 
munication, however,  is  denied  by  Valentin,  who  gives  a  different  explanation 
of  the  appearances  described  by  Muller. — The  arteries  are  protected  in  such 
a  manner,  that,  even  when  the  veins  are  most  compressed,  and  the  erection 
most  complete,  they  are  still  quite  pervious. 

*  The  results  of  the  more  recent  experiments  of  Dr.  G.  Burrows  (Med.  Gaz.,  April  and 
May,  1843)  fully  confirm  the  views  stated  above, 
f  General  Anatomy,  p.  298. 

48* 


570  OF  RESPIRATION. 


CHAPTER    XIII. 


OF    RESPIRATION. 

1. — Nature  of  the  Function:  and  Provisions  for  its  Performance. 

749.  IT  is  obvious  that  the  Nutritive  fluid,  in  its  circulation  through  the 
capillaries  of  the  system,  must  undergo  great  alterations,  both  in  its  physical 
constitution,  and  its  vital  properties.  It  gives  up  to  the  tissues  with  which  it 
is  brought  into  contact,  some  of  its  most  important  elements  ;  and,  at  the  same 
time,  it  is  made  the  vehicle  of  the  removal,  from  these  tissues,  of  ingredients 
which  are  no  longer  in  the  state  of  combination,  that  fits  them  for  their  offices 
in  the  Animal  Economy.  To  separate  these  ingredients  from  the  general  cur- 
rent of  the  circulation,  and  to  carry  them  out  of  the  system,  is  the  great  object 
of  the  Excretory  organs  ;  and  it  is  very  evident  that  the  importance  of  the 
respective  functions  of  these  will  vary  with  the  amount  of  the  ingredient 
which  they  have  to  separate,  and  with  the  deleterious  influence  which  its  re- 
tention would  exert  on  the  welfare  of  the  system  at  large.  Of  all  these  injuri- 
ous ingredients,  Carbonic  Acid  is  without  doubt  the  one  most  abundantly 
introduced  into  the  nutritive  fluid ;  and  it  is  also  most  deleterious  in  its  effects 
on  the  system,  if  allowed  to  accumulate. — We  find,  accordingly,  that  the  pro- 
vision for  the  removal  of  Carbonic  Acid  from  the  Blood,  is  one  of  peculiar 
extent  and  importance,  especially  in  the  higher  forms  of  Animals  ;  and  further, 
that  instead  of  being  effected  by  an  operation  peculiarly  vital  (like  other  acts 
of  Excretion),  its  performance  is  secured  by  being  made  to  depend  upon  simple 
physical  laws,  and  is  not  nearly  so  susceptible  of  derangement  from  disorder 
of  other  processes,  as  it  would  be  if  its  conditions  were  less  simple.  All  that 
is  requisite  for  it,  as  we  shall  presently  see,  is  the  exposure  of  the  Blood  to 
the  influence  of  the  Atmospheric  air,  or  of  Air  dissolved  in  water,  through  the 
medium  of  a  membrane  that  shall  permit  the  diffusion  of  gases;  and  an  inter- 
change then  takes  place  between  the  gaseous  matters  on  the  two  sides, — Car- 
bonic acid  being  exhaled  from  the  Blood,  and  being  replaced  by  Oxygen. 
Thus  the  extrication  of  Carbonic  acid  is  effected  in  a  manner,  that  renders  it 
subservient  to  the  introduction  of  the  element  which  is  required  for  all  the 
most  active  manifestations  of  vital  power ;  and  it  is  in  these  two  processes 
conjointly,  not  in  either  alone,  that  the  function  of  Respiration  essentially  con- 
sists.— We  shall  now  inquire  into  the  sources  from  which  Carbonic  acid  is 
produced  in  the  living  body;  and  the  causes  of  the  demand  for  Oxygen. 

750.  All  organized  bodies,  as  already  explained,  are  liable  to  continual 
decay,  even  whilst  they  are  most  actively  engaged  in  performing  the  actions 
of  Life ;  and  one  of  the  chief  products  of  that  decay  is  Carbonic  Acid.  A 
large  quantity  of  this  gas  is  set  free,  during  the  decomposition  of  almost  every 
kind  of  organized  matter;  the  Carbon  of  the  substance  being  united  with  the 
oxygen  supplied  by  the  air.  Hence  we  find,  that  the  formation  and  liberation 
of  carbonic  Acid  go  on  with  great  rapidity  after  death,  both  in  the  Plant  and 
in  the  Animal ;  and  that  they  take  place,  also,  to  a  very  great  extent,  in  the 
period  that  often  precedes  the  death  of  the  body,  during  which  a  general  de- 
composition of  the  tissues  is  occurring.  Thus  in  Plants,  as  soon  as  they 
become  unhealthy,  the  extrication  of  carbon  in  the  form  of  carbonic  acid  takes 


SOURCES  OF  CARBONIC  ACID.  571 

I 

place  in  greater  amount  than  its  fixation  from  the  carbonic  acid  of  the  atmo- 
sphere ;  and  the  same  change  normally  occurs  during  the  period  that  immedi- 
ately precedes  the  annual  fall  of  the  leaves,  their  tissue  being  no  longer  able 
to  perform  its  proper  functions,  and  giving  rise,  by  its  incipient  decay,  to  a 
large  increase  in  the  quantity  of  carbonic  acid  set  free.  The  same  thing 
happens  in  the  Animal  body,  during  the  progress  of  many  diseases  which  are 
attended  with  an  unusual  tendency  to  decomposition  in  the  solids  and  fluids, 
— such  as  eruptive  fevers  ; — the  quantity  of  carbonic  acid  set  free  in  Respira- 
tion is  greatly  increased,  although  the  body  remains  completely  at  rest ;  and 
notwithstanding  this,  the  blood  frequently  exhibits  a  very  dark  hue,  indicating 
that  it  has  not  been  freed  from  the  unusual  amount  of  that  substance  which 
it  has  received  from  the  tissues. — Hence  the  first  object  of  the  Respiratory 
process,  which  is  common  to  all  forms  of  organized  being,  is  to  extricate  from 
the  body  the  carbonic  acid,  which  is  one  of  the  products  of  the  continual  de- 
composition of  its  tissues.  The  softness  of  many  of  the  tissues  of  Animals, 
and  the  large  quantity  of  fluid  contained  in  their  bodies,  render  them  more 
prone  than  Plants  to  this  kind  of  decomposition;  and  in  warm-blooded  animals, 
the  high  temperature  at  which  the  fabric  is  usually  maintained,  adds  con- 
siderably to  the  degree  of  this  tendency,  so  that  the  waste  of  their  tissues, 
from  this  cause  alone,  is  as  much  greater  than  that  of  cold-blooded  animals, 
as  the  latter  is  than  that  of  Plants.  But  when  the  temperature  of  the  Reptile 
is  raised  by  external  heat  to  the  level  of  that  of  the  Mammal,  its  need  for 
respiration  increases,  owing  to  the  augmented  waste  of  its  tissues.  When,  on 
the  other  hand,  the  warm-blooded  Mammal  is  reduced,  in  the  state  of  hyber- 
nation,  to  the  level  of  the  cold-blooded  Reptile,  the  waste  of  its  tissues  dimin- 
ishes to  such  an  extent,  as  to  require  but  a  very  small  exertion  of  the  respira- 
tory process  to  get  rid  of  the  carbonic  acid,  which  is  one  of  its  chief  products. 
And  in  those  animals  which  are  capable  of  retaining  their  vitality,  when  they 
are  frozen,  or  when  their  tissues  are  completely  dried  up,  the  decomposition 
is  for  the  time  entirely  suspended,  and  consequently  there  is  no  carbonic  acid 
to  be  set  free. 

751.  But  another  source  of  Carbonic  acid  to  be  set  free  by  the  Respiratory 
process,  and  one  which  is  peculiar  to  animals,  consists  in  the  rapid  changes 
which  take  place  in  the  Muscular  and  Nervous  tissues,  during  the  period  of 
their  activity.  It  has  been  already  shown  (§  586),  that  there  is  strong  reason 
to  believe  the  waste  or  decomposition  of  the  muscular  tissue  to  be  in  exact 
proportion  to  the  degree  in  which  it  is  exerted ;  every  development  of  muscu- 
lar force  being  accompanied  by  a  change  in  the  condition  of  a  certain  amount 
of  tissue.  In  order  that  this  change  may  take  place,  the  presence  of  Oxygen 
is  essential;  and  one  of  the  products  of  the  union  of  oxygen  with  the  elements 
of  muscular  fibre  is  carbonic  acid.  The  same  may  probably  be  said  of  the 
Nervous  tissue  (§  292).  Hence  it  may  be  stated  as  a  general  principle,  that 
the  peculiar  waste  of  the  Muscular  and  Nervous  substances,  which  is  a  con- 
dition of  their  functional  activity,  and  which  is  altogether  distinct  from  the 
general  slow  decay  that  is  common  to  these  tissues  with  others,  is  another 
source  of  the  carbonic  acid  which  is  set  free  from  the  animal  body ;  and  that 
the  amount  thus  generated  will  consequently  depend  upon  the  degree  in  which 
these  tissues  are  exercised.  In  animals  which  are  chiefly  made  up  of  the 
organs  of  vegetative  life,  in  whose  bodies  the  nervous  and  muscular  tissues 
form  but  a  very  small  part,  and  in  whose  tranquil  plant-like  existence  there  is 
but  very  little  demand  upon  the  exercise  of  these  structures,  the  quantity  of 
carbonic  acid  thus  liberated  will  be  extremely  small.  On  the  other  hand,  in 
animals,  whose  bodies  are  chiefly  composed  of  muscle,  and  whose  life  is  an 
almost  ceaseless  round  of  exertion,  the  quantity  of  carbonic  acid  thus  liberated 
is  very  considerable. 


572  OF  RESPIRATION. 

752.  Besides  these  sources  of  Carbonic  acid,  which  are  common  to  all 
Animals,  there  is  another,  which  appears  to  be  peculiar  to  the  two  highest 
classes,  Birds  and  Mammals.     These  are  capable  of  maintaining  a  constantly 
elevated  temperature,  so  long  as  they  are  supplied  with  a  proper  amount  of 
appropriate  food;  and  their  power  of  doing  so  appears  to  depend  upon  the 
direct  combination  of  certain  elements  of  the  food,  with  the  oxygen  of  the  air, 
by  a  process  analogous  to  combustion  ;  these  elements  having  been  introduced 
into  the  blood  for  that  purpose,  but  not  having  formed  a  part  of  any  of  the 
solid  tissues  of  the  body,  unless  they  have  been  deposited  in  the  form  of  fat. 
The  nature  of  these  substances  has  been  already  noticed  (§  641).     It  is  quite 
clear  that  they  cannot  be  applied  in  their  original  form,  to  the  nutrition  of  the 
tissues  that  originate  in  proteine  compounds;  and  it  is  tolerably  certain  that, 
in  the  ordinary  condition  of  the  body,  they  undergo  no  such  conversion,  as 
would  adapt  them  to  that  purpose.     The  Liver  seems  to  afford  a  channel,  by 
which  some  of  the  fatty  matters  are  drawn  off  from  the  blood ;  but  even  these 
seem,  in  part  at  least,  to  be  reabsorbed  (§  671),  and  to  be  thrown  off  by  the 
respiratory  process. 

753.  The  quantity  of  carbonic  acid,  that  is  generated   directly  from   the 
elements  of  the  food,  seems  to  vary  considerably  in  different  animals,  and  in 
different  states  of  the  same  individual.    In  the  Carnivorous  tribes,  which  spend 
the  greater  part  of  their  time  in  a  state  of  activity,  it  is  probable  that  the  quan- 
tity which  is  generated  by  the  waste  or  metamorphosis  of  the  tissues  is  suffi- 
cient for  the  maintenance  of  the  required  temperature, — and  that  little  or  none 
of  the  carbonic  acid  set  free  in  respiration  is  derived  from  the  direct  combus- 
tion of  the  materials  of  the  food.    But  in  Herbivorous  animals  of  comparatively 
inert  habits,  the  amount  of  metamorphosis  of  the  tissues  is  far  from  being  suf- 
ficient; and  a  large  part  of  the  food,  consisting  as  it  does  of  substances  that 
cannot  be  applied  to  the  nutrition  of  the  tissues,  is  made  to  enter  into  direct 
combination  with  the  .oxygen  of  the  air,  and  thus  to  compensate  for  the  de- 
ficiency.   In  Man  and  other  animals,  which  can  sustain  considerable  variations 
of  climate,  and  can  adapt  themselves  to  a  great  diversity  of  habits,  the  quantity 
of  carbonic  acid  formed  by  the  direct  combination  of  the  elements  of  the  food 
with  the  oxygen  of  the  air,  will  differ  extremely  under  different  circumstances. 
It  will  serve  as  the  complement  of  that  which  is  formed  in  other  ways ;  so 
that  it  will  diminish  with  the  increase,  and  will  increase  with  the  diminution 
of  muscular  activity.     On  the  other  hand  it  will  vary,  in  accordance  with  the 
external  temperature;  increasing  with  its  diminution,  as  more  heat  must  then 
be  generated ;  and  diminishing  with  its  increase. — In  all  cases,  if  a  sufficient 
supply  of  food  be  not  furnished,  the  store  of  fat  is  drawn  upon :  and  if  this  be 
exhausted,  the  animal  dies  of  cold  (§  896). 

754.  To  recapitulate,  then,  the  sources  of  Carbonic  Acid  in  the  animal  body 
are  threefold. — I.  The  continual  decay  of  the  tissues;  which  is  common  to 
all  organized  bodies ;  which  is  diminished  by  cold  and  dryness,  and  increased 
by  warmth  and  moisture ;  which  takes  place  with  increased  rapidity  at  the 
approach  of  death,  whether  this  affect  the  body  at  large,  or  only  an  individual 
part;  and  which  goes  on  unchecked  when  the  actions  of  nutrition  have  ceased 
altogether. — n.  The  Metamorphosis,  which  is  peculiar  to  the  Nervous  and 
Muscular  tissues ;  which  is  the  very  condition  of  their  activity,  and  which 
therefore  bears  a  direct  relation  to  the  degree  in  which  they  are  exerted. — in. 
The  direct  conversion  of  the  carbon  of  the  food  into  carbonic  acid;  which  is 
peculiar  to  warm-blooded  animals ;  and  which  seems  to  vary  in  quantity,  in 
accordance  with  the  amount  of  heat  to  be  generated. — We  shall  now  examine 
into  the  manner  in  which  this  compound  is  set  free,  in  the  principal  groups  of 
the  Animal  kingdom. 

755.  Notwithstanding  their  diversity  in  external  form,  {he  organs  of  Re- 


GENERAL  STRUCTURE  OF  THE  RESPIRATORY  ORGANS.  573 

spiration  are  always  formed  upon  the  same  general  plan ;  being  essentially 
composed  of  a  membranous  prolongation  of  the  external  surface,  adapted,  by 
its  vascularity  and  permeability,  to  bring  the  blood  into  close  relation  with  the 
surrounding  medium.  But  as  this  medium  may  be  either  air  or  water,  we 
find  two  principal  forms  of  the  apparatus;  one  of  them  adapted  for  each  kind 
of  respiration.  In  aquatic  animals,  the  membrane  is  usually  prolonged  ex- 
ternally into  tufts  or  fringes,  which  are  so  arranged  as  to  expose  the  greatest 
amount  of  surface  to  the  water ;  each  filament  of  which  these  are  composed, 
includes  an  afferent  and  efferent  capillary  vessel ;  and  it  is  whilst  the  fluid  is 
passing  through  them,  that  its  aeration  is  accomplished.  The  collection  of 
tufts  or  fringes  constitutes  what  are  known  as  gills; 
and  though  their  arrangement  varies  considerably,  their  Fig.  214. 

essential  character  is  but  little  different,  throughout  the 
classes  of  animals  that  possess  them.  On  the  other 
hand,  in  air-breathing  Animals,  the  aerating  surface 
is  reflected  inwardly,  forming  passages  or  chambers 
into  which  the  air  is  received,  and  on  the  walls  of 
which  the  blood  is  distributed  in  a  minute  capillary 
net-work.  Such  a  conformation  is  found  even  among 
some  of  the  lower  Articulata,  which  have  a  series  of 
air-sacs  disposed  along  each  side  of  the  body,  one  for 
every  segment.  In  Insects  we  find,  instead  of  the 
sacs,  a  system  of  prolonged  tubes,  ramifying  through 
the  body,  and  carrying  air  into  its  minutest  por- 
tions. Even  in  Some  Mollusca,  such  as  the  Snail  One  of  the  arborescent  pro- 
,  ,  •  i  /-M  f  i  •  •  cesses,  forming  the  gills  of 

and  other  terrestrial  Gasteropods,  we  rind  a  provision     Doris  j0hnstorii,  separated 
for  aerial  respiration ;  a  large  cavity  being  formed  in     and  enlarged. 
the  back,  communicating  with  the  air,  and  having  a 

beautifully-reticulated  plexus  of  blood-vessels  on  its  walls.  In  none  of 
the  Invertebrata,  however,  does  the  respiratory  apparatus  communicate  with 
the  mouth;  which  is  an  organ  solely  appropriated,  in  them,  to  the  ingestion 
of  food.  In  the  Mollusca,  indeed,  the  channel  through  which  the  water, 
that  has  passed  over  the  aerating  surface,  leaves  the  chamber  (formed  by 
a  fold  of  the  mantle  or  general  envelope)  which  contains  the  gills,  is  the 
same  as  that  through  which  the  excrementitious  matter  is  discharged  from 
the  intestine ;  and  the  gills  themselves  are  very  commonly  situated  in  the 
neighbourhood  of  the  anal  orifice.  This  fact  is  interesting  in  regard  to  the 
character  of  the  temporary  respiratory  apparatus  of  the  Human  embryo.  In 
Fishes  and  the  Iarva3  of  Batrachia,  which  are  the  highest  animals  that  breathe 
by  gills,  these  organs  are  so  disposed  in  connecting  with  the  cavity  of  the 
mouth,  that  fresh  currents  of  water  are  continually  being  forced  over  them  by 
its  muscles ;  and  thus  the  energy  of  their  action  is  greatly  increased.  More- 
over the  whole  blood,  which  is  propelled  from  the  heart,  proceeds  first  to  the 
respiratory  organs ;  instead  of  passing  through  them  on  its  return  from  the 
systemic  circulation,  as  in  most  of  the  aquatic  Invertebrata.  Still,  as  the 
quantity  of  oxygen  which  the  blood  can  obtain  in  this  manner  is  very  small, 
being  limited  to  that  contained  in  the  atmospheric  air  dissolved  in  the  water, 
the  amount  of  aeration  must  be  considered  as  low. 

756.  In  the  lowest  Vertebrata  that  possess  anything  like  a  pulmonary  cavity, 
this  has  a  structure  as  simple  as  that  of  the  air-sac  of  the  Snail.  This  is  the 
case  in  many  Fishes,  where  it  is  known  as  the  air-bladder ;  it  is  frequently 
single  in  this  class,  and  communicates  with  the  intestinal  canal  near  the  sto- 
mach, or  is  altogether  destitute  of  outlet.  In  others,  however,  it  is  double, 
and  its  duct  opens  into  the  oasophagus  near  the  mouth ;  so  that  its  analogy  to 
the  lungs  of  higher  animals  is  very  evident.  The  Batrachia  begin  life  as 


574 


OF  RESPIRATION. 


Fishes,  breathing  by  gills  during  their  tadpole  state ;  but  at  the  time  that  the 
legs  are  developed  and  the  tail  has  decreased,  the  pulmonary  organs  also  are 
evolved,  and  the  course  of  the  blood  is  altered,  so  that  it  is  no  longer  trans- 
mitted through  the  gills,  which  speedily  shrivel  and  disappear  (§  31).  There 
are  some  species,  however,  whose  metamorphosis  is  checked,  so  that  in  their 
permanent  condition  both  lungs  and  gills  are  present ;  but  the  former  are  then 
present  in  a  very  rudimentary  form,  not  being  more  developed  than  the  air- 
sacs  of  many  Fishes.  The  lungs  of  Reptiles  are,  for  the  most  part,  simple 
sacs ;  into  which  the  bronchial  tubes  open  freely ;  and  on  the  walls  of  which, 
the  pulmonary  vessels  are  distributed.  The  extent  of  surface  is  considerably 
increased,  however,  by  the  formation  of  a  number  of  little  pits  or  sacculi  on 
the  inner  wall  of  the  cavity,  especially  at  its  upper  part;  and  between  these, 
we  observe  a  sort  of  cartilaginous  frame-work,  which  is  continuous  with  the 
cartilage  of  the  bronchus  on  either  side.  The  Turtles  and  their  allies  are  the 
only  Reptiles,  in  which  the  cavity  of  the  lung  is  itself  divided  by  membranous 
partitions ;  and  thus  it  happens  that,  excepting  in  these,  the  net- work  of  pul- 
monary capillaries,  in  the  class  of  Reptiles,  is  exposed  only  on  one  side  to 
the  influence  of  the  air.  The  general  distribution  of  these  vessels  is  shown 
in  the  accompanying  figures.  It  will  be  seen  that  the  trunk  of  the  pulmonary 
artery  runs  along  one  side  of  the  sac,  and  that  of  the  pulmonary  vein  along 
the  other  (Fig.  215) ;  and  that  numerous  branches  arise  from  the  former, 
which  subdivide  into  capillaries  that  ramify  over  the  whole  surface,  and  then 
reunite  into  small  veins  which  terminate  in  the  latter.  The  islets  of  paren- 
chyma left  between  the  capillary  vessels,  are  seen  to  be  much  smaller  than 
those  which  are  usually  to  be  observed  in  the  systemic  circulation  (Figs. 
216,  217);  so  that  the  membrane  is  more  copiously  traversed  by  vessels,  than 


Fig.  215. 


[Fig.  216. 


Lung  of  Triton  cristatus,  magnified 
about  3  diameters ;  a,  pulmonary  artery; 
b,  pulmonary  vein. 


Portion  of  the  lung  of  the  same  animal, 
more  highly  magnified ;  the  vessels,  finely- 
injected  with  size  and  vermilion,  form  a 
net-work  so  minute,  that  the  parenchyma  is 
only  seen  in  small  islets  in  its  interstices. 


GENERAL  STRUCTURE  OF  THE  RESPIRATORY  ORGANS.  575 

any  other  that  is  known.  The  walls  of  the  capillaries,  moreover,  are  much 
less  distinct  than  those  of  the  systemic  circulation.  These  two  conditions 
are  obviously  favourable  to  the  exposure  of  the  largest  possible  quantity  of 
blood  to  the  influence  of  the  air ;  but  as  the  surface  is  not  an  extensive  one, 
the  amount  which  can  be  thus  exposed  at  any  one  time  is  very  limited ;  and 
the  pulmonary  artery  is  in  fact  one  of  the  smaller  branches  of  the  aorta,  which 
conveys  a  mixed  fluid  to  the  system  at  large. 

Fig.  217. 


Portion  of  the  lung  of  a  living  Triton,  as  seen  under  the  microscope  with  the  power  of  150  diam. ;  a, 
b,  pulmonary  vein,  receiving  blood  from  the  large  trunk  c,  and  a  smaller  vessel  d, 

757.  In  the  warm-blooded  Vertebrata,  which  have  a  complete  double  cir- 
culation,— namely,  Birds  and  Mammalia, — a  much  larger  extent  of  surface  is 
provided  for  the  aeration  of  the  blood ;  the  whole  current  of  which  is  trans- 
mitted to  the  lungs,  before  circulating  again  through  the  system.  This  in- 
crease is  provided  in  Birds,  partly  by  the  greater  extension  of  surface  in  the 
lungs  themselves, — these  cavities  being  subdivided  by  partitions  into  numerous 
smaller  chambers,  each  having  pitted  walls,  and  resembling  the  entire  lung  of 
a  Reptile ; — and  partly  by  the  addition  of  a  number  of  large  air-sacs,  which 
are  disposed  in  various  parts  of  the  body,  and  even  in  the  interior  of  the  long 
bones.  Hence  it  happens,  that  the  amount  of  Respiration  is  greater  in  this 
class  than  in  any  other ;  although  the  form  of  the  apparatus  is  not  nearly  so 
concentrated  as  in  the  Mammalia  ;  nor  is  the  mechanism  of  the  chest  so  well 
adapted  to  a  constant  exchange  of  the  air  contained  in  its  cavities  (§  37).  In 
Mammalia  the  lungs  are  proportionally  smaller ;  and  the  whole  respiratory 


576 


OF  RESPIRATION. 


apparatus  is  restricted  to  the  thorax :  but  the  minute  subdivision  of  their  cavity, 
and  the  mechanism  by  which  a  continual  interchange  of  air  is  provided  for, 
render  them  very  efficient  for  their  designed  purpose. — The  following,  accord- 
ing to  the  latest  researches,  especially  those  of  Mr.  Rainey,*  appears  to  be 
the  nature  of  the  ultimate  structure  of  the  lungs  in  Man  and  the  Mammalia 
in  general.  The  bronchial  tubes  divide  and  subdivide,  like  the  branches  of  a 
tree,  still  retaining  their  ordinary  characters,  until  they  are  no  more  than  from 
l-50th  to  l-30th  of  an  inch  in  diameter ;  and  in  these  the  longitudinal  and 
annular  fibres,  together  with  the  ciliated  epithelium,  come  to  an  abrupt  ter- 
mination. Beyond  this  boundary,  the  tubular  form  of  the  air-passages  con- 
tinued from  the  bronchi  is  retained  for  some  distance  ;  but  it  is  gradually 
changed  by  the  irregular  branching  of  the  passages,  and  by  the  increase  of 
the  number  of  apertures  in  their  walls,  which  lead  to  the  air-cells.  Thus,  at 
last,  each  minute  division  of  the  air-passages  becomes  quite  irregular  in  form  ; 
air-cells  opening  into  every  part  of  itj  and  almost  constituting  its  walls ;  until 
it  terminates,  almost  without  dilatation,  in  an  air-cell.  This  terminal  portion 
of  the  air-passage,  with  its  surrounding  cluster  of  air-cells,  may  be  regarded 
as  forming  a  sort  of  lobule,  and  as  representing  the  entire  lung  of  a  Frog  or 

[Fig.  218. 


The  Larynx,  Trachea  and  Bronchia?,  deprived  of  their  fibrous  covering,  and  with  the  outline  of  the 
Lungs ;  1, 1,  outline  of  the  upper  lobes  of  the  lungs ;  2,  outline  of  the  middle  lobe  of  the  right  lung ;  3,  3, 
outline  of  the  inferior  lobes  of  both  lungs  ;  4,  outline  of  the  ninth  dorsal  vertebra,  showing  its  relation  to 
the  lungs  and  the  vertebral  column  ;  5,  thyroid  cartilage  ;  6,  cricoid  cartilage  ;  7,  trachea;  8,  right  bron- 
chus ;  9,  left  bronchus  ;  10,  crico-thyroid  ligament;  11, 12,  rings  of  the  trachea;  13,  first  ring  of  the  tra- 
chea ;  14,  last  ring  of  the  trachea,  which  is  corset-shaped ;  15, 16,  a  complete  bronchial  cartilaginous 
ring ;  17,  one  which  is  bifurcated  ;  18,  double  bifurcated  bronchial  rings ;  19, 19,  smaller  bronchial  rings ; 
20,  depressions  for  the  course  of  the  large  blood-vessels.] 

*  Medico-Chirurgical  Transactions,  vol.  xxviii. 


STRUCTURE  AND  DEVELOPMENT  OF  HUMAN  LUNG.  577 

[Fig.  219. 


A  view  of  the  Bronchise  and  Blood-Vessels  of  the  Lungs  as  shown  by  dissection,  as  well  as  the  rela- 
tive position  of  the  Lungs  to  the  Heart ;  1,  end  of  the  left  auricle  of  the  heart ;  2.  the  right  auricle ;  3, 
the  left  ventricle  with  its  vessels ;  4,  the  right  ventricle  with  its  vessels;  5,  the  pulmonary  artery ;  6, 
arch  of  the  aorta ;  7,  superior  vena  cava ;  8,  arteria  innominata  ;  9,  left  primitive  carotid  artery ;  10,  left 
subclavian  artery ;  11,  the  trachea ;  12,  the  larynx  ;  13,  upper  lobe  of  the  right  lung ;  14,  upper  lobe  of  the 
left  lung;  15,  trunk  of  the  right  pulmonary  artery ;  16,  lower  lobes  of  the  lungs.  The  distribution  of  the 
bronchia  and  of  the  arteries  and  veins,  as  well  as  some  of  the  air-cells  of  the  lungs,  is  also  shown  in 
this  dissection.] 

other  Reptile ;  the  whole  lung  of  the  Mammal  being  made  up  of  a  multitude 
of  such  lobules,  which  are  almost  exact  repetitions  of  each  other.  There  is, 
however,  this  difference ; — that  the  air-cells  in  the  lung  of  the  Reptile  are  mere 
sacculated  depressions  in  the  walls  of  the  cavity,  opening  very  freely  into  it ; 
— whilst  the  air-cells  of  each  lobule  of  the  lung  of  the  Mammal  are  arranged 
around  the  central  passage  in  such  numbers,  that  the  outer  ones  can  only 
communicate  with  this  passage  through  the  medium  of  those  which  are  nearer 
the  middle  of  the  cluster.  Those  cells  which  communicate  directly  with  the 
bronchial  tubes  and  intercellular  passages,  open  into  them  by  large  circular 
apertures  ;  and  they  are  themselves  similarly  opened  into  by  other  cells,  which 
again  communicate  with  others  beyond  them ;  so  that  each  of  the  openings 
in  the  air-passage  leads  to  a  series  of  air-cells,  extending  from  it  to  the  surface 
of  the  lobule.  These  cells  have  also  lateral  communications  with  each  other. 
The  walls  of  the  air-cells  are  formed  of  a  very  thin  and  transparent  mem- 
brane, which  is  folded  sharply  at  the  orifices  of  communication,  so  as  to 
form  a  very  definite  border  to  them;  and  the  capillary  plexus  is  so  placed 
between  the  two  layers,  which  form  the  walls  of  two  adjacent  air-cells,  as  to 
expose  one  of  its  surfaces  each ;  by  which  provision,  the  full  influence  of  the 
air  upon  it  is  secured. 
49 


578  OF  RESPIRATION. 

a.  It  appears  from  the  researches  of  M.  Bourgery,*  that  the  development  of  the  air-cells 
continues  in  the  human  subject  up  to  the  age  of  thirty,  at  which  time  the  capacity  for  re- 
spiration is  the  greatest;  it  subsequently  decreases,  especially  in  persons  who  suffer  from 
cough, — the  violence  of  which  expiratory  effort  frequently  causes  rupture  of  the  air-cells, 
and  thus  gradually  produces  that  emphysematous  state  of  the  lungs,  which  is  so  common  in 
elderly  persons.     The  power  of  increasing  the  volume  of  air  taken  in,  by  a  forced  inspira- 
tion, is  much  less  in  the  old  person  than  in  the  child,  though  the  average  amount  of  air  in- 
spired may  be  the  same;  hence  the  young  person  possesses  a  greater  capacity  of  respiration, 
as  it  were,  in  reserve ;  whilst  the  old  man  has  little,  and  is,  therefore,  unfit  for  great  exer- 
tion. 

b.  The  Lungs  are  developed,  in  the  first  instance,  as  diverticula  from  the  oesophageal  tube. 
In  the  Chick,  about  the  fourth  day,  a  little  sacculus  is  described  as  shooting  forth  at  its  pos- 
terior and  inferior  part;  and  this   soon  subdivides  at  its  lower  part  into  two;  at  the  same 
time  becoming  more  separated  from  the  tube,  by  a  constriction  around  the  neck,  which  soon 
elongates  so  as  to  form  the  trachea.     On  the  fifth  or  sixth  day,  the  lung  of  one  side  is  com- 
pletely distinct  from  that  of  the  other,  and  each 

Fi°\  220.  i§  Attached  to  the  common  pedicle  by  a  pecu- 

liar branch,  the  future  bronchus.     The  upper 
portion  has  much  thicker  walls  than  the  lower ; 
and  these  appear  to  contain  a  large   quantity 
of  vesicular  parenchyma,  in  which  the  rami- 
fications of  the  bronchial  tubes  subsequently 
extend  themselves.     About  the  tenth  or  ele- 
venth day  of  incubation,  these  ramifications 
possess  nearly  their  permanent  character  and 
situation.     The  first  trace  of  the  Glottis  ap- 
First  appearance  of  the  lungs  ;  a,  in  a  Fowl  at      pears   about  the  fifth  day;  it  is  then  a  mere, 
four  days  ;  6,  in  a  Fowl  at  six  days  ;  c,  terrnina-       slit  in  the  walls  of  the  oesophagus,  resembling 
lion  of  bronchus  in  a  very  young  Pig,  that  by  which  the  ductus  pneumaticus  of  some 

Fishes,  opens  into  the  alimentary  canal.  The 

formation  of  the  cartilaginous  rings  of  the  trachea  does  not  commence  until  after  the  twelfth 
day,  when  they  first  appear  as  transverse  striae  on  the  median  line  of  the  front  only ;  they 
gradually  become  solid,  and  extend  themselves  on  either  side,  until  they  nearly  meet  at  last 
on  the  median  line  on  the  back  or  vertebral  side  of  the  tube. 

c.  The  history  of  the  process  in  the  Human  embryo,  appears  to  be  very  nearly  the  same. 
The  first  appearance  of  the  Lungs  takes  place  about  the  sixth  week,  at  which  time  they  are 
simple  vesicular  prolongations  of  the  cesophageal  membrane.     Their  surface,  however,  soon 
becomes  studded  with  numerous  little  wart-like  projections;  and  these  are  caused  by  the 
formation  of  corresponding  enlargements  of  their  cavity.     These  enlargements  soon  become 
prolonged,  and  develope  corresponding  bud-like  enlargements  from  their  sides ;  and  in  this 
manner,  the  form  of  the  organs  is  gradually  changed,  a  progressive  increase  in  their  bulk 
taking  place  from  above  downwards,  in  consequence  of  the  extension  of  the  bronchial  ra- 
mifications from  the  single  tube  at  the  apex.     At  the  same  time,  however,  a  corresponding 
increase  in  the  amount  of  the  parenchymatous  tissue  of  the  lung  is  taking  place ;  for  this  is 
deposited  in  all  the  interstices  between  the  bronchial  ramifications,  and  might  be  compared 
with  the  soil  filling  up  the  spaces  amongst  the  roots  of  a  tree.     It  is  in  this  parenchyma  that 
the  pulmonary  vessels  are  distributed ;  and  the  portion  of  it  which  extends  beyond  the  ter- 
minations of  the   bronchial   tubes,  seems  to  act  as  the  nidus  for  their  further  extension.     It 
can  be  easily  shown  that,  up  to  a  late  period  of  the   development  of  the  lungs,  the  dilated 
terminations  of  the  bronchi  constitute  the  only  air-cells  (Fig.  220,  c) :  but,  as  already  men- 
tioned, the  parenchyma  subsequently  has  additional  cavities  formed  within  it. — It  is  a  fact 
of  some  interest,  as  an  example  of  the  tendency  of  certain  diseased  conditions  to  produce  a 
return  to  forms  which  are  natural  to  the  fcetal  organism,  or  which  present  themselves  in  other 
animals, — that  up  to  a  late  period  in  the  development  of  the  Human  embryo,  the  lungs  do 
not  nearly  fill  the  cavity  of  the  chest,  and  the  pleura  of  each  side  contains  a  good  deal  of 
serous  fluid. 

758.  The  network  of  vessels  on  the  walls  of  the  air-cells  is  so  minute,  that 
the  diameter  of  the  meshes  is  scarcely  so  great  as  that  of  the  capillary  ves- 
sels which  inclose  them.  According  to  Mr.  Addison,  the  capillaries  in  the 
lung  of  a  Toad  admit,  in  their  natural  state,  no  more  than  one,  or  at  most  two 
rows  of  blood-corpuscles ;  and  the  islets  of  tissue  between  them  are  compa- 

*  Archives  Generates  de  Medecine,  Mars  1843. 


STRUCTURE  AND  DEVELOPMENT  OF  HUMAN  LUNG. 


579 


Arrangement  of  the  Capillaries  of  the  air-cells  of 
the  Human  Lung. 


ratively  large  ;  whilst,  if  the  lung  Fig.  221. 

be  congested  or  inflamed,  five  or 
six  rows  of  corpuscles  are  seen  in 
the  vessels  ;  and  the  islets  of  tissue 
are  almost  entirely  obliterated. — 
The  diameter  of  the  Human  air- 
cells  is  about  twenty  times  greater 
than  that  of  the  capillaries  which 
are  distributed  upon  their  parietes  ; 
varying  (according  to  the  measure- 
ment of  Weber)  from  the  l-200th 
to  the  l-70th  of  an  inch.  It  has 
been  calculated  by  M.Rochoux,  that 
as  many  as  17,790  air-cells  are 
grouped  around  each  terminal  bron- 
chus ;  and  that  their  total  number 
amounts  to  no  less  than  600  mil- 
lions. 

759.  The  fibrous  coat  of  the  bronchial  tubes  possesses  a  considerable  amount 
of  contractility,  which  can  scarcely  be  regarded  as  otherwise  than  muscular. 
From  the  experiments  of  Dr.  C.  B.  Williams,*  it  appears  that  all  the  air- 
tubes  are  endowed  with  a  considerable  amount  of  contractility,  which  may 
be  excited  by  electrical,  chemical,  or  mechanical  stimuli,  applied  to  them- 
selves ;  but  this  is  not  so  readily  excitable  through  their  nerves,  although  the 
experiments  of  Volkmann  and  Longet  have  clearly  shown  the  possibility  of 
thus  calling -it  into  action  (§  410).  This  contractility  resembles  that  of  the 
intestines  or  arteries,  more  than  that  of  the  voluntary  muscles  or  heart ;  the 
contraction  and  relaxation  being  more  gradual  than  that  of  the  latter,  though 
less  tardy  than  that  of  the  former.  It  is  chiefly  manifested  in  the  smaller 
bronchial  tubes  ;  since,  in  the  trachea  and  the  larger  bronchi,  the  cartilaginous 
rings  prevent  any  decided  diminution  in  the  calibre  of  the  tube.  Wedemeyer 
did  not  succeed  in  producing  any  distinct  contraction  of  the  fibres  of  the  tra- 
chea and  larger  bronchi ;  but  he  states  that  tubes  of  less  than  a  Ime  in  dia- 
meter could  be  perceived  to  contract  gradually  under  the  stimulus  of  galva- 
nism, until  their  cavity  was  nearly  obliterated.  It  is  remarked  by  Dr.  Williams, 
that  the  contractility  of  the  bronchial  muscles  is  soon  exhausted  by  the  action 
of  a  stimulus ;  but  that  it  may  in  some  degree  be  restored  by  rest,  even  when 
the  lung  is  removed  from  the  body.  When  the  stimulation  is  long  continued, 
however,  as  by  intense  irritation  of  the  mucous  membrane  during  life,  the 
contractile  tissue  passes  into  a  state  which  resembles  that  of  the  tonic  con- 
traction of  muscular  fibre  (§  593).  The  contractility  is  greatly  affected  by 
the  mode  of  death,  and  is  remarkably  diminished  by  the  action  of  vegetable 
narcotics,  particularly  stramonium  and  belladonna ;  whilst  it  seems  to  be  scarcely 
at  all  affected  by  hydrocyanic  acid. — These  facts  are  very  important,  as 
throwing  light  upon  certain  diseased  conditions.  It  has  long  been  suspected, 
that  the  dyspnoea  of  Spasmodic  Asthma  depends  upon  a  constricted  state  of 
the  smaller  bronchial  tubes,  excited  through  the  nervous  system,  frequently 
by  a  stimulating  cause  at  some  distance ;  and  there  can  now  be  little  doubt 
that  this  is  the  case.  The  peculiar  influence  of  stramonium  and  belladonna, 
in  diminishing  the  contractility  of  these  fibres,  harmonizes  remarkably  with 
the  well-known  fact  of  the  relief  frequently  afforded  by  them  in  this  distress- 
ing malady. 

760.  The  Lungs  themselves  are  to  be  regarded   as  quite  passive  in  the 


*  Athenaeum  Report  of  the  Meeting  of  the  British  Association,  1840,  p.  802. 


580  OF  RESPIRATION. 

movements  of  respiration ;  the  renewal  of  their  contained  air  being  accom- 
plished by  the  action  of  the  muscles  external  to  the  thorax,  or  partly  forming 
its  parietes.  The  lung  completely  fills  the  cavity  of  the  pleura,  in  the  healthy 
state  at  least;  so  that,  when  this  is  enlarged,  a  vacuum  is  produced,  which 
can  only  be  filled  by  a  corresponding  enlargement  of  the  lung ;  and  to  pro- 
duce this,  the  air  rushes  down  the  trachea,  and  passes  to  the  remotest  air-cells. 

a.  The  distension  of  the  whole  tissue  of  the  lung,  which  is  effected  in  this  manner,  is 
much  more  complete  than  that,  which  could  be  occasioned  by  simple  insufflation  from  the 
trachea ; — a  fact  of  which  it  has  been  proposed  to  take  advantage  in  juridical  inquiries  in 
regard  to  suspected  cases  of  Infanticide,  where  the  lungs  are  found  to  float,  and  the  defence 
is  set  up  that  the  child  was  still-born,  and  that  air  was  blown  into  the  chest  for  the  purpose 
of  resuscitating  it.     It  has  been  ascertained  by  the  experiments  of  Mr.  Jennings,*  that  if  a 
piece  of  lung,  which  has  been  filled  with  air  by  insufflation,  be  exposed  to  great  pressure, 
the  air  may  be  expelled  from  it  sufficiently  to  cause  it  to  sink  in  water;  but  that  no  pressure 
can  produce  the  same  effect  upon  that  which  has  been  filled  by  a  natural  inspiratory  effort. 
It  is  a  serious  objection  to  the  use  of  this  test  of  juridical  investigations,  however,  that  the 
early  inspiratory  efforts  of  the  infant  are  often  so  feeble,  as  to  produce  but  a  very  imperfect 
dilatation  of  the  air-cells;  so  that  the  lung  of  an  infant  which  has  naturally  inspired  cannot, 
by  such  means,  be  distinguished  from  one  that  has  been  artificially  inflated.     The  fact  ascer- 
tained by  Mr.  J.,  however,  is  one  of  much  physiological  interest. — Owing  to  the  freedom 
with  which  the  air  enters  the  lungs,  when  there  is  no  abnormal  obstruction,  the  external 
surface  is  always  in  contact  with  the  walls  of  the  chest,  so  that  the  pulmonary  and  costal 
pleurae  glide  over  one  another  with  every  inspiration  and  expiration.     The  smooth  and 
moistened  character  of  their  surface  prevents  the  movement  from  producing  any  sound;  but 
it  becomes  evident  when  the  friction  is  increased,  either  by  the  dryness  that  is  commonly 
one  of  the  early  changes  produced  by  inflammation,  or  by  the  rough  deposit  that  subsequently 
appears. 

b.  The  complete  dependence  of  the   expansion  of  the  Lungs  upon  the  production  of  a 
vacuum  in  the  chest,  is  well  shown  by  the  effect  of  admission  of  air  into  the  pleural  cavity. 
When  an  aperture  is  made  on  either  side,  so  that  the  air  rushes  in  at  each  inspiratory 
movement,  the  expansion  of  the  lung  on  that  side  is  diminished,  or  entirely  prevented,  in 
proportion  to  the  size  of  the  aperture.     If  air  can  enter  through  it  more  readily  than  through 
the  trachea,  an  entire  collapse  of  the  lung  takes  place;  and  by  making  such  an  aperture  on 
each  side,  complete  asphyxia  is  produced.     But  if  it  be  too  small  to  admit  the  very  ready 
passage  of  air,  the  vacuumi produced  by  the  inspiratory  movement  is  more  easily  filled  by  the 
distension  of  the  lungs,  than  by  the  rush  of  air  into  the  pleural  cavity ;  so  that  a  sufficient 
amount  of  change  takes  place  for  the  maintenance  of  life.     This  is  frequently  observed  in 
the  case  of  penetrating  wounds  of  the  thorax,  in  the  surgical  treatment  of  which,  it  is  of 
great  importance  to  close  the  aperture  as  completely  as  possible  ;  when  this  has  been  accom- 
plished, the  air  that  had  found  its  way  into  the  cavity  is  soon  absorbed,  and  the  lung  re- 
sumes its  full  play.     When  one  lung  is  obstructed  by  tubercular  deposit,  or  is  prevented  in 
any  other  way  from  rightly  discharging  its  function,  an  opening  that  freely  admits  air  into 
the  pleural  cavity  of  the  other  side,  is  necessarily  attended  with  an  immediately  fatal  result; 
and  in  this  manner  it  not  unfrequently  happens,  that  chronic  pulmonary  diseases  suddenly 
terminate  in  Asphyxia,  a  communication  being  opened  by  ulceration  between  a  bronchial 
tube  and  the  cavity  of  the  thorax. 

761.  The  dilatation  of  the  chest  during  Inspiration,  is  chiefly  accomplished 
by  the  contraction  of  the  Diaphragm,  which,  from  the  high  arch  that  it  pre- 
viously formed,  becomes  nearly  plane;  in  this  change  of  figure,  it  presses  on 
the  abdominal  viscera,  so  as  to  cause  them  to  protrude,  which  they  are  ena- 
bled to  do  by  the  relaxation  of  the  abdominal  muscles.  In  ordinary  tranquil 
breathing,  the  action  of  the  diaphragm  is  alone  nearly  sufficient  to  produce 
the  necessary  exchange  of  air;  but,  when  a  full  inspiration  is  required,  the 
cavity  of  the  chest  is  dilated  laterally,  as  well  as  inferiorly.  This  is  accom- 
plished by  the  Intercostal  muscles,  the  Scaleni,  Serrati,  and  others ;  which, 
by  elevating  the  ribs,  bring  them  and  their  cartilages  more  nearly  into  the 
same  direction,  and  thus  separate  them  more  widely  from  the  median  line. 
Expiration  is  chiefly  effected  by  the  contraction  of  the  abdominal  muscles, 
which  at  the  same  time  force  up  the  diaphragm  by  their  pressure  on  the  vis- 

*  Transactions  of  the  Provincial  Medical  and  Surgical  Association,  vol.  ii. 


ACTION  OF  THE  LUNGS  IN  RESPIRATION.  581 

cera,  and  depress  the  ribs ;  in  the  latter  movement  they  are  aided  by  the 
Longissimus  Dorsi,  Sacrolumbalis,  &c.,  and  also  by  the  elasticity  of  the  car- 
tilages of  the  ribs,  with  that  of  the  air-cells  and  air-tubes  themselves. 

762.  It  is  difficult  to  form  an  estimate  by  observations  on  one's  self,  of  the 
usual  number  and  degree  of  the  respiratory  movements;  since  the  direction  of 
the  attention  to  them  is  certain  to  increase  their  frequency  and  amount.     In 
general  it  may  be  stated,  that  from  14  to  18  alternations  usually  occur  in  a 
minute;  of  these  the  ordinary  inspirations  involve  but  little  movement  of  the 
thorax  ;  but  a  greater  exertion  is  made  at  about  every  fifth  recurrence.     The 
average  numerical  proportion  of  the  respiratory  movements,  to  the  pulsations 
of  the  heart,  is  about  1  to  5  or  4| ;  and  when  this  proportion  is  widely  de- 
parted from,  there  is  reason  to  suspect  some  obstruction  to  the  aeration  of  the 
blood,  or  some  disorder  of  the  nervous  system.     Thus  in  Pneumonia,  in  which 
a  greater  or  less  amount  of  the  lung  is  unfit  for  its  office,  the  number  of  respira- 
tions increases  in  a  more  rapid  proportion  than  the  acceleration  of  the  pulse ; 
so  that  the  ratio  becomes  as  1  to  3,  or  even  1  to  2,  in  accordance  with  the  de- 
gree of  engorgement.*     In  Hysterical  patients,  however,  a  similar  increase, 
or  even  a  greater  one,  may  take  place  without  any  serious  cause;  thus  Dr. 
Elliotsont  mentions  a  case,  in  which  the  respiratory  movements  of  a  young 
female,  through  nervous  affection,  were  98  or  even  106,  whilst  the  pulse  was 
104.     On  the  other  hand,  the  respirations  in  certain  typhoid  conditions  and 
in  narcotic  poisoning  become  abnormally  slow,  owing  to  the  torpid  condition  of 
the  nervous  centres,  the  proportion  being  1  to  6,  or  even  1  to  8 ;  and  in  such 
cases,  the  lungs  not  unfrequently  become  cedematous,  from  the  cause  formerly 
mentioned  (§  411). 

763.  The  amount,  also,  of  the  Respiratory  Movements  is  affected  by  vari- 
ous morbid  conditions  ;  thus  when  dislocation  of  the  spine  takes  place  above 
the  origin  of  the  intercostal  nerves,  but  below  that  of  the  phrenic,  so  that  the 
former  are  paralyzed,  the  respiratory  movement  is  confined  to  the  diaphragm  ; 
and  as  this  is  insufficient,  serum  is  effused  into  the  lungs,  and  a  slow  Asphyxia 
supervenes,  which  usually  proves  fatal  in  from  three  to  seven  days.     Even 
where  the  muscles  and  nerves  are  all  capable  of  action,  the  full  performance 
of  the  inspiratory  movements  is  prevented,  by  the  solidification  or  engorge- 
ment of  any  par.t  of  the  lung,  which  interferes  with  its  free  distension  ;  or  by 
adhesions  between  the  pleural  surfaces,  which  offer  a  still  more  direct  impedi- 
ment. When  these  adhesions  are  of  long  standing,  they  are  commonly  stretched 
into  bands,  by  the  continual  tension  to  which  they  are  subjected.     If  the 
impeding  cause  affect  both  sides,  the  movements  of  both  will  be  alike  inter- 
fered with;  but  if  one  side  only  is  affected,  its  movements  will  be  diminished, 
whilst  those  of  the  other  remain  natural ;  and  the  physician  hence  frequently 
derives  an  indication  of  great  value,  in  regard  to  the  degree  in  which  the  lung 
is  incapable  of  performing  its  functions.     It  is  to  be  remembered,  however, 
that  the  action  both  of  the  diaphragm  and  of  the  elevators  of  the  ribs  may  be 
prevented,  by  pain  either  in  the  muscles  themselves  or  in  the  parts  which  they 
move ;  thus  the  descent  of  the  diaphragm  is  checked  by  inflammation  of  the 
abdominal  viscera  or  of  the  peritoneum  ;  and  that  of  the  intercostals  by  rheu- 
matism, pleuritis,  pericarditis,  or  other  painful  disorders  of  the  parts  forming 
the  parietes  of  the  thorax  (§  431). 

764.  The  capacity  of  the  Lungs  for  air  varies  considerably  in  different  in- 
dividuals ;  and  as  the  most  complete  expiration  does  not  by  any  means  empty 

*  See  a  Paper  by  Dr.  Hooker,  on  the  Relation  between  the  Respiratory  and  Circulating 
Functions,  in  the  Boston  (N.  E.)  Medical  and  Surgical  Journal ;  an  abstract  of  which  will  be 
found  in  British  and  Foreign  Medical  Review,  vol.  vi.  p.  263. 

t  Physiology,  p.  215.  note. 

49* 


582  OF  RESPIRATION. 

them,  it  is  not  possible  to  ascertain  it  with  accuracy.  But  the  amount  which 
can  be  expelled  by  a  forcible  expiration,  after  a  full  inspiration,  may  be  taken 
as  a  measure  of  the  comparative  "  capacity  of  respiration"  in  different  indi- 
viduals ;  and  the  researches  of  Mr.  Hutchinson  have  shown  that,  in  the  state 
of  health,  this  bears  a  very  constant  proportion  to  the  height.  Thus  he  found 
that  the  average  capacity  of  men  of  5  ft.  7  in.  is  about  224  cubic  inches,  whilst 
that  of  men  of  5  ft.  2  in.  is  about  173  cubic  inches,  and  that  of  men  of  6  feet, 
about  255  cubic  inches.  The  size  of  the  chest  affords  no  good  indication  of 
the  capacity  of  expiration.  The  results  of  such  examinations  are  so  nearly 
uniform,  that  disease  may  be  suspected  in  any  man,  who  cannot  blow  out 
nearly  so  many  cubic  inches  as  the  average  of  those  of  the  same  height ;  the 
only  exceptions  among  healthy  subjects,  being  in  the  case  of  fat  men,  whose 
capacity  is  always  low. — It  is  obvious  from  these  facts,  that  the  amount  of  air 
ordinarily  respired  will  vary  greatly  in  different  individuals  ;  and  this  is  doubt- 
less one  source  of  the  discrepancy  of  the  results  of  the  various  experiments, 
which  have  been  made  to  determine  this  point.  Some  of  the  most  recent  ex- 
periments on  the  subject  are  those  of  Mr.  Coathupe,*  in  which  the  Author  has 
much  reason  to  feel  confidence.  According  to  his  estimate,  about  266£  cubic 
feet,  or  460,224  cubic  inches  of  air,  pass  through  the  lungs  of  a  middle-sized 
man  in  24  hours;  reckoning  the  average  number  of  inspirations  at  16  per 
minute,  this  would  give  20  cubic  inches  as  the  amount  inhaled  at  each. 

2. — Effects  of  Respiration  on  the  Mr. 

765.  We  naturally  pass  from  the  foregoing  inquiries,  to  those  that  relate  to 
the  alterations  in  the  Air,  which  are  effected  by  Respiration.  These  mainly 
consist  in  the  removal  of  a  portion  of  the  Oxygen,  and  the  substitution  of  a 
quantity  of  Carbonic  Acid,  rather  less  in  bulk  than  the  Oxygen  which  has 
disappeared.  The  proportion  of  the  air  thus  changed  appears  to  vary  accord- 
ing to  the  frequency  of  the  respirations.  Thus  Vierordt  found  that,  if  he  only 
respired  six  times  in  a  minute,  the  quantity  of  Carbonic  acid  was  5*5  per 
cent,  of  the  whole  air  exhaled ;  with  twelve  respirations,  it  was  4*2 ;  with 
twenty-four,  it  was  3*3 ;  with  forty-eight,  it  was  3*0  ;  and  with  ninety-six,  it 
was  2*6  per  cent.  In  some  of  the  experiments  of  Messrs.  Allen  and  Pepys, 
it  was  as  much  as  8  per  cent.  Probably  about  4  per  cent,  may  be  taken  as 
the  average,  at  the  ordinary  rate  of  respiration. — It  appears,  however,  from  the 
researches  of  the  last-named  experimenters,  that  if  the  air  be  already  charged 
in  some  degree  with  Carbonic  acid,  the  quantity  exhaled  is  much  less  ;  for 
when  300  cubic  inches  of  air  were  respired  for  three  minutes,  only  28£  cubic 
inches  (9£  per  cent.)  of  Carbonic  acid  were  found  in  it;  although  the  previous 
rate  of  its  production,  when  fresh  air  was  taken  in  at  every  respiration,  was 
32  cubic  inches  in  a  minute.  Knowing,  then,  the  necessity  of  a  free  excre- 
tion of  carbonic  acid,  we  are  led  by  this  fact  to  perceive  the  high  importance 
of  ventilation ;  for  it  is  not  sufficient  for  health,  that  a  room  should  contain  the 
quantity  of  air  requisite  for  the  support  of  its  inhabitants  during  a  given  time  ; 
since  after  they  have  remained  in  it  but  a  part  of  that  time,  the  quantity  of 
carbonic  acid  which  its  atmosphere  will  contain,  will  be  large  enough  to  inter- 
fere greatly  with  the  due  aeration  of  their  blood,  and  will  thus  cause  oppres- 
sion of  the  brain  and  the  other  morbid  affections  that  result  from  the  accumu- 
lation of  carbonic  acid  in  the  circulating  fluid. — On  the  other  hand,  it  has  been 
ascertained  by  the  recent  experiments  of  Dr.  Boswell  Reid  that,  if  the  carbonic 
acid  be  removed  as  fast  as  it  is  formed,  an  animal  may  remain  in  a  limited 
quantity  of  air,  without  much  inconvenience,  until  nearly  the  whole  of  its 

*  Athenaeum  Report  of  Meeting  of  the  British  Association,  1839;  p.  707. 


EXCHANGE  OF  OXYGEN  AND  CARBONIC  ACID.  583 

oxygen  is  exhausted  ; — thus  showing  that  the  respirability  of  air  does  not  de- 
pend so  much  upon  the  proportion  of  oxygen  it  contains,  as  upon  its  freedom 
from  contamination  with  carbonic  acid  or  other  poisonous  gases. 

766.  The  reaction  which  thus  takes  place  between  the  Air  and  the  Blood, 
is  easily  explained  upon  physical  principles.     If  the  Blood  come  to  the  Lungs 
charged  with  Carbonic  acid,  and  is  exposed  in  their  cells  to  the  influence  of 
atmospheric  air,  which  is  a  mixture  of  Oxygen  and  Nitrogen,  an  endosmose 
and  exosmose  of  gases  will  take  place,  according  to  certain  fixed  laws.*     The 
Carbonic  acid  of  the  blood  will  pass  out,  to  be  replaced  by  Oxygen  and  Ni- 
trogen ;  and  the  quantity  of  the  former  which  enters  will  be  much  greater  than 
that  of  the  latter,  on  account  of  the  superior  facility  with  which  oxygen  passes 
through  porous  membranes.     If  the  venous  blood  also  contain  Nitrogen  as 
well  as  carbonic  acid,  this  also  will  pass  out,  to  be  replaced  by  the  Oxygen  of 
the  air.     Thus,  there  will  be  a  continual  Exosmose  of  Carbonic  acid  and  Ni- 
trogen, and  a  continual  Endosmose  of  Oxygen  and  Nitrogen.     The  exhalation 
and  absorption  of  Nitrogen  appear  usually  to  balance  each  other;  so  that  the 
amount  of  this  gas  in  the  respired  air  undergoes  little  or  no  change.     But  the 
case  is  different  in  regard  to  the  exchange  of  Carbonic  acid  and  Oxygen. 
According  to  the  law  of  mutual  diffusion  of  gases,  the  volume  of  Oxygen  that 
is  taken  in,  should  exceed  that  of  the  Carbonic  acid  which  passes  out,  in  the 
proportion  of  1174  to  1000.     This  calculation,  deduced  from  the  relative 
densities  of  the  two  gases,  corresponds  so  closely  with  the  actual  results  of 
experiments  upon  the  respiration  of  Man,  that  the  interchange  may  be  regarded 
as  always  taking  place  in  accordance  with  the  law  of  mutual  diffusion ;  so 
that,  from  the  amount  of  Carbonic  acid  exhaled,  the  quantity  of  Oxygen  ab- 
sorbed may  be  readily  calculated.!     Now  as  Carbonic  acid  contains  its  own 
bulk  of  Oxygen,  it  follows  that  the  amount  of  Oxygen  absorbed  exceeds  that 
which  is  given  off,  by  174  parts  in  every  1000 ;  so  that  a  quantity  of  oxygen, 
equal  to  more  than  one-sixth  of  that  which  is  converted  into  Carbonic  acid,  is 
employed  in  the  system  for  other  purposes.     It  appears  probable  that  a  part 
of  this  additional  Oxygen  is  made  to  combine  with  Hydrogen  furnished  by  the 
food  or  by  the  disintegration  of  the  tissues  ;  and  that  the  water  thus  generated 
forms  part  of  that  exhaled  from  the  lungs ;  whilst  another  part  will  be  applied 
to  the  oxidation  of  the  Sulphur  and  Phosphorus,  which  are  taken  in  as  such 
in  the  food,  and  which,  after  forming  part  of  the  solid  tissues,  are  excreted  in 
the  condition  of  Sulphuric  and  Phosphoric  acids, — chiefly  through  the  kidneys. 

767.  The  absolute  quantity  of  Carbonic  Acid  exhaled  from  the  Lungs  is 
liable  to  variation  from  so  many  sources,  that   no  fixed  standard  can  be 
assigned  for  it.     The  mean  of  a  great  number  of  observations,  however, 
made  in  different  modes,  and  under  different  circumstances,  would  give  about 
160  grains  of  Carbon  per  hour  as  the  amount  set  free  by  a  well-grown  adult 
man,  under  ordinary  circumstances.      Taking  this  as  the  average    of  the 
twenty-four  hours,  the  total  quantity  of  Carbon  thus  daily  expired  from  the 
Lungs  would  be  3840  grains,  or  8  oz.  Troy.     The  chief  causes  of  variation 
are, — the  Temperature  of  the  surrounding  medium,  Age,  Sex,  Development 
of  the  body,  state  of  Health  or  Disease,  Muscular  Exertion  or  Repose,  Sleep 
or  Watchfulness,  Period  of  the  Day,  and  state  of  the .  Digestive  process. 
These  will  now  be  considered  in  detail. 

a.  Temperature  of  surrounding  Medium.  —  The  amount  of  Carbonic  Acid  exhaled  by 
warm-blooded  animals  is  greatly  increased  by  external  Cold,  and  diminished  by  Heat;  as  is 
shown  by  the  following  results  of  comparative  experiments  upon  the  quantity  set  free  by 
the  same  animals,  at  low,  medium,  and  high  temperatures,  in  periods  of  an  hour  (Letellier). 


*  See  Principles  of  General  and  Comparative  Physiology,  §§  437 — 9. 
j"  Valentin's  Lehrbuch  der  Physiologic,  vol.  i.,  pp.  507-SSO. 


584  OF  RESPIRATION. 

Temp,  about  32°.  Temp.  59°— 68°.  Temp.  86°— 106°. 

Grammes.  Grammes.  Grammes. 

A  Canary     -         -.        -         0-325  0-250  0-129 

A  Turtle-Dove     -        -         0-974  0*684  0-336 

Two  Mice  -        -         -         0-531  0-498  0-268 

A  Guinea-Pig       -         -         3'006  2-080  1-453 

From  this  table  it  appears  that  the  quantity  of  carbonic  acid  exhaled  by  Mammals  between 
86°  and  106°  is  less  than  half  that  set  free  near  the  freezing-point;  whilst  that  which  is 
exhaled  between  59°  and  68°  is  but  little  more  than  two-thirds  of  the  same  amount.  The 
diminution  occasioned  by  heat  is  still  more  remarkable  in  Birds;  which  exhaled  at  the 
highest  temperature  scarcely  more  than  one-third  of  that  set  free  at  the  lowest.  The  ob- 
servations of  Vierordt  upon  himself  show  that  the  same  is  true  of  the  Human  subject ;  a 
difference  of  10°  Fahr.,  according  to  him,  producing  a  variation  of  rather  more  than  two 
cubic  inches  in  the  amount  of  Carbonic  Acid  hourly  expired. 

b.  Age. — The  amount  of  Carbonic  Acid  exhaled  increases  in  both  sexes  up  to  about  the 
thirtieth  year;  it  remains  stationary  until  about  the  forty-fifth ;  and  then  diminishes.     The 
following  are  the  comparative  results  of  experiments  upon  males  of  different  ages,  and  of  a 
moderate  degree  of  muscular  development  (Andral  and  Gavarret). 

Carbon  exhaled  Carbon  exhaled 

Age.  per  hour.  Age.  •  per  hour. 

8  years     -         -       77-0  grains  37  years  -         -     164-7  grains. 

12  "         -         -     113-9      "  48     "  -         -     161-7      " 
14     «         -         -     126-2      "  59     "  -         -     154-0      « 

'  20     "         -         -     166-3      "  68     "         -         -     147-8      " 

26     "         -         -     169-4      "  76     "         -         -       92-4      " 

c.  Sex. — At  all  ages  beyond  eight  years,  the  exhalation  is  greater  in  Males  than  in  Fe- 
males.    Nearly  the  same  proportionate  increase  takes  place,  however,  in  females,  up  to  the 
time  of  puberty;  when  the  quantity  abruptly  ceases  to  increase,  and  remains  stationary  so 
long  as  they  continue  to  menstruate.     When,  however,  menstruation  has  ceased,  the  exhala- 
tion of  carbonic  acid  begins  again  to  augment;  and  then  again  diminishes,  with  the  advance 
of  years,  as  in  men.     Should  menstruation  temporarily  cease  at  any  time,  the  exhalation  of 
carbonic  acid  immediately  undergoes  an  increase,  precisely  as  at  the  final  cessation  of  the 
function.     And  during  pregnancy,  the  exhalation  increases  in  like  manner.     The  following 
table  of  the  comparative  respiration  of  females  at  different  ages,  will  serve  at  the  same 
time  for  comparison  with  the  preceding,  so  as  to  exhibit  the  general  difference  between  the 
two  sexes,  at  ages  nearly  corresponding ;  and  also  to  indicate  the  peculiar  modifications 
induced  by  the  operations  of  the  genital  system  (Andral  and  Gavarret). 

Carbon  exhaled  After  Cessation  of  Catamenia. 

Age.                        per  hour.  Carbon  exhaled 

10  years     -         -     92-4  grains  Age.                           per  hour. 

13  «         -         -     97-0      "  38  years     -         -     120-3  grains. 
During  Menstrual  life.  49     «         -         -     113-9      " 

15^  years  -  -  97-0  grains.                         52     «         -         -     115-5      " 

26       "  -  97-0      "  56     "         -         -     119-3      " 

32       "  -  -  95-4      «                              66     «         -         -     104-7      " 

45       "  -  -  95-4      «                             76     "•       -        -     101-4      " 

During  Pregnancy.  82     «         -         -       92-4      " 

22  years  -  -  129-3  grains. 

32     "  -  -  126-7      « 

42     "  -  -  120-3      " 

d.  Development  of  the  Body. — The  more  robust  the  individual,  cateris  paribus,  the  more 
Carbonic  Acid  is  exhaled ;  and  the  variation  is  much  more  influenced  by  the  development 
of  the  muscular  system,  than  by  the  height,  or  weight,  capacity  of  the  chest,  &c.     Thus,  a 
very  strong  man  of  twenty-six  years  of  age  exhaled  at  the  rate  of  217-1  grains  per  hour; 
when  a  man  of  moderate  muscular  power  set  free  but  169-4  grains  in  the  same  time.     An- 
other robust  man  of  sixty  years  of  age  exhaled  at  the  rate  of  209-4  per  hour;  another  of 
similar  constitution,  and  sixty-three  years  of  age,  at  the  rate  of  190-9  grains  per  hour ;  and 
an  old  man  of  92  years,  who  still  preserved  an  uncommon  degree  of  energy,  and  who  in 
his  younger  days  had  boasted  of  extraordinary  muscular  powers,  exhaled  at  the  rate  of  135-5 
grains  per  hour.     So  also,  a  remarkably  vigorous  young  woman  of  nineteen  years  exhaled 
at  the  rate  of  107-8  grains  per  hour ;  another  of  twenty-two  years,  rather  less  powerful,  at 
the  rate  of  103*1  grains;  and  a  strong  woman  of  forty-four  years  (who  had  ceased  to  men- 
struate) 152-4  grains. — On  the  other  hand,  a  slender  man  of  forty-five  years,  in  the  enjoy- 


AMOUNT  OF  CARBONIC  ACID  EXHALED.  585 

merit  of  good  health,  only  exhaled  at  the  rate  of  132-4  grains  per  hour  (Andral  and  Ga- 
varret). 

e.  State  of  Health  or  Disease. — Upon  this  very  important  cause  <?f  variation,  few  accurate 
researches  have  yet  been  made.  The  per  centage  of  carbonic  acid  in  the  expired  air  has 
been  found  to  be  unusually  great  in  the  Exanthemata,  and  in  chronic  skin  diseases  (Mac- 
gregor) ;  and  it  has  been  stated  to  be  diminished  in  typhus  (Malcolm). — Thus,  the  average 
proportion  in  health  being  about  3f96  per  cent.  (Prout),  it  has  been  seen  at  8  per  cent,  in 
confluent  small-pox,  at  5  per  cent,  in  measles,  and  at  7-2  per  cent,  in  a  severe  case  of  icthyosis 
which  terminated  fatally;  whilst  in  Typhus  the  per  centage  has  been  found  to  range  from 
1*18  to  2-50.  /  But  these  statements  do  not  indicate  the  total  quantity  exhaled  in  each  case. — 
The  remarkable  increase  of  the  exhalation  in  cases  of  Chlorosis,  has  been  already  noticed; 
in  four  cases  recorded  by  Hannover,  the  hourly  expiration  was  123'6,  118-6,  116-9,  and  106-3 
grains, — the  absolute  quantity  diminishing  as  the  respirations  increased  in  rapidity. — In  chronic 
diseases  of  the  respiratory  organs,  as  might  be  anticipated,  the  amount  of  Carbonic  acid  ex- 
haled undergoes  a  sensible  diminution  (Nysten  and  Hannover). — Further  researches  are 
much  needed  on  this  subject;  but,  for  obvious  reasons,  they  cannot  be  readily  made  in  severe 
forms  of  disease. 

/.  Muscular  Exertion  or  Repose. — The  effect  of  bodily  exercise,  in  moderation,  is  to  produce 
a  considerable  increase  in  the  amount  of  carbonic  acid  exhaled,  both  during  its  continuance, 
and  for  some  little  time  subsequently  to  its  cessation.  According  to  the  observations  of  Vie- 
rordt,  the  increase  amounts  to  one-third  of  the  quantity  exhaled  during  rest ;  and  it  lasts  for 
more  than  an  hour  afterwards,  being  manifested  in  the  greater  quantity  of  air  respired,  and 
in  the  larger  per  centage  of  carbonic  acid  contained  in  it.  If  the  exercise  be  prolonged, 
however,  so  as  to  occasion  fatigue,  it  is  succeeded  by  a  diminished  exhalation. — The  connec- 
tion between  muscular  exertion  and  the  exhalation  of  carbonic  acid,  is  most  remarkably 
shown  in  Insects ;  in  which  animals  we  may  witness  the  rapid  transition  between  the  op- 
posite conditions  of  extreme  muscular  exertion,  and  tranquil  repose ;  and  in  which  the  effects 
of  these  upon  the  respiratory  process  are  not  masked  by  that  exhalation  of  carbonic  acid, 
which  is  required  in  warm-blooded  animals  simply  for  the  maintenance  of  a  fixed  tempera- 
ture. Thus  a  Humble-Bee  has  been  found  to  produce  one-third  of  a  cubic  inch  of  carbonic 
acid,  in  the  course  of  a  single  hour,  during  which  its  whole  body  was  in  a  state  of  constant 
movement,  from  the  excitement  resulting  from  its  capture ;  and  yet,  during  the  whole  twenty- 
four  hours  of  the  succeeding  day,  which  it  passed  in  a  state  of  comparative  rest,  the  quantity 
of  carbonic  acid  generated  by  it  was  absolutely  less. 

g.  Sleep  or  Watchfulness. — The  amount  of  carbonic  acid  exhaled  during  sleep  is  considera- 
bly less  than  that  set  free  in  the  waking  state.  This  is  particularly  shown  by  the  experi- 
ments of  Scharling;  who  confined  the  subjects  of  them  in  an  air-tight  chamber,  within 
which  they  could  sleep,  take  their  meals,  &c.  Thus  in  one  case,  the  hourly  exhalation  sank 
from  160  to  100,  in  another  from  194*7  to  122-3,  and  in  another  from  99  to  75-1.  The  cause 
of  this  result  is  partly  to  be  sought  in  the  cessation  of  all  muscular  exertion  (save  that  con- 
cerned in  the  maintenance  of  the  respiration) ;  and  partly  in  the  diminution  in  the  dissipa- 
tion of  the  heat  of  the  body  itself. 

h.  State  of  the  Digestive  Process. — It  is  well  established,  that  the  exhalation  of  carbonic  acid 
is  greatly  increased  by  eating,  and  that  it  is  diminished  by  fasting.  Thus  Prof.  Scharling 
states  the  hourly  exhalation  to  have  increased  in  one  instance  from  145  to  190,  after  break- 
fast and  a  walk ;  in  another  from  140  to  177  after  breakfast  alone ;  and  in  another  from  1 1 1'9 
to  188'9,  after  dinner.  It  is  remarkable  that  alcoholic  drinks  have  a  tendency  to  diminish  the 
exhalation  of  carbonic  acid,  especially  when  taken  into  an  empty  stomach;  and  strong  tea  is 
said  to  have  the  same  effect  (Prout,  Vierordt). — The  quantity  is  also  increased  by  exhilarating 
emotions,  and  decreased  by  depressing  affections  of  the  mind  (Prout). 

t.  Period  of  the  Day. — Independently  of  these  variations,  which  have  their  source  in  the 
condition  of  the  individual,  there  appears  to  be  a  slight  tendency  to  increase  in  the  quantity 
of  carbonic  acid  exhaled  during  the  early  part  of  the  day,  and  a  steady  decrease  during  the 
afternoon;  so  that,  in  the  evening  the  quantity  is  decidedly  less  than  in  the  morning.  It  is 
very  difficult  to  separate  the  effects  of  this  influence,  however,  from  those  of  the  causes  pre- 
viously adverted  to. 

768.  The  aeration  of  the  blood  may  take  place,  not  only  by  means  of  the 
Lungs,  but  also  through  the  medium  of  the  Cutaneous  surface.  In  some  of 
the  lower  tribes  of  animals,  indeed,  this  is  a  very  important  part  of  their 
respiratory  process  :  and  even  in  some  Vertebrata,  the  cutaneous  respiration 
is  capable  of  supporting  life  for  a  considerable  time.  This  is  especially  the 
case  in  the  Batrachia,  whose  skin  is  soft,  thin,  and  moist ;  and  the  effect  is 
here  the  greater,  since  the  blood  which  circulates  through  the  system  is,  from 


586  OF  RESPIRATION. 

\ 

the  small  proportion  of  it  that  has  passed  through  the  lungs,  very  imperfectly 
arterialized.  By  the  experiments  of  Bischoff  it  was  ascertained  that,  even 
after  the  lungs  of  a  Frog  had  been  removed,  a  quarter  of  a  cubic  inch  of  car- 
bonic acid  was  exhaled  from  the  skin,  during  eight  hours.  Experiments  which 
have  been  made  on  the  Human  subject  leave  no  room  for  doubt,  that  a  similar 
process  is  effected  through  the  medium  of  his  general  surface ;  for,  when  a 
limb  has  been  inclosed  for  some  hours  in  an  air-tight  vessel  containing  atmo- 
spheric air  freed  from  carbonic  acid,  a  sensible  amount  of  this  gas  has  been 
found  to  be  generated.  Moreover,  it  has  been  observed  not  unfrequently,  that 
the  livid  tint  of  the  skin  which  supervenes  in  Asphyxia,  owing  to  the  non- 
arterialization  of  the  blood  in  the  lungs,  has  given  place  after  death  to  the 
fresh  hue  of  health,  owing  to  the  reddening  of  the  blood  in  the  cutaneous 
capillaries  by  the  action  of  the  atmosphere  upon  them.  We  have  no  means 
of  ascertaining  the  usual  amount  of  carbonic  acid  excreted  through  the  Skin, 
except  by  determining  the  whole  quantity  disengaged  from  the  body,  and  sub- 
tracting the  portion  exhaled  from  the  lungs ;  and  no  sufficiently  precise  experi- 
ments upon  this  subject  have  yet  been  made.  The  only  way  to  separate  the 
results  of  the  pulmonary  and  cutaneous  exhalation  of  carbonic  acid,  would  be 
to  confine  the  body  in  a  close  chamber,  into  which  the  product  of  the  cutaneous 
respiration  might  freely  pass ;  whilst  the  pulmonary  respiration  during  the 
same  period  should  be  measured  by  a  distinct  apparatus.  It  is  not  improbable 
that,  in  cases  of  obstruction  to  the  due  action  of  the  lungs,  the  exhalation  of 
carbonic  acid  through  the  skin  may  undergo  a  considerable  increase ;  for  we 
find  a  similar  disposition  to  vicarious  action  in  other  parts  of  the  excreting 
apparatus.  Moreover,  there  is  evidence,  that  the  interchange  of  gases  between 
the  air  and  the  blood,  through  the  skin,  has  an  important  share  in  keeping  up 
the  temperature  of  the  body  (Chap,  xvi.,  Sect.  2) ;  and  we  find  the  tempera- 
ture of  the  surface  much  elevated  in  many  cases  of  pneumonia,  phthisis,  &c., 
in  which  the  lungs  seem  to  perform  their  function  very  insufficiently. 

3. — Effects  of  Respiration  on  the  Blood. 

769.  That  an  important  change  is  effected  in  the  character  of  the  Blood,  by 
exposure  to  Atmospheric  air  in  the  lungs,  has  been  known,  from  the  time 
when  it  was  first  ascertained  that  it  is  regularly  transmitted  to  those  organs. 
The  most  obvious  part  of  this  change  is  the  alteration  in  its  colour,  from  the 
dark  purple  of  the  venous  fluid,  to  the  rich  crimson  of  the  arterial.  But  this 
alteration  is  only  the  index  of  changes  far  more  important,  which  occur  in  its 
chemical  constitution.  Respecting  the  nature  of  these  changes,  there  has 
been,  as  formerly  stated,  much  difference  of  opinion ;  some  maintaining  that 
the  carbonic  acid  exhaled  is  formed  in  the  lungs ;  and  others,  that  it  is  con- 
tained in  the  venous  blood,  and  is  truly  excreted  from  it.  The  latter  opinion, 
which  was  long  since  brought  forward  by  La  Grange  and  Hassenfratz,  has 
recently  obtained  such  full  confirmation,  from  the  experiments  of  Spallanzani, 
Edwards,  Miiller,  Bischoff,  Magnus,  and  others,  as  to  have  a  full  claim  for 
adoption  as  a  physiological  truth.  These  experiments  are  of  two  kinds  ;  first, 
those  which  show  that  an  exhalation  of  carbonic  acid  may  continue  for  a  long 
time,  when  the  animal  is  breathing  an  atmosphere  in  which  no  oxygen  exists  ; 
and,  secondly,  those  which  prove  that  much  more  carbonic  acid  exists  in  an 
uncombined  state  in  venous  blood  than  in  arterial,  whilst  more  oxygen  exists 
in  a  similar  condition  in  arterial  blood  than  in  venous.  The  results  of  these 
will  now  be  briefly  stated. — It  was  shown  by  Spallanzani,  that  Snails  might 
be  kept  for  a  long  period  in  Hydrogen,  without  apparent  injury  to  them ;  and 
that  during  this  period  they  disengaged  a  considerable  amount  of  Carbonic 
acid.  Dr.  Edwards  subsequently  ascertained  that,  when  Frogs  were  kept  in 


EFFECTS  OF  RESPIRATION  ON  THE  BLOOD.  587 

•hydrogen  for  several  hours,  the  quantity  of  carbonic  acid  exhaled  was  fully  as 
great  as  it  would  have  been  in  atmospheric  air,  or  even  greater ;  this  latter  fact, 
if  correct,  may  be  accounted  for,  by  the  superior  displacing  power,  which  (on 
the  laws  of  the  diffusion  of  gases)  hydrogen  possesses  for  carbonic  acid. 
Collard  de  Martigny  repealed  this  experiment  in  nitrogen,  with  the  same  re- 
sults. In  both  sets  of  experiments,  the  precaution  was  used  of  compressing 
the  flanks  of  the  animal,  previously  to  immersing  it  in  the  gas,  so  as  to  expel 
from  the  lungs  whatever  mixture  of  oxygen  they  might  contain.  These  ex- 
periments have  been  since  repeated  by  Miiller  and  Bergemann,  who  took  the 
additional  precaution  of  removing,  by  means  of  the  air-pump,  all  the  atmo- 
spheric air  that  the  lungs  of  the  frog  might  previously  contain,  together  with  the 
carbonic  acid  that  might  exist  in  the  alimentary  canal.  They  found  in  one  of 
their  experiments,  that  the  quantity  of  carbonic  acid  exhaled  in  hydrogen  was 
nearly  a  cubic  inch  in  65  hours ;  and  in  another,  that  nearly  the  same  amount 
was  given  off  in  nitrogen  ;  but  this  required  rather  a  longer  period.  It  appears 
from  the  table  of  their  results,*  that  the  amount  was  not  ordinarily  greater  in 
the  experiments  which  were  prolonged  for  twelve  or  fourteen  hours,  than  in 
those  which  were  terminated  in  half  the  time  ;  hence  it  may  be  inferred,  that  the 
quantity  which  the  blood  is  itself  capable  of  disengaging  is  limited,  and  that 
the  absorption  of  oxygen  is  necessary  to  enable  carbon  to  be  set  free  from  the 
tissues. — It  is  impossible,  however,  for  an  adult  Bird  or  Mammal  to  sustain 
life  for  any  considerable  time, in  an  atmosphere  deprived  of  oxygen;  since  the 
greatly-increased  rapidity  and  energy  of  all  their  vital  operations,  necessitate 
a  much  more  constant  supply  of  this  vivifying  agent,  than  is  needed  by  the 
inferior  tribes ;  and,  as  we  shall  presently  see,  the  capillary  action  necessary 
for  the  passage  of  the  blood  through  the  lungs  will  not  take  place  without  it. 
But  Dr.  Edwards  has  shown,  that  young  Mammalia  can  sustain  life  in  an 
atmosphere  of  hydrogen  or  nitrogen,  for  a  sufficient  length  of  time  to  exhale  a 
sensible  amount  of  carbonic  acid  ;  so  that  the  character  of  the  process  is  clearly 
proved  to  be  the  same  in  them,  as  in  Reptiles  and  Invertebrata. 

770.  That  the  changes  which  Venous  Blood  undergoes  in  the  lungs,  are  to 
be  explained  upon  principles  of  a  purely  chemical  and  physical  nature,  is  evi- 
dent from  the  fact,  that  the  same  changes  will  take  place  when  it  is  exposed 
to  the  air  out  of  the  body,  even  through  the  medium  of  a  thick  membrane,  such 
as  a  bladder.  Such  changes,  however,  only  affect  the  surface  of  the  fluid;  but 
this  is  exactly  what  we  should  expect,  since  the  air  has  no  access  to  the  part 
beneath.  The  Blood,  whilst  circulating  through  the  capillaries  of  the  Lungs, 
is  divided  into  an  innumerable  multitude  of  minute  streamlets,  each  so  small 
as  to  admit  but  a  single  layer  of  its  corpuscles;  and  in  these,  therefore,  the 
surface  which  is  placed  in  contact  with  the  air  is  so  enormously  extended,  as 
to  be  almost  beyond  calculation.  Hence,  then,  we  can  at  once  understand 
how  such  a  change  may  be  instantaneously  effected  in  it,  as  would  occupy 
several  hours,  when  the  blood  is  less  advantageously  exposed  to  the  influence 
of  oxygen. — In  studying  the  nature  of  these  alterations,  it  is  very  necessary 
to  ascertain  whether  Oxygen  and  Carbonic  Acid  exist  in  a  free  state  in  the 
Blood;  and  to  what  extent  their  proportions  differ  in  Venous  and  Arterial 
blood.  The  late  researches  of  Professor  Magnus  have  shown  that  Blood 
possesses  a  very  remarkable  absorbing  power  for  these  gases,  especially  for 
Carbonic  acid.  By  freely  exposing  it  to  the  latter  gas,  it  was  found  that  it 
could  take  up  as  much  as  1^  times  its  bulk;  and  that  after  all  its  Oxygen  and 
Nitrogen  had  been  thus  displaced,  it  could  still  absorb  as  much  as  16  per 
cent,  of  its  volume  of  Oxygen,  and  6*3  of  Nitrogen,  on  being  exposed  to  those 
gases  respectively.  The  usual  quantity  of  Oxygen  present  in  arterial  blood 

*  Miiller's  Physiology,  p.  341. 


588  OF  RESPIRATION. 

is,  according  to  the  experiments  of  Magnus,  about  10  per  cent.;  but  while 
passing  through  the  systemic  capillaries,  this  is  diminished  about  one-half,  so 
that  Venous  blood  does  not  contain  more  than  5  per  cent,  of  its  volume  of 
Oxygen.  On  the  other  hand,  the  Carbonic  acid  of  Arterial  blood  is  about  20 
per  cent,  of  its  volume ;  and  this  proportion  is  increased  in  Venous  blood  to 
nearly  25  per  cent.  The  amount  of  Nitrogen  varies  considerably,  being  some- 
times as  little  as  1'7  per  cent,  of  the  volume  of  the  blood,  and  sometimes 
nearly  double  that  proportion ;  it  does  not  appear  to  differ,  according  to  any 
constant  law,  in  arterial  and  venous  blood.* 

771.  There  can  be  little  doubt,  then,  that  the  changes  which  the  function 
of  Respiration  effects  in  the  Blood  have  reference  in  great  part  to  the  relative 
proportions  of  the  different  gases,  which  it  holds  in  solution.     And  although 
it  might  appear  that  the  change  of  colour,  which  the  Red  Corpuscles  undergo, 
is  a  proof  of  a  change  of  composition  in  the  Haematine  which  they  contain, 
yet  such  a  supposition  is  not  borne  out  by  experiment ;  for  no  difference  of 
composition  has  been  detected,  between  the  Haematine  of  Venous  and  that  of 
Arterial  blood ;  and  it  appears  from  the  researches  of  Peligot  on  the  action  of 
the  protoxide  of  nitrogen  upon  solutions  of  the  salts  of  the  protoxide  of  iron, 
that  liquids  may  have  their  colour  changed  by  the  absorption  of  gases,  which 
form  no  chemical  union  with  them. — There  seems  reason  to  conclude,  how- 
ever, from  the  statements  formerly  quoted  (§  115)  in  regard  to  the  difference 
between  the  Fibrine  of  Venous  and  that  of  Arterial  blood,  that  Oxygen  derived 
from  the  inspired  air  enters  into  actual  combination  with  this  element ;  and 
the  same  may  very  probably  be  true  of  other  constituents  of  the  blood : — so 
that  we  are  to  regard  the  influence  of  Respiration  as  partly  exerted  in  modify- 
ing the  proportions  of  the  gases  dissolved  in  the  blood,  substituting  Oxygen 
for  a  portion  of  its  Carbonic  Acid ;  and  partly  in  enabling  the  ingredients  of 
the  liquid  to  enter  into  new  combinations  with  the  Oxygen  of  the  air.     For 
the  reasons  formerly  stated  (§  150)  it  appears  probable  that,  whether  or  not 
their  Haematine  be  chemically  affected  by  the  change,  the  Red  Corpuscles  are 
the  chief  carriers  of  the  two  gases  to  be  interchanged,  between  the  pulmonary 
and  systemic  capillaries. 

772.  Although  the  alteration  in  the  relative  proportions  of  Oxygen  and  Car- 
bonic acid  which  it  contains,  is  doubtless  the  essential  change  effected  in  the 
Blood  by  the  Respiratory  process,  the  alteration  in  its  colour  is  the  most  ob- 
vious ;  and  this  is,  under  ordinary  circumstances,  an  indication  that  the  other 
change  has  taken  place.    Thus,  if  Arterial  blood  be  exposed,  out  of  the  body, 
to  carbonic  acid,  it  will  acquire  the  dark  hue  of  venous  blood;  and  Venous 
blood  exposed  to  it  becomes   darker  still.     On  the  other  hand,  if  Venous 
blood  be  exposed  to  Oxygen,  it  acquires  the  Arterial  hue.    The  presence  of  a 
certain  amount  of  saline  matter  appears,  from  the  experiments  of  Dr.  Stevens 
and  others,  to  be  a  condition  necessary  for  the  due  influence  of  oxygen  upon 
the  colour  of  the  blood;  since,  if  it  be  deficient,  the  contact  of  oxygen  will  not 
produce  its    usual  effect.     On   the  other  hand,  the  addition  of  saline  matter 
(especially  nitre)  will  occasion  a  decided  change  of  hue  in  venous  blood,  with- 
out any  extrication  of  carbonic  acid  or  absorption  of  oxygen. 

*  For  the  latest  researches  of  Prof.  Magnus,  which  have  had  their  origin  in  the  objections 
of  M.  Gay  Lussac  to  those  previously  published  by  him,  see  the  Annalen  der  Physik  und 
Chemie,  vol.  Ixvi.,  p.  177,  and  an  Abstract  in  the  Philosophical  Magazine,  Dec.  1845,  Suppl. 
In  these  researches,  far  greater  success  was  obtained  in  removing  the  gases  from  the  blood, 
than  in  any  previous  experiments ;  and  the  account  of  their  proportions,  therefore,  is  more 
satisfactory.  It  is  extremely  difficult  to  avoid  all  sources  of  error,  in  such  researches ;  but 
the  constancy  of  the  results  obtained  by  Magnus  indicates  that  we  may  place  much  confidence 
in  them. 


ABSORPTION  THROUGH  THE  LUNGS.  589 

a.  It  has  recently  been  attempted,  by  Mulder  and  others,  to  account  for  the  change  of  hue 
under  the  influence  of  carbonic  acid,  oxygen,  and  saline  matter,  by  a  change  of  form  in  the 
red  corpuscles ;  which  are  supposed  to  be  bi-concave  and  reflecting  in  bright  coloured  blood, 
and  bi-convex  and  refracting  in  blood  presenting  the  venous  tint.  But  the  supposition  is  not 
borne  out  by  minute  and  careful  observations  on  the  forms  of  the  corpuscles,  nor  by  varied 
experiments  on  the  effects  of  re-agents.  As  Dr.  G.  0.  Rees  has  shown,  the  blood-corpuscles 
may  be  changed  in  form,  without  any  consequent  change  of  colour ;  whilst,  on  the  other 
hand,  the  blood  is  reddened  by  saline  solutions,  whether  they  produce  endosmose  or  exos- 
mose  in  the  red  corpuscles,  thus  either  filling  or  emptying  them,  and  rendering  them  either 
bi-convex  or  bi-concave. 

773.  Exhalation  and  Absorption  by  the  Lungs. — The  alteration  in  the 
proportions  of  its  usual  gaseous  ingredients,  is  by  no  means  the  only  change 
which  the  Blood  undergoes  in  the  Lungs.     It  parts  also,  with  a  considerable 
amount  of  water,  in  the  form  of  vapour;  this  usually  contains  a  certain  pro- 
portion of  animal  matter;  and  it  is  sometimes  charged  with  volatile  substances, 
which  have  been  elsewhere  introduced  into  the  blood,  or  which  have  been 
formed  during  its  assimilation.    It  may  also  absorb  from  the  atmosphere  vola- 
tile matter  diffused  through  it.     Both  these  changes  are  probably  to  be  ex- 
plained upon  simple  physical  principles ;  being  dependent  on  the  exposure  of 
the  blood  to  the  atmosphere,  over  a  very  extensive  surface,  and  through  a 
membrane  of  great  permeability.     Of  the  fluid  ordinarily  exhaled  with  the 
breath,  a  part  doubtless  proceeds  from  the  moist  lining  of  the  nostrils,  fauces, 
&c. ;  but  it  is  indisputable  that  the  greater  proportion  of  it  comes  from  the 
lungs,  since,  when  the  respiration  is  entirely  performed  through  a  canula  intro- 
duced into  the  trachea,  the  amount  of  watery  vapour  which  the  breath  contains, 
is  still  very  considerable.     The  quantity  which  thus  passes  off  is  by  no  means 
trifling;  probably  between  16  and  20  ounces  in  the  twenty-four  hours.     It  is 
not  so  liable  to  variation  under  the  influence  of  temperature,  the  movement  of 
the  surrounding  air,  and  other  similar  causes,  as  is  the  cutaneous  transpira- 
tion ;  for  air,  which  has   found  its  way  into  the  air-cells  of  the  lungs,  is, 
under  almost  all  circumstances,  nearly  the  same  in  regard  to  such  conditions, 
and  becomes  charged  with  that  amount  of  watery  vapour  which  saturates  it  at 
the  temperature  of  the  body.    It  is  considered  by  Dr.  Prout,  that  the  principal 
source  of  this  vapour  is  not  the  blood  properly  so  called,  but  the  chyle  and 
lymph  which  have  just  been  introduced  into  it  from  the  thoracic  duct;  a  loss 
of  a  portion  of  their  fluid  being  required,  to  give  them  sufficient  concentration. 
A  process  very  analogous  takes  place  in  Plants ;  for  a  very  large  proportion  of 
the  water  taken  up  in  the  crude  sap,  is  parted  with  in  the  leaves.     But  it  is 
probable  that  a  part,  at  least,  of  the  water  thrown  off  by  the  lungs  is  generated 
by  the  union  of  Oxygen  and  Hydrogen  during  the  course  of  the  Circulation. 

774.  The  fluid  thrown  off  from  the  Lungs  is  not  pure  water.     It  holds  in 
solution,  as  might  have  been  expected,  a  considerable  amount  of  carbonic  acid, 
and  also  some  animal  matter;  the  exact  nature  of  the  latter,  which,  according 
to  Collard  de  Martigny,  constitutes  about  3  parts  in  1000,  has  not  been  ascer- 
tained.    If  the  fluid  be  kept  in  a  closed  vessel,  and  be  exposed  to  an  elevated 
temperature,  a  very  evident  putrid  odour  is  exhaled  by  it.    Every  one  knows 
that  the  breath  itself  has,  occasionally  in  some  persons,  and  constantly  in 
others,  a  fetid  taint;  when  this  does  not  proceed  from  carious  teeth,  ulcerations 
in  the  air-passages,  disease  in  the  lungs,  or  other  similar  causes,  it  must  result 
from  the  excretion  of  the  odorous  matter,  in  combination  with  watery  vapour, 
from  the  pulmonary  surface.    That  this  is  the  true  account  of  it  seems  evident, 
from  the  analogous  phenomenon  of  the  excretion  of  turpentine,  camphor,  alco- 
hol, and  other  odorous  substances,  which  have  been  introduced  into  the  venous 
system,  either  by  natural  absorption,  or  by  direct  injection;  and  also  from  the 
suddenness  with  which  it  manifests  itself,  when  the  digestive  apparatus  is 
slightly  disordered. 

50 


590  OF  RESPIRATION. 

775.  The  Lungs  are  capable,  under  peculiar  circumstances,  of  absorbing 
fluid  from  the  atmosphere.     Thus  Dr.  Madden*  has  shown  that,  if  the  vapour 
of  hot  water  be  inhaled  for  some  time  together,  the  loss  by  exhalation  is  found 
to  be  so  much  less  than  usual,  as  to  indicate  that  the  cutaneous  transpiration 
is  partly  counterbalanced  by  pulmonary  absorption;  the  pulmonary  exhalation 
being  at  the  same  time  entirely  checked.     It  is  probable  that,  if  the  quantity 
of  fluid  in  the  blood  had  been  previously  diminished  by  excessive  sweating, 
or  by  other  copious  fluid  secretions,  the  pulmonary  absorption  would  have 
been  much  greater.     Still  in  the  cases  formerly  mentioned  (§  678),  in  which 
a  large  increase  in  weight  could  only  be  accounted  for  on  the  supposition  of 
absorption  of  water  from  the  atmosphere,  it  seems  probable  that  the  cutaneous 
surface  was  chiefly  concerned :  for  it  can  only  be  when  the  air  introduced  into 
the  lungs  is  saturated  with  watery  vapour,  that  the  usual  exhalation  will  be 
checked,  or  that  any  absorption  can  take  place. 

776.  That  absorption  of  other  volatile  matters  diffused  through  the  air  is, 
however,  continually  taking  place  by  the  lungs,  is  easily  demonstrated.     A 
familiar  example,  is  the  effect  of  the  inhalation  of  the  vapour  of  Turpentine 
upon  the  urinary  excretion.     It  can  only  be  in  this  manner  that  those  gases 
act  upon  the  system,  which  have  a  noxious  or  poisonous  effect,  when  min- 
gled in  small  quantities  in  the  atmosphere.     Of  these,  Sulphuretted  Hydrogen 
is  one  of  the  most  powerful  in  its  action  ;  for  it  has  been  found  that  air  im- 
pregnated with  l-1500th  part  of  it,  will  kill  a  bird  in  a  very  short  time  ;  and 
that  a  quantity  but  little  more  than  double,  namely  l-800th  part,  will  soon  kill 
a  dog.     This  gas  is  exhaled  in  large  quantities  from  many  forms  of  decom- 
posing animal  and  vegetable  matter;  and  it  has  recently  been  shown  (by  Pro- 
fessor Daniell)  to  be  absorbed  by  the  water  of  the  estuaries  of  those  African 
rivers,  whose  mouths  are  regarded  as  among  the  most  pestilential  spots  upon 
the  surface  of  the  globe.— Carburetted  hydrogen  is  another  gas  whose  effects 
are  similar  ;  but  a  larger   proportion  is  required  to  destroy  life. — Carbonic 
acid  gas,  also,  appears  to  be  absorbed  by  the  lungs,  when  a  large  proportion 
of  it  is  contained  in  the  atmosphere.     The  accumulation  of  this  gas  in  the 
blood,  when  the  respired  air  is  charged  with  it  even  to  a  moderate  amount, 
might  be  attributed  to  the  impediments  thus  offered  to  its  ordinary  exhalation : 
but  the  following  experiment  appears  to  prove,  that  it  may  be  actually  absorbed 
into  the  blood ;  and  that  it  will  thus  exert  a  real  poisonous  influence,  and  not 
merely  produce  an  asphyxiating  effect.     It  was  found  by  Rolando,  that  the 
air-tube  of  one  lung  of  the   land-tortoise  may  be  tied,   without  apparently 
doing  any  material  injury  to  the  animal,  as  the  respiration  performed  by  the 
other  is  sufficient  to  maintain  life  for  some  time  ;  but,  having  contrived  to  make 
a  tortoise  inhale  carbonic  acid  by  one  lung,  whilst  it  breathed  air  by  the  other, 
he  found  that  the  animal  died  in   a  few  hours.t — Cyanogen  is  another  gas 
which  has  an  actively-poisonous  influence  upon  animals,  when  absorbed  into 
the  lungs ;  its  agency,  also,  is  of  a  narcotic  character. 

777.  It  is  singular  that  the  effects  of  the  respiration  of  pure  Oxygen  should 
not  be  dissimilar.     At  first,  the  rapidity  of  the  pulse  and  the  number  of  the 
respirations  are  increased,  and  the  animal  appears  to  suffer  little  or  no  incon- 
venience for  an  hour;  but  symptoms  of  coma  then  gradually  develop  them- 
selves, and  death  ensues  in  six,  ten,  or  twelve   hours.     If  the  animals   are 

*  Prize  Essay  on  Cutaneous  Absorption,  p.  55. 

j-  The  fatal  result  of  breathing  the  fumes  of  charcoal  is,  therefore,  riot  simple  asphyxia, 
such  as  would  result  from  breathing  hydrogen  or  nitrogen.  Other  volatile  products  are  set 
free  in  the  combustion  of  charcoal,  besides  carbonic  acid.  Mr.  Coathupe  (loc.  cit.)  states 
these  to  be  Carbonate,  Muriate  and  Sulphate  of  Ammonia,  Carbonic  Oxide,  Oxygen,  Nitro- 
gen, Watery  vapour,  and  Einpyreumatic  Oil :  to  these  Sulphurous  acid  may  appear  to  be 
properly  added. 


EFFECTS  OF  SUSPENSION  OF  RESPIRATION.  591 

removed  into  the  air  before  the  insensibility  is  considerable,  they  then  quickly 
recover.  When  the  body  is  examined,  the  heart  is  seen  beating  strongly 
while  the  diaphragm  is  motionless ;  the  whole  blood  in  the  veins,  as  well  as 
in  the  arteries,  is  of  a  bright  scarlet  colour;  and  several  of  the  membranous 
surfaces  have  the  same  tint.  The  blood  is  observed  to  coagulate  with  re- 
markable rapidity ;  and  it  is  to  the  alteration  in  its  properties,  occasioned  by 
the  hyper-arterialization,  and  indicated  by  this  condition,  that  we  are  proba- 
bly to  attribute  the  fatal  result.  There  can  be  no  doubt  that  in  this  instance 
an  undue  amount  of  oxygen  is  absorbed  ;  and  it  does  not  seem  unlikely  that 
one  cause  of  the  fatal  result,  is  a  stagnation  of  the  blood  in  the  systemic  capil- 
laries, consequent  upon  the  want  of  sufficient  change  in  its  condition. — When 
Nitrogen  or  Hydrogen  is  breathed,  for  any  length  of  time,  death  results  from 
the  deprivation  of  Oxygen,  rather  than  from  any  deleterious  influence  which 
these  gases  themselves  exert. — Death  is  also  caused  by  the  inhalation  of 
several  gases  of  an  irritant  character,  such  as  Sulphurous,  Nitrous,  and  Muria- 
tic acids  :  but  it  is  doubtful  how  far  they  are  absorbed ;  or  how  far  their 
injurious  effects  are  due  to  the  abnormal  action,  which  they  excite  in  the 
lining  membrane  of  the  air-cells  and  tubes. — It  cannot  be  doubted,  that  mias- 
mata and  other  morbific  agents  diffused  through  the  atmosphere,  are  more 
readily  introduced  into  the  system  through  the  pulmonary  surface  than  by 
any  other ;  and  our  aim  should  therefore  be  directed  to  the  discovery  of  some 
counteracting  agents,  which  can  be  introduced  in  the  same  manner.  The 
pulmonary  surface  affords  a  channel  for  the  introduction  of  certain  medicines 
that  can  be  raised  in  vapour,  when  it  is  desired  to  affect  the  system  with  them 
speedily  and  powerfully  ;  such  are  iodine,  mercury,  tobacco,  stramonium,  &c. 

4. — Effects  of  Suspension  of  Respiration. 

778.  We  have  now  to  consider  the  results  of  the  cessation  of  the  Respira- 
tory function,  and  the  consequent  retention  of  carbonic  acid  in  the  blood.  If 
this  be  sufficiently  prolonged,  a  condition  ensues,  to  which  the  name  of 
Asphyxia  has  been  given ;  the  essential  character  of  which  is  the  cessation 
of  muscular  movement,  and  shortly  afterwards  of  the  circulation  ;  with  an 
accumulation  of  blood  in  the  venous  system.  The  time  which  is  necessary 
for  life  to  be  destroyed  by  asphyxia  varies  much,  not  only  in  different  animals, 
but  in  different  states  of  the  same.  Thus  Warm-blooded  animals  are  much 
sooner  asphyxiated  than  Reptiles  or  Invertebrata;  on  the  other  hand,  a  hyber- 
nating  Mammal  supports  life  for  many  months,  with  a  respiration  sufficiently 
low  to  produce  speedy  asphyxia  if  it  were  in  a  state  of  activity.  And  among 
Mammalia  and  Birds,  there  are  many  species  which  are  adapted,  by  peculiari- 
ties of  conformation,  to  sustain  a  deprivation  of  air  for  much  more  than  the 
average  period.*  Excluding  these,  it  may  be  stated  as  a  general  fact,  that,  if 
a  warm-blooded  animal  in  a  state  of  activity  be  deprived  of  respiratory  power, 
its  muscular  movements  (with  the  exception  of  the  contraction  of  the  heart) 
will  cease  within  five  minutes,  often  within  three  ;  and  that  the  circulation 
generally  fails  within  ten  minutes.  Many  persons,  however,  are  capable  of 
sustaining  a  deprivation  of  air  for  three,  four,  or  even  five  minutes,  without 
insensibility  or  any  other  injury ;  but  this  power,  which  seems  possessed  to 

*  Thus,  the  Cetacea  contain  far  more  blood  in  their  vessels,  than  do  any  other  Mamma- 
lia ;  and  these  vessels  are  so  arranged  that  both  arteries  and  veins  are  in  connection  with 
large  reservoirs  or  diverticula.  The  reservoirs  belonging  to  the  former  are  usually  full ;  but 
when  the  Whale  remains  long  under  water,  the  blood  which  they  contain  is  gradually  in- 
troduced into  the  circulation,  and,  after  becoming  venous,  accumulates  in  the  reservoirs  con- 
nected with  the  venous  system.  By  means  of  this  provision,  the  Whale  can  remain  under 
water  for  more  than  an  hour. 


592  OF  RESPIRATION. 

the  greatest  degree  by  the  divers  of  Ceylon,  can  only  be  acquired  by  habit. 
The  period  during  which  remedial  means  may  be  successful  in  restoring  the 
activity  of  the  vital  and  animal  functions,  is  not,  however,  restricted  to  this. 
Cases  are  not  unfrequent,  of  the  revival  of  drowned  persons  after  a  submer- 
sion of  half  an  hour;  and  more  than  one  has  been  credibly  recorded,  in  which 
above  three-quarters  of  an  hour  had  elapsed.  It  is  not  improbable,  however, 
that  in  some  of  these  cases  a  state  of  Syncope  had  come  on  at  the  moment 
of  immersion,  through  the  influence  of  fear  or  other  mental  emotion,  concus- 
sion of  the  brain,  <fcc. ;  so  that,  when  the  circulation  was  thus  enfeebled,  the 
deprivation  of  air  would  not  have  the  same  injurious  effect,  as  when  this 
function  was  in  full  activity.  The  case  would  then  closely  resemble  that  of 
a  hybernating  animal ;  for  in  both  instances  the  being  might  be  said  to  live 
very  slowly,  and  would  therefore  not  require  the  usual  amount  of  vital  stimuli. 
The  condition  of  the  still-born  infant  is  in  some  respects  the  same ;  and  re- 
animation  has  been  successfully  attempted,  when  nearly  half  an  hour  had 
intervened  between  birth  and  the  employment  of  resuscitating  means,  and  when 
probably  a  much  longer  time  had  elapsed  from  the  period  of  the  suspension 
of  the  circulation. 

779.  It  has  now  been  sufficiently  proved,  both  by  experiment  and  by  pa- 
thological observation,  that  the  first  effect  of  the  non-arterialization  of  the 
blood  in  the  lungs,  is  the  retardation  of  the  fluid  in  their  capillaries  (§  738) ; 
of  which  the  accumulation  in  the  venous  system,  and  the  deficient  supply  to 
the  arterial,  are  the  necessary  consequences.     It  is  some  time,  however,  be- 
fore a  complete  stagnation  takes  place  from  this  cause :  since,  as  long  as  the 
proportion  of  oxygen  which  remains  in  the  air  in  the  lungs  is  considerable, 
and  that  of  the  carbonic  acid  is  small,  so  long  will  some  imperfectly-arte- 
rialized  blood  find  its  way  back  to  the  heart,  and  be  transmitted  to  the  system. 
This  blood  will  have  a  depressing  influence  upon  the  functions  of  the  brain 
and  of  the  muscular  system ;  which  influence  is  aided  by  the  diminution  that 
gradually  takes  place,  in  the  quantity  of  blood  propelled  through  the  aorta  ; 
and  the   actions  of  the  respiratory  muscles  and   of  the  heart  will  therefore 
soon  become  enfeebled.     The  cessation  of  the  heart's  contraction  is  due  to 
two  distinct  causes,  acting  on  the  two  sides  ;  for  on  the  right  side  it  is  the 
result  of  the  over-distension  of  the  walls  of  the  ventricle,  owing  to  the  accu- 
mulation of  venous  blood ;  and  on  the  left  to  deficiency  of  the  stimulus  ne- 
cessary to  excite  the  movement.     The  property  of  contractility  is  not  finally 
lost,  nearly  as  soon  as  the  movements  cease;  for  the  action  of  the  right  ven- 
tricle may  be  renewed,  for  some  time  after  it  has  ceased,  by  withdrawing  a 
portion  of  its  contents, — either  through  the  pulmonary  artery,  their  natural 
channel, — or,  more  directly,  by  an  opening  made  in  its  own  parietes,  in  the 
auricle,  or  in  the  jugular  vein  (  §  723,  c).    On  the  other  hand,  the  left  ventricle 
may  be  again  set  in  action,  by  renewing  its  appropriate  stimulus  of  arterial 
blood.     Hence,  if  the  stoppage  of  the  circulation  have  not  been  of  too  long 
continuance,  it  may  be  renewed  by  artifical  respiration  ;  for  the  replacement 
of  the  carbonic  acid  by  oxygen  in  the  air-cells  of  the  lungs,  restores  the  cir- 
culation through  the  pulmonary  capillaries  ;  and  thus  at  the  same  time  relieves 
the  distension  of  the  right  ventricle  and  conveys  to  the  left  the  due  stimulus  to 
its  actions. 

780.  Of  the  mode  in  which  the  pulmonary  circulation  is  stagnated  by  the 
want  of  oxygen,  and  renewed  by  its  ingress  into  the  lungs,  no  other  explana- 
tion can  be  given,  than  that  which  has  been  heretofore  offered  of  the  capillary 
circulation  in  general; — namely,  that  the  performance  of  the  normal  reaction 
between  the  blood  and  the  surrounding  medium  (whether  this  be  air,  water, 
or  solid  organized  tissue)  is  a  condition  necessary  to  the  regular  movement 


GENERAL  VIEW  OF  THE  PROCESS  OF  NUTRITION. 


593 


of  the  blood  through  the  extreme  vessels.*  This  view  has  recently  obtained 
additional  support  from  the  experiments  of  Dr.  J.  Reid  on  the  Respiration  of 
Azote.t  He  found  that,  when  the  ordinary  respiration  of  an  animal  is  inter- 
rupted, and  the  Asphyxia  is  proceeding  to  the  stage  of  insensibility,  the  first 
effect  upon  the  arterial  system  is  an  increased  distension  (as  indicated  by  the 
hffimadynamometer),  even  although  the  blood  is  at  that  time  nearly  venous  in 
its  character  ;  this  indicates  that  the  fluid,  now  so  perverted,  is  unable  to  pass 
with  facility  through  the  systemic  capillaries,  in  consequence  of  its  not  being 
in  a  state  fit  for  the  performance  of  its  normal  actions.  As  the  stagnation  in 
the  pulmonary  capillaries  becomes  more  complete,  however,  less  and  less 
blood  is  returned  from  the  lungs  to  the  heart;  and,  the  systemic  arteries 
being  gradually  unloaded  without  being  refilled,  the  pressure  of  the  blood 
upon  their  walls  diminishes,  and  is  at  last  no  longer  experienced.  Its  dimi- 
nution is  not  arrested  by  causing  the  animal  to  breathe  nitrogen,  although  the 
respiratory  movements  are  renewed, — thus  proving  that  the  stagnation  of  the 
blood  in  the  capillaries  of  the  lungs  is  not  due  (as  some  have  supposed)  to  a 
mechanical  impediment:  but  the  pressure  is  immediately  increased  by  the 
admission  of  atmospheric  air,  which  occasions  the  renewal  of  the  pulmonary 
circulation,  and  the  consequent  increase  in  the  supply  of  aerated  blood  to  the 
systemic  arteries. — It  has  been  shown  by  Mr.  Wharton  Jones,:}:  that  the  ca- 
pillary circulation  in  a  frog's  foot  is  retarded  or  even  checked,  by  the  direc- 
tion of  a  stream  of  carbonic  acid  gas  against  the  membrane ;  and  he  attributes 
this  stagnation  to  the  disposition  thus  produced  in  the  red  corpuscles,  to  ag- 
gregate together  and  to  adhere  to  the  walls  of  the  vessel,  so  as  to  choke  up 
its  calibre. 


CHAPTER    XIV. 


OF    NUTRITION. 


1. — General  Considerations. — Selective  Power  of  Individual  Parts. 

781.  THE  function  of  Nutrition,  considered  in  the  widest  acceptation  of  the 
term,  includes  the  whole  series  of  processes,  by  which  the  fluid  alimentary 
materials, — prepared  by  the  Digestive  process,  introduced  into  the  system  by 
Absorption,  and  carried  into  its  penetralia  by  the  Circulation, — are  converted 
into  Organized  tissue;  by  which  conversion  it  is  caused  to  manifest  a  set  of 
properties  altogether  new,  which,  being  neither  Physical  nor  Chemical,  are 
termed  Vital.  Thus  Albumen,  which  is  a  perfectly  dead  or  inert  substance, 
and  of  which  the  distinguishing  properties  are  entirely  attributable  to  its  pecu- 
liar composition,  is  transformed  by  the  Nutritive  process  into  Muscular  Fibre, 
possessed  of  the  remarkable  Vital  property  of  Contractility. — But  this  process 
of  conversion  commences  in  the  nutritive  materials  whilst  they  are  still  in  a 
fluid  condition,  and  are  moving  through  the  vessels ;  for  we  have  seen  that,  at 
this  stage  of  the  operation,  the  unorganizable  Albumen  is  transformed  into 

*  For  a  fuller  discussion  of  the  Pathology  of  Asphyxia,  see  the  Author's  essay  on  the  sub- 
ject in  the  Library  of  Practical  Medicine,  vol.  iii. 
f  Edinb.  Med.  and  Surg.  Journal,  April  1841* 
j  British  and  Foreign  Medical  Review,  vol.  xiv.,  p.  600, 

50* 


594  OF  NUTRITION. 

Fibrine, — a  substance  which  possesses  a  tendency  to  spontaneous  organization, 
and  which  must  be  regarded  as  endowed  with  Vital  properties.  It  is  convenient 
to  speak  of  it,  therefore,  under  a  distinct  designation ;  and  the  term  Assimilation 
has  been  applied  to  it.  In  its  more  restricted  sense,  the  term  Nutrition  is 
applied  to  the  growth  of  the  various  tissues  of  the  body,  at  the  expense  of  the 
materials  prepared  by  the  Assimilating  process,  and  supplied  by  the  Circu- 
lating current. 

782.  It  appears  evident,  from  what  has  been  formerly  stated  (Chap,  in.), 
that  the  process  of  Nutrition  mainly  consists  in  the  growth  of  the  individual 
cells  composing  the  fabric;  and  that  these  derive  their  support  from  the 
organic  compounds  with  which  they  are  supplied  by  the  blood,  just  as  the 
cells  composing  the  simplest  Plants  derive  theirs  from  the  inorganic  elements 
which  surround  them.  And  as  different  species  of  the  latter  select  and  com- 
bine these  in  such  modes  and  proportions  as  to  give  rise  to  organisms  of 
very  diversified  forms  and  properties,  so  is  it  easily  intelligible  that  the  dif- 
ferent parts  of  the  fabric  of  the  highest  Animals  should  exercise  a  similar 
selective  power,  in  regard  to  the  materials  with  which  the  blood  supplies 
them.  The  structure  composing  every  separate  portion  of  the  body  has 
(what  may  be  termed)  an  elective  affinity  for  some  particular  constituents  of 
the  blood ;.  causing  it  to  abstract  from  that  fluid,  and  to  convert  into  its  own 
substance,  certain  of  its  elements.  The  property  by  which  the  cells  of  the 
Animal  or  Vegetable  structure  are  enabled  to  perform  it,  is  one  of  which  we 
are  not  likely  soon  to  know  more.  It  will  probably  long  remain  an  ultimate 
fact  in  Physiology,  that  cells  have  the  power  of  growing  from  germs,  of  under- 
going certain  transformations,  and  of  producing  germs  that  will  develope  other 
cells  similar  to  themselves ; — just  as  it  is  an  ultimate  fact  in  Physics,  that 
masses  of  matter  attract  each  other ;  or  in  Chemistry,  that  the  molecules  of 
different  substances  have  a  tendency  to  unite,  so  as  to  form  a  compound  dif- 
ferent from  either  of  the  elements.  It  is  of  such  ultimate  facts  as  these,  that 
the  science  of  Vitality  essentially  consists :  since  the  Physical  and  Chemical 
phenomena  which  occur  in  living  bodies,  are  not  strictly  removable  from  the 
laws  of  Inorganic  Nature.  The  conditions  under  which  this  appropriating 
power  operates,  however,  are  freely  open  to  our  investigation ;  and  it  is  a 
great  step  in  the  progress  of  the  inquiry,  to  become  aware  that  these  are  so 
closely  conformable,  throughout  the  organized  world,  as  they  have  been 
shown  to  be.  It  may  be  stated,  as  a  general  fact,  that  in  assimilating,  or  con- 
verting into  its  own  substance,  matter  which  was  previously  unable  to  exhibit 
any  of  the  manifestations  of  life,  every  cell  thereby  participates  in  the  process 
of  organization  and  vitalization;  for,  by  the  new  circumstances  in  which  the 
matter  is  placed,  its  properties  undergo  a  change,— or,  to  speak  more  correctly, 
properties  which  were  previously  dormant  are  caused  to  manifest  themselves. 
No  matter,  that  is  not  in  a  state  of  Organization,  can  exhibit  those  properties, 
which,  from  their  being  peculiar  to  living  bodies,  and  altogether  different  from 
Physical  and  Chemical,  are  termed  Vital;  and  it  may  also  be  asserted  that 
no  matter,  which  exhibits  perfect  organization,  is  destitute  of  the  peculiar 
vital  properties  belonging  to  its  kind  of  structure.*  As  a  corollary  to  this 
general  fact,  it  may  be  stated,  that  no  organism  can  be  produced  by  any 
fortuitous  combination  of  inorganic  matter;  since,  even  for  the  generation  of 
the  simplest  cell,  there  is  required  a  cell  previously  existing,  to  furnish  the 
germ. 

*  For  a  fuller  consideration  of  this  question,  and  the  grounds  upon  which  this  view  is 
supported,  the  reader  is  referred  to  the  Article  Life  in  the  Cyclopedia  of  Anatomy  and  Phy- 
siology; and  to  the  Chapter  on  the  "Nature  and  Causes  of  Vital  Actions,"  in  his  Principles  of 
General  and  Comparative  Physiology. 


SELECTIVE  POWER  OF  INDIVIDUAL  PARTS.  595 

783.  We  have  seen  that,  in  some  cases,  the  germs  are  prepared  by  pre- 
viously-existing cells  of  the  same  kind;  thus  the  Red  and  colourless  corpuscles 
of  the  Blood,  the  Cartilage-cells,  the  cells  of  Vesicular  Nervous  matter,  and 
those  of  many  other  tissues,  appear  to  be  the   offspring  of  parents  exactly 
similar  to  themselves.     In   other  cases,  however,  the  germs  seem  to  be  fur- 
nished by  certain  "  nutritive  centres,"  which  appear  to  be  constantly  engaged 
in  the  preparation  of  them,  deriving  their  materials  from  the  blood".*     Thus 
the  Epidermic  and  Epithelial  cells  are  produced,  not  from  preceding  cells  of 
a  similar  character  (for  these  are  thrown  off  without  performing  any  such 
reproductive  act),  but  from  germs  derived  from  the  basement  or  primary  mem- 
brane beneath;  and,  in  like  manner,  the  minute  cells,  of  which  the  ultimate 
Jibrillse  of  Muscle  are  composed,  appear  to  originate  in  nuclei  or  germinal 
centres,  belonging  to  the  tubular  Myolemma.     But  even  these  germinal  centres 
may  probably  be  considered  as  nothing  else  than  the  nuclei  of  certain  parent- 
cells,  which,  instead  of  producing  their  like,  give  origin  to  a  new  generation 
having  different  properties.     Thus,  the  basement  or  primary-membrane  has 
been   already  stated  (§  135)  to  exhibit  not  unfrequently  the  indications  of  a 
cellular  constitution ;  the  germinal  centres  which  it  contains  being  the  nuclei 
of  its  component  cells :  and  its  character  is  particularly  well  seen  where  it  is 
inverted  so  as  to  form  secreting  follicles ;  for,  as  we  have  seen  (§  174),  each 
of  these  follicles  may  be  regarded  as  a  single  parent-cell,  which  opens  at  the 
extremity  farthest  from  the  nucleus,  and  continues  to  discharge  from  its  orifice 
successive  generations  of  cells,  having  their  origin  in  its  nucleus,  which  thus 
acts  as  a  permanent  "  germinal  centre."     And  in  like  manner,  the  germinal 
centres  of  Muscular  Fibre  may  be  regarded  as  the  nuclei  of  the  cells,  of  which 
it  was  originally  composed. 

784.  The  Selecting  power,  which  is  possessed  by  the  germs  of  each  kind 
of  tissue,  and  which  enables  them  to  draw  from  the  Blood  the  materials  which 
they  severally  require  for  their  development,  manifests  itself  also  in  the  mode 
in  which  substances,  that  are  abnormally  present  in  the  Blood,  affect  the  con- 
dition and  development  of  the  solid  tissues.     Thus  we  find  that  the  presence 
of  a  certain  quantity  of  Arsenic  in  the  Blood,  will  produce  a  state  of  irritation 
of  all  the  Mucous  membranes  in  the  body.     The  continued  introduction  of 
Lead  into  the  circulating  system,  occasions  a  modification  in  the  nutrition  of 
the  extensor  muscles  of  the  forearm,  producing  the  form  of  partial  paralysis 
commonly  termed  wrist-drop;  and  the  existence  of  this  modification  is  shown 
by  the  fact  (disclosed  by  Chemical  analysis)  of  the  actual  presence  of  lead  in 
the  palsied  muscles. — Here  we  have  to  remark  the  Symmetrical  nature  of  the 
affection,  consequent  upon  the  occurrence  of  the  same  disorder  in  the  corre- 
sponding parts  of  the  two  sides  of  the  body ;  for  these  muscles  appear  to  have 
the  same  kind  of  tendency  to  attract  Lead  from  the  circulating  current,  in  a 
degree  that  is  equal  on  the  two  sides,  as  they  have  to  draw  from  the  blood 
the  materials  of  their  regular  growth,  and  to  develope  themselves  in  an  exactly 
similar  manner.     In  like  manner,  the  cutaneous   eruptions,  which  are  occa- 
sionally produced  by  the  internal  exhibition  of  iodide  of  potassium,  are  found 
to  be  almost  precisely  symmetrical;  the  presence  of  the  medicine  in  the  blood 
being  the  occasion  of  a  disordered  nutrition  of  certain  parts  of  the  skin ;  and 
the  selecting  power  of  particular  spots  being  evinced  by  the  exact  correspond- 
ence of  the  parts  affected  on  the  two  sides. 

785.  The  same  appears  to  be  the  case  with  regard  to  substances,  whose 
presence  in  the  blood  is  rather  the  result  of  a  disordered  condition  of  the 
digestive  and  assimilating  processes,  than  of  their  direct  introduction  from 
without.     Thus  in  Lepra  and  Psoriasis, — chronic  diseases  of  the  Skin,  which 

*  See  Goodsir's  Anatomical  and  Pathological  Observations,  Chap.  i. 


596  OF  NUTRITION. 

seem  to  have  their  origin  in  a  disordered  state  of  the  Blood,  rather  than  in  the 
solid  tissues  affected, — we  find  a  remarkable  tendency  to  the  repetition  of  the 
patches,  on  the  two  sides  of  the  body,  or  on  the  corresponding  parts  of  the 
limbs ;  and  this  we  must  attribute,  to  the  peculiar  attraction  subsisting  between 
the  solid  tissues  of  those  parts,  and  the  morbid  matter  circulating  through 
them. — So  in  those  chronic  forms  of  Gout  and  Rheumatism,  which  modify 
the  nutrition  of  the  joints,  producing  a  deposit  of  "chalk  stones,"  or  perma- 
nent distortion  and  stiffening  from  an  alteration  of  the  tissues,  of  the  joint,  we 
almost  invariably  find  the  corresponding  joints  of  the  two  sides  affected. — 
The  chief  exceptions  to  the  general  principle,  that  the  presence  of  morbid  or 
extraneous  matters  in  the  blood  affects  all  parts  alike,  are  found  to  occur 
where  there  is  much  febrile  disturbance,  or  where  local  causes  produce  a 
peculiar  tendency  to  disorder  of  a  single  part.  The  nearer  the  approach 
presented  by  the  morbid  process,  in  point  of  rate  and  character,  to  the  ordi- 
nary nutritive  operations  of  the  part,  the  more  does  it  tend  to  approach  these, 
in  the  symmetry  with  which  it  developes  itself.* 

2. —  Varying  Activity  of  the  Nutritive  Processes. — Separative  Operations. 

786.  Without  any  change  in  the  character  of  the  Nutritive  processes,  there 
may  be  considerable  variations  in  their  degree  of  activity  ;  and  this,  either  as 
regards  the  entire  organism,  or  individual  parts,  though  most  commonly  the 
latter.     These  variations  may  be   so  considerable  as  to  constitute  Disease ; 
though  there  are  some  which  take  place  as  part  of  the  regular  series  of  Phy- 
siological phenomena.     Thus,  the  Nutritive  processes  should  have  a  degree 
of  activity  more  than  sufficient  to  supply  the  Waste  of  the  body  during  the 
whole  period  of  infancy,  childhood  and  adolescence,  until,  in  fact,  its  full 
dimensions  are  obtained ;  whilst,  on  the  other  hand,  they  are  usually  less 
rapid  than  the  disintegrating  processes  in  old  age,  so  that  the  bulk  of  the  body 
diminishes.     Now  as  the  Waste  of  the  body,  so  far  from  being  more  rapid  in 
old  age  than  in  childhood,  is  much  less  so,  it  follows  that  the  difference  in 
the  activity  of  the  Nutritive  processes  in  these  two  states  must  be  very  con- 
siderable ;  and  this  is  manifested,  not  only  in  the  greater  demand  for  food 
which  exists  in  the  child  (relatively  to  the  bulk  of  its  body),  but  also  in  the 
greater  quickness  and  facility  with  which  injuries  are  repaired.     Local  varia- 
tions may  also  occur,  as  part  of  the  regular  train  of  vital  actions  in  the  adult; 
thus  we  perceive  an  enormous  increase  in  the  amount  of  tissue  contained  in 
the  Uterus  and   Mammary  glands  during  pregnancy,  and  a  decrease  in  the 
bulk  of  the  Thymus  gland  after  the  period  of  infancy.     Now  in  these  cases 
we  see,  that  increased  Nutrition  is  invariably  connected  with  increased  Func- 
tional activity;  and  diminished  nutrition  with  diminished  functional  activity: 
and  this  we  shall  find  to  be  the  constant  rule,  in  regard  also  to  those  variations 
which  must  be  considered  as  abnormal. 

787.  Increased  Nutrition,  or  Hypertrophy,  is  never  known  to  affect  the 
whole  body,  to  a  degree  sufficient  to  constitute  disease.     It  cannot  be  pro- 
duced as  a  consequence  of  the  ingestion  of  an  undue  supply  of  food  :  for  this 
does  not  increase  the  formative  activity  of  the  tissues,  but  merely  renders  the 
blood  richer  in  nutritive  materials;  a  part  of  which  the  excreting  organs  are 
called  on  to  be  continually  removing,  without  its  being  rendered  subservient  to 
the  wants  of  the  body  (§  819);  whilst  another  part  may  be  employed  in  the 
nutrition  of  one  particular  tissue,  the  Adipose,  which  has  a  tendency  to  in- 
crease with  the  superfluity  of  non-azotized  food,  provided  that  the  requi- 

*  See  Dr.  W.  Budd's  valuable  paper  on  the  "  Symmetry  of  Disease,"  in  vol.  xxv.  of  the 
Medico-Chirurgical  Transactions. 


VARYING  ACTIVITY  OF  THE  NUTRITIVE  PROCESSES.  597 

site  amount  of  cellular  tissue  be  generated  to  hold  the  fatty  matter  (§  184). 
But  examples  of  Hypertrophy  of  particular  tissues  or  organs  are  very  com- 
mon. Thus  any  particular  set  of  Muscles,  which  is  subjected  to  frequent  and 
energetic  use,  acquires  a  great  increase  in  bulk  ;  as  we  see  in  the  arms  of  a 
Blacksmith  or  Waterman,  the  legs  of  an  Opera-dancer,  &c.  The  hypertrophy 
of  these  muscles  is  a  consequence  of  their  increased  functional  activity  ;  which, 
being  produced  by  an  exertion  of  the  will,  and  unaccompanied  with  any  in- 
jurious effects  on  the  system,  can  scarcely  be  regarded  as  morbid.  But  there 
are  many  instances,  in  which  the  involuntary  muscles  acquire  a  greatly- 
increased  strength,  in  consequence  of  an  obstruction  to  their  action,  which 
results  from  disease.  Thus  we  see  the  right  ventricle  of  the  Heart  become 
hypertrophied  (and  dilated  at  the  same  time),  where  chronic  pulmonary  dis- 
ease produces  a  difficulty  in  the  propulsion  of  the  blood  through  the  vessels 
of  the  lungs ;  the  muscular  fibres  of  the  Bladder  become  enormously  hyper- 
trophied, when  stricture,  diseased  prostate,  or  other  causes  produce  a  demand 
for  increased  expulsive  force  on  the  part  of  that  organ  ;  and  those  of  the 
Stomach  also  become  so,  in  cases  of  stricture  of  the  pylorus.  As  an  instance 
of  hypertrophy  of  a  Secreting  organ  in  consequence  of  an  undue  excitement 
of  its  function,  we  may  notice  the  enlargement  which  usually  takes  place  in 
the  Kidney,  when  its  fellow  is  incapacitated  by  disease.  And  the  Nervous 
system  presents  us  with  a  very  remarkable  case  of  hypertrophy  of  a  part, 
resulting  from  over-excitement  of  its  function;  for  if  young  persons,  who 
naturally  show  precocity  of  intellect,  are  encouraged  rather  than  checked  in 
the  use  of  their  brain,  the  increased  nutrition  of  the  organ  (which  grows  faster 
than  its  bony  case)  occasions  pressure  upon  its  vessels,  it  becomes  indurated 
and  inactive,  and  fatuity  and  coma  are  the  result. 

788.  Local  hypertrophy  may  be  induced  also  by  local  congestions ;  but  in 
such  cases  it  will  usually  be  found,  that  the  form  of  tissue  produced  is  of  the 
lowest  kind,  unless  the  functional  activity  of  the   part  be  increased  by  the 
congestion.     Thus,  when  disease  of  the  Heart  produces  long-continued  con- 
gestion of  the  Lungs,  Liver,  Spleen,  &c.,  the  bulk  of  these  organs  increases ; 
but  chiefly  by  the  production  of  an  additional  amount  of  interstitial  Areolar 
tissue,  which  may  result  (as  we  have  seen)  from  the  simple  consolidation  of 
Fibrine ;  and  partly  also  (in  the  case  of  the  spleen  especially)  by  the  gorging 
of  their  distensible  veins  with  blood. — One  of  the  least  explicable  cases  of 
Hypertrophy,  is  that  which  takes  place  in  the  Thyroid  gland,  causing  Bron- 
chocele.     So  little  is  known  of  the  normal  office  of  this  organ,  that  it  cannot 
be  determined,  whether  its  increased  size  be  due  to  an  increased  activity  of 
its  functional  operations,  or  to  an  unusual   formative  activity  in    its  tissue, 
depending  on  some  hidden    cause.     The  connection  of  this  disorder  with 
causes  which  affect  the  whole  constitution  rather  than  individual  parts,  would 
seem  to  indicate  the  former. 

789.  When  the  Waste  of  the  Tissues  is  more  rapid  than  their  replacement 
by  Nutrition,  Atrophy  is  said  to  take  place ;  and  this  may  affect  either  the 
whole  body,  or  individual  parts.     General  Atrophy,  Marasmus,  or  emaciation, 
may  result  from  an  insufficient  supply  of  plastic  matter,  from  want  of  forma- 
tive power  in  the  tissues  themselves,  or  from  their  too  rapid  disintegration. 
The  insufficiency  of  the  supply  of  nutritive  matter  may  depend  either  on  de- 
ficiency in  the  azotized  substances  ingested  as  food,  or  on  imperfect  perform- 
ance of  those  processes  by  which  they  are  converted  into  the  plastic  ele- 
ment,— Fibrine.      Hence,  even  when  there  is    an   ample    supply  of  food, 
atrophy  may  take  place  to  a  very  severe  extent,  in  consequence  of  disordered 
digestion,  or  a  want  of  vital  power  in  the  fibrine-elaborating  cells.     Again,  we 
have  reason  to  believe  that  the  formative  power  in  the  tissues  themselves  may 
be  diminished,  so  as  to  check  the  process  of  Nutrition,  even  when  the  plastic 


598  OF  NUTRITION. 

material  is  supplied  ;  thus  there  seems  to  be  a  complete  stoppage  of  this  action 
in  Fever,  and  a  diminution  of  it  in  that  irritable  state  of  the  system,  which 
results  from  excessive  and  prolonged  bodily  exertion  or  anxiety  of  mind,  es- 
pecially when  accompanied  by  want  of  sleep.  It  is  difficult  to  separate  this 
cause,  however,  from  mal-assimilation  on  the  one  hand,  or  from  too  rapid 
decay  of  the  tissues  on  the  other :  for  we  know  that,  in  such  states,  there  is  a 
tendency  to  imperfect  elaboration  of  the  Fibrinous  element,  and  at  the  same 
time  an  unusually  rapid  disintegration,  as  manifested  by  the  increased  amount 
of  Urea  in  the  urine.  The  influence  of  excessive  waste  in  causing  Atrophy 
of  the  body,  is  well  shown  in  the  cases  of  Diabetes  mellitus  and  colliquative 
Diarrhoea ;  in  both  these,  the  increase  and  depravation  of  the  secretions  are 
undoubtedly  to  be  regarded  as  the  effects,  and  not  the  causes,  of  the  textural 
changes  with  which  they  are  associated.  Colliquative  Diarrhoea  is  a  constant 
occurrence  on  the  last  day  or  two  of  life,  in  animals  reduced  by  Starvation  ; 
and  is  accompanied  by  that  foetid  odour  of  the  body,  which  indicates  that 
decomposition  is  already  going  on  throughout  the  system.  The  same  thing 
occurs  as  the  ordinary  termination  to  many  diseases  of  exhaustion ;  in  which 
Inanition  is  unquestionably  the  immediate  cause  of  death. 

790.  Partial  Atrophy  may   occur  in  consequence  of  disuse  of  the  organ 
affected,  occasioning  inactivity  in  its  formative  processes ;  or  as  a  result  of  a 
deficiency  of  nutriment,  occasioned  by  an  obstruction  to  the  circulation.     Of 
the  operation  of  the  former  cause,  we  have  many  examples  in  the  ordinary 
processes  of  the  economy.     Thus   the  Uterus  is   atrophied,  relatively  to  its 
previous  condition,  as  soon  as  parturition  has  taken  place  ;  and  the  Mammary 
glands,  when  lactation  has  been  discontinued.     It  is  probably  in   part  to  this 
cause,  and  in  part  to  the  diversion  of  the  blood  into  other  channels,  that  we 
are  to  attribute  the  atrophy  of  many  parts,  as  the  development  of  the  system 
advances,  which  at  an  earlier  period  were  of  large  comparative  size, — such  as 
the   Corpora  Wolffiana,   the   Suprarenal  capsules,  and  the   Thymus   gland. 
Many  instances  might  be  adverted  to,  of  the  influence  of  suspension  of  func- 
tional activity,  as  a  result  of  disease  or  injury,  in  producing  local  atrophy. 
One  of  the  most  common  cases,  is  the  atrophy  of  Muscles  which  is  conse- 
quent upon  their  disuse.     This  disuse  will  produce  the  same  effect,  whether 
it  be  occasioned  by  paralysis,  which  prevents  the  nervous  centres  from  excit- 
ing the  muscles  to  contraction;  or  by  anchylosis,  which  interposes  a  mechani- 
cal impediment  to  their  use  ;  or  by  fractures  or  other  accidents,  the  reparation 
of  which  requires   the  limb  to  be  kept  at  rest.     Or  even  if,  without  having 
suffered  from  any  injury,  a  limb  be  fixed  during  some  time  in  one  posture,  its 
muscles  will  become  atrophied,  as  is  seen  in  the  case  of  the  Indian  Fakirs. 
(See  §  588).     Similar  facts  may  be  adduced,  in  regard  to  Atrophy  of  Nerves, 
from  interruption  of  their  normal  function.     Thus  when  the  Cornea  has  been 
rendered  so  opaque  by  accident  or  disease,  that  no  light  can  penetrate  to  the 
interior  of  the  eye,  the  Retina  and  the  Optic  nerve  lose,  after  a  time,  their 
characteristic  structure  ;  so  that  scarcely  a  trace  of  the  peculiar  globules  of  the 
former,  or  of  the  nerve-tubes  of  the  latter,  can  be  found  in  them.     These  and 
similar  facts  are  readily  understood,  when  connected  by  the  general  principle 
formerly  laid  down, — that  every  proper  vital  operation  involves  an   act  of 
nutrition  ;  in  such  a  manner  that,  whilst  the  vital  properties  of  any  part  are 
dependent  upon  its  due  nutrition,  the  amount  of  its  nutrition  will  in  return 
depend  upon  the  degree  in  which  these  properties  are  exercised. 

791.  Partial  Atrophy  may  depend,  however,  upon  causes  of  a  purely  me- 
chanical nature ;  such,  for  example,  as  produce  an  interruption  of  the  current 
of  Blood  through  the  part.     This  may  result  from  changes   in   the  Arteries 
supplying  it ;  such  as  ossification,  or  other  forms  of  obstruction.     Or  it  may 
be  consequent  upon  disease  in  the  part  itself ;  as  when  the  deposits  produced 


VARYING  ACTIVITY  OF  THE  NUTRITIVE  PROCESSES.  5&9 

by  Inflammation  tend  to  contract,  and  thus  to  press  upon  the  vascular  struc- 
ture, which  frequently  happens  in  the  lungs,  liver,  and  kidneys;  or  when  the 
inflammation  occurs  in  the  vessels  themselves,  causing  adhesion  of  their  walls, 
and  obliteration  of  their  tubes ;  or  when  a  new  growth  absorbs  into  itself  all 
the  nutritive  materials  which  the  Blood  supplies.* 

792.  The  nutritive  operations  take  place,  with  extraordinary  energy  and 
rapidity,  in  the  process  of  Reparation;  by  which  losses  of  substance,  occa- 
sioned by  injury  or  disease,  are  made  good.  In  its  most  perfect  form,  this 
process  is  exactly  analogous  to  that  of  the  first  development  of  the  correspond- 
ing parts ;  and  its  results  are  as  complete  in  the  one  case  as  in  the  other.  In 
fact,  among  the  lowest  tribes  of  Animals,  we  find  these  two  conditions 
blended,  as  it  were,  together;  for  the  process  of  reparation  may  be  carried  in 
them  to  such  an  extent,  as  to  regenerate  the  whole  organism  from  a  very  small 
portion  of  it.  In  the  Hydra,  or  Fresh-water  Polype,  there  would  seem  to  be 
scarcely  any  limit  to  this  power;  for,  if  the  body  of  the  animal  be  minced 
into  the  smallest  possible  fragments,  every  one  of  these  can  produce  a  new 
and  perfect  being.  In  this  manner  no  less  than  forty  have  been  artificially 
generated  from  a  single  individual. — In  ascending  the  Animal  scale,  we  find 
this  reparative  power  less  conspicuous,  because  exercised  with  regard  to 
smaller  parts  only  of  the  body ;  but  the  greater  complexity  of  the  changes 
involved  in  the  process,  renders  it  in  reality  not  less  considerable  than  in  the 
lower  classes.  Thus,  the  restoration  of  a  Bone  destroyed  by  Necrosis  is  a 
much  more  extraordinary  operation,  than  the  growth  of  an  entire  Polype  from 
a  single  fragment:  since  it  involves  a  far  greater  amount  and  variety  of 
actions.  Numerous  and  well-authenticated  instances  are  on  record,  of  the 
reunion  of  parts  that  had  been  entirely  separated  from  the  body,  and  of  the 
restoration  of  all  their  vital  properties  :  and  this  could  only  take  place,  through 
the  perfect  reproduction  of  a  large  number  of  very  different  structures.  The 
reappearance  of  Fungous  growths,  whose  organization  is  of  a  low  character, 
is  a  fact  with  which  every  surgeon  is  familiar ;  and  cases  occasionally,  though 
rarely,  present  themselves,  in  which  reproduction  of  a  whole  member  takes 
place  even  in  the  Human  subject.t 

793.  [t  is  the  general  opinion  among  British  surgeons  (founded  upon  what 
they  believe,  but  erroneously,  to  have  been  the  doctrine  of  Hunter),  that  In- 
flammation is  essential  to  the  process  of  Reparation.     There  is  no  doubt  that, 
as  usually  conducted,  the  healing  of  wounds  is  attendee^  by  a  greater  or  less 
degree  of  Inflammation ;  but  it  does  not  thence  follow  that  this  morbid  con- 
dition is  essential  to  the  renewal  of  the  healthy  state;  and  in  fact  it  can  be 
shown  that,  in  the  majority  of  cases,  the  Inflammation  is  injurious  rather  than 
beneficial.     The  following  important  conclusions  are  drawn  by  Dr.  Macart- 
ney:}: from  a  very  philosophical  comparative  survey  of  .the  operations  of  Re- 
paration and  Inflammation,  as  performed  in  the  different  classes  of  animals  : 
— "  That  the  powers  of  Reparation  and  Reproduction  are  in  proportion  to  the 
indisposition  or  incapacity  for  Inflammation ; — that  Inflammation  is   so  far 
from  being  necessary  to  the  Reparation  of  parts,  that,  in  proportion  as  it  exists, 
the  latter  is  impeded,  retarded,  or  prevented; — that,  when  Inflammation  does 
not  exist,  the  Reparative  power  is  equal  to  the  original  tendency  to  produce 
and  maintain  organic  form  and  structure  ; — and  that  it  then  becomes  a  natural 
function,  like  the  growth  of  the  individual,  or  the  reproduction  of  the  species." 

794.  Guided  chiefly  by  Dr.  Macartney's  views,  which  have  derived  im- 

*  See  on  this  subject  Dr.  Williams'  Elements  of  Medicine,  chap.  iv. ;  to  which  the  Author 
is  partly  indebted  for  the  preceding  paragraphs. 

f  See,  on  the  whole  of  the  subject  of  the  comparative  powers  of  Reparation  in  the  Ani- 
mal series,  the  Author's  Principles  of  Gen.  and  Comp.  Physiol.  §§  586,  587. 

J  Treatise  on  Inflammation,  p.  7. 


600  OF  NUTRITION. 

portant  confirmation  from  recent  observations,  we  shall  treat  of  the  reparative 
processes  under  three  distinct  heads  : — First,  the  adhesion  of  the  sides  of  a 
wound  by  a  medium  of  coagulable  lymph,  or  of  a  clot  of  blood.  Second, 
reparation  without  any  medium  of  lymph  or  granulations,  the  cavity  of  the 
wound  being  filled  by  a  natural  process  of  growth  from  its  walls.  Third, 
reparation  by  means  of  a  new,  vascular,  and  organized  substance,  termed ' 
Granulations. — The  first  of  these  modes  of  Reparation,  is  that  which  is  ordi- 
narily termed  union  by  the  first  intention;  of  this  kind  of  adhesion,  the  heal- 
ing of  the  incision  made  in  venesection,  which  usually  takes  place  almost 
without  consciousness  on  the  part  of  the  patient,  and  with  scarcely  any  In- 
flammation, is  a  characteristic  example:  the  white  line  of  cicatrix  which  is 
left,  marks  the  formation  of  new  substance ;  and  is  the  result  of  the  want  of 
that  perfect  approximation  of  the  lips  of  the  wound,  which  may  frequently  be 
obtained  in  parts,  where  pressure  can  be  more  firmly  applied,  and  where  the 
space  to  be  filled  up  is  proportionably  thinner.  This  mode  of  union  is  ordi- 
narily considered  by  British  Surgeons  to  be  the  result  of  an  adhesive  inflam- 
mation. In  so  regarding  it,  they  conceive  that  they  are  following  out  the 
views  of  Hunter ;  but  he  expressly  states  that  wounds  may  heal  without  any 
pain  or  constitutional  disturbance,  the  reunion  proceeding  "as  if  nothing  had 
happened  ;"  so  that  he  in  effect  admits,  that  reparation  of  this  kind  may  take 
place  without  Inflammation.  It  is  well  known  that  if  a  slight  wound,  which 
is  thus  healing,  be  provoked  to  an  increased  degree  of  Inflammation,  its  pro- 
gress is  interrupted ;  and  all  the  means  which  the  Surgeon  employs  to  pro- 
mote union,  are  such  as  tend  to  prevent  the  accession  of  this  state.  The 
doctrine  that  the  effusion  of  Lymph  for  the  Reparation  of  the  tissues,  is  not 
to  be  regarded  as  necessarily  a  result  of  the  Inflammatory  process,  is  not  so 
novel  as  its  opponents  have  regarded  it;  since  it  has  been  maintained  by  many 
eminent  observers,  even  from  the  earliest  times.  The  only  case  in  which 
the  occurrence  of  Inflammation  can  be  regarded  as  salutary,  is  that  in  which 
there  is  a  deficiency  of  Fibrine  in  the  blood,  causing  a  deficient  organiza- 
bility  of  the  lymph.  It  has  been  seen  that  the  amount  of  Fibrine  is  rapidly 
increased  by  inflammation ;  and  the  Surgeon  well  knows  that  a  wound  with 
pale  flabby  edges,  in  a  depressed  state  of  the  system,  will  not  heal,  until  some 
degree  of  Inflammation  has  commenced. 

795.  When  the  Liquor  Sanguinis  of  the  Blood,  known  as  Coagulable 
Lymph,  is  effused  between  the  two  edges  of  a  wound,  or  upon  the  surface  of 
a  membrane  lining  a  closed  sac,  the  following  appears  to  be  the  history  of  its 
organization.  The  new  matter,  which  is  poured  out  in  a  fluid  state,  and 
which  seems  to  have  been  subjected  to  the  peculiar  influence  of  the  Colour- 
less Corpuscles  that  rapidly  collect  in  large  numbers  at  the  injured  spot,  un- 
dergoes a  Coagulation  resembling  that  of  Blood;  the  Serum,  being  set  free 
by  the  concretion  of  the  Fibrine,  is  absorbed;  and  the  fibrinous  coagulum 
speedily  attains  an  almost  membranous  density.  If  examined  with  a  Micro- 
scope at  the  commencement  of  the  process  of  organization,  it  is  seen  to  con- 
tain a  large  number  of  cells,  which  sometimes  closely  resemble  the  Colourless 
Corpuscles  of  the  Blood;  and  in  other  instances  (especially  where  there  has 
been  active  Inflammation)  present  greater  similarity  to  Pus-corpuscles  ;  these 
cells,  which  are  known  as  exudation-corpuscles,  probably  originate  in  granules 
set  free  from  the  Colourless  Corpuscles  of  the  circulating  blood,  and  exuded 
with  the  Liquor  Sanguinis.  In  a  short  time,  these  corpuscles  present  the 
appearance  of  regular  cells,  disposed  in  layers,  and  adhering  together^  by  an 
intermediate  unorganized  substance ;  bearing,  in  fact,  a  strong  resemblance  to 
the  cells  of  tesselated  epithelium.  Some  hours  later,  the  mass  exhibits  an 
evidently-fibrous  character  ;  which  is  probably  due  to  the  further  elaboration 
of  the  plastic  material,  by  the  cells  just  mentioned.  Between  the  fibres,  a 


REPARATIVE  PROCESSES.  601 

considerable  amount  of  unorganized  substance  yet  remains  ;  and  they  may  be 
readily  separated,  or  torn  in  any  direction.  A  vascular  rete  next  makes  its 
appearance,  in  connection  with  the  vessels  of  the  subjacent  surface;  the  first 
appearance  of  this  network  is  in  the  form  of  transparent  arborescent  streaks, 
which  push  out  extensions  on  all  sides ;  these  encounter  one  another,  and 
form  a  complete  series  of  capillary  reticulations,  the  distribution  of  which  very 
nearly  resembles  that  which  has  been  seen  in  the  villi  of  the  intestines  (Fig. 
204). — From  the  observations  of  Mr.  Travers*  it  appears,  that  isolated  glob- 
ules enter  these  capillary  tubes,  and  perform  an  oscillatory  motion  in  them 
for  some  hours,  before  any  series  of  them  passes  into  it ;  so  that  we  cannot 
regard  the  new  channel  as  burrowed  out  by  a  string  or  file  of  red  corpuscles, 
pushed  out  from  the  nearest  capillary  by  vis  a  tergo,zs  some  have  maintained. 
And  he  has  further  established  two  important  facts,  in  the  history  of  the  Re- 
paration of  Tissues,  which  correspond  with  the  observation  just  cited: — 1. 
That  the  Liquor  Sanguinis  first  effused  is  not  sufficiently  organizable  to  be- 
come an  entirely  new  and  permanent  tissue  ;  although  adequate  both  to  afford 
nutrition  to  the  old,  and  to  form  a  new  tissue  of  temporary  character : — and, 
2.  That  the  generation  of  the  new  tissues  is  preceded  by  the  collection  of  a 
large  number  of  white  corpuscles,  in  a  nearly  stationary  condition,  in  the 
blood-vessels  immediately  subjacent ;  and  by  the  appearance  of  a  large  number 
of  similar  cells  in  the  newly-forming  tissue  ;  the  two  together  constituting 
what  Mr.  T.  has  aptly  called  "  the  new  lymph-bed  of  organization."  The 
views  formerly  advanced  (§§  154-159)  respecting  the  function  of  the  Colour- 
less Corpuscles,  are  thus  strikingly  confirmed. — This  process  of  Reparation 
appears  to  be  conformable,  in  all  essential  particulars,  with  that  which  has 
been  observed  in  the  first  Development  of  new  parts, — such  as  the  toes  of  the 
larva  of  the  Water-Newt. 

796.  Although  many  have  doubted  whether  effusions  of  Blood  could  thus 
become  organized,  there  seems  no  valid  reason  to  think  that  its  Fibrine  would 
comport  itself  in  any  other  way,  when  Red  particles  are  included  in  its  coa- 
gulum,  than  when  they  are  absent.     That  large  masses  of  extravasated  Blood 
should  exhibit  little  or  no  tendency  to   organization,  will   not  be  considered 
surprising;  when  it  is  remembered  that  only  their  surface  can  be  in  that  re- 
lation with  a  living  membrane,  which  has  been  stated  to  be  essential  to  the 
further  vitalization  of  the  effused  Fibrine  (§119).    It  has  been  proved  in  many 
instances,  however,  that  Coagula  of  Blood  completely  inclosed  within  the  body 
possess  an  incipient  vascularity,  being  capable  of  injection  from  the  surface 
beneath  (§  700) ;t  and  there  is  no  valid  reason  to  deny  that  the  thin  layer  of 
Blood  which  remains  between  the  lips  of  an  incised  wound,  when  these  are 
closely  brought  together,  is  the  medium  of  their  reunion.  It  is  unquestionable, 
however,  that  the  Fibrine  of  an  ordinary  Blood-clot  is  less  highly-elaborated, 
and   consequently  less   susceptible   of  organization,  than  that  of  the  Liquor 
Sanguinis,  which  is  poured  forth  after  an  injury,  and  which  has  been  subjected 
to  the  local  action  that  is  its  immediate  result. 

797.  To  the  second  mode  of  Reparation,  attention  has  recently  been  strongly 
directed  by  Dr.  Macartney  ;  and  as  this,  too,  is  a  strictly  Physiological  action, 
and  is  one  which  the  Surgeon   should   aim  at  producing,  it  will  be  here  dis- 
cussed somewhat  in  detail.     The   Surgeon  has,  until  recently,  regarded  the 
processes  of  Granulation   and   Suppuration,  which   are   attended  with   much 
local  Inflammation,  and  with  a  considerable  amount  of  Constitutional  disturb- 
ance when  the  surface  is  large,  as  the  only  means  by  which  an  open  wound 

*  Physiology  of  Inflammation  and  the  Healing  Process. 

j"  For  well-established  cases  of  this  sort,  see  communications  by  Mr.  Dalrymple  in  the 
Medico-Chirurgical  Transactions,  vol.  xxiii.;  and  in  Lancet,  March  23,  1844. 
51 


602  OF  NUTRITION. 

can  be  filled  up.  Occasional  instances,  however,  have  not  heen  wanting,  in 
which  large  open  wounds  have  closed  up  under  the  dry  clot  of  blood,  by  which 
they  were  at  first  covered  over,  without  any  suppuration,  or  other  symptom 
of  inflammation ;  and  in  these  it  has  been  found,  that  the  new  surface  much 
more  nearly  resembles  the  ordinary  one,  than  does  the  Cicatrix  which  follows 
granulation.  To  Dr.  Macartney,  however,  is  due  the  merit  of  explaining  the 
rationale  of  this  action ;  which  is  precisely  analogous  to  that  which  is  con- 
cerned in  the  ordinary  processes  of  growth,  and  to  that  reproduction  of  whole 
parts  which  takes  place  in  the  lower  animals  without  Inflammation.  It  is 
termed  by  him  the  modelling  process ;  and  he  remarks  as  characteristic  of  it 
that,  when  it  goes  on  perfectly,  and  without  Inflammation,  the  patients  are  so 
completely  free  from  uneasy  sensations,  as  only  to  be  aware  of  the  extent  of  the 
injury  by  their  own  examination.  In  this  process,  the  surfaces  of  the  wound 
do  not  unite  by  vascular  connection,  even  when  they  lie  in  contact;  nor  is  the 
space  between  them  filled  up  with  coagulable  lymph ;  but  they  are  smooth 
and  red,  moistened  with  a  fluid,  and  presenting  the  appearance  of  one  of  the 
natural  mucous  membranes.  "  It  might  be  anticipated  that,  as  this  mode  of 
reparation  bears  so  strong  a  resemblance  to  the  natural  formation  and  develop- 
ment of  parts,  it  is  the  slowest  mode  ;  but  this  is  of  little  account,  when  com- 
pared with  its  great  advantages  in  being  unattended  with  pain,  inflammation, 
and  constitutional  sympathy,  and  leaving  behind  it  the  best  description  of 
cicatrix."  In  the  case  of  large  burns  on  the  trunk  in  children,  the  difference 
between  the  two  modes  of  Reparation  will  frequently  be  that  of  life  and  death; 
for  it  often  happens  that  the  patient  sinks  under  the  great  constitutional  dis- 
turbance occasioned  by  a  large  Suppurating  surface,  although  he  has  survived 
the  immediate  shock  of  the  injury. 

798.  The  most  effectual  means  of  promoting  this  kind  of  Reparative  pro- 
cess, and  of  preventing  the  interference  of  Inflammation,  vary  according  to 
the  nature  of  the  injury.  The  exclusion  of  air  from  the  surface,  and  the 
regulation  of  the  temperature,  appear  the  two  points  of  chief  importance.  By 
Dr.  Macartney,  the  constant  application  of  moisture  is  also  insisted  on.*  He 
states  that  the  immediate  effects  of  injuries,  especially  of  such  as  act  severely 
upon  the  sentient  extremities  of  the  nerves,  are  best  abated  by  the  action  of 
"steam  at  a  high  but  comfortable  temperature,  the  influence  of  which  is 
gently  stimulant,  and  at  the  same  time  extremely  soothing.  After  the  pain 
and  sense  of  injury  have  passed  away,  the  steam,  at  a  lower  temperature, 
may  be  continued;  and,  according  to  Dr.  M.,  no  local  application  can  com- 
pete with  this,  when  the  Inflammation  is  of  an  active  character.  For  subse- 
quently restraining  this,  however,  so  as  to  promote  the  simple  Reparative 
process.  Water-dressing  will,  he  considers,  answer  sufficiently  well;  its  prin- 
cipal object  being  the  constant  production  of  a  moderate  degree  of  Cold, 
which  diminishes,  whilst  it  does  not  extinguish,  sensibility  and  vascular 
action,  and  allows  the  Reparative  process  to  be  carried  on  as  in  the  inferior 
tribes  of  animals.  The  reduction  of  the  heat  in  an  extreme  degree,  as  by 
the  application  of  ice  or  iced  water,  is  not  here  called  for,  and  would  be 
positively  injurious;  since  it  not  only  renders  the  existence  of  Inflammation 
in  the  part  impossible,  but,  being  a  direct  sedative  to  all  vital  actions,  suspends 
also  the  process  of  restoration.  The  efficacy  of  Water-dressing  in  injuries 
of  the  severest  character,  and  in  those  which  are  most  likely  to  be  attended 
with  violent  Inflammation  (especially  wounds  of  the  large  joints)  has  now 
been  established  beyond  all  question;  and  its  employment  is  continually 
becoming  more  general.! — Other  plans  have  been  proposed,  however,  which 

*  Treatise  on  Inflammation,  p.  178. 

•j-  See  an  account  of  the  results  of  this  treatment  by  Dr.  Gilchrist,  in  Brit,  and  For.  Med. 
Rev.,  July  1846,  p.  242. 


ORIGIN  OF  THE  SOLID  TISSUES.  603 

seem  in  particular  cases  to  be  equally  effectual.  To  Dr.  Greenhow,  of  New- 
castle, for  instance,  it  was  accidentally  suggested,  a  few  years  since,*  to  cover 
the  surface  of  recent  burns  with  a  liquefied  resinous  ointment;  and  he  states 
that  in  this  manner  Suppuration  may  be  prevented,  even  where  large  sloughs 
are  formed;  the  hollow  being  gradually  filled  up  by  new  tissue,  which  is  so 
like  that  which  has  been  destroyed,  that  no  change  in  the  surface  manifests 
itself,  and  none  of  that  contraction,  which  ordinarily  occurs  even  under  the 
best  management,  subsequently  takes  place.  A  plan  has,  moreover,  been 
proposed  for  preventing  suppuration,  and  promoting  reparation  by  the  model- 
ling process,  which  consists  in  the  application  of  warm  dry  air  to  the  wounded 
surface.  The  experiments  made  on  this  have  not  been  entirely  satisfactory, 
but  they  seem  to  show  that,  though  the  process  of  healing  is  much  slower 
under  treatment  of  this  kind,  it  is  attended  with  less  constitutional  disturb- 
ance than  is  unavoidable  in  the  ordinary  method;  and  it  may,  therefore,  be 
advantageously  put  in  practice  in  those  cases  in  which  the  condition  of  the 
patient  requires  every  precaution  against  such  an  additional  burthen, — as  after 
amputation  in  a  strumous  subject.  But  of  the  superiority  of  this  treatment 
to  the  water-dressing,  no  evidence  has  yet  been  adduced. 

799.  The  third  method  of  Reparation, — that  by  Granulation — appears  to 
be  a  means  employed  by  Nature  for  the  purpose,  under  the  unfavourable  cir- 
cumstances of  Irritation  or  a  continuance  of  Inflammation ;  proving  that  parts 
previously  in  a  healthy  state,  are  disposed  to  heal,  in  despite  of  many  impe- 
diments thrown  in  their  way.     The  Granulation-structure  is  a  special  one, 
formed  for  a  temporary  purpose.     It  is  endowed  with  higher  vascularity  and 
a  more  rapid  power  of  growth,  than  is   possessed  by  any  modification  of 
ordinary  tissue;  but  it  is  very  easily  destroyed  by  injury,  or  by  a  higher 
degree  of  inflammation.     The  existence  of  Granulations  has  been  supposed 
to  be  necessary  to  fill  up  deficiencies;  this,  however,  is  not  altogether  true; 
as  we  occasionally  find  very  considerable  vacancies  filled  with  lymph,  which 
gradually  becomes  organized,  without  being  converted  into  granulations;  and 
the  void  may  be  also  supplied  by  the  process  of  natural  growth  just  described. 
Moreover,  it  is  only  in  the  beginning  that  granulations  take  the  place  of  the 
natural  structure;  for  the  approximation  of  the  edges  of  a  wound  filled  with 
them,  requires  that  they  should  be  removed  by  interstitial  absorption ;  so  that 
wounds  healed*  by  this  process  do  not  exhibit  any  remains  of  the  new  me- 
dium.    This  approximation  somewhat  resembles  that  which  occurs  in  open 
wounds  that  have  never  inflamed,  being  the  result  of  the  natural  processes  of 
growth;  and  it  does  not  take  place  until  the  Inflammation  has  in  great  degree 
subsided :  but  it  differs  from  the  modelling  processes  in  this, — that,  as  the  wound 
is  occupied  by  granulations,  its  closure  takes  place  prematurely,  as  it  were ; 
so  that,  when  the  granulations  are  subsequently  absorbed  altogether,  a  con- 
tracted cicatrix  is  the  result. — It  will  be  presently  seen  that  the  formation  of 
the  Granulation-structure  is  intimately  connected  with  the  elaboration  of  Pus ; 
and  this  process,  accompanied  as  it  is  with  such  great  constitutional  disturb- 
ance, and  involving  such  a  loss  of  nutritious  material,  cannot  but  be  regarded 
as  an  action  to  be  altogether  avoided,  if  possible. 

800.  We  shall  now  consider,  more  in  detail,  the  nature  of  the  process  of 
Granulation,  and  of  the  Suppuration  which  usually  accompanies  it.    Its  com- 
mencement is  exactly  conformable  to  the  first  stage  of  ordinary  reunion  by  the 
first  intention ;  for  Liquor  Sanguinis  is  thrown  out,  in  which  Exudation-cor- 
puscles present  themselves  in  large  numbers.     According  to  Gerber,  the  trans- 
formation of  these  into  a  sort  of  imperfect  Epithelium  may  be  seen  to  take 
place  within  half  an  hour.     New  layers  are  in  the  mean  time  developed ;  and 

*  Medical  Gazette,  Oct.  13,  1838. 


004  OF  NUTRITION. 

the  most  superficial  of  the  Exudation-corpuscles,  which  are  exposed  to  the 
contact  of  air,  change  their  character  (in  the  mode  to  be  presently  described, 

5  805),  and  become  Pus-Globules  ;  whilst  those  in  close  contact  with  the  sub- 
jacent surface  take  a   share   in  the  process   of  reparation.     A  new  layer  of 
exudation-corpuscles  is  next  deposited  over  this  :    of  which  the  outer  portion 
degenerates  as  before  into  pus-globules,  whilst  the  inner  part  gives  origin  to 
a  kind  of  areolar  tissue,  forming  Granulations.    These  Granulations  are  them- 
selves extremely  vascular ;  and,  as  recently  shown   by  Mr.  Listen,*  the  ves- 
sels of  the  subjacent  tissue  are  much  enlarged,  and  assume  a  varicose  charac- 
ter.    The  bright  red  colour  of  the  Granulations,  however,  does   not  depend 
on  their  vascularity  alone  ;  for  the  cells   themselves,  especially  those  most 
recently  evolved,  are  of  nearly  as  deep   a  colour  as  the  blood-globules  ;  and 
the  superficial  bleeding  which  follows  even  the   slightest  touch  of  the  granu- 
lating surface,  does  not  proceed  from  blood  shed  from  the  newly-formed  vessels 
only  ;  for  the   red  fluid   shed  in   this   manner  contains,  besides   blood-discs, 
newly-developed  red  cells,  ruddy  cytoblasts,  pale  granules  and  reddish  serum. 
It  is  a  common  property  of  animal  cytoblasts,  that  they  present  a  red  colour 
on  their  first  formation,  when  in   contact  with  oxygen ;  but  this  hue  they 
lose  again,  whether  they  advance  to  perfect  development  and  become  integral 
parts  of  a  living  tissue,  or  die  and  degenerate. 

801.  The  process  of  Granulation  and   Suppuration  appears  to  differ  from 
that  of  simple  Reparation  (the  modelling  process  of  Dr.  Macartney)  in  this, 
— that  a  large  part  of  the  Exudation-corpuscles   deposited   on   the  wounded 
surface  degenerate  into  Pus  in  the  former  case,  whilst  none  are  thus  wasted 
in  the  latter  ; — but  that  the  existence  of  Inflammation  occasions   a  more  co- 
pious supply  of  Fibrine  in  the  former  case,  and  increases  its  tendency  to  be- 
come organized  ;  the  filling-up  of  a  wound  with  Granulations   being  thus  a 
much  more  rapid  process  than  that  renewal  of  the  completely-formed  Tissues, 
which  may  take  place  in  the  absence   of  Inflammation.     The   imperfect  cha- 
racter of  the  Granulation-structure  is  shown,  by  the  almost  complete  disap- 
pearance of  it  after  the  wound  has  closed  over.     The  portion  of  it  in  immediate 
contact  with  the  subjacent  tissue,  however,  appears  to  undergo  a  higher  organi- 
zation ;  for  it  becomes  the  medium  by  which  the  Cicatrix  is  made  to   adhere 
to  the  bottom   of  the  wound.     It  is  very  liable  to  undergo  changes  which 
end  in  its  disintegration  ;  as  is  evident  from  the  known  tendency  to  re-open- 
ing, in  wounds  that  have  been  closed  in  this  manner. 

3. — Abnormal  Forms  of  the  Nutritive  Process. 

802.  Under  the  preceding  head,  we  have  considered   the  chief  variations 
in  the  degree  of  activity,  that  are  witnessed  in  the  ordinary  or  normal  condi- 
tions of  the  Nutritive  process, — that  is,  those   conditions   in  which   the  pro- 
ducts  are   adapted,  by  their  similarity  of  character,  to  replace  those  which 
have  been  removed  by  disintegration.     But  we  have  now  to  consider  those 
forms  of  this  process, — in  which  the  products  are  abnormal, — being  different 
from  the  tissues  they  ought  to  replace.     We  shall  confine  ourselves  to  a  brief 
examination  of  the  two  most  important  of  these  states  ; — that  which  is  termed 
Inflammation ; — and    that  which   gives    rise    to   Tubercular  deposit.     The 
former  results  from  an  excess  of  the  plastic  element  in  the  blood  ;  the  latter 
from  a  depraved  condition  of  it,  whereby  its  plasticity  is  impaired  or  destroy- 
ed.— Notwithstanding  all  the  attention  which  has  been  given   to  the  state  of 
the  vessels  in  Inflammation,  a  careful  consideration  of  its  phenomena,  with  the 
light  which  recent  investigations  have  thrown  upon  these,  leads  us  to  attach 

*  Medicc-Chirurgical  Transactions,  vol.  xxiii. 


ABNORMAL  FORMS  OF  THE  NUTRITIVE  PROCESS.  605 

comparatively  little  importance  to  this,  and  to  seek  for  the  essential  character  of 
the  process  elsewhere.  The  researches  of  Addison,  Williams,  Barry,  Gulli- 
ver, Andral,  and  others,  all  seem  to  point  to  the  following  conclusions  : — 1. 
That  there  is  a  peculiar  afflux  or  determination  of  the  White  Corpuscles  of 
the  Blood  towards  the  inflamed  part.  2.  That  the  total  amount  of  these  cor- 
puscles in  the  circulating  blood  undergoes  a  great  increase.  3.  That  the 
quantity  of  Fibrine  in  the  Blood  augments,  in  proportion  to  the  extent  and 
intensity  of  the  Inflammation ;  and  this,  even  when  it  was  previously,  from 
the  influence  of  some  other  morbid  condition,  below  the  usual  standard. 
With  its  quantity,  its  plasticity,  or  tendency  to  organization,  also  increases  in 
a  healthy  subject. — Now  when  these  facts  are  compared  together,  and  are 
connected  with  those  formerly  adduced,  in  regard  to  the  probable  function 
of  the  White  Corpuscles  of  the  blood,  they  lead  almost  irresistibly  to  the  con- 
clusion, that  the  process  of  Inflammation  essentially  consists  in  an  undue 
stagnation  of  these  corpuscles  in  the  vessels  of  the  part,  an  excessive  multi- 
plication of  them  by  the  ordinary  process  of  generation,  and  a  consequent 
over  production  of  Fibrine.  By  these  changes,  and  by  the  results  which  fol- 
low them,  Inflammation  may  be  distinguished  from  the  various  forms  of  Hy- 
peraemia  and  Congestion.  To  the  results,  then,  we  shall  next  direct  our  at- 
tention. 

803.  It  may  be  inferred  from  various  phenomena,  that  whilst  the  forma- 
tive power  of  the  Blood  is  increased  in  Inflammation,  that  of  the  Tissues  is 
diminished.  Certainly  this  is  the  case  in  regard  to  the  system  at  large,  when 
febrile  irritation  has  been  established;  for,  notwithstanding  the  increased  Plas- 
ticity of  the  Blood,  we  see  the  body  wasting,  instead  of  increasing  in  vigour. 
'And  it  may  be  inferred  also,  in  regard  to  the  tissues  of  the  part  aflfected, 
from  the  tendency  to  Atrophy  and' Disintegration  which  they  exhibit;  and 
which  is  greater  (leading  even  to  the  death  of  whole  parts)  in  proportion  as 
the  inflammation  is  more  intense,  and  as  the  tendency  to  the  deposit  of  new 
products  is  the  more  decided.  That  a  Stagnation  of  Blood  takes  place  in 
the  vessels  of  the  inflamed  part,  is  another  general  fact,  which  throws  some 
light  upon  the  nature  of  the  process  ;  for  this  stagnation  is  obviously  favour- 
able to  the  transudation  of  the  fluid  Plasma  of  the  blood,  through  the  walls 
of  the  vessels,  into  the  surrounding  tissue,  or  upon  a  neighbouring  surface. 
This  deposition  of  the  Fibrinous  element,  possessing  a  high  degree  of  plasti- 
city, and  capable  of  spontaneously  passing  into  simple  forms  of  tissue  (which 
may  be  gradually  replaced  by  higher  forms,  when  penetrated  by  vessels  from 
the  surrounding  parts),  may  be  regarded  as  the  first  characteristic  result  of 
Inflammation.  It  is  by  the  deposition,  and  subsequent  organization,  of  plas- 
tic matter  in  the  substance  of  organs,  that  their  tissues  become  consolidated  ; 
and  by  its  deposition  and  subsequent  organization  upon  their  free  surfaces, 
that  false  membranes  and  adhesions  are  formed.  It  appears  probable,  from 
the  recent  inquiries  of  Mr.  Robinson,*  that  this  deposition  may  be  attributed 
to  physical  causes.  It  is  well  known,  that  simple  Congestion  will  occasion 
transudation  of  the  serous  portion  of  the  Blood  ;  and  if  the  return  of  the 
Blood  by  the  veins  of  a  part  be  completely  prevented,  a  greater  or  less  pro- 
portion of  fibrine  also  may  be  poured  forth.  Now  when  the  quantity  of  Fi- 
brine in  the  blood  is  greatly  augmented,  and  the  firmness  of  the  walls  of  the 
vessels  in  the  inflamed  part  is  diminished  by  the  alterations  taking  place  iri 
their  tissue,  it  is  easy  to  understand  that  the  disposition  to  the  effusion  of  Fi- 
brine will  be  much  increased.  Sometimes  the  Fibrine  is  diluted  with  a  large 
quantity  of  Serum  ;  and  is  poured  into  a  cavity  (as  that  of  a  serous  sac)  in 
the  form  of  a  liquid,  which  afterwards  separates  into  clot  and  serum. 

*  Medico-Chirurgical  Transactions,  vol.  xxvi.  p.  51. 
51* 


606  OF  NUTRITION. 

804.  Should  the  Inflammation  increase  in  intensity,  a  complete  stagnation 
of  blood  in  the  tissue  most  affected,  or  even  in  an  entire  organ,  will  be  the 
result;  and  this  will  occasion  its  death.     If  a  large  part  be  thus  entirely  de- 
stroyed at  once,  the  process  is  termed  Gangrene;  and  it  separates  from  the 
living  part,  at  a  line  where  the  Inflammation  is  less  intense,  and  where  there 
is  a  deposit  of  Fibrine,  which  serves  the  important  purpose  of  closing  the 
mouths  of  the  blood-vessels  that  are  laid  open  by  the  process.     If  the  destruc- 
tion of  tissue,  however,  be  interstitial,  the  dead  parts  are  not  thus  thrown  off, 
but  are  taken  up  by  the  absorbent  process  ;  and  thus  the  cavity  of  an  Jlbscess, 
or  of  an  Ulcer  is  formed.     This  cavity  is  usually  bounded  by  tissue,  that  has 
been  consolidated  by  the  effusion  of  Fibrine  ; — a  fact  readily  accounted  for  on 
the  principles  just  stated.     For  the  death  and  removal  of  tissue  take  place, 
where  the  Inflammation  has  been  most  intense  and  the  stagnation  most  com- 
plete, which  is  in  the  centre  of  the  inflamed  spot;  and  the  fibrinous  effusion, 
the  result  of  moderate  inflammation,  is  poured  into  the  surrounding  tissue. 
The  elements  of  Liquor  Sanguinis  are  poured  into  the  central,  as  well  as  the 
peripheral,  portion  of  the  inflamed  tissue ;  but  they  assume  a  different  form — 
that  of  Pus.     It  would  appear  as  if  the  influence  of  the  surrounding  death  and 
decay  produces  a  degradation  of  their  character;  so  that  they  become  entirely 
aplastic  or  unorganizable,  although  immediately  derived  from  Blood  highly 
charged  with  Fibrine. 

805.  Between  Coagulable  Lymph  and  Purulent  effusions,  there  are  many 
degrees  of  transition ;  the  very  same  deposit  being  frequently  organizable  at 
one  part, — presenting  the  character  of  a  tough  fibrous  membrane,  interspersed 
with  corpuscles, — whilst  it  is  friable  in  another,  from  want  of  complete  fibril- 
lation in  the  fluid  portion  of  th£  effusion, — and  is  entirely  destitute  of  tenacity 
in  a  third  portion,  especially  the  superficial  part,  or  free  surface,  of  the  deposit. 
When  examined  by  the  Microscope,  Pus  is  found  to  be  characterized  by  the 
presence  of  a  number  of  cells  of  a  peculiar  aspect,  having  a  very  tuberculated 
or  mulberry  surface ;  these  are  seen  floating  in  a  fluid,  termed  liquor  puris,, 
which  is  of  an  albuminous  or  low  fibrinous  character,  being  entirely  destitute 
of  organizability.     Now  the  production  of  Pus  in  an  inflamed  part,  or  in  other 
words,  the  act  of  Suppuration,  may  be  due  to  one  of  three  causes,  viz. — the 
intensity  of  the  inflammation ;  the  presence  of  air,  which  becomes  a  source  of 
irritation  ;  and   a  previously  vitiated  state  of  the   blood.     Various  attempts 
have  been  made  to  show  that  the  Pus-globule  is  a  degenerated  red  or  white 
corpuscle  of  the  Blood  ;  it  seems  more  probable,  however,  that  it  does  not 
escape  from  the  vessels  as  a  complete  cell,  but  as   a  cell-germ,  which  may 
have  had  its  origin  in  a  white  corpuscle  of  the  blood ;  and  which,  under 
favourable  circumstances,  might  have  produced  an  Exudation-corpuscle  (§  800). 
At  any  rate,  it  must  be  regarded  as  a  degenerated  form  of  cell ;  and  the  liquor 
puris  must  be  considered  as  analogous  to  the  plasma  of  the  Blood  in  a  de- 
generated state. 

806.  In  what  manner  the  Inflammatory  process  determines  the  formation 
of  the  Pus-cell,  and  the  consequent  degradation  of  the   product,  we  are  at 
present  unable  to  state  ;  but  that  the  degree  of  irritation  in  the  part  has  an 
influence  upon  it,  is  evident  from  the  effects  of  the  contact  of  air  upon  inflamed 
surfaces,  causing  those  elements  to  take  the  form  of  Pus,  which  would  other- 
wise have  been  thrown  out  as  a  plastic  deposit.     This  circumstance  would 
seem  to  indicate,  beyond  all  doubt,  that  the  Exudation  and  Pus-corpuscles, 
the  plastic  Lymph  and  the  aplastic  Liquor  puris  have  the  same  origin ;  but 
that  their  character  is  determined  by  local  circumstances.     There  is  great 
reason  to  believe,  that  when  Pus  is  introduced  into  the  Blood,  it  may  induce 
such  a  change  in  the  character  of  the  fluid,  as  speedily  to  impair  its  vital  pro- 
perties ;  so  that  the  Pus-corpuscles  will  rapidly  propagate  themselves  in  the 


ABNORMAL  FORMS  OF  THE  NUTRITIVE  PROCESS.  607 

Blood,  and  the  plasticity  of  the  Liquor  Sanguinis  will  be  diminished.  In  this 
manner  the  whole  system  will  be  seriously  affected,  and  there  will  be  a  tend- 
ency to  deposits  of  Pus  in  various  organs — especially  in  those  which,  like  the 
Lungs  and  Liver,  serve  as  emunctories  to  the  system — without  any  previous 
inflammatory  changes  in  these  parts.  It  has  been  ascertained  by  Mr.  Addi- 
son,  that  if  a  drop  of  Pus  be  treated  with  Liquor  Potassa?,  it  entirely  loses  its 
opaque  character,  and  becomes  clear  and  transparent,  like  Mucus, — with  whose 
tenacity  and  elasticity  also  it  becomes  endowed.  If  it  be  then  treated  with 
acetic  acid,  it  recovers  somewhat  of  its  former  opacity ;  and,  when  pressed 
into  a  thin  film,  exhibits  a  distinct  fibrillation. 

807.  In  persons  of  that  peculiar  constitution,  which  is  te*rmed  Scrofulous 
or  Strumous,  we  find  an  imperfectly-organizable  or  Caco-plastic  deposit,  or 
even  an  altogether  aplastic  product,  known  by  the  designation  of  Tuberculcft 
matter,  frequently  taking  the  place  of  the  normal  elements  of  Tissue  ;  both 
in  the  ordinary  process  of  Nutrition,  and  still  more  when  Inflammation  is  set 
up.     From  an  examination  of  the  Blood  of  Tuberculous  subjects  it  appears, 
that  the  Fibrinous  element  is  not  deficient  in  amount,  but  that  it  is  not  duly 
elaborated ;  so  that  the  coagulum  is  loose,  and  the  red  corpuscles  are  found 
to  bear  an  abnormally  low  proportion  to  it.     We  can  understand,  therefore, 
that  such  a  constant  deficiency  in  Plasticity  must  affect  the  ordinary  nutritive 
process ;  and  that  there  will  be  a  liability  to  the  deposit  of  cacoplastic  pro- 
ducts, without  Inflammation,  instead  of  the  normal  elements  of  tissue.     Such 
appears  to  be  the  history  of  the  formation  of  Tubercles  in  the  lungs  and  other 
organs,  when  it  occurs  as  a  kind  of  metamorphosis  of  the  ordinary  Nutritive 
process  ;  and  in  this  manner  it  may  proceed  insidiously  for  a  long  period,  so 
that  a  large  part  of  the  tissue  of  the  lungs  shall  be  replaced  by  an  amorphous 
deposit,   without  any  other  ostensible  sign  than  an  increasing  difficulty  of 
respiration.     It  is  in  the  different  forms  of  Tubercular  deposit,  that  we  see 
the  gradation  most  strikingly  displayed  between  the  plastic  and  the  aplastic 
formations.     In  the  semi-transparent,  miliary,  gray,  and  tough  yellow  forms 
of  Tubercle,  we  find  traces  of  organization  in  the  form  of  cells  and  fibres, 
more  or  less  obvious  ;  these  being  sometimes  almost  as  perfectly  formed  as 
those  of  Plastic  Lymph,  at  least  on  the  superficial  part  of  the  deposit,  which 
is  in  immediate  relation  with  the  living  structures  around ;  and  sometimes  so 
degenerated,  as  scarcely  to  be  distinguishable.     In  no  instances  do  such  de- 
posits ever  undergo  further  organization;  and  therefore  they  must  be  regarded 
as  caco-plastic.     But  in  the  opaque,  crude,  or  yellow  Tubercle,  we  do  not 
find  even  these  traces  of  definite  structure;  for  the  matter  of  which  it  con- 
sists is  altogether  granular,  more  resembling  that  which  we  find  in  an  albu- 
minous  coagulum.     The  larger  the  proportion  of  this  kind  of  matter  in  a 
tubercular  deposit,  the  more  is  it  prone  to  soften,  whilst  the  semi-organized 
tubercle  has  more  tendency  to  contraction.     This  is  entirely  aplastic. 

808.  Now  although  Tubercular  matter  may  be  slowly  and  insidiously  de- 
posited, by  a  kind  of  degradation  of  the  ordinary  Nutritive  process,  yet  it  can- 
not be  doubted  that  Inflammation  has  a  great  tendency  to  favour  it ;  so  that  a 
larger  quantity  may  be  produced  in  the  lungs,  after  a* Pneumonia  has  existed 
for  a  day  or  two,  than  it  would  have  required  years  to  generate  in  the  pre- 
vious mode.     But  the  character  of  the  deposit  still  remains  the  same  ;  and  its 
relation  to  the  plastic  element  of  the  blood  is  shown  by  the  interesting  fact,  of 
no  unfrequent  occurrence, — that,  in   a  Pneumonia  affecting  a  Tuberculous 
subject,  Plastic  Lymph  is  thrown  out  in  one  part,  whilst  Tubercular  matter  is 
deposited  in  another.     Now  Inflammation,  producing  a  rapid  deposition  of 
Tubercular  matter,  is  peculiarly  liable  to  arise  in  organs,  which  have  been 
previously  affected  with  chronic  Tubercular  deposits,  by  an  impairment  of 
the  process  of  textural  Nutrition ;  for  these  deposits,  acting  like  foreign  bodies, 


608  OF  NUTRITION. 

may  of  themselves  become  sources  of  irritation ;  and  the  perversion  of  the 
structure  and  functions  of  the  part  renders  it  peculiarly  susceptible  of  the 
influence  of  external  morbific  causes. — These  views,  at  which  several  recent 
Physiologists  and  Pathologists  have  arrived  on  independent  grounds,  seem  to 
reconcile  or  supersede  all  the  discordant  opinions  which  have  been  upheld  at 
different  times  regarding  the  nature  of  Tubercle ;  and  lead  to  the  soundest 
views  with  respect  to  the  treatment  of  the  Diathesis. 

809.  We  frequently  meet  with  abnormal  growths  of  a  Fatty,  Cartilaginous, 
Fibrous,  or  even  Bony  structure;  which  result  from  the  development  of  these 
tissues  in  unusual  situations,  and  appear  to  originate  in  some  perverted  action 
of  the  parts  themselves. — But  there  is  another  remarkable  form  of  disordered 
Nutrition,  which  is  concerned  in  producing  what  have  been  termed  hetero- 
togous  growths, — that  is,  masses  of  tissue,  differing  in  character  from  any 
which  is  normally  present  in  the  body.  Most  of  these  are  included  under 
the  general  designation  of  Cancerous  or  Fungous  structures  ;  and  it  has  been 
shown  by  Miiller  and  others,  that  the  new  growth  consists  of  a  mass  of  cells; 
which,  like  the  Vegetable  Fungi,  develope  themselves  with  great  rapidity ;  and 
which  destroy  the  surrounding  tissues  by  their  pressure,  as  well  as  by  ab- 
stracting from  the  Blood  the  nourishment  which  was  destined  for  them. 
These  parasitic  masses  have  a  completely  independent  power  of  growth  and 
reproduction ;  and  it  seems  difficult  to  refuse  them  the  character  of  distinct 
existences.  They  can  be  propagated  by  inoculation,  which  conveys  into  the 
tissues  of  the  animal  operated  on,  the  germs  of  the  peculiar  cells  that  consti- 
tute the  morbid  growth  ;  and  these  soon  develope  themselves  into  a  new 
mass.  It  seems  to  be  by  the  diffusion  of  the  germs  produced  in  one  part, 
through  the  whole  fabric,  by  the  circulating  current,  that  the  tendency  to  re- 
appearance (which  is  one  great  feature  in  the  malignant  character  of  these 
diseases)  is  occasioned.  Yet  there  is  no  evidence,  that  the  first  production 
of  a  Cancerous  growth  is  due  to  germs  introduced  from  without;  in  fact,  as 
it  appears  to  the  Author,  the  history  of  its  origin,  as  well  as  the  analogy  of 
similar  cases,  makes  it  far  more  probable,  that  the  Cancer-cell  is  but  an  abnor- 
mal form  of  the  ordinary  tissue-cells  of  the  body, — being,  in  fact,  a  cell  which 
possesses  to  an  unusual  degree  the  power  of  reproduction,  instead  of  under- 
going those  transformations  by  which  it  would  be  converted  into  other 
kinds  of  tissue. 

a.  Several  instances  have  been  recently  published,  of  the  occurrence  of  Vegetable  organ- 
isms as  parasites  upon  the  Animal  body.     That  in  some  of  these  a  true  Plant,  possessing  a 
regular  apparatus  of  nutrition  and  reproduction,  has  arisen  from  a  germ  introduced  from 
without,  there  can  be  little  question ;  but  in  other  instances  (as  in  the  case  of  the  crusts  of 
Porrigo  favosa),  it  has  been  assumed  that  the  organization  is  Vegetable,  merely  because  it 
consists  of  a  mass  of  cells  capable  of  extending  themselves  by  the  ordinary  process  of  mul- 
tiplication.    But  it  must  be  remembered,  that  the  cellular  organization  is  common  to  Ani- 
mals as  well  as  to  Plants ;  being  the  only  form  that  manifests  itself  at  an  early  period  of 
development  in  either  kingdom,  and  remaining  throughout  life  in  those  parts  which  have 
not  undergone  a  metamorphosis  for  special  purposes.     Hence  to  speak  of  Porrigo  favosa,  or 
any  similar  disease,  as  produced  by  the  growth  of  a  Plant  within  the  Animal  body,  appears 
to  the  Author  a  very  arbitrary  assumption ;  the  simple  fact  being,  in  regard  to  this  and  many 
other  structures  of  a  low  type,  that  they  present  the  simplest  or  most  general  kind  of  organ- 
ization.    Their  nature  must  be  decided  by  their  Chemical  constitution ;  and  this,  in  the  case 
of  the  Porrigo  favosa,  appears  to  be  unquestionably  Animal. 

b.  There  seems  a  strong  probability  in  the  idea,  that  the  propagation  of  many  diseases  by 
inoculation,  essentially  consists  in  the  transplanting  of  cell-germs  from  the  body  of  one  ani- 
mal to  that  of  another.     Thus  the  Vaccine  Vesicle  appears  to  be  made  up  of  an  aggregation 
of  distinct  cells,  to  which  we  may  very  fairly  attribute  an  origin  of  this  kind.    But  this  seems 
rather  true  of  diseases  which  manifest  themselves  by  a  local  development  of  cellular  struc- 
tures,— such  as  Cancer  and  Cow-pox, — than  of  such  as  Hydrophobia,  Plague,  Poisoning  by 
Serpents,  &c.,  in  which  the  symptoms  are  referrible,  more  or  less  clearly,  to  an  alteration  in 
the  character  of  the  Blood,  by  the  introduction  of  a  substance  acting  as  a  ferment  (§  708). 


VARYING  DURATION  OF  CELL-LIFE.  609 


4. —  Varying  duration  of  different  parts  of  the  Organism. 

810.  From   the  foregoing  details  the  obvious  inference  results, — that  each 
part  of  the  organism  has  an  individual  Life  of  its  own,  whilst  contributing  to 
uphold  the  general  Life  of  the  entire  being.     This  Life,  or  state  of  Vital 
Action,  depends  upon  the  due  performance  of  the  functions  of  all  the  subordi- 
nate parts,  which  are  closely  connected  together.     The  lowest  classes  of  or- 
ganized beings   are  made  up  of  repetitions  of  the  same  elements;  and  each 
part,  therefore,  can  perform  its  functions  in  great  degree  independently  of  the 
rest.     But,  in  ascending  the  scale,  we  find  that  the  lives  of  the  individual  parts 
become  gradually  merged  (so  to  speak)  in  the  general  life  of  the  structure  ; 
for  these  parts  gradually  become  more  and  more  different  in  function,  and 
therefore  more  and  more  dependent  on  each  other  for  their  means  of  support ; 
so  that  the  activity  of  all  is  necessary  for  the  maintenance  of  any  one. 

811.  The  doctrine  of  Development  from  Cells  gives  us  a  clearer  idea  of  the 
nature  of  the  continual  process  of  decay  and  renewal,  which  take  place  in  the 
Animal  body.     Every  Cell  has,  to  a  certain  degree,  an  individual  life  of  its 
own.     This  individuality  is  much  more  decided  in  the  lower  forms  of  organ- 
ized being,  where  each  cell  can  maintain  an  independent  existence,  than  ifcis 
in  the  higher,  in  whose  fabric  a  large  number  having  different  functions  are 
united  into  one  structure,  the  combined  activity  of  the  whole  of  which  is 
necessary  to  the  life  of  any  one.     But,  even  in  the  highest,  it  is  evident  that 
each  cell  will  possess  a  certain  duration  of  its  own  ;  and  that,  from  its  first 
period  of  development,  all  the  changes  which  it  undergoes  are  governed  by 
laws  peculiar  to  it.     In  the  various  parts  of  the  Vegetable,  as  in  those  of  the 
Animal,  we  find  a  great  difference  in  the  duration  of  the  existence  of  the  cells 
composing  them.     These  differences  may  be  reduced  to  five  heads. 

i.  Cells  may  be  generated,  which  have  a  very  transient  existence,  and 
"which  disappear  again,  without  undergoing  any  transformation.  This  may  be 
seen  in  the  Vegetable  ovule,  and  in  the  Germinal  Vesicle  of  the  Animal  Ovum  ; 
as  well  as  in  many  other  parts.  Thus  we  have  Absorbent  Cells  (§  181), 
Secreting  Cells  (§  179),  and  probably  Assimilating  or  Fibrine-elaborating 
Cells  (§  154);  all  of  which  originate  in  pre-existing  germs,  attain  their  full 
development  (in  the  course  of  which  they  perform  their  allotted  function), 
and  then  disappear  by  rupture  or  liquefaction.  In  such  instances  it  is  obvious 
that,  from  their  first  origin,  the  cells  are  subject  to  a  law  of  limited  duration, 
and  that  their  death  and  decay  are  as  much- the  result  of  their  inherent  consti- 
tution, as  are  those  of  each  entire  Animal  or  Vegetable  organism. 

ii.  The  contrary  extreme  to  this  may  be  found  in  those  Cells,  of  which  the 
function,  instead  of  being  transient,  is  to  be  indefinitely  prolonged ;  such  are 
those  of  which  the  organs  of  mechanical  support  are  usually  formed.  Here 
the  cell,  instead  of  changing  its  form,  or  of  giving  origin  to  new  cells  within 
itself,  becomes  the  subject  of  an  internal  deposit  of  hard  matter,  which  lines 
its  walls,  and  cuts  it  off,  more  or  less  completely,  from  the  general  course  of 
Vital  Action.  When  this  is  the  case,  and  the  hard  matter  is  not  itself  liable 
to  decomposition,  the  duration  of  the  cell-walls,  which  are  protected  by  their 
peculiar  aggregation  from  exposure  to  decomposing  agents,  may  undergo  little 
or  no  change  for  an  almost  indefinite  period.  Thus  the  heart-wood  of  Plants, 
the  Bones  of  Animals,  and  still  more  their  Hair,  Hoofs,  Horns,  &c.,  may  re- 
main unaltered  through  a  long  series  of  years.  Of  some  of  these  parts  it  can 
scarcely  be  said  that  they  are  less  alive,  when  removed  from  the  organism  to 
which  they  belonged,  than  when  included  in  it.  In  the  heart-wood  of  a  Plant, 
for  example,  no  vital  change  takes  place,  from  the  time  that  the  woody  tubes 
and  cells  are  once  consolidated  by  internal  deposition ;  it  may  decay,  whilst 


610  OF  NUTRITION. 

still  forming  part  of  the  stem,  without  interfering  with  the  nutritive  operations 
of  the  tree  ;  and  if  we  could  possibly  remove  it  entirely,  without  doing  injury 
by  the  operation  to  the  rest  of  the  structure,  its  absence  would  be  productive 
of  no  other  evil  consequences  than  those  which  would  necessarily  result 
from  the  withdrawal  of  the  mechanical  support  afforded  by  it.  The  same 
may  be  said  of  the  Epidermic  Appendages  of  Animals,  and  of  the  External 
Skeletons  of  many  Invertebrata ;  which  remain  equally  unchanged  from  the 
time  of  their  first  formation. — Now  as  long  as  these  structures  hold  together, 
it  is  evident  that  the  organized  part  of  them  must  have  undergone  little  change 
from  the  condition  in  which  it  existed  in  the  living  fabric ;  and  that  their 
death  takes  place,  in  reality,  only  when  the  structures  decay, — this  decay 
being,  in  fact,  the  consequence  of  it.  The  law  of  existence  of  such  cells, 
therefore,  is  that  of  indefinitely -prolonged  duration  ;  this  law  must  have  been 
impressed  upon  them  from  their  origin;  and  the  power  by  which  their  walls 
secrete  and  deposit  the  consolidating  materials,  appears  to  be  the  chief  means 
of  keeping  it  in  operation. 

in.  In  all  the  higher  forms  of  Animal  structure,  the  Cells  originally  com- 
posing it  are  only  the  means  of  generating  tissues  of  other  kinds,  in  which 
the  Cellular  character  is  less  obvious.  Thus  the  Muscular  and  Nervous  tis- 
s*fes  have  their  origin  in  cells,  which  at  first  appear  in  no  respect  different 
from  others,  but  which  subsequently  undergo  a  peculiar  metamorphosis,  and 
themselves  no  longer  exist  as  such.  Upon  all  these  primordial  cells,  there- 
fore, a  law  of  transformation  is  impressed,  from  the  time  of  their  first  pro- 
duction. In  their  original  aspect,  they  cannot  be  distinguished  from  the  cells 
which  are  not  destined  to  undergo  any  such  metamorphosis;  but,  just  as  the 
first  cell  of  the  embryo,  from  which  Man  is  produced,  must  have  some  real 
though  not  apparent  difference  from  that  in  which  the  Polype  originates,  so 
must  the  cell  which  is  afterwards  developed  into  Muscular  Fibre,  be  inherently 
different  from  that  which  is  subsequently  converted  into  Nervous  tissue. 

iv.  The  tissues,  thus  formed  by  the  transforming  processes  to  which  certain 
Cells  are  subject,  are  evidently  governed  by  the  same  laws  of  Nutrition  as 
those  which  regulate  ordinary  Cell-growth ;  these  are  modified  in  their  action, 
however,  by  the  conditions  in  which  they  are  placed,  in  regard  to  the  activity 
of  the  function  which  the  Tissue  is  called  upon  to  perform.  In  all  instances, 
however,  these  Tissues  have  a  limited  period  of  existence.  They  are  gene- 
rated, they  grow  from  the  alimentary  materials  with  which  they  are  supplied, 
they  arrive  at  maturity,  they  decline,  they  die,  and  they  decay;  just  as  do  the 
isolated  vesicles  constituting  the  humblest  forms  of  vegetation.  For  all  of 
them  there  is  an  appointed  duration  of  life,  just  as  there  is  for  the  entire  Man. 
— Now  on  this  view  we  can  explain  many  physiological  phenomena,  which 
cannot  otherwise  be  very  satisfactorily  accounted  for.  It  is  owing  to  the  con- 
tinual death  and  decay  of  its  component  cells,  that  the  process  of  decomposition 
goes  on  with  such  constancy  and  uniformity  in  the  living  body;  whilst,  on  the 
other  hand,  it  is  by  the  continual  reproduction  of  new  cells,  in  the  place  of 
those  which  have  disappeared,  that  the  normal  organization  is  maintained. 
The  limited  duration  of  the  life  of  the  cells  composing  the  various  tissues  is 
further  made  evident,  by  the  rapid  disappearance  of  the  normal  organization, 
and  by  the  loss  of  the  functional  power  of  those  tissues,  when  the  cessation 
of  their  activity  prevents  the  development  of  the  new  cells,  by  which  alone 
their  character  can  be  maintained.  Of  the  change  of  structure  and  loss  of 
power  which  result  from  disuse  and  consequent  want  of  nutrition  in  Muscular 
and  Nervous  tissues,  instances  have  already  been  given  (§§  588  and  790). 
The  ordinary  processes  of  Decomposition  and  Interstitial  Absorption  are  pro- 
bably less  rapid  than  usual  under  such  circumstances ;  so  that  the  length  of 
time  required  for  the  disappearance  of  the  characteristic  structure,  and  the 


VARYING  DURATION  OF  DIFFERENT  PARTS.  Oil 

consequent  loss  of  functional  power,  affords  us  some  idea  of  the  limit  to  the 
duration  of  the  life  of  the  tissue.  It  may  be  stated,  then,  as  a  general  pro- 
position, that  the  interstitial  change,  which  the  whole  structure  of  the  body  is 
continually  undergoing,  in  its  normal  or  physiological  condition,  is  due  to  the 
regularly-occurring  death  and  reproduction  of  its  component  cells,  of  which 
every  one  has  its  own  limit  of  duration.  We  uniformly  find  that  those 
Tissues,  in  which  the  most  active  vital  changes  are  going  on  (such  as  the 
Nervous  and  Muscular),  are  those  in  which  the  duration  of  the  individual 
component  portions  is  the  least;  as  is  shown  by  the  rapidity  of  the  changes 
of  removal  and  reposition,  which  are  continually  taking  place  in  them.  The 
converse  holds  good  also.  Further  it  may  be  remarked, — and  this  is  a  matter 
of  much  practical  importance, — that  anything  which  increases  the  functional 
activity  of  any  particular  tissue,  thus  causing  it  to  live  faster,  diminishes  the 
duration  of  its  life ;  as  is  shown  in  the  increased  rapidity  of  disintegration, 
which  results  from  the  continued  exercise  of  the  Muscular  and  Nervous 
systems. 

v.  There  is  yet  another  phase,  under  which  Cellular  life  presents  itself  as 
a  natural  condition  in  the  lower  organisms,  and  in  the  early  condition  of  the 
higher ;  but  which  constitutes  a  morbid  state  in  the  adult  condition  of  the 
latter.  This  is  when  cells  reproduce  themselves  with  extreme  rapidity, — 
neither  the  primary  nor  secondary  cells  undergoing  any  further  transforma- 
tion,— and  the  duration  of  each  individual  being  limited  by  the  development 
of  its  progeny  within  it,  causing  its  own  distension  and  final  rupture  or  dis- 
appearance. The  growth  of  the  lower  Fungi  offers  a  striking  example  of  this 
in  the  Vegetable  kingdom ;  and  the  early  processes  of  development  in  the 
Ovum  of  the  highest  Animals,  exhibit  the  same  character.  Every  cell,  as  it 
is  generated,  proceeds  at  once  to  the  work  of  multiplication,  for  which  it 
seems  specially  destined;  and  thus  it  is  subject  from  the  first  to  the  law  of 
Reproduction.  It  is  this  which  distinguishes  the  Fungoid  diseases ;  which 
derive  the  character  designated  by  the  Surgeon  as  malignancy,  simply  from 
their  tendency  to  propagation,  and  his  want  of  power  to  control  it.  It  seems 
probable  that  many  other  changes  of  structure  are  due  to  a  corresponding 
cause. 

812.  The  duration  of  the  existence  of  the  individual  Cells  in  corresponding 
parts,  is  further  subject  to  variation,  in  accordance  with  the  period  of  life  of 
the  entire  organism.  Thus  all  the  tissues,  even  those  most  consolidated,  are 
undergoing  continual  changes  in  the  young  animal,  in  which  the  processes  of 
decay  and  renewal  go  on  much  faster  than  in  the  adult ;  and  in  the  adult,  than 
in  the  aged  person.  Even  the  cells  of  the  Bony  structure,  which  in  the  adult 
are  almost  permanent,  and  in  the  aged  person  are  subject  to  extremely  little 
change,  are  liable  in  the  infant  to  an  early  decomposition ;  their  places  being 
filled  up  by  others,  of  which  the  form  adapts  itself  to  the  growth  of  the  struc- 
ture. This  may  be  partly  accounted  for  by  the  imperfect  degree,  in  which, 
so  long  as  the  entire  organism  is  undergoing  rapid  increase,  the  normal  struc- 
ture is  developed  in  any  one  portion  of  it;  for  the  degree  of  consolidation 
being  less,  the  tendency  to  decay  will  naturally  be  greater.  But  this  explana- 
tion is  not  in  itself  sufficient ;  and  we  must  be  content  for  the  present  to 
regard  it  as  a  general  law  (which  may  ultimately  prove  to  be  but  a  result  of 
some  more  general  principle)  that  the  duration  of  the  existence  of  individual 
cells  increases,  cseteris  paribus,  with  the  advance  of  life.  At  the  same  time, 
their  functional  activity  diminishes.  They  may  be  said  to  live  more  slowly. 
The  dull  perceptions,  and  slow  and  feeble  movements,  of  the  aged  man,  form 
a  striking  contrast  with  the  acute  sensibility,  and  the  rapid  and  vigorous  mus- 
cular actions,  of  the  child ;  and  the  same  change  may  be  noticed  in  the  organic 
functions.  Hence  it  may  be  stated  as  a  general  law,  that  the  vital  activity  of 


612  OF  NUTRITION. 

the  Cells  (and  of  the  tissues  produced  by  their  transformation)  diminishes  in 
proportion  to  the  prolongation  of  the  general  life  of  the  system ;  and  this  law 
exactly  corresponds  with  what  has  just  been  observed,  as  to  the  comparison 
of  the  tissues  of  different  kinds,  which  are  present  in  the  same  body. 

5. — Of  Death,  or  Cessation  of  Nutrition. 

813.  It  is  a  necessary  consequence  of  that  intimate  mutual  dependence  of 
the  several  operations,  which  is  characteristic  of  the  higher  organisms,  that 
the  interruption  of  the  function  of  any  one  important  part  is  followed  by  the 
Death  of  the  whole  structure;  because  it  interferes  with  the  elaboration,  cir- 
culation, or  depuration  of  that  nutritive  fluid,  which  supplies  the  pabulum  for 
the  growth  and  reproduction  of  each  portion  of  the  system.     But  the  lives 
of  individual  parts  may  be  prolonged  for  a  greater  or  less  duration,  after  the 
suspension  of  the  regular  series  of  their  combined  operations;   hence  it  is 
that  Molecular  Death  is  not  always  an  immediate  result  of  Somatic  Death. — 
But,  on  the  other  hand,  if  the  function  of  the  part  have  no  immediate  relation 
to  the  indispensable  actions  just  alluded  to,  it  may  cease  without  affecting 
them;  so  that  Molecular  death  may  take  place  to  a  considerable  extent  (as  in 
entire  limbs,  or  in  the  muscles  and  integuments  of  the  head  and  trunk)  with- 
out Somatic  death  necessarily  resulting. 

814.  The  permanent  and  complete  cessation  of  the  Circulating  current,  is 
that  which  essentially  constitutes  Somatic  Death;  and  this  may  be  traced  to 
several  distinct  causes. — In  i\\e  first  place,  it  may  be  due  to  failure  in  the  pro- 
pulsive power  of  the  Heart,  which  constitutes  Syncope;  and  this  may  result 
from  a  variety  of  causes,  which  cannot  be  here  particularized. — Secondly,  it 
may  be  occasioned  by  an  obstruction  to  the  flow  of  blood  through  the  capil- 
laries of  the  lungs,  constituting  Asphyxia;  and  this,  as  we  have  seen,  may 
be  consequent  upon  disordered  states  of  the  lungs  themselves,  or  upon  sus- 
pension of  the  respiratory  movements,  through  affections  of  the  Nervous 
centres.     It  is  in  this  mode  that  most  fatal  disorders  of  the  Nervous  System 
produce  death;  except  when  a  sudden  and  violent  impression  (as  from  con- 
cussion of  the  brain,  or  a  blow  on  the  epigastrium)  occasions  a  cessation  of 
the  heart's  power.    Thus  in  Apoplexy,  Narcotic  Poisoning,  &c.,  death  results 
from  the  paralyzed  condition  of  the  Medulla  Oblongata ;  whilst  in  the  con- 
vulsive diseases,  the  fatal  result  ensues  upon   a  spasmodic  fixation  of  the 
respiratory  muscles. —  Thirdly,  Somatic  death  may  be  occasioned  by  a  dis- 
ordered condition  of  the  Blood  itself,  which  at  the  same  time  weakens  the 
power  of  the  Heart,  impairs  the  activity  of  the  Nervous  system,  and  prevents 
the  performance  of  those  changes  in  the  systemic  capillaries,  which  afford  a 
powerful  auxiliary  to  the  circulation.   This  is  Death  by  Necrsemia. — Fourthly, 
Somatic  death  may  result  directly  from  the  agency  of  Cold,  which  stagnates 
all  the  vital  operations  of  the  system.  Where  the  cooling  is  due  to  the  agency 
of  an  extremely  low  external  temperature,  which  acts  first  upon  the  super- 
ficial parts,  there  is  reason  to  think  that  the  congestion  of  the  internal  vessels 
thereby  induced,  occasions  a  torpid  condition  of  the  nervous  centres,  and  that 
the  cessation  of  the  Circulation  is  immediately  due  to  Asphyxia.     But  when 
the  cooling  is  gradual,  and  the  loss  of  heat  is  nearly  equally  rapid  throughout, 
it  is  obvious  that  the  stagnation  will  be  universal,  and  that  no  cessation  of 
activity  in  any  one  part  is  the  occasion  of  the  stagnation  in  the  functions  of 
the  remainder.     It  is  in  this  manner  that  death  results  from  Starvation ;  and 
not  by  the  weakening  of  the  heart's  action,  as  commonly  supposed.     The 
proofs  of  this  will  be  stated  hereafter  (§  896). 

815.  That  Molecular  death  should  speedily  follow  Somatic  death,  is  not 
surprising;  when  it  is  borne  in  mind  how  constant  is  the  dependence  of  all 


OF  DEATH,  OR  CESSATION  OF  NUTRITION.  613 

those  functional  operations,  in  which  vital  activity  consists,  upon  the  due 
supply  of  the  circulating  fluid.  And  as  a  general  rule  we  find,  that  the  more 
active  the  changes  which  normally  take  place  in  any  tissue  during  life,  the 
more  speedily  is  its  complete  loss  of  activity,  or  Death,  when  the  requisite 
conditions  of  its  vital  action  are  no  longer  supplied  to  it.  We  may  observe 
that,  in  Cold-blooded  animals,  the  supervention  of  Molecular  upon  Somatic 
death  is  much  less  speedy  than  it  is  in  Birds  and  Mammals.  This  seems 
due  to  two  causes.  In  the  first  place,  the  tissues  of  the  former,  being  at  all 
times  possessed  of  a  lower  degree  of  vital  activity  than  those  of  the  latter, 
are  disposed  to  retain  it  for  a  longer  time ;  according  to  the  principle  already 
laid  down.  And,  secondly,  as  the  maintenance  of  a  high  temperature  is  an 
essential  condition  of  the  vital  activity  of  the  tissues  of  warm-blooded  ani- 
mals, the  rapid  cooling  of  the  body  after  Somatic  death  is  calculated  to  extin- 
guish it  speedily;  and  that  this  cause  has  a  real  operation,  is  evinced  by  the 
influence  of  artificial  warmth  in  sustaining  the  vital  properties  of  separated 
parts. — The  rapidity  with  which  Molecular  death  follows  the  cessation  of  the 
general  circulation,  will  be  influenced  by  a  variety  of  causes ;  but  especially 
by  the  degree  in  which  the  condition  of  the  solids  and  fluids  of  the  body  has 
been  impaired  by  the  mode  of  death.  Thus  in  Necraemia,  and  in  death  by 
gradual  -cooling,  Molecular  and  Somatic  death  may  be  said  to  be  simultane- 
ous ;  and  the  same  appears  to  be  true  of  death  by  sudden  and  violent  impres- 
sions on  the  Nervous  System.  But  in  many  cases  of  death  by  causes,  which 
suddenly  operate  in  producing  Syncope  or  Asphyxia,  the  tissues  and  blood 
having  been  previously  in  a  healthy  condition,  Molecular  death  may  be  long 
postponed.  We  cannot  be  quite  certain  that  it  has  supervened,  until  signs  of 
actual  decomposition  present  themselves. 

816.  When  Molecular  death  takes  place  in  an  isolated  part,  it  must  result 
from  some  condition  peculiar  to  that  part,  and  not  primarily  affecting  the 
body  in  general.     Thus  we  may  have  Gangrene  or  Mortification  of  a  limb  as 
a  direct  result  of  the  application  of  severe  cold,  or  of  an  agent  capable  of 
producing  chemical  changes  in  its  substance,  or  of  violent  contusions  occa- 
sioning mechanical  injury;  or,  again,  from  an  interruption  to  the  current  of 
nutritive  fluid;  or,  further,  from  some  ill-understood  stagnation  of  the  nutri- 
tive process,  which  manifests  itself  in  the  spontaneous  death  of  the  tissues 
without  any  assignable  cause,  as  in  some  cases  of  Senile  Gangrene.     Some- 
times we  are  enabled  to  trace  this  stagnation  to  some  disordered  condition  of 
the  circulating  fluid;  as  in  the  Gangrene  resulting  from  the  continued  use  of 
the  Ergot  of  Rye  or  Wheat;  but  we  can  give  no  other  account  of  the  almost 
invariable  commencement  of  such  gangrene  in  the  extremities,  than  we  can 
of  the  selection  of  Lead,  introduced  into  the  blood,  by  the  extensors  of  the 
fore-arm. — When  Mortification  or  Molecular  Death  is  once  established  in  any 
part,  it  tends  to  spread,  both  to  contiguous  and  to  distant  portions  of  the  body. 
— Thus  we  have  continually  to  witness  the  extension  of  Gangrene  of  the 
lower  extremities,  resulting  from  severe  injury  or  from  the  use  of  the  Ergot, 
from  the  small  part  first  affected,  until  the  whole  limb  is  involved ;  and  this 
extension  is  easily  accounted  for  by  our  knowledge  of  the  tendency  of  organic 
substances  in  the  act  of  decomposition,  to  produce  a  similar  change  in  other 
organic  substances  subjected  to  their  influence.     And  the  propagation  of  the 
Gangrenous  tendency  to  other  parts,  is  obviously  due  to  the  perversion  of  the 
qualities  of  the  Blood,  which  results  from  a  similar  cause.     It  is  not,  how- 
ever, until  some  organ  is  affected,  whose  action  is  essential  to  the  due  main- 
tenance of  the  Vegetative  functions,  that  Molecular  death  becomes  a  cause  of 
Somatic  death ;  and  very  extensive  ravages  may  thus  take  place  without  the 
extinction  of  the  sufferer's  life. 
52 


614  OF  SECRETION. 


CHAPTER    XV. 

OF  SECRETION. 

1. — Of  Secretion  in  General. 

817.  The  literal  meaning  of  the  term  Secretion  is  separation;  and  this  is 
nearly  its  true  acceptation  in  Physiology.     We  have  seen  that  the  Nutritive 
materials,  which  are  received  into  the  living  body,  are  combined  in  a  certain 
proportion  in  the  circulating  fluid;  and  that  they  are  carried  in  its  current  to 
every  part  of  the  structure.     Of  the  elements  of  the  Blood,  some  are  being 
continually  separated  from  it,  to  be  introduced  into  the  solid  textures,  of  which 
they  become  constituents ;  forming,  as  it  were,  the  organized  frame-work,  in 
the  interstices  of  which  various  other  matters  (also  separated  from  the  blood) 
are  deposited  in  an  inorganic  condition.      This  separation,  the  object  of  which 
is  to  build  up  a  living  fabric,  has  been  already  considered  under  the  head  of 
Nutrition;  but  it  may  be  here  remarked,  that  the  deposition  of  Calcareous 
matter  in  the  Bones  and  Teeth,  of  Chondrine  and  Gelatine  in  the  Bones  and 
Cartilages,  and  of  Horny  matter  in  the  cells  of  the  Epithelium  and  its  ap- 
pendages (Hair,  Nails,  Hoofs,  &c.),  is  accomplished  by  a  process  analogous 
in  all  respects  to  that  concerned  in  the  separation  of  those  other  products 
which  are  ordinarily  considered  as  Secretions.     The  same  may  be  said  of  the 
Serous  fluid,  which  distends  the  interspaces  of  Areolar  tissue,  the  Oily  matter 
contained  in  the  Fat-cells,  the  Albuminous  fluid  of  the  Humours  of  the  Eye, 
and  other  analogous  constituents  of  the  living  fabric. 

818.  But  we  have  chiefly  to  consider  under  the  present  head,  the  nature 
and  origin  of  those  products  which  are  continually  being  cast  forth  from  the 
living  body ;  the  amount  of  which  is  usually  equal,  in  the  .adult  animal,  to 
that  of  the  solids  and  fluids  ingested,  after  allowance  has  been  made  for  the 
portion  rejected,  in  the  form  of  faeces,  as  indigestible.     The  experiments  of 
Dr.  Dalton*  on  his  own  person,  give  the  following  as  the  proportional  quan- 
tities discharged  through  the  principal  channels   of  excretion.     The  mean 
quantity  of  solid  and  liquid  Aliment  taken  into  the  system  daily  (during  14 
days  in  spring)  being  91  oz.,  or  about  5|  Ibs.,  the  average  amount  of  Faeces 
(including  part  of  the  solid  matter  of  the  bile)  was  5  oz. ;  the  average  amount 
of  Urine  was  48£  oz.  daily ;  and,  as  the  total  weight  of  the  body  remained 
the  same,  the  quantity  of  fluid  and  solid  matter  excreted  by  the  Skin  and  the 
Lungs  must  have  been  37k  oz.     At  other  periods  of  the  year,  a  variation  was 
observed  ;  especially  in  the  relative  amount  of  fluid  passing  off  by  the  Urine, 
and  by  Cutaneous  exhalation. 

819.  It  can  scarcely  be  questioned,  that  the  chief  source  of  the  Excretions 
is  to  be  found  in  the  continued  Decomposition  of  the  various  tissues  of  the 
body,  which  has  been  several  times  alluded  to  (§§  275  and  811) ;  and  it  is  pro- 
bable, from  considerations  heretofore  adduced,  that  they  are  derived,  not  so 
much  from  the  fluid  returned  into  the  blood  by  the  Lymphatics  (as  formerly 
supposed),  as  from  the  Blood  itself  (§  680).     It  has  been  pointed  out  by  Lie- 
big,  that  there  is  a  remarkable  correspondence  between  the  elements  of  the 
Blood,  and  those  of  the  Bile  and  Urine  taken  together ;  so  that  the  Tissues, 

*  Edinburgh  New  Philosophical  Journal,  1832,  1833. 


OF  SECRETION  IN  GENERAL.  615 

which  are  all  formed  from  the  nutritive  fluid,  may  be  regarded  as  resolving 
themselves,  by  their  ultimate  decomposition,  into  these  two  excretions. 
Moreover,  the*  Blood,  during  its  circulation,  gives  up  one  portion  of  its  con- 
stituents in  one  part  of  the  body — -another  at  a  different  situation, — and  so  on. 
Thus,  the  elaboration  of  Gelatine,  which  is  deposited  so  largely  in  the  solid 
tissues,  must  occasion  a  considerable  alteration  in  the  blood :  since,  in  its  pro- 
duction from  Albumen,  a  certain  residuum  must  be  left  (§  141,  6,  c).  This 
residuum  is  probably  another  important  source  of  the  products  of  Excretion. 
The  same  may  be  remarked  in  regard  to  the  Nutrition  of  the  Nervous  Sys- 
tem (§  249).  In  several  other  instances,  peculiarities  of  action  in  different 
parts  will  deprive  the  Blood  that  passes  through  them,  of  its  due  proportion 
of  certain  of  its  constituents  ;  these  are  partly  restored  by  its  admixture  in 
the  Heart,  with  the  Blood  that  has  returned  from  other  parts ;  but  still  a  gene- 
ral alteration  in  the  character  of  the  Blood  is  the  result  of  its  Circulation  ;  and 
for  this  alteration,  it  is  the  province  of  the  Excretory  function  to  compensate. 
A  striking  illustration  may  be  found,  in  the  change  of  the  colour,  and  of  the 
proportional  amount  of  free  Oxygen  and  Carbonic  Acid,  which  takes  place 
in  the  Systemic  capillaries,  and  which  is  reversed  in  the  passage  of  the  Blood 
through  the  Lungs  (§  766). — Moreover  it  appears  that  two,  at  least,  of  the 
Excreting  organs  have  for  their  function  to  prevent  the  accumulation,  in  the 
Blood,  of  matters  which  have  been  taken  in  as  food,  but  for  which  there  is 
no  demand  in  the  economy.  Thus  the  Liver  appears  to  be  the  peculiar 
channel  for  the  elimination  of  superfluous  non-azotized  matter  (§  833)  ;  and 
the  Kidney  of  these  azotized  compounds,  which  cannot  be  worked  up  (so 
to  speak)  into  tissue  (§  842).  Particular  sources  for  the  respective  contents 
of  other  Excretions  will  be  pointed  out,  when  they  are  considered  in  detail. 

820.  A  distinction  has  already  been  drawn  (§  278)  between  the  proper 
Excretions,  the  retention  of  which  in  the  Blood  would  be  positively  injurious, 
and  those  Secretions  which  are  destined  for  particular  purposes  within  ihe 
system,  and  the  cessation  of  which  has  no  immediate  influence  on  any  but  the 
function  to  which  they  are  destined.  This  distinction  is  one  of  great  import- 
ance, especially  when  it  is  considered  with  reference  to  the  Chemical  Elements, 
that  are  found  in  the  two  classes  of  fluids  respectively.  The  solid  matter  dis- 
solved in  those  of  the  latter  class,  is  little  else  than  a  portion  of  the  constitu- 
ents of  the  Blood,  either  pure,  or  but  slightly  altered  ;  thus,  in  the  Lachrymal 
fluid,  the  Saliva,  the  Pancreatic  juice,  the  Serous  fluid  of  areolar  tissue  and 
of  serous  and  synovial  membranes,  we  find  little  else  than  Albuminous  and 
Saline  matter,  derived  at  once  from  the  blood.  The  Caseine,  which  is  the 
most  characteristic  ingredient  of  Milk  (§  854  6),  is  but  a  slightly-altered  form 
of  Albumen;  and  some  curious  evidence  has  recently  been  obtained,  that  this 
alteration  commences  in  the  Blood,  and  goes  on  during  pregnancy  as  a  pre- 
paration for  lactation.*  On  the  other  hand,  the  characteristic  ingredients  of  the 
Excretions  are  very  different  in  character  from  the  normal  elements  of  the 
Blood.  They  are  all  of  them  completely  unorganizable;  and  they  possess, 
for  the  most  part,  a  simple  atomic  constitution.  Some  of  them  also,  have  a 
tendency  to  assume  a  crystalline  form  ;  which  is  considered  by  Dr.  Prout  to 
indicate  their  unfitness  to  enter  into  the  composition  of  organized  tissues. 
With  regard  to  some  of  the  chief  of  these,  there  is  sufficient  evidence  of  their 
existence,  in  small  quantity,  in  the  circulating  Blood;  but  it  is  also  clear,  that 
they  exist  there  as  products  of  decomposition,  and  that  they  are  destined  to 
be  separated  from  it  as  speedily  as  possible.  If  their  separation  be  prevented, 
they  accumulate,  and  communicate  to  the  circulating  fluid  a  positively  delete- 
rious character.  Of  this,  we  have  already  seen  a  striking  example  in  the 

*  See  Dr.  G.  Bird,  in  Guy's  Hospital  Reports,  vol.  v. 


616  OF  SECRETION. 

case  of  Asphyxia  (§  779) ;  and  the  history  of  the  other  two  principal  Excre- 
tions, the  Bile  and  Urine,  will  furnish  evidence  to  the  same  effect. — As  a 
general  fact,  then,  it  may  be  stated,  that  the  materials  of  the  Secretions  pre- 
exist in  the  Blood,  in  a  state  nearly  resembling  that  in  which  they  are  thrown 
off  by  the  secreting  organs :  but  that  the  materials  of  those  secretions,  which 
are  only  destined  to  perform  some  particular  function  in  the  economy,  are 
derived  from  the  substances  which  are  appropriated  to  its  general  purposes ; 
whilst  those  of  the  excretions  are  the  result  of  the  changes  that  have  taken 
place  in  the  system,  and  cannot  be  retained  in  it  without  injury. 

821.  Of  the  reason  why  certain  compounds  forming  part  of  the  circulating 
Blood,  are  separated  from  it  by  one  organ,  and  others  by  a  different  one,  no 
other  account  can  be  given,  than  that  which  refers  them  to  the  special  endow- 
ments of  the  ce//5,  which  are  the  real  instruments  of  the  process.  When  the 
ultimate  structure  of  Glands  is  considered,  it  is  found  to  be  neither  more  nor 
less  than  a  vascular  membrane,  covered  with  epithelium-cells,  and  made  up 
into  various  forms  for  convenience  of  packing.  Of  such  a  membrane,  in  its 
most  expanded  state,  that  which  composes  the  walls  of  the  Serous  cavities,  or 
of  the  Synovial  capsules,  affords  a  good  example.  Of  Mucous  membrane 
(§  178),  the  structure  is  in  some  instances  almost  equally  simple  ;  but  in  gene- 
ral the  secreting  surface  is  extended,  by  the  inversion  of  the  membrane,  into 
a  large  number  of  little  open  sacs  or  follicles  (Fig.  45),  which  are  lined  with 
epithelium-cells,  and  copiously  supplied  with  blood-vessels,  and  which  are 
equally"  concerned  with  the  external  superficies,  in  the  elaboration  of  the  pro- 
tective secretion  that  covers  these  membranes.  In  the  most  complex  form  of 
gland,  we  find  nothing  but  a  very  obvious  modification  of  this  structure. 
Either  the  sacs  are  prolonged  into  coeca  or  blind  tubes,  as  is  the  case  in  the 
Human  Kidney  or  Testis ;  or  they  are  very  greatly  multiplied,  and  are  clus- 
tered together  (just  like  currants  upon  a  stalk)  upon  efferent  ducts  common  to 
several  of  them,  as  is  seen  in  the  Parotid.  Now,  that  the  particular  modifica- 
tion of  structure,  which  the  Gland  may  present,  has  no  essential  connection 
with  the  character  of  the  Secretion  it  is  destined  to  form,  is  evident  from  this 
circumstance, — that  almost  every  gland  may  be  found  under  a  variety  of  .forms, 
in  different  parts  of  the  Animal  series.  The  Secreting  system,  like  every 
other,  is  far  simpler  in  the  lower  classes  of  Animals  than  in  the  higher;  the 
number  of  effete  compounds,  to  be  excreted  from  the  circulating  fluid,  is  much 
smaller;  and  the  variety  of  purposes,  for  which  special  secretions  are  required, 
is  much  less.  Hence,  for  almost  every  Gland,  there  is  a  part  of  the  Animal 
scale  below  which  it  does  not  exist ;  and  when  it  makes  its  first  appearance, 
it  almost  invariably  presents  a  character  nearly  as  simple,  as  that  of  the  least 
complex  glanular  structures  in  the  higher  animals.  Thus  the  Pancreas  in 
Fishes  (Fig.  257),  the  Mammary  Gland  in  the  Ornithorhyncus  (Fig.  222),  the 

Salivary  glands  in  the  Echinodermata, 

Fig.  222.  and  the  Urinary  organs  of  Insects,  are 

nothing  more  than  follicles  more  or  less 
extended,  and  having  separate  orifices. 
Again,  in  Insects,  we  find  that  all  the 
glands, — the  Liver  and  Salivary  glands, 
as  well  as  the  Kidneys  and  Testes, 
— have  the  form  of  prolonged  tubes ; 

whilst  in  Mollusca,  all  the  secret- 
Mammary  Gland  of  Ornithorhyncus,  ing  organs, — the  Urinary  and  Genital, 

as  well  as  the  Biliary  and  Salivary, — 

consist  of  multiplied  vesicles  connected  with  a  ramifying  duct.  Moreover,  it 
is  a  well-ascertained  fact  that,  even  in  the  highest  organisms,  the  functions  of 
Glandular  structures  (especially  of  those  concerned  in  Excretion)  are  to  a 


OF  SECRETION  IN  GENERAL.  617 

certain  degree  vicarious  with  each  other  ;  so  that,  when  the  secretion  from  one 
of  them  is  checked,  the  system  makes  an  effort  to  throw  off,  by  another  chan- 
nel, the  injurious  products  that  would  otherwise  accumulate  in  the  Blood. 
What  is  the  nature  of  the  change  in  any  secreting  organ,  that  causes  it  thus  to 
take  upon  itself  a  new  function,  is  a  question  upon  which  we  can  at  present 
only  speculate ;  we  have  no  more  certain  knowledge  of  it,  than  we  have  of 
the  cause  which  occasions  their  normal  actions. 

822.  It  has  been  recently  proved,  beyond  all  reasonable  doubt,  that  in  all 
secreting  organs,  the  Cells  which  cover  the  membranous  surfaces,  and  line  the 
follicles  and  tubes,  constitute  the  really  operative  part.     The  simplest  condi- 
tion of  a  Secreting  Cell,  in  the  Animal  Body,  is  that  in  which  it  exists  in  Adi- 
pose tissue  ;  every  cell  of  which  possesses  the  power  of  secreting  or  separat- 
ing Fatty  matter  from  the  Blood.     In  this  case,  the  secreted  product  remains 
stored  up  in  the  cavity  of  the  cell,  as  it  usually  does  in  the  Cellular  tissue  of 
Plants  ; — not  being  poured  forth,  as  it  generally  is  elsewhere,  by  the  subse- 
quent bursting  or  liquefaction  of  the  cell.     But  when  the  Secreting  Cells  are 
disposed  on  the  surface  of  a  membrane,  instead  of  being  aggregated  in  a  mass, 
it  is  obvious  that,  if  they  burst  or  dissolve  away,  their  contents  will  be  poured 
into  the  cavity  bounded  by  that  membrane  ;  and  this  is  the  case  in  the  ordinary 
Secreting  processes.     Thus  the  Mucus,  which  covers  the  surface  of  the  Mu- 
cous membranes,  and  which  is  being  continually  renewed,  is  the  product  of 
the  elaboration  performed  by  the  Epithelium-cells,  which  cover  their -free  sur- 
faces, and  line  their  follicles.     These  cells  are  being  continually  cast  off,  and 
replaced  by  a  fresh  growth,  which  has  its  origin  in  germs  supplied  by  the 
subjacent  membrane  ;  and  thus  it  is  by  the  act  of  Cell-growth,  that  the  Secret- 
ing process  is  accomplished.     For  just  as  the  cells  at  the  extremities  of  the 
Intestinal  Villi  select,  from  the  contents  of  the  alimentary  tube,  the  nutritious 
portion  which  is  to  be  introduced  into  the  absorbent  vessels, — so  do  the  cells 
of  the  Secreting  Tubuli  or  Follicles  select  from  the  Blood  those  effete  particles 
which  it  is  their  peculiar  province  to  assimilate,  and  then  discharge  them  into 
the  canals  by  which  they  will  be  carried  out  of  the  system.*     Hence,  as  Mr. 
Goodsir  justly  remarks,  "  there  are  not,  as  has  been  hitherto  supposed,  two 
vital  processes  going  on  at  the  same  time,  viz.,  growth  and  secretion;  but 
only  one,  viz.,  growth.     The  only  difference  between  this  kind  of  growth, 
and  that  which  occurs  in  other  organs  is,  that  a  portion  of  the  product  is,  from 
the  anatomical  condition  of  the  part,  thrown  out  of  the  system." 

823.  From  the   study  of  the  changes  which  take  place  in  the  Glandular 
organs,  during  their  first  development  and  their  continued  activity,  Mr.  Good- 
sir  has  arrived  at  the  conclusion,  that  the  follicles  may  be  considered  as  pa- 
rent-cells ;  and  that  the  secreting  cells  in  their  interior  may  be  regarded  as  a 
second  generation,  developed  from  the  nuclei  or  germinal  spots  on  the  walls 
of  the  first.     Now  the  successive  production  and  development  of  the  latter, 
in  which  the  process  of  secretion  essentially  consists,  may  take  place  on  two 
different  plans. 

a.  In  one  class  of  Glands,  the  parent-cell,  having  begun  to  develope  new  cells  in  its  inte- 
rior, gives  way  at  one  point,  and  bursts  into  the  excretory  duct,  so  as  to  become  an  open  fol- 
licle, instead  of  a  closed  cell;  its  contained  or  secondary  cells,  in  the  progress  of  their  own 
growth,  draw  into  themselves  the  matters  to  be  eliminated  from  the  blood,  and,  having  at- 
tained their  full  term  of  life,  burst  or  liquefy,  so  as  to  discharge  their  contents  into  the  cavity 
of  the  follicle,  whence  they  pass  by  its  open  orifice  into  the  excretory  duct;  and  a  continual 
new  production  of  secondary  cells  takes  place  from  the  germinal  spot  or  nucleus  at  the  ex- 
tremity of  the  follicle,  which  is  here  a  permanent  structure.  In  this  form  of  gland,  we  may 
frequently  observe  the  secreting  cells  existing  in  various  stages  of  development,  within  a 


*  We  shall  hereafter  meet  with  an  instance  (§  829)  in  which,  from  the  position  of  the 
cells  secreting  it,  Adipose  matter  is  discharged  from  the  body  as  an  Excretion. 

52* 


618  OF  SECRETION. 

single  follicle ;  their  size  increasing,  and  the  character  of  their  contents  becoming  more  dis- 
tinct, in  proportion  to  their  distance  from  the  germinal  spot  (which  is  at  the  blind  termina- 
tion of  the  follicle),  and  their  consequent  proximity  to  the  outlet  (Fig.  41).  In  some  varieties 
<  >f  such  glands,  however,  especially  when  the  follicles  are  extended  into  prolonged  tubes,  the 
production  of  new  cells  does  not  take  place  from  a  single  germinal  spot  at  the  extremity  of 
tfye  follicle,  but  from  a  number  of  points  scattered  through  its  entire  length. 

b.  In  the  second  type  of  Glandular  structures,  the  parent-cell  does  not  remain  as  a  perma- 
nent follicle;  but,  having  come  to  maturity,  and  formed  a  connection  with  the  excretory 
duct,  it  discharges  its  entire  contents  into  the  latter,  and  then  shrivels  up  and  disappears,  to 
be  replaced  by  newly-developed  follicles.     In  each  parent-cell  of  a  gland  formed  upon  this 
type,  we  shall  find  all  its  secondary  or  secreting  cells  at  nearly  the  same  grade  of  develop- 
ment ;  but  the  several  parent-cells,  of  which  the  parenchyma  of  the  gland  is  composed,  are 
in  very  different  stages  of  growth  at  any  one  period — some  having  discharged  their  contents, 
and  being  in  progress  of  disappearance,  whilst  others  are  just  arriving  at  maturity,  and  con- 
necting themselves  with  the  excretory  duct;  others  exhibiting  an  earlier  degree  of  develop- 
ment in  the  secondary  cells ;  others  presenting  the  latter  in  their  incipient  condition ;  whilst 
others  are  themselves  just  starting  into  existence,  and  as  yet  exhibit  no  traces  of  the  second 
generation,  which  they  are  destined  subsequently  to  develope. 

c.  The  former  of  these  seems  to  be  the  usual  type  of  the  ordinary  glands;  the  latter  is 
chiefly,  if  not  entirely,  to  be  met  with  among  the  Spermatic  Glands.* 

824.  It  is  important  to  bear  in  mind,  that  an  essential  difference  exists  be- 
tween the  vital  power  concerned  in  the  true  Secreting  process,  and  the  phy- 
sical property  which  occasions  fluid  Exhalation  or  Transudation.     This  dif- 
ference is  precisely  the  same  as  that  which  exists  between  the  vital  act  of 
Selective  Absorption,  and  the  physical  operation  of  Endosmose  or  Imbibition. 
By  Imbibition  and  Transudation,  certain  fluids   may  pass   through  organic 
membranes,  in  the  dead  as  well  as  in  the  living  body;  and  this  passage  de- 
pends merely  upon  the  physical  condition  of  the  part,  in  regard  to  the  amount 
and  the   nature  of  the  fluid  it  contains,  and  the  permeability  of  its  tissues. 
Not  only  does  water  thus  transude,  but  various  substances  that  are  held  in 
complete   solution  in  it,  especially  albumen  and  saline  matter :  it  is  in  this 
manner  that  the  Blood  absorbs  fluids  from  the  digestive  cavity  (§  675),  and 
pours  out  the  serous  fluid  which  occupies  the  interspaces  of  the  areolar  tissue 
and  the  serous  cavities.     The  transudation  of  the  watery  portion  of  the  blood 
is  much  increased  by  any  impediment  to  its  flow  through  the  vessels,  as  in 
Congestion  and  Inflammation;  and  also  by  any  causes  that  produce  a  dimi- 
nished resistance  in   their  walls. — We  shall  hereafter  see,  in  examining  the 
Physiology  of  the  Urinary  secretion,  a  very  striking  example  of  the  contrast 
between  physical  Transudation  and  vital  Secretion  (§  840). 

2. — The  Liver. — Secretion  of  Bile. 

825.  The  Liver  is   probably  more  universally  found,  throughout  the  Ani- 
mal scale,  than  any  other  gland.     Its  form  varies  so  greatly,  however,  in  dif- 
ferent tribes,  that,  without  a  knowledge  of  its  essential  structure,  we  should  be 
disposed  to    question  whether  any  identity  of  character  exists   amongst  the 
several  organs  which  we  include  under  this  designation. 

a.  In  the  higher  Polypes,  for  example,  we  find  it  to  consist  of  a  number  of  distinct  folli- 
cles, lodged  within  the  walls  of  the  stomach,  and  pouring  their  secretion  into  its  cavity  by 
as  many  separate  orifices ;  and  it  is  more  by  the  peculiar  character  of  their  secretion,  than 
by  any  other  distinction,  that  these  follicles  are  recognized  as  Hepatic. — In  the  lower  Articu- 
late, a  very  similar  conformation  is  met  with  ;  but  in  the  higher  classes  of  this  series,  such 
as  Insects,  the  follicles  are  prolonged  into  tubes  of  considerable  extent.  It  is  very  curious 
to  observe,  in  animals  of  such  complex  structure,  that  a  few  long  tubes,  closed  at  one  end, 
and  opening  at  the  other  into  the  alimentary  canal,  are  all  which  they  have  to  represent  a 
Liver ;  but  the  wonder  is  readily  accounted  for  by  keeping  in  view  the  extremely  active 

*  See  Goodsir's  Anatomical  and  Pathological  Researches,  Chap.  v. 


THE  LIVER — SECRETION  OF  BILE.  619 

Respiration  of  these  beings,  which  renders  unnecessary  any  other  complex  apparatus  for  ela- 
borating carbon  from  the  system. 

6.  On  the  other  hand,  among  the  Mollusca,  the  Liver  attains  a  much  greater  development. 
Instead  of  the  follicles  being  prolonged  into  tubes  (which  is  the  usual  form  of  the  glandular 
system  in  Insects),  they  are  very  much  increased  in  number,  and  arranged  on  the  sides  of 
canals  or  efferent  ducts,  which  either  separately  pour  their  fluid  into  the  intestine,  or  partially 
unite  with  each  other  before  doing  so.  The  Liver  thus  acquires  a  lobulated  character,  each 
lobe  consisting  of  a  duct  with  its  branching  follicles ;  and  the  whole  organ  forms  a  consider- 
able proportion  of  the  mass  of  the  viscera,  and  is  evidently  of  great  importance  in  the 
economy  of  the  animal. — It  as  interesting  to  compare  this  complex  structure  with  the  very 
simple  condition  presented  by  the  Liver  in  insects ;  arid,  when  we  keep  in  view  the  relative 
amount  of  Respiration  in  the  two  groups  of  animals,  we  are  at  once  struck  with  the  fact, 
that  the  development  of  the  Liver  bears  an  inverse  proportion  to  the  opportunity  afforded 
by  the  Respiratory  organs  for  the  aeration  of  the  blood;  it  being  peculiarly  extended,  when 
these,  either  from  their  small  size,  or  from  their  employment  in  an  aquatic  medium,  cannot 
perform  their  function  with  great  activity.  This  conclusion  is  confirmed  in  an  interesting 
manner  by  the  fact,  that  the  Crustacea,  which  have  the  general  organization  of  Insects,  but 
which  inhabit  the  water  and  breathe  by  gills  instead  of  by  a  complex  system  of  air-tubes, 

Fig.  223.  Fig.  224. 


Lobule  of  Liver  of  Squilla  Mantis ;  exterior.  Lobule  of  Liver  of  Squilla  Mantis  cut  open. 

possess  a  Liver  corresponding  in  form  and  in  degree  of  development  with  that  of  the 
Mollusca.  4| 

c.  In  the  Vertebrated  Sub-kingdom,  we  may  trace  the  operation  of  the  same  principle; 
but  the  internal  structure  of  the  Liver,  in  the  adult  condition  at  least,  is  less  easily  demon- 
strated, than  it  is  in  the  lower  classes ;  owing  to  its  increased  complexity  of  structure,  and 
the  closer  union  between  its  different  parts.  In  Fishes  and  Reptiles,  the  Liver  is  of  consider- 
able size,  and  seems  to  perform  a  very  important  part  in  the  decarbonization  of  the  blood : 
its  form  is  adapted  to  that  of  the  cavity  in  which  it  is  lodged,  sometimes  one  lobe  only  being 
developed.  In  Birds,  on  the  other  hand,  whose  respiration  is  so  much  more  active,  it  is  much 
smaller,  but  is  placed  on  the  median  line,  in  conformity  with  the  general  symmetry  of  their 
internal  as  well  as  external  organs  (§  40).  In  Mammalia,  also,  it  is  comparatively  small ; 
but,  though  reduced  in  proportional  size,  it  is  at  the  same  time  much  more  compact  and 
firm  than  in  the  lower  Vertebrata. 

rf.  The  Liver  of  Man  is  much  less  developed  than  that  of  many  other  Mammalia;  and 
presents,  as  rudimentary  indications,  certain  organs  which  are  elsewhere  fully  developed. 
The  whole  mass,  which  we  are  accustomed  to  describe  as  consisting  of  a  right  and  left  lobe, 
does  in  reality  form  but  one  (there  being  no  real  division  between  its  two  portions),  which 
must  be  regarded  as  the  Central  lobe ;  the  Lobulus  Spigelii  is  the  rudiment  of  a  second  or 
right  lobe,  and  the  Lobulus  Caudatus  is  a  Lobule  developed  from  it.  In  the  Carnivora  and 
Rodentia,  which  present  the  most  complex  form  of  Liver  that  we  meet  with  among  Mam- 
malia, there  are  five  distinct  parts ; — a  central  or  principal  lobe,  corresponding  with  the 
principal  part  of  the  liver  of  Man;  a  right  lateral  lobe  with  a  lobular  appendage,  correspond- 
ing to  the  Lobulus  Spigelii  and  Lobulus  Caudatus ;  and  a  similar  lobe  and  lobule  on  the  left 
side. 

e.  The  Gall-bladder  is  an  appendage  to  the  Liver,  of  which  we  find  no  traces  in  the 
Invertebrata.  It  may  be  regarded  as  simply  a  dilatation  of  the  efferent  duct,  more  or  less 
prolonged  from  it,  adapted  to  store  up  the  hepatic-secretion  against  the  time  when  it  may  be 
required.  In  Fishes  it  frequently,  but  by  no  means  constantly,  presents  itself;  in  Reptiles, 
on  the  other  hand,  it  invariably  exists.  In  Birds  it  is  occasionally  absent,  even  in  species 


620 


OF  SECRETION. 

[Fig.  225. 


The  inferior  or  concave  surface  of  the  Liver,  showing  its  subdivisions  into  lobes ;  1,  centre  of  the  right 
lobe ;  2,  centre  of  the  left  lobe ;  3,  its  anterior,  inferior  or  thin  margin ;  4,  its  posterior,  thick  or  diaphragm- 
atic portion ;  5,  the  right  extremity ;  6,  the  left  extremity  ;  7,  the  notch  in  the  anterior  margin ;  8,  the 
umbilical  or  longitudinal  fissure ;  9,  the  round  ligament  or  remains  of  the  umbilical  vein ;  10,  the  portion 
of  the  suspensory  ligament  in  connection  with  the  round  ligament ;  11,  pons  hepatis,  or  band  of  liver 
across  the  umbilical  fissure ;  12,  posterior  end  of  longitudinal  fissure ;  13, 14,  attachment  of  the  obliterated 
ductus  venosus  to  the  ascending  vena  cava ;  15,  transverse  fissure  ;  16,  section  of  the  hepatic  duct;  17, 
hepatic  artery;  18,  its  branches ;  19,  venaportarum  ;  20,  its  sinus,  or  division  into  right  and  left  branches ; 
21,  fibrous  remains  of  the  ductus  venosus ;  22,  gall-bladder ;  23,  its  neck ;  24,  lobulus  quartus ;  25,  lobulus 
spigelii;  26,  lobulus  caudatus  ;  27,  inferior  vena  cava ;  28,  curvature  of  liver  to  fit  the  ascending  colon; 
29,  depression  to  fit  the  right  kidney  ;  30,  upper  portion  of  its  right  concave  surface  over  the  renal  cap- 
sule ;  31,  portion  of  liver  uncovered  by  the  peritoneum ;  32,  inferior  edge  of  the  coronary  ligament  in  the 
liver;  33,  depression  made  by  the  vertebral  column.] 

closely  allied  to  others  that  possess  it,  and  without  any  marked  difference  in  the  food,  habits, 
&c.  of  the  two.  In  Mammalia,  again,  it  is  frequently  absent,  especially  among  herbivorous 
animals;  sometimes,  on  the  other  hand,  two  are  present,  a  second  or  accessory  gall-bladder 

being  formed  upon  the  Ductus  com- 

[Fig.  226.  munis    choledochus,    which    else- 

where not  unfrequently  presents  a 
dilatation  in  the  same  situation.  In 
the  first  Giraffe  dissected  by  Mr. 
Owen,  no  gall-bladder  was  found ; 
in  the  second  there  were  two. 

/.  In  the  Human  species  the  gall- 
bladder is  rarely  absent,  except  in 
cases  of  malformation  depending 
upon  general  arrest  of  development, 
in  which  several  organs  are  in- 
volved. The  Excretory  Ducts  of 
the  Liver  and  Gall-bladder  have 
three  coats, — an  internal  or  mucous, 
a  middle  or  fibrous,  and  an  external 
or  areolar.  The  internal  coat  is  con- 
tinuous with  the  Mucous  membrane 
of  the  intestinal  tube,  into  which  it 
opens;  and  the  whole  glandular 
structure  may  indeed  be  considered 
as  a  complex  prolongation  of  this, 
copiously  supplied  with  blood-ves- 
sels, and -packed  into  the  smallest 
possible  compass.  The  middle  or 
Shows  the  three  coats  of  the  Gall-Bladder  separated  from  fibrous  coat  bears  a  considerable 
each  other ;  1,  the  external  or  peritoneal  coat;  2,  the  cellular  resemblance  in  aspect  to  that  of  the 
coat  with  its  vessels  injected ;  3,  the  mucous  coat  covered  Arteries ;  in  its  properties,  however, 
with  wrinkles ;  4,  4,  valves  formed  by  this  coat  in  the  neck  of  it  is  still  more  nearly  allied  to  true 
the  gall-bladder;  5,5,  orifices  of  the  mucous  follicles  at  this  muscle,  being  capable  of  exhibiting 
point.]  contraction  on  the  application  of 


THE  LIVER — SECRETION  OF  BILE. 


621 


stimuli  to  the  Sympathetic  nerves 
supplying  it  j  and  in  some  instances 
of  obstruction,  it  has  presented  an 
appearance  very  closely  resembling 
that  of  the  muscular  coat  .of  the 
alimentary  canal.*  Dr.  Davy  has 
pointed  out,  that  the  mucous  coat  of 
the  Ductus  communis  is  disposed  in 
valve-like  folds ;  in  such  a  manner, 
as  to  prevent  the  reflux  of  the  bile, 
or  of  the  contents  of  the  intestine. 


826.  The  Liver  may  be  re- 
garded   as   essentially  consist-       A  view  °f  the  Gall-Bladd"  distended  with  air,  and  with  its 

mff  of  a  mass  of  cells    in  con-   vessels  injected;  x'  Cy9tic  arterv '  2> the  branches  of  it  which 
iiass  01      us,  in  cor     gupply  the  peritoneai  coat  of  the  liver .  3)  the  branch  of  the 

nection  With  the  ramifications    hepatic  artery  which  goes  to  the  gall-bladder  j  4,  the  lymphatics 

of  the  Hepatic  Duct :  and  these  Of  the  gall-bladder.] 
are  in  close  relation  with  the 

ramifications  of  the  Portal  Vein  and  Hepatic  Artery,  that  serve  to  con- 
vey blood  to  the  minutest  parts  of  this  organ ;  and  with  those  of  the 
Hepatic  Vein,  which  return  it  to  the  heart,  after  it  has  been  subservient  to 
the  Nutrition  of  the  structure  and  to  the  elaboration  of  the  Secretion.  Be- 
sides these,  the  Liver  contains  Lymphatics  and  Nerves ;  the  latter  are  chiefly 
derived  from  the  Sympathetic  system,  and  are  distributed  on  the  walls  of  the 
vessels  and  ducts.  These  various  portions  of  the  structure  are  connected 
together  by  a  fibrous  tissue,  to  which  the  name  of  Glisson's  Capsule  has  been 
given.  For  our  present  knowledge  of  their  ultimate  arrangement,  we  are 
almost  entirely  indebted  to  Mr.  Kiernan,t  whose  account  of  them  will  be  here 
followed, — his  researches  having  been  confirmed,  in  all  essential  particulars, 
by  other  Anatomists. 

a.  When  a  Liver  is  closely  examined  with  the  naked  eye,  it  is  seen  to  be  made  up  of  a 
great  number  of  small  granular  bodies,  about  the  size  of  a  millet  seed,  of  an  irregular  form, 
and  presenting  a  mjjnber  of  rounded  projecting 

processes  upon  their  surfaces.  These  are  com- 
monly termed  lobules,  although  by  some  Anatomists 
they  are  spoken  of  as  acini.  When  divided  longi- 
tudinally, they  have  a  somewhat  foliated  appear- 
ance (Fig.  229),  arising  from  the  distribution  of 
the  Hepatic  Vein  ;  which,  passing  into  the  centre 
of  each  division,  is  termed  the  mfra-lobular  vein. 
The  exterior  of  each  Lobule  is  covered  by  a  pro- 
cess of  the  capsule  of  Glisson ;  which  is  very  dense 
in  the  Pig  and  other  animals ;  but  which  is  so  thin 
as  to  be  almost  undistinguishable  in  the  Human 
liver-  Its  substance  is  composed  of  the  minute 
ramifications  of  the  before-mentioned  vessels,  arranged  in  the  manner  presently  to  be  de- 
scribed ;  the  spaces  between  which  are  filled  up  with  a  parenchyma,  composed  of  nucleated 
cells,  like  those  shown  in  Fig.  232.  The  structure  of  each  lobule,  then,  gives  us  the  essential 
characters  of  the  whole  gland. 

b.  The  Lobules,  when  transversely  divided,  are  usually  found  to  present  somewhat  of  a 
pentagonal  or  a  hexagonal  shape ;  the  angles  being  generally  somewhat  rounded,  so  as  to 
form  a  series' of  passages,  or  tnter-lobular  spaces:  in  these  lie  the  branches  of  the  Vena  Portae^ 
and  of  the  Hepatic  Artery  and  Duct,  from  which  are  derived  the  plexuses  that  compose  the 
lobules.     Each  Lobule,  when  examined  with  the  microscope,  is  found  to  be  apparently  com- 
posed of  numerous  minute  bodies  of  yellowish  colour,  and  of  various  forms,  connected  to- 
gether by  vessels  ,•  to  these  the  name  of  acini  was  given  by  Malpighi;  and  to  these,  if  they 
deserve  a  name,  it  ought  to  be  restricted.     They  will  be  presently  shown,  however,  to  be 
nothing  else  than  the  irregular  islets,  left  between  the  meshes  of  the  plexus  formed  by  the 

f  ultimate  ramifications  of  the  Portal  Vein.     The  Vena  Portae,  it  will  be  recollected,  is  formed 


[Fig.  228. 


1,  Nucleated  cells  composing  the  parenchy- 
ma of  the  gland;  2,  lobules  of  human  liver 
with  ramifications  of  the  hepatic  vein.] 


*  In  the  Horse  and  Dog  this  coat  is  clearly  muscular. 
t  Philosophical  Transactions,  1833. 


622 


OF  SECRETION. 


by  the  convergence  of  the  veins,  which  return  the  blood  from  the  chylopoietic  viscera;  and 
there  is  reason  to  believe  that  it  also  receives  the  blood,  which  is  conveyed  to  the  Liver  for 


Fig.  229.  * 


Fig.  230. 


Connection  of  the  lobules  of  the  liver  with 
the  hepatic  vein;  1,  a  trunk  of  the  vein;  2,  2, 
lobules  depending  from  its  branches,  like 
leaves  on  a  tree;  the  centre  of  each  being 
occupied  by  a  venous  twig,— the  Intra-lobu- 
lar  Vein. 


Horizontal  section  of  three  superficial  lobule.?, 
showing  the  two  principal  systems  of  Blood- Ves- 
sels; 1, 1,  t'nJra-lobular  veins,  proceeding  from  the 
Hepatic  veins;  2,  2,  inter-lobular  plexus,  formed 
by  branches  of  the  Portal  veins. 


the  purposes  of  Nutrition,  by  the  Hepatic  Artery.  As  it  is  an  afferent,  not  an  efferent  ves- 
sel, it  has  a  strong  claim  to  the  character  of  an  Artery;  even  although  it  conveys  Venous 
blood.  Like  an  artery,  it  gradually  subdivides  into  smaller  and  yet  smaller  branches  ;  and 
at  last  forms  a  plexus  of  vessels,  which  lie  in  the  inter-lobular  spaces,  and  spread  with  the 
freest  inosculation,  throughout  the  entire  Liver.  To  these  vessels,  the  name  of  inier-lobular 
Veins  is  given  by  Mr.  Kiernan.  They  ramify  in  the  capsules  of  the  lobules,  covering  with 
their  ramifications  the  whole  external  surface  of  these;  and  then  enter  their  substance. 
When  they  enter  the  Lobules,  they  are  termed  lobular  veins ;  and  the  plexus  formed  by  their 
convergence,  from  the  circumference  of  each  lobule  towards  its  centre  (where  their  ultimate 
ramifications  terminate  in  those  of  the  intra-lobular  or  hepatic  vein),  is  designated  as  the 
Lobular  Venous  plexus.  In  the  islets  of  this  plexus  (the  acini  of  Malpighi)  the  ramifications 
of  the  hepatic  duct  are  distributed  in  the  manner  next  to  be  described. 

c.  The  Hepatic  duct  forms,  by  its  subdivision  and  ramification,  an  Interlobular  plexus  of  a 
very  similar  character ;  but  the  anastomosis  between  the  branches  going  to  the  different  lobules 

is  less  intimate  than  that  of  the  inter- 
Fig.  231.  lobular  veins,  and  cannot  be  directly 
demonstrated;  although  Mr.  Kiernan 
thinks  that  his  experiments  leave  but 
little  doubt  of  its  existence, — a  com- 
munication (which  cannot  be  seen  to  be 
established  by  any  nearer  channel)  be- 
ing proved  to  exist  between  the  right 
and  left  primary  subdivisions  of  the 
duct.  The  Interlobular  Ducts  ramify 
upon  the  capsular  surface  tff  the  lobules, 
with  the  branches  of  the  Portal  Vein 
and  Hepatic  Artery ;  they  then  enter  its 
substance,  and  subdivide  into  minute 
branches,  which  anastomose  with  each 
other,  and  form  a  reticulated  plexus, 
termed  by  Mr.  K.,  the  Lobular  Biliary 
plexus.  This  plexus  constitutes  the  prin- 
cipal part  of  the  substance  of  the  lobule ; 
and  when  seen  through  the  meshes  of 
the  Portal  plexus,  gives  rise  to  the  ap- 


Horizontal  section  of  two  superficial  Lobules,  show- 
ing the  interlobular  plexus  of  biliary  ducts;  1,1,  intra- 
lobular  veins  ;  2,  2,  trunks  of  biliary  ducts,  proceeding 
from  the  plexus  which  traverses  the  lobules  ;  3,  inter- 
lobular tissue ;  4,  parenchyma  of  the  lobules. 


THE  LIVER SECRETION  OF  BILE.  623 

pearance  of  ccecal  terminations  of  ducts.  The  ultimate  terminations  of  these  ducts  have 
not,  however,  been  traced  in  the  adult  Liver  of  any  of  the  higher  animals,  although  they  are 
sufficiently  evident  in  the  embryonic  condition.  From  the  analogy  of  other  organs,  there 
would  seem  good  reason  to  believe,  that  the  ultimate  ramifications  of  the  hepatic  ducts 
anastomose  freely  together,  and  that  they  form  a  network,  in  which  their  terminations  are 
lost,  as  it  were,  without  forming  true  caeca.  This  view  of  the  matter  finds  confirmation  in 
the  curious  fact  pointed  out  by  Mr.  Kiernan,  that,  in  the  kft  lateral  ligament,  the  essential 
parts  of  a  lobe  are  found  in  the  simplest  form  and  arrangement.  From  the  edge  of  the  liver 
next  to  the  ligament,  numerous  Ducts  emerge,  which  ramify  between  the  two  layers  of  peri- 
toneum of  which  the  ligament  is  composed.  They  are  accompanied  by  branches  of  the  Portal 
and  Hepatic  Veins,  and  of  the  Hepatic  Artery;  which  also  ramify  in  this  ligament,  especially 
around  the  parietes  of  the  ducts.  These  Ducts,  of  which  some  are  occasionally  of  considera- 
ble size,  divide,  subdivide,  and  anastomose  with  each  other;  and  the  meshes  formed  by  the 
network  of  larger  or  excreting  Ducts,  are  occupied  by  minute  plexuses  of  their  ultimate 
ramifications  or  secreting  Ducts. 

d.  The  Hepatic  Artery  sends  branches  to  every  part  of  the  Liver,  supplying  the  walls  of 
the  Portal  and  Hepatic  Veins,  and  of  the  Hepatic  Ducts,  as  well  as  Glisson's  capsule.     The 
principal  distribution  of  its  branches,  however,  is  to  the  Lobules,  which  they  reach,  in  the 
same  manner  with  the  Portal  vessels  and  Biliary  Ducts,  by  spreading  themselves  through  the 
interlobular  spaces.     There  they  ramify  upon  the  interlobular  ducts,  and  upon  the  capsular 
surface  of  the  lobules,  which  they  then  penetrate;  their  minuteness  prevents  their  distribu- 
tion within  the  lobules  from  being  clearly  demonstrable ;  but,  as  they  enter  along  with  the 
biliary  ducts,  there  can  be  little  doubt  that,  here  as  elsewhere,  they  are.  principally  distributed 
upon  the  walls  of  these.     As  to  the  ultimate  termination  of  the  capillaries  of  the  Hepatic 
Artery, — whether  they  enter  the  Portal  plexus,  or  the  Hepatic  Vein, — there  is  a  difference 
of  opinion  amongst  anatomists ;  the  former  view  being  upheld  by  Kiernan,  the  latter  by 
Muller.     The  question  is  a  very  interesting  one  in  a  physiological  point  of  view ;  since,  if 
the  former  aqcount  be  the  true  one,  the  Blood  which  is  brought  to  the  Liver  by  the  Hepatic 
Artery  becomes  subservient  to  the  secretion  of  Bile,  only  by  passing  into  the  Portal  plexus; 
whilst,  if  the  latter  be  the  correct  statement,  either  the  arterial  Blood  is  not  at  all  subservient 
to  the  formation  of  Bile,  or  the  secretion  can  be  elaborated  from  the  arterial  capillaries.     The 
experiments  of  Mr.  Kiernan  have  satisfactorily  proved,  that  the  Intralobular  or  Hepatic  Veins 
cannot  be  filled  by  injection  from  the  Hepatic  Artery,  though  they  maybe  readily  filled  from 
the  Portal  plexus ;  whilst,  on  the  other  hand,  there  is  reason  to  believe,  that  a  very  fine  in- 
jection into  the  Hepatic  arteries,  will  find  its  way  into  the  Portal  plexus.*     It  is  certain  that 
all  the  branches  of  the  Hepatic  artery,  of  which  the  termination  can  be  ascertained,  end  in 
the  Vena  Portaej  a  free  capillary  communication  existing  between  their  two  systems  of 
branches,  on  the  walls  of  the  larger  blood-vessels  and.  ducts.     According  to  Muller,  there  is 
an  ultimate  plexus  of  capillary  vessels,  with  which  all  the  three  systems  freely  communicate ; 
but  for  this  idea  there  is  no  adequate  foundation;  and  it  is  inconsistent  with  the  fact  just  stated, 
that  injection  into  the  Hepatic  Artery  does  not  return  by  the  Hepatic  vein.     And  the  views 
of  Mr.  Kiernan  have  lately  received  important  confirmation  from  the  researches  of  Mr. 
Bowman  on  the  circulation  in  the  Kidney  (§  841). 

e.  It  now  only  remains  to  describe  the  Hepatic  Veins,  the  branches  of  which  occupy  the 
interior  of  the  Lobules,  and  are  termed  wrtra-lobular  veins  (1,  1,  Figs.  230  and  231).     On 
making  a  transverse  section  of  a  lobule,  it  is  seen  that  the  central  vessel  is  formed  by  the 
convergence  of  from  four  to  six  or  eight  minute  venules,  which  arise  from  the  processes 
upon  the  surface  of  the  lobule.     In  the  superficial  lobules,  (by  which  term  are  designated 
those  lobules  which  lie  upon  the  exterior  of  the  glandular  substance,  not  only  upon  the  sur- 
face of  the  Liver,  but  also  against  the  walls  of  the  larger  vessels,  ducts,  &c.,)  the  Intralobular 
Veins  commence  directly  from  their  surface;  and  the  minute  venules  of  which  each  is  com- 
posed may  be  seen  in  an  ordinary  injection,  converging  from  the  circumference  towards 
the  centre,  as  in  the  transverse  section  of  other  lobules.    The  Intralobular  Veins  terminate  in 
the  larger  trunks,  which  pass  along  the  bases  of  the   lobules,  collecting  from  them  their 
venous  blood ;  these  are  called  by  Mr.  Kiernan  sublobular  veins.     The  main  trunk  of  the 
Hepatic  Vein  terminates  in  the  ascending  Vena  Cava. 

/.  In  regard  to  the  mode  in  which  the  nucleated  Cells,  that  are  the  real  agents  in  the 
Secreting  process,  are  arranged  in  the  Liver  of  Man  and  the  higher  animals,  there  is  much 
uncertainty;  owing  especially  to  our  want  of  acquaintance  with  the  mode  in  which 
the  Hepatic  Ducts  terminate.  They  would  seem  to  form  the  greatest  part  of  the  Paren- 
chyma, which  fills  up  the  interstices  between  the  reticulations  of  the  Blood-vessels 
and  Ducts ;  but  it  is  obvious,  from  their  functional  operation,  that  they  must  have  a  more 


*  This  is  stated  to  have  been  the  case  in  the  injections  of  Lieberkuhn,  although  Mr.  Kier- 
nan has  not  succeeded  in  effecting  it. 


624 


OF  SECRETION. 


Glandular  cells  of 
Liver ;  a,  nucleus  ;  6, 
nucleolus  (?);  c,  adi- 
pose particles. 


Fig.  233. 


Fig.  232.  close    relation   to   the   latter  than   to  the  former.     Their   diameter 

is  usually  from  1-1 500th  to  l-2000th  of  an  inch;  and  they  are  conse- 
quently easily  recognized,  whenever  a  portion  of  the  substance  of 
the  Liver  is  torn  up  and  examined  with  the  higher  powers  of  the 
Microscope.  Their  shape  is  usually  spheroidal.  They  have  a  distinct 
biliary  tinge ;  and  contain  a,  granular  amorphous  matter,  with  a  few 
small  adipose  globules. 

g.  In  regard  to  the  Embryonic  Development  of  the  Human  Liver, 
a  considerable  part  of  our  information  must  necessarily  be  derived 
from  the  study  of  that  of  other  animals ;  and  this  not  so  much  from 
Mammalia,  as  from  Birds  ;  since  the  development  of  this  organ  com- 
mences so  early  in  the  former,  its  phases  are  so  rapidly  hurried 
through,  and  its  evolution  is  so  soon  completed,  that  the  process  cannot 

be  continuously  watched. — In  the  Chick,  the  rudiments  of  the  Liver  are  found  at  the  commence- 
ment of  the  third  day  of  incubation,  in  the 
form  of  two  ccecal  pouches,  which  are  pro- 
longed from  the  Intestinal  tube ;  these  carry 
before  them  a  fold  of  the  vascular  layer,  from 
which  the  blood-vessels  subsequently  origin- 
ate ;  and  they  soon  begin  to  ramify  in  this, 
sending  off  branches,  of  which  the  coecal  ex- 
tremities are  still  evident.  At  the  end  of  the 
fourth  day,  the  tubuli  and  their  ramifications 
have  attained  a  considerable  size  ;  and  they 
approach  each  other  and  coalesce  at  the  base, 
entering  the  intestine  by  an  orifice  common 
to  the  two.  In  this  process,  it  is  easy  to  re* 
cognize  the  analogy  to  the  succession  of 
forms,  which  we  encounter  in  ascending  the 
animal  scale.  The  size  and  density  of  the 
organ  are  gradually  increased ;  but  it  is  not 
until  several  days  afterwards,  that  the  gall- 
bladder is  developed. — In  the  Human  Em- 
bryo, the  formation  of  the  Liver  begins  at 
about  the  third  week  of  intra-uterine  existence  ;  the  organ  is  from  the  first  of  very  large 
size,  when  compared  with  that  of  the  body;  and  between  the  third  and  the  fifth  week,  it  is 
one-half  the  weight  of  the  entire  embryo.  It  is  at  that  period  divided  into  several  lobes. 
By  the  third  lunar  month,  the  liver  extends  nearly  to  the  pelvis,  and  almost  fills  the  abdo- 
men ;  the  right  side  now  begins  to  gain  upon  the  left ;  the  gall-bladder  begins  to  appear  at 
this  time.  The  subsequent  changes  chiefly  consist  in  the  consolidation  of  the  viscus,  and  the 
diminution  of  its  proportional  size.  Up  to  the  period  of  birth,  however,  the  bulk  of  the 
Liver,  relatively  to  that  of  the  entire  body,  is  much  greater  than  in  the  adult ;  the  proportion 
being  as  1  to  18  or  20  in  the  new-born  child,  whilst  it  is  about  1  to  36  in  the  adult:  and 
the  difference  between  the  right  and  left  sides  is  still  inconsiderable.  During  the  first  year  of 
extra-uterine  life,  however,  a  great  change  takes  place ;  the  right  lobe  increases  a  little  or  re- 
mains stationary,  whilst  the  left  lobe  undergoes  an  absolute  diminution,  being  reduced  nearly 
one-half;  and  as,  during  the  same  period,  the  bulk  of  the  rest  of  the  body  has  been  rapidly 
increasing,  the  proportion  is  much  more  reduced  during  that  period,  than  in  any  subsequent 
one  of  the  same  length.  According  to  Meckel,  the  liver  of  the  newly-born  infant  weighs 
one-fourth  heavier  than  that  of  a  child  of  eight  or  ten  months  old ;  and  as  the  weight  of  the 
whole  body  is  more  than  doubled,  during  the  same  time,  it  is  obvious  that  the  change  in  the 
proportion  of  the  two  must  be  principally  effected  at  this  epoch. 

827.  The  knowledge  of  the  distribution  of  the  Biliary  ducts,  and  of  the  two 
chief  systems  of  Blood-vessels,  in  the  Lobules  of  the  Liver,  has  enabled  Mr. 
Kiernan  to  give  a  most  satisfactory  explanation  of  appearances,  by  which 
Pathological  anatomists  had  been  previously  much  perplexed.  When  the 
Liver  is  in  a  state  of  Anaemia  (which  rarely  happens  as  a  natural  condition, 
although  it  may  be  induced  by  bleeding  an  animal  to  death),  the  whole  sub- 
stance of  the  lobules  is  pale,  as  represented  in  Fig.  234.  In  general,  how- 
ever, the  Liver  is  more  or  less  congested  at  the  moment  of  death;  and  this 
congestion  may  manifest  itself  in  several  ways.  The  whole  substance  may 
be  congested ;  in  which  case  the  lobules  present  a  nearly  uniform  dark  colour 
throughout  their  substance,  their  centres  being  usually  more  deeply-coloured 


Origin  of  the  Liver  from  the  intestinal  wall,  in 
the  embryo  of  the  Fowl,  on  the  fourth  day  of  incu- 
bation ;—  a,  heart ;  6,  intestines ;  c,  everted  portion 
giving  origin  to  the  liver ;  d,  liver ;  e,  portion  of 
yolk-bag. 


SECRETION  OF  BILE. 


625 


Fig.  235. 


1,  angular  lobules  in  a  state  of  Ansemia,  as 
they  appear  on  the  external  surface  of  the  liver ; 
2,  interlobular  spaces ;  3,  interlobular  fissures ; 
4,  interlobular  veins,  occupying  the  centres  of 
the  lobules ;  5,  smaller  veins,  terminating  in  the 
central  veins. 


1,  rounded  lobules  infirjst  stage  of  Hepatic  Ve- 
nous congestion,  as  they  appear  on  the  surface 
of  the  liver;  2,  interlobular  spaces  and  fissures. 


than  the  margins.  An  appearance  more  frequently  offered  after  death,  how- 
ever, is  that  represented  at  Fig.  235,  and  termed  by  Mr.Kiernan  the  first  stage 
of  Hepatic  Venous  congestion.  In  this,  the  isolated  centres  of  the  Lobules  alone 
present  the  colour  of  sanguineous  congestion;  and  the  surrounding  substance 
varies  from  a  yellowish-white,  yellow,  or  greenish  colour,  according  to  the 
quantity  and  quality  of  the  Bile  which  it  contains.  This  accumulation  of  the 
blood  in  the  Hepatic  Veins,  and  the  emptiness  of  the  Portal  plexus,  seem  due 
to  the  continuance  of  capillary  action  after  the  general  circulation  has  ceased ; 
— a  circumstance  to  which  we  find  an  exact  parallel,  in  the  emptiness  of  the 
systemic  arteries,  and  the  fulness  of  the  veins,  after  most  kinds  of  death.  In 
the  second  stage  of  Hepatic  Venous  congestion,  the  accumulation  of  blood  is 
found  not  only  in  the  Intralobular  Veins,  but  even  in  parts  of  the  Portal  or 
Lobular  Venous  plexus.  The  parts  which  are  freest  from  it  are  those  sur- 

Fig.  236. 


A,  lobules  in  the  second  stage  of  Hepatic  Venous 
congestion ;  B,  and  c,  interlobular  spaces ;  u,  con- 
gested intralobular  veins ;  E,  congested  patches, 
extending  to  the  circumference  of  the  lobules ; 
F,  non-congested  portions  of  lobules. 


53 


A,  lobules  as  they  appear  on  the  surface  in  a 
state  of  Portal  Venous  congestion ;  B,  interlo  • 
bular  spaces  and  fissures;  c,  intralobular  hepatic 
veins,  containing  no  blood;  D,  the  central  por- 
tions in  a  state  of  anaemia;  E.  the  marginal  por- 
tions in  a  congested  state. 


626  OF  SECRETION. 

rounding  the  interlobular  spaces ;  so  that  the  non-congested  substance  here 
appears  in  the  form  of  circular  or  irregular  patches,  in  the  midst  of  which  the 
spaces  and  fissures  are  seen  (Fig.  236).*  Although  the  Portal  as  well  as  the 
Hepatic  venous  system  is  thus  involved  in  this  form  of  congestion,  yet,  as 
the  obstruction  evidently  originates  in  the  latter,  the  term  given  by  Mr.  Kier- 
nan  is,  still  applicable ;  and  it  is  important  to  distinguish  this  appearance  from 
that  next  to  be  described.  The  second  stage  of  Hepatic  venous  congestion  very 
commonly  attends  disease  of  the  heart,  and  other  disorders  in  which  there  is 
an  impediment  to  the  venous  circulation ;  and  in  combination  with  accumu- 
lation in  the  biliary  ducts,  it  gives  rise  to  those  various  appearances,  which 
are  known  under  the  name  of  dram-drinkers'  or  nutmeg  liver.  The  other 
form  of  partial  congestion  arises  from  an  accumulation  of  blood  in  the  Portal 
veins,  with  a  reverse  condition  of  the  Hepatic  or  intralobular  veins ;  in  this 
condition,  which  Mr.  K.  designates  as  portal  venous  congestion,  the  marginal 
portions  of  the  lobules  are  of  deeper  colour  than  usual,  and  form  a  continuous 
network,  the  isolated  spaces  between  which  are  occupied  by  the  non-congested 
portions  (Fig.  237).  This  is  a  very  rare  occurrence  ;  having  been  seen  by  Mr. 
K.  in  children  only. — These  differences  fully  explain  the  diversity  of  the  state- 
ments of  different  anatomists,  as  to  the  relative  position  of  the  so-called  red 
and  yellow  substances ;  for  it  now  appears,  that  the  red  substance  is  the  con- 
gested portion  of  the  lobules,  which  may  be  either  interior  or  exterior,  or 
irregularly  disposed;  whilst  the  yellow  is  the  non-congested  part,  in  which 
the  Biliary  plexus  shows  itself  more  or  less  distinctly. 

828.  Another  very  interesting  form  of  Pathological  change  in  the  aspect  of 
the  Liver,  which  the  knowledge  of  the  structure  of  the  Lobules  enables  us  to 
comprehend,  is  that  to  which  the  name  of  Cirrhosis  has  been  given.     This 
has  been  erroneously  attributed  to  the  presence  of  a  new  deposit,  analogous  to 
that  of  Tubercular  matter ;  but  it  is  really  due  to  Atrophy  and  partial  Con- 
gestion in  the  Liver  itself.     It  is  described  by  Laennec  as  usually  presenting 
itself  in  small  masses,  varying  in  size  from  a  cherry-stone  to  a  millet-seed, 
and  scattered  through  the  substance  of  the  Liver.     When  these  are  minute, 
and  closely  set,  they  impart  what  appears  at  first  to  be   a  uniform  brownish- 
yellow  tint  to  the  divided  surface  of  the  Liver ;  but  when  the  tissue  is  more 
attentively  examined,  their  separation  becomes  evident.     These  small  masses 
are  not  distinct  lobules  in  a  variable  state  of  hypertrophy  (as  supposed  by 
Cruveilhier) ;  but  small  uncongested  patches,  composed  of  parts  of  several 
adjoining  lobules,  and  having  one  or  more  interlobular  spaces  for  a  centre ; 
and  the  biliary  plexuses  of  these,  being  filled  with  bile,  give  them  their  yellow 
colour.     On  the  other  hand,  there  is  an  atrophy,  more  or  less  complete,  of 
the  portions  of  the  substance  of  the  liver  intervening  between  them ;  so  that 
the  bulk  of  the  whole  organ  is  much  diminished,  very  commonly  to  one-half, 
and  sometimes  to  one-third,  of  its  original  size. 

829.  The  application  of  the  Microscope  to  the  Hepatic  Cells,  in  various  states 
of  disease,  has  afforded  many  facts  of  great  interest.     The  fatty  liver,  which 
is  often  found  in  the  bodies  of  persons  who  have  died  from  diseases  obstructing 
the  pulmonary  circulation,  has  been  shown   by  Mr.   Bowrnant  to   depend 
upon  the  presence  of  a  large  quantity  of  fatty  matter  in  the  interior  of  the 
cells ;  which  frequently  appear  as  if  gorged  with  it.     This  would  seem  to 
be  occasioned  by  the  want  of  elimination  of  the  fatty  matter  through  the 
respiratory  process ;  and  the  consequent  accumulation  of  it  in  the  Blood,  by 

*  This  very  common  aspect  of  the  Liver,  which  presents  numerous  modifications,  has  been 
a  source  of  great  perplexity  to  those  who  have  studied  the  minute  anatomy  of  this  organ,  and 
has  even  led  Anatomists  of. the  highest  eminence  into  serious  errors.  See  Cyclop,  of  Anat. 
and  Physiol.,  vol.  iii.  pp.  185, 186. 

t  Medical  Gazette,  January  1842. 


SECRETION  OF  BILE.  627 

which  the  burden  of  separating  it  is  thrown  upon  the  Liver. — Dr.  Williams* 
mentions,  that,  in  a  case  of  obstruction  of  the  ductus 
choledochus  by  malignant  disease, — which  occasioned  com-  Fig.  238. 
plete  interruption  to  the  passage  of  bile,  and  consequent 
jaundice, — scarcely  an  entire  nucleated  cell  could  be  dis- 
covered by  attentive  examination  of  a  large  part  of  the  organ. 
Nothing  more  than  minute  free  particles  of  fat,  and  free  float- 
ing amorphous  granular  matter,  could  be  detected.  He  further 
states  that,  in  a  case  of  fever,  the  hepatic  cells  were  found  to  Hepatic  Ceils 
be  almost  entirely  destitute  of  fatty  particles;  and  that  in  gorged  with  Fat: 
what  is  known  as  "  granular  liver,"  the  granules  (which  have  3J^ 
much  the  appearance  of  tubercles)  consist  of  cells,  which  globules.' 
strongly  resemble  the  ordinary  cells  of  the  parenchyma  of  the 
Liver  in  every  respect,  except  that  they  are  almost  or  completely  destitute  of 
yellow  contents.  Similar  observations  have  been  also  recorded  by  Dr.  G. 
Budd. — In  two  cases  of  jaundice  examined  by  Mr.  Gulliver,  the  hepatic  cells 
were  gorged  with  biliary  matter;  some  of  them  to  such  an  extent,  that  they 
had  become  nearly  opaqu«.  Perhaps  if  this  condition  had  continued,  these 
cells  would  have  been  all  ruptured,  and  the  state  of  the  organ  would  have 
resembled  that  described  by  Dr.  Williams. 

830.  Previously  to  birth,  the  Liver  is  the  only  decarbonizing  organ  in  the 
system,  the  Lungs  being  at  that  time  inert ;  but  as  soon  as  the  latter  come 
into  play,  they  separate  from  the  Venous  blood  a  large  proportion  of  the  car- 
bon with  which  it  is  charged,  and  less  blood  is  transmitted  to  the  Liver  for 
this  purpose.     The  diminution  in  the  quantity  of  the  BloOd  circulating  through 
this  organ,  is  extremely  rapid ;  and  it  is  usually  very  evident  within  a  short 
time  after  birth,  in  the  comparative  paleness  of  the  substance  of  the  gland.     It 
has  been  proposed  to  give  this  fact  a  practical  bearing,  in  those  judicial  in- 
quiries which  are  directed  to  the  determination  of  the  question,  whether  or 
not  an  Infant  has   respired  after  birth ;  it  having  been  conceived,  that  the 
diversion  of  the  current  of  the  Blood  from  the  Liver  to  the  Lungs,  consequent 
upon  the  first  inspiration,  would  be  sufficient  to  make  a  certain  difference  in 
their  relative  weights,  if  that  inspiration  had  taken  place.     More  careful  and 
extended  observations,  however,  have  satisfactorily  proved  that,  although  an 
increase  in  the  weight  of  the  Lungs,  and  a  diminution  of  that  of  the  Liver,  are 
generally  found  to  exist  after  respiration  has  been  fully  established,  they  are 
not  by  any  means  constantly  produced  when  the  inspirations  have  been  feeble, 
as  they  frequently  are  for  some  hours  or  days  after  birth  ;  whilst,  on  the  other 
hand,  it  is  not  uncommon  to  meet,  in  infants  that  have  not  breathed,  with  Lungs 
as  heavy,  and  Livers  as  light,  as  in  the  average  of  those  which  have  respired.f 

831.  We  have  now  to  consider  the  conditions,  under  which  the  secretion 
of  Bile  takes  place ;  and  one  of  the  most  important  of  these,  is  the  character 
of  the  Blood  with  which  the  organ  is  supplied.     We  have  seen  that  there  is 
anatomical  reason  for  the  belief,  that  the  blood  supplied  by  the  Hepatic  Artery 
is  not  directly  concerned  in  the  Secretion  ;  but  that  it  first  serves  for  the 
Nutrition  of  the  organ,  and  then,  passing  into  the  Portal  system  (in  the  same 
manner  as  does  the  blood  of  the  mesenteric  and  other  arteries),  forms  part  of 
the  mass  of  Venous  Blood,  from  which  the  secreting  cells  elaborate  their  pro- 
duct.    This  view  is  borne  out  by  the  results  of  Experiment,  and  of  Patholo- 
gical observation.     Thus,  if  the  Vena  Portae  be  tied,  the  secretion  of  bile  still 
continues,  though  in  diminished  quantity^  and  several  cases  are  on  record,  in 
which,  through  a  malformation,  the  Vena  Portae  terminated  in  the  Vena  Cava 

*  Guy's  Hospital  Reports^  1843. 

j"  See  Dr.  Guy,  in  Edinb.  Med.  and  Surg.  Journal,  vols.  Ivi.  and  Ivii. 


628  OF  SECRETION. 

without  ramifying  through  the  liver,  and  in  which  secretion  of  Bile  took 
place, — evidently  from  the  blood  of  the  Hepatic  Artery,  which  had  become 
venous  by  circulating  through  the  substance  of  the  Liver;  and  this  blood 
appears*  to  have  passed  into  the  ramifications  of  the  Umbilical  Vein,  which 
formed  a  plexus  in  the  lobules,  exactly  resembling  the  ordinary  portal  plexus. 
It  must  be  remembered,  however,  that  in  all  these  instances,  the  arterial 
Blood  will  become  abnormally  charged  with  the  elements  of  Bile ;  since  the 
blood  of  the  chylopoietic  viscera,  from  which  it  ought  to  have  been  separated, 
returns  to  the  heart  without  undergoing  any  such  purification :  and  the  secre- 
tion of  Bile  from  the  blood  supplied  by  the  Hepatic  Artery  under  such  circum- 
stances cannot,  therefore,  be  considered  as  proving  that  the  arterial  blood  is 
ordinarily  concerned  in  the  secretion  to  the  same  degree. 

832.  That  the  proximate  elements  of  the  Bile  accumulate  in  the  Blood, 
when  from  any  cause  the  secretion  is  suspended,  is   a  fact  now  well  ascer- 
tained ;  and  this  satisfactorily  accounts  for  the  disturbance  of  the  other  func- 
tions, especially  those  of  the  Nervous  system,  which  then  ensues.     When 
the  suppression  is  complete,  the  patient  suddenly  becomes  jaundiced,  the 
powers  of  that  system  are  speedily  lowered  (almost  as  by  a  narcotic  poison), 
and  death  rapidly  supervenes.!     When  the   secretion  is  diminished,  but  not 
suspended,  the  same  symptoms  present  themselves  in  a  less  aggravated  form. 
It  is  probable  that  much  of  the  disorder  in  the  functions  of  the  Brain,  which 
so  constantly  accompanies  deranged  action  of  the  Digestive  system,  is  due  to 
the  less  severe  operation  of  the  same  cause, — the  partial  retention  within  the 
Blood,  of  certain  constituents  of  the  Bile,  which  should  have  been  eliminated 
from  the  circulating  fluid.     In  such  a  condition,  we  derive  great  benefit  from 
the  use  of  mercurial  medicines ;   which,  by  stimulating  the  Liver  to  increased 
action,  cause  the  removal  of  the  morbific  agent  from  the  blood.     Deficient 
secretion  of  the  Liver  may  be  recognized  as  the  cause  of  this  and  of  other 
diseases,  by  the  paleness  of  the  alvine  evacuations,  the  diffused  yellowness  of 
the  surface   of  the  body,  the  yellowish-brown  fur  upon  the  tongue,  and  the 
congestion  of  the  portal  system ;  this  last  results  from  the  same  cause,  as  that 
which  stagnates  the  blood  in  the  Lungs  when  there  is  deficient  Respiration 
(§  738),  and  frequently  occasions  Aseites,  and  other  disorders  of  the  contents 
of  the  abdomen.     An  abnormal  accumulation  of  the  elements  of  the   Bile  in 
the  Blood,  is  habittiaLin  some  persons;  and  it  produces  a  degree  of  indisposi- 
tion to  bodily  or  mental  exertion,  which  it  is  difficult  to  counteract.     It  may 
often  be  recognized  by  the  accumulation  of  dark  mucus  having  distinctly  the 
taste  of  bile,  on  the  surface  of  the  tongue,  especially  during  the  night;  this 
secretion  being  apparently  eliminated  by  the  mucous  membrane  of  the  tongue, 
when  the  function  of  the  liver  is  not  duly  performed. 

833.  Much  discussion  has  taken  place  among  Chemists,  in  regard  to  the 
proximate  principles  of  the  Biliary  secretion  ;  a  large  number  of  analyses  hav- 
ing been  made,  amongst  the  results  of  which  there  is  great  want  of  conformity. 
The  discrepancies  principally  arise  from  this  source, — that  the  secretion  is 
acted  on  with  great  facility  by  chemical  reagents ;  so  that  many  of  the  com- 
ponent parts  which  have  been  enumerated,  are  not  true  educts ;  but  are  pro- 
ducts of  the  operations,  to  which  the  fluid  has  been  subjected.     The  propor- 
tion of  solid  matter  is  usually  from  9  to  12  per  cent,;  and  nearly  the  whole  of 
this  consists  of  substances  peculiar  to  Bile. 

a.  The  following  are  the  general  results  of  the  analyses  made  by  Berzelius,  of  Human 
Bile,  and  of  that  of  the  Ox: — 


*  This,  at  least,  was  found  to  be  the  case,  in  the  only  instance  in  which  the  liver  was 
examined  with  sufficient  care. 

|  See  Dr.  Alison  in  Edinburgh  Medical  and  Surgical  Journal,  vol.  xliv.  p  287. 


SECRETION  OF  BILE.  629 

MAN.  Ox. 

Water    .            ..             .                          .             .             .  90-44  92-84 

Biliary  matter    ......  8-00-  5'00 

Mucus    .             .             .             .             .  -30  -23 

Alkali  (in  combination  with  fatty  acids)            .             .  '41 

Chloride  of  sodium,  and  extractive        .             .             .  -74  1'50 

Phosphates  and  sulphates  of  soda  and  lime       .             .  '11  '43 


100-00  100-00 

In  the  Biliary  matter,  we  are  to  distinguish  at  least  three  distinct  substances ;  Cholesterine, 
Bilic  acid,  and  Colouring  matter. — In  healthy  bile,  the  proportion  of  Cholesterine  appears  to 
be  very  small;  but  in  many  disordered  states  of  the  secretion,  and  especially  in  disease  of 
the  Gall-bladder,  this  substance  is  present  in  much  larger  amount;  and  it  usually  forms  the 
principal,  if  not  the  sole,  ingredient  in  biliary  concretions.  It  is  a  white  crystallizable  fatty 
matter,  somewhat  resembling  Spermaceti;  free 'from  taste  and  odour;  not  soluble  in  water, 
but  dissolving  freely  in  alcohol,  from  which  it  is  deposited  on  cooling  in  pearly  scales.  It 
is  almost  entirely  composed  of  Carbon, and  Hydrogen;  its  constitution  being  36  Carbon,  32 
Hydrogen,  1  Oxygen.  It  may  be  obtained  by  a  chemical  process  of  no  great  complexity, 
from  the  Serum  of  the  BJood;  and  it  is  not  unfrequently  deposited  as  a  result  of  diseased  ac- 
tion in  other  parts  of  the  body,  especially  in  the  fluids  of  local  Dropsies,  as  hydrocele,  ovarian 
dropsy.  &c.  %  , 

b.  The  principal  constituent  of  Bile  is  a  compound  of  soda  with  a  peculiar  organic  body ; 
which  is  now  generally  regarded  in  the  light  of  a  fatty  acid,  and  named  Bilic  add.    Accord- 
ing  to  Platner,  this  bilic  acid  and  the  bibilate  of  soda  may  be  obtained  in  a  pure  crystalline 
state  from  fresh  bile ;  a  yellowish-brown  syrup  being  left,  which  seems  principally  to  consist 
of  colouring  matter  diffused  through  the  water.     No  analysis  has  yet  been  made  of  bilic  acid 
thus  purified ;  that  of  Dr.  Kemp,  rnade  upon  an  impure  bilic  acid,  gives  as  its  ultimate  com- 
position 48  Carbon,  42  Hydrogen,  13  Oxygen,  and  1  Nitrdgen.  This  is  the  substance  described 
by  different  Chemists  (doubtless  under  various  modifications,  according  to  the  process  used 
to  obtain  it),  as  Choleic  acid,  Bilin,  Picromel,  &c.     It  is  very  readily  altered  by  reagents,  espe- 
cially by  acids;  and  a  great  variety  of  products  may  be  formed  by  its  decomposition.     Some 
of  these  appear  to  present  themselves  in  the  living  body,  as  results  of  disordered  condition^ 
of  the  secreting  process. 

c.  The  colouring  matter  of  the  bile  is  now  termed  Eiliverdin.    That  of  the  Ox  contains  no 
azote ;  and  appears  to  be  identical  with  the  Chlorophyl  of  plants.     That  of  Man,  however, 
contains  about  7  per  cent,  of  Azote,  with  68  parts  of  Carbon,  7£  of  Hydrogen,  and  17^  of 
Oxygen;   and  it  cannot  be  derived  so  directly  from  the  food.     When   exposed  to  the  air,  it 
becomes  of  a  deep  green  absorbing  oxygen ;  and  the  same  change  is  produced  by  nitric  acid, 
—the  liquor  soon  passing,  however,  to  a  red  hue..   This  frequently  takes  place  within  the 
body,  in  cases  of  Jaundice;  but  more  especially  in  the  urine.     Though  the  colouring  matter 
is  usually  present  but  in  small  quantity  during  health,  it  sometimes  accumulates  in  disease, 
so  as  to  produce  solid  masses,  which  include  little  else. 

834.  The  amount  of  the  secretion  of  Bile  appears  to  bear  some  proportion 
to  that  of  the  Food  digested.  That  its  formation  is  continually  going  on  to  a 
certain  degree  appears  unquestionable ;  but  that  its  quantity  is  greatly  increased 
during  the  solution  of  food  in  the  stomach,  appears  also  to  be  well  established. 
In  those  animals  which  are  most  constantly  ingesting  food,  we  find  no  Gall- 
bladder :  for  in  them,  the  Bile  may  be  poured  into  the  Intestine  as  fast  as  it  is 
formed.  In  those  which  only  take  food  occasionally,  on  the  other  hand,  and 
which  are  provided  with  a  Gall-bladder,  the  Bile,  when  not  required  in  the 
Intestine,  flows  back  into  that  reservoir.  This  reflex  would  appear  due  to  the 
valve-like  termination  of  the  Ductus  Choledochus  in  the  walls  of  the  Intestine ; 
by  which  a  certain  resistance  is  offered  to  the  entrance  of  the  fluid,  unless  it 
be  propelled  by  some  decided  force.  The  flow  of  Bile  into  the  Intestinal  tube, 
when  its  action  is  needed  there,  is  commonly  imputed  to  the  pressure  of  the 
distended  Duodenum  against  the  Gall-bladder;  it  may  be  doubted,  however, 
whether  the  contractile  power  of  the  Duct  itself  does  not  afford  important  aid 
in  the  process ;  and  it  is  easy  to  understand,  from  the  known  influence  of  the 
Sympathetic  system  of  nerves  upon  it  (§  825,/),  that  peristaltic  movements 
may  be  thus  excited  at  the  time  when  they  are  needed. — It  is  an  interesting 
fact,  proving  how  completely  the  passage  of  Bile  into  the  Intestine  is  depend- 

53* 


630  OF  SECRETION. 

ent  upon  the  presence  of  aliment  in  the  latter,  that  the  Gall-bladder  is  almost 
invariably  found  turgid  in  persons  who  have  died  of  starvation ;  the  secretion 
formed  at  the  ordinary  slow  rate  having  gradually  accumulated,  for  want  of 
demand.  This  fact  is  important  in  juridical  inquiries. 

835.  The  Bile,  as  already  shown  (§  660),  has  an  important  operation  to 
effect  in  the  Digestive  process ; — that  of  reducing  the  oily  matter  of  the  food 
to  a  state  in  which  it  may  be  taken  up  by  the  Absorbent  vessels.     This  it 
effects  by  means  of  its  soapy  character ;  which,  notwithstanding  the  doubts 
of  Chemists,  seems  to  be  proved  by  familiar  facts.     Thus,  Ox-Gall  is  com- 
monly employed  to  remove  grease  spots  ;  and  the  bile  of  the  Sea-Wolf  (Anar- 
rhicas  lupus)  is  ordinarily  used  as   soap  by  the  Icelanders.     Moreover,  the 
small  quantity  of  Cholesterine  contained  in  healthy  Bile,  is  certainly  in  a  state 
of  complete  solution;  the  biliary  soap  having  the  same  action  upon  it,  as 
upon  the  oleaginous  constituents  of  the  chyme. — From  the  recent  experiments 
of  H.  Meckel,  however,  it  appears  that  the  Bile  may  perform  another  very 
important  office, — the   transformation  of  sugar  into  fatty  matter.     He  found 
that,  when  bile  was  mingled  with  grape-sugar,  and  allowed  to  remain  in  con- 
tact with  it  for  some  time,  a  much  larger  quantity  of  fatty  matter  existed  in 
the  mixture,  than  could  have  been  present  in  the  bile  ;   and  that  the  transfor- 
mation is  much  aided  by  heat.     Thus,  the  amount  of  fat,  contained  in  an  equal 
amount  of  the  bile  employed,  having  been  ascertained  from  parallel  experi- 
ments to  be  from  '48  to  '54  grammes,  the  amount  obtained  from  the  mixture 
of  bile  and  grape-sugar,  after  five  hours'  exposure  to  the  warmth  of  an  incu- 
bating machine,  was  *87  grammes  ;  and  after  twenty-four  hours'  exposure,  1*84 
grammes.*     It  seems  probable  that  this  transformation  may  take  place  in  the 
Liver  itself;  for  in  animals  fed  upon  grape-sugar,  this  substance  has  been  de- 
tected in  the  blood  of  the  portal  vein,  but  not  in  that  of  the  hepatic  vein.     It 
will  take  effect,  not  merely  upon  the   Sugar  introduced  as  such  in  the  food, 
but  also  upon  the  amylaceous  substances,  which  have  been  converted  into 
sugar  by  the  action  of  the  Salivary  and  Pancreatic  fluids  (§  670). 

836.  There  can  be  no  doubt,  however,  that  the  Bile  is  partly  an  excremen- 
titious  fluid ;   a  portion  of  it  being  destined  to  be  at  once   carried  out  of  the 
system,  by  the  intestinal  canal,  although  another  portion  is  destined  to  be  re- 
absorbed,  for  the  purpose  (as  it  would  seem)  of  being  ultimately  carried  off 
by  the  respiratory  process.     The  former  part  probably  includes  the  whole  of 
the  colouring  matter ;  the  presence   of  which  in  the  faeces  is  sufficiently  ob- 
vious.    The  latter  seems  usually  to  comprise  the  fatty  or  soapy  portion  ;  no 
distinct  indications  of  which  can  be  generally  found  in  the  faeces,  unless  they 
have  rapidly  passed  through  the  alimentary  canal  (§  662).     But  in  particular 
states  of  the  system,  the  freces  may  contain  a  very  large  quantity  of  bile ;  the 
presence  of  which  almost  unchanged,  may  be  recognized  in  the   evacuations 
in   bilious  diarrhoea,  and  in  the   stools  which  follow  mercurial  purgatives. 
Hence  the  Bile  may  be  a  completely  excrementitious  product;  and  the  idea 
of  the  action  of  the  Liver,  as  one  of  the  great  purifiers  of  the  body  from  the 
results  of  its  decay,  is  not  at  all  invalidated  by  the  observation,  that  a  large 
part  of  its  secretion  is  ordinarily  destined  for  immediate  re-absorption.     The 
composition  of  the  secretion  clearly  indicates,  that  it  is  especially  intended  to 
eliminate  from  the  blood  its  superfluous  Hydro-Carbon, — whether  this   have 
been  absorbed  as  such  from  the  aliment,  or  have  been  taken  up  by  the  Blood 
as  effete  matter,  during  the  course  of  the  circulation. 

a.  If  more  non-azotized  food  be  taken  into  the  system,  than  can  be  got  rid  of  by  the 
Respiratory  process,  and  if  there  be  not  a  sufficiently  rapid  production  of  Adipose  tissue  to 
admit  of  its  being  deposited  as  Fat,  it  would  accumulate  in  the  Blood,  unless  separated  by 


*  Mr.  Pagefs  Report,  in  Brit,  and  For.  Med.  Rev.,  July  1846,  p.  261. 


SECRETION  OF  BILE.  631 

the  Liver.  If  too  much  work  be  thrown  upon  this  organ,  its  function  becomes  disordered, 
from  its  inability  to  separate  from  the  Blood,  all  that  it  should  draw  off:  the  injurious  sub- 
stances accumulate  in  the  Blood,  therefore,  producing  various  symptoms  that  are  known  un- 
der the  general  term  of  bilious.  This  is  particularly  liable  to  happen  in  warm  climates,  in 
consequence  of  the  diminished  excretion  through  the  Lungs, — occasioned  by  the  warmth  of 
the  surrounding  air,  and  the  small  quantity  of  exercise  usually  taken.'  To  remove  these 
symptoms,  medicines  are  required,  which  shall  stimulate  the  liver  to  increased  action.  The 
constant  use  of  such,  however,  has  a  very  pernicious  effect  upon  the  constitution ;  and  care- 
ful attention  to  the  regulation  of  the  diet, — especially  the  avoidance  of  a  superfluity  of  oily 
or  farinaceous  matter, — together  with  the  employment  of  an  increased  amount  of  exercise, 
will  probably  answer  the  same  end  in  a  much  better  manner. 

Besides  the  source  of  Biliary  matter  already  pointed  out  in  the  decompo- 
sition of  the  Fibrinous  tissues  (§  819),  it  seems  probable  that  there  is  another 
very  important  one  in  the  continual  waste  of  Nervous  matter,  which  more 
nearly  approaches  Bile  in  composition  (§  249);  especially  if,  as  asserted  by 
Fremy,  the  peculiar  acids  of  the  Brain  may  be  detected  in  the  Liver.  In 
cases  of  slow  Asphyxia,  the  amount  of  the  Biliary  secretion  is  much  increased; 
as  might  be  expected,  from  what  has  just  been  stated  of  its  purpose. 

837.  It  would  not  seem  improbable,  that  the  Liver  acts  towards  the  ab- 
sorbed matters  which  enter  the  blood  by  the  Mesenteric  Veins,  the  same  part 
which  the  Lungs  perform  for  those  which  are  introduced  through  the  Lymph- 
atic system  ;  namely,  the  affording  an  opportunity  for  the  excretion  of  super- 
fluous or  injurious  substances  contained  in  the  absorbed  fluid,  before  it 
enters  the  general  current  of  the  Circulation.  There  is  every  reason  to  be- 
lieve, that  the  conversion  of  Chyle  into  Blood  is  a  slow  process,  requiring  the 
prolonged  influence  of  the  latter  fluid  upon  the  former;  during  this  influence 
many  chemical  changes  take  place,  which  are  almost  certain  to  be  attended 
with  an  extrication  of  Carbon  and  Hydrogen,  these  being  the  ingredients  of 
which  the  Chyle  contains  most  when  compared  with  blood ;  and  for  the  extrica- 
tion of  these,  the  Lungs  and  Liver  afford  ready  means.  Hence  we  see  why  the 
Lacteal  system  should  terminate  in  a  Venous  trunk  near  the  Heart,  so  that  the 
fluid  discharged  by  it  will  proceed  at  once  to  the  Lungs  ;  and  why  the  Liver, 
wherever  it  has  a  distinct  circulation,  should  receive  the  blood  from  the  walls 
of  the  Intestines.  Among  the  Mollusca,  in  which  the  chyle  is  absorbed  by 
the  mesenteric  veins,  (there  being  no  separate  lacteal  system,)  these  veins,  in- 
stead of  returning  to  the  heart  through  the  liver,  terminate  in  the  branchial 
vessels  ;  and  the  process  of  depuration  is  effected  by  the  gills.  Their  liver 
is  supplied  only  by  the  hepatic  artery. 

a.  This  view  derives  interesting  confirmation  from  the  experiments  of  Cruveilhier,  on 
the  artificial  production  of  purulent  deposits  by  injection  of  Mercury  into  the  veins.  He  found 
that,  when  the  mercury  was  introduced  into  any  part  of  the  general  venous  system,  abscesses 
in  the  Lungs  were  induced ;  each  inclosing  a  globule,  the  irritation  occasioned  by  which 
was  the  cause  of  the  purulent  deposit.  When  the  mercury  was  introduced  into  one  of  the 
Intestinal  veins,  on  the  other  hand,  similar  purulent  deposits  occurred  in  the  Liver.  It  is 
well  known  that  abscesses  in  the  Lungs  aiid  Liver  are  very  common  sequelae  of  wounds  of 
the  head,  and  of  surgical  operations,  especially  those  in volving  bones ;  and  there  seems  good 
reason  to  believe,  that  in  such  cases  PUS  (or  some  of  its  elements,  which  may  act  the  part  of 
a  ferment  in  exciting  suppuration  elsewhere) .  is  actually  carried  along  with  the  current  of  blood 
in  the  Lungs  and  Liver;  and  that,  like  the  globules  of  mercury,  not  being  susceptible  of  elimi- 
nation by  these  two  great  emunctories,  it  acts  as  a  disturbing  cause,  and  occasions  disease  of 
their  tissue.  The  fact  that  a  considerable  amount  of  Copper  may  be  detected  in  the  substance 
of  the  Liver,  after  the  prolonged  introduction  of  its  salts  into  the  system,  seems  to  add  weight 
to  this  view  of  its  function.  It  is  yet  to  be  ascertained,  however,  why  some  substances  should 
be  arrested  in  this  organ,  whilst  others  are  allowed  to  pass. 


632 


OF  SECRETION. 


3. — The  Kidneys — Secretion  of  Urine. 

838.  The  Kidneys  cannot  be  regarded  as  inferior  in  importance  to  the 
Liver,  when  considered  merely  as  excreting  organs ;  but  their  function  only 
consists  in  separating  from  the  blood  certain  effete  substances,  which  are  to 
be  thrown  off  from  it;  and  has  no  direct  connection  with  any  of  the  nutritive 
operations,  concerned  in  the  introduction  of  aliment  into  the  system.  Organs 
destined  to  the  elaboration  of  a  Urinary  secretion  may  be  traced  very  low 
down  in  the  Animal  scale.  Among  many  of  the  Mollusca  we  find  a  small 
sac,  filled  with  a  semi-fluid  secretion  which  has  been  shown  to  contain  uric 
acid,  opening  into  the  intestine,  near  its  anal  orifice.  In  Insects,  we  often 
meet  with  prolonged  tubes,  resembling  the  biliary  vessels  in  form,  but  termi- 
nating in  a  lower  part  of  the  intestinal  tube  ;  hi  some  species  these  are  dilated 
near  their  extremity  into  a  receptacle  for  their  secretion,  or  a  urinary  bladder. 
Throughout  the  Vertebra  ted  classes,  they  exist  in  a  still  more  evident  form. 
They  are  uniformly  composed  of  a  congeries  of  prolonged  tubes,  subdividing 
and  ramifying  more  or  less  ;  which  spring  from  the  ureter  or  efferent  duct, 
and  terminate  either  in  blind  extremities,  or  in  a  plexus  formed  by  their  inos- 
culation. There  are  considerable  variations  in  the  arrangement  of  these  tubes, 
however,  in  different  tribes  of  animals.  In  Fishes,  the  Kidneys  very  com- 
monly extend  the  whole  length  of  the  abdomen ;  and  they  consist  of  tufts  of 
uniform-sized  tubules,  which  shoot  out  transversely  at  intervals  from  the  long 
ureter.  These  tubes  frequently  divicle  into  pairs,  but  without  any  great  alte- 
ration in  their  diameter.  They  appear  to  terminate  in  ccecal  extremities,  with- 
out any  inosculation;  the  number  of  bifurcations,  and  the  degree  of  convolu- 

[Fig.  240. 


A  view  of  the  Right  Kidney  with  its  Renal 
Capsule  ;  1,  anterior  face  of  the  kidney  ;  2,  exter- 
nal or  convex  edge ;  3,  its  internal  edge  ;  4,  hilum 
renale  ;  5,  inferior  extremity  of  the  kidney;  6,  pel- 
vis of  the  ureter ;  7,  ureter ;  8,  9,  superior  and  in- 
ferior branches  of  the  emulgent  artery ;  10, 11, 12, 
the  three  branches  of  the  emulgent  vein  ;  13,  an- 
terior face  of  the  renal  capsule ;  14,  its  superior 
edge ;  15,  its  external  edge ;  16,  its  internal  ex- 
tremity; 17,  the  fissure  on  the  anterior  face  of  the 
capsule.] 


A  section  of  the  Kidney,  surmounted  by  the 
Supra-Renal  Capsule  ;  1,  the  supra-renal  cap- 
sule ;  2,  the  vascular  portion ;  3,  3,  its  tubular 
portion,  consisting  of  cones ;  4,  4,  two  of  the 
calices  receiving  the  apex  of  their  correspond- 
ing cones  ;  5, 5,  5,  the  three  infundibula  ;  6,  the 
pelvis ;  7,  the  ureter.] 


THE  KIDNEYS — SECRETION  OF  URINE. 


633 


[Fig.  241. 


Represents  the  half  of  a  Kidney  di- 
vided vertically,  and  with  its  arteries 
injected ;  the  matter  has  also  passed 
into  the  excretory  ducts;  1,  2,  branches 
of  the  emulgent  artery ;  3,  3,  hilum  re- 
nale ;  4,  4,  cprtical  substance,  as  essen- 
tially formed  by  the  capillary  termina- 
tions of  the  vessels  of  the  kidney ;  5, 
medullary  or  tubular  portion.] 


A  view  of  half  a  Kidney  divided  vertically  from  its  con- 
vex to  its  concave  edge  ;  one  of  its  extremities  is  perfect; 
1, 1,  the  lobes  which  form  the  kidney  ;  2,  2,  the  lines  of  se- 
paration of  these  lobes ;  3,  the  cortical  substance ;  4,  5,  the 
pyramids  of  Malpighi;  6,  the  hilum  renale  split  up  and 
cleared  of  its  vessels ;  7,  7,  poilits  to  the  tubes  of  Bellini ; 
8,  one  of  the  papillae  ;  9, 10,  two  other  papillae,  uncut,  but 
deprived  of  the  calicesthat  surrounded  them;  11,  one  of  the 
foveolae  in  the  papilla ;  12, 12,  the  vascular  circle  sur- 
rounding the  papillae ;  13,  circumference  of  the  tubular 
portion ;  14,  external  surface  of  the  kidney  ;  15,  the  por- 
tion of  its  external  surface  on  a  line  with  its  fissure.] 

tion,  vary  greatly  in  different  species.  The  uriniferous  tubes  are  connected 
together  by  a  very  loose  areolar  web. — The  structure  of  the  gland  in  Reptiles 
appears  to  be  essentially  the  same  ;  its  form,  however,  varies  considerably 
in  the  different  tribes,  being  greatly  prolonged  in  the  Serpents,  and  abbreviated 
in  the  Tortoises.  In  the  Crocodile,  the  distinction  between  the  cortical  and 
medullary  portion  begins  to  show  itself;  the  tubes  being  nearly  straight  where 
they  issue  from  the  ureter,  and  being  convoluted  near  the  surface  only  of  the 
lobes.  The  Corpora  Malpighiana  (§  839,  6), however,  where  they  exist  in  this 
class,  are  scattered  through  the  whole  substance ;  not  being  confined,  as  in 
higher  animals,  to  the  cortical  portion. — In  Birds,  the  urinary  tubes,  forming 
the  several  clusters,  are  more  closely  united  together;  they  frequently  ramify 
to  a  considerable  degree. — In  the  Mammalia,  as  in  Man,  there  is  an  evident 
distinction  between  the  straight  and  the  convoluted  portions  of  the  system  of 
tubes ;  the  former  character  is  seen  in  the  medullary  substance  ;  the  latter  in 
the  cortical.  In  nearly  all  below  the  Mammalia,  the  kidneys  present  exter- 
nally a  tabulated  aspect ;  resulting  from  the  want  of  union  between  the  differ- 
ent bundles  of  tubes,  which  arise  from  separate  parts  of  the  ureter.  In  the 
kidney  of  the  Mammalia,  however,  the  ureter  dilates  into  a  capacious  recep- 
tacle, towards  which  the  several  bundles  of  uriniferous  tubes  converge,  so 
that  they  open  into  it  in  close  proximity  with  each  other ;  and  the  lobules 
formed  by  these  bundles  are  so  closely  brought  together,  that  no  appearance 
of  a  division  presents  itself,  until  a  section  of  the  gland  is  made.  Among 
some  Mammalia,  however,  the  lower  form  is  still  retained  ;  and  it  is  presented 
in  the  Human  species  also,  at  an  early  period  of  its  festal  development. 

839.  The  following  is  an  account  of  the  structure  of  the  Kidney,  according 
to  the  most  recent  investigations.* 

*  See  Bowman  in  Philosophical  Transactions,  1842;  afso  Gerlach,  in  Miiller's  Archiv., 
Heft  4,  1845,  and  in  Banking's  Abstract,  vol.  iii.  p.  307. 


634 


OF  SECRETION. 


a.  The  distinction  between  the  cortical  and  medullary  parts  of  the  Kidney  essentially  con- 
sists in  this,— that  the  former  is  by  far  the  most  vascular,  and  the  plexus  formed  by  the 
tubuli  uriniferi  seems  to  come  into  the  closest  relation  with  that  of  the  sanguiferous  capil- 
laries, so  that  it  is  probably  the  seat  of  the  greater  part  of  the  process  of  secretion;  whilst 
the  latter  is  principally  composed  of  tubes,  passing  in  a  straight  line  from  the  former  towards 
their  point  of  entrance  into  the  ureter.  In  this  respect  there  is  a  .considerable  analogy  of 
structure  and  comparative  function,  between  the  two  parts  of  the  kidney  and  the  two  parts 
of  the  brain.  The  adjoined  figure  represents  the  appearances  presented  by  a  portion  of  an 


Fig.  243. 


Fig.  244. 


Portion  of  the  Kidney  of  a  new-born  infant ;  A,  natural 
size;  1, 1,  corpora  Alalpighiana,  as  dispersed  points  in  the 
cortical  substance ;  2,  2,  papilla ;  B,  a  smaller  part  magni- 
fied j  1, 1,  corpora  Malpighiana ;  2,  2,  tubuli  uriniferi. 


Portion  of  one  of  the  tubuli  uriniferi, 
from  th*  kidney  of  an  adult;  showing 
its  tesselated  epithelium.  Magnified 
250  diameters. 


injected  kidney,  as  seen  by  the  naked  eye,  and  under  a  low  magnifying  power.  The  tubuli 
uriniferi,  in  passing  outwards  from  the  calices,  increase  in  number  by  divarication,  -to  a  con- 
siderable extent,  as  shown  in  Fig.  246;  but  their  diameter  remains  the  same.  When  they 
arrive  in  the  cortical  substance,  their  previously  straight  direction  is  departed  from,  and  they 
become  much  convoluted.  The  "closeness  of  the  texture  formed  by  their  interlacement  with 
the  blood-vessels,  renders  it  difficult  to  obtain  a  clear  view  of  their  mode  of  termination. 
They  seem  to  inosculate  with  each  other,  forming  a  plexus,  with  a  free  extremity,  or  more 
probably  a  loop,  here  and  there  (Fig.  246);  the  number  of  these  free  extremities,  however, 
does  not  appear  to  be  nearly  equal  to  that  of  the  uriniferous  tubes  themselves. 

b.  Scattered  through  the  plexus  formed  by  the  blood-vessels  and  uriniferous  tubes,  a  num- 
ber of  little  dark  points  may  be  seen  with  the  naked  eye,  to  which  the  designation  of  Cor- 
pora Malpighiana  has  been  given,  after  the  name  of  their  discoverer.  Each  one  of  these, 
when  examined  with  a  high  magnifying  power,  is  found  to  consist  of  a  mass  of  minute 
blood-vessels  (Fig.  246,  7)  ;  somewhat  resembling  those  convoluted  masses  of  Absorbents, 
termed  Lymphatic  Glands.  Each  of  these  is  included  in  an  offshoot  from  one  of  the  tubuli 
uriniferi,  which  swells  into  a  flask-like  dilatation  to  receive  it  (Fig.  247) ;  and  every  tube 
may  have  several  such  lateral  offshoots.  The  Epithelium  which  elsewhere  lines  the  tube 
(whose  usual  character  is  shown  in  Fig.  244)  is  altered  in  appearance,  where  the  tube  is 
continuous  with  this  capsular  dilatation  (Fig.  247,  2') ;  being  there  more  transparent,  and 
furnished  with  cilia  (as  shown  at  2"),  which  in  the  Frog  may  be  seen,  for  many  hours  after 
death,  in  very  active  motion,  directing  a  current  down  the  tube.  Further  within  the  capsule, 
the  Epithelium  is  excessively  delicate ;  but  it  may  be  clearly  seen  to  cover  the  convoluted 
knot  of  vessels,  which  constitutes  the  Malpighian  body.* — The  Renal  Artery,  on  entering 
the  Kidney,  divides  itself  into  minute  twigs,  which  are  the  afferent  vessels  of  the  Malpighian 
tufts  (Fig.  248,  a/).  After  it  has  pierced  the  capsule,  the  twig  dilates ;  and  suddenly  divides 
and  subdivides  itself  into  several  minute  branches,  terminating  in  convoluted  capillaries, 
which  are  collected  in  the  form  of  a  ball  (m,  m}  ;  and  from  the  interior  of  the  ball,  the  soli- 
tary efferent  vessel,  ef,  arises,  which  passes  out  of  the  capsule  by  the  side  of  the  single  affe- 
rent vessel.  This  ball  seems  to  lie  loose  and  bare  in  the  capsule,  being  attached  to  it  only 
by  its  afferent  and  efferent  vessels  (Fig.  248,  m) ;  but  it  appears  in  reality  to  be  enveloped 
in  a  reflexion  of  the  membrane  that  forms  the  capsule;  and  from  this  are  probably  generated, 
the  epithelium-cells,  by  which  it  is  covered.  The  efferent  vessels,  on  leaving  the  Malpighian 
bodies,  separately  enter  the  plexus  of  capillaries,  p,  surrounding  the  tubuli  uriniferi,  st,  and 
supply  that  plexus  with  blood :  from  this  plexus  the  Renal  vein  arises. — In  Mr.  Bowman's 


*  On  this  point,  which  is  one  of  difference  between  Mr.  Bowman  and  Dr.  Gerlach,  the, 
Author's  own  observations  lead  him  unhesitatingly  to  concur  with  the  latter. 


SECRETION  OF  URINE, 

[Fig.  245. 


635 


A  section  of  one  of  the  Pyramids  of  Malpighi,  and  of  its  corresponding  cortical  substance,  as  seen 
under  the  microscope  ;  1,  portion  of  the  surface  of  the  kidney ;  2,  from  this  figure  up  to  1,  is  the  cortical 
substance  of  the  kidney  ;  3,  from  2  to  this  number  is  the  tubular  portion  ;  4,  the  foveola ;  6,  6,  arteries 
and  veins  ramifying  through  the  kidney ;  7,  arteries  to  the  acina  of  the  kidney  ;  8,  capillary  extremities 
of  veins  anastomosing  with  corresponding  arterioles;  9,  tortuous  extremities  of  the  arteries  directed 
into  the  interior  of  the  gland  ;  10,  bases  of  the  cones  of  the  cortical  and  pyramidal  substance  of  the  kid- 
ney ;  from  10  to  4  is  a  collection  of  these  cones ;  11,  the  envelop  of  the  cortical  layer;  12,  prolongations 
of  the  tubular  portion  ;  13,  tortuous  tubes,  or  those  of  Ferrien  ;  14,  straight  tubes,  or  those  of  Bellini ;  15, 
vessels  which  wind  between  them ;  16,  course  of  the  uriniferous  tubes  in  the  tubular  portion  ;  17,  the 
matter  between  these  tubes ;  18,  bifurcation  of  the  straight  tubes ;  19,  sections  of  these  tubes ;  20,  their 
orifices.] 

opinion,  all  the  free  extremities  of  the  tubuli  uriniferi  thus  include  Corpora  Malpighiana ; 
and  the  appearance  of  coacal  terminations,  such  as  those  represented  at  a  and  c,  Fig.  246,  he 
regards  as  an  optical  illusion,  caused  by  a  change  in  the  direction  of  the  tubuli,  which  occa- 
sions them  to  dip  away  suddenly  from  the  observer. 


636 


OF  SECRETION. 

Fig.  246. 


7         2  3 


I 


A  small  portion  of  the  Kidney,  magnified  about  60  times;  1,  supposed  C03cal  extremity  of  a  tubulus 
uriniferus ;  3,  3,  recurrent  loops  of  tubuli ;  5,  5,  bifurcations  of  tubuli ;  4,  5,  6,  tubuli  converging  towards 
the  papilla ;  7,  7,  7,  Corpora  Malpighiana,  seen  to  consist  of  plexuses  of  blood-vessels,  connected  with  a 
capillary  net- work ;  8,  arterial  trunk. 

c.  The  Embryological  Development  of  the  Urinary  organs  in  Vertebrated  animals  is  a 
subject  of  peculiar  interest;  owing  to  the  correspondence  which  may  be  traced  between  the 
transitory  forms  they  present  in  the  higher  classes,  and  their  permanent  condition  in  the 
lower.  In  this  respect  there  is  an  evident  analogy  with  the  Respiratory  system.  The  first 


THE  KIDNEYS — SECRETION  OF  URINE. 


637 


appearance  of  anything  resembling  a  Urinary  apparatus  in  the  Chick,  is  seen  on  the  second 
half  of  the  third  day.  The  form  at  the  time  presented  by  it  is  that  of  a  long  canal,  extend- 
ing on  each  side  of  the  Spinal  Column,  from  the  region  of  the  heart,  towards  the  Allantois ; 
and  the  sides  of  this  present  a  series  of  elevations  and  depressions,  indicative  of  the  com- 
mencing development  of  coeca.  On  the  fourth  day,  the  Corpora  Wolffiana,  as  they  then  are 
termed,  are  distinctly  recognized,  as  composed  of  a  series  of  coecal  appendages,  which  are 
attached  along  the  whole  course  of  the  first-mentioned  canal,  opening  into  its  outer  side.  On 
the  fifth  day  these  appendages  are  convoluted;  and  the  body  which  they  form  acquires 
increased  breadth  and  thickness.  They  evidently  then  possess  a  secreting  function ;  and  the 
fluid  which  they  separate  is  poured  by  the  long  straight  canal  into  the  cloaca.  Between 
their  component  shut  sacs,  numbers  of  small  points  appear,  which  consist  of  little  clusters 
of  convoluted  vessels,  exactly  analogous  to  the  Corpora  Malpighiana  of  the  kidney. — The 


Fig.  247. 


Fig.  248. 


Fig.  249. 


..«./f 


Uriniferous  Tube,  Malpighian 
Tuft,  and  Capsule,  from  Kidney 
of  Frog :  a,  cavity  of  the  tube ; 
fc,  epithelium  of  the  tube;  &', 
ciliated  epithelium  of  the  neck 
of  the  capsule;  6",  detached 
epithelium  scale;  c,  basement 
membrane  of  tube ;  c',  basement 
membrane  of  capsule.  Magnified 
about  320  diam. 


Distribution  of  the  Renal  ves- 
sels ;  from  Kidney  of  Horse ;  a, 
branch  of  Renal  artery;  of, 
afferent  vessel;  m,  m,  Malpig- 
hian tufts;  e/",  ef,  efferent  ves- 
sels; p,  vascular  plexus  sur- 
rounding the  tubes ;  s£,  straight 
tube ;  ct,  convoluted  tube.  Mag- 
nified about  30  diam. 


Corpora  Wolffiana,  with  kid- 
ney and  testes,  from  embryo  of 
Bird;  1, kidney;  2,2, ureters;  3, 
corpus  Wolffianum ;  4,  its  ex- 
cretory duct;  5,  5,  testicles;  at 
the  summit  are  seen  the  supra- 
renal capsules. 


Corpora  Wolffiana,  however,  have  only  a  temporary  existence  in  the  higher  Veftebrata; 
although  it  seems  that,  in  Fishes,  they  constitute  the  permanent  kidney.*  The  development 
of  the  true  Kidneys  commences  in  the  Chick  about  the  fifth  day.  They  are  seen  on  the 
sixth,  as  tabulated  grayish  masses,  which  sprout  from  the  outer  edges  of  the  Wolffian  bodies ; 
and  they  gradually  increase,  the  temporary  organs  diminishing  in  the  same  proportion.  The 
sexual  organs,  as  will  be  hereafter  explained  (§  866, 6),  also  originate  in  the  Wolffian  bodies; 
and  at  the  end  of  foetal  life,  the  only  vestige  of 'the  latter  is  to  be  found  as  a  shrunk  rudi- 
ment situated  near  the  testes  of  the  male. — The  progress  of  development  in  the  Human 
embryo  seems  closely  conformable  to  the  foregoing  account.  The  Wolffian  bodies  begin  to 
appear  towards  the  end  of  the  first  month;  and  it  is  in  the  course  of  the  seventh  week, 
that  the  true  Kidneys  first  present  themselves.  From  the  beginning  of  the  third  month  the 
diminution  in  the  size  of  the  Wolffian  bodies  goes  onparipassu  With  the  increase  of  the  Kidneys; 
and  at  the  time  of  birth  scarcely  any  traces  of  them  can  be  found.  At  the  end  of  the  third 


54 


See  Principles  of  General  and  Comparative  Physiology,  §  659. 


638  OF  SECRETION. 

month,  the  kidneys  consist  of  seven  or  eight  lobes,  the  future  pyramids;  their  excretory 
ducts  still  terminate  in  the  same  canal,  which  receives  those  of  the  Wolffian  bodies  and  of 
the  sexual  organs;  and  this  opens,  with  the  rectum,  into  a  sort  of  cloaca,  or  sinus  urogeni- 
talis,  analogous  to  that  which  is  permanent  in  the  oviparous  Vertebrata.  The  Kidneys  are 
at  this  time  covered  by  the  Supra-Renal  Capsules,  which  are  very  large ;  about  the  sixth 
month,  however,  these  have  decreased,  whilst  the  kidneys  have  increased,  so  that  their  pro- 
portional weight  is  as  1  to  4£.  At  birth  the  weight  of  the  Kidneys  is  about  three  times 
that  of  the  Supra-Renal  Capsules;  and  they  bear  to  the  whole  body  the  proportion. of  1  to 
SO;  in  the  adult,  however,  they  are  no  more  than  1  to  240.  The  Corpora  Wolffiana  are, 
when  at  their  greatest  development,  the  most  vascular  parts  of  the  body  next  to  the  liver; 
four  or  five  branches  from  the"  aorta  are  distributed  to  each,  and  two  veins  are  returned  from 
each  to  the  vena  cava.  The  upper  veins  and  their  corresponding  arteries  are  converted 
into  the  Renal  or  emulgent  vessels;  and  the  lower  into  Spermatic  vessels.  The  lobulated 
appearance  of  the  kidney  gradually  disappears ;  partly  in  consequence  of  the  condensation 
of  the  areolar  tissue,  which  connects  the  different  parts;  and  partly  through  the  develop- 
ment of  additional  tubuli  in  the  interstices.  The  Urinary  Bladder  is  formed  quite  inde- 
pendently of  the  secreting  apparatus,  being  a  part  of  the  allantois,  which  is  first  developed 
as  a  large  coscum  or  diverticulum  from  the  lower  extremity  of  the  alimentary  canal  (Chap. 
XYII.).  The  part  of  the  tube  below  this  forms  the  Cloaca,  or  common  termination  of  the 
intestinal  and  vesical  apparatus.  The  sides  of  this  cloaca,  however,  gradually  approach 
one  another,  so  as  to  form  a  transverse  partition,  which  separates  the  Rectum  from  the 
Genito-urinary  canal ;  and  the  urethra  of  the  female  is  afterwards  separated  from  the  Vagina 
by  a  similar  process. 

840.  The  researches  of  Mr.  Bowman  on  the  structure  of  the  Malpighian 
bodies,  and  on  the  vascular  apparatus  of  the  Kidney,  have  thrown  great  light 
upon  the  mode  in  which  the  Urinary  secretion  is  elaborated.  §  One  of  the 
most  remarkable  circumstances  attending  this  excretion,  in  the  Mammalia 
particularly,  is  the  large  but  variable  quantity  of  water,  which  i§  thus  got  rid 
of,— the  amount  of  which  bears  no  constant  proportion  to  that  of  the  solid 
matter  dissolved  in  it.  The  Kidneys,  in  fact,  seem  to  form  a  kind  of  regu- 
lating valve,  by  which  the  quantity  of  water  in  the  system  is  kept  to  its  proper 
amount.  The  Exhalation  from  the  Skin,  which  is  the  other  principal  means 
of  removing  the  superfluous  liquid  from  the  blood,  is  liable  to  great  variations, 
from  the  temperature  of  the  air  around  (§  870) :  hence,  if  there  were  not  some 
other  means  of  adjusting  the  quantity  of  fluid  in  the  Blood-vessels,  it  would 
be  liable  to  continual  and  very  injurious  variation.  This  important  function 
is  performed  by  the  Kidneys ;  which  allow  such  a  quantity  of  water  to  pass 
into  the  urinary  tubes,  as  may  keep  the  pressure  within  the  vessels  nearly  at 
a  uniform  standard.  The  quantity  of  water  which  is  passed  off  by  the  kid- 
neys, therefore,  will  depend  in  part  upon  that  exhaled  by  the  Skin;  being 
greatest  when  this  is  least,  and  vice  versa:  but  the  quantity  of  solid  matter  to 
be.  conveyed  away  in  the  secretion  has  little  to  do  with  this ;  being  dependent 
upon  the  amount  of  waste  in  the  system,  and  upon  the  quantity  of  surplus 
azotized  aliment  which  has  to  be  discharged  through  the  channel. — The  Kid- 
ney contains  two  very  distinct  provisions  for  these  purposes.  The  cells  lining 
the  Tubuli  Uriniferi  are  probably  here,  as  elsewhere,  the  instruments  by  which 
the  solid  matter  of  the  secretion  is  elaborated ;  whilst  it  can  scarcely  be  doubted 
that  the  office  of  the  Corpora  Malpighiana  is  to  allow  the  transudation  of  the 
superfluous  fluid  through  the  thin-walled  and  naked  capillaries  of  which  they 
are  composed.  "It  would,  indeed,"  Mr.  Bowman  remarks,  "  be  difficult  to 
conceive  a  disposition  of  parts  more  calculated  to  favour  the  escape  of  water 
from  the  blood,  than  that  of  the  Malpighian  body.  A  large  artery  breaks  up 
in  a  very  direct  manner  into  a  number  of  minute  branches;  each  of  which 
suddenly  opens  into  an  assemblage  of  vessels  of  far  greater  aggregate  capacity 
than  itself,  and  from  which  there  is  but  one  narrow  exit.  Hence  must  arise 
a  very  abrupt  retardation  in  the  velocity  of  the  current  of  blood.  The  vessels 
in  which  this  delay  occurs  are  uncovered  by  any  structure.  They  lie  bare  in 
a  cell,  from  which  there  is  but  one  outlet,  the  orifice  of  the  tube.  This  orifice 


THE  KIDNEYS SECRETION  OF  URINE.  639 

is  encircled  by  cilia,  in  active  motion,  directing  a  current  towards  the  tube. 
These  exquisite  organs  must  not  only  serve  to  carry  forward  the  fluid  which 
is  already  in  the  cell,  and  in  which  the  vascular  tuft  is  bathed;  but  must  tend 
to  remove  pressure  from  the  free  surface  of  the  vessels,  and  so  to  encourage 
the  escape  of  their  more  fluid  contents." 

841.  There  is  a  striking  analogy  between  the  mode  in  which  the  Tubuli 
Uriniferi  are  supplied  with  Blood,  for  the  purpose  of  elaborating  their  secre- 
tion, and  the  plan    on   which  the  Hepatic  circulation   is  carried  on.     The 
secretion  of  the  Liver  is  formed  from  blood  conveyed  to  it  by  one  large  vessel, 
the  Vena  Portae,  which  has  collected  it  from  the  Venous  capillaries  of  the 
ehylopoietic  viscera,  and  which  subdivides  again  to  distribute  it  through  the 
liver.     The  secretion  of  the  Kidney,  in  like  manner,  is  elaborated  from  blood 
which  has  already  passed  through  one  set  of  capillary  vessels, — those  of  the 
Malpighian  tufts ;  this  blood  is  collected  and  conveyed  to  the  proper  secreting 
surface,  not  by  one  large  trunk  (which  would  have  been  a  very  inconvenient 
arrangement),  but  by  a  multitude  of  small  ones, — the  efferent  vessels  of  the 
Malpighian   bodies,  which  may  be  regarded  as  collectively  representing  the 
Vena  Portae,  since  they  convey  the  blood  from  the  systemic  to  the  secreting 
capillaries.     Hence  the  Kidney  may  be  said  to  have  a  portal  system  within 
itself. — This  ingenious  view  of  Mr.  Bowman's  finds  support  from  jthe  fact, 
that  in  Reptiles  (in  which,  as  in  Fishes,  the  Portal  trunk  receives  the  blood 
from  the  whole  posterior  part. of  the  body,  and  supplies  the  Kidneys  as  well 
as  the  Liver),  the  efferent  vessels  of  the  Malpighian   bodies — which  receive 
their  blood,  as  elsewhere,  from  the  Renal  Artery — unite  with   the  branches 
of  the  Portal  vein,  to  form  the  secreting  plexus  around  the  Tubuli  Uriniferi. 
Here,  therefore,  the  blood  of  the  secreting  plexus  has  a  double  source;  the 
vessels  which  supply  it  receiving  their  blood  in  part  from  the  capillaries  of  the 
organ  itself,  and  in  part  from  those  of  viscera  external  to  it;  just  as,  in  the 
Liver,  the  secreting  plexus  is  supplied  in  part  by  the  blood  conveyed  from  the 
chylopoietic   viscera  through   the   Vena  Portae,  and  in  part  by  the  nutritive 
capillaries  of  the  organ  itself,  which  receive  their  blood  from  the  Hepatic 
Artery. 

842.  The  nature  and  purposes  of  the  Urinary  secretion,  and  the  alterations 
which  it  is  liable  to  undergo  in  various   conditions  of  the  system,  are  much 
better  understood  than  are  those  of  the  Bile ;  this  is  owing,  in  great  part,  to 
the  circumstance,  that  it  may  be   readily  collected  in  a  state  of  purity  ;  and 
that  its  ingredients  are  of  such  a  nature,  as  to  be  easily  and  definitely  sepa- 
rated from  each  other  by  simple  chemical  means.     There  can  be  no  doubt 
that  the  chief  purpose  of  this  excretion,  is  to  remove  from  the  system  the  effete 
azotized  matters  which  the  blood  takes  up  in  the  course  of  the  circulation,  or 
which  may  have  been  produced' by  changes  occurring  in  itself.     This  is  evi- 
dent from  -the  large  proportion  of  Nitrogen  which  is  contained  in  the  solid 
matter  dissolved  in  it ;  and  from  the  crystalline  form  presented  by  this  solid 
matter  when  separated, — a  form  which  indicates  that  its  state  of  combination 
is  such,  as  to  prevent  it  from  conducing  to  the  nutrition  of  the  system.     The 
injurious  effects  of  the  retention  in  the  Blood,  of  the  components  of  the  Uri- 
nary secretion,  are  fully  demonstrated  by  the  results  of  its  cessation ;  whether 
this  be  made  to  take  place  experimentally  (as  by  tying  the  renal  artery),  or  be 
the  consequence  of  a  disordered  condition  of  the  kidney.     Symptoms  of  great 
disorder  of  the  nervous  centres,  analogous  to  those  produced  by  many  narcotic 
poisons,  soon  exhibit  themselves ;  and  the  patient  dies  comatose,  if  the  secre- 
tion be  not  restored.     In  such  cases,  Urea  (the  characteristic  ingredient  of  the 
urine)  is  found  to  have  accumulated  in  the  Blood  ;  and  it  may  even  be  detected 
by  the  smell,  in  the  fluid  effused  into  the  Ventricles  of  the  Brain.     The  con- 
clusion which  may  be  drawn  from  this  circumstance,  regarding  the  pre-exist- 


640  OF  SECRETION. 

ence  of  the  components  of  the  secretion  in  the  Blood,  is  strengthened  by  the 
fact  that,  even  in  the  healthy  state,  Urea  may  be  detected  in  the  blood  ;  it  only 
exists  there  normally,  however,  in  very  small  quantity ;  but,-  when  there  is 
any  impediment  to  its  excretion,  it  goes  on  accumulating,  and  produces  conse- 
quences more  or  less  serious  in  proportion  to  its  amount.  It  is  not  improba- 
ble that,  as  in  the  case  of  the  retention  of  Bile  in  the  Blood  (§  832),  many  of 
the  minor  as  well  as  of  the  severer  forms  of  sympathetic  disturbance,  connected 
with  disordered  secretion  from  the  Kidney,  are  due  to  the  directly  poisonous 
operation  of  the  elements  of  the  Urine,  upon  the  several  organs  whose  func- 
tion is  disturbed ;  and  that  many  complaints,  in  which  no  such  agency  has 
been  until  recently  suspected, — especially  Convulsive  affections  arising  from 
a  disordered  action  of  the  Nervous  centres, — are  due  to  the  insufficient  elimi- 
nation of  Urea  from  the  Blood. 

843.  In  order  to  form  a  correct  opinion  of  the  state  of  the  Urinary  secretion 
in  morbid  conditions  of  the  system,  it  is  desirable  to  be  acquainted  with  every 
leading  particular  regarding  its  healthy  characters. — The  average  Quantity, 
during  24  hours,  has  been  variously  estimated :  it  differs,  of  course,  with  the 
amount  of  fluid  ingested,  and  it  is  influenced  also  by  the  external  temperature, 
— a  much  smaller  amount  of  the  superfluous  fluid  of  the  body  being  set  free 
from  the  skin  in  winter  than  in  summer,  and  a  larger  proportion  being  carried 
off  by  the  kidneys.     Probably  we  shall  be  pretty  near  the  truth,  in  estimating 
the  amount  at  from  about  30  oz.  in  sunimer,  to  40  oz.  in  winter,  for  a  person 
who  does  not  drink  more   than  the   simple  wants  of  nature  require. — The 
Specific  Gravity  comes  to  be  a  very  important  character,  in  various  morbid 
conditions  of  the  urine  :  and  it  is  therefore  desirable  to  estimate  it  correctly. 
This  also  is,  of  course,  liable  to  the  same  causes  of  variation ;  since,  when 
the  same  amount  of  solid  matter  is  dissolved  in  a  larger  or  smaller  quantity  of 
water,  the  specific  gravity  will  be   proportionably  lower  OF  higher.     The 
average,  according  to  Dr.  Prout,  in  a  healthy  person,  taking  the  whole  year 
round,  is  about  1020;  the  standard  rising  in  summer  (on  account  of  the  greater 
discharge  of  fluid  by  perspiration)  to  1025 ;  and  being  lowered  in  winter  to 
1015.     Simon,  however,  states  the  average  specific  gravity  at  no  more  than 
1012.     It  will  depend,  in  each  individual  case,  upon  the  amount  of  fluid  habitu- 
ally ingested,  as  compared  with  that  dissipated  by  cutaneous  exhalation;  and 
it  will  also  vary  with  the  period  that  has  elapsed  since  the  last  introduction  of 
liquid  into  the  stomach.     From  these  and  other  causes,  the  proportion  of  solid 
matter  in  1000  parts  of  Urine  may  vary  from  20  to  70.     The  following  table 
expresses  the  relative  amounts  of  the  different  components,  in  every  100  parts 
of  this  solid  matter;  according  to  the  analyses  of  different  Chemists. 

Berzelius.  Lehmann.  Simon.  Marchand. 

Urea .         .  45-10  49'68  33-80  48-91 

Uric  Acid 1-50  1'61  1-40  1'59 

Extractive  matter,  Ammonia-salts,  )  36.3Q  2g.95  -  42W  32<49 

and  Chloride  of  sodium  $ 

Alkaline  Sulphates                   .         .         .         .     .  10-30  11-58  8-14  10-18 

Alkaline  Phosphates            .         .         .         .         .       6'88  f  5-96  6-50  .  4-57 

Phosphates  of  Lime  and  Magnesia         .         .     .       1'50  1-97  1-59  1-81 

We  shall  presently  find  the  causes  of  some  of  these  variations  in  the  nature 
of  the  ingesta,  and  in  the  amount  of  exercise  taken  by  the  individual. — The 
Urine  in  health  usually  exhibits  an  acid  reaction;  this  depends,  however, 
upon  certain  conditions  furnished  by  the  aliment;  and  may  be  altered  (as  will 
presently  appear)  by  a  change  in  the  ingesta. 

844.  The  most  important  of  the  above  ingredients  (constituting  from  one- 
third  to  one-half  of  the  whole  solid  matters  of  the  Urine)  is  evidently  that 
\vhich,  from  its  being  the  principal  cause  of  the  characteristic  properties  of  the 


SECRETION  OF  URINE. 


641 


secretion,  is  termed  Urea.  This  maybe  readily  separated  from  Urine,  in  the 
form  of  transparent  colourless  crystals ;  which  have  a  faint  and  peculiar,  but 
not  urinous  odour:  and,  as  already  mentioned,  it  is  distinctly  traceable  in  the 
Blood,  where  it  rapidly  accumulates,  if  its  continual  elimination  be  in  any  way 
interfered  with.  It  is  very  soluble  in  water,  and  combines  with  acids  without 
neutralizing  them.  In  its  chemical  composition,  it  is  identical  with  cyanate 
of  ammonia;  this  composition  being  2  Carbon,  4  Hydrogen,  2  Nitrogen,  and 
2  Oxygen, — a  formula  much  more  simple  than  that  of  almost  any  other 
organic  substance.  The  amount  of  Urea  excreted  in  twenty-four  hours  has 
been  made  the  subject  of  examination  by  Lecanu  ;*  and  the  following  are  his 
results,  as  deduced  from  a  series  of  120  analyses : — 


Minimum. 
.     357-51  grs 

By  women     '.         .         .... 
By  old  men  (84  to  86  years) 
By  children  of  eight  years 
By  children  of  four  years    . 

.     .     153-25 

61-08 
.     .     161-78 
.       57-28 

Mean. 

433-13  grs. 
295-15 
125-22 
207-99 

69-55 


Maximum. 
510-36  grs. 
437-06 
295-15 
254-20 
81-83 


It  is  very  interesting  to  perceive,  in  this  table,  how  large  an  amount  of  Urea 
is  excreted  by  children  ;  and  how  small  a  quantity,  in  proportion  to  their  bulk, 
by  old  men.  This  corresponds  precisely  with  the  rapidity  of  interstitial 
change  at  different  periods  of  life.  (See  §  812.)  Moreover,  as  this  continual 
disintegration  is  very  much  accelerated  by  increased  vital  activity  of  the  Tis- 
sues, the  amount  of  Urea  undergoes  a  like  augmentation ;  so  that — other  cir- 
cumstances being  equal — the  amount  of  Urea  excreted  may  fairly  serve  as  a 
measure  of  the  waste  of  the  tissues,  and  consequently  of  the  degree  in  which 
they  have  been  exercised.  This  will  be  especially  the  case  in  regard  to  the 
Muscular  Tissue  ;  which  constitutes  so  large  a  part  of  the  fabric.  In  some 
experiments  recently  made  on  the  influence  of  various  causes  upon  the  con- 
stitution of  Urine,  Dr.  Lehmann  found  that,  by  the  substitution  of  violent  for 
moderate  exercise,  the  quantity  of  Urea  was  raised  from  32s  to  45 £  parts ; 
and  Simon  found  that,  by  two  hours'  violent  exercise,  the  proportion  of  the 
urea  in  the  urine  passed  half  an  hour  subsequently  was  double  that  contained 
in  the  morning  urine.  If  such  increased  waste  be  not  compensated  by  in- 
creased nutrition,  a  diminution  in  the  bulk  of  the  body  is  the  necessary  con- 
sequence. 

845.  The  next  important  ingredient,  Uric  or  Lithic  Acid,  exists  much 
more  largely  in  the  Urine  of  the  lower  Vertebrata,  than  in  that  of  Mammalia; 
thus  the  nearly  solid  urinary  excretion  of  Serpents,  and  the  semi-fluid  urine 
of  Birds,  is  almost  entirely  composed  of  this  acid,  in  combination  with  Am- 
monia. Its  presence  has  not  yet  been  detected  in  healthy  blood;  but  when 
it  is  imperfectly  eliminated,  we  are  assured  of  its  accumulation  in  the  circu- 
lating fluid,  by  its  deposition,  in  combination  with  Soda,  in  the  neighbourhood 
of  the  joints, — formingfGrouty  concretions,  or  Chalk-stones.  Pure  Lithic  acid 
crystallizes  in  fine  scales  of  a  brilliant  white  colour,  and  silky  lustre  ;  it  is 
tasteless  and  inodorous,  and  is  so  sparingly  soluble  in  water,  that  at  least 
10,000  times  its  own  weight  is  required  to  dissolve  it.  As  it  exists  in  a  state 
of  perfect  solution  in  healthy  Urine,  it  must  be  in  combination  with  some 
base;  and  that  this  is  the  case,  is  at  once  proved  by  the  fact,  that  it  is  precipi- 
tated immediately  on  the  addition  of  a  small  quantity  of  any  acid,  even  the 
Carbonic.  It  is  generally  believed,  that  the  base  is  Ammonia ;  but  it  has 
recently  been  affirmed  by  Liebig,t  that  the  Uric  acid  (with  the  Hippuric)  is 
held  in  solution  by  the  Phosphate  of  Soda, — which,  from  being  bibasic  or 
alkaline,  is  rendered  acid,  by  yielding  up  a  part  of  its  soda  to  these  organic 


Journal  de  Pharmacie,  torn.  xxv. 


f  Lancet,  June  8,  1844. 


54* 


642  OF  SECRETION. 

acids,  which  are  thereby  rendered  soluble.  It  is  in  this  manner  that  he  partly 
explains, the  usually  acid  reaction  of  healthy  urine  ;  the  other  causes  of  which 
will  be  presently  noticed. — If  there  be  an  undue  proportion  of  Lithic  acid  in 
the  urine,  it  will  be  precipitated  on  cooling ;  because  it  is  less  soluble  in  a 
cold  than  in  a  warm  solution  of  phosphate  of  soda ;  and  the  same  result  will 
happen,  if  there  be  a  predominance  of  other  acids  in  the  urine,  which  will 
seize  upon  its  base,  as  soon  as  its  own  affinity  for  it  is  diminished  by  the 
lowering  of  its  temperature.  By  Dr.  Prout  it  is  believed  that  Lactic  acid,  ex- 
isting in  the  Blood  or  in  the  Urine  in  excess,  is  an  ordinary  source  of  this 
deposit ;  but  the  presence  of  this  acid  is  altogether  denied  by  Liebig  (§  846). 
— The  composition  of  Lithic  Acid  is  as  follows: — 10  Carbon,  4  Hydrogen, 
4  Nitrogen,  6  Oxygen.  The  amount  of  it  usually  excreted  in  the  Urine  of 
Man  is  but  very  small;  it  is  occasionally,  however,  considerably  increased; 
but  the  circumstances  under  which  this  increase  takes  place  have  not  yet  been 
exactly  determined. 

a.  Uric  acid  is  replaced  in  the  Herbivorous  animals  by  the  Hippuric ;  the  composition  and 
properties  of  which  are  very  different  from  those  presented  by  that  substance.     When  pure, 
it  forms  long  transparent  four-sided  prisms;  it  is  soluble  in  400  parts  of  cold  water,  and  dis- 
solves readily  at  a  boiling  heat ;  and  it  has  a  strong  acid  reaction,  and  bitterish  taste.     Its 
formula  is  18  Carbon,  8  Hydrogen,  1  Nitrogen,  and  5  Oxygen,  with  1  equiv.  of  Water.     It 
has  very  curious  relations  with  Benzoic  acid ;  which  it  yields,  together  with  Benzoate  of 
Ammonia,  when  acted  upon  by  a  high  temperature,  or  during  the  putrefaction  of  the  urine 
of  which  it  forms  a  part.     According  to  Liebig,  the  Hippuric  acid  in  the  urine  of  the  Horse 
and  Ox  is  replaced  by  Benzoic  acid,  when  the  animal  is  subjected  to  hard  labour. — It  appears 
from  his  recent  experiments,*  that  we  are  to  regard  Hippuric  acid  as  a  normal  element  of 
Human  urine;  for  he  has  detected  Benzoic  acid  among  the  products  of  its  putrefaction;  and 
as  we  know  that  the  latter  does  not  exist  in  the  Urine  of  Man,  and  as  there  is  no  other  sub- 
stance at  the  expense  of  which  it  can  be  formed  during  the  putrefactive  process,  we  can 
scarcely  hesitate  to  admit  that  such  must  be  the  case.     It  is  a  very  curious  fact,  that  the  intro- 
duction of  Benzoic  acid  into  the  system  causes  a  large  increase  in  the  amount  of  Hippuric 
acid  in  the  Urine ;  and  if  this  be  formed  at  the  expense  of  the  elements,  which  would  other- 
wise have  produced  Uric  acid,  an  easy  method  is  pointed  out  for  the  elimination  of  the  latter 
substance  from  the  blood,  when  it  has  accumulated  there,- — the  salts  of  Hippuric  acid  being 
so  much  more  soluble  than  those  of  the  Uric.     According  to  Keller,")"  whose  experiments 
were  made  upon  himself,  both  Urea  and  Uric  acid  existed  in  normal  quantity  in  his  urine, 
though  a  large  quantity  of  Hippuric  acid  was  being  excreted ;  whilst  Mr.  Alexander  Ure 
states,J  that  he  has  succeeded,  by  the  administration  of  Benzoic  acid,  in  preventing  the  de- 
position of  Gouty  concretipns,  and  even  in  removing  them  when  they  had  been  formed. 

b.  Many  remarkable  changes  are  effected  in  Lithic  acid,  by  the  operation  of  other  chemi- 
cal agents ;  and  these  changes  are  very  important,  in  their  bearing  on  pathological  conditions 
of  the  Urine.     When  Uric  acid  is  subjected  to  the  action  of  Oxygen,  it  is  first  resolved  into 
Urea  and  a  compound  termed  JLlloxan.     Now  this  Alloxan,  when  acted  on  by  a  new  supply 
of  Oxygen,  is  resolved  into  Urea  and  Oxalic  acid ;  or,  with  a  still  further  amount  of  Oxygen, 
into  Urea  and  Carbonic  acid : — a  fact,  which  has  a  very  important  bearing  on  the  production 
of  Calculi  composed  of  Uric  and  Oxalic  acids,  and  which  explains  the  remarkable  alterna- 
tions which  are  often  observed  in  the  layers  of  these  concretions.     It  is  affirmed  by  Liebig, 
that  the  calculi  which  are  composed  of  Urate  of  Ammonia,  or  of  Oxalate  of  Lime,  occur  in 
persons,  in  whom,  from  want  of  exercise,  or  from  other  causes,  Ae  quantity  of  Oxygen  intro- 
duced into  the  system  is  beneath  what  it  ought  to  be.     When  patients  suffering  under  Uric 
acid  Calculi  take  more  exercise,  the  Urates  are  replaced  by  Oxalates,  in  consequence  of  the 
larger  amount  of  Oxygen  introduced  into  the  system ;  and  if  the  oxygenation  could  be  carried 
still  further,  the  latter  would  cease  to  be  deposited,  their  elements  passing  off  in  the  form  of 
Urea  and  Carbonic  acid.     These  views  are  borne  out  by  the  results  of  Lehmann's  experi- 
ments upon  himself;  for  he  found  that  the  violent  exercise,  which  raised  the  proportion  of 
Urea  in  the  urine  by  more  than  one-third  (§  844)  brought  down  the  amount  of  Uric  acid 
from  1-18  to  -642,  or  nearly  one-half. 

c.  Another  change  is  that  which  gives  rise  to  the  peculiar  compound  termed  Attantoin; 
which  naturally  exists  in  the  fluid  of  the  Allantois  of  the  fetal  calf.     This  may  be  formed 
artificially  by  boiling  Uric  acid  with  peroxide  of  lead ;  from  which  process  there  result  an 

*  Loc.  cit.  f  Liebig's  Animal  Chemistry,  p.  327. 

J  Medico-Chirurgical  Transactions,  vol.  xxiv. 


SECRETION  OF  URINE.  643 

Oxalate  of  the  protoxide  of  lead,  Urea  and  Allantoin ;  the  composition  of  which  last  substance 
is  very  different  from  that  of  urea  or  uric  acid,  being  8  Carbon,  5  Hydrogen,  4  Nitrogen,  and 
5  Oxygen. 

d.  By  the  operation  of  Nitric  Acid  upon  Uric  acid,  several  new  products  are  generated, 
some  of  which  are  of  much  practical  interest.  To  one  of  these  the  name  of  Murexid  has 
been  given,  on  account  of  its  reddish  purple  colour  (resembling  that  of  the  Tyrian  dye  which 
was  obtained  from  a  species  of  Murex) ;  this  is  a  crystalline  substance,  sparingly  soluble  in 
cold  water,  but  copiously  soluble  in  warm,  imparting  to  it  its  vivid  colour.  By  Dr.  Prout  it 
was  long  since  described  as  consisting  of  a  peculiar  acid,  the  Purpuric,  in  combination  with 
Ammonia;  this  view  of  its  composition  is  not  generally  received  by  German  Chemists ;  but 
it  has  lately  been  supported  by  Fritzche,  who  has  shown  the  real  existence  of  the  acid,  by 
obtaining  Purpurates  of  other  bases.  This  substance  is  one  source  of  the  colours  of  the 
pink  and  lateritious  sediments  which  so  often  present  themselves  in  the  Urine  ;  these  hues 
partly  depend,  however,  on  the  influence  of  nitric  acid  upon  the  peculiar  Colouring  princi- 
ples of  the  urine,  the  nature  of  which  principles  is  not  yet  fully  understood. 

846.  It  was  supposed  until  recently,  that  Lactic  acid  is  a  normal  constitu- 
ent of  Human  Urine.     It  appears  to  have  been  demonstrated  by  the  experi- 
ments of  Liebig,  however,  that  this  is  not  the  case  ;  and  that  another  organic 
substance,  which  forms  a  crystalline  compound  with  zinc,  very  similar  to  the 
lactate,  has  been  mistaken  for  it.     The  composition  of  this  substance,  which 
usually  forms  about  one  part  in  200  of  Urine,  has  been  recently  determined 
to  be  8  Carbon,  8  Hydrogen,  3  Nitrogen,  and  3  Oxygen.     It  thus  differs  from 
Lactic  acid  in  containing  Nitrogen ;  as  well  as  in  proportion  of  its  other  com- 
ponents. 

847.  It  has  been  shown   (§  843),  that  the  Urine  contains  a  considerable 
amount  of  Saline  matter;  the  excretion  of  which  from  the  system  appears  to 
be   one  of  the  principal  offices  of  the  Kidney.     Various  saline  compounds, 
and  the  bases  of  others,  are  being  continually  introduced  with  the  food  (§  648) ; 
and  these,  after  performing  their  part  in  the  organism,  must  be  eliminated  from 
the  circulating  fluid,  in  order  to  prevent  injurious   accumulation.     Of  these 
we  shall  now  examine  the  chief  sources. — The  mode  in  which  the  Muriates 
find  their  way  into  the  Urine  is  easily  understood.     Of  the  Common  Salt  in- 
gested, a  considerable  part  is  decomposed  into  Muriatic  Acid  and  Soda ;  the 
former  being  found  uncombined  in  the  Gastric  juice  ;  and  the  latter  in  the  Bile. 
By  the  mixture  of  the  Bile  with  the  Chyme,  a  re-union  of  these  two  consti- 
tuents takes  place ;  and  Salt  is  again  formed,  which  is  received  into  the  Cir- 
culation that  it  may  be  eliminated  (its  part  in  the  economy  having  been  now  per- 
formed) by  the  Kidney. — The  quantity  of  the  Sulphates  present  in  the  Urine, 
appears  to  have  no  relation  with  that  of  the  amount  of  Sulphuric  acid  ingested  ; 
for  it  much  surpasses  what  could  be  thus  accounted  for, — being  often  consi- 
derable, when  no  Sulphate  whatever  can  be  detected  in  the  food.     But  most 
of  the  azotized  compounds  employed  as  food  have  Sulphur  in  combination 
with  them ;  and  there  can  be  no  doubt,  that  this  undergoes  oxidation  within 
the  system,  and  thus  generates   Sulphuric  acid,  which  unites  with  any  free 
or  weakly-combined  bases  it  may  meet  with,  to  form  the  Sulphates  present  in 
the  Urine. — The  Phosphates  are  probably  derived  in  part  from  the  Phos- 
phates taken  in  with  the  food,  and  in  part  from  the  free  Phosphorus,  which 
its  elements  contain.     Of  the  latter,  great  use  is  made  in  the  production  of 
Nervous  matter  (§249) ;  the  continual  waste  of  which  must  set  it  free  again. 
When  thus  set  free,  there  is  obviously  no  channel  for  its  elimination,  save  by 
its  conversion  into  Phosphoric  acid,  and  its  union  with  an  alkaline  base.* 
That  this  is  really  the  case,  would  appear  from  the  fact  noticed  by  Dr.  Prout, 
and  confirmed  by  many  others, — that  mental  or  bodily  labour  which  involves 

*  This  circumstance  has  been  entirely  overlooked  by  Liebig,  in  his  late  discussion  (he. 
cit.)  of  the  Constitution  of  the  Urine;  the  Phosphates  being  regarded  by  him  as  having  their 
sole  origin  in  the  Phosphates  of  the  ingesta. 


644  OF  SECRETION. 

much  waste  of  the  Nervous  System,  is  followed  by  an  increase  in  the  quan- 
tity of  the  alkaline  Phosphates  in  the  Urine  (§  295).  This  increase  cannot 
proceed  from  the  waste  of  the  Muscular  system  ;  for  this  would  set  free 
Phosphate  of  Lime,  which  chiefly  passes  off  by  the  faeces. 

848.  The  alkaline  or  acid  reaction  of  the  Urine,  therefore,  will  not  only 
depend  upon  the  quantity  of  alkaline  Phosphates  converted  into  acid  Phos- 
phates by  the  Uric  and  Hippuric  acids  (§  845) ;  but  also  upon  the  amount  of 
the  bases  in  the  ingesta,  compared  with  that  of  the  permanent  Acids  intro- 
duced into  the  system  or  generated  within  it.     The  Urine  of  animals  which 
live   chiefly  or  entirely  upon  Vegetable  food,  is  almost  invariably  alkaline; 
because  this  food  contains  a  large  quantity  of  alkaline  bases,  in  combination 
with  Citric,  Tartaric,  Oxalic,  and  other  acids,  which  are  decomposed  within 
the  system ;  and  the  amount  of  Sulphuric  and  Phosphoric  acids  produced  is 
not  sufficient  to  neutralize  them.     On  the  other  hand,  the  food  of  Carnivo- 
rous animals  contains  no  free  or  weakly-combined  bases  ;  and  as  its  Sulphur 
and  Phosphorus,  when  oxidized  in  the  system,  produce  a  considerable  quan- 
tity of  free  acids,  which  share  the  bases  with  the  Muriatic  acid  already  there, 
the  Urine  must  necessarily  have  an  acid  reaction.     The  character  of  the 
Urine  of  Man,  in  this  respect,  is  considered  by  Liebig  to  depend  entirely  upon 
that  of  the  food  ingested. 

a."  Proceeding  upon  his  determination  that  no  Lactic  acid  is  ever  present  in  the  Urine,  he 
remarks :  "  The  acid,  neutral,  or  alkaline  reaction  of  Urine  of  healthy  individuals,  does  not 
depend  on  any  difference  in  the  processes  of  digestion,  respiration,  or  secretion,,  in  the  va- 
rious classes  of  animals,  but  upon  the  constitution  of  the  aliments,  and  upon  the  alkaline 
bases  which  enter  the  organism  through  the  medium  of  these  aliments.  If  the  amount  of 
these  bases  is  sufficiently  large  to  neutralize  the  acids  formed  in  the  organism,  or  supplied 
by  the  aliments,  the  urine  is  neutral ;  whilst  it  manifests  an  alkaline  reaction,  when  the 
amount  of  alkaline  bases  thus  supplied  to  the  organism  is  more  than  sufficient  to  neu- 
tralize the  acids;  but  in  all  these  cases,  the  urine  accords  with  the  nature  of  the  aliments 
taken."  The  varying  amount  of  Uric  Acid, — which,  on  Prof.  Xiebig's  own  showing,  is  very 
much  influenced  by  the  respiration, — is  altogether  left  out  of  consideration  in  this  sweeping 
generalization. 

849.  The  amount  of  Azotized  matter  in  the  Urine,  also,  is  greatly  influ- 
enced by  the  nature  of  the  food  ingested,  whilst  the  constitution  of  the  Ani- 
mal frame  remains  nearly  the  same ;  hence  it  appears,  that  a  certain  portion 
of  it  must  be  derived  from  the  unassimilated  materials  which  have  been  taken 
into  the  blood,  and  which,  being  superfluous,  are  injurious.     It  is  well  known 
that  the  ingestion  of  an  over-supply  of  azotized  matter  does  not  occasion  an 
increased  production  of  the  fibrinous  or  gelatinous  tissues ;  and  it  may  be 
hence  inferred  that,  as   there  is  no  means  by  which  the  superfluous  amount 
can  be  stored  up  in  the  system  (in  the  mode  that  non-azotized  matter  is  stored 
up  as  Fat),  it  must  be  continually  eliminated  from  the  Blood.     And  there  can 
be  no  doubt  that  the  Kidneys  are  the  principal  channel  by  which  this  is  ef- 
fected ;  the  amount  of  azote  thrown  off  in  a  given  time,  in  the  various  com- 
pounds which  they  excrete,  being   equal  to   10-llths  of  the  whole   quantity 
ingested. — The  following  are  the  results  of  the  most  satisfactory  inquiries 
that  have  yet  been  made,  in  regard  to  the  influence  of  various   kinds  of  Ali- 
ment upon  the  amount  of  the  solid  matters  in  the  Urine.     These  experiments 
were  performed  by  Dr.  Lehmann  of  Leipsig,  upon  himself.    In  the  first  series, 
Dr.  L.  adopted  an  ordinary  mixed  diet ;  but  he  took  no  more  solid  or  liquid 
aliment  than  was  needed  to  appease  hunger  or  thirst,  and  abstained  from  fer- 
mented drinks.     Every  two  hours  he  took  exercise  in  the  open  air,  but  he 
avoided  immoderate  exertion  of  every  kind.     The  average  result  of  the  exa- 
mination of  the  Urine  passed  under  these   circumstances,  for  fifteen  days,  is 
given  in  the  first  line  of  the  subsequent  Table. — In  a  second  series  of  experi- 
ments, Dr.  L.  lived  for  twelve  days  on  an  exclusively  Animal  diet ;  and  for 


SECRETION  OF  URINE.  645 

the  last  six  of  these,  it  consisted  solely  of  eggs.  He  took  32  eggs  daily ; 
which  contained  189*7  grammes  of  dry  albumen,  and  157*48  of  fatty  matters; 
or  about  228*75  grammes  of  carbon,  and  30*16  of  azote.  The  amount  of 
Urea  is  shown,  in  the  second  line  of  the  Table,  to  have  undergone  a  very 
large  increase  ;  and  it  contained  more  than  five-sixths  of  the  whole  azote  in- 
gested.— In  a  third  series  of  experiments,  Dr.  L.  lived  for  twelve  days  on  a 
Vegetable  diet ;  and  its  effect  upon  the  solid  matter  of  the  Urine  is  shown  in 
the  third  line  of  the  Table.— -In  a  fourth,  he  lived  for  two  days  upon  pure 
farinaceous  and  oleaginous  substances,  without  azotized  food  of  any  kind  ; 
and  the  azotized  matter  of  the  Urine  must,  therefore,  have  been  solely  the 
result  of  the  disintegration  of  the  tissues.  It  is  seen  to  undergo  a  very  marked 
diminution  under  this  regimen,  as  is  shown  in  the  fourth  line  of  the  Table. 
His  health  was  so  seriously  affected,  however,  by  this  diet,  that  he  was  una- 
ble to  continue  it  longer. 

Lactic  Acid  (?)  Extractive 
Solid  Matters.         Urea.  Uric  Acid,    and  Lactates.      Matters. 

I.  Mixed  diet         .  .  .  67-82  32-498  1-183  2*257  10-480 

II.  Animal  diet        .  .  .  87-44  53-198  1-478  2-167  5-145 

III.  Vegetable  diet    .  .  .  59-24  22-481  1-021  2-669  16-499 

IV.  Non-Azotized  diet  .  .  41-68  15-408  0-735  5-276  ,11-854 

850.  The  following  inferences  are  drawn  by  Dr.  Lehmann,  from  these 
experiments: — "  1.  Animal  articles  of  diet  augment  the  solid  matters  of  the 
Urine.  Vegetable  substances,  and  still  more  such  as  are  deprived  of  azote, 
on  the  contrary,  diminish  it. — 2.  Although  Azote  be  a  product  of  decomposi- 
tion of  the  organism,  yet  its  proportions  in  the  urine  depend  also  on  the  food, 
for  we  find  a  richly-azotized  diet  augment  considerably  the  quantity  of  Urea. 
In  the  above  experiments,  the  proportion  of  the  Urea  to  the  other  solid  mat- 
ters was  as  100  to  116  in  a  mixed  diet;  as  100  to  63  in  an  animal  diet;  as 
100  to  156  in  a  vegetable  diet;  and  as  100  to  170  in  a  non-azotized  diet. — 3. 
The  quantity  of  Uric  Acid  depends  less  on  the  nature  of  the  diet,  than  on 
other  circumstances  ;  the  differences  observed  in  it  being  too  slight  to  warrant 
us  in  ascribing  them  to  the  former  cause. — 4.  The  combinations  of  Proteine, 
and  consequently  the  azote  of  the  food,  are  absorbed  in  the  intestinal  canal ; 
and  what  is  not  employed  in  the  formation  of  the  tissues,  is  thrown  off  by 
the  Kidneys  in  the  form  of  Urea  or  Uric  acid, — these  organs  being  the  chief 
if  not  the  sole,  channel  through  which  the  system  frees  itself  of  its  excess  of 
azote. — 5.  The  urine  contains  quantities  of  Sulphates  and  Phosphates  pro- 
portional to  the  azotized  matters  which  have  been  absorbed  ;  and  the  propor- 
tion of  these  salts  is  sensibly  increased  under  the  use  of  a  large  amount  of 
those. — 6.  In  the  same  circumstances,  the  Extractive  matters  diminish,  while 
their  quantity  is  increased  by  the  use  of  vegetable  diet, — a  fact  which  proves 
the  influence  of  vegetable  aliment  over  the  production  of  these  matters  in  the 
urine. — 7.  Under  an  animal  diet,  the  quantity  of  Lactic  acid  diminishes  ;  but 
the  greater  part  of  this  acid  is  free.  It  is  the  reverse  under  a  vegetable  diet ; 
there  is  more  lactic  acid,  but  it  is  united  to  bases.  The  largest  production  of 
lactic  acid  is  under  a  non-azotized  diet ;  and  most  of  it  is  then  combined  with 
ammonia.  Therefore  the  lactic  acid  eliminated  with  the  urine,  is  in  great  part 
the  product  of  non-azotized  substances  not  entirely  assimilated;  but  it  results 
also  in  part  from  the  decomposition  of  the  azotized  substances  entering  into 
the  composition  of  the  body  and  the  food. — 8.  The  Kidneys  not  only  sepa- 
rate certain  constituent  parts  of  the  organs,  which  have  become  inadequate  for 
the  maintenance  of  life,  but  they  also  expel  the  superfluous  nutritive  matters 
that  may  have  been  absorbed."*  It  must  be  remarked,  with  regard  to  these 

*  L'Experience,  Dec.  7,  1843;  andEdinb.  Monthly  Journal,  March,  1844. 


646  OF  SECRETION. 

inferences,  that  the  statements  concerning  the  amount  of  Lactic  acid  and  the 
Lactates,  must  be  considered  as  invalidated  by  the  discoveries  of  Liebig  al- 
ready referred  to  (§  846).  The  most  unequivocal  facts  determined  by  Dr. 
Lehmann's  inquiries,  are  those  which  relate  to  the  influence  of  Diet  on  the 
amount  of  Urea  excreted.  The  experiments  upon  a  purely  non-azotized 
diet  were  not  continued  long  enough  for  a  satisfactory  result  to  be  obtained ; 
but  it  is  evident  that,  so  long  as  the  ingesta  contain  no  azote,  the  whole  of 
that  element  in  the  Urine  must  be  attributed  to  the  disintegration  or  waste  of 
the  tissues,  and  may  be  fairly  taken  as  a  measure  of  its  amount. 

851.  The  fact  of  the  pre-existence  of  the  chief  constituents  of  Urine  in  the 
Blood,  is  important  as  explaining  the  facility  with  which  the  secreting  function 
appears  to  be  transferred  to  other  membranes,  in  some  of  the  cases  in  which 
the  Kidney  does  not  perform  its  function.     Doubtless  there  has  been  much 
error  on  this  subject,  arising  out  of  deceptions  practised  by  impostors  ;  but  a 
sufficient  number  of  indubitably  genuine  cases  are  on  record,  to  put  it  beyond 
doubt  that  such  transferences  have  taken  place, — urinous  fluid  being  secreted 
from  the  stomach,  mammae,  umbilicus,  nose,  &c.* — On  the  other  hand,  the 
Kidney  may  serve  as  the  channel  for  the  elimination   of  substances  which 
are  usually  drawn  off  by  other  organs.     Thus,  when  the  secreting  action  of 
the  Liver  has  been  gradually  impaired  by  structural  disease,  the  Kidneys  ap- 
pear to  have  performed  its  function,  in  separating  some  (at  least)  of  the   ele- 
ments of  Bile.     And  a  case  has  recently  been  mentioned,  in  which  the  urine 
of  a  parturient  female,  who  did  not  suckle  her  infant,  was  found  to  contain  a 
considerable  amount  of  Butyric  acid,  during  several  days.     The  elimination 
of  Kiesteine  by  the  Kidney  during  pregnancy  will  be  presently  noticed  (§  859). 

852.  The  facility  with  which   substances   taken  into  the  current  of  the 
Circulation  pass  into  the  Urinary  secretion,  varies  extremely ;  and  no  general 
law  can  be  stated  in  regard  to  it.     It  appears  from  Wohler's  elaborate  re- 
searches on  this  subject,  that  the  salts  which  are  most  readily  excreted  are 
those  which  excite   the  action  of  the  kidneys.t     The  rapidity  with  which 
absorption  and  elimination  take  place  is  often  extremely  remarkable;  Frus- 
siate  of  Potash  having  been  detected  in  the  urine,  within  two  minutes  after  it 
had  been  introduced  into  the  stomach.     The  variations  in  this  respect  would 
appear  to  depend  chiefly  on  the  degree  of  concentration  of  the  saline  solution, 
which  will  affect  the  rapidity  of  its  absorption,  according  to  the  laws  of  En- 
dosmose ; — its  reception  into  the  blood  being  more  rapid,  in  proportion  as  its 
density  is  lower,  in  comparison  with  that  of  the  circulating  fluid.     Pure  water, 
or  water  containing  but  a  small  admixture  of  saline  matter,  is  readily  absorbed 
into  the  blood-vessels  of  the  Intestinal  villi ;  but  it  is  as  readily  drawn  off 
through  the  Kidneys  (by  the  agency,  as  it  would  seem,  of  the  Malpighian 
bodies,  §  840) ;  and  consequently  a  large  amount  may  be  ingested  in  a  short 
time.     But  if  the  water  contain  an  amount  of  saline  matter  equal  to  that  of 
the  Serum,  no  absorption  of  it  takes  place ;  it  remains  in  the  intestinal  tube ; 
and  it  is  voided  by  the  rectum.     Further,  if  the  quantity  of  saline  matter  in 
the  solution  be  greater  than  that  of  the  Serum,  not  only  will  no  absorption 
take  place,  but  there  will  be  an  endosmose  of  the  water  of  the  blood  towards 
the  solution ;  so  that  a  large  quantity  of  fluid  is  discharged  by  the  Intestinal 
canal.     This  simple  'explanation,  first  offered  by  Liebig4  accounts  well  for 
the  diuretic  effect  of  most  weak  saline  solutions,  and  the  purgative  qualities  of 
stronger  ones. — For  the  transit  of  the  peculiar  principles  of  Vegetables,  how- 
ever, it  appears  that  from  one  to  two  hours  are  usually  required.     The  effect 

*  For  a  scientific  explanation  of  this  fact,  see  Princ.  of  Gen.  and  Comp.  Phys.,  §  539. 
See  Muller's  Physiology,  p.  589. 
Chemistry  applied  to  Agriculture  and  Physiology,  Part  ii. 


MAMMARY  GLANDS SECRETION  OF  MILK. 


647 


of  Oil  of  Turpentine,  and  probably  of  other  volatile  agents,  is  produced  much 
more  rapidly;  the  characteristic  odour  of  violets  being  perceptible  in  the 
Urine  passed  but  a  few  minutes  after  the  vapour  of  the  oil  had  been  received 
into  the  lungs. 

4. — Mammary  Glands. — Secretion  of  Milk. 

853.  We  now  come  to  those  Glands,  whose  action  is  rather  to  elaborate 
from  the  Blood  certain  products,  which  are  destined  for  special  uses  in  the 
economy,  than  to  eliminate  matters,  whose  retention  in  the  circulating  current 
would  be  injurious.  Pre-eminent  amongst  these  in  size  and  importance,  at 
least  during  their  period  of  activity,  are  the  Mammary  Glands;  which  are 
found  only  in  the  animals  of  the  Class  Mammalia,  and  which  present  them- 
selves in  an  almost  rudimentary  state  in  some  of  the  non-placental  subdivisions 
of  the  class  (§44). 

a.  The  structure  of  the  Human  Mammary  Gland,  which  has  been  recently  investigated 
fully  by  Sir  A.  Cooper,  is  very  simple,  and  easily  described.  It  consists  of  a  series  of  ducts 
passing  inwards  from  their  termination  in  the  nipple,  and  then  ramifying  like  the  roots  of  a 
tree,  their  ultimate  subdivisions  terminating  in  minute  follicles.  The  mamillary  tubes  are 
usually  about  ten  or  twelve  in  number;  they  are  straight  ducts,  of  somewhat  variable  size; 
and  their  orifices,  which  are  situated  in  the  centre  of  the  nipple,  and  are  usually  concealed 
by  the  overlapping  of  its  sides,  are  narrower  than  the  tubes  themselves.  At  the  base  of  the 
nipple,  these  tubes  dilate  into  reservoirs,  which  extend  beneath  the  areola  and  to  some  dis- 
tance into  the  gland,  when  the  breast  is  in  a  state  of  lactation.  These  are  much  larger  in 
many  of  the  lower  Mammalia  than  they  afe  in  the  Human  female;  their  use  is  to  supply 
the  immediate  wants  of  the  child  when  it  is  first  applied  to  the  breast,  so  that  it  shall  not 
be  disappointed,  but  shall  be  induced  to  proceed  with  sucking  until  the  draught  be  occasioned 
(§  626).  From  each  of  these  reservoirs  commence  five  or  six  main  branches  of  the  lacti- 
ferous tubes,  each  of  which  speedily  subdivides  into  smaller  ones;  and  these  again  divari- 
cate, until  their  size  is  very  much  reduced,  and  their  extent  greatly  increased.  The  propor- 
tional size  of  the  trunk  and  of  its  branches,  appears  to  follow  the  same  law  which  governs 
that  of  the  blood-vessels.  The  breast  is  not  formed  into  regular  lobes  by  the  ramifications 
of  the  ducts;  because  they  ramify  between,  and  intermix  with  each  other  so  as  to  destroy 


[Fig.  250. 


[Fig.  251. 


The  Mammary  Gland  after  -the  removal  of  the 
skin,  as  taken  from  the  subject  three  days  after 
delivery ;  1,  the  surface  of  the  chest ;  2,  subcuta- 
neous fat ;  3,  the  skin  covering  the  gland ;  4,  cir- 
cumference of  the  gland;  5,  its  lobules  separated 
by  fat;  6,  the  lactiferous  ducts  converging  to  unite 
in  the  nipple ;  7,  the  nipple  slightly  raised  and 
showing  the  openings  of  the  tubes  at  its  extremity.] 


A  vertical  section  of  the  Mammary  Gland, 
showing  its  thickness  and  the  origins  oHfce  lacti- 
ferous ducts ;  1, 2, 3,  its  pectoral  surface ;  4,  section 
of  the  skin  on  the  surface  of  the  gland ;  5,  the  thin 
skin  covering  the  nipple ;  6,  the  lobules  and  lobes 
composing  the  gland ;  7,  the  lactiferous  tubes  com- 
ing from  the  lobules;  8,  the  same  tubes  collected 
in  the  nipple.] 


648 


OF  SECRETION. 

Fig.  252. 


Distribution  of  the  milk-ducts  in  the  Mamma  of  the  Human  female,  during  lactation;   the  ducts 

injected  with  wax. 

the  simplicity  and  uniformity  of  their  divisions.  It  is- very  rarely,  however,  that  they  inos- 
culate. The  mammary  ducts  are  composed  of  a  fibrous  coat  lined  by  a  mucous  membrane ; 
the  latter  is  highly  vascular,  and  forms  a  secretion  of  its  own,  which  sometimes  collects  in 
considerable  quantity  when  the  milk  ceases  to  be  produced. 

b.  The  gland  itself  is  composed  of  the  union  of  a.  number  of  glandules,  which  are  con- 
nected by  means  of  the  fibrous  or  fascial  tissue  of  the  gland ;  it  is  between  these,  that  the 
mammary  tubes  may  be  observed  to  ramify;  and  from  them  their  branches  spring.  When 
the  glandules  are  filled  with  injection,  and  for  a  long  time  macerated  in  water  and  un- 
ravelled, they  are  found  to  be  disposed  in  lobuli ;  and  when  a  branch  of  mammary  tube  is 
separated,  with  the  glandules  attached,  the  part  appears  like  a  bunch  of  fruit  hanging  by  its 
stalk.  When  the  lactiferous  tube  proceeding  from  a  glandule  is  minutely  injected,  the  latter 
will  be  found  to  be  composed  of  numerous  follicles,  in  which  the  ultimate  ramifications  of 
the  former  terminate,  or  rather  originate.  Their  size,  in  full  lactation,  is  that  of  a  hole 


Fig.  253. 


Fig.  254. 


Termination  of  portion  of  milk- 
duct  in  a  cluster  of  follicles ;  from 
a  mercurial  injection;  enlarged 
four  times. 


Ultimate  follicles  of  Mammary 
gland,  with  their  secreting  cells, 
o,  o/ — 6,  6,  the  nuclei. 


MAMMARY  GLANDS — SECRETION  OF  MILK.  649 

pricked  in  paper  by  the  point  of  a  very  fine  pin ;  so  that  the  follicles  are,  when  distended 
.  with  quicksilver  or  milk,  just  visible  to  the  naked  eye.  At  other  times,  however,  the  follicles 
do  not  admit  of  being  injected,  though  the  lactiferous  tubes  may  have  been  completely  filled. 
They  are  lined  by  a  continuation  of  the  same  membrane,  with  that  which  lines  the  ducts ; 
and  this  possesses  a  high  vascularity.  The  arteries  which  supply  the  glandules  with  blood, 
become  very  large  during  lactation;  and  their  divisions  spread  themselves  minutely  on  the 
follicles.  From  the  blood  which  they  convey,  the  milk  is  secreted  and  poured  into  the 
follicles,  whence  it  flows  into  the  ducts.  From  the  researches  of  Mr.  Goodsir  it  appears, 
that,  in  common  with  other  glandular  structures,  the  inner  surface  of  the  milk-follicles  is 
covered  with  a  layer  of  epithelium-cells;  which,  being  seen  to  contain  milk-globules,  may 
be  without  doubt  regarded  as  the  real  agents  in  the  secreting  process.  Absorbent  vessels 
are  seen  to  arise  in  large  numbers  in  the  neighbourhood  of  the  follicles;  their  function  ap- 
pears to  be,  to  absorb  the  more  watery  part  of  the  milk  contained  in  the  follicles  and  tubes, 
so  as  to  render  it  more  nutrient  than  it  is  as  first  secreted;  and  also  to  relieve  the  distention 
which  would  occur,  during  the  absence  of  the  child,  from  the  continuance  of  the  secreting 
process. 

c.  The  Mammary  gland  may  be  detected  at  an  early  period  of  fetal  existence ;  being 
easily  distinguishable  from  the  surrounding  parts,  by  the  redness  of  its  colour  and  its  high 
vascularity,  especially  when  the  whole  is  injected.     At  this  period  it  presents  no  difference 
in  the  male  and  female;  and  it  is  not  until  near  the  period  of  puberty,  that  any  striking 
change  manifests  itself, — the  gland  continuing  to  grow,  in  each  sex,  in  proportion  to  the 
body  at  large.     About  the  age  of  thirteen,  however,  the  enlargement  of  the  gland  com- 
mences in  the  Female ;  and  by  sixteen  years,  it  is  greatly  evolved,  and  some  of  the  lactife- 
rous tubes  can  be  injected.     At  about  the  age  of  twenty,  the  gland  attains  its  full  size 
previous  to  lactation ;  but  the  milk  follicles  cannot  even  then  be  injected  from  the  tubes. 
During  pregnancy,  the  mammae  receive  a  greatly-increased  quantity  of  blood.     This  deter- 
mination often  commences  very  early,  and  produces  a  feeling  of  tenderness  and  distention, 
which  is  a  valuable  sign  (where  it  exists  in  connection  with  others)  of  the  commencement 
of  gestation.     The  Areola  at  this  time  becomes  darker  in  its  colour,  and  thicker  in  sub- 
stance, and  more  extended ;  its  papillae  become  'more  developed,  and  the  secretion  from  its 
follicles  increased.     The  vascularity  of  the  gland  continues  to  increase  during  pregnancy; 
and  at  the  time  of  parturition,  its  tabulated  character  can  be  distinctly  felt.     The  follicles 
are  not,  however,  developed  sufficiently  for  injection,  until  lactation  has  commenced.     After 
the  cessation  of  the  catamenia  from  age,  so  that  pregnancy  is  no  longer  possible,  the  lactife- 
rous ducts  continue  open,  but  the  milk  follicles  are  incapable  of  receiving  injection.     The 
substance  of  the  glandules  gradually  disappears,  so  that  in  old  age  only  portions  of  the  ducts 
remain,  which  are  usually  loaded  with  mucus;  but  the  place  of  the  glandules  is  commonly 
filled  up  by  adipose  tissue,  so  that  the  form  of  the  breast  is  preserved.     Sir  A.  Cooper 
notices  a  curious  change,  which  he  states  to  be  almost  invariable  with  age, — namely,  the 
ossification  of  the  arteries  of  the  breast,  the  large  trunks  as  well  as  the  branches ;  so  that 
their  calibre  is  greatly  diminished,  or  even  obliterated. 

d.  The  Mammary  gland  of  the  Male  is  a  sort  of  miniature  picture  of  that  of  the  female. 
It  varies  extremely  in  its  magnitude,  being  in  some  persons  of  the  size  of  a  large  pea ; 
whilst  in  others  it  is  an  inch,  or  even  two  inches  in  diameter.     In  its  structure  it  corre- 
sponds exactly  with  that  of  the  female,  but  is  altogether  on  a  smaller  scale.     It  is  composed 
of  lobules  containing  follicles,  from  which  ducts  arise ;  and  these  follicles  and  ducts  are  not 
too  minute  to  be  injected,  although  with  difficulty.     The  evolution  of  the  gland  goes  on  pari 
passu  with  that  of  the  body,  not  undergoing  an  increase  at  any  particular  period ;  it  is  some- 
times of  considerable  size  in  old  age.     A  fluid,  which  is  probably  mucus,  may  be  pressed 
from  the  nipple  in  many  persons;  and  this  in  the  dead  body,  with  even  more  facility  than  in 
the  living.    That  the  essential  character  of  the  gland  is  the  same  in  the  male  as  in  the  female, 
is  shown  by  the  instances,  of  which  there  are  now  several  on  record,  in  which  infants  have 
been  suckled  by  men.     The  following  is  given  by  Dr.  Dunglison.*     "  Professor  Hall,  of  the 
University  of  Maryland,  exhibited  to  his  Obstetrical  class,  in  the  year  1837,  a  coloured  man, 
fifty-five  years  of  age,  who  had  large,  soft,  well-formed  mammae,  rather  more  conical  than 
those  of  the  female,  and  projecting  fully  seven  inches  from  the  chest;  with  perfect  and  large 
nipples.     The  glandular  structure  seemed  to  the  touch  to  be  exactly  like  that  of  the  female. 
This  man  had  officiated  as  wet-nurse,  for  several  years,  in  the  family  of  his  mistress ;  and 
he  represented  that  the  secretion  of  milk  was  induced  by  applying  the  children  entrusted  to 
his  care  to  the  breasts  during  the  night.     When  the  milk  was  no  longer  required,  great  dif- 


*  Dunglison's  Physiology,  [sixth  ed.,  vol.  ii.  p.  480.]     See  also  the  case  described  by  the. 
Bishop  of  Cork,  in  the  Philosophical  Transactions,  vol.  xli.  p.  813:  one  mentioned  by  Cap- 
tain Franklin  (Narrative  of  a  Journey  to  the  Polar  Sea,  p.  157);  and  one  which  fell  under 
the  notice  of  the  celebrated  traveller  Humboldt  (Personal  Narrative,  vol.  iii.  p.  58). 
55 


650  OF  SECRETION. 

ficulty  was  experienced  in  arresting  the  secretion.      His  genital  organs  were  fully  deve 
loped." — Corresponding  facts  are  also  recorded  of  the  male  of  several  of  the  lower  animals 

854.  The  secretion  of  Milk  consists  of  Water  holding  in  solution  Sugar, 
various  Saline  ingredients,  and  a  peculiar  albuminous  substance  termed 
Caseine;  and  having  Oleaginous  particles  suspended  in  it.  The  constitution 
of  this  fluid  is  made  evident  by  the  ordinary  processes,  to  which  it  is  sub- 
jected in  domestic  economy.  If  it  be  allowed  to  stand  for  some  time,  exposed 
to  the  air,  a  large  part  of  the  oleaginous  globules  come  to  the  surface,  being 
of  less  specific  gravity  than  the  fluid  through  which  they  are  diffused.  At 
the  same  time  there  is  reason  to  believe  that  they  undergo  a  change  which 
will  be  presently  described.  The  cream  thus  formed  does  not,  however,  con- 
sist of  oily  particles  alone ;  but  includes  a  considerable  amount  of  caseine, 
with  the  sugar  and  salts  of  the  milk.  These  are  further  separated  by  the 
continued  agitation  of  the  cream ;  which,  by  rupturing  the  envelopes  of  the 
oil-globules,  separates  it  into  butter,  formed  by  their  aggregation,  and  butter- 
milk, containing  the  caseine,  sugar,  &c.  A  considerable  quantity  of  caseine, 
however,  is  entangled  with  the  oleaginous  matter ;  and  this  has  a  tendency  to 
decompose,  so  as  to  render  the  butter  rancid.  It  may  be  separated  by  melting 
the  butter  at  the  temperature  of  180° ;  when  the  caseine  will  fall  to  the  bot- 
tom, leaving  the  butter  pure,  and  much  less  liable  to  change. — The  milk,  after 
the  cream  has  been  removed,  still  contains  the  greatest  part  of  its  caseine  and 
sugar.  If  it  be  kept  long  enough,  spontaneous  change  takes  place  in  its  com- 
position ;  the  sugar  is  converted  into  lactic  acid,  and  this  coagulates  the  caseine, 
precipitating  it  in  small  flakes.  The  same  precipitation  may  be  accomplished 
at  any  time,  by  the  addition  of  an  acid;  all  the  acids,  however,  which  act 
upon  albumen,  do  not  precipitate  caseine,  as  will  presently  be  pointed  out  in 
detail ;  the  most  effectual  is  that  contained  in  the  dried  stomach  of  a  calf, 
known  as  rennet.  This  exerts  so  powerful  an  influence  over  it,  that,  accord- 
ing to  the  experiments  of  Berzelius,  a  piece  of  the  membrane  coagulated  the 
caseine  of  1800  times  its  weight  of  milk,  with  the  loss  of  only  l*17th  part  of 
its  own  weight;  so  that  the  active  principle,  dissolved  from  the  rennet,  must 
have  collected  the  caseine  of  about  30,000  times  its  weight  of  milk.  The 
whey  left  after  the  curd  has  been  separated,  contains  a  large  proportion  of  the 
saccharine  and  saline  matter,  entering  into  the  original  composition  of  the 
milk.  This  may  be  readily  separated  by  evaporation.* 

a.  When  Milk  is  examined  with  the  Microscope,  it  is  seen  to  contain  a  large  number  of 
particles  of  irregular  size  and  form,  suspended  in  a  somewhat  turbid  fluid;  these  particles 
(according  to  the  measurement  of  Donnef)  vary  in  size  from  about  the  l-12,700th  to  the 
l-3040th  of  an  inch;  and  they  are  termed  milk-globules.  They  are  not  affected  by  the  mere 
contact  of  ether  or  alkalies ;  but  if  these  reagents  are  shaken  with  them,  an  immediate  solu- 
tion is  the  result.  The  same  effect  happens,  if  they  are  first  treated  with  acetic  acid. 
Hence  it  is  evident,  that  the  globules  consist  of  oily  matter,  inclosed  in  an  envelope  of  some 
kind;  and  an  extremely  delicate  pellicle  may,  in  fact,  be  distinguished  after  the  removal  of 
the  oily  matter  by  ether;  or,  after  the  globules  have  been  ruptured,  and  their  contents.pressed 
out,  by  rubbing  a  drop  of  milk  between  two  plates  of  glass.  No  proof  of  the  organization 
of  this  pellicle  has,  however,  been  detected ;  and  it  is  probably  to  be  regarded  as  the  simple 
result  of  the  contact  of  oil  with  albuminous  matter,  which  is  known  to  give  rise  to  a  mem- 
branous film. — Besides  these  milk-globules,  other  globules  of  much  smaller  size  are  seen  in 
milk ;  and  these  present  the  peculiar  movement,  which  is  exhibited  by  molecules  in  gene- 
ral. Most  of  them  seem  to  consist  of  oily  matter,  not  inclosed  in  an  envelope,  as  they  are 
at  once  dissolved,  when  the  fluid  is  treated  with  ether;  but,  according  to  the  statements  of 
Donne,  it  would  seem  that  a  portion  of  them  are  composed  of  caseine,  suspended,  not  dis- 
solved, in  the  fluid.  It  may  be  reasonably  doubted,  however,  whether  these  were  not  in 


*  A  considerable  quantity  is  thus  obtained  for  household  purposes  in  Switzerland, 
•j-  Cours  de  Microscopie,  Douzieme  Legon. 


MAMMARY  GLANDS SECRETION  OF  MILK.  651 

a  state  of  change ;  whether  from  their  own  decomposition,  or  from  incipient  coagulation ; 
either  of  which  might  have  taken  place  during  the  processes  of  filtration,  &c.,  that  were 
required  to  determine  their  nature.  In  addition  to  the  foregoing  particles,  there  are  found  in 
the  Colostrum,  or  milk  first  secreted  after  delivery,  large  yellow  granulated  corpuscles,  which 
are  described  by  Donne  as  composed  of  a  multitude  of  small  grains  aggregated  together,  and 
frequently  including  a  true  globule  of  milk  in  their  centre :  these  are  for  the  most  part  solu- 
ble in  ether;  but  traces  of  some  adhesive  matter,  probably  mucus,  holding  together  the  par- 
ticles, are  then  seen.  They  are  considered  by  some  as  exudation-corpuscles;  to  which  they 
certainly  bear  a  close  resemblance.  Lamellae  of  epithelium  are  also  found  in  the  milk. — 
All  the  larger  globules  may  be  removed  by  repeated  filtration;  and  the  fluid  is  then  nearly 
transparent.  This,  in  fact,  is  the  simplest  way  of  separating  the  oleaginous  from  the  other 
constituents  of  the  milk ;  as  little  caseine  then  adlieres  to  the  former.  That  the  transparent 
fluid  which  has  passed  through  the  filter  contains  nearly  the  whole  amount  of  the  caseine 
of  the  milk,  appears  a  sufficient  proof  that  this  is,  for  the  most  part,  truly  dissolved  in  the 
fluid. 

b.  We  shall  now  consider  the  chemical  characters  of  each  of  the  foregoing  ingredients. — 
The  Oleaginous  matter  of  milk  principally  consists,  like  fatty  matter  in  general,  of  the  two 
substances,  elaine  and  stearine;  which  are  converted  in  the  process  of  saponification  into 
the  elaic,  stearic,  and  margaric  acids :  but  it  also  contains  another  substance  peculiar  to  it, 
which  yields  in  saponification  three  volatile  acids,  of  strong  animal  odour,  to  which  Chev- 
reul  has  given  the  names  of  butyric,  caproic,  and  capric  acids ;  whilst  the  fatty  substance 
itself,  to  which  the  peculiar  smell  and  taste  of  butter  are  due,  is  designated  as  butyrine.  The 
peculiar  acids  are  not  only  formed  when  the  butyrine  is  treated  with  alkalies;  but  are  pro- 
duced by  the  ordinary  decomposition  of  this  principle,  which  is  favoured  by  time  and  mode- 
rate warmth. — The  Caseine  or  cheesy  matter  of  milk,,  which  is  obtained  with  some  slight 
admixture  of  fatty  matter  in  the  production  of  cheese  from  skimmed  milk,  is  chiefly  distin- 
guished from  Albumen,  by  the  peculiar  readiness  with  which  it  is  precipitated  by  feeble 
organic  acids,  such  as  the  lactic  and  acetic ;  and  by  its  non-coagulability  by  heat  alone.  The 
Caseine  of  Human  milk,  however,  is  much  less  precipitable  by  acids,  than  is  that  of  the 
Cow;  very  commonly  resisting  the  action  of  the  mineral  acids,  and  even  that  of  the  acetic; 
but  being  always  coagulated  by  rennet,  though  the  curd  is  long  in  collecting.  It  is  remarked 
by  Dr.  G.  O.  Rees,*  that  the  caseine  of  human  milk  thus  bears  somewhat  the  same  relation 
to  that  of  the  cow,  that  the  albumen  of  chyle  bears  to  that  of  the  blood. — The  Sugar  of  milk, 
which  may  be  obtained  by  evaporating  whey  to  the  consistence  of  a  syrup  and  then  setting 
it  aside  to  crystallize,  contains  a  large  proportion  (12  per  cent.)  of  water,  so  that  it  may  be 
considered  as  really  a  hydrate  of  sugar;  it  is  nearly  identical  in  its  composition  with  starch, 
and  may,  like  it,  be  converted  into  true  sugar  by  the  action  of  sulphuric  acid ;  and  when  in 
contact  with  a  ferment,  or  decomposing  azotized  compound,  it  is  extremely  prone  to  be  con- 
verted into  lactic  acid,  by  appropriating  to  itself  the  elements  of  water.  It  is,  in  fact,  through 
this  process,  that  the  coagulation  of  the  caseine  is  effected,  by  means  of  rennet;  for  as  soon 
as  a  very  minute  quantity  of  lactic  acid  is  generated,  it  withdraws  from  the  caseine  the  free 
alkali  which  kept  it  in  solution,  and  the  caseine  is  consequently  precipitated.  The  same 
effect  will  be  produced  by  incipient  decomposition  of  the  caseine  itself;  which  will  soon 
occasion  lactic  acid  to  be  generated  from  the  sugar,  in  sufficient  quantity  to  give  to  the  milk 
a  distinctly  acid  reaction.— The  Saline  matter  contained  in  milk,  appears  to  be  nearly  iden- 
tical with  that  of  the  blood;  with  a  larger  proportion  of  the  phosphates  of  lime  and  mag- 
nesia, which  amount  to  2  or  2^  parts  in  1000.  These  phosphates  are  held  in  solution  chiefly 
by  the  Caseine;  which  seems  to  have  a  power  of  combining  with  them,  even  greater  than 
that  of  Albumen :  the  presence  of  a  minute  proportion  of  free  alkali,  also,  assists  their  solu- 
tion. A  small  portion  of  iron  in  the  state  of  phosphate,  together  with  the  chlorides  of 
potassium  and  sodium,  may  also  be  detected  in  milk.-f- 

855.  The  proportion  of  these  different  constituents  is  liable  to  great  varia- 
tion, from  several  causes.  Thus,  the  whole  amount  of  the  solid  constituents 
may  vary  from  86  to  138*6  parts  in  1000;  the  difference  being  partly  due  to 
individual  constitution,  but  in  great  part,  also,  to  the  amount  and  character 
of  the  ingesta.  The  average  seems  to  be  between  100  and  120  parts.  The 
following  are  the  results  of  the  analyses  of  Simon;  the  first  column  being 
the  average  of  fourteen  observations  upon  the  same  woman ;  the  second  giv- 
ing the  maximum  of  each  ingredient;  and  the  third  the  minimum: — 

*  Art.  MILK,  in  the  Cyclopaedia  of  Anatomy  and  Physiology, 
f  Haidlen,  in  Annalen  der  Chemie  und  Pharmacie,  xlv.  p.  263. 


652  OF  SECRETION. 

I-  II.  III. 

Water 883*6  914-0  861-4 

Butter 25-3  54'0  8-0 

Caseine       .         .     •     .         .         .         .           34'3  45'2  19'6 

Sugar  of  Milk  and  Extractive  Matters           48-2  62*4  39-2 

Fixed  salts 2-3  .2-7  1-6 

It  also  appears  from  the  analyses  of  Simon,  that  the  proportion  of  the  differ- 
ent ingredients  is  liable  to  variation,  according  to  the  time  which  has  elapsed 
since  parturition.  The  quantity  of  Caseine  is  at  its  minimum  at  the  com- 
mencement of  lactation,  and  then  gradually  rises  until  it  attains  a  nearly  fixed 
proportion.  The  quantity  of  Sugar,  on  the  contrary,  is  at  its  maximum  at 
first,  and  gradually  diminishes.  The  amount  of  Butter  (as  appears  from  the 
wide  extremes  shown  in  the  above  tables)  is  more  variable  than  that  of  any 
other  constituent — .That  some  of  the  variations  are  due,  moreover,  to  the 
character  of  the  ingesta,  and  others  to  the  external  temperature,  amount  of 
exercise,  and  other  circumstances  affecting  the  individual,  is  proved  by  the 
recent  inquiries  of  Dr.  Playfair  upon  the  Milk  of  the  Cow.  He  has  shown 
that  the  amount  of  butter  depends  in  part  upon  the  quantity  of  oily  matter  in 
the  food ;  and  in  part  upon  the  amount  of  exercise  which  the  animal  takes, 
and  the  warmth  of  the  atmosphere  in  which  it  is  kept.  Exercise  and  cold, 
by  increasing  the  respiration,  eliminate  part  of  the  oily  matter  in  the  form  of 
carbonic  acid  and  water;  whilst  rest  and  warmth,  by  diminishing  this  drain, 
favour  its  passage  into  the  milk. — The  proportion  of  Caseine,  on  the  other 
hand,  is  increased  by  exercise ;  which  would  seem  to  show  that  this  ingre- 
dient is  derived  from  the  disintegration  of  Muscular  tissue, — and  thus  adds 
strength  to  the  Author's  view  (§  681)  that  of  the  matter  thus  set  free,  a  part 
only  is  destined  to  immediate  excretion,  and  that  a  part  may  again  be 
subservient  to  the  operations  of  Nutrition.  Dr.  Playfair's  experience  on  this 
head  seems  to  correspond  with  the  results  of  common  observation  in  Swit- 
zerland, where  they  pasture  cattle  in  very  exposed  situations,  and  are  obliged 
to  use  a  great  deal  of  muscular  exertion.  The  quantity  of  Butter  yielded  by 
them  is  very  small;  whilst  the  Cheese  is  in  unusually  large  proportion.  But 
these  very  cattle,  when  stall-fed,  give  a  large  quantity  of  Butter  and  very  little 
Cheese. 

856.  The  change  which  naturally  takes  place,  from  the  condition  of  Co- 
lostrum to  that  of  true  Milk,  during  the  first  week  of  lactation,  is  a  very  im- 
portant one.  The  Colostrum  has  a  purgative  effect  upon  the  child,  which  is 
very  useful  in  clearing  its  bowels  of  the  meconium  that  loads  them  at  birth ; 
and  thus  the  necessity  of  any  other  purgative  is  generally  superseded.  Oc- 
casionally, however,  the  colostric  character  is  retained  by  the  milk,  during 
an  abnormally  long  period;  and  the  health  of  the  infant  is  then  severely  af- 
fected. It  is  important  to  know  that  this  may  occur,  even  though  the  rnilk 
may  present  all  the  usual  appearances  of  the  healthy  secretion ;  but  the  mi- 
croscope at  once  detects  the  difference.*  The  return  to  the  character  of  the 
early  milk,  which  has  been  stated  to  take  place  after  the  expiration  of  about 
twelve  months,  seems  to  indicate  that  Nature  designs  the  secretion  no  longer 
to  be  encouraged.  The  mother's  milk  cannot  then  be  so  nutritious  to  the 
child  as  other  food;t  and  every  medical  man  is  familiar  with  the  injurious 
consequences,  to  which  she  renders  herself  liable  by  unduly  prolonging  lac- 
tation.J 

*  See  Donne,  "Du  Lait,  et  en  particulier  celui  des  Nourrices;"  and  Brit,  and  For.  Med. 
Review,  vol.  vi.  p.  181. 

f  On  the  whole  subject  of  Infant  Nutrition,  the  Author  would  strongly  recommend  the 
excellent  little  work  of  Dr.  A.  Combe,  formerly  referred  to. 

One  of  these,  which  has  particularly  fallen  under  the  Author's  notice,  is  debility  of  the 


MAMMARY  GLANDS — SECRETION  OF  MILK.  653 

857.  It  is  very  interesting  to  observe  that  Milk  contains  the  three  classes 
of  principles  which  are  required  for  human  food, — the  Albuminous,  Oleagi- 
nous, and   Saccharine  ;  and  it  is  the  only  secreted  fluid,  in  which  these  all 
exist  in  any  considerable  amount.     It  is,  therefore,  the  food  most  perfectly 
adapted  for  the  young  animal ;  and  is  the  only  single  article  supplied  by  na- 
ture, in  which  such  a  combination  exists.     Our  artificial  combinations  will  be 
suitable  to  replace  it,  just  in  proportion  as  they  imitate  its  character;  but  in 
none  of  them  can  we  advantageously  dispense  with  milk,  under  some  form 
or  other.     It  should  be  remembered  that  the  saline  ingredients  of  Milk,  espe- 
cially the  phosphates  of  lime,  magnesia,  and  iron,  have   a  very  important 
function  in  the  nutrition  of  the  infant, — affording  the  material  for  the  consoli- 
dation of  its  bones,  and  for  the  production  of  its  red  blood-corpuscles ;  and 
any  fluid  substituted  for  milk,  which  does  not  contain  these,  is  deficient  in 
essential  constituents.     It  is  very  justly  remarked  by  Dr.  Rees,  that  of  all 
the  secreted  fluids,  Milk  is  most  nearly  allied  in  its  composition  to  blood. 

858.  The  proportion  of  the  different  ingredients  in  the  Milk  of  different 
animals,  is  subject  to  considerable  variation :  and  this  fact  is  of  much  practi- 
cal importance  in  guiding  our  selection,  when  good  Human  milk  cannot  be 
conveniently  obtained  for  the  nourishment  of  an  infant.     The  first  point  to 
be  inquired  into,  is  the  quantity  of  solid  matter  contained  in  each  kind ;  this 
may  be   determined  either  by  evaporation,  or  by  the  specific  gravity  of  the 
fluid.     The  Specific  Gravity  of  Human  milk  is  stated  by  Dr.  Rees  to  vary 
between  1030   and  1035;   others,  however,  have   estimated  it  much  lower. 
That  of  the  Cow  appears  to  be  usually  about  the  same  ;   that  of  the  cream, 
however,  being  1024,  and  that  of  the  skimmed  milk  about  1035.     The  varia- 
tion will  in  part  depend  (as  in  the  case  of  the  urine)  upon  the  quantity  of  fluid 
ingested,  and  in  part,  it  is  probable,  upon  the  manner  in  which  the  milk  is 
drawn  ;  for  it  is  well  known  to  milkers,  that  the  last  milk  they  obtain  is  much 
richer  than  that  with  which  the  udder  is  distended  at  the  commencement. 
The  quantity  of  solid  matter,  obtainable  from  Human  and  from  Cow's  Milk 
by  evaporation,  seems,  like  the  specific  gravities  of  the  fluids,  to  be  nearly  the 
same.     In  the  relative  proportion  of  the  ingredients,  however,  there  is  a  con- 
siderable difference ;  there  being  much  more  sugar,  and  less  caseine  in  Human 
Milk  than  in  that  of  the  Cow.     The  following  table  exhibits  the  relative  pro- 
portion of  the  different  ingredients,  in  the  Milk  of  various  animals,  from  which 
it  is  commonly  obtained: — 

Cow.  Goat.  Sheep.           Ass.  Mare. 

Water 861-0  •     868-0  856-2  907-0  896-3 

Butter          .             .             .              .             .       38-0  33-2  42-0           12-10  traces 

Caseine 68-0  40-2  45-0          16-74  162 

Sugar  of  Milk  and  Extractive  Matters       .       29-0  52-8  50-0  )        R9.qi  R7.« 

Fixed  Salts             ....         6-1  5-8  6-8  \ 

It  appears  from  this,  that,  whilst  the  milk  of  the  Cow,  Goat,  and  Sheep  do 
not  differ  from  each  other  in  any  very  prominent  degree,  that  of  the  Ass  and 
Mare  is  a  fluid  of  very  dissimilar  character,  containing  a  comparatively  small 
proportion  of  caseine  and  butter,  and  abounding  in  sugar.  Hence  it  is,  that 
it  is  much  more  disposed  to  ferment  than  other  milk ;  indeed  the  sugar  of 
Mare's  milk  is  so  abundant,  that  the  Tartars  prepare  from  it  a  spirituous 
liquor,  to  which  they  give  the  name  of  koumiss.  It  appears  from  these  de- 
tails that  no  milk  more  nearly  approaches  that  of  the  Human  female,  than 
that  of  the  Sheep  and  Goat ;  these  both  possess,  however,  a  larger  proportion 
of  caseine,  which  forms  a  peculiarly  dense  curd ;  and  the  milk  of  the  Goat 

retina,  sometimes  proceeding  to  complete  amaurosis;  this,  if  treated  in  time,  is  most  commonly 
relieved  by  discontinuance  of  lactation,  generous  diet,  and  quinine. 

55* 


654  OF  SECRETION. 

is  tainted  with  the  peculiar  odour  of  the  animal,  which  is  more  intense  if  the 
individual  be  dark-coloured.  The  milk  of  the  Cow  will  usually  answer  very 
well  for  the  food  of  the  infant ;  care  being  taken  to  dilute  it  properly,  accord- 
ing to  the  age  of  the  child,  and  to  add  a  little  sugar.  It  is  an  interesting  cir- 
cumstance, lately  ascertained,  that  the  milk  of  Carnivorous  Mammals,  fed  ex- 
clusively on  animal  diet,  contains  scarcely  a  trace  of  sugar,  whilst  the  caseine 
and  butter  are  abundant. 

859.  From  what  has  been  stated  of  the  close  correspondence  between  the 
elements  of  the  Blood  and  those  of  the  Milk,  it  is  evident  that  we  can  scarcely 
expect  to  trace  the  existence  of  the  latter,  as  such,  in  the  circulating  fluid. 
To  what  degree  the  change,  in  which  their  elaboration  consists,  is  accom- 
plished in  the  Mammary  gland,  or  during  the  course  of  the  circulation,  there 
is  no  certain  means  of  ascertaining.  The  recent  discovery  of  the  usual  pre- 
sence of  the  organic  compound  named  kiesteine  (which  is  nearly  related  to 
caseine),  in  the  urine  of  pregnant  women,  seems  to  indicate  that  the  conversion 
of  albumen  into  caseine  takes  place  in  the  blood, — this  curious  excretion  being 
the  means  of  preventing  its  accumulation  in  the  circulating  fluid,  previously 
to  the  time  when  it  is  secreted  by  the  mamma?.*  It  is  evident  that  this  secre- 
tion cannot  serve  as  the  channel  for  the  deportation  of  any  element,  the  accu- 
mulation of  which  would  be  injurious  to  the  system;  since  it  does  not  occur 
in  the  male  at  all ;  and  is  present  in  the  female  at  particular  times  only.  Yet 
there  is  reason  to  believe  that  if,  whilst  the  process  is  going  on,  it  be  suddenly 
checked,  the  retention  of  the  material  in  the  blood,  or  the  reabsorption  of  the 
secreted  fluid,  is  attended  with  injurious  consequences.  Thus  if,  when  the 
milk  is  first  secreted,  the  child  be  not  put  to  the  breast,  an  accumulation  takes 
place,  which,  if  not  relieved,  occasions  great  general  disturbance  of  the  system. 
The  narrowness  of  the  orifice  of  the  milk-tubes  obstructs  the  spontaneous  exit 
of  the  fluid,  especially  in  primiparx;  the  reservoirs  and  ducts  become  loaded; 
further  secretion  is  prevented ;  and  a  state  of  congestion  of  the  vessels  of  the 
gland,  tending  to  inflammation,  is  induced.  The  accompanying  fever  is  partly 
due,  no  doubt,  to  the  local  disturbance ;  but  in  part  also,  there  seems  reason 
to  believe,  to  the  reabsorption  of  the  milk  into  the  blood;  this  cannot  but  be 
injurious,  since,  although  but  little  altered,  the  constitution  of  milk  is  essen- 
tially different,  especially  in  regard  to  the  quantity  of  crystallizable  matter 
(sugar)  which  it  contains.  The  instances  of  the  vicarious  secretion  of  milk 
are  not  numerous ;  and  in  no  instance  is  there  any  proof  that  the  elements  of 
the  fluid  were  pre-existent  in  the  blood.  Some  of  the  most  curious  are  those 
in  which  it  has  been  poured  out  from  a  gland  in  the  groin ;  but  it  is  probable 
that  this  was  in  consequence  of  the  existence  of  a  real  repetition,  in  that 
place,  of  the  true  mammary  structure, — this  being  the  situation  of  the  mamma? 
of  many  of  the  inferior  animals,  of  which  the  analogues  in  Man  are  usually 
undeveloped. 

a.  The  following  is  a  more  unequivocal  case  of  vicarious  secretion ;  and  it  is  peculiarly 
interesting  as  exhibiting  the  injurious  effects  of  the  re-absorption  of  the  secretion,  and  the 
relief  which  the  system  experienced  when  it  was  separated  from  the  blood  by  the  new 
channel.  "  A  lady  of  delicate  constitution  (with  a  predisposition  to  pneumonia)  was  pre- 
vented from  suckling  her  child,  as  she  desired,  by  the  following  circumstance.  Soon  after 
her  delivery  she  had  a  severe  fever,  during  which  her  breasts  became  very  large  and  hard; 
the  nipples  were  swollen  and  firm;  and  there  was  evidently  an  abundant  secretion  of 
milk ;  but  neither  the  sucking  of  the  infant,  nor  any  artificial  means,  could  draw  a  single 
drop  of  fluid  from  the  swollen  glands.  It  was  clear  that  the  milk-tubes  were  closed;  and  as 
the  breasts  continued  to  grow  larger  and  more  painful,  purgatives  and  other  means  were 
employed  to  check  the  secretion  of  milk.  After  three  days  the  fever  somewhat  diminished, 
and  was  replaced  by  a  constant  cough,  which  was  at  first  dry,  but  soon  after  was  followed 


See  Dr.  Golding  Bird,  in  Guy's  Hosp.  Rep.,  vol.  v. 


SALIVARY  GLANDS  AND  PANCREAS.  655 

by  the  expectoration  of  simple  mucus.  After  this,  the  cough  diminished  in  severity,  and  the 
expectoration  became  easy ;  but  the  sputa  were  no  longer  mucous,  but  were  composed  of  a 
liquid,  which  had  all  the  physical  characters  of  genuine  milk.  This  continued  for  fifteen 
days;  the  quantity  of  milk  expectorated  amounting  to  three  ounces  or  more  in  the  twenty- 
four  hours.  The  breasts  gradually  diminished  hi  size :  and  by  the  time  that  the  expectoration 
ceased,  they  had  regained  their  natural  dimensions.  The  same  complete  obstacle  to  the 
flow  of  milk  from  the  nipples  recurred  after  the  births  of  four  children  successively,  with 
the  same  sequelse.  After  the  sixth,  she  had  the  same  symptoms  of  fever,  but  this  time 
they  were  not  followed  by  bronchitis  or  the  expectoration  of  milk ;  she  had  in  their  stead 
copious  sweatings,  which,  with  other  severe  symptoms,  reduced  her  to  a  cachectic  state,  and 
terminated  fatally  in  a  fortnight."* 

860.  Of  the   quantity  of  Milk  ordinarily  secreted  by  a  good  Nurse,  it  is 
impossible  to  gain  any  definite  idea ;  as  the  amount  which  can  be  artificially 
drawn,  affords  no  criterion  of  that  which  is  secreted  at  the  time  of  the  draught 
(§  626).     The  quantity  which  can  be  squeezed  from  either  breast  at  any  one 
time,  and  which,  therefore,  must  have  been  contained  in  its  tubes  and  reser- 
voirs, is  about  two  ounces.     The  amount  secreted  is  greatly  influenced  by 
the  mental  and  physical  condition  of  the  female,  and  also  by  the  quantity  and 
character  of  the  ingesta.     In  regard  to  the  influence  of  the  mental  state  upon 
this  secretion,  a^nple  details  have  already  been  given   (Chap.   ix.).     With 
respect  to  the  physical  state  most  favourable  to  the  production  of  an  ample 
supply  of  this  important  fluid,  it  may  be  stated  generally,  that  sound  health, 
a  vigorous  but  not  plethoric  constitution,  regular  habits,  moderate  but  not 
fatiguing  exercise,  and  an  adequate  but  not  excessive  amount  of  nutritious 
food,  furnish  the   conditions  most  required.     It  is  seldom   that  stimulating 
liquors,  which  are  so  commonly  indulged  in,  are  anything  but  prejudicial ;  but 
the  unmeasured  condemnation  of  them  in  which  some  writers  have  indulged, 
is  certainly  injudicious ;  as  experience  amply  demonstrates  the  improvement 
in  the  condition  both  of  mother  and  infant,  which  occasionally  results  from  the 
moderate  employment  of  them. 

861.  The  influence  of  various   Medicines  upon  the  Milk,  is  another  im- 
portant question,  which  has  not   yet  been  sufficiently  investigated.     As  a 
general  rule,  it  appears  that  the  most  soluble  saline  compounds  pass  into  the 
milk  as  into  other  secretions ;  but  there  are  many  exceptions.     Common  salt, 
the  sesqui-carbonate  of  soda,  sulphate  of  soda,  iodide  of  potassium,  oxide  of 
zinc,  tris-nitrate  of  bismuth,  and  sesqui-oxide  of  iron,  have  been  readily  de- 
tected in  the  milk,  when  these  substances  were  experimentally  administered 
to  an  a'ss;  and  ordinary  experience  shows,  that  the  human  infant  is  affected 
by  many  of  these,  when  they  are  administered  to  the  mother.     The  influence 
of  mercurial  medicines  taken  by  the  mother,  in  removing  from  the  infant  a 
syphilitic  taint  possessed  by  both,  is  also  well  known.     The  vegetable  purga- 
tives, especially  castor  oil,  senna,  and  colocynth,  have  little  effect  upon  the 
milk ;  hence  they  are  to  be  preferred  to  the  saline  aperients,  when  it  is  not 
desired  to  act  upon  the  bowels  of  the  child. 

5.— Salivary  Glands  and  Pancreas. 

862.  The  structure  of  the  Salivary  Glands  and  Pancreas  in  Man,  bears 
considerable  resemblance  to  that  of  the  Mammary  glands.     In  some  of  the 
lower  tribes,  however,  they  are  much  simpler.     Thus,  in  the  Echinodermata 
and  in  Insects,  the  Salivary  glands  have  the  character  of  prolonged  coeca, 
more  or  less  convoluted ;  and  the  Pancreas  of  Fishes  presents  itself  in  the 
form  of  a  cluster  of  short  cceca  round  the  pyloric  extremity  of  the  stomach, 
and  opening  into  it  by  distinct  orifices.     The  accompanying  figure  will  give 

*  Bulletino  delle  Scienze  Mediche,  Apr.  1839;  and  Brit,  and  For.  Med.  Review,  Jan. 
1840. 


656 


OF  SECRETION. 


Fig.  255. 


Fig.  256. 


Lobule  of  Parotid  gland  of  a  new-born  infant 
injected  with  mercury.    Magnified  50  diam. 


Distribution  of  Capillaries  around  the 
follicles  of  Parotid  Gland. 


Fig.  257. 


a  sufficient  idea  of  the  structure  of  these  glands  in  Man ;  the  follicles  are 

very  minute,  having  a  diameter  only  about 
three  times  greater  than  that  of  the  capillary 
blood-vessels.  Their  development  commences 
from  a  simple  canal,  sending  off  bud-like  pro- 
cesses, which  opens  from  the  mouth,  and  lies 
amidst  a  cellular  blastema.  As  development 
proceeds,  the  canal  becomes  more  and  more 
ramified,  and  communicates  with  the  enlarged 
parent-cells  of  the  blastema,  which  remain  as 
the  terminal  follicles  of  the  branches  of  the 
gland-duct  (§  823). 

863.  The  Salivary  secretion  is  by  no  means 
necessarily  constant;  being  almost  or  com- 
pletely suspended  by  cessation  of  the  move- 
ment of  the  masticator  muscles  and  tongue,  if 
unexcited  by  any  nervous  stimulus.  Hence 
it  is,  that  the  secretion  is  checked  during  sleep ; 
so  that,  if  the  mouth  be  kept  open,  its  surface 
is  almost  dried  up  by  the  atmosphere.  The 
mode  in  which  the  secretion  is  excited  through 

the  influence  of  the  nervous  system  has  already  been  considered  (§§  625,  626). 
The  quantity  of  Saliva  formed  during  the  twenty-four  hours  has  been  estimated 
at  about  15  or  20  ounces  ;  but  on  this  point  it  is  evidently  impossible  to  speak 
with  certainty.  The  fluid  obtained  from  the  mouth  is  of  a  more  viscous  cha- 
racter than  the  true  saliva  secreted  by  the  glands  ;  being  mingled  with  mucus. 
The  salivary  fluid  varies  as  to  its  chemical  reaction ;  being  sometimes  slightly 
acid,  and  sometimes  slightly  alkaline  ;  but  it  is  seldom  precisely  neutral. 
According  to  Huenefeld,  it  will  at  the  same  time  strike  a  blue  colour  with 
reddened  litmus-paper  ;  and  turn  blue  litmus-paper  red ;  but  the  saliva  ex- 
amined directly  before,  and  during,  the  act  of  eating,  is  always  alkaline.  It 
seems  probable  that  the  acid  reaction  is  due  to  the  mucus  of  the  mouth  ; 
which,  at  times  when  only  a  small  amount  of  saliva  is  excreted,  is  not  neu- 
tralized by  its  alkali.  The  specific  gravity  of  Saliva  varies  from  T006  to 
1*009.  It  contains  a  small  number  of  corpuscles,  which  seem  to  be  partly 
epithelium-cells  from  the  mucous  surface  of  the  mouth,  and  partly  the  secret- 
ing cells  of  the  salivary  vesicles.  The  solid  matter  contained  in  Saliva 
amounts  to  from  10  to  13  parts  in  1000.  The  animal  principles  of  which 


Rudimentary  Pancreas  from  Cod : — 
a,  pyloric  extremity  of  stomach;  b,  in- 
testine. 


LACHRYMAL  GLAND THE  TESTIS.  657 

this  is  composed  are  Albumen,  Mucus,  and  a  peculiar  substance  termed  Ptya- 
lin,  which  is  soluble  in  Water,  insoluble  in  alcohol,  and  yet  is  different  either 
from  albumen  or  gelatin.  A  considerable  proportion  of  saline  and  earthy 
matter  exists  in  the  solid  residue  of  saliva ;  this  is  nearly  of  the  same  cha- 
racter as  that  which  the  blood  contains,  being  chiefly  composed  of  the  phos- 
phate of  lime  and  soda,  the  chlorides  of  sodium  and  potassium,  and  the  lac- 
tates  of  soda  and  potash.  One  remarkable  property  of  the  salivary  secretion, 
is  its  formation  of  a  rust-red  precipitate  when  mixed  with  a  solution  of  per- 
salt  of  iron.  This  is  supposed  to  be  due  to  the  presence  in  it  of  the  prin- 
ciple termed  sulpho-cyanogen.  The  tartar  which  collects  on  the  human  teeth 
consists  principally  of  the  earthy  phosphates,  the  particles  of  which  are  held 
together  by  about  20  per  cent,  of  animal  matter ;  and  nearly  the  same  may 
be  said  of  the  salivary  concretions  which  occasionally  obstruct  the  ducts. — It 
appears  from  various  recent  experiments,  that  the  peculiar  animal  matter  of 
the  Saliva  has  a  decided  effect  in  metamorphosing  certain  alimentary  sub- 
stances, and  thus  performs  the  first  part  of  the  digestive  process.  Starch  may 
be  converted  into  sugar,  and  sugar  into  lactic  acid,  by  its  agency  ;  and  if  acidu- 
lated, it  has  a  solvent  power  for  caseine,  animal  flesh,  and  other  albuminous 
substances  (§  669). 

864.  The  Pancreatic  Secretion  of  Man  cannot,  of  course,  be  readily  ob- 
tained for  analysis ;  that  which  is  procured  from  the  lower  animals,  however, 
probably  gives  a  sufficiently  correct  idea  of  its  character.     It  seems  to  be  of 
a  nearly  similar  nature  with  saliva,  but  usually  contains  a  much  larger  propor- 
tion of  solid  matter;  in  that  of  the  Dog  as  much  as  87  parts  in   1000  have 
been  found ;  and  in  that  of  the  Sheep,  40  parts.     The  probable  offices  of  this 
secretion  in  the  digestive  process,  have  been  already  noticed  (§§  669,  670). 

6. — Lachrymal  Gland. 

865.  The  Lachrymal  glands  and  their  secretion  may  be  next  mentioned  ; 
but  neither  require  any  lengthened  description.     The  gland  in  Man  is  formed 
very  much  on  the  plan  of  the  Parotid,  being  composed  of  branched  canals 
terminating  in  follicles,  the  ultimate  ramifications  of  the   several  branches 
forming  lobules  or  divisions  of  the  glands.     The  lachrymal  fluid  has  not  re- 
cently undergone  any  accurate  analysis ;  and  all  that  can  be  stated  respecting 
it  is  the  general  fact,  that  the  quantity  of  solid  matter  in  it  is  extremely  small, 
and  that  this  consists  chiefly  of  saline,  and  either  mucous  or  albuminous 
compounds.     It  seems  probable  that  the  secretion  of  the  lachrymal  gland 
itself  is  very  little  else  than  the  serum  of  the  blood,  deprived  of  a  great  part 
of  its  albumen  ;  and  that  the  mucus  of  the  tears  is  secreted  from  the  surface 
of  the  conjunctival  membrane.     This  secretion  has  a  slightly  alkaline  reac- 
tion.    It  is  being  constantly  formed  in  moderate  amount,  for  the  purpose  of 
cleansing  the  surface  of  the  eye  from  the  impurities  which  would  otherwise 
rest  upon  it ;  and  it  is  then  absorbed  by  the  open  orifices  of  the  nasal  duct, 
and  carried  into  the  nose,  as  fast  as  it  is  poured  out.     The  cause  of  this  ab- 
sorption does  not  seem  very  clear.     Capillary  attraction  is  probably  in  part 
concerned ;  and  it  has  been  thought  that  the  momentary  partial  vacuum,  oc- 
casioned by  the  inspiratory  effort  in  all  the  air-passages,  will  cause  the  empty- 
ing of  the  nasal  duct  below,  and  a  consequent  in-draught  above.     The  influ- 
ence of  the  nervous  system  upon  this  secretion  has  been  already  adverted  to 
(§§  625,  626). 

7. — The  Testis. — Spermatic  Fluid. 

866.  In  the  Testes  we  return  to  the  tubular  form  of  glandular  structure, 
which  so  remarkably  distinguishes  the  Kidney  from  all  the  other  glands 


658 


OF  SECRETION. 


hitherto  mentioned.  The  external  forms  presented  by  these  glands  through- 
out the  Animal  kingdom,  are  extremely  various ;  but  their  composition  is  for 
the  most  part  very  uniform.  The  object  is  sometimes  attained  by  a  simple 
but  much  elongated  canal ;  sometimes  by  shorter  branched  tubes ;  and  in 
other  instances,  again,  by  numerous  aggregated  co3ca,  which  are  often  rounded 
into  cells.  In  regard  to  this,  as  to  many  other  glands,  it  may  be  stated  that, 
whilst  its  general  form  in  Insects  is  that  of  prolonged  tubes,  the  required  ex- 
tension of  surface  is  given  in  the  Mollusca  by  the  multiplication  of  cells,  so 
that  the  structure  has  a  compact  spongy  character.  It  is  interesting  to  remark 
that,  in  some  of  the  lowest  Fishes,  this  organ  consists  of  a  mass  of  vesicles 
which  have  no  efferent  duct;  and  that  the  secretion  formed  within  these 
escapes  by  the  rupture  of  the  vesicles,  allowing  it  to  escape  into  the  abdomi- 
nal cavity,  whence  it  passes  by  openings  that  lead  directly  to  the  exterior. 
In  these  Fishes,  the  ova  are  discharged  from  the  ovarium  in  a  very  similar  man- 
ner ;  a  modification  of  which  plan  is  followed  in  all  the  higher  Vertebrata, — 
the  ovum  being  in  them  also  discharged,  by  the  rupture  of  its  containing  vesi- 
cle or  ovisac,  into  the  abdominal  cavity,  but  being  immediately  received  and 
conveyed  away  by  the  funnel-shaped  internal  prolongation  of  the  external  ori- 
fice, which  is  known  as  the  fimbriated  extremity  of  the  Fallopian  tube.* 

a.  The  Testis  in  Man  has  in  every  respect,  however,  a  distinctly  glandular  character.  It 
consists  of  several  lobules,  which  are  separated  from  each  other  by  processes  of  the  tunica 
albuginea  that  pass  down  between  them,  and  also  by  an  extremely  delicate  membrane  (de- 
scribed by  Sir  A.  Cooper  under  the  name  of  tunica  vasculosa)  consisting  of  minute  ramifica- 
tions of  the  spermatic  vessels  united  by  areolar  tissue.  Each  lobule  is  composed  of  a  mass 
of  convoluted  Tubuli  Seminiferi,  throughout  which  blood-vessels  are  minutely  distributed. 


[Fig.  258. 


[Fig.  259. 


The  Testicle  injected  with  mercury;  1,  tunica 
albuginea ;  2,  seminiferous  tubes;  3,  the  rete  vas- 
culosum  testis ;  4,  a  globule  of  mercury  which  has 
ruptured  the  tubes ;  5,  the  vasa  efierentia  which 
form  the  coni  vasculosi;  6,  coni  vasculosi  forming 
the  head  of  the  epididymis;  7,  epididymis  ;  8,  glo- 
bus  minor  of  the  epididymis ;  9,  vas  deferens.] 


A  view  of  the  minute  structure  of  the  Testis  ; 
1,1,  tunica  albuginea;  2,  2,  corpus  highmorianum; 
3,  3,  tubuli  seminiferi  convoluted  into  lobules ;  4, 
vasa  recta ;  5,  rete  testis ;  6,  vasa  efferentia ;  7, 
coni  vasculosi  constituting  the  globus  major  of 
the  epididymis ;  8,  body  of  the  epididymis ;  9,  its 
globus  minor;  10,  vas  deferens  11,  vasculum 
aberrans  or  blind  duct.] 


See  Principles  of  General  and  Comparative  Physiology,  §  641. 


THE  TESTIS SPERMATIC  FLUID. 


659 


The  lobules  differ  greatly  in  size,  some  containing  one,  and  others  many  of  the  tubuli ;  the 
total  number  of  the  lobules  is  estimated  at  about  450  in  each  testis,  and  that  of  the  tubuli  at 
840.  The  convolutions  of  the  tubuli  are  so  arranged,  that  each  lobule  forms  a  sort  of  cone, 
the  apex  of  which  is  directed  towards  the  Rete  Testis.  It  is  difficult  to  trace  the  free  ex- 
tremities of  the  Seminiferous  tubes,  owing  to  the  frequency  of  their  anastomoses  with  each 
other;  in  this  respect,  therefore,  the  structure  of  the  testis  accords  closely  with  that  of  the 

Fig.  260. 


Human  Testis,  injected  with  mercury  as  completely  as  possible;  1, 1,  lobules  formed  of  the  semini- 
ferous tubes;  2,  rete  testis  ;  3,  vasa  efferentia;  4,  flexures  of  the  efferent  vessels  passing  into  the  head, 
5,  5,  of  the  epididymis  ;  6,  body  of  the  epididymis;  7,  appendix  ;  8,  cauda ;  9,  vas  deferens. 

Fig.  261. 


Plan  of  the  structure  of  the  Testis  and  Epididymis;  a,  a,  seminiferous  tubes;  a*,  a*,  their  anasto- 
moses ;  the  other  references  as  in  the  last  figure. 


660  OF  SECRETION. 

Kidney.  The  diameter  of  the  Tubuli  is  for  the  most  part  very  uniform;  in  the  natural  con- 
dition they  seem  to  vary  from  about  the  l-195th  to  the  l-10th  of  an  inch;  but  when  injected 
with  mercury  they  are  distended  to  a  size  nearly  double  the  smaller  of  these  dimensions. 
When  they  have  reached  to  within  a  line  or  two  of  the  Rete  Testis,  they  cease  to  be  con- 
voluted, several  unite  together  into  tubes  of  larger  diameter,  and  these  enter  the  rete  testis 
under  the  name  of  tubuli  recti.  The  rete  teslis  consists  of  from  seven  to  thirteen  vessels, 
which  run  in  a  waving  course,  anastomose  with  each  other,  and  again  divide,  being  all 
connected  together.  The  vasa  efferentia  which  pass  to  the  head  of  the  epididymis  are  at 
first  straight,  but  soon  become  convoluted,  each  forming  a  sort  of  cone,  of  which  the  apex  is 
directed  towards  the  rete  testis,  the  base  to  the  head  of  the  epididymis.  The  number  of 
these  is  stated  to  vary  from  nine  to  thirty ;  and  their  length  to  be  about  eight  inches.  The 
epididymis  itself  consists  of  a  very  convoluted  canal,  the  length  of  which  is  about  twenty-one 
feet.  Into  its  lower  extremity,  that  is,  the  angle  which  it  makes  where  it  terminates  in  the 
vas  deferens,  is  poured  the  secretion  of  the  vasculum  aberrans  or  appendix ;  which  seems 
like  a  testis  in  miniature,  closely  resembling  a  single  lobule  in  its  structure.  Its  special  func- 
tion is  unknown. 

6.  The  Testicles  originate,  in  the  Embryo,  from  the  lower  part  of  the  Corpora  Wolffiana 
(§  839,  c)  ;  arising  from  their  lower  and  inner  sides,  whilst  the  Kidneys  spring  from  their 
upper  and  outer  parts.  They  make  their  first  appearance  in  the  Chick  about  the  fourth  day, 
as  delicate  striae  on  the  Wolffian  bodies ;  and  at  this  period  no  difference  can  be  detected  be- 
tween the  Testes  and  the  Ovaria,  which  originate  in  precisely  the  same  manner.  Like 
the  kidneys,  the  germ-preparing  organs  increase  in  proportion  with  the  diminution  in  the 
temporary  structures ,  at  first  their  efferent  ducts  open  into  those  of  the  Wolffian  bodies,  but 
they  are  subsequently  separated  by  the  formation  of  a  partition,  like  that  which  separates 
the  rectum  from  the  cloaca.  In  the  Human  embryo,  the  rudiments  of  the  sexual  organs, — 
whether  testes  or  ovaria, — first  present  themselves  soon  after  the  kidneys  make  their  appear- 
ance, that  is,  towards  the  end  of  the  seventh  week.  They  are  at  first  much  prolonged,  and 
seem  to  consist  of  a  kind  of  soft,  homogeneous  blastema,  in  which  the  tubular  structure  subse- 
quently developes  itself.  The  Ovary  at  that  period  has  the  same  aspect  and  texture ;  but  its 
subsequent  course  of  development  is  different.  The  Testis  gradually  assumes  its  permanent 
form ;  the  epididymis  appears  in  the  tenth  week ;  and  the  gubernaculum,  (a  membranous 
process  from  the  filamentous  tissue  of  the  scrotum,  analogous  to  the  round  ligament  arising 
from  the  labium,  and  attached  to  the  ovary,  of  the  female,)  which  is  originally  attached  to 
the  vas  deferens,  gradually  fixes  itself  to  the  lower  end  of  the  testis  or  epididymis.  The 
Testes  begin  to  descend  at  about  the  middle  period  of  pregnancy ;  at  the  seventh  month 
they  reach  the  inner  ring ;  in  the  eighth  they  enter  the  passage ;  and  in  the  ninth  they  usually 
descend  into  the  scrotum.  The  cause  of  this  descent  is  not  very  clear.  It  can  scarcely  be 
due  merely,  as  some  have  supposed,  to  the  contraction  of  the  gubernaculum ;  since  that  does 
not  contain  any  fibrous  structure,  until  after  the  lowering  of  the  testes  has  commenced.  It 
is  well  known  that  the  testes  are  not  always  found  in  the  scrotum  at  the  time  of  birth,  even 
at  the  full  period.  Upon  an  examination  of  97  new-born  infants,  Wrisberg  found  both  testes 
in  the  scrotum  in  67, — one  or  both  in  the  canal  in  17, — in  8  one  testis  in  the  abdomen, — and 
in  3  both  testes  within  the  cavity.  Sometimes  one  or  both  testes  remain  in  the  abdomen 
during  the  whole  of  life ;  but  this  circumstance  does  not  seem  to  impair  their  function.  This 
condition  is  natural,  indeed,  in  the  Ram. 

867.  The  fluid  secreted  by  the  Testes  is  thick,  tenacious,  and  of  a  greyish 
or  yellowish  colour.  It  is  mingled,  during  or  before  emission,  with  fluid 
secreted  by  the  Prostate,  Cowper's  glands,  &c. ;  and  it  cannot,  therefore,  be 
obtained  pure,  but  by  drawing  it  from  the  testicle  itself;  hence  no  accurate 
analysis  can  be  made  of  it  in  the  Human  subject.  The  so-called  Spermatozoa 
and  Seminal  Granules,  which  form  the  most  important  and  characteristic  parts 
of  the  Semen,  are  so  intimately  connected  with  the  Reproductive  Function, 
that  they  will  be  more  appropriately  described  under  that  head.  It  may  be  here 
remarked,  however,  that  they  correspond  most  exactly  with  other  Secretions, 
in  their  mode  of  production  ;  for,  as  will  be  shown  hereafter,  they  are  elaborated 
by  cells,  which  lie  within  the  tubuli,  and  which  rupture  so  as  to  set  them  free, 
when  they  are  mature  (§  902).  The  peculiar  odour  which  the  Semen  pos- 
sesses, does  not  appear  to  belong  to  the  proper  spermatic  fluid  ;  but  is  probably 
derived  from  one  or  other  of  the  secretions  with  which  it  is  mingled.  The 
chemical  analyses  which  have  been  made  of  this  fluid  are  all  defective,  inas- 
much as  they  do  not  distinguish  the  real  secretion  of  the  testes  from  the  mucus, 
prostatic  fluid,  &c.,  with  which  it  is  mingled.  It  may  be  stated,  however,  that 


CUTANEOUS  AND  MUCOUS  FOLLICLES. 


661 


it  has  an  alkaline  reaction,  and  contains  albumen,  with  a  peculiar  animal  prin- 
ciple termed  Spermatine  ;  and  also  saline  matter,  consisting  chiefly  of  muriates 
and  phosphates,  especially  the  latter,  which  form  crystals  when  the  fluid  has 
stood  for  some  little  time. 


8. — Cutaneous  and  Mucous  Follicles. 

868.  Having  now  described  the  structure 
and  functions  of  the  principal  Glands,  which 
are  composed  of  aggregated  masses  of  secret- 
ing cells  or  tubes,  we  may  proceed  to  those  in 
which  the  glandulx  are  more  scattered,  but 
are  still,  in  their  aggregate  amount,  of  sufficient 
importance  to  claim  particular  notice.  This 
is  especially  the  case  in  the  Skin,  and  its  in- 
ternal prolongations,  forming  Mucous  Mem- 
branes. The  Skin  is  the  seat  of  various  secre- 
tions ;  for  each  of  which  it  is  provided  with 
special  organs.  Of  these  the  most  important 
is  the  Perspiration;  which  is  formed  in  small 
glandular  organs  seated  just  beneath  the  cutis, 
and  diffused  over  the  whole  surface  of  the 
body.  The  efferent  ducts  of  these  Glandulae 
open  by  minute  pores  in  the  Epidermis,  which 
are  seen  in  elevated  lines  on  the  skin  of  the 
palm  of  the  hand  and  the  sole  of  the  foot ;  they 
penetrate  the  epidermis  rather  obliquely,  so 
that  a  sort  of  little  valve  is  formed  by  it,  which 
is  lifted  up  by  the  excreted  fluid  as  it  issues. 
The  ducts  pass  through  the  Epidermis  and 
Cutis  in  a  spiral  direction;  and  then  enter  the 
glands,  which  consist  of  the  convolutions  of 
the  ducts,  more  or  less  subdivided,  on  which 
blood-vessels  are  distributed.  Where  the 
Epidermis  is  thin,  the  canal  is  straighter.*—  On 
the  palm  of  the  hand,  the  sole  of  the  foot,  and 
the  extremities  of  the  fingers,  the  apertures  of 
the  perspiratory  ducts  are  visible  to  the  naked 
eye ;  being  situated  at  regular  distances  along 
the  little  ridges  of  sensory  papillae,  and  giving 
to  the  latter  the  appearance  of  being  crossed 
by  transverse  lines.  According  to  Mr.  Eras- 
mus Wilson,*  as  many  as  3528  of  these 
fflandulae  exist  in  a  square  inch  of  surface  on 

1  f*       1  1  •»  -I  i  -1  OUUUI  IlCH-fU.0     V-i  10.1HJ.    iiwm     1.1^     ^i*..."     ~» 

the  palm  of  the  hand  ;  and  as  every  tube,  when  the  hand>  magnified  40  diameters ;  i,  i, 

straightened  out,  is  about  a  quarter  of  an  inch  contorted  tubes,  composing  the  gland, 

in  length,  it  follows  that,  in  a  square  inch  of  and  uniting  into  two  excretory  ducts,  a, 

skin  from  the  palm  of  the  hand,  there  exists  a  2,  which  unite  into  one  spiral  canal,  that 

T          ,       c      i  i  ,     ooo  •      i  *oi   c     i      perforates  the  epidermis  at  3,  and  opens 

length  Of  tube  equal  tO  883  inches,  or  73£  feet,    ^n  its  surface  at 4;  the  gland  is  imbedded 
The  number  of  glandulcB  in  Other  parts  of  the    in  fat-vesicles,  which  are  seen  at  5,  5. 

skin,  is  sometimes  greater,  but  generally  less 

than  this ;   and  according  to   Mr.  Wilson,  about  2800  may  be  taken  as  the 

average  number  of  pores  in  each  square  inch  throughout  the  body.     Now  the 


Sudoriferous  Gland  from  the  palm  of 


Practical  Treatise  on  Healthy  Skin,  p.  42. 


56 


662 


OF  SECRETION. 


[Fig.  263. 


[Fig.  265. 


Vertical  section  of  the  skin 
and  sweat-glands  of  the  axilla ; 
—a.  Layer  of  glands  with  their 
ducts  traversing  ft,  the  cutis  and 
cuticle,  c.  Small  hair,  d,  d. 
Portions  of  larger  hairs.— 
Magn.  one  and  a  half  diam.] 


[Fig.  264, 


Sweat-gland  and  the  commencement  of  its 
duct : — a.  Venous  radicles  on  the  wall  of  the 
cell  in  which  the  gland  rests.  This  vein  anas- 
tomoses with  others  in  the  vicinity,  b.  Capilla- 
ries of  the  gland  separately  represented,  arising 
trom  their  arteries,  which  also  anastomose. 
The  blood-vessels  are  all  situated  on  the  outside 
or  deep  surface  of  the  tube,  in  contact  with  the 
basement-membrane. — Magn.  35  diam.] 


a.  Vertical  section  of  the  cuticle  from  the  heel, 
detached  by  maceration.  The  epithelium  of  the 
sweat-duct,  continuous  with  the  cuticle,  has  been 
drawn  out  of  the  tube  of  basement-membrane,  as 
far  as  the  gland,  where  it  begins  to  be  contorted. 
The  cavity  of  the  duct  is  seen  dilating  as  it  enters 
the  cuticle,  and  then  stretching  up  to  the  surface 
through  the  epidermic  laminae.  The  deep  surface 
of  the  duct  is  continuous  with  the  surface  of  the 
cavities  in  which  the  papillae  are  lodged.— Magn. 
35  diameters. 

6.  Duct  at  its  entrance  into  the  cuticle.— More 
highly  magnified.] 


number  of  square  inches  of  surface,  in  a  man  of  ordinary  stature,  is  about 
'2500 ;  the  total  number  of  pores,  therefore,  may  be  about  seven  millions ; 
and  the  length  of  the  perspiratory  tubing  would  thus  be  1,750,000  inches,  or 
145,833  feet,  or  48,611  yards ;  or  nearly  28  miles. 

869.  The  Secretion  of  fluid  by  these  Glands  is  continually  taking  place ; 
but  this  fluid,  being  usually  carried  off  in  the  form  of  vapour  "as  fast  as  it  is 
separated,  does  not  accumulate  and  become  sensible.  If,  however,  from  the 
increased  amount  of  the  secretion,  or  from  the  condition  of  the  surrounding 
air,  the  whole  fluid  thus  poured  out  should  not  evaporate,  it  accumulates  in 


CUTANEOUS  AND  MUCOUS  FOLLICLES.  663 

minute  drops  upon  the  surface  of  the  skin.  Thus  the  Sudoriferous  excretion 
may  take  the  form  either  of  sensible  or  insensible  transpiration ;  the  latter 
bemg  constant,  the  former  occasional.  It  is  difficult  to  obtain  enough  of  this 
secretion  for  analysis,  free  from  the  sebaceous  and  other  matters  which  accu- 
mulate on  the  surface  of  the  skin ;  and  its  character  can  only,  therefore,  be 
stated  approximately.  It  has  usually  an -acid  reaction,  which  seems  due  to 
the  presence  of  acetic  acid ;  and  to  this,  or  to  lactic  acid,  we  are  probably  to 
attribute  the  sour  smell  which  it  has,  especially  in  some  disordered  states  of 
the  system.  The  proportion  of  solid  matter,  according  to  Anselmino,  varies 
between  5  and  12*5  parts  in  1000.  The  greatest  part  of  it  consists  of  animal 
matter,  wKl6h»is.agpaj;ently  a  proteine-compound  in  a  state  of  incipient  decom- 
position. The  remaTMer.  consists  'of  saline  compounds ;  of  which  the  chlorides 
of  potassium  and  sodium  appear  to  be  pretty  constantly  present ;  whilst  the 
muriate  of  ammonia,  free  acetic  acid,  and  acetate  of  soda,  have  also  been  said 
to  occur  in  it. — The  proportion  of  these  ingredients  would  probably  be  found 
larger  in  the  fluid  of  the  Sudoriferous  glands,  if  we  had  the  means  of  collecting 
it  separately ;  for  of  the  whole  fluid  which  passes  off  from  the  surface  of  the 
skin,  only  a  small  proportion  can  be  properly  said  to  be  secreted  by  the  Sudo- 
riferous glands ;  the  greater  part,  under  ordinary  circumstances,  being  the 
product  of  simple  Evaporation,  by  which,  of  course,  nothing  but  pure  watery 
vapour  is  dissipated. 

870.  The  entire  amount  of  fluid  which  is  insensibly  lost  from  the  Cutaneous 
and  Pulmonary  surfaces,  is  estimated  by  Seguin  at  18  grains  per  minute ;  of 
which  11  grains  pass  off  by  the  skin,  and  7  by  the  lungs.     The  maximum 
loss  by  Exhalation,  cutaneous  and  pulmonary,  during  twenty-four  hours,  (ex- 
cept under  very  peculiar  circumstances,)  is  5  Ibs. ;  the  minimum  If  Ib.     It 
varies  greatly,  according  to  the  condition  of  the  atmosphere,  and  that  of  the 
body  itself.    The  manner  and  degree  in  which  it  is  influenced  by  atmospheric 
conditions,  will  be  better  discussed  under  the  head  of  Animal  Heat  (§  897) ; 
since  this  influence  has  a  most  important  effect  in  the  regulation  of  the  tem- 
perature of  the  body.     As  already  pointed  out,  the  Urinary  excretion  is  in 
great  degree  vicarious  with  it,  in  regard  to  the  amount  of  fluid  discharged, — 
the  urine  being  more  watery  in  proportion  as  the  Cutaneous  Exhalation  is 
diminished  in  amount, — and  vice  versa  (§  840).     But  we  are  also  to  look  at 
these  two  excretions  as  vicarious,  in  regard  to  the  deportation  (or  getting  rid) 
of  the  products  of  the  waste  of  the  system.     The  share  which  the  Skin  has 
in  this  office  has  probably  been  generally  under-rated.     There  is  reason  to 
believe  that  at  least  100  grains  of  azotized  matter  are  excreted  from  it  daily; 
and  any  cause  which  checks  this  excretion,  must  throw  additional  labour  on 
the  kidneys,  and  will  be  likely  to  produce  disorders  of  their  function. 

871.  The  Exhalant  action  of  the  Skin  is  influenced  by  general  conditions  of 
the  vascular  and  nervous  systems ;  which  are  as  yet  ill  understood.    It  is  quite 
certain,  however,  that  through  the  influence  of  the  latter  the  secretion  may 
be  excited  or  suspended  ;  this  is  seen  on  the  one  hand  in  the  state  of  syncope, 
and  the  effects  of  depressing  emotions,  especially  fear,  and  its  more  aggravated 
condition,  terror ;  and  on  the  other  in  the  dry  condition  of  the  skin  during 
states  of  high  nervous  excitement.    It  is  very  probable  that,  in  many  forms  of 
fever,  the  suppression  of  the  perspiration  is  a  cause,  rather  than  an  effect,  of 
disordered  vascular  action ;  for  there  are  several  morbid  conditions  of  large 
parts  of  the  surface,  in  which  the  suppression  of  the  transpiration  appears  to 
be  one  of  the  chief  sources  of  danger,  having  a  tendency  to  produce  congestion 
and  inflammation  of  internal  organs.     From  the  recent  experiments  of  Dr. 
Fourcault,*  it  appears  that  complete  suppression  of  the  Perspiration  in  animals, 

*  Comptes  Rendus  de  1' Academic,  May,  1844;  and  Lancet,  June  8,  1844. 


664 


OF  SECRETION. 


by  means  of  a  varnish  applied  over  the  skin,  gives  rise  to  a  state  termed  by 
him  Cutaneous  Asphyxia  ;  which  is  marked  by  imperfect  arterialization  of  the 
blood,  and  considerable  fall  of  temperature  (§§  768,  891);  and  which,  as- it 
produces  death  in  the  lower  animals,  would  probably  do  the  same  in  Man. 
A  partial  suppression  by  the  same  means  gives  rise  to  Febrile  symptoms,  and 
to  Albuminuria. 

872.  The  Skin  is  likewise  furnished  with  numerous  Sebaceous  glands,  also 
distributed  more  or  less  closely  throughout  the  whole  surface  of  the  body.  By 
these  an  Adipose  secretion  is  poured  forth,  which  keeps  the  skin  from  being 
dried  and  cracked  by  the  action  of  the  sun  and  air.  It  is  especially  abundant 
in  the  races  which  are  formed  to  inhabit  warm  climates.  Some  of  these  glan- 

[Fig.  266. 


Sebaceous  glands,  showing  their  size  and  relation  to  the  hair- follicles :— 4.  and  B  from  the  nose ;  c  from 

the  beard.    In  the  latter  the  cutis  sends  down  an  investment  of  the  hair-follicle. — Magn.  IS  diam.] 

\ 

dulae  are  simple  follicles  lined  with  secreting  cells,  and  contained  in  the  sub- 
stance of  the  Skin  itself;  whilst  others  are  formed  out  of  similar  follicles,  more 
or  less  branched,  elongated,  and  convoluted ;  and  others,  again,  seem  to  con- 
sist of  little  else  than  clusters  of  Fat  cells,  from  one  part  of  which  an  excretory 
duct  arises:  these  last  commonly  open  into  the  passage,  by  which  the  Hair 
makes  its  way  outwards.  Besides  these  there  are  other  glands  situated  in 
particular  parts  of  the  body,  and  having  special  functions.  Such  are  the  Ceru- 
minous  glands  situated  beneath  the  skin  of  the  auditory  meatus ;  these  are 
closely  analogous  in  form  to  the  sudoriferous  glands,  as  the  accompanying 
figure  shows  ;  but  their  secretion  is  very  different,  being  nearly  solid,  and 
having  somewhat  of  a  resinous  character. — A  peculiar  series  of  glandulae, 
bearing  a  general  resemblance  to  the  sudoriferous  glands,  but  of  larger  size, 
have  lately  been  discovered  by  Prof.  Homer*  and  M.  Robin  to  exist  in  the 
human  axillae ;  where  they  probably  serve  to  secrete  the  peculiar  odorous 
matter,  characteristic  of  that  part.  In  many  of  the  lower  animals,  such  glands 
maybe  detected,  having  a  structure  of  considerable  complexity.  The  odorous 
secretion  would  appear  to  be  elaborated  from  the  blood  by  a  simple  chemical 
change;  for  it  may  be  made  evident  even  in  blood  that  has  been  dried  up,  by 

*  [Am.  Journ.  Med.  Science,  Jan.  1846,  p.  13.] 


CUTANEOUS  AND  MUCOUS  FOLLICLES. 

Fig.  267. 


665 


Cutaneous  glands  of  external  meatus  auditorius.— 1.  Section  of  the  skin,  magnified  three  diameters  ; 
2,  2,  hairs ;  3,  3,  superficial  sebaceous  glands ;  1, 1,  larger  and  deeper-seated  glands,  by  which  the  ceru- 
men is  secreted.— 2.  A  hair,  perforating  the  epidermis  at  3 ;  1,  1,  sebaceous  glands,  with  their  excretory 
ducts  2,2;  4,  base  of  the  hair,  in  its  double  follicle  5,5. — 3.  Cerumen-gland,  formed  by  the  contorted 
tube,  1, 1,  of  the  excretory  duct,  2;  3,  vascular  trunk  and  ramifications. — The  last  two  figures  highly 
magnified. 

[Fig.  268. 


Cutaneous  Follicles  or  Glands  of  the  Axilla,  magnified  one-third.— (Homer.)] 

treating  it  with  sulphuric  acid.  This  aromatic  principle  differs  sufficiently  m 
the  blood  of  different  animals,  to  enable  a  person  with  a  delicate  sense  of 
smell  to  determine  from  what  animal  any  specimen  has  been  procured  ;  and 
this  fact  has  been  applied  with  success  to  juridical  investigations.  It  has  even 

56* 


666 


OF  SECRETION. 


been  stated  that  the  blood  of  the  human  Male  may  be  distinguished  from  that 
of  the  Female,  by  its  more  powerful  odour;  but  this  does  not  appear-  to  be 
the  case. — at  least  with  sufficient  certainty  for  medico-legal  inquiries.* 

873.  Besides  the  crypts  or  follicles,  which  have  been  spoken  of  as  gene- 
rally existing  in  Mucous  Membranes  (§  178),  there  exist,  in  that  of  the  Intes- 
tinal Canal,  numerous  glandulae  in  various  parts,  for  the  elaboration  of  par- 
ticular secretions.  In  the  Stomach,  for  example,  a  large  number  of  these 
secreting  organs,  some  of  them  possessing  rather  a  complex  structure,  are 
included  in  the  thickness  of  its  walls,  composing,  indeed,  the  greater  part  of 
the  mucous  membrane.  If  this  be  divided  by  a  section  perpendicular  to  its 
surface,  it  is  seen  to  be  made  up  of  a  number  of  tubuli  closely  applied  to  each 
other,  their  blind  extremities  being  in  contact  with  the  submucous  tissue,  and 
their  open  ends  being  directed  towards  the  cavity  of  the  stomach.  In  some 
situations,  these  tubuli  are  short  and  straight ;  in  other  parts  they  are  longer, 
and  present  an  appearance  of  irregular  dilatation  or  partial  convolution.  This, 
indeed,  is  their  usual  character,  especially  towards  the  cardiac  orifice  of  the 


Fig.  269. 


Section  of  the  coats  of 
the  stomach,  near  the  py- 
lorus, showing  the  gastric 
glands,  1,  magnified  three 
times.  2,  magnified  twenty 
times. 


[Fig.  270. 


A.  Horizontal  section  of  a  stomach-cell,  a 
little  way  within  its  orifice,    a.  Basement- 
membrane,     b.  Columnar  epithelium.     All 
but  the  centre  of  the  cavity  of  the  cell  is  oc- 
cupied by  transparent  mucus,  which  seems 
to  have  oozed  from  the  open  extremities  of 
the  epithelial  particles,     c.  Fibrous  matrix 
surrounding  and  supporting  the  basement- 
membrane,    d.  Small  blood-vessel. 

B.  Horizontal  section  of  a  set  of  stomach 
tubes  proceeding  from  a  single  cell.    The 
letters  refer  to  corresponding-  parts.     The 
epithelium  is   glandular;    the  nuclei   very 
delicate ;  the  cavity  of  the  tubes  very  small, 
and  in  some  cases  not  visible. 

From  the  dog,  after  twelve  hours'  fasting. 
Magnified  200  diameters.] 


*  See  Annales  d'Hygiene,  vol.  j.  pp.  267  and  548;  vol.  ii.  p.  217;  vol.  x.  p.  160,  &c. 


CUTANEOUS  AND  MUCOUS  FOLLICLES. 


667 


stomach.  On  the  other  hand,  towards  the  pyloric  extremity,  they  have  a 
much  more  complex  structure.  Betweeen  the  tubuli,  blood-vessels  pass  up 
from  the  sub-mucous  tissue,  and  form  a  vascular  net-work  on  its  surface. 
From  the  examination  of  these  horizontal  sections  of  the  mucous  membrane 
at  various  depths,  Dr.  Todd*  has  ascertained  that  the  tubuli  are  arranged  in 
bundles  or  groups,  surrounded  and  bound  together  by  a  fine  areOlar  mem- 
brane ;  the  size  of  the  bundles,  and  the  number  of  tubules  contained  in  them, 
vary  considerably.  The  tubes  do  not,  in  general,  open  directly  upon  the 
surface,  but  into  the  bottom  of  small  depressions  or  pits,  which  may  be  seen 
to  cover  the  membrane.  These  pits  are  more  or  less  circular  in  form,  and 
are  separated  from  one  another  by  partition-like  elevations  of  the  membrane, 
which  vary  in  depth  ;  and  sometimes  even  by  pointed  processes,  that  have 
been  mistaken  by  some  anatomists  for  villi.  The  diameter  of  these  pits 
varies  from  about  l-100th  to  l-250th  of  an  inch;  it  is  always  greatest  near 


[Fig.  271. 


Fig.  272. 


[Fig.  273. 


Portion  of  the  mucous 

membrane  of  the  stomach, 

showing  entrances  to  the 

A     secreting   tubes,   in  pits 

upon  its  surface. 


A.  Inner  surface  of  the  stomach,  showing 
the  cells  after  the  mucus  has  been  washed 
out.    Magnified  25  diameters. 

B.  Columnar  epithelium  of  the  inner  sur- 
face and  cells  of  the  stomach:— a.  Free 
ends  of  the  epithelial   particles,  seen  on 
looking  down  upon  the  membrane,    b.  Nu- 
clei visible  at  a  deeper  level,    c.  The  free 
ends  seen  obliquely,    d.  Deep  or  attached 
ends  of  the  same.   The  oval  nuclei  are  seen 
near  the  deeper  ends. 

From  the  dog.    Magnified  300  diameters.] 

*  Gulstonian  Lectures  <*n  the  Physiology  of  the  Stomach,  in  Medical  Gazette,  1839. 
See  also  Dr.  Sprott  Boyd's  Inaugural  Dissertation  on  the  Mucous  Membrane  of  the  Stpmach, 
in  Edinb.  Med.  and  Surg.  Journal,  vol.  xlvi. 


Vertical  section  of  a  stomach  cell,  with  its 
tubes  :  A  in  the  middle  region,  B  in  the  pyloric 
region,  a  a.  Orifices  of  the  cells  on  the  inner 
surface  of  the  stomach.  6  6.  Different  depths  at 
which  the  columnar  epithelium  is  exchanged 
for  glandular,  c.  Pyloric  tube,  or  prolonged 
stomach  cell.  d.  Pyloric  tubes,  terminating 
variously,  and  lined  to  their  extremities  with 
sub-columnar  epithelium. 

From  the  dog,  after  twelve  hours'  fasting. 
Magnified  200  diameters.] 


668 


OF  SECRETION. 


[Fig.  274. 


the  pylorus.  When  the  surface  of  the  membrane,  cleansed  from  mucus  and 
epithelium-scales,  is  examined  with  a  sufficient  magnifying  power,  it  is  seen 
that  from  three  to  five  perforations  exist  in  the  bottom  of  each  pit ;  and  these 
are  the  openings  of  the  secreting  tubes.  The  Gastric  fluid,  elaborated  by  this 
apparatus,  having  been  already  made  a  subject  of  special  consideration  (§  664) 
need  not  be  here  described. 

874.  The  whole  Mucous  sur- 
face of  the  Intestinal  canal  is  fur- 
nished with  glandular  follicles  of 
a  very  similar  character;  of  which 
some  approach  those  of  the  sto- 
mach in  complexity  of  structure ; 
whilst  others  evidently  corre- 
spond with  the  crypts  of  ordinary 
Mucous  Membrane.  An  innu- 
merable multitude  of  pores  are 
easily  seen,  by  the  aid  of  a  sim- 
ple lens,  to  cover  the  whole  in- 
ternal.surface  of  the  large  Intes- 
tine ;  and  these  are  the  entrances 
to  tubular  follicles,  closely  resem- 
bling those  of  the  stomach,  but 
more  simple  in  structure.  Their 
coecal  extremities  abut  against  the 
sub-mucous  tissue :  towards  the 
end  of  the  Rectum,  however, 
they  are  much  prolonged,  and 
constitute  a  peculiar  layer  be- 
tween the  mucous  and  muscular 
coats;  the  tubes  which  are  there 
visible  to  the  naked  eye,  being 
erect,  parallel,  and  densely  crowd- 
ed. These  glands  probably  form 
the  peculiarly  thick  and  tenacious 
mucus  of  the  large  intestine.  In 
the  small  intestine,  on  the  other 
hand,  the  coeca  are  less  deep  and 
their  apertures  are  smaller.  These 
apertures  are,  for  the  most  part, 
situated  around  the  bases  of  the 
villi :  in  the  fo3tus  and  newly-born  child,  they  are  so  abundant  as  to  be  almost 


A  section  of  the  Ileum,  inverted  so  as  to  show  the  ap- 
pearance and  arrangement  of  the  villi  on  an  extended 
surface,  as  well  as  the  follicles  of  Lieberkiihn  ;  the  whole 
seen  under  the  microscope.  A  close  examination  of  this 
cut  will  show  a  great  number  of  black  points  in  the 
spaces  between  the  projections  of  villi :  these  are  the 
follicles  of  Lieberkiihn.] 


Fig.  275. 


Fig.  276. 


One  of  the  glandulae  majores  sim- 
plices.  viewed  from  above  at  A,  and 
seen  in  section  at  B  ;  from  the  large 
intestine. 


Mucous  coat  of  small  intestines  as 
altered  in  f»ver ;  the  follicles  of  Lie- 
berkiihn filled  with  tenacious  white 
secretion. 


CUTANEOUS  AND  MUCOUS  FOLLICLES. 


669 


[Fig.  277. 


in  contact ;  but  in  the  adult,  the  intervals  increase,  so  as  to  occupy  more 
space  than  the  apertures.  The  glandulae  of  the  small  intestines  have  long 
been  known  under  the  name  of  the  follicles  of  Lieberkiihn  ;  they  become 
particularly  evident  (Fig.  275)  when  the  mucous  membrane  is  inflamed,  being 
then  filled  with  an  opaque  whitish  secre- 
tion, which  is  absent  in  the  healthy  state. 
— Besides  the  foregoing  descriptions  of 
solitary  glandulae,  the  Ccecum  and  the 
lower  part  of  the  Rectum  contain  a  num- 
ber of  simple  and  large  follicles,  which 
produce  slight  rounded  elevations  on  the 
surface  of  the  mucous  membrane ;  the 
centre  of  each  of  these  elevations  is  per- 
forated by  an  aperture  of  the  follicle ;  and 
around  this  are  seen  the  orifices  of  the 
tubular  coeca,  which  closely  envelope 
the  globular  follicle  (Fig.  270).  These 
seem  most  abundant  where  the  largest 
quantity  of  mucus  is  required.  They 
have  been  confounded  with  the  glands  of 
Brunner ;  but  are  rather  analogous  to  the 
solitary  Peyerian  glands,  presently  to  be 
noticed. 

875.    The  true  glands  Of  Brunner  are        A  section  of  the  small  Intestine  containing 

chiefly  situated  in  the  Duodenum  ;  and  some  of  the  elands  of  Peyer> as  shown  und°r 


the 


Fig.  278. 


they  lie  not  in  the  mucous  but  in  « 

Sub-mUCOUS    tiSSUe,   where    they    form    a  cording  to  Boehm,  a  white,  milky  and  rather 

Continuous    layer   of    white    bodies    Stir-  thick  fluid,  with  numerous  round  corpuscles  of 

rounding   the     whole    intestine.        Their  various  sizes,  but  mostly  smaller  than  blood- 

size,  unless  diseased,  is   scarcely  that  of  globules.    The  meshes  seen  in  the  cut  are  the 

a  hemp-seed;  each   consists  of  nmne- 

rous  minute  lobules,  of  which  the  ducts 

open  into  a  common  excretory  tube  ; 

and  in  the  lobules  may  be  distinguished  the  minute  ramifications  of  these 

ducts,  with  clusters  of  follicles  forming  acini,  of  which  about  six  hundred 

are  computed  to  exist  in  each.     Hence  these  glands 

are  of  complex  structure,  much  resembling  that  of  the 

Salivary  glands  and  Pancreas,  and  entirely  differing 

from  all  the  other  glandulae  of  the  walls  of  the  ali- 

mentary canal.     Of  the  peculiar  nature  of  their  secre- 

tion nothing  is  known. 

876.  The  so  called  Peyerian  glands  constitute, 
when  aggregated  together,  large  patches  on  the  mucous 
membrane  of  the  small  intestine,  where  they  are 
known  as  the  glandulsc  agminatx  ;  and  it  is  to 
these  alone  that  Peyer's  name  is  usually  applied. 
Similar  bodies,  however,  known  as  the  glandulse 
solitarise,  exist  separately  in  the  lower  part  of  the 
small  intestines  ;  where  they  have  been  confounded  with  the  glands  of  Brun- 
ner, which  do  not  extend  beyond  the  commencement  of  the  Jejunum.  The 
glands  of  Peyer,  when  examined  in  a  healthy  mucous  membrane,  present  the 
appearance  of  circular  white  slightly-raised  spots,  about  a  line  in  diameter, 
over  which  the  membrane  is  usually  less  set  with  villi,  and  very  often  entirely 
free  from  them.  Each  of  these  white  spots,  of  which  a  large  number  are 
contained  in  the  agminated  glands,  is  surrounded  by  a  zone  of  openings  like 


Conglomerate  gland  of 
Brunner,  from  commence- 
ment of  duodenum;  mag- 
nified a  hundred  limes. 


670 


OF  SECRETION. 


Fig.  279. 


Portion  of  one  of  the  patches  of  Peyer's  glands, 
from  the  end  of  the  Ileum,  highly  magnified  ;  the  villi 
are  also  displayed. 


those  of  the  follicles  of  Lieberkuhn,  which  lead  (as  do  those)  into  tubular 
cceca.     On  rupturing  the  surface  of  one  of  the  white  bodies,  there  is  found  a 

cavity,  corresponding  in  extent  with 
the  spot,  and  of  considerable  extent; 
but  this  cavity  has  usually  no  ex- 
cretory opening,  and  the  tubular  fol- 
licles by  which  it  is  surrounded, 
have  no  connection  with  it.  In  its 
interior  is  found  a  grayish-white 
mucous  matter,  interspersed  with 
cells  in  various  stages  of  develop- 
ment. There  is  reason  to1  believe 
that,  at  a  certain  period  of  the  ex- 
istence of  each  of  these  glandulae, 
an  excretory  orifice  is  formed,  by  a 
sort  of  dehiscence  in  the  wall  of  the 
cavity ;  and'  that,  through  this,  the 
product  secreted  by  the  contained 
cells  may  be  poured  forth.  Each 
of  them  may  be  compared,  on  this 
view,  to  one  of  the  ultimate  folli- 
cles, which  constitutes  the  secreting 
portion  of  any  one  of  the  larger 
glands  (§  823) ;  the  only  difference  being,  that  the  latter  are  situated  at  the 
extremities  of  the  ramifying  ducts,  by  which  their  product  is  collected  and 
conveyed  away;  whilst  the  former  pour  their  secretion  at  once  into  the 
cavity  of  the  intestine. — The  membrane  which  covers  in  the  cavity  is  ex- 
tremely thin,  and  is  very  liable  to  be  destroyed  by  ulceration  ;  hence  it  is,  that, 
after  inflammation  of  the  enteritic  mucous  membrane,  the  patches  of  Peyer 
are  often  to  be  seen  as  a  congeries  of  shallow  open  cells  or  follicles. 

877.  Although  the  particular  use  of  each  variety  of  the  Intestinal  glandulae 
cannot  yet  be  determined,  there  seems  little  doubt  that  their  general  function 
is,  to  eliminate  from  the  Blood  those  putrescent  matters  which  would  other- 
wise accumulate  in  it;  whether  as  one  of  the  results  of  the  normal  waste  of 
the  system, 'or  as  produced  by  various  morbific  causes,  which  act  as  ferments, 
and  thus  occasion  an  unusual  tendency  to  decomposition  in  the  solids  and 
fluids  of  the  body.  That  the  putrescent  elements  of  the  faeces  are  not  imme- 
diately derived  from  the  food  taken  in,  so  much  as  from  the  excreting  action 
of  the  Intestinal  .Glandulae,  appears  from  this  consideration,  among  others ; — 
that  faecal  matter  is  still  discharged,  even  in  considerable  quantities,  long  after 
the  intestinal  tube  has  been  completely  emptied  of  its  alimentary  contents. 
We  see  this  in  the  course  of  many  diseases,  when  food  is  not  taken  for  many 
days,  during  which  time  the  bowels  have  been  completely  emptied  of  their 
previous  contents  by  repeated  evacuations ;  and  whatever  then  passes,  in  ad- 
dition to  the  biliary  and  pancreatic  fluids,  must  be  derived  from  the  intestinal 
walls  themselves.  Sometimes  a  copious  flux  of  putrescent  matter  continues 
to  take  place  spontaneously ;  whilst  it  is  often  produced  by  the  agency  of 
purgative  medicine.  The  "colliquative  diarrhea,"  which  frequently  comes 
on  at  the  close  of  exhausting  diseases,  and  which  usually  precedes  death  by 
starvation,  appears  to  depend,  not  so  much  upon  a  disordered  state  of  the 
intestinal  glandulae  themselves,  as  upon  the  general  disintegration  of  the  solids 
of  the  body,  which  calls  them  into  extraordinary  activity  for  the  purpose  of 
separating  the  decomposing  matter. 


GENERAL  REVIEW  OF  THE  NUTRITIVE  PROCESSES.  671 


CHAPTER    XVI. 

* 

GENERAL   REVIEW    OF    THE    NUTRITIVE    PROCESSES. ANIMAL    HEAT. 

\.~Review  of  the  Nutritive  Processes,  with  Practical  Applications. 

878.  THE  detailed  survey  which  has  been  now  taken,  of  the  different 
Functional  operations  concerned  in  maintaining  the  life  of  the  individual, 
may  suggest  to  us  some  general  views  that  have  important  practical  applica- 
tions. In  the  first  place,  it  has  been  shown,  that  the  province  of  the  Animal 
is  not  to  combine  Inorganic  elements  into  Organic  compounds,  fit  to  be  ap- 
plied to  the  purposes  of  Nutrition ;  but  to  use  those  which  are  prepared  for 
it  by  the  Plant.  The  nutritive  materials  thus  obtained  may  be  divided  into 
two  great  classes,  the  azotized  and  the  non-azotized.  The  former  have  been 
shown  (§  642)  to  be  so  nearly  identical  in  composition  with  the  proximate 
principles  of  which  the  Animal  body  is  composed,  that  no  great  amount  of 
chemical  transformation  can  be  required  to  prepare  them  for  being  appropri- 
ated by  it.  The  latter  are  altogether  different  in  character;  and  whether  or 
not  they  can,  by  any  process  of  transformation,  be  made  subservient  to  the 
nutrition  of  the  Azotized  tissues,  it  is  unquestionable  that  their  ordinary  use 
is  to  serve  as  the  materials  for  the  Respiratory  process,  and  for  the  mainte- 
nance of  Animal  heat.  The  demand  for  these  several  articles  in  the  system 
will  depend,  in  regard  to  the  former,  upon  the  amount  of  Tissue  which  has 
been  disintegrated  and  needs  repair;  and  with  respect  to  the  latter,  upon  the 
amount  of  Heat  which  it  is  necessary  to  generate,  to  keep  up  the  tempera- 
ture of  the  body  to  its  regular  standard.  Hence  a  highly-azotized  diet  is 
most  required  when  the  greatest  amount  of  muscular  exertion  is  being  used ; 
whilst  a  diet,  in  which  non-azotized  substances  are  predominant,  will  serve 
to  sustain  the  Animal  Heat  in  a  cold  atmosphere.  The  adjustment  of  the 
diet  to  the  wants  of  the  system,  is  a  matter  of  the  greatest  importance  for 
the  preservation  of  health.  If  too  great  an  amount  of  azotized  food  be  in- 
gested, and  the  superfluity  be  thrown  upon  the  Kidneys  to  eliminate  (§  850), 
disorder  of  the  Urinary  Secretion  is  almost  certain,  sooner  or  later,  to  mani- 
fest itself.  The  quantity  of  Lithic  Acid,  in  particular,  undergoes  considerable 
increase;  and,  by  the  removal  of  its  bases  through  the  increased  production 
of  other  acids,  it  is  very  likely  to  pass  out  in  an  insoluble  state,  giving  rise  to 
Gravelly  deposits.  Or  it  may  accumulate  in  the  Blood,  and  there  combine 
with  Soda;  forming  a  salt  which  is  deposited  in  various  parts  (especially  in 
the  neighbourhood  of  the  smaller  joints),  forming  concretions,  which  are  com- 
monly known  tinder  the  name  of  "chalk-stones."  These  deposits  usually 
take  place,  however,  after  severe  attacks  of  a  peculiar  Inflammation,  known 
as  Gout;  and  this  inflammation  seems  to  be  connected  with  the  accumulation 
of  Lithate  of  Soda  in  the  Blood. — Over  this  disease  a  careful  regulation  of 
the  diet  exercises  a  powerful  control.  A  patient  affected  with  the  "  Lithic 
Acid  diathesis,"  may  palliate,  if  not  altogether  cure  his  disorder,  by  rigorously 
abstaining  from  the  use  of  any  superfluous  amount  of  azotized  compounds 
as  food ;  and  by  subsisting  as  much  as  possible  upon  those  belonging  to  the 
Farinaceous  group.  It  is  by  no  means  every  case,  however,  that  is  capable 
of  alleviation  by  treatment  of  this  sort ;  in  fact,  it  can  seldom  be  rigorously 


672  GENERAL  REVIEW  OF  THE  NUTRITIVE  PROCESSES. 

enforced,  except  in  early  life,  or  at  any  rate  when  the  constitution  is  unbroken 
by  disease  or  intemperance.  Not  unfrequently  it  will  be  found,  that  the  per- 
sistence in  a  diet  of  this  kind,  occasions  so  much  disorder  of  the  stomach,  as 
to  be  quite  out  of  the  question. — On  the  other  hand,  in  the  "  Strumous  dia- 
thesis," there  would  seem  to  be  a  low  condition  of  those  vital  powers,  which 
are  concerned  in  the  conversion  of  the  Albuminous  materials  prepared  by 
the  Digestive  process,  into  the  Fibrinous  matter  which  is  ready  for  assimila- 
tion;  so  that,  by  a  perversion  of  the  ordinary  nutrient  actions,  Albuminous 
Tubercle  is  deposited  in  the  interstices  of  the  tissues,  instead  of  these  tissues 
being  themselves  regenerated  by  Organizable  Fibrine ;  and  the  same  may 
take  place  in  a  more  rapid  manner,  in  consequence  of  that  disturbance  of  the 
nutrient  processes,  which  is  known  in  healthy  constitutions  as  Inflammation 
(§  802).  It  is  obvious,  then,  that  the  treatment  of  the  Strumous  Diathesis 
should  be  directed  towards  the  invigoration  of  the  general  powers  of  the  sys- 
tem ;  and  although,  when  disease  of  the  Chest  has  once  established  itself,  a 
warm  moist  atmosphere  may  be  necessary  as  a  preventive  of  inflammatory 
affections,  it  is  a  great  mistake  to  imagine  that  such  a  plan  is  applicable  to 
those  in  whom  there  is  merely  a  Strumous  predisposition ;  for  this  should  be 
combated  by  such  means  as  are  calculated  rather  to  brace  than  to  relax  the 
system, — especially  out-door  exercise,  a  nutritious  diet  in  which  easily-digested 
proteine-compounds  should  predominate,  and  a  dry  and  well-ventilated  habi- 
tation. There  can  be  no  doubt  that  the  Tuberculous  Cachexia  is  encouraged, 
and  developed,  by  injudicious  management  during  the  early  ages  of  life,  in 
many  cases  where  it  might  have  been  avoided.* 

879.  Equally  important  is  the  regulation  of  the  diet,  in  regard  to  its  non- 
azotized  constituents.  If  these  are  in  excess,  the  elimination  of  them  from 
the  Blood  falls  especially  upon  the  Liver  (§  836) ;  and  a  continued  excess 
gives  rise  to  disorders  in  its  function,  which  a  diminution  in  the  quantity  of 
Farinaceous  or  Oleaginous  matter  ingested  would  prevent  or  cure.  This  is 
especially  liable  to  happen  to  Europeans  proceeding  to  warm  climates  ;  who 
are  not  warned  by  their  decrease  of  appetite,  that  there  is  no  longer  a  necessity 
for  the  same  supply ;  but  force  themselves  to  eat  much  more  than  they  have 
any  real  occasion  for. — There  is  a  very  remarkable  condition  of  the  system, 
in  which  there  is  a  tendency  to  the  presence  of  a  large  amount  of  Sugar  within 
the  vessels ;  either  through  the  absence  of  power  to  convert  that  which  has 
been  taken  in  ;  or  through  the  actual  production  of  that  compound,  as  a  result 
of  the  waste  of  the  system.  We  have  seen  that  Sugar  may  be  detected  in 
the  Serum  of  healthy  blood,  drawn  soon  after  a  meal;  but  that  it  soon  becomes 
untraceable, — probably  in  consequence  of  its  being  carried  off  by  the  respi- 
ratory process  (§  697).  In  the  disease  termed  Diabetes,  or  the  "  saccharine 
diathesis,"  there  is  a  much  larger  amount  of  Sugar  in  the  Blood:  and  this 
appears  to  be  constantly  present,  as  if,  from  some  cause,  its  elimination  by 
the  usual  channel  were  retarded.  The  Sugar  makes  its  appearance,  also,  in 
the  Urine ;  the  Kidneys  taking-on  the  unusual  office  of  separating  this  com- 
pound, that  it  may  not  accumulate  in  the  Blood. — Some  late  researches  on 
the  exclusive  employment  of  azotized  principles  as  articles  of  diet,  in  the 
treatment  of  the  Saccharine  diathesis,  have  given  very  favourable  results.  The 
plan  was  long  since  proposed  by  Dr.  Rollo  ;  and  when  the  diseased  condition 
has  been  uncomplicated  by  other  maladies  (as  is  not  unfrequently  the  case), 
the  rigorous  enforcement  of  such  a  diet  has  been  attended  with  success  in 
numerous  instances.  One  of  the  greatest  difficulties  in  the  application  of  the 
system,  however,  has  arisen  from  the  longing  which  the  patients  experience 

*  See  the  excellent  works  of  Sir  James  Clark,  in  which  the  tVnportance  of  Hygienic  treat- 
ment is  strongly  insisted  on. 


GENERAL  REVIEW  OF  THE  NUTRITIVE  PROCESSES.  673 

for  Vegetable  food ;  since  this  tempts  them  to  gratify  their  appetites,  to  the 
complete  prejudice  of  the  remedial  system, — a  very  small  amount  of  farina- 
ceous matter  being  sufficient  to  cause  the  re-appearance  of  the  Sugar,  after  it 
had  seemed  to  be  entirely  got  rid  of.  It  has  been  proposed,  however,  by  M. 
Bouchardat  to  gratify  this  longing  to  a  certain  degree,  by  allowing  the  use  of 
bread  made  of  wheaten  flower,  from  which  nearly  all  the  Fecula  has  been 
separated, — the  Gluten  only  being  left,  with  such  a  small  amount  of  Fecula 
as  may  serve  to  make  it  rise  in  fermentation ;  so  that  it  is  as  free  from  un- 
azotized  constituents,  as  the  average  of  animal  substances.  This  plan  has 
been  very  successfully  practiced;  having  frequently  kept  the  disease  in  com- 
plete check,  where,  from  the  advanced  period  of  life,  the  duration  of  the 
morbid  state,  and  other  circumstances,  a  perfect  cure  could  not  be  reasonably 
expected. 

880.  From  what  has  been  stated  in  Chap,  xn*  respecting  the  nature  of  the 
Function  of  Circulation,  it  is  evident  that  primary  disorders  of  that  function 
are  not  nearly  so  frequent  as  they  are  ordinarily  supposed  to  be ;  and  that 
the  proximate  cause  of  morbid  phenomena  is  seldom  to  be  found  in  them. 
By  the  action  of  the  Heart  and  Blood-vessels,  the  nutrient  fluid,  which  has 
been  prepared  from  the  atooientary  materials  submitted  to  the  digestive  appara- 
tus, is  conveyed  to  the  tismies  which  it  is  to  nourish ;  but  the  true  process  of 
Nutrition  is  independent  of  this,  and  may  take  place  after  the  motion  of  the 
fluid  has  ceased,  just  as  it  commences  before  any  movement  shows  itself. 
For  the  tissue  which  exists  in  the  Embryo  during  the  early  period  of  its  de- 
velopment, and  also  in  any  newly-forming  part,  is  destitute  of  vessels,  consist- 
ing only  of  cells  ;  and  these  grow  and  reproduce  themselves  at  the  expense 
of  the  nutritive  materials  supplied  to  them  from  without,  just  as  does  the 
whole  mass  of  a  Cellular  Plant.  Moreover  it  has  been  shown  (§  740),  that 
the  activity  of  the  nutrient  processes  has  much  to  do  with  the  movement  of 
the  fluid  through  the  smaller  vessels,  and  is  a  cause  rather  than  a  consequence 
of  it.  If  the  action  of  the  Heart  cease,  the  whole  circulation  must  obviously 
come  to  a  stand  ere  long;  but  in  many  animals  the  Capillary  movement  may 
continue  for  some  time  after  the  general  circulation  has  been  checked;  and, 
so  long  as  blood  is  supplied  to  the  parts,  so  long  may  their  nutrition  continue, 
provided  other  circumstances  be  favourable.  It  is  unquestionably  true,  that 
the  cessation  of  the  Circulation  is  usually  the  immediate  cause  of  Death  ;  and 
that,  when  the  suspension  is  permanent,  the  loss  of  the  vitality  of  the  system, 
considered  both  as  a  whole,  and  as  made  up  of  distinct  parts,  is  a  necessary 
consequence.  But  still,  we  find  that  the  cause  of  this  cessation  seldom  origi- 
nates in  the  Circulating  apparatus  itself;  and  in  general,  a  disturbed  state  of 
the  Circulation  is  to  be  looked  upon  rather  as  a  result,  than  as  a  cause,  of 
diseased  action.  An  extreme  case  of  such  a  disturbance,  which,  when  suffi- 
ciently prolonged,  is  attended  with  fatal  results,  is  to  be  found  in  Asphyxia  ; 
in  which  the  cessation  of  the  action  of  the  Lungs  induces  a  stagnation  of  the 
Blood  in  their  capillaries ;  and  as,  in  warm-blooded  animals,  the  whole  cur- 
rent of  Blood  has  to  pass  through  the  Lungs,  before  proceeding  again  to  the 
system,  a  total  suspension  of  the  Circulation  necessarily  results  from  this  inter- 
ruption (§§  738  and  779).  Now  if  we  take  this  (which  it  appears  reasonable 
to  do)  as  a  type  of  a  great  number  of  morbid  conditions  of  different  organs, 
we  are  led  to  see  why  a  serious  disturbance  of  the  movement  in  any  one  part 
should  affect  the  entire  circulating  apparatus,  and  should  thus  influence  its 
flow  through  almost  every  other  organ.  There  are  no  other  organs,  however, 
in  which  a  stagnation  can  be  so  serious  as  in  the  Lungs ;  since  there  are  none 
through  which  the  whole  current  flows.  The  Liver  ranks  next  in  importance, 
since  all  the  venous  blood  collected  from  the  Chylopoietic  viscera  passes 
through  it ;  and  every  practical  man  is  aware  how  frequently  derangement  of 
57 


674  GENERAL  REVIEW  OF  THE  NUTRITIVE  PROCESSES. 

the  circulation  through  the  Liver,  originating  in  an  unhealthy  state  of  the  gland 
itself,  is  a  cause  of  serious  disorders  in  the  abdominal  viscera. — Minor  irregu- 
larities in  the  Circulation,  in  various  parts,  not  unfrequently  become  causes  of 
serious  inconvenience.  Thus,  few  conditions  are  more  common,  especially 
amongst  persons  of  active  minds  but  inert  habits,  than  undue  determination  of 
blood  to  the  Head,  conjoined  with  torpor  of  the  circulation  through  the  Skin, 
especially  that  of  the  extremities,  which  are  ordinarily  cold.  The  obvious 
indication  here  is,  to  endeavour  to  restore  the  balance  of  the  Circulation  ;  and 
excitement  of  the  flow  of  blood  through  the  Skin,  by  frictions,  moderately- 
stimulating  applications,  exercise,  &c.,  will  commonly  prove  of  great  utility. 

881.  There  are  many  disorders   commonly  regarded   as  affections  of  the 
Circulation,  which   evidently  consist  in  reality  of  a  morbid  alteration  in  the 
Nutritive,  processes  :  among  these  there  can  be  little  doubt  that  wre  are  to  rank 
local  Determinations  and  Congestions,  which  result  from  an  exalted  or  dimi- 
nished activity  of  the  formative  actions ;  and  Inflammation,  in  which  these 
actions  are  perverted.     Much  has  been  said  and  written,  to  very  little  purpose, 
respecting  the  essential  nature  of  this  process ;  it  has  been  attributed  by  some 
to  disordered  action  of  the  vessels,  and  by  others  to  an  injurious  impression 
on  the  nerves, — the  fact,  that  Inflammation  may  occur  in  tissues  which  con- 
tain neither  vessels  nor  nerves,  having  been  entirety  overlooked.     The  only 
view  of  the  character  of  Inflammation  that  seems  likely  to  account  for  its 
phenomena,  is  that  which  regards  it  as  essentially  consisting  in  a  disturbance 
of  the  due  relation  between  the  living  Tissue   and  the  nutrient  materials 
contained  in  the  Blood  ;  in  other  words,  as  an  abnormal  form  of  the  ordinary 
nutritive  process  (§§  802 — 806).     A  similar  remark  may  be  made,  in  regard 
to  those   productions    formerly  termed   "  Heterologous    transformations"  of 
tissue ;  which  are  rather  to  be  regarded  as  new  growths,  that  have  appro- 
priated the  nutriment  designed  for  the  support  of  the  proper  tissues,  and  have 
therefore  become  developed  at  the  expense  of  these.     It  is  quite  as  absurd 
to  attempt  to   account  for  the  growth  of  Scirrhus,  Carcinoma,  &c.,  by  any 
peculiar  action  of  the  vessels  of  the  part,  as  it  would  be  to  attribute  the  secre- 
tion of  fatty  matter  by  the   cells   of  one  tissue,  or  of  phosphate  of  lime  by 
those  of  another,  to  the  peculiar  distribution  of  their  vessels.     The  progress 
of  research  obviously  leads  to  the  conclusion,  that  in  every  part  of  the  living 
body  there  is  an  inherent  and  independent  vitality,  which  enables  it  to  grow 
and  maintain  its  normal  structure  and  constitution,  so  long  as  it  is  supplied 
with  the  requisite  materials ;  and  that  changes  in  the  character  of  the  tissue 
can  be  referred  to  nothing  else  than  to  alterations  in  its  properties,  resulting 
from   external   agencies,  or  to   alterations  in   the    materials  supplied    for  its 
renewal.     Of  these  two  morbific  causes,  the  latter  is  undoubtedly  the  most 
frequent ;  and  the  tendency  which  is  now  gaining  ground,  to  seek  in  the  Blood 
for  indications  of  pathological  changes,  when  there  is  no  obvious  general  dis- 
turbance of  the  system,  will  probably  lead  to  a  greatly-increased  knowledge 
of  the  real  nature  of  diseased  states ;  in  spite  of  the  opposition  which  any 
return  to  the  Humoral  Pathology  is  sure  to  excite,  in  the  minds  of  those  who 
regard  it  as  an  exploded  and  pernicious  system. 

882.  The  Sympathy  between  different  parts  of  the  system,  which  espe- 
cially manifests  itself  in  the  tendency  to  simultaneous  affection  with  the  same 
Disease,  affords  an  excellent  illustration  of  this  principle.     Of  those  Sympa- 
thetic actions,  which  result  from  the   Nervous   connections   of  the  various 
organs,  this  is   not  the  place  to  speak ;   since  we  are   at  present  concerned 
with  those  perversions  of  the  Nutritive  processes,  which  give  rise  to  Inflam- 
matory and  other  diseases.     Where  a  certain  tissue,  throughout  the  body,  is 
similarly  affected,  there  is  strong  reason  to  presume  that  the  morbific  cause 
is  conveyed  to  it  in  the  Blood ;  this  is  the  case,  for  example,  with  regard  to 


GENERAL  REVIEW  OF  THE  NUTRITIVE  PROCESSES.  675 

the  Mucous  membranes,  which  all  manifest  a  tendency  to  Inflammation,  when 
Arsenic  has  been  received  into  the  system :  and  certain  forms  of  the  disease 
commonly  termed  Influenza,  are  marked  by  a  similar  disposition.  The  same 
may  be  said  in  regard  to  Inflammation  of  the  Fibrous  membranes,  Areolar 
tissue,  Serous  membranes,  and  other  structures.  It  has  been  considered  a 
sufficient  account  of  these  consentaneous  affections,  to  say  that  they  result 
from  Sympathy, — a  mere  verbal  quibble,  which  explains  nothing.  If,  on  the 
other  hand,  we  regard  the  disease  as  a  perversion  of  the  ordinary  processes 
of  Nutrition,  Secretion,  &c.,  and  as  dependent  upon  an  abnormal  condition  of 
the  Blood  (such  as  is  induced  by  the  introduction  of  a  poison  into  it),  the 
rationale  of  the  sympathetic  disturbance  becomes  apparent; — since  all  the 
tissues  of  the  same  kind  will  of  necessity  be  similarly  affected,  although  some 
local  cause  may  occasion  one  to  suffer  more  severely  than  another.  In  the 
ingenious  paper  by  Dr.  W.  Budd,  already  referred  to  (§  785),  the  perfect  cor- 
respondence, which  not  unfrequently  manifests  itself  between  the  diseased 
actions  on  the  two  sides  of  the  body,  is  Adduced  in  support  of  the  same  view, 
to  which  it  is  made  to  afford  very  striking  confirmation.  The  fact  that  this 
kind  of  Sympathy  not  unfrequently  manifests  itself  between  tissues  having 
an  analogous  structure,  but  very  different  function,  is  another  argument  in 
favour  of  the  same  view  ;  of  this  fact,  the  sympathy  of  which  every  practical 
man  is  aware,  between  the  Skin  and  Mucous  Membranes,  is  a  very  good 
example.  The  sympathy  of  the  different  tissues  forming  any  individual  organ, 
by  which  disease  in  one  becomes  a  cause  of  disorder  in  the  rest,  is,  however, 
to  be  very  differently  explained.  We  have  examples  of  this  in  Inflammatory 
affections  of  the  Mucous  membranes,  which  usually  extend  themselves  to  the 
remaining  constituents  of  the  organs  of  which  they  form  a  part;  and  in  those 
of  the  Serous  membranes,  which  almost  always  follow  inflammation  of  the 
organs  they  invest.  Here  the  local  disturbance  of  one  part  appears  sufficient 
to  account  for  the  extension  of  it  to  another,  that  is  closely  connected  with  it 
by  vessels  and  nerves;  this  has  been  termed  the  Sympathy  of  Contiguity. 
The  Fibrous  membranes  are  less  liable  to  be  affected  in  this  manner,  than  are 
most  other  tissues  ;  and  the  reason  appears  simply  this, — that  there  is  usually 
less  vascular  connection  between  them  and  the  adjacent  parts,  than  there  is 
in  the  case  of  the  Serous  membranes.  Hence  the  Fibrous  membranes  fre- 
quently act  as  insulators,  preventing  the  spread  of  disease  to  adjacent  parts. 
883.  The  general  characters  of  the  processes  of  Nutrition  and  Secretion 
are  so  nearly  allied,  that  what  has  been  stated  of  the  Pathological  states  of  the 
former,  is  nearly  as  applicable  to  those  of  the  latter.  Although  it  is  unques- 
tionable that  disordered  Secretion  may  result  from  a  purely  local  cause,  acting 
on  the  solid  tissue  of  the  part  affected,  yet  there  is  also  increasing  reason  to 
believe,  that  in  a  large  number  of  cases,  the  abnormal  character  of  the  pro- 
duct is  in  reality  a  result  of  the  abnormal  state  of  the  Blood  from  which  it 
is  separated ;  and  that  the  organ  itself  is  still  performing  a  healthy  function, 
in  separating  from  the  blood  that  which  would  be  injurious  to  it.  This 
leads  us  to  refer  such  disorders  to  causes  much  more  remote  than  those 
which  were  formerly  supposed  to  operate  ;  but  they  are  undoubtedly  nearer 
the  true  ones.  Such  a  view  has  been  prosecuted  by  Dr.  Prout  in  regard  to 
the  abnormal  conditions  of  the  Urine,  with  great  success ;  and  there  can  be 
little  doubt  that  it  is  also  applicable  to  the  Biliary  secretion,  on  the  true 
chemical  nature  of  which  there  is  scarcely  yet  an  agreement  among  Chemists, 
and  whose  pathological  conditions,  therefore,  are,  and  must  long  remain, 
comparatively  obscure.  It  is  obvious  that,  if  the  Assimilation  of  Nutritive 
matter  be  in  any  respect  wrongly  performed,  the  products  of  the  Decomposi- 
tion of  the  Tissues  (in  which  these  excretions  probably  originate,  §  819),  must 
also  be  different;  and  our  remedial  measures  must  often  be  directed,  therefore, 
not  so  much  to  the  Secreting  organ,  as  towards  the  previous  operations. 


676  GENERAL  REVIEW  OF  THE  NUTRITIVE  PROCESSES. 

884.  These  considerations  are  of  the  highest  importance  in  the  treatment 
of  Disease ;  the  success  of  which  will  greatly  depend  upon  the  degree  in 
which  the  Physician  follows  the  indications  of  Nature,  instead  of  putting  him- 
self in  antagonism  to  her  course  of  operation.  If  we  pay  but  a  slight  attention 
to  those  ^phenomena  which  result  from  the  introduction  of  poisons  into  the 
system,  we  perceive  that  there  is  almost  invariably  an  increased  excretion  of 
some  kind,  which  tends  to  eliminate  them  from  the  blood.  Even  where  there 
is  no  other  obvious  means  for  their  removal,  we  can  have  little  doubt  that  the 
Respiratory  function  gives  important  aid  in  their  separation  ;  when  we  keep 
in  view  that  from  five  to  eight  ounces  of  solid  carbon,  to  say  nothing  of  the 
hydrogen,  are  thrown  off  from  the  lungs  in  the  course  of  every  twenty-four 
hours.  It  is  important  to  bear  this  circumstance  in  mind  ;  since  it  enables  us 
to  understand  how,  if  time  be  given,  the  system  frees  itself  from  such  noxious 
substances;  and  it  points  out  the  duty  of  the  medical  attendant  to  be  rather 
that  of  supporting  the  powers  of  the  body  by  judiciously-devised  means,  and 
of  aiding  in  the  elimination  of  the  noxious  matter  by  a  copious  supply  of  pure 
air,  than  of  interfering  more  actively  to  promote  that  which  Nature  is  already 
effecting  in  the  most  advantageous  manner.  We  see  the  results  of  this  ope- 
ration in  the  case  of  Narcotic  poisoning ;  in  which,  if  the  Respiratory  process 
can  be  artificially  kept  up  for  a  sufficient  length  of  time,  the  powers  of  the 
nervous  system  are  gradually  restored,  even  after  what  seemed  to  be  their 
complete  and  final  cessation. — There  can  be  no  doubt  that,  in  like  manner, 
the  system  makes  an  effort  to  rid  itself  of  other  noxious  substances,  the  pre- 
sence of  which  in  the  blood  results  from  morbid  processes  going  on  in  the 
body  itself,  and  which,  if  retained,  would  produce  the  most  serious  conse- 
quences. Thus  a  copious  discharge  of  Lithic  acid  by  the  Urine  will  frequently 
avert  or  curtail  an  attack  of  Gout.  The  copious  acid  perspirations,  which 
occur  in  certain  forms  of  Rheumatism,  are  the  means  by  which  the  Lactic  acid 
(which  seems  to  be  the  materies  morbi  of  this  disease)  is  separated  from  the 
blood.  And  there  can  be  no  doubt  that  an  attack  of  Diarrhoea  often  prevents 
more  serious  disease,  by  removing  an  unusual  accumulation  of  the  elements 
of  bile,  or  by  eliminating  an  undue  amount  of  putrescent  matter,  the  continued 
presence  of  which  in  the  circulating  fluid  would  induce  the  most  serious  dis- 
orders in  the  nervous  system. — There  can  be  no  doubt  that  a  due  regulation 
of  the  Excreting  processes  is  one  of  the  most  important  means,  by  which  the 
Physician  can  counteract  the  results  of  disordered  actions  in  the  system.  They 
may  frequently  require  to  be  gently  stimulated,  in  order  to  remove  some  mor- 
bific elements  from  the  blood.  But  it  will  be  seldom  that  it  will  be  desirable 
to  check  them,  even  when  apparently  excessive,  unless  there  be  strong  reason 
to  believe,  that  the  excess  proceeds  from  a  disordered  state  of  the  organ  itself, 
produced  by  local  causes  only. 


2. — Minimal  Heat. 

885.  All  the  vital  actions  that  have  been  considered  in  the  preceding  pages, 
require  a  certain  amount  of  Heat  as  a  condition  of  their  performance ;  and  in 
the  more  elevated  tribes  of  animals,  in  which  (for  the  very  purposes  of  their 
creation)  a  high  degree  of  constancy  and  regularity  is  required  in  these  actions, 
there  is  a  provision  within  themselves  for  the  maintenance  of  their  temperature 
at  a  certain  standard.     We  shall  inquire,  in  the  first  place,  into  the  amount  of 
Heat  thus  generated  by  Man ;  and  then  into  the  sources  of  its  production. 

886.  Our  present  knowledge  of  the  Temperature  of  the  Human  body  under 
different  circumstances,  is  chiefly  due  to  the  investigations  of  Dr.  J.  Davy. 
Much  additional  information  may  be  expected,  however,  from  inquiries  which 


ANIMAL  HEAT.  677 

are  at  present  in  progress.  Dr.  Davy's  observations*  have  included  114  in- 
dividuals of  both  sexes,  of  different  ages,  and  among  various  races,  in  different 
latitudes,  and  under  various  temperatures;  the  external  temperature,  however, 
was  in  no  instance  very  low,  and  the  variations  were  by  no  means  extreme. 
The  mean  of  the  ages  of  all  the  individuals  was  27  years.  The  following  is 
a  general  statement  of  the  results,  the  temperature  of  the  body  being  ascer- 
tained by  a  thermometer  placed  under  the  tongue. 

Temperature  of  the  air  60°  Average  temperature  of  the  body  91-28° 

69°  "  »  98-15° 

78°  »  "  »  »  98-85° 

79.50  „  „  „  „  99.21o 

80°  "             »  99-67° 

82°  "             "             "             "  99-9° 

Mean  of  all  the  experiments     74°  Mean  of  all  the  experiments  100° 

Highest  temperature  of  air        82°  Highest  temperature  of  body  102° 

Lowest  temperature  of  air        60°  Lowest  temperature  of  body  96-5° 

From  this  we  see  that  the  variations  noted  by  Dr.  Davy,  which  were  evidently 
in  part  the  consequence  of  variations  in  external  temperature,  but  which  were 
also  partly  attributable  to  individual  peculiarities,  amounted  to  5|  degrees  ;  the 
lower  extreme  would  probably  undergo  still  further  depression,  if  the  inquiries 
were  carried  on  in  very  cold  climates. — The  Temperature  of  the  body  may 
be  affected  by  internal  as  well  as  by  external  causes ;  thus  in  diseases  which 
involve  an  accelerated  pulse  and  an  augmented  respiration,  the  temperature  is 
generally  higher  than  usual,  even  though  a  large  portion  of  the  lung  may  be 
unfit  for  its  function.  This  is  often  remarkably  seen  in  the  last  stages  of 
Phthisis,  when  the  inspirations  are  extremely  rapid,  and  the  pulse  so  quick  as 
scarcely  to  admit  of  being  counted ;  the  skin,  in  such  cases,  often  becomes 
alm,ost  painfully  hot.  On  the  other  hand,  in  diseases  of  the  contrary  character, 
such  as  Asthma  and  the  Asiatic  Cholera,  the  temperature  of  the  body  falls, 
sometimes,  to  the  extent  of  20  degrees.  The  following  observations  have  been 
made  on  this  subject  by  M.  Donne  ;t  it  is  much  to  be  desired,  however,  that 
fuller  data  could  be  collected  on  the  subject.  In  a  case  of  Puerperal  Fever, 
the  pulse  being  168,  and  the  respiration  48  per  minute,  the  temperature  was 
104°.  In  a  case  of  Hypertrophy  of  the  Heart,  the  pulse  being  150  and  the 
respirations  34,  the  temperature  was  103°<  In  a  case  of  Typhoid  Fever,  the 
pulse  being  136,  and  the  respirations  50,  the  temperature  was  104°.  And  in 
a  case  of  Phthisis,  the  pulse  being  140,  and  the  respirations  62,  the  tempera- 
ture was  102°.  On  the  other  hand,  in  a  case  of  Jaundice,  in  which  the  pulse 
was  but  52,  the  temperature  was  only  96*40° ;  but  the  same  temperature  was 
observed  in  a  case  of  Diabetes,  in  which  the  pulse  was  84.  The  limited  re- 
sults of  Mons.  D.'s  experiments,  whilst  they  clearly  indicate  that  a  general 
relation  exists  between  the  temperature  of  the  body  and  the  rapidity  of  the 
pulse,  also  show  that  this  relation  is  by  no  means  invariable,  but  that  it  is 
liable  to  be  affected  by  several  causes,  of  which  our  knowledge  is  as  yet  very 
limited.  Dr.  Dunglison  speaks  of  having  frequently  seen  the  thermometer  at 
106°  in  Scarlatina  and  Typhus  ;  and  Dr.  Edwards  mentions  a  case  of  Tetanus, 
in  which  it  rose  to  11014 

*  Phil.  Trans.,  1814;  republished  in  Anatomical  and  Physiological  Researches. 

f  Archives  Generates,  Oct.  1835  ;  and  Brit,  and  For.  Med.  Rev.,  vol.  ii.  p.  248. 

J  [An  extensive  series  of  observations  has  been  made  by  M.  Roger*  on  the  temperature 
of  children  in  health  and  various  diseases. 

In  nine  examinations  of  infants  from  one  to  twenty  minutes  after  birth,  the  temperature' 
(observed  in  these  and  in  all  the  other  cases,  in  the  axilla),  was  from  99'95  to  95-45.  Im- 


Arch.  Gen.  de  Medecine,  Juillet,  Aout,  &c.,  1344. 

57* 


678  GENERAL  REVIEW  OF  THE  NUTRITIVE  PROCESSES. 

887.  Although  there  appears  to  be,  for  all  species  of  animals,  a  distinct 
limit  to  the  variations  of  bodily  temperature,  under  which  their  vital  opera- 
tions can  be  carried  on,  this  limitation  does  not  prevent  animals  from  existing 
in  the  midst  of  great  diversities  of  external  conditions  ;  since  they  have  within 
themselves  the  power  of  compensating  for  these,  in  a  very  extraordinary  de- 
gree.    This  power  seems  to  exist  in  Man  to  a  higher  amount  than  in  most 
other  animals;  since  he  can  not  only  support,  but  enjoy,  life  under  extremes, 
either  of  which  would  be  fatal  to  many.     In  many  parts  of  the  tropical  zone, 
the  thermometer  rises  every  day  through  a  large  portion  of  the  year  to  110°; 
and  in  British  India  it  is  said  to  be  seen  occasionally  at  130°.     On  the  other 
hand,  the  degree  of  cold  frequently  sustained  by  Arctic  voyagers,  and  quite 
endurable  under  proper  precautions,  appears   much  more   astonishing ;  by 
Capt.  Parry,  the  thermometer  has  been  seen  as  low  as  — 55°,  or  87°  below 
the  freezing  point;  by  Capt.  Franklin  at — 58°,  or  90°  below  the  freezing 
point ;  and  by  Capt.  Back  at  — 70°,  or  102°  below  the  freezing  point.    In  both 
cases,  the  effect  of  the  atmospheric  temperature  on  the  body  is  greatly  influ- 
enced by  the  condition  of  the  air  as  to  motion  or  rest;  thus,  every  one  has 
heard  of  the  almost  unbearable  oppressiveness  of  the  sirocco  or  hot  wind  of 
Sicily  and  Italy,  the  actual  temperature  of  which  is  not  higher  than  has  often 
been  experienced  without  any  great  discomfort,  when  the  air  is  calm  :  and,  on 
the  other  side,  it  may  be  mentioned  that,  in  the  experience  of  many  Arctic  voya- 
gers, a  temperature  of — 50°  may  be  sustained,  when  the  air  is  perfectly  still, 
with  less  inconvenience  than  is  caused  by  air  in  motion  at  a  temperature  fifty 
degrees  higher.     This  is  quite  conformable  to  what  might  be  anticipated  on 
physical  principles. 

888.  Again,  the  degree  of  moisture  contained  in  a  heated  atmosphere,  makes 
a  great  difference  in  the  degree  of  elevation  of  temperature,  which  may  be  sus- 

mediately  after  birth  the  temperature  was  at  the  highest;  but  it  quickly  fell  to  near  the 
lowest  of  those  above  stated ;  but,  by  the  next  day,  it  was  again  completely  or  nearly  what 
it  was  before.  The  rapidity  of  the  pulse  and  of  respiration  appeared  to  have  no  certain  re- 
lation to  the  temperature. 

In  thirty-three  infants  of  from  one  to  seven  days  old,  the  most  frequent  temperature  was 
98-6;  the  average  was  98-75;  the  maximum  (in  one  case  only)  102-2;  the  minimum  (also 
observed  only  once)  96°- 8.  All  the  infants  were  healthy.  The  frequency  of  respiration 
had  no  evident  or  constant  relation  to  tlie  temperature.  A  few  of  the  infants  were  of  a 
weakly  habit;  their  average  was  97-7:  the  others  were  strong,  and  their  average  tempera- 
ture was  99°-534.  The  age  of  the  infant  (in  this  short  period)  had  no  influence  on  its 
temperature ;  neither  had  its  sex,  nor  its  state  of  sleep  or  waking,  nor  the  period  after 
suckling. 

In  twenty-four  children,  chiefly  boys,  from  four  months  to  fourteen  years  old,  the  most  fre- 
quent temperature  was  above  980>6 ;  the  average  was  980>978,  the  minimum  was  980>15; 
the  maximum  99°-95.  The  average  temperature  of  those  six  years  old  or  under,  was 
98°-798;  of  those  above  six  years  old,  99°-158.  The  average  number  of  pulsations  in  the 
minute  was  in  those  under  six  years  old  102 ;  in  those  above  that  age  77 ;  yet  the  tempera- 
ture of  the  latter  was  higher  than  that  of  the  former,  or  of  younger  infants.  There  was  no 
evident  relation  between  the  temperature  and  the  frequency  of  respiration ;  nor  in  a  few 
examinations,  was  the  temperature  affected  in  a  regular  way,  by  active  exercise  for  a  short 
time,  or  by  the  stage  of  digestion. 

As  already  said,  in  all  the  examinations  from  which  these  results  were  obtained,  the 
thermometer  was  held  in  the  axilla;  comparative  examinations  proved  that  the  tempera- 
ture of  the  axilla  (though  lower  than  that  of  internal  organs),  was  higher  than  that  of  any 
other  part  of  the  surface  of  the  skin.  Of  the  other  parts  examined,  the  warmest  was  the 
abdomen,  then  in  succession,  the  cavity  of  the  mouth,  the  bend  of  the  arm,  the  hands,  the 
feet ;  of  which  last,  the  average  temperature,  in  four  examinations,  was  only  87°-35.  (These 
results  correspond  sufficiently  with  those  obtained  by  Dr.  John  Davy.) 

In  diseased  states,  (to  the  illustration  of  which  the  greater  part  of  the  memoir  is  devoted,) 
the  temperature  of  the  skin  in  children  may  descend  to  74°-3,  and  may  ascend  to  108°-5. 
Its  range  of  variation  is  therefore  much  greater  than  in  adults,  in  whom  M.  Andral  found  it 
to  vary  in  different  diseases  not  more  than  from  95°  to  107°-6. — M.  C.] 


ANIMAL  HEAT.  679 

tained  without  inconvenience.  Many  instances  are  on  record,  of  a  heat  of 
from  250°  to  280°  being  endured  in  dry  air  for  a  considerable  length  of  time, 
even  by  persons  unaccustomed  to  a  particularly  high  temperature  ;  and  per- 
sons whose  occupations  are  such  as  to  require  it,  can  sustain  a  much  higher 
degree  of  heat,  though  not  perhaps  for  any  long  period.  The  workmen  of 
the  late  Sir  F.  Chantrey  have  been  accustomed  to  enter  a  furnace  in  which 
his  moulds  were  dried,  whilst  the  floor  was  red-hot,  and  a  thermometer  in  the 
air  stood  at  350° ;  and  Chabert,  the  "  Fire-king,"  was  in  the  habit  of  entering 
an  oven,  whose  temperature  was  from  400°  to  600°.  It  is  possible  that  these 
feats  might  be  easily  matched  by  many  workmen  who  are  habitually  exposed 
to  high  temperatures;  such  as  those  employed  in  Iron -foundries,  Glass- 
houses, and  Gas-works.  In  all  these  instances,  the  dryness  of  the  air  facili- 
tates the  rapidity  of  the  vaporization  of  the  fluid,  of  which  the  heat  occasions 
the  secretion  by  the  Cutaneous  glands;  and  the  large  amount  of  caloric  which 
becomes  latent  in  the  process,  is  for  the  most  part  withdrawn  from  the  body, 
the  temperature  of  which  is  thus  kept  down.  Exposure  to  a  very  elevated 
temperature,  however,  if  continued  for  a  sufficient  length  of  time,  does  pro- 
duce a  certain  elevation  of  that  of  the  body ;  as  might  be  expected  from  the 
statements  already  made  in  regard  to  the  variation  in  the  heat  of  the  body 
with  changes  in  atmospheric  temperature  (§  886).  In  the  experiments  of 
MM.  Berger  and  Delaroche,  it  was  found  that,  after  the  body  had  been  ex- 
posed to  air  of  120°  during  17  minutes,  a  thermometer  placed  in  the  mouth 
rose  nearly  6  degrees  above  the  ordinary  temperature;  it  may  be  remarked, 
however,  that  as  the  body  was  immersed  in  a  close  box,  from  which  the  head 
projected  (in  order  to  avoid  the  direct  influence  of  the  heated  air  on  the  tem- 
perature of  the  mouth),  the  air  had  probably  become  charged  with  the  vapour 
exhaled  from  the  surface,  and  had  therefore  somewhat  of  the  effects  of  a  moist 
atmosphere.  At  any  rate,  the  temperature  of  the  body  does  not  appear  to 
rise,  under  any  circumstances,  to  a  degree  very  much  greater  than  this.  In 
one  of  the  experiments  of  Drs.  Fordyce  and  Blagden,  the  temperature  of  a 
Dog,  that  had  been  shut  up  for  half-an-hour  in  a  chamber  of  which  the  tem- 
perature was  between  220°  and  236°,  was  found  to  have  risen  from  101°  to 
about  108°.  MM.  Delaroche  and  Berger  tried  several  experiments  on  differ- 
ent species  of  animals,  in  order  to  ascertain  the  highest  temperature  to  which 
the  body  could  be  raised  without  the  destruction  of  life,  by  inclosing  them  in 
air  heated  from  122°  to  201°,  until  they  died:  the  result  was  very  uniform, 
the  temperature  of  the  body  at  the  end  of  the  experiment  only  varying 
in  the  different  species  between  11°  and  13°  above  their  natural  standard: 
whence  it  may  be  inferred,  that  an  elevation  to  this  degree  must  be  fatal. 
This  elevation  would  be  attained  comparatively  soon  in  a  moist  atmo- 
sphere ;  partly  because  of  the  greater  conducting  power  of  the  medium ; 
but  principally  on  account  of  the  check  which  is  put  upon  the  vapor- 
ization of  the  fluid  secreted  by  the  skin.  Even  here,  however,  custom 
and  acquired  constitution  have  a  very  striking  influence ;  for  whilst  the  in- 
habitants of  this  country  are  unable  to  sustain,  during  more  than  10  or  12 
minutes,  immersion  in  a  vapour-bath  of  the  temperature  of  110°  or  120°,  the 
Finnish  peasantry  remain  for  half-an-hour  or  more  in  a  vapour-bath,  the  tem- 
perature of  which  finally  rises  even  to  158°  or  167°. — Accurate  experiments 
are  yet  wanting,  to  determine  the  influence  of  humidity  on  the  effects  of  cold 
air.  From  experiments  on  young  Birds  incapable  of  maintaining  their  own 
temperature,  of  which  some  were  placed  in  cold  dry  air,  and  others  in  cold  air 
charged  with  moisture,  it  was  found  by  Dr.  Edwards  that  the  loss  of  heat  was 
in  both  instances  the  same;  the  effect  of  the  evaporation  from  the  surface  in 
the  former  case,  being  counter-balanced  in  the  latter  by  the  depressing  influ- 
ence of  the  cold  moisture.  This  influence,  the  existence  of  which  is  a  mat- 


680  GENERAL  REVIEW  OF  THE  NUTRITIVE  PROCESSES. 

ter  of  ordinary  experience,  is  probably  exerted  directly  upon  the  nervous 
system. 

889.  Having  thus  considered  the  general  facts  which  indicate  the  faculty 
possessed  by  the  living  system,  in  the  higher  Animals,  of  keeping  up  its  tem- 
perature to  an  elevated  standard,  and  of  preventing  it  from  being  raised  much 
beyond  it  by  any  degree  of  external  heat,  we  have  next  to  inquire  to  what 
this  faculty  is  due.  We  shall  be  more  likely  to  arrive  at  accurate  results  in 
such  an  inquiry,  the  more  comprehensive  is  our  survey  of  the  phenomena  to 
which  it  relates.* 

a.  The  most  recent  experiments  on  the  temperature  of  Plants  (those  made  by  MM.  Bec- 
querel  and  Breschet  with  the  thermo-multiplier)  have  demonstrated,  that  in  those  parts  in 
which  the  vital  processes  are  taking  place  with  activity,  a  sensible  amount  of  caloric  is  being 
constantly  evolved.     The  amount  of  this  evolution  of  heat  is  generally  very  low,  not  more, 
in  fact,  than  a  single  degree  (Fahr.) ;  and  as  it  does  not  more  than  counterbalance  the  effect 
of  the  evaporation,  which  is  continually  taking  place  from  the  surface,  there  is  no  sensible 
difference  between  the  temperature  of  the  plant  and  that  of  the  surrounding  air.     At  the 
time  of  Flowering,  however,  a  much  greater  degree  of  heat  is  generated  in  many  plants, 
especially  in  those  in  which  a  large  number  of  flowers  are  crowded  together,  as  in  the  case 
of  the  Arum  tribe:  thus  a  thermometer  placed  in  the  midst  of  twelve  spadixes  has  been 
seen  to  rise  to  121°,  whilst  the  temperature  of  the  air  was  only  66°.     During  the  Germina- 
tion of  seeds,  again,  a  considerable  development  of  heat  takes  place;  this,  which  is  soon 
carried  off  from  a  single  seed,  becomes  very  sensible  when  a  large  number  are  heaped  toge- 
ther, as  in  malting ;  the  thermometer  plunged  into  a  heap  of  germinating  barley  having  been 
seen  to  rise  to  110°. 

b.  These  facts  are  of  more  importance  than  might  appear  at  first  sight ;  for  they  indicate 
unequivocally,  that  the  source  of  the  heat  is  to  be  looked  for  in  the  Organic  functions,  not  in 
those  of  Animal  life.     The  evolution  of  Caloric  has  been  attributed  by  many  physiologists 
to  the  Nervous  system  ;  the  influence  which  this  system  evidently  possesses  over  the  func- 
tion, being  mistaken  for  the  efficient  cause  of  it.     As  has  been  remarked  on  several  former 
occasions,  however, — the  fact  that  any  change  takes  place  in  Vegetables,  to  the  same  degree 
(under  certain  conditions,)  with  that  in  which  it  ever  presents  itself  in  Animals,  is  a  suffi- 
cient proof  that  it  cannot  be  dependent  upon  nervous  agency,  although  it  may  be  influenced  by 
it.     Moreover,  it  may  be  remarked  that  the  production  of  Heat  is  an  operation  of  an  entirely 
physical  character,  and  that  it  may  be  referred  to  physical  causes ;  whilst  the  operations  in 
which  the  Nervous  system  is  concerned,  are  such  as  we  cannot  liken  in  any  degree  to  physical 
phenomena,  and  are  of  a  purely  vital  character.— In  our  inquiry  into  the  sources  of  the  Heat 
evolved  by  living  beings,  we  are  limited,  therefore,  to  those  which  can  operate  in  the  Vege- 
table kingdom ;  and  on  examining  into  the  phenomena  which  present  any  relation  to  this, 
we  are  at  once  struck  with  the  fact,  that  an  absorption  of  Oxygen  from  the  air,  with  an  ex- 
trication of  Carbonic  acid,  is  continually  taking  place  (constituting  the  true  Respiratory  pro- 
cess of  Plants,  §  750);  and  that  these  changes  occur  with  excessive  activity,  at  the  very 
periods  at  which  the  evolution  of  Heat  is  tnost  remarkable, — those,  namely,  of  germination 
and  flowering.     The  quantity  of  Oxygen  consumed  by  flowers  is  enormous — those  of  the 
Arum  Italicum  having  been  found  to  convert  40  times  their  own  bulk  of  that  gas  into  Carbonic 
acid,  between  the  periods  of  their  first  appearance  and  their  final  decay ;  and  of  this,  the  far 
larger  proportion  is  consumed  by  the  sexual  apparatus,  which  has  been  found  to  consume  132 
times  its  own  bulk  of  Oxygen  in  24  hours.   That  this  change  is  a  condition  necessary  for  the 
production  of  Heat,  is  fully  proved  by  the  fact,  that  no  caloric  is  evolved  when  the  flowers 
are  excluded  from  the  contact  of  Oxygen ;  whilst  the  substitution  of  pure  oxygen  for  atmo- 
spheric air  occasions  the  elevation  of  temperature  to  be  more  rapid  and  considerable  than 
usual-t     The  same  may  be  said  of  the  heat  liberated  by  seeds  in  the  act  of  Germination :  a 
large  amount  of  oxygen  is  absorbed,  and  of  carbonic  acid  given  out,  during  this  process ;  and 
the  evolution  of  Heat  may  be  easily  shown  to  be  as  dependent  upon  this  change,  as  in  the 
instance  just  quoted. 

c.  When  the  phenomena  of  Calorification  in  Animals  are  carefully  examined,  they  are 
found  to  harmonize  completely  with  this  view.     Throughout  the  whole  kingdom,  an  exact 
conformity  may  be  perceived  between  the  amount  of  Oxygen  consumed  and  of  Carbonic 
acid  given  off,  and  the  degree  of  Heat  liberated.     In  the  cold-blooded  animals,  whose  tem- 


*  This  subject  is  more  fully  treated  in  the  Author's  Principles  of  General  and  Compara- 
tive Physiology,  §§  548—567. 

•j"  See  the  very  interesting  experiments  of  MM.  Vrolik  and  Vriese,  in  the  Ann.  des  Sci. 
Nat.,  N.  S.  Botan.,  torn,  xi.,  p.  551. 


DEVELOPMENT  OF  HEAT.  681 

perature  is  almost  entirely  dependent  upon  that  of  the  surrounding  element,  the  respiration 
is  feeble,  being  carried  on,  for  the  most  part,  through  the  medium  of  water.  In  the  warm- 
blooded Vertebrata,  however,  which  have  the  power  of  keeping  up  the  heat  of  their  bodies  to 
an  elevated  standard,  even  when  that  of  the  surrounding  air  is  far  beneath  it,  the  quantity  of 
oxygen  consumed  is  very  large  ;  and  that  required  by  Birds  is  more,  in  proportion  to  their  size, 
than  that  employed  by  Mammalia ;  as  we  should  expect  from  the  more  elevated  tempera- 
ture of  the  former.  In  the  class  of  Insects,  we  have  a  very  remarkable  illustration  of  the 
same  general  fact.  It  appears,  from  the  researches  of  Mr.  Newport,  that  Insects,  during 
their  larva  and  pupa  states,  and  even  in  their  perfect  condition  when  at  rest,  are  to  be  re- 
garded as  truly  cold-blooded,  animals  ;  their  temperature  rising  arid  falling  with  that  of  the 
surrounding  medium,  and  being  at  no  time  more  than  a  degree  or  two  above  it.  In  a  state 
of  activity,  however,  the  temperature  of  the  body  attains  a  considerable  elevation, — fre- 
quently as  much  as  10°  or  15°  above  that  of  the  air.  It  must  be  remembered  that,  owing 
to  their  larger  extent  of  surface  in  proportion  to  their  bulk,  small  animals  are  cooled  much 
more  rapidly  than  large  ones ;  and  the  temperature  of  Insects  would  probably  rise  much 
higher,  if  it  were  not  for  the  loss  they  are  thus  continually  experiencing,  which  is  greatly 
increased  by  the  action  of  the  wings.  In  one  of  Mr.  N.'s  experiments,  a  single  Humble-bee, 
in  a  state  of  violent  excitement,  communicated  to  three  cubic  inches  of  air  as  much  as  4° 
of  heat  within  five  minutes;  its  own  temperature  being  raised  7°  in  the  same  time.  When 
several  individuals  in  a  state  of  excitement,  however,  are  clustered  together,  so  that  the  loss 
of  heat  is  prevented,  the  elevation  of  temperature  is  much  more  considerable;  thus  a  ther- 
mometer introduced  among  seven  "Nursing-Bees"  stood  at  92^°,  whilst  the  external  air 
was  only  70°;  and  the  temperature  of  a  hive  was  raised  by  disturbing  it,  during  winter, 
from  4S^°  to  102°,  the  temperature  of  the  air  being  only  34£  at  the  time !  In  all  these 
instances,  the  amount  of  Oxygen  consumed  bears  an  exact  proportion  to  that  of  the  Heat 
evolved. 

890.  In  the  higher  animals,  as  in  the  lower,  exercise  has  a  considerable 
effect  in  producing  an  elevation  of  temperature ;  and,  that  this  is  not  merely 
due  to  the  acceleration  of  the  circulation,  is  shown  by  the  very  curious  fact, 
that  the  exercise  of  a  particular  muscle  will  cause  an  increase  in  the  heat 
liberated  from  it,  as  shown  by  needles  plunged  in  its  substance,  and  connected 
with  the  thermo-multiplier.*     It  may,  indeed,  be  stated  as  a  general  proposi- 
tion, applicable  as  well  to  different  parts  of  the  same  being,  as  to  different 
individuals,  that  the  development  of  Heat  is  proportional  to  the  activity  of  the 
molecular  processes  which  constitute  the  functions  of  Nutrition,  Secretion, 
&c. ;  increasing  with  their  activity,  and  diminishing  with  their  torpor.     It  is 
very  easy  to  explain,  on  this  principle,  the  known  influence  of  the  Nervous 
system  on  the  calorific  function :  since,  although  the  molecular  changes  in  the 
organized  fabric  are  not  dependent  upon  the  agency  of  that  system,  they  are 
very  much  influenced  by  it;  and  thus  we  can  readily  understand  how  a  state 
of  nervous  excitement  may  produce  an  elevation  of  temperature,  whilst  a  de- 
pression of  nervous  power  occasions  a  cooling  of  the  body.     The  experi- 
ments of  Sir  B.  Brodie,  Chossat,  and  others, — in  which   a  greater  or  less 
portion  of  the  nervous  centres  was  removed,  and  the  animal  cooled  notwith- 
standing the  maintenance  of  the  circulation, — by  no  means  prove  that  the 
Nervous  system  is  directly  concerned  in  the  production  of  heat;  since  in  all 
such  experiments,  there  is  a  gradual  loss  of  those  other  vital  powers,  which 
are  concerned  in  the  function  of  calorification.     From  the  experiments  of  Dr. 
W.  Philip  and  Dr.  Hastings,  it  appears  that  an  animal  whose  nervous  centres 
have  been  removed,  cools  much  faster  when  left  to  itself,  than  when  Artifi- 
cial Respiration  is  practised;  and  that,  if  the  cooling  have  made  much  pro- 
gress before  the  artificial  respiration  is  caused  to  commence,  the  temperature 
may  be  raised; — and  this,  too,  in  spite  of  the  very  imperfect  manner  in  which 
natural  Respiration  is  replaced  by  movements  artificially  effected. 

891.  That  the  maintenance  of  Animal  Heat  is  due  in  part  to  those  molecu- 
lar changes,  to  which  the  Cutaneous  Respiration  is  subservient,  appears  from 

*  See  the  experiments  of  MM.  Becquerel  and  Breschet,  in  Ann.  des  Sci.  Nat.  N.  S.  Zool., 
torn.  vi. 


682  GENERAL  REVIEW  OF  THE  NUTRITIVE  PROCESSES. 

the  following  experiments  recently  performed  by  MM.  Becquerel  and  Bres- 
chet.  The  hair  of  Rabbits  was  shaved  off,  and  a  composition  of  glue,  suet, 
and  resin,  forming  a  coating  through  which  air  could  not  pass,  was  applied 
over  the  whole  surface.  It  might  seem  natural  to  suppose  that,  by  preventing 
the  evaporation  of  the  sweat,  the  temperature  of  the  tissues  would  be  very 
sensibly  increased  ;  and  that,  by  this  increase  of  the  temperature  of  the  whole 
body,  a  high  state  of  fever  would  be  engendered,  with  the  symptoms  of  which 
the  animal  would  at  last  die.  But  the  contrary  occurred.  In  the  first  Rabbit, 
which  had  a  temperature  of  100°  before  being  shaved  and  plastered,  it  had 
fallen  to  891°  by  the  time  the  material  spread  over  him  was  dry.  An  hour 
after,  the  thermometer  placed  in  the  same  parts  (the  muscles  of  the  thigh  and 
chest)  had  descended  to  76°.  In  another  Rabbit,  prepared  with  more  care, 
by  the  time  that  the  plaster  was  dry,  the  temperature  of  the  body  was  not 
more  than  51°  above  that  of  the  surrounding  medium,  which  was  at  that  time 
69s°;  and  in  an  hour  after  this,  the  animal  died.  These  experiments  place 
in  a  very  striking  point  of  view  the  importance  of  the  Cutaneous  surface  as  a 
respiratory  organ,  even  in  the  higher  animals:  and  they  enable  us  to  under- 
stand how,  when  the  secreting  power  of  the  Lungs  is  nearly  destroyed  by 
disease,  the  heat  of  the  body  is  kept  up  to  its  natural  standard  by  the  action 
of  the  Skin.  A  valuable  therapeutic  indication,  also,  is  derivable  from  the 
knowledge  which  we  thus  gain,  of  the  importance  of  the  Cutaneous  Respira- 
tion ;  for  it  leads  us  to  perceive  the  desirableness  of  keeping  the  skin  moist, 
in  those  febrile  diseases  in  which  there  are  great  heat  and  dryness  of  the  sur- 
face, since  secretion  cannot  properly  take  place  through  a  dry  membrane.  Of 
the  relief  afforded  by  cold  or  tepid  sponging  in  such  cases,  experience  has 
given  ample  evidence. 

892.  All  the  foregoing  facts  point  to  the  formation  of  Carbonic  Acid,  by  the 
union  of  the  Oxygen  absorbed  from  the  air  with  Carbon  set  free  from  the 
body,  as  the  main  source  of  the  evolution  of  Heat  within  the  Animal  sys- 
tem. The  precise  mode  in  which  this  union  is  accomplished,  is  not  yet 
known;  but  it  is  certain  that,  in  whatever  manner  the  combination  may  take 
place,  a  certain  measure  of  caloric  must  be  generated.  The  combustion  of 
from  5  to  10  oz.  of  Carbon  per  day,  however,  would  be  by  no  means  suffi- 
cient to  keep  up  the  temperature  of  the  Human  body  to  its  proper  standard ; 
for  it  has  been  experimentally  ascertained,  that  the  amount  of  Caloric  set  free 
by  a  warm-blooded  animal  in  a  given  time  is  more  than  can  be  thus  accounted 
for.  It  does  not  hence  follow,  however,  that  we  are  to  look  to  any  other  than 
Chemical  processes,  for  the  explanation  of  this  most  important  function;  since 
there  can  be  no  doubt  that  there  are  many  other  changes  of  composition,  con- 
tinually taking  place  in  the  living  body,  which  have  their  share  in  the  pro- 
duction of  the  effect.  These  take  place,  for  the  most  part,  at  the  expense  of 
the  surplus  of  Oxygen  absorbed  over  that  which  is  given  out  in  the  form  of 
Carbonic  Acid;  this  surplus  amounting  to  as  much  as  15  per  cent,  of  the 
whole  (§  766).  Of  the  manner  in  which  this  surplus  is  employed,  no  precise 
account  can  be  given ;  but  there  can  be  little  doubt  that  part  of  it  is  expended 
in  uniting  with  Hydrogen,  to  form  a  portion  of  the  watery  vapour  which  is 
exhaled  from  the  lungs;  and  that  another  part  unites  with  the  Phosphorus 
and  Sulphur  which  are  taken  in  as  food  (forming  part  of  the  proteine-com- 
pounds  (§  114),  to  be  excreted  as  Phosphates  and  Sulphates  (§  847).  These 
and  other  changes,  in  which  the  absorbed  Oxygen  participates,  will  be  attended 
with  the  evolution  of  Caloric ;  and  thus  we  are  probably  to  account  for  the 
excess  of  Heat  generated  by  a  warm-blooded  animal  in  a  given  time,  above 
that  which  would  be  produced  by  the  combustion  of  the  amount  of  Carbon 
exhaled  by  it  during  the  same  period;  as  shown  in  the  experiments  of  Dulong 


DEVELOPMENT  OF  HEAT.  683 

and  Despretz.*  Although,  therefore,  the  Chemical  doctrine  of  Calorification 
cannot  be  regarded  as  yet  perfected  as  to  its  details,  there  can  be  no  reasonable 
doubt  that  it  is  altogether  sufficient  to  account  for  the  phenomena  in  question. 
And  it  may  be  stated  as  a  general  fact,  that  the  production  of  Animal  Heat  is 
due  to  the  various  changes  in  Chemical  composition,  that  are  continually 
taking  place  within  the  system ;  of  which  changes,  the  absorption  of  Oxygen, 
and  the  disengagement  of  Carbonic  Acid,  are  the  two  chief  external  manifesta- 
tions:— and  that  the  degree  of  Caloric  liberated  bears  a  close  relation  to  the 
activity  of  these  changes,  either  in  regard  to  the  body  at  large,  or  to  any 
portion  of  it. 

893.  The  researches  of  Dr.  Edwards  upon  Animal  Heat  have  brought  to 
light  some  very  interesting  facts,  regarding  the  diversity  which  exists  as  to 
the  power  of  generating  heat,  in  the  same  species  of  animal,  at  different  ages, 
and  at  different  periods  of  the  year. 

a.  It  appears  to  be  a  general  fact,  that  the  younger  the  animal,  the  less  is  its  independent 
calorifying  power.     The  development  of  the  embryo  of  oviparous  animals  is  entirely  de- 
pendent upon  the  amount  of  external  warmth  supplied  to  it;  and  there  are  many  kinds  of 
Birds,  which,  at  the  time  they  issue  from  the  egg,  are  so  deficient  in  the  power  of  generating 
heat,  that  their  temperature  rapidly  falls,  when  they  are  removed  from  the  nest  and  placed 
in  a  cold  atmosphere.     It  was  shown  by  collateral  experiments,  that  the  loss  of  heat  was 
not  to  be  attributed  to  the  absence  of  feathers,  nor  to  'the  extent  of  surface  exposed  in  com- 
parison with  the  bulk  of  the  body;  and  that  nothing  but  an  absolute  deficiency  in  the  power 
of  generating  it,  would  account  for  the  fall  of  temperature.     This  is  quite  conformable  to 
facts  well  ascertained  in  regard  to  Mammalia.     The  fcetus,  during  intra-uterine  life,  has 
little  power  of  keeping  up  its  own  temperature;  and  in  many  cases  it  is  much  dependent 
on  external  warmth,  for  some  time  after  birth.     The  degree  of  this  dependence,  however, 
differs  greatly  in  the  various  species  of  Mammalia,  as  among  Birds:  being  less,  in  propor- 
tion as  the  general  development  is  advanced.     Thus,  young  Guinea  pigs,  which  can  run 
about  and  pick  up  food  for  themselves  almost  as  soon  as  they  are  born,  are  from  the  first 
independent  of  parental  warmth ;  whilst,  on  the  other  hand,  the  young  of  Dogs,  Cats,  Rab- 
bits, &c.,  which  are  born  blind,  and  which  do  not,  for  a  fortnight  or  more,  acquire  the  same 
development  with  the  preceding,  rapidly  lose  their  heat  when  withdrawn  from  contact  with 
jhe  body  of  the  mother. 

b.  In  the  Human  species  it  is  well  known,  that  external  warmth  is  necessary  for  the 
Infant;  but  the  fact  is  too  often  neglected  (under  the  erroneous  idea  of  hardening  the  con- 
stitution) during  the  early  years  of  childhood.     It  is  to  be  carefully  remembered,  that  the 
development  of  Man  is  slower  than  that  of  any  other  animal;  and  that  his  calorifying 
power  is  closely  connected  with  his  general  bodily  vigour.     In  the  case  of  children  born 
very  prematurely,  the  greatest  attention  must  be  given  to  the  sustenance  of  the  heat  of  the 
body  (§  932) ;  and  though  the  infant  becomes  more  independent  of  it  as  development 
advances,  it  is  many  years  before  the   standard  can  be  maintained  without  assistance, 
throughout  the   ordinary  vicissitudes  .  of  external   temperature.      The   calorifying   power, 
which  is  fully  possessed  by  adults,  decreases  again  in  advanced  age.     Old  people  complain 
that  their  "  blood  is  chill;"  and  they  suffer  greatly  from  exposure  to  cold,  the  temperature  of 
their  whole  body  being  lowered  by  it. 

c.  These  facts  have  a  very  interesting  connection  with  the  results  of  statistical  inquiries, 
as  to  the  average  number  of  deaths  at  different  seasons,  recorded  by  M.  Queteletf 


*  It  has  been  recently  shown  by  Liebig,  that  the  discrepancy  between  the  actual  amount 
of  heat  generated,  and  the  amount  which  was  calculated  to  have  been  produced  by  the 
union  of  Carbon  and  Hydrogen  with  Oxygen,  to  form  the  Carbonic  Acid  and  Water  exhaled, 
in  these  experiments,  may  be  nearly  reconciled  by  adopting  a  more  correct  estimate  of  the 
heat  generated  by  combustion  of  given  quantities  of  Carbon  and  Hydrogen  respectively.  But 
all  these  calculations  proceed  upon  the  supposition,  that  the  whole  amount  of  Oxygen  ab- 
sorbed, which  is  not  exhaled  as  Carbonic  acid,  is  exhaled  in  combination  with  Hydrogen,  as 
Water ;  and  thus  no  account  is  taken  of  other  combustion-processes  going  on  in  the  body,  by 
which  a  greater  amount  of  heat  may  be  generated,  than  by  the  combustion  of  Hydrogen. 
We  have  no  means  whatever  of  ascertaining  how  much  of  the  watery  vapour  thrown  off 
by  the  lungs  and  skin  is  actually  formed  within  the  body,  and  how  much  is  the  mere  super- 
fluity of  the  liquid  ingested. 

|  Essai  de  Physique  Sociale,  torn.  i.  p.  197. 


684 


GENERAL  REVIEW  OF  THE  NUTRITIVE  PROCESSES. 


First 
Month. 

2—3 
Years. 

8—12 
Years. 

25—30 
Years. 

50—65 
Years. 

90  Years 
and  above. 

January 

1-39 

1-22 

1-08 

1-05 

1-30 

1-58 

February 

1-28 

1-13 

1-06 

1-04 

122 

1-48 

March 

1-21 

1-30 

1-27 

1-11 

1-11 

1-25 

April 

1-02 

1-27 

1-34 

1-06 

1-02 

0-96 

May 

0-93 

1-12 

1-21 

1-02 

0-93 

0-84 

June 

.0-83 

0-94 

0-99 

1-02 

0-85 

0-75 

July 

0-78 

0-82 

0-88 

0-91 

0-77 

0-64 

August 

0-79     . 

0-73 

0-82 

0-96 

0'85 

0-66 

September 

0-86 

0-76 

0-81 

0-95 

0-89 

0-76 

October 

0-91 

0-78 

0-76 

093 

0-90 

0-74 

November 

O93 

091 

0-80 

0-97 

1-00 

1-03 

December 

107 

1-01 

0-96 

0-97 

1-15 

1-29 

We  see  from  this  table  that,  during  the  first  month  of  infant  life,  the  external  temperature 
has  a  very  marked  influence;  for  the  average  mortality  during  each  of  the  three  summer 
months  being  80,  that  of  January  is  nearly  140,  and  the  average  of  February  and  March  is 
125.  This  is  confirmed  by  the  result  obtained  by  MM.  Villerme  and  Milne-Edwards,  in 
their  researches  on  the  mortality  of  the  children  conveyed  to  the  Foundling  Hospitals  in 
the  different  towns  in  France ;  for  they  not  only  ascertained  that  the  mortality  is  much  the 
greatest  during  the  first  three  months  in  the  year,  but  also  that  it  varies  in  different  parts  of 
the  kingdom,  according  to  the  relative  severity  of  the  winter.  As  childhood  advances,  how- 
ever, the  winter  mortality  diminishes,  whilst  that  of  the  spring  undergoes  an  increase ;  this 
is  probably  due  to  the  greater  prevalence  of  certain  epidemics  at  the  latter  season ;  for  the 
same  condition  is  observed,  in  a  still  more  remarkable  degree,  between  the  ages  of  8  and  12 
years, — the  time  when  children  are  most  severely  affected  by  such  epidemics.  As  the  con- 
stitution acquires  greater  vigour,  and  the  bodily  structure  attains  its  full  development,  the 
influence  of  the  season  upon  mortality  becomes  less  apparent;  so  that  at  the  age  of  from 
25  to  30  years,  the  difference  between  the  summer  and  winter  mortality  is  very  slight.  This 
difference  reappears,  however,  in  a  very  marked  degree,  at  a  later  period,  when  the  general 
vigour,  and  the  calorifying  powejs  undergo  a  gradual  diminution.  Between  the  ages  of  50 
and  65  it  is  nearly  as  great  as  in  early  infancy ;  and  it  gradually  becomes  more  striking, 
until,  at  the  age  of  90  and  upwards,  the  deaths  in  January  are  158,  for  every  64  in  July  (a 
proportion  of  2^  to  ] ) ;  and  the  average  of  the  three  winter  months  is  145,  whilst  that  of 
the  three  summer  months  is  only  68,  or  less  than  one-half. 

894.  Not  only  does  the  same  individual  possess  different  degrees  of  calori- 
fying power,  at  different  periods  of  his  life,  but  also  at  different  seasons  of 
the  year. 

a.  Dr.  Edwards  found  that  Sparrows,  when  exposed  for  some  time  to  a  temperature  of 
32°  during  the  summer,  rapidly  lost  heat,  the  refrigeration  during  3  hours  being  from  6  to 
21  degrees  ;  but  that,  when  they  were  placed  in  the  same  circumstances  during  winter  (after 
having  been  accustomed  to  a  warm  temperature)  the  refrigeration  was  much  less,  not  being 
in  any  instance  more  than  2°  in  3  hours.  Although  it  would  be  difficult  to  prove  the  fact 
experimentally  in  regard  to  Man,  there  can  be  little  doubt  that  he  shares  with  the  other 
Mammalia  in  this  variation.  It  is  well  known  that  the  general  vigour  of  the  system  is  less 
in  summer  than  in  winter;  in  hot  climates  than  in  moderately  cold.  Moreover,  we  con- 
tinually experience  the  great  discomforts  of  a  cold  day  in  summer;  when,  our  system  not 
being  prepared  for  it,  we  can  less  readily  maintain  our  temperature  at  its  normal  standard. 
The  practical  inference, — that  we  should  be  much  on  our  guard  against  exposure  to  low 
temperatures  during  summer, — is  one  of  much  importance ;  and  its  value  has  been  fully 
confirmed  by  experience.  The  same  principle  may  also  be  applied  to  the  explanation  of 
the  well-known  fact,  that  those  who  have  been  long  resident  in  warm  climates  feel  the  cold 
acutely ;  whilst  those  who  have  been  inured  to  cold  are  able  to  resist  it  much  better,  than 
those  who  are  exposed  to  it  for  the  first  time.  The  former  have  a  continued  summer  con- 
stitution ;  and  their  system  not  being  called  upon  by  its  external  conditions  to  produce  much 
heat,  the  power  is  after  a  time  partially  lost.  On  the  other  hand,  those  who  live  in  cold 
climates  have  a  perpetual  winter  constitution  (as  it  were)  established;  and  the  amount  of 
heat  generated  by  them  is  much  greater.  It  will  be  obvious  that  this  must  be  the  case,  if 
Man's  capability  of  living  under  the  greatest  varieties  of  climate  be  sufficiently  considered. 
From  Dr.  E.'s  experiments  it  appears,  that  every  month  makes  an  evident  difference  in  the 


DEVELOPMENT  OF  HEAT.  685 

seasonal  degree;  the  heat  lost  by  Sparrows  in  August  being  miuh  less  than  that  lost  by 
birds  of  the  same  species  in  July. 

895.  Our  knowledge  of  the  dependence  of  all  the  vital  processes  in  warm- 
blooded animals,  upon  the  Heat  of  their  bodies, — and  of  the  dependence  of 
their  Calorifying  power  upon  the  due  supply  of  material  for  the  Chemical 
changes  which  generate  Heat, — has  lately  received  some  very  remarkable 
additions  from  the  experiments  of  M.  Chossat.*     He  found  that  Birds,  when 
totally  deprived  of  food  and  drink,  suffered  a  progressive,  though  slight,  daily 
diminution  of  temperature.     This  diminution  was  not  so  much  shown  by  a 
fall  of  their  maximum  heat,  as  by  an  increase  in  the  diurnal  variation,  which 
he  ascertained  to  occur  even  in  the  normal  state.     The  amount  of  this  varia- 
tion, in  Birds  properly  supplied  with  food,  is  about  1£°  Fahr.  daily;  the 
maximum  being  about  noon,  and  the   minimum  at  midnight.      In  the  in- 
anitiated   state,   however,  the    average   variation   was    about   6°,  gradually 
increasing  as  the  animal  became  weaker:  moreover,  the  gradual  rise  of  tem- 
perature, which  should  have  taken  place  between  midnight  and  noon,  was 
retarded;   whilst  the  fall  subsequently  to  noon  commenced  much  earlier  than 
.in  the  healthy  state;  so  that  the  average  of  the  whole  day  was  lowered  by 
about  4|°  between  ihe  first  and  the  penultimate  days  of  this  condition.     On 
the  last  day,  the  production  of  Heat  diminished  very  rapidly,  and  the  ther- 
mometer fell  from  hour  to  hour,  until  death  supervened;  the  whole  loss  on 
that  day  being  about  25°  Fahr.,  making  the  total  depression  about  295°. 
This  depression  appears,  from  the  considerations  to  be  presently  stated,  to  be 
the  immediate  cause  of  Death. — On  examining  the  amount  of  loss  sustained 
by  the  different  organs  of  the  body,  it  was  found  that  93  per  cent,  of  the  Fat 
had  disappeared, — all,  in  fact,  which  could  be  removed;   whilst  the  Nervous 
Centres  scarcely  exhibited  any  diminution  in  weight.     The  loss  of  weight  of 
the  whole  body  averaged  about  40  per  cent. ;  and  that  of  the  various  other 
component  tissues  was  very  much  what  might  have  been  anticipated.     From 
the  constant  coincidence  between  the  entire  consumption  of  the  Fat,  and  the 
depression  of  Temperature, — joined  to  the  fact  that  the  duration  of  life  under 
the  inanitiating  process  evidently  varied  (other  things  being  equal)  with  the 
amount  of  Fat  previously  accumulated  in  the  body, — the  inference   seems 
irresistible,  that  the  Calorifying  power  depended  chiefly,  if  not  entirely,  on 
the  materials  supplied  by  this  substance.     The  maintenance  of  the  normal 
amount  of  matter  in  the  Nervous  centres,  is   a  very  remarkable  fact;  and 
seems  to  countenance  the  idea,  that  the  substances  peculiar  to  Nervous  tissue 
may  be  formed  from  Fatty  matter,  rather  than  from  a  Proteine-compound 
(§  249). 

896.  Whenever,  therefore,  the  store  of  combustible  matter  in  the  system  was 
exhausted, — whether  by  the  Respiratory  process  alone,  or  by  this  in  conjunc- 
tion with  the  conversion  of  Adipose  matter  into  the.  materials  for  the  Nervous 
or  other  tissues, — the  inanitiated  animals  died,  by  the  cooling  of  their  bodies 
consequent  upon  the  loss  of  Calorifying  power.     That  this  is  the  real  expla- 
nation of  the  fact,  is  shown  by  the  results  of  a  series  of  very  remarkable  ex- 
periments performed  by  M.  Chossat,  with  a  view  of  testing  the  correctness 
of  this  view.     When  inanitialed  animals  whose  death  seemed  impending  (in 
several  instances  death  actually  took  place,  whilst  the  preliminary  processes 
of  weighing,  the  application  of  the  thermometer,  &c.,  were  being  performed), 
were  subjected  to  artificial  heat,  they  were  almost  uniformly  restored  from  a 
state  of  insensibility  and  want  of  muscular  power  to  a  condition  of  compara- 
tive activity;  their  temperature  rose,  their  muscular  power  returned,  they  flew 

*  Recherches  Experimentales  sur  1'Inanition,  Paris,  1843.     See,  also,  the  Brit,  and  For. 
Med.  Rev.  for  April,  1844. 

58 


686  GENERAL  REVIEW  OF  THE  NUTRITIVE  PROCESSES. 

about  the  room  and  took  food  when  it  was  presented  to  them ;  and,  if  the  ar- 
tificial assistance  was  sufficiently  prolonged,  and  they  were  not  again  subjected 
to  the  starving  process,  most  of  them  recovered.  If  they  were  left  to  them- 
selves too  early,  however,  the  digestive  process  was  not  performed,  and  they 
ultimately  died.  Up  to  the  time  when  they  began  to  take  food,  their  weight 
continued  to  diminish ;  the  secretions  being  renewed,  under  the  influence  of 
artificial  heat,  sometimes  to  a  considerable  amount.  It  was  not  until  Diges- 
tion had  actually  taken  place  (which,  owing  to  the  weakened  functional  power, 
was  commonly  many  hours  subsequently  to  the  ingestion  of  the  food),  that 
the  animal  regained  its  power  of  generating  heat ;  so  that,  if  the  external 
source  of  heat  was  withdrawn,  the  body  at  once  cooled :  and  it  was  not  until 
the  quantity  of  food  actually  digested  was  sufficient  to  support  the  wants  of 
the  body,  that  its  independent  power  of  Calorification  returned.  It  is  to  be 
remembered  that,  in  such  cases,  the  resources  of  the  body  are  on  the  point  of 
being  completely  exhausted,  when  the  attempt  at  re-animation  is  made ;  con- 
sequently it  has  nothing  whatever  to  fall  back  upon ;  and  the  leaving  it  to  itself 
at  any  time  until  fresh  resources  have  been  provided  for  it,  is  consequently 
as  certain  a  cause  of  death,  as  it  would  have  been  in  the  first  instance. — It 
can  scarcely  be  questioned,  from  the  similarity  of  the  phenomena,  that  Inani- 
tion, with  its  consequent  depression  of  temperature,  is  the  immediate  cause 
of  death  in  various  Diseases  of  Exhaustion  ;  and  it  seems  probable  that  there 
are  many  cases,  in  which  the  depressing  cause  is  of  a  temporary  nature,  and 
in  which  a  judicious  and  timely  application  of  artificial  Heat  might  prolong 
life  until  it  has  passed  off, — just  as  artificial  Respiration  is  serviceable  in  cases 
of  Narcotic  Poisoning  (§  885).  It  is  especially,  perhaps,  in  those  forms  of 
Febrile  disease,  in  which  no  decided  lesion  can  be  discovered  after  death,  that 
this  view  has  the  strongest  claim  to  reception ;  but  many  other  cases  will 
occur  to  the  intelligent  Practitioner.* 

897.  Having  thus  considered  the  means,  by  which  the  degree  of  Heat  ne- 
cessary for  the  performance  of  the  functions  of  the  Human  system  is  gene- 
rated, we  have  to  inquire  how  its  temperature  is  prevented  from  being  raised 
too  high ;  in  other  words,  what  Frigorifying  means  there  are,  to  counter- 
balance the  influence  of  causes,  which  in  excess  would  otherwise  be  fatal,  by 
raising  the  heat  of  the  body  to  an  undue  degree.  How  is  it,  for  example, 
that,  when  a  person  enters  a  room  whose  atmosphere  is  heated  to  one  or 
two  hundred  degrees  above  his  body,  the  latter  does  not  partake  of  the  eleva- 
tion, even  though  exposed  to  the  heat  for  some  time  ?  Or,  since  the  inhabitants 
of  a  climate  where  the  thermometer  averages  100°  for  many  weeks  together, 
are  continually  generating  additional  heat  in  their  own  bodies,  how  is  it  that 
this  does  not  accumulate,  and  raise  them  to  an  undue  elevation  ?  The  means 
provided  by  Nature  for  cooling  the  body  when  necessary,  are  of  the  simplest 
possible  character.  From  the  whole  of  its  soft  moist  surface,  simple  Evapo- 
ration will  take  place  at  all  times,  as  from  an  inorganic  body  in  the  same  cir- 
cumstances ;  and  the  amount  of  this  will  be  regulated  merely  by  the  condi- 
tion of  the  atmosphere  as  to  warmth  and  dryness.  The  more  readily  watery 
vapour  can  be  dissolved  in  atmospheric  air,  the  more  will  be  lost  from  the 

*  The  beneficial  result  of  the  administration  of  Alcohol  in  such  conditions,  and  the  large 
amount  in  which  it  may  be  given  with  impunity,  may  probably  be  accounted  for  on  this 
principle.  That  it  is  a  specific  stimulus  to  the  Nervous  system,  cannot  be  doubted  from  its 
effects  on  the  healthy  body;  but  that  it  serves  as  a  fuel  to  keep  up  the  Calorifying. process, 
appears  equally  certain.  Now  its  great  efficacy  in  such  cases  seems  to  depend  upon  the 
readiness  with  which  it  will  be  taken  into  the  Circulation,  by  a  simple  act  of  Endosmotic 
Imbibition,  when  the  special  Absorbent  process  dependent  upon  the  peculiar  powers  of  the 
cells  of  the  villi  (§  181 ),  is  in  abeyance.  There  is  no  other  combustible  fluid,  whose  density, 
relatively  to  that  of  the  Blood,  will  permit  of  its  rapid  Absorption  by  the  simple  physical 
process  adverted  to. 


OF  REPRODUCTION.  687 

surface  of  the  body  in  this  manner.  In  cold  weather,  very  little  is  thus  carried 
off,  even  though  the  air  be  dry  :  and  a  warm  atmosphere,  already  charged 
with  dampness,  will  be  nearly  as  ineffectual.  But  simple  evaporation  is  not 
the  chief  means  by  which  the  temperature  of  the  body  is  regulated.  The 
Skin,  as  already  mentioned  (§  868),  contains  a  large  number  of  glandulae,  the 
office  of  which  is  to  secrete  an  aqueous  fluid ;  and  the  amount  of  this  Exha- 
lation appears  to  depend  solely  or  chiefly  upon  the  temperature  of  the  sur- 
rounding air.  Thus,  when  the  external  heat  is  very  great,  a  considerable 
amount  of  fluid  is  transuded  from  the  skin ;  and  this,  in  evaporating,  converts 
into  latent  heat  a  large  quantity  of  the  free  caloric,  which  would  otherwise 
raise  the  temperature  of  the  body.  If  the  atmosphere  be  hot  and  dry,  and 
also  be  in  motion,  both  Exhalation  and  Evaporation  go  on  with  great  rapidity. 
If  it  be  cold,  both  are  checked, — the  former  almost  entirely  so ;  but  if  it  be 
dry,  some  evaporation  still  continues.  On  the  other  hand,  in  a  hot  atmosphere, 
saturated  with  moisture,  Exhalation  continues,  though  Evaporation  is  almost 
entirely  checked;  and  the  fluid  poured  out  by  the  exhalant  glands  accumulates 
on  the  skin.  There  is  reason  to  believe  that  the  secretion  continues,  even 
when  the  body  is  immersed  in  water,  provided  its  temperature  be  high. — We 
learn  from  these  facts  the  great  importance  of  not  suddenly  checking  Exhala- 
tion, by  exposure  of  the  surface  to  cold,  when  the  secretion  is  being  actively 
performed ;  since  a  great  disturbance  of  the  circulation  will  be  likely  to  ensue, 
similar  to  that  which  has  been  already  mentioned,  as  occurring  when  other 
important  secretions  are  suddenly  suspended. 


CHAPTER    XVII. 

OF  REPRODUCTION. 

1. — General  Character  of  the  Function. 

898.  THE  Function  of  Reproduction  has  been  commonly  regarded  as  so 
entirely  different  in  character  from  the  ordinary  Nutritive  processes,  that  no 
analogy  can  be  drawn  between  them.  The  results  of  late  inquiries,  however, 
leave  nO  doubt  that  the  difference  between  them  is  extremely  small, — having, 
in  fact,  a  relation  rather  to  the  object  of  the  action,  than  to  the  mode  in  which 
it  is  performed.  In  the  ordinary  function  of  Nutrition,  there  is  a  continual 
regeneration  or  reproduction  of  the  tissues  and  organs  of  the  body;  but  the 
new  parts  are  destined  still  to  constitute  the  same  whole.  On  the  other  hand, 
in  Reproduction,  the  newly-formed  parts  are  destined  from  the  first  to  be  cast 
off  from  the  parent  structure,  and  to  become  new  individuals.  Still,  their  ori- 
gin is  essentially  the  same  in  both  instances  ;  as  appears  from  the  mode  in 
which  the  multiplication  of  the  lower  Plants  and  Animals  takes  place.  Thus 
in  the  simplest  Cryptogamia,  such  as  the  Yeast  Fungus,*  every  single  cell 
may  be  regarded  as  a  distinct  individual ;  since  it  is  capable  of  living  by  itself, 
and  of  generating  new  cells ;  and  thus  the  production  of  a  new  cell,  in  con- 
nfection  with  the  original  one,  may  be  regarded  as  alike  an  act  of  Nutrition 
and  of  Reproduction.  So  again,  in  the  Hydra  and  other  Polypes,  the  remark- 
able power  of  reparation  which  is  manifested  in  their  Nutritive  operations, 

*  See  Principles  of  General  and  Comparative  Physiology,  §  98. 


688  OF  REPRODUCTION. 

may  be  employed  in  generating  new  individuals ;  since,  when  the  body  is 
divided  into  numerous  parts,  each  one  of  these  has  the  power  of  developing 
all  the  rest  of  the  structure,  and  thus  of  becoming  a  complete  animal  (§  9). 
Still  we  find  in  most  Plants,  and  in  all  Animals,  some  portion  of  the  structure 
specially  designed  to  form  and  to  set  free  germs,  which  are  destined  to  become 
new  individuals  ;  and  it  is  in  the  liberation  and  development  of  these,  that  the 
function  of  Reproduction  essentially  consists. 

899.  In  Plants  it  is  very  evident  that  these  germs  differ  but  little  from 
those  which  elsewhere  produce  new  cells  (§  122) ;  and  that  the  first  aspect 
of  the  new  being  is  neither  more  nor  less  than  a  single  cell,  in  which  all  the 
other  cells  of  the  structure  subsequently  originate.     In  the  Cryptogamia,  the 
cell-germs  are  contained  in  what  is  termed  the  spore;  and,  when  liberated 
from  the  parent,  they  are  developed  into  cells  without  any  further  assistance 
than  that  which  they  derive  from  the  air,  moisture,  &c.,  that  surround  them. 
In  Flowering  Plants,  on  the  other  hand,  the  cell-germs  are  conveyed  into  a 
new  set  of  organs,  in  which  they  are  supplied  with  nutriment  previously  ela- 
borated for  them  by  the  parent ;  and,  in  this  manner,  they  are  enabled  to  attain 
an  ultimate  development  which  is  much  higher  than  that  of  the  Cryptogamia. 
It  is  now  well  established,  that  the  pollen-grain  of  Phanerogamia  is  analogous 
to  the  spore  of  Cryptogamia;  since  it-contains  the  reproductive  granules,  which 
are  the  germs  of  the  first  cells  of  the  new  individual.    When  the  pollen-grains 
are  cast  upon  the  stigmatic  surface,  they  project  one  or  more  long  tubes,  which 
insinuate  themselves  down  the  soft  loose  tissue  of  the  style,  and  reach  the 
ovarium.     Into  these  tubes,  the  granules  which  the  pollen-grain  contained  are 
seen  to  pass ;   and  they  are  thus  conveyed  into   the  ovules,  the  foramina  of 
which  are  penetrated  by  the  extremities   of  the  pollen-tubes.     The   ovules 
previously  contained  nothing  but-  starchy  matter;  but  from  the  time  that  the 
pollen-tubes  have  thus  implanted  (as  it  were)  their  contents  in  their  cavity, 
they  may  be  considered  as  fecundated.  The  subsequent  growth  of  the  embryo 
from  the  first-formed  cells,  takes  place  according  to  the  principles  already 
stated,  under  the  head  of  Nutrition;  and  thus  it  is  seen,  that  the  mysterious 
process  of  Reproduction  evidently  consists,  in  Flowering  Plants,  of  nothing 
else  than  the  implantation  of  a  cell-germ  prepared  by  the  male  organs,  in  a 
nidus  or  receptacle  adapted  to  aid  its  early  development,  which  nidus  consti- 
tutes the  essential  part  of  the  female  system. 

900.  There  is  now  good  reason  to  believe  that,  in  no  Animals,  is  the  Re- 
productive apparatus  less  simple  than  it  is  in  the  higher  Plants  ; — that  is  to 
say,  in  every  instance,  two  sets  of  organs,  a  germ-preparing,  and   a  germ- 
nourishing,,  are  present.     These  organs  differ  much  in  form  and  complexity 
of  structure  in  the  various  tribes  of  Animals  ;  but  their  essential  function  is 
the  same  in  all.     Those  which  are  termed  Male  organs  prepare  and  set  free 
certain  bodies,  which,  having  an  inherent  power  of  motion,  have  been  sup- 
posed to  be  independent  Animalcules,  and  have  been  termed  Spermatozoa ; 
there  is  but  little  reason,  however,  to  regard  them  in  this  light,  since  ciliated 
epithelium-cells  may  exhibit  as  much  activity  ;  and  there  is  no  evidence  that 
their  function  is  any  higher  than  that  of  the  pollen-tube  of  Plants,  which  con- 
veys into  the  ovulum  the  germs  of  the  first  cells  of  the  embryo.  This  view  of 
the  character  of  the  Spermatozoa  rests  alike  upon  the  nature  of  their  move- 
ments, and  the  mode  of  their  production.*     Dr.  Barry's  observations  on  the 
history  of  the  Ovum,  and  on  the  nature  of  the  act  of  Fecundation  (which  will 
be  presently  given  in  some  detail)  have  left  scarcely  any  doubt,  that  this  act 
consists  in  the  introduction  of  some  new  element  into  the  Ovule,  through  the 
medium  of  the  Spermatozoa ;  the  arrival  of  which  at  the  surface  of  the  ovary 

*  See  Principles  of  General  and  Comparative  Physiology,  §  606. 


ACTION  OF  THE  MALE. 

had  been  more  than  once  previously  seen,  and  the  penetration  of  which  to  the 
Ovum  there  was  good  reason  to  suspect :  and  these  have  been  confirmed  by 
the  observations  of  Dr.  A.  Farre  on  the  Ovum  of  the  Earth-worm,  which  he 
has  distinctly  seen  to  be  penetrated  by  Spermatozoa.  The  act  of  Fecunda- 
tion is  evidently  analogous,  therefore,  in  Animals,  to  the  process  which  has 
been  described  as  taking  place  in  the  Flowering  Plants.  In  many  of  the 
lower  tribes  of  Animals,  the  spermatic  fluid  effused  by  an  individual  of  one 
sex,  comes  into  direct  contact  with  the  ova  previously  deposited  by  the  other ; 
but  in  all  the  higher  tribes,  as  in  Man,  the  act  of  fecundation  is  performed  be- 
fore, or  shortly  after  the  ova  quit  the  ovarium.  With  these  general  views,  we 
shall  now  be  prepared  to  consider  the  share  which  each  sex  has  in  the  Function 
of  Reproduction. 

2.  Action  of  the  Male. 

901.  The  Spermatic  fluid  secreted  by  the  Testes  of  the  Male  (§  867),  differs 
from  all  other  secretions,  in  containing  a  large  number  of  very  minute  bodies, 
only  discernible  with  a  high  power  of  the  Microscope ;  and  these,  in  ordinary 
cases,  remain  in  active  motion  for  some  time  after  they  have  quitted  the  living 
body.  The  Human  Spermatozoon  (of  which  representations  are  given  in 
Plate  I,,  Fig.  18),  consists  of  a  little  oval  flattened  body  from  the  l-600th  to 
the  1 -800th  of  a  line  in  length,  from  which  proceeds  a  long  filiform  tail  gradu- 
ally tapering  to  the  finest  point,  of  l-50th  or  at  most  l-40th  of  a  line  in  length. 
The  whole  is  perfectly  transparent ;  and  nothing  that  can  be  termed  structure 
can  be  satisfactorily  distinguished  within  it.*  The  movements  are  principally 
executed  by  the  tail,  which  has  a  kind  of  vibratile  undulating  motion.  They 
may  continue  for  many  hours  after  the  emission  of  the  fluid ;  and  they  are  not 
checked  by  its  admixture  with  other  secretions,  such  as  the  urine  and  the 
prostatic  fluid.  Thus,  in  cases  of  nocturnal  emission,  the  Spermatozoa  may 
not  unfrequently  be  found  actively  moving  through  the  urine  in  the  morning; 
and  those  contained  in  the  seminal  fluid  collected  from  females  that  have  just 
copulated,  are  frequently  found  to  live  many  days.  Their  presence  may  be 
readily  detected  by  a  Microscope  of  sufficient  power,  even  when  they  have 
long  ceased  to  move,  and  are  broken  into  fragments ;  and  the  Physician  and 
the  Medical  Jurist  will  frequently  derive  much  assistance  from  an  examination 
of  this  kind.  Thus,  cases  are  of  no  uncommon  occurrence,  especially  among 
those  who  have  been  too  much  addicted  to  sexual  indulgence,  in  which  seminal 
emissions  take  place  unconsciously  and  frequently,  and  produce  great  general 
derangement  of  the  health;  and  the  true  nature  of  the  complaint  is  obscure, 
until  the  fact  has  been  detected  by  ocular  examination.  Again,  in  charges  of 
rape,  in  which  evidence  of  actual  emission  is  required,  a  microscopic  exami- 
nation of  the  stiffened  spots  left  on  the  linen  will  seldom  fail  in  obtaining  proof, 
if  the  act  have  been  completed :  in  such  cases,  however,  we  must  not  expect 
to  meet  with  more  than  fragments  of  Spermatozoa;  but  these  are  so  unlike 
anything  else,  that  little  doubt  need  be  entertained  regarding  them.  It  has 
been  proposed  to  employ  the  same  test,  in  juridical  inquiries  respecting  doubt- 
ful cases  of  death  by  suspension :  seminal  emissions  being  not  unfrequent 
results  of  this  kind  of  violence:  but  there  are  many  obvious  objections  which 
should  prevent  much  confidence  being  placed  in  it.t 

*  It  has  been  asserted  that  distinct  oral  and  anal  orifices,  with  appearances  of  internal 
organs,  have  been  seen  in  the  Spermatozoa  of  certain  Mammalia ;  but  these  observations 
have  not  been  confirmed ;  and  they  are  not  borne  out  by  the  attentive  examination  of  the 
larger  Spermatozoa  of  other  animals. 

f  See  the  Author's  Article  "Asphyxia,"  in  the  Library  of  Practical  Medicine,  and  the 
authorities  there  referred  to. 

58* 


690  OF  REPRODUCTION. 

902.  The  mode  of  Evolution  of  Spermatozoa,  which  has  been  recently 
discovered  by  Wagner,  is  so  different  from  the  ordinary  method  of  produc- 
tion amongst  Animalcules,  as  of  itself  to  indicate  that  the  former  cannot  be 
referred  to  the  same  category  with  the  latter.     It  may  be  best  studied  in  those 
animals  which  only  have  a  periodical  fertility ;  and  the  Passerine  Birds  are 
among  the  most  convenient  subjects  for  the  purpose.     During  the  winter,  the 
testes  are  small  and  almost  bloodless,  and  no  trace  of  Spermatozoa  can  be 
detected  within  them ;   on  the  return  of  spring,  however,  they  undergo  great 
enlargement  and  become  almost  gorged  with  blood,  and  the  gradual  steps  of 
the  evolution  of  the  Spermatozoa  may  be  easily  observed.     The  fluid  drawn 
from  them  is  first  seen  to  contain  a  number  of  granular  corpuscles,  resembling 
those  known  as  the  Seminal  Granules  in  the  human  semen  (delineated  at  «, 
Fig.  18,  Plate  I.);  and  in  a  short  time  there  are  seen,  in  addition  to  these, 
numerous  rounded  transparent  vesicles,  at  first  having  but  one  nucleus,  and 
afterwards  presenting  several.     These  nuclei  bear  a  close  resemblance  to  the 
granular  corpuscles  just  mentioned ;  and  it  is  probable  that  the  former  are  to 
be  regarded   as  cytoblasts,  from  which  the  Spermatoferous  cells  (shown,  as 
existing  in  the  human  semen,  in  Fig.  19,  Plate  I.)  are  evolved.     The  nuclei 
seem  afterwards  to  resolve   themselves  into  a  fine  granular  matter,  which  is 
diffused  through  the  whole  vesicle  or  "cyst  of  evolution ;"  and  in  this,  a  linear 
arrangement  soon  becomes  perceptible.     The  lines  become  more  and  more 
distinct,  and  are  at  last  seen  to  be  evidently  produced  by  the  arrangement  of 
the  Spermatozoa,  which  lie  side  by  side  within  the  vesicle;  and  the  form  of 
this   changes   from   a  sphere  to  a  long  oval.     After  a  time  they  break  forth, 
but  still  adhere  to  each  other  for  a  short  period,  forming  bundles,  such  as  may 
often  be  met  with  in  the  human  semen,  when  taken  directly  from  the  testis 
(Fig.  20,  Plate  I.).*     That  the  Spermatozoa  are  the  essential  elements  of  the 
spermatic  fluid,  has  been  reasonably  inferred  from  several  circumstances,  such 
as  their  absence  or  imperfect  development  in  hybrid  animals,  which  are  nearly 
or  entirely  sterile :   and  the  fact  that  Fecundation  essentially  consists  in  the 
direct  communication  of  one  of  them  with  a  certain  point  in  the  Ovum,  ap- 
pears too  well  established  to  admit  of  further  doubt.     Regarding  the  uses  of 
the  other  constituents  of  the  Semen,  no  sufficient  account  can  be  given. 

903.  The  power  of  procreation  does  not  usually  exist  in  the  Human  Male, 
until  the  age  of  from  14  to  16  years;  and  it  may  be  considered  probable  that 
no  Spermatozoa  are  produced  until  that  period,  although  a  fluid  is  secreted  by 
the  testes.     At  this  epoch,  which  is  ordinarily  designated  as  that  of  Puberty,  a 
considerable  change  takes  place  in  the  bodily  constitution:  the  sexual  organs 
undergo  a  much-increased  development;  various  parts  of  the  surface,  especially 
the  chin  and  the  pubes,  become  covered  with  hair;  the  larynx  enlarges,  and 
the  voice  becomes  lower  in  pitch,  as  well  as  rougher  and  more  powerful ;  and 
new  feelings  and  desires  are  awakened  in  the  mind.     Instances,  however,  are 
by  no  means  rare,  in  which  these  changes  take   place  at  a    much  earlier 
period;  the  full  development  of  the  generative  organs,  with  manifestations  of 
the  sexual  passion,  having  been  observed  in  children  of  but  a  few  years  old. 
The  procreative  power  may  last,  if  not  abused,  during  a  very  prolonged 
period.     Undoubted  instances  of  virility  at  the  age  of  more  than  100  years 
are  on  record;  but  in  these  cases,  the  general  bodily  vigour  was  preserved  in 
a  very  remarkable  degree.     The  ordinary  rule  seems  to  be,  that  sexual  power 
is  not  retained  by  the  male  in  any  considerable  degree,  after  the  age  of  60  or 
65  years.     To  the  use  of  the  sexual  organs  for  the  continuance  of  his  race, 

*  For  a  fuller  account,  with  illustrations,  of  the  development  of  the  Spermatozoa,  and  its 
analogy  with  the  formation  of  other  tissues,  see  Princ.  of  Gen.  and  Comp.  Phys.,  §§  430 
and  007. 


ACTION  OF  THE  MALE.  691 

Man  is  prompted  by  a  powerful  Instinctive  desire,  which  he  shares  with  the 
lower  animals.  This  Instinct,  like  the  others  formerly  alluded  to  (§  428 — 
430),  is  excited  by  sensations ;  and  these  may  either  originate  in  the  sexual 
organs  themselves,  or  may  be  excited  through  the  organs  of  special  sensation. 
Thus  in  Man  it  is  most  powerfully  aroused  by  impressions  conveyed  through 
the  sight  or  the  touch :  in  many  other  animals,  the  auditory  and  olfactive  organs 
communicate  impressions  which  have  an  equal  power ;  and  it  is  not  impro- 
bable that,  in  certain  morbidly-excited  states  of  feeling,  the  same  may  be  the 
case  in  ourselves.  That  local  impressions  have  also  a  very  powerful  effect  in 
exciting  sexual  desire,  must  have  been  within  the  experience  of  almost  every 
one ;  the  fact  is  most  remarkable,  however,  in  cases  of  Satyriasis,  which  dis- 
ease is  generally  found  to  be  connected  with  some  obvious  cause  of  irritation 
of  the  generative  system,  such  as  pruritus,  active  congestion,  &c.  That  some 
part  of  the  Encephalon  is  the  seat  of  this,  as  of  other  instinctive  propensities, 
appears  from  the  considerations  formerly  adduced ;  but  that  the  Cerebellum 
is  the  part  in  which  this  function  is  specially  located,  cannot  be  regarded  as 
by  any  means  sufficiently  proved  (§§  466 — 470).  The  instinct,  when  once 
aroused  (even  though  very  obscurely  felt),  acts  upon  the  mental  faculties  and 
moral  feelings;  and  thus  becomes  the  source,  though  almost  unconsciously  so 
to  the  individual,  of  the  tendency  to  form  that  kind  of  attachment  towards  one 
of  the  opposite  sex,  which  is  known  as  love.  This  tendency  cannot  be  re- 
garded as  a  simple  passion  or  emotion,  since  it  is  the  result  of  the  combined 
operations  of  the  reason,  the  imagination,  and  the  moral  feelings ;  and  it  is  in 
the  engraftment  (so  to  speak)  of  the  psychical  attachment,  upon  the  mere 
corporeal  instinct,  that  a  difference  exists  between  the  sexual  relations  of  Man 
and  those  of  the  lower  animals.  In  proportion  as  the  Human  being  makes 
the  temporary  gratification  of  the  mere  sexual  appetite  his  chief  object,  and 
overlooks  the  happiness  arising  from  spiritual  communion,  which  is  not  only 
purer  but  more  permanent,  and  of  which  a  renewal  may  be  anticipated  in 
another  world, — does  he  degrade  himself  to  the  level  of  the  brutes  that  perish. 
Yet  how  lamentably  frequent  is  this  degradation ! 

1  904.  When  impelled  by  sexual  excitement,  the  Male  seeks  intercourse  with 
the  Female,  the  erectile  tissue  of  the  genital  organs  becomes  turgid  with  blood 
(§  748),  and  the  surface  acquires  a  much-increased  sensibility ;  this  is  espe- 
cially acute  in  the  Glans  penis.  By  the  friction  of  the  Glans  against  the  rugous 
walls  of  the  Vagina,  the  excitement  is  increased ;  and  the  impression  which 
is  thus  produced  at  last  becomes  so  strong,  that  it  produces,  through  the 
medium  of  the  Spinal  Cord,  a  reflex  contraction  of  the  muscles  which  sur- 
round the  Vesiculae  Seminales  (§  393).  These  receptacles  discharge  their 
contents  (partly  consisting  of  semen  and  partly  of  a  secretion  of  their  own) 
into  the  Urethra;  and  from  this  they  are  expelled  with  some  degree  offeree, 
and  with  a  kind  of  convulsive  action,  by  its  own  Compressor  muscles.  Now 
although  the  sensations  concerned  in  this  act  are  ordinarily  most  acutely  plea- 
surable, there  appears  sufficient  evidence  that  they  are  by  no  means  essential  to 
its  performance;  and  that  the  impression  which  is  conveyed  to  the  Spinal  Cord 
need  not  give  rise  to  a  sensation,  in  order  to  produce  the  reflex  contraction  of 
the  Ejaculator  muscles  (§  372).  The  high  degree  of  nervous  excitement 
which  the  act  of  coition  involves,  produces  a  subsequent  depression  of  corre- 
sponding amount ;  and  the  too  frequent  repetition  of  it  is  productive  of  conse- 
quences very  injurious  to  the  general  health.  This  is  still  more  the  case  with 
the  solitary  indulgence,  which  (it  is  to  be  feared)  is  practised  by  too  many 
youths ;  for  this,  substituting  an  unnatural  degree  of  one  kind  of  excitement, 
for  that  which  is  wanting  in  another,  cannot  but  be  still  more  trying  to  the 
bodily  powers.  The  secretion  of  seminal  fluid  being,  like  other  secretions, 
very  much  under  the  control  of  the  nervous  system,  will  be  increased  by  the 


692  OF  REPRODUCTION. 

continual  direction  of  the  mind  towards  objects  which  awaken  the  sexual  pro- 
pensity (§  626,  note) ;  and  thus,  if  intercourse  be  very  frequent,  a  much  larger 
quantity  will  altogether  be  produced,  although  the  amount  emitted  at  each 
period  will  be  less.  The  formation  of  the  secretion  seems  of  itself  to  be  a 
much  greater  tax  upon  the  corporeal  powers,  than  might  have  been  supposed 
a  priori:  and  it  is  a  well-known  fact,  that  the  highest  degree  of  bodily  vigour 
is  inconsistent  with  more  than  a  very  moderate  indulgence  in  sexual  inter- 
course ;  whilst  nothing  is  more  certain  to  reduce  the  powers,  both  of  body 
and  mind,  than  excess  in  this  respect.  These  principles,  which  are  of  great 
importance  in  the  regulation  of  the  health,  are  but  results  of  the  general  law, 
which  prevails  equally  in  the  Vegetable  and  Animal  kingdoms, — that  the 
Development  of  the  Individual,  and  the  Reproduction  of  the  Species,  stand 
in  an  inverse  ratio  to  each  other. 

3. — Action  of  the  Female. 

905.  The  essential  part  of  the  Female  Generative  system  is  that  in  which 
the  Ova  are  prepared ;  the  other  organs  are  merely  accessory,  and  are  not  to 
be  found  in  a  large  proportion  of  the  Animal  kingdom.  In  many  of  the  lower 
animals,  the  Ovaria  and  Testes  are  so  extremely  like  each  other,  that  the  dif- 
ference between  them  can  scarcely  be  distinguished  ;  and  the  same  has  already 
been  stated,  regarding  the  condition  of  these  organs  in  Man,  at  an  early  period 
of  development  (§  866  6).  The  fact  is  one  of  no  small  interest.  In  the  lower 
animals,  the  Ovarium  consists  of  a  loose  tissue  containing  many  cells,  in  which 
the  Ova  are  formed,  and  from  which  they  escape  by  the  rupture  of  the  cell- 
walls  ;  in  the  higher  animals,  as  in  the  Human  female,  the  tissue  of  the  Ova- 
rium is  more  compact,  forming  what  is  known  as  the  stroma;  and  the  Ova, 
except  when  they  are  approaching  maturity,  can  only  be  distinguished  in  the 
interstices  of  this,  by-  the  aid  of  a  high  magnifying  power.  We  owe  to  Dr. 
Barry  the  discovery  of  the  earliest  stages  in  the  production  of  the  Ovum  and 
its  accessory  parts,  in  Mammalia  and  other  Vertebrata.  In  order  to  under- 
stand his  account,  however,  it  will  be  necessary  that  the  parts  of  which  the 
ovum  consists  should  be  previously  understood. — Taking  the  Fowl's  Egg  as  a 
familiar  illustration,  it  must  be  remarked,  in  the  first  place,  that  neither  the 
albumen  which  forms  the  white,  nor  the  shell-membrane  with  its  testaceous 
covering,  exist  in  the  Ovarian  Ovum  ;  these  portions  being  added  during  its 
passage  along  the  oviduct.  The  parts  which  we  have  to  analyze,  are  the 
Yolk-membrane  and  its  contents.  Within  the  Yolk-membrane,  we  find  in  the 
first  place,  the  Yolk  itself;  a  substance  consisting  in  part  of  albuminous  gran- 
ules, and  in  part  of  oily  globules.  Towards  the  centre,  the  character  of  the 
Yolk  in  some  degree  changes  ;  its  colour  being  lighter,  and  the  granules  pre- 
senting more  the  appearance  of  cells,  with  minuter  globules  in  their  interior. 
The  central  portion  is  termed  the  discus  vitellinus.  Occupying  the  centre  of 
the  yolk  (in  the  immature  ovulum)  is  a  large  cell,  very  distinct  in  aspect  from 
the  rest,  and  having  a  well-marked  nucleus  upon  its  walls.  This  is  termed 
the  germinal  vesicle;  and  the  nucleus,  the  germinal  spot. — The  Mammalian 
Ovum  contains  exactly  the  same  parts ;  but  the  yolk  is  much  smaller  in  pro- 
portion, and  corresponds  in  character  rather  with  the  discus  vitellinus,  than 
with  the  whole  yoljt  of  the  Bird's  egg.  The  Ovum  in  all  Vertebrated  animals 
is  produced  within  a  capsule  or  bag,  the  exterior  of  which  is  in  contact  with 
the  stroma  of  the  ovarium  ;  this  has  been  termed  in  Mammalia,  the  Graafian 
follicle,  after  the  name  of  its  first  discoverer ;  but  the  more  general  and  ap- 
propriate designation  of  Ovisac  has  been  given  to  it  by  Dr.  Barry,  who  has 
shown  that  it  exists  in  other  classes  of  Vertebrata.  Between  the  Ovum  and 
the  Ovisac,  in  Oviparous  animals,  there  is  scarcely  any  interval ;  but  in  the 


ACTION  OF  THE  FEMALE.  603 

Mammalia,  a  large  amount  of  granular  matter  is  present ;  and  this  arranges 
itself  into  some  peculiar  structures  discovered  by  Dr.  Barry,  and  presently  to 
be  described.  The  membrane  which  surrounds  the  yolk  in  Mammalia  has 
received,  on  account  of  its  thickness  and  peculiar  transparency,  the  designation 
of  zona  pellucida. — The  several  parts  of  the  Ovum  now  described  are  shown 
in  Fig.  5,  Plate  I. 

906.  From  the  researches  of  Dr.  Barry  on  the  early  development  of  the 
Ovum,  it  appears  that  the  Germinal  Vesicle  is  the  part  which  can  first  be 
distinctly  traced.     In  Fig.  1  (Plate  I.)  is  seen  a  representation  of  one  of  its 
incipient  stages  in  the  Rabbit;  there  is  nothing  here  visible,  but  a  collection 
of  very  transparent  vesicles,  surrounded  by  a  mass  of  dark  granules.     In  the 
succeeding  stage,  represented  in  Fig.  2,  some  of  the  vesicles  have  enlarged, 
and  the  granules  immediately  surrounding  them  have  become  developed  into 
cells.    A  more  advanced  condition  is  represented  (on  a  smaller  scale)  in  Fig. 
3 ;  in  which  a  distinct  spot  (b)  is  seen  on  the  central  vesicle  (a),  marking  it  as 
the  Germinal  Vesicle ;  whilst  many  of  the  granules  surrounding  it  have  be- 
come cells,  and  have  taken-on  a  very  regular  arrangement.     After  a  time,  a 
membrane  forms  around  each  cluster  of  granules,  separating  it  from  the  stroma 
of  the  ovarium  ;  this  is  the  Ovisac.    At  a  later  period,  a  separation  takes  place 
between  the  inner  and  outer  portions  of  the  mass  of  granular  matter,  included 
between  the  ovisac  and  the  germinal  vesicle  ;  and  the  separation  is  completed 
by  the  development  of  a  membrane,  which  envelopes  the  inner  stratum.    This 
stratum  becomes  the  Yolk,  and  includes  most  of  the  oil-particles  which  pre- 
viously existed  within  the  ovisac ;  whilst  the  portion  of  the  granular  mass, 
exterior  to  this,  gives  origin  in  Mammalia  to  certain  structures  of  a  very  pe- 
culiar character,  which  seem  to  be  concerned  in  the  liberation  of  the  ovum 
from  the  Graafian  follicle  or  Ovisac.     The  appearance  of  the  Human  Ovisac 
and  its  contents  is  seen  in  Fig.  4.     The  granules  immediately  surrounding 
the  Ovum  assume  the  appearance  of  cells ;  and  these  unite  to  form  a  sort  of 
membrane,  to  which  the  name  of  tunica  granulosa  has  been  given.     This  is 
seen  at  t  g  (Fig.  7).    The  granules  lining  the  Ovisac  also  combine  themselves 
into  a  membranous  structure ;  to  which  Dr.  Barry  has  given  the  designation 
of  membrana  granulosa  (g  g.  Fig.  6).     These  are  connected  by  four  band- 
like  extensions  of  the  same  cellulo-membranous  structure,  which  seem  to  sus- 
pend the  ovum  in  its  place ;  and  these  are  called  retinacula  (r  r,  Figs.  6  and 
7).    The  space  between  the  Tunica  Granulosa  and  the  Membrana  Granulosa, 
which  is  not  occupied  by  the  Retinacula,  is  filled  with  fluid,  in  which  few  or 
no  cells  can  be  seen.    The  uses  of  this  structure,  so  far  as  they  are  apparent, 
will  be  described,  when  the  processes  by  which  the  Ovum  escapes  from  the 
Ovary  are  detailed. 

907.  The  Ovisac  does  not  form  the  entire  structure  which  has  been  described 
as  the  Graafian  follicle ;  for  this  consists  of  two  layers,  of  which  the  inner 
one  is  the  true  Ovisac,  whilst  the  outer  results  from  a  thickening  and  conden- 
sation of  the  surrounding  layer  of  the  Stroma  of  the  Ovarium.    It  is  the  outer 
layer  only  which  is  vascular ;  the  inner  presents  no  trace  of  structure ;  and 
the  increase  of  the  ovum  must  take  place  by  simple  imbibition,  through  it,  of 
the  supply  of  nutritive  matter  brought  into  contact  with  its  exterior.     The 
Ovarium  may  be  seen,  even  in  the  fetal  animal,  to  contain  immature  Ova ;  in 
which  the  several  parts  can  be  clearly  distinguished.     At  a  later  period,  how- 
ever, the  number  of  Ova  greatly  increases  ;  and  the  development  of  some  ad- 
vances, whilst  others  degenerate.     According  to  the  recent  valuable  inquiries 
of  Dr.  Ritchie,*  it  appears  that,  even  during  the  period  of  childhood,  there  is  a 
continual  rupture  of  Ovisacs,  and  discharge  of  Ova,  at  the  surface  of  the 

*  London  Medical  Gazette,  1844. 


694  OF  REPRODUCTION. 

Ovarium.  The  Ovaria  are  studded  with  numerous  minute  copper-coloured 
maculae ;  and  their  surface  presents  delicate  vesicular  elevations,  which  are 
occasioned  by  the  most  matured  ovisacs  :  the  dehiscence  of  these  takes  place 
by  minute  punctiform  openings  in  the  peritoneal  coat ;  and  no  cicatrix  is  left. 
At  the  period  of  puberty,  the  stroma  of  the  ovarium  is  crowded  with  Ovisacs; 
which  are  still  so  minute,  that  in  the  Ox  (according  to  Dr.  Barry's  computa- 
tion) a  cubic  inch  would  contain  200  millions  of  them.  The  greatest  advance 
is  seen  in  those  which  are  situated  nearest  the  surface  of  the  Ovarium;  and 
in  these,  the  Graafian  follicle  with  its  two  coats,  may  be  distinctly  traced.  It 
is  curious  that  the  outer  wall  (which  is  itself  a  part  of  the  condensed  stroma 
of  the  ovarium)  should  contain  an  immense  number  of  minute  ovisacs ;  so 
that  this,  in  the  adult  animal,  is  the  most  convenient  situation  in  which  to 
view  them:  these  ovisacs  have  been  termed  by  Dr.  Barry  "  parasitic  ovisacs." 
In  those  animals  whose  aptitude  for  conception  is  periodical,  the  development 
of  the  Ova,  to  such  a  degree  that  they  become  prepared  for  fecundation,  is 
periodical  also.  This  development  becomes  evident,  when  the  parts  are  ex- 
amined in  an  animal  which  is  "  in  heat,"  by  the  projection  of  the  Graafian 
follicles  from  the  surface  ;  and  it  consists  not  merely  in  an  increase  of  size, 
but  in  certain  internal  changes  presently  to  be  described. 

908.  In  the  Human  female,  the  period  of  Puberty,  or  of  commencing  apti- 
tude for  procreation,  is  usually  between  the  13th  and  16th  year;  it  is  earlier 
in  warm  climates  than  in  cold  ;*  and  in  densely-populated  manufacturing  towns, 
than  in  thinly  peopled  agricultural  districts.  The  mental  and  bodily  habits 
of  the  individual  have  also  a  considerable  influence  upon  the  time  of  its 
occurrence ;  girls  brought  up  in  the  midst  of  luxury  or  sensual  indulgence, 
undergoing  this  change  earlier  than  those  reared  in  hardihood  and  self-denial. 
The  changes  in  which  Puberty  consists,  are  for  the  most  part  connected  with 
the  Reproductive  system.  The  external  and  internal  organs  of  generation 

[*It  has  been  stated,  by  almost  all  physiological  writers,  that  women  reach  maturity,  and 
that  menstruation  commences  much  earlier  in  hot  climates,  particularly  between  the  tropics, 
than  in  temperate  and  very  cold  countries.  Haller  states  that  in  the  warm  regions  of  Asia, 
the  catamenia  appear  from  the  8th  to  the  10th  year;  and  in  Switzerland,  Britain,  and  other 
temperate  regions,  at  the  age  of  12  or  13,  and  later  the  farther  we  ascend  towards  the  north. 
The  same  view  has  been  held  by  nearly  all  subsequent  writers  on  the  subject,  and  they  infer 
that  animals,  like  plants,  reach  maturity  sooner  in  hot  than  in  cold  climates.  Dewees  says 
that  menstruation  occurs  later  in  our  northern  than  in  our  southern  states.  From  many 
elaborate  and  interesting  papers  which  have  been  published  within  a  few  years,  especially 
from  those  of  Mr.  Roberton  of  Manchester,  it  would  seem  that  the  natural  period  of  puberty 
in  women  occurs  in  a  much  more  extended  range  of  agesy  and  is  much  more  equally  dis- 
tributed through  that  range  than  others  have  alleged,  and  that,  in  other  countries,  the  parallel 
between  plants  and  fruits  does  not  hold  good. 

At  Gottingen,  Osiander  ascertained  the  ages  at  which  1 37  women  began  to  menstruate. 
In  21  of  these  the  catamenia  appeared  at  14;  in  32  at  15;  in  24  at  16;  9  at  12 ;  and  1  not 
before  the  24th  year.  The  Indian  girls  in  Canada,  and  in  our  north-western  states  and  ter- 
ritories, begin  to  menstruate  frequently  at  12,  13  and  14.  From  the  statement  of  Baron 
Humboldt,  the  same  is  equally  true  of  the  Korriacs,  and  the  tribes  of  northern  Asia,  where 
girls  of  10  years  are  sometimes  found  mothers.  The  notion  that  women  in  Lapland  do  not 
menstruate  till  20,vand  then  only  during  summer,  is  founded  on  a  mistake  in  Linnaeus's 
Flora  Lapponica.  Tooke  states  that  the  Sclavonian,  or  native  Russians,  reach  puberty  at  an 
early  age ;  and  Dr.  Robert  Lee,  who  was  in  the  Crimea,  and  all  the  Russian  provinces  along 
the  Black  Sea,  and  in  the  Ukraine,  and  whose  opportunities  of  observation  were  extensive, 
says  that  his  conviction  is,  that  over  the  whole  south  of  Russia  the  period  of  puberty  is  the 
same  as  in  Great  Britain ;  and  that  women  cease  to  bear  children  at  the  same  age.  The 
same  would  appear  to  hold  good  in  Java,  and  in  all  the  islands  of  the  Indian  Archipelago,  and 
in  Sierra  Leone;  and  the  difference  said  to  exist  in  Arabia  in  this  respect  is  due  to  the 
early  marriages,  and  universal  licentiousness  and  depravity  of  morals  in  that  country.  It 
would  appear  from  observations  made  in  the  West  India  Islands,  that  menstruation  occurs 
there  about  the  same  period,  and  that  the  alleged  difference  in  this  respect  between  the 
negress  and  the  white  female  does  not  exist. — M.  C.] 


ACTION  OF  THE  FEMALE.  695 

undergo  a  considerable  increase  of  size ;  the  mammary  glands  enlarge  ;  and  a 
deposition  of  fat  takes  place  in  the  mammae  and  on  the  pubes,  as  well  as  over 
the  wjiole  surface  of  the  body,—- giving  to  the  person  that  roundness  and  ful- 
ness, which  are  so  attractive  to  the  opposite  sex,  at  the  period  of  commencing 
Womanhood.  The  first  appearance  of  the  Catamenia  usually  occurs  whilst 
these  changes  are  in  progress,  and  is  a  decided  indication  of  the  arrival  of  the 
period  of  Puberty;  but  it  is  not  unfrequently  delayed  much  longer;  and  its 
absence  is  by  no  means  to  be  regarded  as  a  proof  of  the  want  of  aptitude  for 
procreation,  since  many  women  have  borne  large  families,  without  having  ever 
menstruated.  The  Catamenial  discharge  appears  normally  to  consist  of  blood 
deprived  of  its  fibrine ;  the  fluid  being  composed  of  serum,  in  which  red  cor- 
puscles are  suspended,  and  being  readily  distinguishable  from  true  blood  by 
its  want  of  power  to  clot.  When  clots  are  found  in  it,  therefore,  a  morbid 
condition  of  the  secreting  surface  must  be  inferred.  The  interval  which  usu- 
ally elapses  between  the  successive  appearances  of  the  secretion,  is  about  four 
weeks ;  and  the  duration  of  the  flow  is  from  three  to  six  days.  There  is, 
however,  great  variety  in  this  respect  among  the  inhabitants  of  different  cli- 
mates, and  among  individuals ;  in  general,  the  appearance  is  more  frequent, 
and  the  duration  of  the  flow  greater,  among  the  residents  in  warm  countries, 
and  among  individuals  of  luxurious  habits  and  relaxed  frame,  than  among  the 
inhabitants  of  colder  climes,  or  among  individuals  inured  to  bodily  exertion. 
The  first  appearance  of  the  discharge  is  usually  preceded  and  accompanied  by 
considerable  general  disturbance  of  the  system;  especially  pain  in  the  loins 
and  a  sense  of  fatigue  in  the  lower  extremities  ;  and  its  periodical  return  is 
usually  attended  with  the  same  symptoms,  which  are  more  or  less  severe  in 
different  individuals. 

909.  Much  discussion  has  taken  place  respecting  the  causes  and  purposes 
of  the  Menstrual  flow ;  and  recent  inquiries  have  thrown  much  light  upon 
them.  The  state  of  the  Female  Generative  system,  during  its  continuance, 
appears  to  be  analogous  to  the  heat  of  the  lower  animals ;  many  of  which 
have  a  sero-sanguinolent  discharge  at  that  period.  There  is  good  reason  to 
believe  that  in  Women  the  sexual  feeling  becomes  stronger  at  that  epoch ; 
and  it  is  quite  certain  that  there  is  a  greater  aptitude  for  Conception,  imme- 
diately before  and  after  Menstruation,  than  there  is  at  any  intermediate  period. 
Observations  to  this  effect  were  made  by  Hippocrates,  and  were  confirmed  by 
Boerhaave  and  Haller ;  indeed  coitus  immediately  after  menstruation  appears 
to  have  been  frequently  recommended  as  a  cure  for  sterility,  and  to  have 
proved  successful.  It  is  well  known  that,  among  many  of  the  lower  animals, 
the  Ova  are  entirely  extruded  by  the  Female,  before  the  Spermatic  fluid  of 
the  Male  reaches  them  ;  and  that  even  in  Birds,  this  occasionally  takes  place. 
This  question  has  been  recently  made  the  subject  of  special  inquiry  by  M. 
Raciborski ;  who  affirms  that  the  exceptions  to  the  rule — that  Conception 
occurs  immediately  before  or  after,  or  during,  Menstruation — are  not  more 
than  6  or  7  per  cent.  Indeed,  in  his  latest  work  on  this  subject,*  he  gives  the 
details  of  15  cases,  in  which  the  date  of  Conception  could  be  accurately  fixed, 
and  the  time  of  the  last  appearance  of  the  Catamenia  was  also  known  ;  and  in 
all  but  one  of  them,  the  correspondence  between  the  two  periods  was  very 
close.  Even  in  the  exceptional  case,  the  Catamenia  made  their  appearance 
shortly  after  the  Coitus  ;  which  took  place  at  about  the  middle  of  the  interval 
between  the  two  regular  periods.  When  Conception  occurs  immediately  be- 
fore the  Menstrual  period,  the  Catamenia  sometimes  appear,  and  sometimes 
are  absent ;0f  they  appear,  their  duration  is  generally  less  than  usual, 
fact  that  Conception  often  takes  place  immediately  before  the  last  appearance 

*  Sur  la  Ponte  des  Mammiferes.     Paris,  1844. 


696  OF  REPRODUCTION. 

of  the  Catamenia  (and  not  after  it,  as  commonly  imagined),  is  one  well  known 
to  practical  men.  Numerous  cases  have  been  collected  by  Mr.  Girdwood, 
Dr.  Robert  Lee,  MM.  Gendrin,  Negrier,  Raciborski,  and  others,  in  which  the 
Menstrual  period  was  evidently  connected  with  the  maturation  and  discharge 
of  Ova ;  but  the  most  complete  observations  yet  made  upon  this  subject,  are 
those  of  Dr.  Ritchie  (loc.''cit.)  He  states  that  about  the  period  of  Puberty  a 
marked  change  usually  takes  place  in  the  mode  in  which  the  Ovisacs  discharge 
their  contents  ;  but  that  this  change  does  not  necessarily  occur  simultaneously 
with  the  first  appearance  of  the  Catamenia ;  as  in  some  cases  the  conditions, 
which  obtain  in  the  period  before  puberty,  are  extended  into  that  of  menstrua- 
tion. The  Ovaries  now  receive  a  much  larger  supply  of  blood;  and  the  Ovi- 
sacs show  a  great  increase  in  bulk  and  vascularity  ;  so  that,  when  they  appear 
at  the  surface  of  the  ovary,  they  present  themselves  as  pisiform  turgid  eleva- 
tions ;  and  the  discharge  of  their  contents  leaves  a  much  larger  cicatrix,  and 
is  accompanied  by  an  effusion  of  blood  into  their  cavity,  with  other  subsequent 
changes,  to  be  presently  described.  It  would  appear,  however,  that  although 
such  a  discharge  takes  place  most  frequently  at  the  Menstrual  period,  yet  that 
the  two  occurrences  are  not  necessarily  co-existent;  for  menstruation  may 
take  place  without  any  such  rupture ;  whilst,  on  the  other  hand,  the  matura- 
tion and  discharge  of  mature  ova  may  occur  in  the  intervals  of  Menstruation, 
and  even  at  periods  of  life  when  that  function  is  not  taking  place.  The 
essential  condition  of  Menstruation  itself  would  appear  to  be  the  increased 
turgescence  of  the  vessels  of  the  Uterus ;  and  the  appearance,  on  its  internal 
surface,  of  a  meshwork  of  deciduous  villous  vessels,  which  may  remain  for  at 
least  two  weeks.  It  is  evident  that  this  is  a  preparation  for  the  formation  of 
the  Decidua  (§  919). 

910.  The  duration  of  the  period  of  aptitude  for  procreation,  as  marked  by 
the  persistence  of  the  Catamenia,  is  more  limited  in  Women  than  in  Men; 
usually  terminating  at  about  the  45th  year;  it  is  sometimes  prolonged,  how- 
ever, for  ten  or  even  fifteen  years  longer ;  but  cases  are  rare  in  which  women 
above  50  years  of  age  have  borne  children.     There  is  usually  no  Menstrual 
flow  during  Pregnancy  and  Lactation ;  in  fact,  the  cessation  of  the  Catamenia 
is  generally  one  of  the  first  signs,  indicating  that  Conception  has  taken  place. 
But  it  is  by  no  means  uncommon  for  them  to   appear  once  or  twice  subse- 
quently to  Conception ;  and  in  some  women,  there  is  a  regular  monthly  dis- 
charge, though  probably  not  of  the  usual  secretion,  through  the  whole  period. 
Some  very  anomalous   cases   are  recorded,  in  which  the  Catamenia  never 
appeared  at  any  other  time  than  during  Pregnancy  ;  and  were  then  regular. 
The  absence  of  the  Catamenia  during  Lactation  is  by  no  means  constant, 
especially  if  the  period  be  prolonged ;  when  the  Menstrual  discharge  recurs, 
it  may  be  considered  as  indicating  an  aptitude  for  Conception  ;  and  it  is  well 
known  that,  although  Pregnancy  seldom   recurs  during  the   continuance  of 
Lactation,  the  rule  is  by  no  means  invariable. 

911.  The  function  of  the  Female,  during  the  coitus,  is  entirely  of  a  passive 
character.     When  the  sexual  feeling  is  strongly  excited,  there  is  a  considera- 
ble degree  of  turgescence  in  the  erectile  tissue  surrounding  the  vagina,  and 
composing  the  greater  part  of  the  nymphae  and  the  clitoris ;  and  there  is  also 
an  increased  secretion  from  the  mucous  follicles.*     But  these  changes  are  by 

[*  The  glands  of  Duverney  have  been  lately  (1840)  very  accurately  described  by  Profes- 
sor Tiedemann,  his  attention  having  been  directed  to  these  organs  by  the  late  Dr.  Fricke,  of 
Hamburg.  These  glands  are  situated  at  either  side  of  the  entrance  of  the  ^agina,  beneath 
the  integument  covering  the  inferior  part  of  the  vagina,  as  well  as  the  superficial  perineal 
fascia,  and  the  constrictor  vaginae  muscle.  The  space  they  occupy  lies  between  the  lower 
end  of  the  vagina,  the  ascending  ramus  of  the  ischium,  the  crus  clitoridis,  and  the  erector 
clitoridis  muscle.  Superiorly  are  the  fibres  of  the  levator  ani  which  are  attached  to  the 


ACTION  OF  THE  FEMALE.  697 

no  means  necessary  for  effectual  coition ;  since  it  is  a  fact  well  established, 
that  fruitful  intercourse  may  take  place,  when  the  female  is  in  a  state  of  nar- 
cotism, of  somnambulism,  or  even  of  profound  ordinary  sleep.  It  has  been 
supposed  by  some,  that  the  os  uteri  dilates,  by  a  kind  of  reflex  action,  to  re- 
ceive the  semen;  but  of  this  there  is  no  evidence.  The  introduction  of  a 
small  quantity  of  the  fluid  just  within  the  Vagina,  appears  to  be  all  that  is 
absolutely  necessary  for  conception;  for  there  are  many  cases  on  record,  in 
which  pregnancy  has  occurred,  in  spite  of  the  closure  of  the  entrance  to  the 
vagina  by  a  strong  membrane,  in  which  but  a  very  small  aperture  existed. 
That  the  Spermatozoa  make  their  way  towards  the  Ovarium,  and  fecundate 
the  Ovum  either  before  it  entirely  quits  the  Ovisac  or  very  shortly  afterwards, 
appears  to  be  the  general  rule  in  regard  to  the  Mammalia;  and  the  question 
naturally  arises, — by  what  means  do  they  arrive  there.  It  has  been  supposed 
that  the  action  of  the  cilia,  which  line  the  Fallopian  tubes,  might  account  for 
their  transit;  but  the  direction  of  this  is  from  the  Ovaria  towards  the  Uterus, 
and  would  therefore  be  opposed  to  it.  A  peristaltic  action  of  the  Fallopian 
tubes  themselves  may  generally  be  noticed  in  animals  killed  soon  after  sexual 
intercourse ;  and  in  those  which  have  a  two-horned  membranous  Uterus,  such 
as  is  evidently  but  a  dilatation  of  the  Fallopian  tube,  this  partakes  of  the  same 
movement,  as  may  be  well  seen  in  the  Rabbit :  in  animals,  however,  which 
have  a  single  Uterus  with  thicker  walls  (as  in  the  Human  female),  it  must 
evidently  be  unavailable.  Among  the  tribes  whose  Ova  are  fertilized  out  of 
the  body,  the  power  of  movement  inherent  in  the  Spermatozoa  is  obviously 
the  means  by  which  they  are  brought  in  contact  with  the  Ova :  and  it  does 
not  seem  unreasonable  to  suppose,  that  the  same  is  the  case  in  regard  to  the 
higher  classes ;  and  that  the  transit  of  these  curious  particles,  from  the  Va- 
gina to  the  Ovaries,  is  effected  by  the  same  kind  of  action  as  that  which 
causes  them  to  traverse  the  field  of  the  microscope. — We  shall  now  consider 
the  changes  in  the  Ovum  and  its  appendages,  by  which  it  is  prepared  for 
fecundation. 

912.  Up  to  the  period  when  the  Ovum  is  nearly  brought  to  maturity,  it  re- 
mains in  the  centre  of  the  Ovisac  or  inner  layer  of  the  Graafian  follicle ;  and 
it  is  supported  in  its  place  by  the  Retinacula,  which  connect  its  Tunica 
Granulosa  with  the  Membrana  Granulosa  that  lines  the  ovisac.  (See  Fig.  6, 

ischiura,  and  behind  these  are  the  transversi-perinei  muscles.  They  are  surrounded  by  very 
loose  cellular  tissue.  They  are  rounded,  but  somewhat  elongated,  being  flat  and  bean- 
shaped.  Their  long  diameter  is  from  5  to  10  lines ;  their  transverse  diameter  2^  to  4£  lines, 
and  they  are  from  2j  to  3  lines  thick.  The  excretory  duct  is  at  the  anterior  edge  of  the 
superior  part  of  the  gland,  and  runs  beneath  the  constrictor  vaginae,  horizontally  forwards 
and  inwards,  to  the  inner  face  of  the  nympha,  opening  in  front  of  the  carunculae  myrtiformes, 
in  the  midst  of  a  number  of  small  mucous  follicles.  These  glands  were  first  discov^ed  by 
Duverney  in  the  cow,  about  the  middle  of  the  seventeenth  century.  Bartholinus  subse- 
quently found  them  in  the  human  female,  and  his  observations  were  confirmed  by  Duver- 
ney, Morgagni,  Santorini,  Peyer,  &c.  Haller  denied  their  existence;  and  such  structure 
seems  to  have  been  forgotten  until  they  were  again  described  by  Mr.  Taylor  (Dublin 
Journal,  vol.  xiii.  1838).  They  are  analogous  to  Cowper's  glands  in  the  male,  according  to 
Tiedemann,  and  like  them  are  sometimes  wanting,  and  differ  in  size.  In  advanced  age 
they  are  said  to  diminish  in  size,  and  even  disappear.  They  are  present  in  the  females  of 
all  animals,  where  Cowper's  glands  exist  in  the  males.  They  secrete  a  thick,  tenacious, 
grayish- white  fluid,  which  is  emitted  in  large  quantities,  at  the  termination  of  the  sexual  act, 
most  likely  from  the  spasmodic  contraction  of  the  constrictor  vagina?  muscle,  under  which 
they  lie.  Its  admixture  with  the  male  semen  is  supposed  to  probably  have  some  connection 
with  impregnation,  and  it  has  been  suggested  that  it  may  be  the  vehicle  of  the  fecundating 
principle  of  the  semen.  These  glands  were  probably  known  to  the  ancients,  and  it  is  doubt- 
less their  secretion  which  Hippocrates  and  others  describe  as  the  female  semen. — (1843.) 
These  glands  have  lately  been  described  by  Huguier  of  Paris,  in  the  Archives  d^natomie. 
His  description  corresponds  in  every  respect  with  that  given  above. — (1847.) — M.  C.] 
59 


698  OF  REPRODUCTION*. 

Plate  I.)  The  Ovum  then  begins  to  move  towards  the  periphery  of  the 
Graafian  follicle;  and  always  towards  that  point  of  it  which  is  nearest  the 
surface  of  the  Ovary.  This  movement  appears  to  be  due,  in  the  first  instance, 
to  the  shortening  of  the  Retinacula  in  that  direction ;  and  whilst  the  Ovum 
lies  against  the  membrane  of  the  Ovisac,  a  gradual  thinning  of  the  latter  seems 
to  take  place.  At  the  same  time  an  important  change  is  occurring  in  the  outer 
wall  of  the  Graafian  follicle,  especially  at  the  part  most  deeply  imbedded  in 
the  Ovary;  its  vascularity  is  greatly  increased,  and  its  substance  appears 
thickened.  This  thickening  is  probably  due  to  the  deposition  of  blood  in  a 
state  ready  to  become  more  highly  organized,  upon  the  exterior  of  the  Ovisac; 
and  the  consequence  of  it  is,  that  considerable  pressure  is  made  upon  the  con- 
tents of  the  follicle,  the  effect  of  which  is,  of  course,  exerted  most  upon  the 
thinnest  part  of  it.  Thus,  a  sort  of  vis  a  tergo  is  exercised  against  the  Ovum 
and  the  Disc  (consisting  of  the  tunica  granulosa  and  the  central  part  of  the 
retinacula)  in  which  it  is  imbedded ;  and  the  whole  is  forced,  by  the  rupture 
of  the  Graafian  follicle,  into  the  funnel-shaped  entrance  of  the  Fallopian  tube, 
— the  Retinacula  being  gradually  detached  from  the  Membrana  Granulosa, 
which  is  left  behind.  This  action  is  represented  in  Fig.  8,  Plate  I.  What 
becomes  of  the  Ovisac  is  not  certain.  Dr.  Barry  affirms  that  he  has  some- 
times known  it  to  be  subsequently  expelled  from  the  ovary ;  but  it  appears 
more  commonly  to  coalesce  with  the  surrounding  envelope,  and  to  constitute, 
together  with  it,  the  lining  of  the  cavity,  which  is  usually  found  in  the  Corpus 
Luteum.  The  substance  known  under  this  name  is  found  in  the  Ovary,  after 
the  Ovum  has  escaped  from  it ;  and  the  importance  of  the  question,  how  far 
its  presence  may  be  regarded  as  an  indication  that  Conception  has  taken 
place,  requires  that  we  should  have  clear  ideas  respecting  its  nature. 

913.  The  term  Corpus  Luteum  has  been  usually  applied  to  a  reddish-yel- 
low substance,  glandular  in  aspect,  friable  in  consistence,  and  very  vascular ; 
which  occupies  the  part  of  the  Ovary  from  which  the  germ  has  escaped,  and 
is  larger  or  smaller  according  to  the  length  of  time  that  has  elapsed  since  con- 
ception. At  first  it  is  usually  so  large  as  to  occasion  a  considerable  projection 
on  the  surface  of  the  Ovary ;  its  form  is  oval,  or  resembles  that  of  a  bean. 
When  cut  across,  its  dimensions  are  usually  found  to  be  from  4  to  5-8ths  of 
an  inch  in  its  long  diameter,  and  from  3  to  4-8ths  in  its  short ;  and  it  thus 
occupies  from  a  fourth  to  a  half  of  the  whole  area  of  the  ovarium ;  but  these 
dimensions  are  not  unfrequently  exceeded.  The  centre  of  this  substance  is 
hollow ;  and  by  a  proper  acquaintance  with  this  character,  the  true  Corpus 
Luteum  may  be  distinguished  from  substances,  bearing  a  general  resemblance 
to  it,  but  very  different  in  their  character.  The  following  is  Dr.  Mont- 
gomery's account  of  it.  "  Its  centre  exhibits  either  a  cavity,  or  a  radiated  or 
branching  white  line,  according  to  the  period  at  which  the  examination  is 
made.  If  within  the  first  three  or  four  months  after  conception,  we  shall,  I 
believe,  always  find  the  cavity  still  existing,  and  of  such  a  size  as  to  be  capable 
of  containing  a  grain  of  wheat  at  least,  and  very  often  of  much  greater  dimen- 
sions ;  this  cavity  is  surrounded  by  a  strong  white  cyst ;  and  as  gestation 
proceeds,  the  opposite  parts  of  this  cyst  approximate,  and  at  length  close  to- 
gether, by  which  the  cavity  is  completely  obliterated,  and  in  its  place  there 
remains  an  irregular  white  line,  whose  form  is  best  expressed  by  calling  it 
radiated  or  stelliform.  This  is  visible  as  long  as  any  distinct  trace  of  the 
Corpus  Luteum  remains."*  The  true  Corpus  Luteum  is  further  distinguished 
by  its  capability  of  being  injected  from  the  vessels  of  the  Ovary ;  which  is 
not  the  case  with  Tubercular  deposits,  or  other  substances  which  may  stimu- 
late it.  After  Delivery,  the  size  of  the  Corpus  Luteum  rapidly  diminishes ; 

*  Signs  of  Pregnancy,  p.  226. 


ACTION  OF  THE  FEMALE.  699 

and  in  a  few  months  it  ceases  to  be  recognizable  as  such.  The  cicatrix  by 
which  the  Ovum  has  escaped  is  visible  for  some  time  longer ;  but  this  too, 
according  to  the  careful  researches  of  Dr.  Montgomery,  cannot  be  distin- 
guished at  a  subsequent  period.  Hence  there  is  no  correspondence  between 
the  number  of  Corpora  Lutea  found  in  the  ovaries  of  a  woman,  or  of  Cica- 
trices on  their  surface,  and  the  number  of  children  she  may  have  borne.  The 
number  of  Corpora  Lutea  must  always  be  less,  when  there  have  been  many 
conceptions ;  but  the  number  of  Cicatrices  maybe  greater;  for  several  causes, 
such  as  the  escape  of  unimpregnated  ova,  or  the  bursting  of  little  abscesses, 
may  give  rise  to  such  appearances. 

914.  Much  discussion  has  taken  place  amongst  Embryologists,  as  to 
whether  the  substance  of  the  Corpus  Luteum  is  deposited  within  the  Graafian 
follicle,  externally  to  it,  or  between  its  layers.  The  first  is  the  opinion  of 
Baer,  Bischoff,  and  others;  who  regarded  it  as  a  growth  from  the  inner  layer 
of  the  Graafian  follicle.  The  second  is  the  opinion  of  Dr.  R.  Lee  and  Mr. 
Wharton  Jones.  The  third  is  the  doctrine  taught  by  Drs.  Montgomery  and 
Barry ;  the  former  regarding  it,  however,  as  deposited  between  the  two  layers, 
of  which  the  cellulo-vascular  layer  of  the  Graafian  follicle  (which  are  both 
derived  from  the  condensed  stroma  of  the  ovarium)  consist ;  whilst  the  latter 
maintains  that  the  deposit  takes  place  between  the  true  Ovisac  and  its  Ovarian 
envelopes.  The  recent  inquiries  of  Dr.  Ritchie*  throw  great  light  on  this 
question  ;  by  showing  that  a  great  variety  of  changes  may  take  place,  after  the 
discharge  of  the  Ovum  from  the  Ovisac ;  amongst  which  may  be  included  all 
the  appearances  described  by  the  several  writers  just  quoted.  The  following 
is  an  abstract  of  the  results  of  Dr.  R.'s  researches. 

a.  The  appearances  presented  by  the  Ovaries,  Graafian  follicles,  and  by  the  blood  which 
is  contained  in  the  latter  subsequent  to  their  rupture,  vary  according  to  the  time  at  which 
they  are  examined,  and  the  absorbing  power  of  the  individual. — In  cases  of  the  recent  dis- 
charge of  an  Ovum,  the  Peritoneal  coat  of  the  Ovaiy  is  marked  by  a  jagged  slit  or  opening, 
having  a  florid  vascular  areola ;  in  those  of  longer  standing,  the  opening  is  covered  over, — 
with  the  exception  of  a  minute  circular  foramen  in  the  centre,  (or  where  the  slit  has  been  of 
great  length)  of  two  such  openings, — with  new  tissue,  surrounded  by  a  claret-coloured  mar- 
gin ;  and  in  those  still  more  ancient,  ihe  whole  is  healed  up  into  a  cicatrix,  which  is  more 
or  less  superficial  and  free  from  discoloration,  according  to  its  age. 

b.  With  respect  to  the  Blood,  which  is  generally  contained  in  the  ruptured  follicles,  it  is 
seen  first  as  a  florid  coagulum ;  next,  having  only  its  centre  scarlet-coloured,  and  its  peri- 
phery more  or  less  black,  and  perhaps  furrowed ;  frequently  the  clot  has  a  gamboge  colour 
from  the  decomposition  of  its  red  corpuscles,  or  has  become  pale  from  their  absorption;  and 
lastly,  the  clot  is  found  in  different  stages  of  absorption.     But  it  sometimes  also  happens, — 
and  that  indifferently  in  every  variety  of  the  uterine  state, — that  the  ruptured  follicles  are 
found  empty,  or  containing  only  an  aqueous  fluid. 

c.  The  coats  of  the  ruptured  Follicles  have  been  found  in  four  different  general  condition?, 
apparently  dependent  on  their  relative  degree  of  organization ;  and  each  class  presenting, 
also,  modifications  of  their  respective  characteristics,  proceeding  in  part  from  the  same  cause, 
and  in  part  also  from  changes  connected  with  the  period  of  their  progress  in  which  they 
were  examined. 

i.  The  first  class  was  distinguished  by  the  attenuated  state  of  the  coats  of  the  ruptured 
Follicle;  and  by  the  total  absence  of  any  organic  changes  in  these,  different  from  their  con- 
dition previous  to  their  discharge.  The  only  alterations  observable  resulted  from  the  me- 
chanical dyeing  of  their  coats  of  an  inky-black,  or  of  a  yellow  colour,  proceeding  from  their 
contact  with  decomposed  blood. — The  first  class  of  appearance  was  found  indifferently  in 
all  ages  and  states,  subsequent  to  puberty. 

ir.  The  second  general  class  of  ruptured  Follicles  was  characterized,  in  addition  to  the 
appearances  just  described,  by  organic  changes  in  their  coats ;  consisting,  progressively,  of 
an  increased  vascularity,  a  thickening,  a  whitening  of  the  colour,  and  finally,  a  corrugation 
of  their  tissue.  The  white  bodies  thus  formed,  to  which  Dr.  R.  has  given  the  designation  of 
Corpora  Jllbida,  may  exist  under  two  distinct  forms: — 1.  As  soft  bodies  of  a  yellowish  fatty 
aspect,  having  the  outer  coat  much  thickened,  whilst  their  inner  remains  as  a  delicate  dia- 


Medical  Gazette,  1844. 


700  OF  REPRODUCTION. 

phanous  pellicle ;  these,  after  a  lengthened  period,  present  themselves  as  yellowish-white, 
and  generally  globular  bodies,  more  or  less  fissured  from  their  contraction,  and  sometimes  in 
process  of  absorption,  having  a  granular-looking  structure,  and  seldom  being  divisible  into 
laminae  by  simple  dissection: — and  2.  As  dense  bodies  of  a  whitish,  shining,  firm  structure, 
their  inner  coat  being  the  seat  of  these  changes,  and  their  outer  adhering  loosely  as  a 
transparent  peculiar  layer;  the  inner  layer  presents  itself  as  a  thick,  opaque,  deeply- 
wrinkled  or  corrugated,  and  rocky  cyst,  or  is  sometimes  partially  diaphanous,  and  of  a  shin- 
ing pearly  aspect,  and  very  white  colour;  and  it  sometimes  contains  a  yellow,  greenish, 
transparent  fluid,  or  a  clot  of  blood,  either  unchanged,  or  converted  into  a  yellow  or  black 
pigment.  This  second  variety  appears  to  be  the  Corpus  Luteum  of  Baer. — These  white 
bodies,  or  Corpora  Albida,  were  found  by  Dr.  R.  in  every  variety  of  uterine  condition,  subse- 
quent to  the  establishment  of  menstruation,  but  never  before  it ;  and  the  dense  kind,  espe- 
cially, were  persistent  for  a  long  period.  They  had  no  necessary  connection  with  the  gravid 
condition;  but  they  were  occasionally  (especially  the  dense  variety)  the  only  specialty  ob- 
servable in  the  ovaries  of  the  puerperal  female,  some  time  after  delivery. 

in.  The  third  class  was  characterized  by  the  presence  of  an  organized  yellow-coloured 
brain-like,  granular  matter ;  forming  bodies  to  which  Dr.  R.  has  given  the  name  of  Corpora 
Cephaloidea.  These  differed,  according  as  the  cerebriform  matter  was  deposited  between 
the  layers  of  ruptured  Follicles,  having  transparent  pellicular  walls,  as  in  Class  i.,  or  having 
either  their  inner  or  outer  coat  thickened,  as  in  Class  u. ; — or  according  as  the  cerebriform 
matter  was  deposited  externally  to  the  two  inner  layers  oflhe  Follicle. — The  former  of  those 
varieties  was  found  by  Dr.  Ritchie  in  menstruating  females ;  also  during  the  first  months  of 
the  gravid  state  ;  and  sometimes  even  in  the  period  of  lactation.  In  some  instances,  only 
one  or  two  of  the  cerebriform  bodies  were  found ;  but  in  others,  five  or  six.  Their  struc- 
ture, especially  in  the  more  perfectly-organized  specimens,  presented  a  striking  resemblance 
to  the  convoluted  reddish-yellow  surface  of  the  brain,  covered  by  its  inner  membranes,  and 
painted  with  its  scarlet-coloured  and  dark  vessels.  These  cephaloid  bodies  undergo  diminu- 
tion in  proportion  to  their  age,  and  the  absorbing  power  of  the  female.  In  those  possessed 
of  only  thin  coats,  or  having  the  outer  layer  as  the  seat  of  the  thickening,  the  inner  walls  of 
the  cysts  speedily  contracted  and  coalesced;  so  that  their  centres  exhibited  a  delicate  opaque 
streak:  or,  in  those  better  developed,  a  serrated,  curved,  and  well-marked  white  line,  ac- 
cording as  the  cyst  was  of  elliptical  or  of  a  globular  form.  This  variety  of  cerebriform  cyst 
was  met  with  in  a  recent  state  as  well  in  immediate  connection  with  the  existence  of  men- 
struation, as  during  the  first  seven  months  of  pregnancy ;  and  in  this  latter  case,  by  under- 
going a  conversion  in  its  form  presently  to  be  noticed  (iv),  they  constituted  the  Corpora 
Lutea  of  Dr.  Montgomery. — In  the  second  variety  of  Cephaloid  bodies,  the  two  inner  layers 
of  the  Graafian  Follicle  were  converted  into  a  dense  white  body,  surrounded  by  an  envelope 
of  yellow  matter.  Such  cysts  (the  Corpora  Lutea  of  Dr.  Lee)  were  never  observed  as  an 
effect  of  menstruation  simply,  but  were  met  with  exclusively  in  the  gravid  female ;  although 
two  were  seen  (as  were  also  the  cephaloid  bodies  of  the  preceding  order)  to  be  present  in 
some  cases  of  single  conception.  This  form  of  Cephaloid  bodies  was  generally  distinguished 
by  large,  persistent,  white,  glistening  cavities.  The  granular  cephaloid  matter  was  some- 
times found  quite  absorbed  within  a  few  days  after  parturition ;  but  in  other  instances  it 
underwent  the  metamorphosis  characteristic  of  the  next  class. 

iv.  The  fourth  general  state  of  the  ruptured  Graafian  follicle  was  peculiar  to  the  impreg- 
nated and  lactating  female,  in  the  period  between  the  8th  and  13th  months  after  concep- 
tion ;  and  appeared  to  be  a  conversion  of  the  Corpora  Cephaloidea  already  described,  arising 
out  of  a  higher  and  more  perfect  organization.  Down  to  the  7th  month  of  pregnancy,  the 
cysts  contained  in  the  Ovaries  did  not  differ  in  any  respect  from  the  cerebriform  bodies 
found  in  the  unimpregnated  state;  except  that  they  were  sometimes  plumper,  more  vascu- 
lar, better  developed,  and  had  their  inner  layer  more  frequently  thickened.  A  change  in 
the  hue  of  the  granular  matter  then  commences,  which  becomes  more  decided  as  time 
elapses;  so  that  by  the  end  of  the  1st  month  after  delivery,  it  becomes  of  a  decided  rose 
colour,  changing  to  a  still  more  florid  hue  on  exposure  to  air.  Its  cavity  also  contracts,  so  as 
to  leave  but  a  stellated  point,  or  a  curved  groove :  and  a  fibrous  appearance  (probably  de- 
pendent on  the  traction  thus  exercised)  is  seen  in  the  surrounding  substance.  Although 
these  bodies,  termed  by  Dr.  Ritchie  Corpora  rubra,  are  found  exclusively  in  the  later  months 
of  pregnancy,  or  in  the  puerperal  state,  yet  they  are  not  always  present  in  those  conditions. 

The  number  of  cases  examined  by  Dr.  Ritchie  is  not,  perhaps,  sufficient  to 
enable  us  to  found  any  positive  statements  upon  the  results  of  his  examina- 
tion of  them  ;  but  the  following  inductions  appear  highly  probable  : — 1.  That 
the  presence  of  Corpora  Rubra  may  be  regarded  as  indicative,  not  only  of 
conception,  but  also  of  an  advanced  state  of  pregnancy,  or  of  recent  delivery; 
but  that  their  absence  is  not  to  be  regarded  as  any  proof  to  the  contrary. — 2. 


ACTION  OF  THE  FEMALE.  701 

That  the  presence  of  Corpora  Cephaloidea  of  the  second  order  is  to  be  re- 
garded as  indicative  of  conception. — 3.  That  the  presence  of  the  Corpora 
Cephaloidea  of  the  first  order,  or  of  Corpora  Jllbida,  cannot  be  regarded  as 
in  the  least  degree  indicative  of  Conception  ;  as  they  may  result  from  the 
simple  discharge  of  an  Ovum,  in  the  ordinary  course  of  those  changes  to 
which  the  Ovarium  is  subject. — The  excess  of  Corpora  Albida  above  every 
other  appearance  is  due,  not  merely  to  their  being  an  ordinary  result  of  the 
discharge  of  unimpregnated  Ova ;  but  also  to  the  frequency  of  their  produc- 
tion as  degenerated  forms  (so  to  speak)  of  the  Corpora  Cephaloidea  and  Cor- 
pora Rubra  of  the  gravid  female  ;  and  also  to  their  occasional  existence  as, 
from  the  first,  the  only  Ovarian  change  following  upon  Conception. 

915.  The  object  of  the  changes  which  have  been  already  described,  is  to 
bring  the  Ovum  within  reach  of  the  fecundating  influence ;  and  to  convey  it 
into  the  Uterus  after  it  has  been  fertilized.     We  have  now  to  consider  the 
changes  in  the  Ovum  itself,  which  take  place  during  the  same  epoch.     At 
about  the  same  period  that  the  Ovum  moves  towards  the  periphery  of  the 
Graafian  follicle,  the  Germinal  Vesicle  moves  towards  the  periphery  of  the 
yolk-bag ;  and  it  always  takes  up  its  position  at  the  precise  point  of  the  Zona 
Pellucida  which  is  nearest  the  Ovisac,  and  which  is  closest,  therefore,  to  the 
surface  of  the  Ovary.     Moreover,  the  Germinal  Spot  is  always  on  that  part 
of  the  Germinal  Vesicle,  which  is  in  closest  contact  with  the  Zona  Pellucida. 
(See  a,  Figs.  9  and  10,  Plate  I.)     Thus,  the  Germinal  Spot  is  very  near  the 
exterior  of  the  Ovary;  but  is  separated  from  it  by  the  peritoneal  coat  of  the 
latter,  by  a  thin  layer  of  its  stroma  forming  the  external  layer  of  the  Graafian 
follicle,  by  the  ovisac  forming  its  internal  membrane,  and  by  the  zona  pellu- 
cida.     We  have  already  seen  how  the  obstacle  interposed  by  the  three  former 
to  the  entrance  of  the  Spermatozoon,  is  overcome ;  we  shall  presently  find 
that  the  Zona  Pellucida  undergoes  a  similar  change. 

916.  Whilst  the  Ovum  is  being  prepared  for  fecundation,  a  series  of  very 
important  actions  takes  place  in  the  Germinal  Vesicle.     The  exterior  or  peri- 
pheral portion  of  the  Spot,  which  previously  consisted  of  a  collection  of  very 
minute  granules,  begins  to  develope  itself  into  a  ring  of  new  cells  of  extreme 
delicacy  (Fig.  9,  «) ;   these  gradually  enlarge,  and  a  second  ring  of  cells  is 
developed  within  it,  pushing  the  first-formed  cells  further  away  from  the  cen- 
tre.    Many  successive  rings  of  cells  are  thus  formed  ;  and  at  last  the  whole 
Germinal  Vesicle  is  filled  with  them,  as  shown  at  6,  Fig.  10.     Still  there 
remains  a  pellucid  space  in  the  centre  of  the  Germinal  Spot  (resembling  that 
seen  at  a,  Fig.  12) ;  in  which  no  cells  are  developed.     The  first-formed  cells 
that  have  been  pushed  outwards,  are  so  much  compressed  by  those  subse- 
quently formed,  as  frequently  to  undergo  liquefaction  ;  and  during  the  time 
that  the  Ova  are  being  matured  for  fertilization,  there  is  a  continual  new  pro- 
duction of  cells  at  the  centre,  and  a  degeneration  at  the  circumference. — At 
the  same  time,  the  Yolk   undergoes  changes    somewhat  analogous ;   for  it 
ceases  to  contain  separate  oil-globules ;  and  large  elliptical  discs  or  cells  are 
seen  in  it,  especially  just  beneath  the  Zona  Pellucida  (Fig.  9,  c).*     Here,  too, 
the  formation  of  new  cells  takes  place  from  the  periphery  towards  the  centre  ; 
the  peripheral  ones  gradually  undergo  liquefaction,  as  is  seen  in  the  outer 
layer  of  those  in  Fig.  10,  which  are  becoming  indistinct;  and  they  are  replaced 
by  a  new  layer  pushed  outwards  from  the  centre.     The  same  process  sub- 
sequently continues  in  the  Yolk,  for  some  time  after  fecundation ;  and  this 
not  only  in  regard  to  the  yolk  as  a  whole,  but  in  respect  to  its  individual  cells, 

*  It  is  to  be  remembered  that  the  observations  of  Dr.  Barry,  here  quoted,  were  made  on 
the  Rabbit :  and  are,  therefore,  probably  applicable  equally  to  other  Mammalia,  but  not  to 
Oviparous  Animals. 

59* 


702  OF  REPRODUCTION. 

as  is  shown  in  Fig.  1 1 ,  where  concentric  rings  of  new  cells  are  seen  in  each 
of  the  parent  vesicles.  Even  in  the  most  advanced  of  these  secondary  cells, 
another  generation  may  be  seen,  and  these  are  developed  upon  the  same  plan 
with  those  of  the  Germinal  Vesicle :  thus  in  Fig.  12,  the  pellucid  centre  of 
the  original  nucleus  of  the  parent  disc  is  seen  at  «,  and  is  surrounded  by  seve- 
ral concentric  rings  of  cells,  increasing  in  size  from  within  outwards  ;  and  at 
b  is  represented  the  condition  of  the  outer  and  older  cells,  in  which  the  same 
process  is  undergoing  repetition.  (Although  the  figure  only  represents  one 
secondary  cell  as  in  the  act  of  producing  others,  the  others  of  the  same  age 
are  alike  engaged  in  the  process  of  multiplication.) — The  foregoing  history  is 
equally  applicable  to  the  cells,  from  which  the  Embryo  subsequently  origi- 
nates ;  and  it  is  probably  the  general  mode  in  which  the  process  takes  place. 

917.  At  the  time  when  the  interior  of  the  Germinal  Vesicle  is  being  pre- 
pared for  the  reception  of  the  fecundating  influence,  the  portion  of  the  Zona 
Pellucida  against  which  it  lies  becomes  attenuated;  and  a  chink  then  forms  in 
it,  just  above  what  was  the  pellucid  centre  of  the  Germinal  Spot.     Through 
this  chink,  the  Spermatozoon  can  reach  the  Germinal  Vesicle;  and  that  it  does 
so,  we  are  now  entitled  to  affirm,  not  only  from  analogy,  but  also  from  actual 
observation  (§  900).     What  is  the  nature  of  the  influence  communicated  by  it 
is  less  certain;  but  from  the  known  character  of  the  process  of  fecundation  in 
Plants,  we  shall  have  little  difficulty  in  concluding,  that  it  deposits  in  the 
Germinal  Vesicle  the  rudiments  of  the  first  cells,  which  are  subsequently  to 
be  developed  into  the   Embryonic  structure.     It  is  certain  that  none  of  the 
cells  previously  contained  in  the  Germinal  Vesicle  subsequently  form  part  of 
it ;  in  fact,  they  all  liquefy  after  a  time,  and  disappear  entirely.     But  in  the 
previously  pellucid  centre  of  what  was  the  Germinal  Spot,  two  new  cells  are 
seen  after  fecundation;  these  enlarge  at  the  expense  of  the  rest;  and  from 
them,  all  the  permanent  structures  originate.     This  pair  of  cells  is  seen  at  «, 
Figs.  13  and  14;  in  the  former  some  of  the  cells  of  the  Germinal  Vesicle  are 
still  left ;  in  the  latter,  they  have  been  all  absorbed.     The  Germinal  Vesicle 
returns  after  fecundation  to  the  centre  of  the  Yolk,  being  at  first  entirely  con- 
cealed by  its  discs  (Fig.  11);  and  the  cleft  in  the  Zona  Pellucida  soon  closes, 
so  as  to  be  no  longer  distinguishable.     The  two  new  cells  and  the  other  con- 
tents of  the  Germinal  Vesicle,  undergo  such  a  rapid  increase  in  size,  that  they 
soon  fill  the  whole  interior  of  the  Zona  Pellucida ;  and  the  cells  of  the  Yolk 
being  reduced  by  the  pressure  into  a  liquid  form,  their  elements  are  absorbed 
by  the  new  cells  of  the  Embryonic  structure.     This,  at  least,  is  the  case  in 
the  Mammalia ;  among  which  the  Yolk  performs  but  a  very  subordinate  part, 
having  only  to  serve  for  the  development  of  the  Embryo  during  a  very  brief 
period.— In  each  of  the  two  primary  Germ-cells  (as  they  may  be  called)  a 
series  of  changes  takes  place,  exactly  conformable  to  that  already  described  as 
occurring  in  the  Germinal  Vesicle  ; — that  is  to  say, — a  ring  of  new  cells  origi- 
nates in  the  margin  of  its  nucleus, — this  increases  in  size,  and  is  pushed  out- 
wards by  another  ring  nearer  the  centre,  this  again  by  another,  and  so  on, — 
and  at  last,  two  cells  appear  in  the  pellucid  central  space,  which  are  developed 
at  the  expense  of  all  the  rest,  and  are  to  be  regarded  as  the  real  permanent 
offspring  of  the  parent.     These  changes  may  be  seen  in  progress  in  Figs.  13 
and  14;  in  the  former,  the  original  cells  of  the  Germinal  Vesicle  have  not 
quite  disappeared,  although  their  liquefaction  is  in  progress ;  in  the  latter,  no 
vestige  of  them  is  left,  the  whole  cavity  being  occupied  by  the  twin-cells. 

918.  These  changes  commence  during  the  passage  of  the  Ovum  along  the 
Fallopian  tube  ;  and  during  its  transit  to  the  Uterus,  it  acquires  a  sort  of  gela- 
tinous envelope,  which  is  inclosed  in  a  membrane  of  fibrous  texture,  termed 
the  Chorion.     The  gelatinous  envelope  is  probably  of  an  albuminous  nature 
in  reality,  corresponding  with  the  white  of  the  Bird's  egg ;  whilst  the  fibrous 


ACTION  OF  THE  FEMALE.  703 

texture  of  Chorion  seems  to  be  produced,  like  the  membranous  basis  of  the 
egg-shell  of  the  Bird  (§  118),  by  the  exudation  of  Fibrine  from  the  lining 
membrane  of  the  Fallopian  tube  or  Oviduct.  The  outer  layer  of  this  en- 
velope, in  the  egg  of  the  Bird,  is  consolidated  by  the  deposition  of  particles  of 
Carbonate  of  Lime  in  its  areolae ;  but  it  undergoes  no  higher  organization. 
The  Chorion  of  the  Mammal,  on  the  other  hand,  subsequently  undergoes 
changes  of  a  much  higher  order;  which  adapt  it  for  participating,  to  a  most 
important  degree,  in  the  nutrition,  of  the  included  embryo. — The  first  of  these 
changes  consists  in  the  extension  of  the  surface  of  the  membrane  into  a  num- 
ber of  villous  prolongations,  which  give  it  a  spongy  or  shaggy  appearance. 
These  serve  as  absorbing  radicles,  and  form  the  channel  through  which  the 
embryo  is  nourished  by  the  fluids  of  the  parent,  until  a  more  perfect  commu- 
nication is  formed,  in  the  manner  to  be  presently  explained. 

919.  We  have  now  to  speak  of  the  changes  in  the  Uterus,  which  take 
place  in  consequence  of  Conception,  and  which  prepare  it  to  receive  the 
Ovum.  Of  these  the  most  important  is  the  formation  of  the  Membrana  De~ 
cidua,  so  called  from  its  being  cast  off  at  each  parturition.  This  membrane 
has  been  usually  supposed  to  be  a  new  formation ;  and  has  been  described  as 
originating  in  coagulable  lymph  thrown  out  on  the  inner  surface  of  the  Uterus, 
into  which  vessels  ^are  prolonged  from  the  subjacent  surface.  It  appears, 
however,  from  the  late  researches  of  Dr.  Sharpey  and  Prof.  Weber,*  that  this 
is  not  the  true  account  of  it;  and  that  the  Decidua  is  really  composed  of  the 
inner  portion  of  the  Mucous  membrane  itself,  which  undergoes  a  considerable 
change  in  its  character.  The  Mucous  membrane  of  the  Uterus  had  been  ob- 
served by  Dr.  J.  Reid  to  possess,  on  its  free  surface,  a  tubular  structure ;  not 
very  unlike  that  which  has  been  described  as  existing  in  the  lining  membrane 
of  the  stomach  (§  873  and  Fig.  269).  This  tubular  portion  becomes  thickened 
and  increased  in  vascularity,  within  a  short  time  after  conception ;  and  when 
the  inner  surface  of  a  newly-impregnated  Uterus  is  examined  with  a  low 
magnifying  power,  the  orifices  of  its  tubes  (Plate  I.,  Fig.  17,  b,b)  are  very 
distinctly  seen,  being  lined  with  a  white  epithelium.  The  blood-vessels  (c,  c) 
form  a  very  minute  net-work,  which  extends  in  loops  from  the  subjacent 
portion  of  the  membrane.  According  to  the  recent  observations  of  Mr.  J. 
Goodsir,t  the  interfollicular  spaces  («,  «, «)  also  are  crowded  with  nucleated 
particles  ;  and  it  is  to  the  development  of  this  interfollicular  substance,  as  well 
as  to  the  enlargement  of  the  follicles  themselves,  and  the  copious  development 
of  epithelial  cells  in  their  interior,  that  the  mucous  membrane  in  this  condition 
owes  its  increased  thickness.  At  a  later  period,  the  Decidua  may  be  found 
to  consist  of  two  distinct  layers;  the  Decidua  vera,  lining  the  uterus;  and  the 
Decidua  reflexa,  covering  the  exterior  of  the  ovum.  It  was  formerly  supposed 
that  the  latter  is  a  portion  of  the  former,  which  has  been  pushed  before  the 
ovum  at  its  entrance  into  the  uterus ;  but  the  two  layers  are  so  different  in 
texture,  that  they  cannot  be  supposed  to  have  the  same  origin.  The  difficulty 
appears  to  be  solved  by  the  observations  of  Mr.  Goodsir.  "  From  what  has 
now  been  stated,"  he  remarks,  "  it  appears  that  the  Decidua  consists  of  two 
distinct  elements;  the  mucous  membrane  of  the  uterus,  thickened  by  a  pecu- 
liar development ;  and  a  non-vascular  cellular  substance,  the  product  of  the 
uterine  follicles.  The  former  constitutes,  at  a  later  period,  the  greater  part  of 
the  decidua  vera ;  the  latter,  the  decidua  reflefta.  This  view  of  the  consti- 
tution of  the  Decidua  clears  up  the  doubts  which  were  entertained  regarding 
the  arrangement  of  these  membranes  at  the  os  uteri  and  entrances  of  the  Fallo- 
pian tubes.  It  is  evident  that  these  orifices  will  be  open  or  closed,  just  as  the 

*  Mullet's  Physiology,  pp.  1574-1580. 

f  Anatomical  and  Pathological  Observations,  Chap.  ix. 


704  OF  REPRODUCTION. 

cellular  secretion  is  more  or  less  plentiful,  or  in  a  state  of  more  or  less  vigor- 
ous development."—"  When  the  ovum  enters  the  cavity  of  the  uterus,  the 
cellular  decidua  surrounds  it,  and  becomes  what  has  been  named  the  decidua 
reflexa,  by  a  continuation  of  the  same  action,  by  which  it  had  been  increasing 
in  quantity  before  the  arrival  of  the  ovum.  The  cellular  decidua  grows  around 
the  ovum  by  the  formation  of  new  cells,  the  product  of  those  in  whose  vicinity 
the  ovum  happens  to  be  situated." 

920.  When  the  Ovum  has  arrived  in  the  Uterus,  therefore,  and  the  villous 
tufts  of  the  Chorion  are  developed,  these  come  into  contact,  in  the  first  in- 
stance, with  the  layer  of  cellular  decidua,  which  intervenes  between  them 
and  the  vascular  decidua.     Through  this  cellular  membrane,  therefore,  the 
ovum  must  derive  its  nutriment  from  the  vascular  surface;    and  it  cannot.be 
deemed  improbable,  that  the  office  of  its  component  cells  is  to  draw  from  the 
subjacent  vessels  the  materials  which  are  to  serve  for  the  nutrition  of  the 
ovum,  and  to  present  it  to  the  villous  tufts  of  the  chorion.     Each  of  these  is 
composed  (according  to  the  observations  of  Mr.  J.  Goodsir)  of  an  assemblage 
of  nucleated  cells,  which  are  found  in  various  stages  of  development ;  and 
these   are    always   inclosed  within   a  layer  of  basement-membrane,  which 
seems  to  be  itself  composed  of  flattened  cells  united  by  their  edges.     At  the 
free  extremity  of  each  villus,  is   a  bulbous  expansion,  the  cells  composing 
which  are  arranged  round  a  central  spot ;  and  it  is  at  this  point  that  the  most 
active  processes  of  growth  take  place,  the  villus  elongating  by  the  develop- 
ment of  new  cells  from  its  germinal  spot,  and  (like  the  spongiole  of  the  plant) 
drawing  in  nutriment  from  the  soil  in  which  it  is  imbedded. — In  its  earliest 
grade  of  development,  the  chorion  and  its  villi  contain  no  vessels;  and  the 
fluid  drawn  in  by  the  tufts  is  communicated  to  the  embryo,  by  the  absorbing 
powers  of  the  germinal  membrane  of  the  latter.     But  when  the  tufts  are  pe- 
netrated by  blood-vessels,  and  their  communication  with  the  embryo  becomes 
more  direct,  the  means  by  which  they  communicate  with  the  parent  are  found 
to  be  still  essentially  the  same ; — namely,  a  double  layer  of  nucleated  cells, 
one  layer  belonging  to  the  foetal  tuft,  an'd  the  other  to  the  vascular  maternal 
surface.    It  is  from  these  elements  that  the  Placenta  is  formed,  in  the  manner 
next  to  be  described. 

921.  The  first  stage  in  this  process  consists  in  the  extension  of  the  foetal 
vessels  into  the  villi  of  the  Chorion  over  its  entire  surface,  in  the  manner  here- 
after to  be  detailed  (§  941) ;  so  that  the  nutriment  which   these  villi  imbibe, 
instead  of  being  merely  added  tb  the  albuminous  fluid  surrounding  the  yolk- 
bag,  is  now  conveyed  directly  to  the  embryo.  This, — the  earliest  and  simplest 
mode  by  which  the  Fretus  effects  a  new  connection  with  the  parent, — is  the 
only  one  in  which  it  ever  takes  place  in  the  lower  Mammalia,  which  are  hence 
properly  designated  as  "  non-placental,"  rather  than  as  ovo-viviparous  (§  44). 
In  the  higher  Mammalia,  however,  there  soon  occurs  a  great  extension  of  the 
vascular  tufts  of  the   fetal  Chorion,  at  certain  points ;  and  a  corresponding 
adaptation,  on  the  part  of  the  Uterine  structure,  to  afford  them  an  increased 
supply  of  nutritious  fluid.     These  specially-prolonged  portions  are  scattered, 
in  the  Ruminantia  and  some  other  Mammalia,  over  the  whole  surface  of  the 
Chorion,  forming  what  are  termed  the  Cotyledons  ;  but  in  the  higher  orders, 
and  in  Man,  they  are  concentrated  in  one  spot,  forming  the  Placenta.     In 
some  of  the  lower  tribes,  the  maternal  and  the  fetal  portions  of  the  Placenta 
may  be  very  easily  separated ;  the  former  consisting  of  the  thickened  Decidua; 
and  the  latter  being  composed  of  the  prolonged  and  ramifying  vascular  tufts 
of  the  Chorion,  dipping  down  into  it.     But  in  the  Human  Placenta,  the  two 
elements  are  mingled  together  through  its  whole  substance. 

922.  On  looking  at  the  Foetal  surface  of  the  Human  Placenta,  we  perceive 
that  the  umbilical  vessels  diverge  in  every  direction  from  the  point  at  which 


ACTION  OF  THE  FEMALE. 


705 


they  enter  it;  and  their  subdivisions  ramify  very  minutely,  forming  a  large 
part  of  its  substance.  The  terminal  ramifications  are  represented  by  Dr.  J. 
Reid*  as  having  the  digitated  aspect  represented  in  Fig.  23,  (Plate  I.) ;  but 
this  is  one  of  the  more  complex  forms.  In  its  simplest  character,  each 
villus  is  cylindrical  or  nearly  so ;  and  the  digitated  villi  are  only  solitary  villi 
grouped  together  at  the  extremity  of  a  primary  branch.  Each  villus  contains 
a  capillary  vessel,  which  forms  a  series  of  loops,  communicating  with  an 
artery  on  one  side  and  with  a  vein  on  the  other;  but  the  same  capillary  may 
pass  into  several  villi,  before  re-entering  a  larger  vessel.  The  vessels  of  the 
villi  are  covered,  as  in  the  Chorion,  by  a  layer  of  cells  (Fig.  280/),  inclosed 


Fig.  280. 


Fig.  281. 


Extremity  of  a  placental  villus  :— o,  exter-  Portion  of  the  external  membrane, 

nal  membrane  of  the  villus,  continuous  with  with  the  external  cells,  of  a  placental 

the  lining  membrane  of  the  vascular  system  villus:— a.  cells  seen  through  the  mem- 

of  the  mother ;  6,  external  cells  of  the  villus,  brane ;  b,  cells  seen  from  within  the 

belonging  to  the  placental  decidua ;  c,  c,  ger-  villus ;  e,  cells  seen  in  profile  along  the 

minal  centres  of  the  external  cells ;  d,  the  edge  of  the  villus. 

space  between  the  maternal  and  foetal  por- 
tions of  the  villus;  e,  the  internal  membrane  of 
the  villus,  continuous  with  the  external  mem- 
braneofthe  chorion;/, the  internal  cellsof  the 
villus,  belonging  to  the  chorion ;  g,  the  loop  of 
umbilical  vessels. 

in  basement-membrane  (e) ;  but  the  foetal  tuft  thus  formed  is  inclosed  in  a  se- 
cond series  of  envelopes  (a,  6,  c),  derived  from  the  maternal  portion  of  the 
Placenta, — a  space  (d)  being  left,  however,  between  the  two,  at  the  extremity 
of  the  tuft. 

923.  Whilst  the  foetal  portion  of  the  Placenta  is  thus  being  generated  by 
the  extension  of  the  vascular  tufts  of  the  Chorion,  the  Maternal  portion  is 
formed  by  the  enlargement  of  the  vessels  of  the  decidua,  between  which  they 
dip  down.  "  These  vessels  assume  the  character  of  sinuses  ;  and  at  last  swell 
out  (so  to  speak)  around  and  between  the  villi ;  so  that  finally  the  villi  are 
completely  bound  up  or  covered  by  the  membrane  which  constitutes  the  walls 
of  the  vessels,  this  membrane  following  the  contour  of  all  the  villi,  and  even 
passing  to  a  certain  extent  over  the  branches  and  stems  of  the  tufts.  Between 
this  membrane,  or  wall  of  the  enlarged  decidual  vessels,  and  the  internal  mem- 
brane of  the  villi,  there  still  remains  a  layer  of  the  cells  of  the  decidua."t  In 
this  manner  is  formed  the  Maternal  portion  of  the  Placenta,  which  may  be  re- 
garded in  its  adult  state  (as  was  well  pointed  out  by  Dr.  J.  Reid)  in  the  light 
of  a  large  sac  formed  by  a  prolongation  of  the  inner  coat  of  the  Uterine  vessels  ; 
against  the  foetal  surface  of  which  sac,  the  tufts  just  described  may  be  said  to 
push  themselves,  so  as  to  dip  down  into  it,  carrying  before  them  a  portion  of 
its  thin  wall,  which  constitutes  a  sheath  to  each  tuft.  Now  as  every  extension 


*  Edinb.  Med.  and  Surg.  Journal,  Jan.  1841. 

j-  Goodsir's  Anatomical  and  Pathological  Observations,  p.  60. 


706 


OF  REPRODUCTION. 


of  the  uterine  vessels  carries  the  decidua  before  it,  every  one  of  the  vascular 
tufts  that  dips  down  into  it  will  be  covered  with  a  layer  of  the  cellular  struc- 
ture of  the  latter ;  and  the  foetal  portion  of  each  tuft  will  thus  be  inclosed  in  a 
layer  of  maternal  cells  and  basement-membrane  (Fig.  280,  «,  6,  c;  and  Fig. 

281,  «,  6,  e).     In  this  manner,  the  whole  interior  of  the  placenta!  cavity  is  in- 
tersected by  numerous  tufts  of  foetal  vessels,  disposed  in  fringes,  and  bound 
down  by  reflections  of  the  delicate  membrane  that  forms  its  proper  wall ;  just 
as  the  intestines  are  held  in  their  places  by  reflections  of  the  peritoneum  that 
covers  them.     This  view  was  suggested  to  Dr.  R.  by  the  very  interesting  fact, 
that  the  tufts  of  fcetal  vessels  not  unfrequently  extend  beyond  the  uterine  sur- 
face of  the  Placenta,  and  dip  down  into  the  uterine  sinuses ;  where  they  are 
still  covered,  and  held  in  their  places,  by  reflections  of  the  same  membrane 
(Plate  I.,  Fig.  24).     All  the  bands  which  connect  and  tie  down  the  tufts  (Fig. 

282,  g-),  are  formed  of  the  same  elements  as  the  envelopes  of  the  tufts  them- 
selves ;  namely,  a  fold  of  the  lining  membrane  of  the  decidual  sinuses,  and  a 
layer  of  the  cellular  decidua. 

Fig.  282. 


Diagram  illustrating  the  arrangement  of  the  placental  decidua :— a,  decidua  in  contact  with  the  interior 
of  the  uterus ;  6,  venous  sinus  passing  obliquely  through  it  by  a  valvular  opening ;  c,  a  curling  artery 
passing  in  the  same  direction ;  d,  the  lining  membrane  of  the  maternal  vascular  system,  passing  in  from 
the  artery  and  vein,  lining  the  bag  of  the  placenta,  and  covering  e,  e,  the  fcetal  tufts,  passing  on  to  them 
from  their  stems  from  the  festal  side  of  the  cavity,  also  by  the  terminal  decidual  bars/./,  from  the  uterine 
side,  and  from  one  tuft  to  the  other  by  the  lateral  bar,  g  ;  h,  h,  separated  fcetal  tufts,  showing  the  internal 
membrane  and  cells,  which,  with  the  loops  of  umbilical  vessels,  constitute  the  true  fcetal  portion  of  the 
tufts. 

924.  The  blood  is  conveyed  into  the  Placental  cavity  by  the  "curling 
arteries"  of  the  Uterus ;  and  is  returned  from  it  by  the  large  veins,  that  are 
commonly  designated  as  sinuses.  The  fcetal  vessels,  being  bathed  in.  this 
blood,  as  the  branchiae  of  aquatic  animals  are  in  the  water  that  surrounds  them, 
not  only  enable  the  fetal  blood  to  exchange  its  venous  character  for  the  arte- 
rial, by  parting  with  its  carbonic  acid  to  the  maternal  blood,  and  receiving 
oxygen  from  it ;  but  they  also  serve  as  rootlets,  by  which  certain  nutritious 
elements  of  the  maternal  blood  (probably  those  composing  the  liquor  sanguinis) 
are  taken  into  the  system  of  the  Foetus.  In  this  they  closely  correspond  with 
the  villi  of  the  Intestinal  canal;  and  there  is  this  further  very  striking  analogy, 

that  the  nutrient  material  is  selected  and  prepared  by  two  sets  of  cells,  one 

of  which  (the  maternal)  transmits  it  to 'the  other  (the  foetal),  in  the  same  man- 
ner as  the  epithelial  cells  of  the  intestinal  villi  seem  to  take  up  and  prepare 
the  nutrient  matter,  which  is  destined  to  be  still  further  assimilated  by  the 
special  absorbing  cells  of  their  interior  (§  672).  There  is  no  more  direct 
communication  between  the  Mother  and  Foetus  than  this;  all  the  observations 
which  have  been  supposed  to  prove  the  existence  of  real  vascular  continuity, 


ACTION  OF  THE  FEMALE.  707 

having  been  falsified  by  the  extravasation  of  fluid,  consequent  upon  the  force 
used  in  injecting  the  vessels.  Moreover,  the  different  size  of  the  blood-corpus- 
cles in  the  Foetus  and  in  the  Parent  (§  149)  shows  the  non-existence  of  any 
such  communication. 

925.  The  formation  of  the  Placenta,  in  the  manner  just  described,  com- 
mences in  the  latter  part  of  the  second  month ;  during  the  third,  it  acquires 
its  proper  character;  and  it  subsequently  goes  on  'increasing,  in  accordance 
with  the  growth  of  the  ovum.  Towards  the  end  of  the  term  of  gestation, 
however,  it  becomes  more  dense  and  less  vascular ;  owing,  it  would  seem,  to 
the  obliteration  of  several  of  the  minuter  vessels,  which  are  converted  into 
hard  fibrous  filaments.  The  vessels  of  the  Uterus  undergo  great  enlargement 
throughout,  but  especially  at  the  part  to  which  the  Placenta  is  attached ;  and 
the  blood  in  moving  through  them  produces  a  peculiar  murmur,  which  is 
usually  distinctly  audible  at  an  early  period  of  Pregnancy,  and  may  be  regarded 
(when  due  care  is  taken  to  avoid  sources  of  fallacy),  as  one  of  its  most  unequi- 
vocal positive  signs.  The  Placental  bruit  is  thus  described  by  Dr.  Mont- 
gomery.* "  The  characters  of  this  phenomenon  are,  a  low  murmuring  or 
somewhat  cooing  sound,  resembling  that  made  by  bio  wing- gently  over  the  lip 
of  a  wide-mouthed  phial,  and  accompanied  by  a  slight  rushing  noise,  but  with- 
out any  sensation  of  impulse.  The  sound  is,  in  its  return,  exactly  synchronous 
with  the  pulse  of  the  mother  at  the  time  of  examination ;  and  varies  in  the 
frequency  of  its  repetitions,  with  any  accidental  variation  which  may  occur 
in  the  maternal  circulation.  Its  situation  does  not  vary  during  the  course  of 
the  same  pregnancy;  but  in  whatever  region  of  the  uterus  it  is  first  heard,  it 
will  in  future  be  found,  if  recognized  at  all, — for  it  is  liable  to  intermissions, — 
at  least  we  shall  occasionally  be  unable  to  hear  it  where  we  have  already 
heard  it  a  short  time  before,  and  where  we  shall  shortly  again  recognize  it. 
According  to  my  experience,  it  will  be  most  frequently  heard  about  the  situa- 
tion of  the  Fallopian  tube  of  the  right  side;  but  it  may  be  detected  in  any  of 
the  lateral  or  anterior  parts  of  the  uterus."  That  the  cause  of  this,  sound 
exists  in  the  Uterus  itself,  is  distinctly  proved  by  the  fact,  that  it  has  been 
heard  when  that  organ  was  so  completely  anteverted,  that  the  fundus  hung 
down  between  the  patient's  thighs.  A  sound  so  much  resembling  this,  as  to 
be  scarcely  distinguishable  from  it,  may  be  occasioned,  however,  by  a  cause 
of  a  very  different  nature, — namely,  an  abdominal  tumour,  pressing  upon  the 
aorta,  iliac  arteries,  or  enlarged  vessels  of  its  own;  and,  in  doubtful  cases,  it 
is  necessary  to  give  full  weight  to  the  possibility  of  such  an  explanation.  The 
sound  may  be  imitated  at  any  time,  by  pressing  the  stethoscope  on  the  iliac 
arteries.  The  Placental  bruit  has  been  not  unfrequently  heard  in  the  llth 
week ;  but  it  cannot  generally  be  detected  before  the  fourth  month,  when  the 
fundus  uteri  rises  above  the  anterior  wall  of  the  pelvis. 

92B.  The  amount  of  the  peculiar  tissue  of  the  Uterus  (§  234)  greatly 
increases  during  pregnancy.  At  the  same  time,  the  Mammary  gland  and  its 
appendages  undergo  a  fuller  development;  and  from  this  a  valuable,  but  not 
unequivocal,  indication  of  pregnancy  may  be  drawn.  Occasional  shooting 
pains  in  the  Mammae  are  not  unfrequently  experienced  within  a  short  period 
after  conception  ;  and  more  continued  tenderness  is  also  not  unusual.  A  sense 
of  distension  is  very  commonly  experienced  at  about  the  end  of  the  second 
month ;  and  from  that  time  a  distinct  "  knottiness"  usually  begins  to  present 
itself,  increasing  with  the  advance  of  Pregnancy.  In  many  instances,  how- 
ever, these  mammary  sympathies  are  entirely  absent;  and  they  may  be  simu- 
lated by  changes  that  take  place  in  consequence  of  various  affections  of  the 
Uterus.  A  change  of  colour  in  the  areola  is  a  very  common,  but  not  an 

*  Op.  cit.,  p.  121. 


708  OF  REPRODUCTION. 

invariable,  occurrence  in  the  early  months  of  pregnancy ;  but  another  sign  is 
afforded  by  the  areola  and  nipple,  which  is  of  more  value  because  more  con- 
stant,— namely,  a  puffy  turgescence,  and  an  increased  development  of  the 
little  glandular  follicles,  or  tubercles,  which  commonly  secrete  a  dewy  mois- 
ture.— The  presence  or  absence  of  kiesteine  in  the  Urine  (§  859)  also  may 
probably  be  regarded  as  a  valuable  diagnostic  sign.  This  substance  appears 
on  the  surface  of  the  fluid,  after  it  has  stood  for  two  or  three  days,  in  the  form 
of  a  thin  pellicle  of  a  somewhat  fatty  aspect ;  it  is  preceded  by  a  sediment 
which  has  very  much  the  appearance  of  cotton  wool;  and  it  disappears  when 
the  urine  is  decomposing,  at  the  same  time  emitting  an  odour  like  that  of 
putrid  cheese.* — Many  other  changes  in  the  constitution  take  place  during 
Pregnancy ;  indicated  by  the  buffiness  of  the  blood,  the  irritability  of  the  sto- 
mach, and  the  increased  excitability  of  the  mind.  All  these,  however,  are 
discussed  with  sufficient  amplification,  in  works  on  Obstetric  Medicine. 

927.  The  act  of  Conception,  being  one  of  a  purely  organic  nature,  is  not 
attended  with  any  consciousness  on  the  part  of  the  mother ;  but  there  are 
some  women,  in  whom  it  is  attended  with  certain  sympathetic  affections,  such 
as  faintness,  vertigo,  &c.,  that  enable  them  to  fix  upon  the  particular  time  at 
which  it  has  taken  place.  From  that  period,  however,  the  Mother  has  no 
direct  consciousness  of  the  change  going  on  in  the  Uterus  (save  by  the  effects 
of  its  increasing  pressure  on  other  parts),  until  the  occurrence  of  what  is 
termed  "  Quickening."  This  is  generally  described  as  a  kind  of  fluttering 
movement,  attended  with  some  degree  of  syncope  or  vertigo.  After  it  has 
once  occurred,  and  has  strongly  excited  attention,  it  is  occasionally  renewed 
once  or  twice,  and  then  gives  place  to  the  ordinary  movements  of  the  foetus. 
Not  unfrequently,  however,  no  movement  whatever  is  felt,  until  near  the  end 
of  the  term  of  gestation,  or  even  through  the  whole  of  it.  As  to  the  cause  of 
the  sensation,  Obstetricians  are  much  divided ;  and  no  satisfactory  account 
has  been  given  of  it.  It  has  been  vulgarly  supposed  to  be  due  to  the  first 
movement  of  the  Foetus,  which  was  imagined  then  to  become  possessed  of  an 
independent  life :  and  the  English  law  recognizes  the  truth  of  this  doctrine, 
in  varying  the  punishment  of  an  attempt  to  procure  Abortion,  according  to 
whether  the  woman  be  "  quick  with  child"  or  not;  and  in  delaying  execution 
when  a  woman  can  be  proved  to  be  so,  though  it  is  made  to  proceed  if  she  is 
not,  even  if  she  be  unquestionably  pregnant.  Whether  or  not  the  first  sensible 
motions  of  the  Foetus  are  the  cause  of  the  peculiar  feeling  in  question,  there 
can  be  no  doubt  that  the  Embryo  has  as  much  independent  vitality  before,  as 
after,  the  quickening.  From  the  time  that  the  Ovum  quits  the  Ovary,  it  ceases 
to  be  a  part  of  the  Parent,  and  is  dependent  on  it  only  for  a  due  supply  of 
nourishment,  which  it  converts,  by  its  own  inherent  powers,  into  its  proper 
fabric.  This  dependence  cannot  be  said  to  cease  at  the  moment  of  quicken- 
ing; for  the  connection  must  be  prolonged  during  several  weeks,  before  the 
Foetus  can  be  said  to  be  capable  of  living  without  such  assistance.  The  earliest 
period  at  which  this  may  occur,  will  be  presently  considered  (§  932). 

928.  At  the  conclusion  of  about  nine  (solar)  months  from  the  period  of  con- 
ception, the  time  of  Parturition  arrives.  The  Uterus,  by  its  own  efforts,  and 
by  the  assistance  of  the  muscles  of  Expiration,  expels  its  contents ;  and  the 
membranes  of  the  Ovum  being  usually  ruptured  before  it  is  entirely  dis- 
charged, the  Foetus  comes  at  once  into  the  world.  Although  there  can  be  no 
doubt  that,  as  already  stated  (§  393),  the  contractile  fibres  of  the  Uterus  may 
be  called  into  effectual  action  without  Nervous  influence,  yet  it  is  equally  cer- 
tain that  Uterine  contractions  may  be  induced  through  the  Spinal  system  of 

*  [See  an  excellent  paper  on  this  subject  in  Am.  Journ.  of  Med.  Sci.,  vol.  iv.,  N.  S.,  by 
Elisha  Kane,  M.  D.— M.  C.] 


ACTION  OF  THE  FEMALE.  709 

nerves.  For  in  no  other  way  can  we  account  for  many  phenomena  which 
are  obviously  of  a  reflex  character ;  such  as  the  sudden  contraction  of  the  Ute- 
rus, previously  distended  and  inactive,  when  cold  is  applied  to  the  external 
surface  of  the  body,  or  when  the  child  is  applied  to  the  nipple.  In  the  first 
stage  of  labour,  the  Uterine  contractions  appear  to  be  alone  concerned ;  and 
it  is  not  until  the  head  of  the  child  is  passing  through  the  Os  Uteri,  and  is 
entering  the  Vagina,  that  the  assistance  of  the  Expiratory  muscles  is  called 
in.  The  excitor  fibres,  which  convey  to  the  Spinal  Cord  the  stimulus  that 
calls  them  into  action,  must  originate,  therefore,  rather  in  the  Vagina  than  in 
the  Uterus  itself.  Whilst  the  fibres  of  the  fundus  and  body  of  the  Uterus  are 
in  powerful  contraction,  those  of  the  Cervix  Uteri  and  Vagina  must  be  in  a 
state  of  dilatation ;  and  this  dilatation  appears  to  be  in  some  respects  different 
from  the  mere  yielding  to  the  pressure  of  the  child's  head.  A  slow  contrac- 
tion of  the  fibres  of  the  fundus  and  body  of  the  Uterus,  and  a  yielding  of 
those  of  the  cervix,  usually  take  place  during  some  days  previous  to  Par- 
turition ;  so  that  the  child  lies  lower,  and  the  size  of  the  abdomen  diminishes.* 

929.  As  to  the  reason  why  the  period  of  Parturition  should  be  just  nine 
months  after  that  of  Conception,  we  know  nothing  more  than  we  do  of  that 
of  similar  facts  in  the  physical  history  of  Man — such  as  the  periodical  return 
of  the  Catamenia, — the  renewal  of  the  Teeth, — the  recurrence  of  the  tend- 
ency to  Sleep,  &c.     That  it  is  immediately  dependent  upon  some  state  of  the 
constitution,  rather  than  upon  the  condition  of  the  Uterus,  appears  from  the 
fact  that,  in  cases  of  Extra-uterine  pregnancy,  contractions  resembling  those 
of  labour  take  place  in  its  walls.     Moreover,  various  states  of  the  constitu- 
tion, especially  that  which  is  designated  as  irritability,  may  induce  the  occur- 
rence of  the  parturient  efforts  at  an  earlier  period ;  and  this  constitutes  Abor- 
tion, or  Premature  delivery,  according  to  the  viability  of  the  child.     There 
are  some  women,  in  whom  this  regularly  happens  at  a  certain  month,  so  that  it 
seems  to  be  an  action  natural  to  them  ;  but  it  is  always  to  be  prevented,  if  pos- 
sible, being  injurious  alike  to  the  mother  and  child ;  and  this  prevention  is  to 
be  attempted  by  rest  and  tranquillity  of  mind  and  body,  and  by  a  careful  avoid- 
ance of  all  the  exciting  causes,  which  may  produce  Uterine  contractions  by 
their  operation  on  the  Nervous  system.     For  it  is  to  be  remembered  that, 
although  the  muscular  fibres  of  the  Uterus  are  capable,  like  those  of  the  ali- 
mentary canal,  of  an  independent  action,  they  are  likely  to  be  excited  to  ope- 
ration through  the  Nervous  system,  and  especially  through  the  Sympathetic 
(§  393).     The  same  action  which  expels  the  Foetus,  also  detaches  the  Pla- 
centa ;  and  if  the  Uterus  contract  with  sufficient  force  after  this  has  been 
thrown  off,  the  orifices  of  the  vessels  which  communicated  with  it  are  so 
effectually  closed,  that  little  or  no  hemorrhage  takes  place.     If,  however,  the 
Uterus  does  not  contract,  or  relaxes  after  having  contracted,  a  large  amount 
of  blood  may  be  lost  in  a  short  time  from  the  open  orifices.     For  some  little 
time  after  Parturition,  a  sero-sanguineous   discharge,  termed  the  Lochia,  is 
poured  out  from  the  Uterus ;  and  this  commonly  contains  shreds  of  the  De- 
ciduous membrane,  which  had  not  been  previously  detached.     Within  a  few 
weeks  after  delivery,  the  Uterus  regains  (at  least  in  a  healthy  subject)  its  pre- 
vious condition;  and  it  is  probable  that  the  portion  of  its  mucous  Membrane, 
which  had  been  thrown  off  as  Decidua,  is  very  early  reproduced. 

930.  Although  the  duration   of  Pregnancy  is  commonly   stated  at  nine 
solar  months,  it  would  be  more  correct  to  fix  the  period  at  40  weeks,  or  280 
days ;  which  exceeds  nine  months  by  from  5  to  7   days,  according  to  the 
months  included.     This,  at  least,  is  the  average  result  of  observation,  in  cases 

*  See  some  interesting  Papers  on  the  Physiology  of  Parturition,  by  Dr.  W.  Tyler  Smith, 
in  the  Lancet,  July  6  and  13,  1844. 

60 


710  OF  REPRODUCTION. 

in  which  the  period  of  Conception  could  be  fixed  from  peculiar  circumstances, 
with  something  like  certainty.  The  mode  of  reckoning  customary  among 
women,  is  to  date  from  the  middle  of  the  month  after  the  last  appearance  of 
the  Catamenia;  but  it  is  certain  that  Conception  is  much  more  likely  to  take 
place  soon  after  they  have  ceased  to  flow,  or  even  before  their  access,  than  at 
a  later  period  (§  909) ;  so  that,  in  most  instances,  it  would  be  most  correct  to 
expect  Labour  at  forty  weeks  and  a  few  days  after  the  last  recurrence  of  the 
Menses.  The  period  of  Quickening  may  be  relied  on  in  some  women,  in 
whom  it  occurs  with  great  regularity  in  a  certain  week  of  Pregnancy ;  but 
there  is  in  general  great  latitude  as  to  the  time  of  its  occurrence.  The  usual 
or  average  time  is  probably  about  the  18th  week. 

931.  The  question  of  the  extreme  limits  of  Gestation,  is  one  of  great  import- 
ance both  to  the  Practitioner  and  to  the  Medical  Jurist ;  but  it  is  one  which 
cannot  yet  be  regarded  as  satisfactorily  decided.  Many  persons,  whose  expe- 
rience should  give  much  weight  to  their  opinion,  maintain  that  the  regular 
period  of  40  weeks  is  never  extended  for  more  than  two  or  three  days  ;  whilst, 
on  the  other  hand,  there  are  numerous  cases  on  record,  which,  if  testimony  is 
to  be  believed  at  all,  (and  in  many  of  these,  the  character  and  circumstances 
of  the  parties  placed  them  above  suspicion,)  furnish  ample  evidence  that  Ges- 
tation may  be  prolonged  for  at  least  three  wreeks  beyond  the  regular  term.* 
The  English  law  fixes  no  precise  limit ;  and  the  decisions  which  have  been 
given  in  our  courts,  when  questions  of  this  kind  have  been  raised,  have  been 
mostly  formed  upon  the  collateral  circumstances.  The  law  of  France  pro- 
vides that  the  legitimacy  of  a  child  born  within  300  days  after  the  death  or 
departure  of  the  husband,  shall  not  be  questioned  ;  and  a  child  born  after  more 
than  300  days  is  not  declared  a  bastard,  but  its  legitimacy  may  be  contested. 
By  the  Scotch  law,  a  child  is  not  declared  a  bastard,  unless  born  after  the 
tenth  month  from  the  death  or  departure  of  the  husband. 

a.  The  analogical  evidence  drawn  from  observations  on  the  lower  animals  is  extremely 
strong.     The  observations  of  Tessier,  which  were  continued  during  a  period  of  forty  years, 
with  every  precaution  against  inaccuracy,  have  furnished  a  body  of  results,  which  seems 
quite  decisive.     In  the  Cow,  the  ordinary  period  of  gestation  is  about  the  same  as  in  the 
Human  female;  but  out  of  577  individuals,  no  less  than  20  calved  beyond  the  298th  day,  and 
of  these,  some  went  on  to  the  321st,  making  an  excess  of  nearly  six  weeks.     Of  447  Mares, 
whose  natural  period  of  gestation  is  about  335  days,  42  foaled  between  the  359th  and  the  419th 
day,  the  greatest  protraction  being  thus  84  days,  or  just  one-fourth  of  the  usual  term.     Of  912 
Sheep,  whose  natural  period  is  about  151  days,  96  yeaned  beyond  the  153d  day;  and  of 
these,  7  went  on  until  the  157th  day,  making  an  excess  of  6  days.     Of  161  Rabbits,  whose 
natural  period  is  about  30  days,  no  fewer  than  25  littered  between  the  32d  and  35th ;  the 
greatest  protraction  was  here  one-sixth  of  the  whole  period,  and  the  proportion  in  which 
there  was  a  manifest  prolongation  was  also  nearly  one-sixth  of  the  total  number  of  indi- 
viduals.    In  the  incubation  of  the  common  Hen,  Tessier  found  that  there  was  not  unfre- 
quently  a  prolongation  to  the  amount  of  three  days,  or  one-seventh  of  the  whole  period. 

b.  In  regard  to  Cows,  the  observations  of  Tessier  have  been  recently  confirmed  by  those 
of  Earl  Spencer,  who  has  published!  a  table  of  the  period  of  gestation  as  observed  in  764 
individuals;  he  considers  the  average  period  to  be  284  or  285  days:  but  no  fewer  than  310 
calved  after  the  285th  day;  and  of  these,  3  went  on  to  the  306th  day,  and  1  to  the  313th. 
It  is  curious  that,  among  the  calves  born  between  the  290th  and  300th  days,  there  was  a 
decided  preponderance  of  males, — these  being  74,  to  32  females ;  whilst  all  of  those  born 
after  the  300th  day  were  females. 

c.  It  appears,  however,  from  some  recent  statements  published  on  the  authority  of  Earl 
Spencer,  that  the  Male  parent  may  exert  an  important  influence  on  the  period  of  gestation. 
Of  75  Cows  in  calf  by  a  particular  bull,  the  average  period  was  288£  days,  or  four  days 
more  than  the  usual  period.     Of  the  764  cows  previously  mentioned,  185  (nearly  one-fourth) 
went  less  than  281  days;  whilst  not  one  of  the  cows  in  calf  to  this  bull  did  so.     On  the 


*  A  good  collection  of  such  cases  will  be  found  in  Dr.  Montgomery's  excellent  work  on 
the  Signs  of  Pregnancy. 

f  Journal  of  the  English  Agricultural  Society,  1839. 


ACTION  OF  THE  FEMALE.  711 

other  hand,  of  the  764  cows  first  mentioned,  111  (rather  more  than  one-seventh)  went  above 
289  days;  while,  of  the  cows  in  calf  by  this  bull,  29  out  of  75  (nearly  two-fifths)  went  above 
289  days  * 

d.  Another  series  of  observations  has  recently  been  published  by  Mr.  C.  N.  Bement  of 
Albany,  U.  S.,f  who  has  recorded  the  period  of  gestation  of  62  Cows.  The  longest  period 
was  336  days;  the  shortest,  213  days.  The  average  period  for  male  calves  was  288  days; 
and  for  females,  282  days. 

These  variations  are  probably  to  be  regarded  as  due,  not  so  much  to  a  pro- 
longation of  the  period  of  tftero-gestation,  as  to  various  circumstances  which 
may  have  a  retarding  influence  on  the  process  of  Fecundation,  and  on  the 
transmission  of  the  Ovum  through  the  Fallopian  tube.  These  have  been  well 
pointed  out  by  Dr.  Montgomery.^  It  may  be  a'dded  that,  in  Dr.  Barry's  ob- 
servations on  the  early  changes  that  take  place  in  the  Ovum  of  Rabbits,  he 
has  noticed  several  irregularities  of  this  description. — On  the  whole,  it  may 
be  considered  that,  in  regard  to  the  Human  female,  the  French  law  is  a  very 
reasonable  one.  It  is  probable,  from  the  circumstances  alluded  to  in  the  pre- 
ceding paragraph,  that  Gestation  is  protracted  to  the  extent  of  a  week,  ten 
days,  or  a  fortnight,  much  more  frequently  than  is  commonly  supposed.  In 
several  of  the  cases  in  which  the  protraction  appeared  indubitable,  the  Infant 
was  unusually  large  and  vigorous. 

932.  In  regard  to  the  shortest  period  at  which  Gestation  may  terminate, 
consistently  with  the  viability  of  the  Child,  there  is  a  still  greater  degree  of 
uncertainty.  Most  practitioners  are  of  opinion,  that  it  is  next  to  impossible 
for  a  Child  to  live  and  grow  to  maturity,  which  has  not  nearly  completed  its 
seventh  month  ;  but  it  is  almost  unquestionable  that  Infants,  which  have  been 
born  at  a  much  earlier  period,  have  lived  for  some  months.  It  is  rare  in  such 
cases,  however,  that  the  date  of  Conception  can  be  fixed  with  sufficient  pre- 
cision to  enable  a  definite  statement  to  be  given.  Of  the  importance  of  the 
question,  a  case  which  recently  occurred  in  Scotland  affords  sufficient  proof. 
A  vast  amount  of  contradictory  evidence  was  adduced  on  this  trial ;  but,  on 
the  general  rule  of  accepting  positive  in  preference  to  negative  testimony,  it 
seems  that  we  ought  to  consider  it  possible,  that  a  child  may  live  for  some 
months,  which  has  been  born  at  the  conclusion  of  24  weeks  of. gestation.  In 
the  case  in  question,  the  Presbytery  decided  in  favour  of  the  legitimacy  of  an 
Infant  born  alive  within  25  weeks  after  marriage. § 

a.  A  very  interesting  case  is  on  record, ||  in  which  the  mother  (who  had  borne  five  chil- 
dren) was  confident  that  her  period  of  gestation  was  less  than  19  weeks;  the  facts  stated 
respecting  the  development  of  the  child  are  necessarily  very  imperfect,  as  it  was  important 
to  avoid  exposing  his  body,  in  order  that  his  temperature  might  be  kept  up;  but  at  the  age 
of  three  weeks,  he  was  only  13  inches  in  length,  and  his  weight  was  no  more  than  29  oz. 
At  that  time,  he  might  be  regarded,  according  to  the  calculation  of  the  mother,  as  correspond- 
ing with  an  infant  of  22  weeks  or  5^  months;  but  the  length  and  weight  were  greater  than 
is  usual  at  that  period,  and  he  must  have  been  probably  born  at  about  the  25th  week.     It  is 
an  interesting  feature  in  this  case,  that  the  calorific  power  of  the  Infant  was  so  low,  that 
artificial  heat  was  constantly  needed  to  sustain  it;  but  that,  under  the  influence  of  the  heat 
of  the  fire,  he  evidently  became  weaker,  whilst  the  warmth  of  a  person  in  bed  rendered 
him  lively  and  comparatively  strong.     During  the  first  week,  it  was  extremely  difficult  to 
get  him  to  swallow ;  and  it  was  nearly  a  month  before  he  could  suck.     At  the  time  of  the 
report,  he  was  four  months  old,  and  his  health  appeared  very  good. 

b.  Another  case  of  very  early  viability  has  been  more  recently  put  on  record  by  Mr. 
Dodd:1T  in  this,  as  in  the  former  instance,  the  determination  of  the  child's  age  rests  chiefly 
on  the  opinion  of  the  mother ;  but  there  appears  no  reason  for  suspecting  any  fallacy.     The 


*  Dr.  J.  C.  Hall,  in  Medical  Gazette,  May  6,  1842. 

f  American  Journal  of  the  Medical  Sciences,  October,  1845.  J  Op.  cit,  p.  272. 

§  Report  of  Proceedings  against  the  Rev.  Fergus  Jardine,  Edin.,  1839. 

||  Edinb.  Med.  and  Surg.  Journal,  vol.  xi. 

IT  Provincial  Medical  and  Surgical  Journal,  vol.  ii.  p.  474. 


712  OF  REPRODUCTION. 

child  seems  to  have  been  born  at  the  26th  or  27th  week  of  gestation ;  and  having  been 
placed  under  judicious  management,  it  has  thriven  well. 

c.  One  of  the  most  satisfactory  cases  on  record,  is  that  detailed  by  Dr.  Outrepont  (Professor 
of  Obstetrics  at  Wurtzburgh),  arfd  stated  by  Dr.  Christison  in  his  evidence  on  the  case  just 
alluded  to.     The  evidence  is  as  complete  as  it  is  possible  to  be  in  any  case  of  the  kind ;  being 
derived  not  only  from  the  date  assigned  by  the  Mother  to  her  Conception,  but  also  from  the 
structure  and  history  of  the  Child.     The  Gestation  could  have  only  lasted  27  weeks,  and  was 
very  probably  less.     The  length  of  the  child  was  13^  inches,  and  its  weight  was  24  oz.     Its 
development  was  altogether  slow;  and  at  the  age  of  eleven  years,  the  child  seemed  no  more 
advanced  in  body  or  mind,  than  most  other  lads  of  seven  years  old.     In  this  last  point,  there 
is  a  very  striking  correspondence  with  the  results  of  other  observations  upon  very  prema- 
ture children,  made  at  an  earlier  age :  and  these  all  harmonize  with  the  general  principle 
already  more  than  once  alluded  to, — that  the  shorter  the  period  during  which  the  early  de- 
velopment of  the  embryo  takes  place  at  the  expense  of  nourishment  supplied  by  the  parent, 
the  lower  is  the  degree  of  development  it  will  ultimately  attain  (§  45). 

d.  To  these  may  be  added  another  case  of  recent  occurrence  in  America :  in  which  a 
woman,  who  believed  herself  to  be  in  the  sixth  month  of  pregnancy,  was  prematurely  de- 
livered in  consequence  of  a  fall.     The  child  seemed  barely  alive,  showing  scarcely  any 
motion,  and  being  too  feeble  to  cry.  It  had  no  nails  on  its  hands  or  feet,  nor  hair  on  the  scalp  ; 
and  the  cranium  was  imperfectly  ossified.     At  the  end  of  seven  weeks  it  was  weighed  for 
the  first  time,  and  found  to  weigh  only  26  oz.     When  ten  months  old,  it  was  playful,  lively, 
and  healthy;  and  weighed  10£  Ibs.     The  reporter  of  this  case  regrets  that  he  did  not  take 
more  particular  notice  of  the  state  of  the  Child  at  birth,  which  he  was  prevented  from 
doing  by  the  daily  expectation  of  its  death.* 

933.  There  is  another  question  regarding  the  Function  of  the  Female  in 
the  Reproductive  act,  which  is  of  great  interest  in  a  scientific  point  of  view, 
and  which  may  become  of  importance  in  Juridical  inquiries ; — namely,  the 
possibility  of  ^uperfoetation^  that  is,  of  two  distinct  conceptions  at  an  interval 
of  greater  or  less  duration  ;  so  that  two  foetuses  of  different  ages,  the  offspring 
perhaps  of  different  parents,  may  exist  in  the  Uterus  at  the  same  time.— The 
simplest  case  of  Superfretation,  the  frequent  occurrence  of  which  places  it  be- 
yond reasonable  doubt,  is  that  in  which  a  female  has  intercourse  on  the  same 
day  with  two  Males  of  different  complexions,  and  bears  twins  at  the  full  time; 
the  two  infants  resembling  the  two  parents  respectively.  Thus,  in  the  slave- 
states  of  America,  it  is  not  uncommon  for  a  black  woman  to  bear  at  the  same 
time  a  black  and  a  mulatto  child ;  the  former  being  the  offspring  of  her  black 
husband,  and  the  latter  of  her  white  paramour.  The  converse  has  occasionally 
though  less  frequently,  occurred  ;  a  white  woman  bearing  at  the  same  time  a 
white  and  a  mulatto  child.  There  is  no  difficulty  in  accounting  for  such 
facts,  when  it  is  remembered  that  nothing  has  occurred  to  prevent  the  Uterus 
and  Ovaria  from  being  as  ready  for  the  second  conception  as  for  the  first ;  since 
the  orifice  of  the  former  is  not  yet  closed  up  ;  and,  at  the  time  when  one  ovum 
is  matured  for  fecundation,  there  are  usually  more  in  the  same  condition. 
But  it  is  not  easy  thus  to  account  for  the  birth  of  two  children,  each  appa- 
rently mature,  at  an  interval  of  five  or  six  months ;  since  it  might  have  been 
supposed  that  the  uterus  was  so  completely  occupied  with  the  first  Ovum,  as 
not  to  allow  of  the  transmission  of  the  seminal  fluid,  necessary  for  the  fecun- 
dation of  the  second.  In  cases  where  two  children  have  been  produced  at 
the  same  time,  one  of  which  was  fully-formed,  whilst  the  other  was  small  and 
seemingly  premature,  there  is  no  occasion  whatever  to  imagine  that  the  two 
were  conceived  at  different  periods ;  since  the  smaller  foetus  may  have  been 
"  blighted,"  and  its  development  retarded,  as  not  unfrequently  happens  in  other 
cases.  Nor  is  it  necessary  to  infer  the  occurrence  of  Superfoetation  in  every 
case,  in  which  a  living  child  has  been  produced  a  month  or  two  after  the  birth 
of  another;  since  the  latter  may  have  been  premature,  whilst  the  former  has 
been  carried  to  the  full  term.  But  such  a  difference  can  scarcely  be,  at  the 

*  American  Journal  of  the  Medical  Sciences,  April  1843. 


DEVELOPMENT  OF  THE  EMBRYO.  713 

most,  more  than  2|  or  three  months ;  and  there  are  several  cases  now  on  re- 
cord, in  which  the  interval  was  from  110  to  170  days,  whilst  neither  of  the 
children  was  premature  in  appearance;  so  that  the  possibility  of  a  second 
Conception,  when  the  Uterus  already  contains  an  Ovum  of  several  months, 
can  scarcely  be  denied,  however  improbable  it  may  seem. 

4. — Development  of  the  Embryo. 

934.  Under  this  head  it  is  intended  to  state,  not  so  much  the  details  of  the 
process  of  Development,  as  those  leading  facts,  the   knowledge  of  which  is 
desirable  in  itself,  as  well  as  essential  to  the  due  comprehension  of  the  former. 
It  is  difficult  to  see  what  practical  benefit  can  result  from  a  minute  acquaint- 
ance with  all  the  steps  of  the  evolution  of  the  Embryo,  however  interesting 
these  may  be  in  a  scientific  point  of  view ;  and  the  time  of  the  ordinary  Stu- 
dent, on  which  there  are  so  many  pressing  calls,  may  be  much  better  occupied 
than  in  committing  them  to  memory.     In  the  following  sketch,  little  will  be 
said  respecting  the  latter  stages  of  the  process,  or  the  development  of  particular 
organs,  since  these  have  been  already  noticed  under  their  severally  distinct 
heads.     Our  attention  will  first  be  given  to  the  formation  of  the  Embryonic 
mass,  and  of  the  membranes  surrounding  the  Yolk-bag;  and  then  to  the  ori- 
gin of  the  Vertebral  column,  Digestive  organs,  and  Circulating  apparatus. 

935.  The  Ovum,  when   it  quits  the  Ovarium,  has   been  stated  to  contain 
within  the  Germinal  Vesicle,  two  cells  which  tlid  not  exist  there  previously 
to  fecundation ;  and  from  each  of  these,  two  new  cells  are  subsequently  pro- 
duced, which  in  their  turn  give  birth  to  eight  others  (§  917).     In  this  manner, 
the  number  of  vesicles  originating  in  the  twin-cells  of  the  Germ  is  continually 
increased,  until  at  last  they  become  too  numerous  to  be  counted,  and  form  a 
cluster  resembling  a  Mulberry  in  appearance;  this  mulberry-like  structure 
maybe  conveniently  termed  the  Germinal  Mass  (Plate  I.,  Fig.  15,  a).    In  the 
centre  of  this  mass  there  is  found  a  peculiar  Cell,  differing  from  the  rest  in  its 
greater  size,  and  in  possessing  a  very  well-defined  annular  nucleus,  with  a 
pellucid  cavity  in  its  centre  (Fig.  16,  a,  6).     From  this  peculiar  Cell,  all  the 
parts  which  enter  permanently  into  the  composition  of  the  Embryo  are  de- 
veloped ;  the  vesicles  forming  the  exterior  of  the  germinal  mass  being  sub- 
servient to  a  merely  temporary  purpose.     This  central  or  Embryonic  Cell  is 
gradually  brought  to  the  surface  of  the  Germinal  Mass,  by  the  formation  of  a 
cavity    c   in  the  interior  of  the  latter;  for  the  layer  of  cells  within  which  this 
cavity  is  formed,  progressively  extends  itself,  until  it  comes  into  contact  with 
the  inner  surface  of  the  Yolk-bag,  having  absorbed  the  yolk  into  the  hollow 
thus  left.     Thus  out  of  the  periphery  of  the  Mulberry-mass,  appears  to  be 
formed  the  exterior  layer  of  what  is  termed  the  Germinal  Membrane :  this 
membrane  is  first  seen  as  an  epithelium-like  layer  of  cells,  covering  the  Yolk ; 
but  beneath  this  layer,  which  is  afterwards  known  as  the  serous  lamina  of  the 
Germinal  membrane,  two  others  are  subsequently  produced  from  the  central 
portion  of  the  Germinal  mass.     Now  it  is  highly  interesting  to  observe,  that 
this  Germinal  Membrane,  which  in  the  higher  animals  is  a  mere  temporary 
structure,  subservient  only  to  a  temporary  function,  forms,  in  the  lower  tribes, 
the  greater  part  of  the  permanent  fabric  of  the  body.     Thus,  in  the  Polypes, 
the  cavity  in  which  the  Yolk  is  inclosed  becomes  a  Stomach  ;  the  external 
layer  of  the  Germinal  Membrane  becomes  the  integument ;  whilst  the  internal 
forms  the  lining  of  the  Digestive  cavity,  of  which  the  mouth  is  formed  by 
absorption  of  its  wall  at  one  point.     Here  the  Yolk  is  directly  absorbed  and 
assimilated  by  the  surrounding  membrane.     In  the  higher  Oviparous  animals, 
the  Germinal  Membrane  serves  to  absorb  nutritious  matter  from  the  Yolk, 
and  to  prepare  it  for  the  use  of  the  Embryo  itself,  by  converting  it  into  "Blood 

60* 


714  OF  REPRODUCTION. 

(§  938) ;  but,  after  the  Yolk  has  been  exhausted,  the  Yolk-bag  is  taken  into 
the  body,  and  is  gradually  removed  by  absorption.  In  Mammalia,  these 
structures  are  of  less  importance.  The  store  of  Yolk,  laid  up  for  the  nutrition 
of  the  Embryo,  is  comparatively  inconsiderable ;  being  only  destined  to  serve 
for  the  short  time  that  elapses,  before  the  Ovum  forms  its  new  connection 
with  the  Parent,  through  the  medium  of  the  Chorion ;  and  the  Yolk-bag  is 
ultimately  separated  from  the  Embryo,  and  thrown  off  as  useless.  Still  the 
early  processes  are  the  same  in  Mammiferous,  as  they  are  in  Oviparous  ani- 
mals ;  and  the  Development  of  Man,  of  a  Bird,  of  a  Reptile,  or  of  a  Fish, 
takes  place,  up  to  a  certain  point,  upon  the  same  general  plan. 

936.  The  Embryonic  Cell,  and  the  cluster  of  cells  that  surrounds  it,  hav- 
ing arrived  on  the  surface  of  the  Yolk  by  the  movement  just  described,  con- 
stitute what  is  known  in  the  Bird's  egg  under  the  name  of  the  Cicatricula. 
This  is  a  semi-opaque  disc,  composed  of  numerous  flattened  cells ;  and  in  the 
midst  of  it  is  seen  a  round  transparent  space,  termed  the  Area  Pellucida, 
which  is  nothing  else  than  the  place  occupied  by  the  large  Embryonic  Cell, 
now  become  flattened,  and  still  retaining  its  clearness.     In  the  centre  of  this 
is  seen  a  very  faint  line,  which  is  termed  the  Primitive  Trace;  and  this  is 
the  large  annular  Nucleus  (Plate  L,  Fig.  16,  b)  of  the  Embryonic  Cell,  now 
become  elongated,  and  itself  beginning  to  be  developed  into  cells.     The  same 
process  then  takes  place  within  the  Embryonic  Cell,  which  has  been  described 
as  occurring  within  the  Germinal  Vesicle  (§  916);  the  granules  forming  the 
periphery  of  the  nucleus  are  first  developed  into  cells,  and  these  are  pushed 
outwards  by  a  new  series  subsequently  generated  near  the  centre.     From  the 
mass  of  cells  thus  formed,  a  hollow  process  passes  down  into  the  Yolk;  and 
this  gradually  extends  itself  in  the  same  manner  as  did  that  formed  from  the 
Mulberry-mass,  until  it  includes  the  whole  Yolk,  and  comes  into  contact  with 
the  inner  surface  of  the  layer  of  cells  already  mentioned  as  forming  the  serous 
or  external  lamina  of  the  Germinal  Membrane.     This  second  layer  of  cells 
is  probably  that  which  forms  the  vascular  lamina  of  the  Germinal  Membrane. 
A  third  process  seems  to  be  afterwards  sent  down,  from  a  part  of  the  nucleus 
somewhat  interior  to  that  from  which  the  last  proceeded :  and  this  becomes 
the  mucous  or  internal  lamina  of  the  Germinal  Membrane. 

937.  The  cell-germs  forming  the  periphery  of  the  Nucleus  having  been  thus 
developed,  those  nearer  the  centre  then  begin  to  exhibit  a  corresponding  acti- 
vity.    Their  evolution  follows  exactly  the  same  plan  as  that  which  has  been 
described  in  regard  to  the  contents  of  the  Germinal  Vesicle  (§  916);  with 
the  exception  that  these  are   arranged  in  an  elongated  and  not  in  a  circular 
form.     The  shape  of  the  nucleus  at  this  time  may  be  compared  to  that  of  a 
pear;  the  large  end  marking  the  situation  of  the  Head  ;  whilst  the  prolonged 
portion  is  the  rudiment  of  the  body.     On  the  median  line  is  seen  a  groove, 
occupying  the  situation  in  which  the  Nervous  Centres  are  to  be  subsequently 
evolved  (Fig.  25,  Plate  II.).     These,  when  first  developed,  are  surrounded  by 
a  tubular  structure,  which  has  but  a  temporary  existence  in  the  higher  Verte- 
brata,  but  which  is  permanent  in  the  lower  Fishes  :  this  structure,  termed  the 
Chorda  Dorsalis,  is  found,  wherever  it  exists,  to  be  entirely  composed  of 
nucleated  cells.     From  the  cells  which  are  exterior  to  these,  is  produced  the 
Vertebral  Column ;  and  the  mode  in  which  this  originates  is  somewhat  as 
follows.    The  cells  on  either  side  of  the  central  space  (in  which  the  elements 
of  the  nervous  system  are  not  yet  developed)  rise  up  in  a  ridge,  so  that  the 
central  space  becomes  a  groove ;  these  two  ridges  gradually  rise  up  and  ap- 
proach one  another,  and  they  are  then  observed  to  contain,  in  what  subse- 
quently becomes   the  thoracic  region,  a  few  pairs   of  small  opaque  plates. 
The  ridges  (termed  plicse  dorsales,or  dorsal  laminae)  continue  inclining  towards 
each  other,  until  they  coalesce,  so  that  a  complete  tube  is  formed ;  and  in  this 


DEVELOPMENT  OF  THE  EMBRYO.  715 

tube  an  indication  is  soon  perceived  of  a  division  into  vertebrae,  of  which  the 
plates  just  mentioned  are  the  incipient  arches  (Fig.  26,  Plate  II.).  Towards 
the  anterior  extremity,  however,  the  dorsal  laminae  do  not  at  once  close  in ; 
and  the  large  cells,  in  which  the  great  divisions  of  the  Encephalon  originate 
(§  358),  may  be  seen  between  them.  From  the  Dorsal  Lamina  on  either  side, 
a  prolongation  passes  outwards  and  then  downwards,  forming  what  is  known 
as  the  ventral  lamina  ;  in  this  are  developed  the  Ribs  and  the  transverse  pro- 
cesses of  the  Vertebrae  ;  and  the  two  have  the  same  tendency  to  meet  on  the 
median  line,  and  thus  to  close  in  the  abdominal  cavity,  which  the  dorsal 
laminae  have  to  inclose  the  spinal  cord.  At  the  same  time  the  layers  of  the 
Germinal  Membrane,  which  lie  beyond  the  extremities  of  the  Embryo,  are 
folded  in,  so  as  to  make  a  depression  on  the  yolk ;  and  their  folded  margins 
gradually  approach  one  another  under  the  abdomen.  In  these  two  modes,  a 
cavity  is  formed  beneath  the  Embryonic  mass,  which  is  separated  from  the 
general  cavity  of  the  Yolk  by  the  folds  just  described;  but  these  still  leave  a 
passage  which,  in  the  Bird,  remains  of  considerable  size  until  a  much  later 
period,  but  which,  in  the  Mammiferous  Ovum,  is  soon  obliterated.  For  the 
sac  which  contains  the  yolk,  and  from  which  the  abdominal  cavity  is  pinched 
off  (as  it  were)  at  a  very  early  period,  is  destined,  in  the  Mammiferous  ani- 
mal, to  be  entirely  cast  away ;  the  purpose  which  it  has  to  serve  being  one  of 
a  very  temporary  character. 

938.  Whilst  these  new  structures  are  being  produced,  a  very  remarkable 
change  is  taking  place  in  that  part  of  the  Serous  lamina,  which  surrounds  the 
Area  Pellucida.  This  rises  up  on  either  side  in  two  folds ;  and  these  gradually 
approach  one  another,  at  last  meeting  in  the  space  between  the  general  en- 
velope and  the  embryo,  and  thus  forming  an  additional  investment  to  the 
latter.  As  each  fold  contains  two  layers  of  membrane,  a  double  envelope 
is  thus  formed ;  of  this,  the  outer  lamina  adheres  to  the  general  envelope ; 
whilst  the  inner  remains  as  a  distinct  sac,  to  which  the  name  of  Jlmnion  is 
given.  (See  Figs.  284,  285,  and  286.)  This  takes  place  during  the  third 
day  in  the  Chick ;  the  period  at  which  it  occurs  in  the  Human  Ovum  is  diffi- 
cult to  be  ascertained,  owing  to  the  small  number  of  normal  specimens  which 
have  come  under  observation  at  a  sufficiently  early  stage. — During  the  same 

Fig.  283.  Fig.  284. 


Plan  of  early  uterine  Ovum.    Within  the  Diagram  of  ovum  at  later  stage;  the  digestive  ca- 

external  ring,  or  zona  pellucida,  are  the  serous  vity  beginning  to  be  separated  from  the  yolk-sac, 

lamina,  a;  the  yolk,  b;  and  the  incipient  em-  and  the  amnion  beginning  to  be  formed;  a,  chorion; 

bryo,  c.  6,  yolk-sac ;  c,  embryo ;  d,  and  e,  folds  of  the  serous 

layer  rising  up  to  form  the  Amnion. 

period,  a  very  important  provision  for  the  future  support  of  the  Embryo  begins 
to  be  made;  by  the  development  of  Blood-vessels  and  the  formation  of  Blood. 
Hitherto,  the  Embryonic  structure  has  been  nourished  by  direct  absorption  of 


716  OF  REPRODUCTION. 

the  alimentary  materials  supplied  to  it  by  the  Yolk ;  in  the  same  manner  as 
the  simplest  Cellular  plant  is  developed  at  the  expense  of  the  carbonic  acid, 
moisture,  &c.,  which  it  obtains  for  itself  from  the  surrounding  elements.  But 
its  increasing  size,  and  the  necessity  for  a  more  free  communication  between 
its  parts  than  any  structure  consisting  of  cells  alone  can  permit,  call  for  the 
development  of  Vessels,  through  which  the  nutritious  fluid  may  be  conveyed. 
These  vessels  are  first  seen  in  that  part  of  the  Vascular  lamina  of  the  Germinal 
Membrane,  which  immediately  surrounds  the  embryo ;  and  they  form  a  net- 
work, bounded  by  a  circular  channel,  which  is  known  under  the  name  of  the 
Vascular  <flrea  (Fig.  27,  Plate  II.).  This  gradually  extends  itself,  until  the 
vessels  spread  over  the  whole  of  the  membrane  containing  the  yolk.  The 
first  blood-discs  appear  to  be  formed  from  the  nuclei  of  the  cells,  whose 
cavities  have  become  continuous  with  each  other  to  form  the  vessels  (§  222) ; 
and  from  these,  all  subsequent  blood-discs  are  probably  generated.  This  net- 
work of  blood-vessels  serves  the  purposes  of  absorbing  the  nutritious  matter 
of  the  Yolk,  and  of  conveying  it  towards  the  embryonic  structures,  which  are 
now  in  process  of  rapid  development.  The  first  movement  of  the  fluid  is 
towards  the  embryo ;  and  this  can  be  witnessed  before  any  distinct  heart  is 
evolved.  The  same  process  of  absorption  from  the  Yolk,  and  of  conversion 
into  Blood,  probably  continues  as  long  as  there  is  any  alimentary  material  left 
in  the  sac. 

939.  The  Yolk-sac  is  early  separated  in  the  Mammalia,  by  a  constriction 
of  the  portion  which  is  continuous  with  the  abdomen  of  the  Embryo ;  and  it 
is  known  from  that  time  under  the  name  of  the  Umbilical  Vesicle.     The  com- 
munication, however,  remains  open  for  a  time  through  the  constricted  portion, 
which  is  termed  the  Vitelline  Duct ;  and  even  after  this  has  been  cut  off,  the 
trunks  which  connected  the  circulating  system  of  the  Embryo  with  that  of  the 
Vascular  Area,  are   still  discernible;  these  are  called  Omphalo-Mesenteric, 
Meseraic,  or  Vitelline  vessels.     It  was  formerly  believed,  that  the  nutrient 
matter  of  the  yolk  passes  directly  through  the  Vitelline  duct,  into  the  (future) 
digestive  cavity  of  the  Embryo,  and  is  from  it  absorbed  into  its  structure;  but 
there  can  now  be  little  doubt,  that  the  Vitelline  vessels  are  the  real  agents  of 
its  absorption,  and  that  they  convey  it  to  the  tissues  in  process  of  formation. 
They  do,  in  fact,  correspond  to  the  Mesenteric  veins  of  Invertebrated  animals, 
which  are  the  sole  agents  in  the  absorption  of  nutriment  from  their  digestive 
cavity  (§  674) ;  and  the  yolk-bag,  as  already  remarked,  is  the  temporary  sto- 
mach of  the  Embryo, — remaining  as  the  permanent  stomach  in  the  Radiated 
tribes.     Previously  to  the  ninth  day  of  incubation  (in  the  Fowl's  egg),  a  series 
of  folds  are  formed  by  the  lining  membrane  of  the  yolk-bag,  which  project 
into  its  cavity;  these  become  gradually  deeper  and  more  crowded,  as  the  bag 
diminishes  in  size  by  the  absorption  of  its  contents.     The  Vitelline  vessels, 
that  ramify  upon  the  yolk-bag,  send  into  these  folds  (or  valvula?  conniventes) 
a  series  of  inosculating  loops,  which  immensely  increase  the  extent  of  this 
absorbing  apparatus.     But  these  minute  vessels  are  not  in  immediate  contact 
with  the  yolk;  for  there  intervenes  between  them  a  layer  of  nucleated  cells, 
which  is  easily  washed  away.     It  was  from  the  colour  of  these,  communicated 
to  the  vessels  beneath,  that  Haller  termed  the  latter  vasa  lutea;  when  the 
layer  is  removed,  the  vessels  present  their  usual  colour.     There  seems  good 
reason  to  believe,  that  these  cells,  like  those  of  the  Intestinal  Villi  in  the  adult 
(§  672),  are  the  real  agents  in  the  process  of  absorbing  and  assimilating  the 
nutritive  matter  of  the  yolk ;  and  that  they  deliver  this  up  to  the  vessels,  by 
themselves  undergoing  rupture  or  dissolution,  being  replaced  by  new  layers. 

940.  The  formation  of  the  Heart  takes  place  in  the  Vascular  layer,  beneath 
the  upper  part  of  the  Spinal  Column ;  it  at  first  appears  as  a  mere  cavity  in  its 
substance,  surrounded  only  by  cells ;  but  its  walls  gradually  acquire  firmness 


DEVELOPMENT  OF  THE  EMBRYO. 


717 


and  distinctness,  and  become  sufficiently  powerful  to  propel  the  blood  through 
the  vessels  of  the  Embryo  and  those  of  the  Vascular  Area.  The  first  ap- 
pearance of  the  Heart  in  the  Chick  is  at  about  the  27th  hour ;  the  time  of  its 
formation  in  Mammalia  has  not  been  distinctly  ascertained.  In  its  earliest 
form,  it  has  the  same  simple  character,  which  is  presented  by  the  central  im- 
pelling cavity  of  the  lower  Invertebrata ;  being  a  mere  prolonged  canal,  which 
at  its  posterior  extremity  receives  the  veins,  and  at  its  anterior  sends  forth  the 
arteries.  After  a  short  time,  however,  it  becomes  bent  upon  itself  (Plate  II., 
Fig.  27,  d) ;  and  it  is  soon  subdivided  into  three  cavities,  which  exist  in  all 
Vertebrata, — a  simple  auricle  or  receiving  cavity,  a  simple  ventricle  or  pro- 
pelling cavity,  and  a  bulbus  arteriosus  at  the  origin  of  the  aorta.  The  circu- 
lation is  at  first  carried  on  exactly  upon  the  plan,  which  is  permanently 
exhibited  by  Fishes.  The  Aorta  subdivides  into  four  or  five  arches  on  either 
side  of  the  neck ;  and  these  are  separated  by  slits  or  fissures,  much  resem- 
bling those  which  form  the  entrances  to  the  gill-cavities  of  Cartilaginous 
Fishes.  These  arches  reunite  to  form  the  descending  aorta,  which  transmits 
branches  to  all  parts  of  the  body.  Such  is  the  first  phase  or  aspect  of  the 
Circulating  Apparatus,  which  is  common  to  all  Vertebrata  during  the  earliest 
period  of  their  development,  and  which  may,  therefore,  be  considered  as  its 
most  general  form.  It  remains  permanent  in  the  class  of  Fishes;  and  in  them 
the  vascular  system  undergoes  further  development  on  the  same  type,  a  num- 
ber of  minute  tufts  being  sent  forth  from  each  of  the  arches,  which  enter  the 
filaments  of  the  gills,  and  serve  for  the  aeration  of  the  blood.  In  higher 
Vertebrata,  however,  the  plan  of  the  circulation  is  afterwards  entirely  changed, 
by  the  formation  of  new  cavities  in  the  heart,  and  by  the  production  of  new 
vessels;  these  changes  will  be  presently  described.  It  is  incorrect,  therefore, 
to  speak  of  the  vascular  arches  in  their  necks  as  branchial  arches ;  since  no 
branchiae  or  gills  are  ever  developed  from  them.  The  clefts  between  them 
may  be  very  distinctly  seen  in  the  Human  Foetus  towards  the  end  of  the  first 
month ;  during  the  second,  they  usually  close  up  and  disappear. 

941.  With  the  evolution  of  a  Circulating  apparatus,  adapted  to  absorb 
nourishment  from  the  store  prepared  for  the  use  of  the  Embryo,  and  to  con- 
vey it  to  its  different  tissues,  it  becomes  necessary  that  a  respiratory  apparatus 

Fig.  286. 


The  Amnion  in  process  of  formation,  by  the 
arching  over  of  the  serous  lamina;  a,  the 
chorion ;  b,  the  yolk-bag,  surrounded  by  se- 
rous and  vascular  laminae ;  c,  the  embryo ; 
d,  e,  and/,  external  and  internal  folds  of  the 
serous  layer,  forming  the  amnion  ;  §•,  incipi- 
ent allantois. 


a,/ 


Diagram  representing  a  Human  Ovum  in 
second  month ;  a.  1,  smooth  portion  of  cho- 
rion ;  a.  2,  villous  portion  of  chorion ;  k,  k, 
elongated  villi,  beginning  to  collect  into  Pla 
centa ;  6,  yolk-sac  or  umbilical  vesicle  ;  c,  em 
bryo;  /,  amnion  (inner  layer);  g,  allantois; 
A,  outer  layer  of  amnion,  coalescing  with 
cborion. 


718 


OF  REPRODUCTION. 


should  also  be  provided,  for  unloading  the  blood  of  the  carbonic  acid  with 
which  it  becomes  charged  during  the  course  of  its  circulation.  The  tempo- 
rary Respiratory  apparatus  now  to  be  described,  bears  a  strong  resemblance 
in  its  own  character,  and  especially  in  its  vascular  connections,  with  the  gills 
of  the  Mollusca;  which  are  prolongations  of  the  external  surface  (usually 
near  the  termination  of  the  intestinal  canal),  and  which  almost  invariably 
receive  their  vessels  from  that  part  of  the  system.  This  apparatus  is  termed 
the  Allantois.  It  consists  at  first  of  a  kind  of  diverticulum  or  prolongation  of 
the  lower  part  of  the  Digestive  cavity,  the  formation  of  which  has  been  already 
described.  This  is  at  first  seen  as  a  single  vesicle,  of  no  great  size  (Fig. 
285,  g) ;  and  in  the  Fretus  of  Mammalia,  which  is  soon  provided  with  other 
means  of  aerating  its  blood,  it  seldom  attains  any  considerable  dimensions. 
In  Birds,  however,  it  becomes  so  large  as  to  extend  itself  around  the  whole 
Yolk-sac,  intervening  between  it  and  the  membrane  of  the  shell ;  and  through 
the  latter  it  comes  into  relation  with  the  external  air.  The  preceding  diagram 
(Fig.  286)  will  serve  to  explain  its  origin  and  position  in  the  Human  ovum. 
The  chief  office  of  the  Allantois  in  Mammalia  is  to  convey  the  vessels  of  the 


Diagram  of  Human  Ovum,  at  the  time  of  formation  of  Placenta;  a,  muco-gelatinous  substance,  block- 
ing up  os  uteri ;  6,  6,  Fallopian  tubes ;  c,  c,  Decidua  vera,  prolonged  at  c  2,  into  Fallopian  tube  ;  d,  cavity 
of°uterus,  almost  completely  occupied  by  ovum;  e,  e,  angles  at  which  Decidua  vera  is  reflected  ;  /,  De- 
cidua serotina ;  g,  allantois;  h,  umbilical  vesicle ;  i,  amnion  ;  fc,  chorion,  lined  with  outer  fold  of  serous 
tunic. 


DEVELOPMENT  OF  THE  EMBRYO.  719 

embryo  to  the  Chorion;  and  its  extent  bears  a  pretty  close  correspondence 
with  the  extent  of  surface,  through  which  the  Chorion  comes  into  vascular 
connection  with  the  Decidua.  Thus,  in  the  Carnivora,  whose  Placenta  ex- 
tends like  a  band  around  the  whole  Ovum,  the  Allantois  also  lines  the  whole 
inner  surface  of  the  Chorion,  except  where  the  Umbilical  Vesicle  comes  in 
contact  with  it.  On  the  other  hand,  in  Man  and  the  Quadrumana,  whose 
Placenta  is  restricted  to  one  spot,  the  Allantois  is  small,  and  conveys  the 
foetal  vessels  to  one  portion  only  of  the  Chorion.  When  these  vessels  have 
reached  the  Chorion,  they  ramify  in  its  substance,  and  send  filaments  into  its 
villi;  and  in  proportion  as  these  villi  form  that  connection  with  the  uterine 
structure,  which  has  been  already  described,  do  the  vessels  increase  in  size. 
They  then  pass  directly  from  the  Foetus  to  the  Chorion;  and  the  Allantois, 
being  no  longer  of  any  use,  shrivels  up,  and  remains  as  a  minute  vesicle,  only 
to  be  detected  by  careful  examination.  The  same  thing  happens  in  regard  to 
the  Umbilical  vesicle,  from  which  the  entire  contents  have  been  by  this  time 
exhausted;  and  from  henceforth  the  Foetus  is  completely  dependent  for  the 
materials  of  its  growth,  upon  the  supply  it  receives  through  the  Placenta, 
which  is  conducted  to  it  by  the  vessels  of  the  Umbilical  Cord.  This  state  of 
things  is  represented  in  the  preceding  diagram. — The  Allantois  has  a  corre- 
spondence in  situation  with  the  Urinary  Bladder ;  but  it  is  only  the  lower 
part  of  it,  pinched  off,  as  it  were,  from  the  rest,  that  remains  as  such.  The 
duct  by  which  it  is  connected  with  the  abdomen  gradually  shrivels;  and  a 
vestige  of  this  is  permanent,  forming  the  Urachus  or  suspensory  ligament  of 
the  Bladder,  by  which  it  is  connected  with  the  Umbilicus.  Before  this  takes 
place,  however,  the  Allantois  is  the  receptacle  for  the  secretion  of  the  Corpora 
Wolffiana,  and  of  the  true  Kidneys,  when  they  are  formed. 

942.  It  will  be  seen  from  the  preceding  diagram,  that  the  Umbilical  Cord 
receives  an  investment  from  the  Amnion,  which  forms  a  kind  of  tubular 
sheath  around  it ;  it  is  continuous  at  the  Umbilicus  with  the  integument  of 
the  foetus ;  and  at  the  point  where  the  cord  enters  the  Placenta,  it  is  reflected 
over  its  internal  or  foetal  surface.  The  Amnion  (which  thus  forms  a  shut 
sac,  like  that  of  the  Pleura,  Arachnoid,  &c.)  contains  a  fluid  known  as  the 
liquor  amnii;  this  consists  of  water  holding  in  solution  a  small  quantity  of 
albumen  and  saline  matter,  and  resembling,  therefore,  very  diluted  serum. 
During  the  first  two  months  of  gestation,  the  Amnion  and  the  inner  surface 
of  the  Chorion  (which  is  really  the  reflected  layer  of  the  Amnion,  just  as  the 
lining  of  the  abdominal  cavity  is  formed  by  the  peritoneum)  are  separated  by  a 
gelatinous-looking  substance;  which  may  perhaps  be  considered  as  represent- 
ing the  white  of  the  egg  in  Birds ;  and  which  probably  aids  in  the  nutrition 
of  the  Embryo,  previously  to  the  formation  of  the  Placenta  (§  918).  This 
is  absorbed  during  the  second  month;  and  the  Amnion  is  then  found  imme- 
diately beneath  the  Chorion. — In  the  Umbilical  Cord,  when  it  is  completely 
formed,  the  following  parts  may  be  traced.  1.  The  tubular  sheath  afforded 
by  the  Amnion.  2.  The  Umbilical  Vesicle,  with  its  pedicle,  or  Omphalo- 
Enteric  duct.  2.  The  Vasa  Omphalo-Meseraica,  or  mesenteric  vessels  of 
the  Embryo,  by  which  the  Yolk  was  absorbed  into  the  body  of  the  Foetus; 
these  accompany  the  pedicle.  4.  The  Urachus,  and  remains  of  the  Allantois. 
5.  The  Vasa  Umbilicalia,  which,  in  the  later  period  of  gestation,  constitute 
the  chief  part  of  the  Cord.  These  last  vessels  consist  in  Man  of  two  Arte- 
ries and  one  Vein.  The  Arteries  are  the  main  branches  of  the  Hypogastric ; 
and  they  convey  to  the  Placenta  the  blood  which  has  to  be  aerated  and  other- 
wise revivified,  by  being  brought  into  relation  with  that  of  the  Mother.  The 
Vein  returns  this  to  the  Foetus,  and  discharges  a  part  of  it  into  the  Vena 
Portaj,  and  a  part  directly  through  the  Ductus  Venosus  into  the  Aorta. 


720  OF  REPRODUCTION. 

943.  A  change  in  the  type  of  the  Circulating  system  of  the  foetus,  from 
that  at  first  presented  by  it  (§  940),  takes  place  at  a  very  early  period.     At 
about  the  4th  week,  in  the  Human  Embryo,  a  septum  begins  to  be  formed  in 
the  Ventricle ;  and  by  >the  end  of  the  8th  week  it  is  complete.     The  Septum 
Auriculorum  is  formed  at  a  somewhat  later  period,  and  it  remains  incomplete 
during  the  whole  of  foetal  life  ;  it  is  partly  closed  by  the  valvular  fold  cover- 
ing the  Foramen  Ovale,  which  fold  is   developed  during  the  third  month. 
During  the  same  period,  a  transformation  takes  place  in  the  arrangement  of 
the  large  vessels  proceeding  from  the  Heart;  which  ends  in  their  assumption 
of  the  form  they  present  until  the  end  of  Festal  life;  and  this  undergoes  but 
a  slight  alteration,  when  the  plan  of  the  circulation  is  changed  at  the  moment 
of  the  first  inspiration.     The  number  of  Aortic  arches  on  each  side,  which 
was  five  at  first,  soon  becomes  reduced  in  the  Mammalia  to  three,  by  the 
obliteration  of  the  two  highest  pairs.     The  Bulbus  Arteriosus  is  subdivided, 
by  the  adhesion  of  its  walls  at  opposite  points,  into  two  tubes,  of  which  one 
becomes  the  Aorta  and  the  other  the  Pulmonary  Artery ;  and  of  the  three 
pairs  of  (branchial)  arches,  the  highest,  being  connected  with  the  Aortic  trunk, 
contributes  to  the  formation  of  the  Subclavian  and  Carotid  arteries ;  whilst  of 
the  middle  pair,  the  arch  on  the  right  side  is  obliterated,  the  other  becoming 
the  Arch  of  the  Aorta.     The  lowest  pair  arises  from  the  Pulmonary  trunk, 
and  forms  the  Pulmonary  artery  on  each  side ;  that  on  the  left  side,  however, 
goes  on  to  join  the  descending  Aorta  as  before,  and  thus  constitutes  the  Ductus 
Arteriosus. 

944.  The  following  is  the  course  of  the  circulation  of  the  blood  in  the 
Foetus.     The  fluid  brought  from  the  Placenta  by  the  Umbilical  Vein  is  partly 
conveyed  at  once  to  the  Vena  Cava  ascendens,  by  means  of  the  Ductus 
Venosus,  and  partly  flows  through  the  Vena  Portae  into  the  Liver,  whence  it 
reaches  the  ascending  Cava  by  the  Hepatic  Vein.     Having  thus  been  trans- 
mitted through  the  two  great  depurating  organs,  the  Placenta  and  the  foetal 
Liver,  it  is  in  the  condition  of  arterial  blood ;  but,  being  mixed  in  the  vessels 
with  that  which  has  been  returned  from  the  trunk  and  lower  extremities,  it 
loses  this  character  in  some  degree  by  the  time  that  it  arrives  in  the  Heart. 
In  the  right  Auricle,  which  it  then  enters,  it  would  be  also  mixed  with  the 
venous  blood  conveyed  by  the  descending  Cava;  were  it  not  that  a  very  curi- 
ous provision  exists,  to  prevent  (in  great  degree,  if  not  entirely)  any  such  fur- 
ther dilution-.     The  Eustachian  valve  has  been  found,  by  the  experiments  of 
Dr.  J.  Reid,*  to  serve  the  purpose  of  directing  the  arterial  blood,  which  flows 
upwards  from  the  ascending  Cava,  through  the  Foramen  Ovale,  into  the  left 
Auricle,  whence  it  passes  into  the  Ventricle;  whilst  it  also  directs  the  Venous 
blood,  that  has  been  returned  by  the  descending  Cava  into  the  right  Ven- 
tricle.    When  the  Ventricles  contract,  the  Arterial  blood  which  the  left  con- 
tains is  propelled  into  the  ascending  Aorta,  and  supplies  the  branches  that 
proceed  to  the  head  and  upper  extremities,  before  it  undergoes  any  admix- 
ture ;  whilst  the  Venous  blood,  contained  in  the  right  Ventricle,  is  forced 
through  the  Pulmonary  artery  and   Ductus  Arteriosus  into  the  descending 
Aorta,  mingling  with  the  arterial  current  which  that  vessel  previously  con- 
veyed, and  passing  thus  to  the  trunk  and  lower  extremities.     Hence  the  Head 
and  superior  extremities,  whose  development  is  required  to  be  in  advance  of 
that  of  the  lower,  are  supplied  with  blood  nearly  as  pure  as  that  which  returns 
from  the  Placenta :  whilst  the  rest  of  the  body  receives  a  mixture  of  this, 
with  what  has  previously  circulated  through  the  system ;  and  of  this  mixture 
a  portion  is  transmitted  to  the  Placenta,  to  be  renovated  by  coming  into  rela- 
tion with  the  maternal  fluid.     At  birth,  the  course  of  the  current  is  entirely 

*  Edinb.  Med.  and  Surg.  Journal,  vol.  xliii. 


DEVELOPMENT  OF  THE  EMBRYO. 

[Fig.  288. 

O     O 


721 


The  Foetal  Circulation;  1,  the  umbilical  cord,  consisting  of  the  umbilical  vein  and  two  umbilical 
arteries;  proceeding  from  the  placenta  (2) ;  3,  the  umbilical  vein  dividing  into  three  branches;  two  (4,  4) 
to  be  distributed  to  the  liver ;  and  one  (5),  the  ductus  venosus,  which  enters  the  inferior  vena  cava  (6) ; 
7,  the  portal  vein,  returning  the  blood  from  the  intestines,  and  uniting  with  the  right  hepatic  branch;  8, 
the  right  auricle ;  the  course  of  the  blood  is  denoted  by  the  arrow,  proceeding  from  8  to  9,  the  left  auricle ; 
10,  the  left  ventricle ;  the  blood  following  the  arrow  to  the  arch  of  the  aorta  (11),  to  be  distributed  through 
the  branches  given  off  by  the  arch  to  the  head  and  upper  extremities.  The  arrows,  12  and  13,  represent 
the  return  of  the  blood  from  the  head  and  upper  extremities  through  the  jugular  and  subclavian  veins, 
to  the  superior  vena  cava  (14),  to  the  right  auricle  (8),  and  in  the  course  of  the  arrow  through  the  right 
ventricle  (15),  to  the  pulmonary  artery  (16) ;  17,  the  ductus  arteriosus,  which  appears  to  be  a  proper  con- 
tinuation of  the  pulmonary  artery— the  offsets  at  each  side  are  the  right  and  left  pulmonary  artery  cut 
off;  these  are  of  extremely  small  size  as  compared  with  the  ductus  arteriosus.  The  ductus  arteriosus 
joins  the  descending  aorta  (18,  18),  which  divides  into  the  common  iliacs,  and  these  into  the  internal 
iliacs,  which  become  the  umbilical  arteries  (19),  and  return  the  blood  along  the  umbilical  cord  to  the 
placenta ;  while  the  other  divisions,  the  external  iliacs  (20),  are  continued  into  the  lower  extremities. 
The  arrows  at  the  termination  of  these  vessels  mark  the  return  of  the  venous  blood  by  the  veins  to  the 
inferior  cava.] 

changed  by  its  diversion  into  the  Lungs ;  which  takes  place  immediately  on 
the  first  inspiration.  The  Ductus  Venosus  and  Ductus  Arteriosus  soon  shrivel 
into  ligaments ;  the  Foramen  Ovale  becomes  closed  by  its  valve ;  and  the 
circulation,  which  was  before  carried  on  upon  the  plan  of  that  of  the  higher 
Reptiles,  now  becomes  that  of  the  complete  Bird  or  Mammal.  It  is  by  no 
means  unfrequent,  however,  for  some  arrest  of  development  to  prevent  the 
61 


722  OF  REPRODUCTION. 

completion  of  these  changes ;  and  various  malformations,  involving  an  imper- 
fect discharge  of  the  function,  may  hence  result.* 

945.  The  Alimentary  Canal  has  been  shown  to  have  its  origin  in  the  Yolk- 
sac  or  Umbilical  Vesicle ;  being  a  portion  pinched  off  (as  it  were)  from  that 
part  of  it,  which  is  just  beneath  the  Spinal  Column  of  the  Embryo  (§  937). 
At  first  it  is  merely  a  long  narrow  tube,  nearly  straight,  and  communicating 
with  the  Umbilical  Vesicle  at  about  the  middle  of  its  length ;  thus  it  may  be 
regarded  as  composed  of  the  union  of  two,  an  upper  and  a  lower  division. 
At  first,  neither  Mouth  nor  Anus   exists  ;  but  these  are  formed  early  in  the 
second  month,  if  not  before.     The  tube  gradually  manifests  a  distinction  into 
its  special  parts,  (Esophagus,  Stomach,  Small  Intestine,  and  Large  Intestine ; 
and  the  first  change  in  its  position  occurs  in  the  Stomach,  which,  from  being 
disposed  in  the  line  of  the  body,  takes  an  oblique  direction.     The  curves  of 
the  large  and  small  intestines  present  themselves  at  a  later  period.     It  is  at  the 
lower  part  of  the  small  Intestine,  near  its  termination  in  the  large,  that  the 
entrance  of  the  Omphalo-Enteric  duct  exists ;  and  a  remnant  of  this  canal  is 
not  unfrequently  preserved  throughout  life,  in  the  form  of  a  small  pouch  or 
diverticulum  from  that  part  of  the  intestine.     The  various  Glandular  structures 
connected  with  the  alimentary  canal,  originate  in  diverticula  from  its  walls,  in 
the  manner  already  described  in  regard  to  the  Liver  (§  826,  g).     The  Lungs 
and  Respiratory  apparatus  are  formed  in  like  manner,  as  diverticula  from  the 
(Esophagus  (§  757,  6,  c). 

946.  The  mode  in  which  the  chief  organs  of  the  Human  embryo  originate 
having  been  thus  described,  and  sufficient  particulars  in  regard  to  their  subse- 
quent development  having  been  already  given  under  distinct  heads,  it  is  un- 
necessary here  to  add  more  on  this  very  interesting  but  complex  subject;  be- 
cause for  practical  purposes  there  is  little  or  no  advantage  to  be  gained  from 
the  most  perfect  aquaintance  with  it.     The  most  important  of  all  the  facts  that 
have  come  under  our  review,  is  that  which  has  been  stated  as  in  the  highest 
degree  probable,  if  not  yet  absolutely  proved,  in  regard  to  the  relative  offices 
of  the  Male  and  Female  in  this  hitherto  mysterious  process.     According  to 
the  view  here  given,  the  Male  furnishes  the  germ;  and  the  Female  supplies 
it  with  Nutriment,  during  the  whole  period  of  its  early  development.     There 
is  no  difficulty  in  reconciling  such  a  doctrine  with  the  well-known  fact,  that 
the  offspring  commonly  bears  a  resemblance  to  both  parents  (of  which  the 
production  of  a  hybrid  between  distinct  species  is  the  most  striking  example) ; 
since  numerous  phenomena  prove  that,  in  this  earliest  and  simplest  condition 
of  the  organism,  the  form  it  will  ultimately  assume  very  much  depends  upon 
circumstances  external  to  it;  among  which  circumstances,  the  kind  of  nutri- 
ment supplied  will  be  one  of  the  most  important.t     Upon  the  same  principle 
we  may  account  for  the  influence  of  the  mental  condition  of  the  Mother  upon 
1ier  Offspring,  during  a  later  period  of  pregnancy.     That  such  influence  may 
occur,  there  can  be  no  reasonable  doubt.    "  We  have  demonstrative  evidence," 
says  Dr.  A.  Combe,^  "  that  a  fit  of  passion  in  a  nurse  vitiates  the  quality  of 
the  milk  to  such  a  degree,  as  to   cause  colic  and  indigestion  [or  even  death] 
in  the  suckling  infant.     If,  in  the  child  already  born,  and  in  so  far  independent 
of  its  parent,  the  relation  between  the  two  is  thus  strong,  is  it  unreasonable  to 
suppose  that  it  should  be  yet  stronger,  when  the  infant  lies  in  its  mother's 
womb,  is  nourished  indirectly  by  its  mother's  blood,  and  is,  to  all  intents  and 
purposes,  a  part  of  her  own  body?     If  a  sudden  and  powerful  emotion  of  her 
own  mind  exerts  such  an  influence  upon  her  stomach  as  to  excite  immediate 

*  See  Principles  of  General  and  Comparative  Physiology,  Chap.  vi. 
f  See  Principles  of  General  and  Comparative  Physiology,  §  665. 
J  On  the  Management  of  Infancy,  p.  76. 


DEVELOPMENT  OF  THE  EMBRYO.  723 

vomiting,  and  upon  her  heart  as  almost  to  arrest  its  motion  and  induce  fainting, 
can  we  believe  that  it  will  have  no  effect  on  her  womb  and  the  fragile  being 
contained  within  it  ?  Facts  and  reason,  then,  alike  demonstrate  the  reality  of 
the  influence:  and  much  practical  advantage  would  result  to  both  parent  and 
child,  were  the  conditions  and  extent  of  its  operations  better  understood." 
Among  facts  of  this  class,  there  is,  perhaps,  none  more  striking  than  that 
quoted  by  the  same  Author  from  Baron  Percy,  as  having  occurred  after  the 
siege  of  Landau  in  1793.  In  addition  to  a  violent  cannonading,  which  kept 
the  women  for  some  time  in  a  constant  state  of  alarm,  the  arsenal  blew  up 
with  a  terrific  explosion,  which  few  could  hear  with  unshaken  nerves.  Out 
of  92  children  born  in  that  district  within  a  few  months  afterwards,  Baron 
Percy  states  that  16  died  at  the  instant  of  birth ;  33  languished  for  from  8  to 
10  months,  and  then  died ;  8  became  idiotic,  and  died  before  the  age  of  5  years  ; 
and  2  came  into  the  world  with  numerous  fractures  of  the  bones  of  the  limbs, 
caused  by  the  cannonading  and  explosion.  Here,  then,  is  a  total  of  59  chil- 
dren out  of  92,  or  within  a  trifle  of  2  out  of  every  3,  actually  killed  through  the 
medium  of  the  Mother's  alarm  and  the  natural  consequences  upon  her  own 
organization, — an  experiment  (for  such  it  is  to  the  Physiologist)  upon  too  large 
a  scale  for  its  results  to  be  set  down  as  mere  "  coincidences."  No  soundly- 
judging  Physiologist  of  the  present  day  is  likely  to  fall  into  the  popular  error, 
of  supposing  that  marks  upon  the  Infant  are  to  be  referred  to  some  transient 
though  strong  impression  upon  the  imagination  of  the  Mother;  but  there  ap- 
pear to  be  a  sufficient  number  of  facts  on  record,  to  prove  that  habitual  mental 
conditions  on  the  part  of  the  Mother  may  have  influence  enough,  at  an  early 
period  of  gestation,  to  produce  evident  bodily  deformity,  or  peculiar  tendencies 
of  the  mind.  But  whatever  be  the  nature  and  degree  of  the  influence  thus 
transmitted,  it  must  be  such  as  can  act  by  modifying  the  character  of  the  nu- 
tritive materials  supplied  by  the  Mother  to  the  Fretus ;  since  there  is  no  other 
channel  by  which  any  influence  can  be  propagated.  The  absurdity  of  the 
vulgar  notion  just  alluded  to,  is  sufficiently  evident  from  this  fact  alone  ;  as  it 
is  impossible  to  suppose  that  a  sudden  fright,  speedily  forgotten,  can  exert 
such  a  continued  influence  on  the  nutrition  of  the  Embryo,  as  to  occasion  any 
personal  peculiarity.*  The  view  here  stated  is  one  which  ought  to  have  great 
weight,  in  making  manifest  the  importance  of  careful  management  of  the  health 
of  the  Mother,  both  corporeal  and  mental,  during  the  period  of  pregnancy ; 
since  the  constitution  of  the  offspring  so  much  depends  upon  the  impressions 
then  made  upon  its  most  impressible  structure. 

947.  It  is  frequently  of  great  importance,  both  to  the  Practitioner  and  to 
the  Medical  Jurist,  to  be  able  to  determine  the  age  of  a  Foetus,  from  the  physi- 
cal characters  which  it  presents ;  and  the  following  table  has  been  framed  by 
Devergiet  in  order  to  facilitate  such  determination.  It  is  to  be  remarked,  how- 
ever, that  the  absolute  Length  and  Weight  of  the  Embryo  are  much  less  safe 
criteria,  than  its  degree  of  Development, — as  indicated  by  the  relative  evolution 
of  the  several  parts,  which  make  their  appearance  successively.  Thus  it  is 
very  possible  for  one  child,  bom  at  the  full  time,  to  weigh  less  than  another, 
born  at  8  or  even  at  7  months  ;  its  length,  too,  may  be  no  greater ;  but  the 
position  of  the  middle  point  of  the  body  will  usually  afford  sufficient  ground 

*  For  some  valuable  observations  on  this  subject,  see  Montgomery  on  the  Signs  of  Preg- 
nancy.    Numerous  cases  have  been  recorded,  during  the  last  few  years  (especially  in  tJ 
Lancet  and  Provincial  Medical  Journal)  in  which  malformations  in  the  Infant  appeared 
distinctly  traceable  to  strong  impressions  made  on  the  mind  of  the  Mother,  some  months 
previously  to  parturition ;  these  impressions  having  been  persistent  during  the  remaining 
period  of  pregnancy,  and  giving  rise  to  a  full  expectation  on  the  part  of  the  Mother,  that 
child  would  be  affected  in  the  particular  manner  which  actually  occurred. 

t  Medecine  Legale,  vol.  i.  p.  495. 


724  OF  REPRODUCTION. 

for  the  determination ;  since,  during  the  two  latter  months  of  pregnancy,  the 
increasing  development  of  the  lower  extremities  throws  it  lower  down. 

Embryo  3  to  4  weeks.' — It  has  the  form  of  a  serpent ; — its  length  from  three  to  five  lines ; 
its  head  indicated  by  a  swelling ;  its  caudal  extremity  (in  which  is  seen  a  white  line,  indi- 
cating the  continuation  of  the  medulla  spinalis),  slender,  and  terminating  in  the  umbilical 
cord; — the  mouth  indicated  by  a  cleft; — the  eyes  by  two  black  points  ;  the  members  begin 
to  appear  as  nipple-like  protuberances ; — the  liver  occupies  the  whole  abdomen ; — the  bladder 
is  very  large.  The  chorion  is  villous,  but  its  villosities  are  still  diffused  over  the  whole  surface. 

Embryo  of  6  weeks. — Its  length  from  7  to  10  lines; — its  weight  from  40  to  75  grains; — 
face  distinct  from  cranium; — aperture  of  nose,  mouth,  eyes,  and  ears  perceptible: — head 
distinct  from  thorax  ; — hands  and  fore-arms  in  the  middle  of  the  length,  ringers  distinct;— 
legs  and  fee,t  situated  near  the  anus  ; — clavicle  and  maxillary  bone  present  a  point  of  ossifi- 
cation ; — distinct  umbilicus  for  attachment  of  cord,  which  at  that  time  consists  of  the  om- 
phalo-meseraic  vessels,  of  a  portion  of  the  urachus,  of  a  part  of  the  intestinal  tube,  and  of 
filaments  which  represent  the  umbilical  vessels.  The  placenta  begins  to  be  formed ; — the 
chorion  still  separated  from  the  amriion; — the  umbilical  vesicle  very  large. 

Embryo  of  2  months. — Length  from  16  to  19  lines;  weight  from  150  to  300  grains;  the 
elbows  and  arms  detached  from  the  trunk ; — heels  and  knees  also  isolated ; — rudiments  of 
the  nose  and  of  the  lips; — palpebral  circle  beginning  to  show  itself;— clitoris  or  penis  ap- 
parent; anus  marked  by  a  dark  spot;  rudiments  of  lungs,  spleen,  and  supra-renal  capsules; 
— caecum  placed  behind  the  umbilicus ; — digestive  canal  withdrawn  into  the  abdomen ; — 
urachus  visible ; — osseous  points  in  the  frontal  bone  and  in  the  ribs. — Chorion  commencing 
to  touch  the  amnion  at  the  point  opposite  the  insertion  of  the  placenta;  placenta  begins  to 
assume  its  regular  form ; — umbilical  vessels  commence  twisting. 

Embryo  of  3  months. — Length  from  2  to  2^  inches ; — weight  from  1  oz.  to  1  \  oz.  (Troy) ; 
— head  voluminous; — ^eyelids  in  contact  by  their  free  margin:  membrana  pupillaris  visible ; 
—mouth  closed; — fingers  completely  separated; — inferior  extremities  of  greater  length  than 
rudimentary  tail ; — clitoris  and  penis  very  long; — thymus  as  well  as  supra-renal  capsules 
present ; — caecum  placed  below  the  umbilicus ; — cerebrum  5  lines,  cerebellum  4  lines,  me- 
dulla oblongata  1^  line,  and  medulla  spinalis  £  of  a  line,  in  diameter; — two  ventricles  of 
heart  distinct. — The  decidua  reflexa  and  decidua  uterina  in  contact: — funis  contains  umbili- 
cal vessels  and  a  little  of  the  gelatine  of  Warthon ; — placenta  completely  isolated ; — umbilical 
vesicle,  allantois,  and  omphalo-mesenteric  vessels  have  disappeared. 

Foetus  of  4  months. — Length  5  to  6  inches; — weight  2^to3oz.; — skin  rosy,  tolerably 
dense; — mouth  very  large  and  open; — membrana  pupillaris  very  evident;  nails  begin  to 
appear: — genital  organ  and  sex  distinct ; — caecum  placed  near  the  right  kidney ; — gall-bladder 
appearing ; — meconium  in  duodenum ;  coecal  valve  visible ;  umbilicus  placed  near  pubis ; — 
ossicula  auditoria  ossified  ; — points  of  ossification  in  superior  part  of  sacrum ; — membrane 
forming  at  point  of  insertion  of  placenta  on  uterus; — complete  contact  of  chorion  with 
amnion. 

Fatus  of  5  months. — Length  6  to  7  inches ;  weight  5  to  7  oz. ; — volume  of  head  still  com- 
paratively great; — nails  very  distinct; — hair  beginning  to  appear; — skin  without  sebaceous 
covering; — white  substance  in  cerebellum;  heart  and  kidneys  very  voluminous ; — caecum 
situated  at  inferior  part  of  right  kidney ; — gall-bladder  distinct ; — germs  of  permanent  teeth 
appear ; — points  of  ossification  in  pubis  and  calcaneum ; — meconium  has  a  yellowish-green 
tint,  and  occupies  commencement  of  large  intestine. 

Fcetus  of  6  months. — Length  9  to  10  inches: — weight  1  Ib. ; — skin  presents  some  appear- 
ance of  fibrous  structure ; — eyelids  still  agglutinated,  and  membrana  pupillaris  remains ; — 
sacculi  begin  to  appear  in  colon; — funis  inserted  a  little  above  pubis; — face  of  a  purplish 
red; — hair  white  or  silvery; — sebaceous  covering  begins  to  present  itself; — meconium  in 
large  intestines; — liver  of  dark  red; — gall-bladder  contains  serous  fluid  destitute  of  bitter- 
ness-— testes  near  kidneys  ; — points  of  ossification  in  four  divisions  of  sternum  ; — middle 
point  at  lower  end  of  sternum. 

Fastus  of!  months. — Length  13  to  15  inches;  weight  3  to  4  Ibs.; — skin  of  rosy  hue,  thick, 
and  fibrous; — sebaceous  covering  begins  to  appear; — nails  do  not  yet  reach  extremities  of 
fingers ;— eyelids  no  longer  adherent; — membrana  pupillaris  disappearing; — a  point  of  ossi- 
fication in  the  astragalus ; — meconium  occupies  nearly  the  whole  of  large  intestine ; — valvulee 
conniventes  beginning  to  appear; — caecum  placed  in  right  iliac  fossa; — left  lobe  of  liver 
almost  as  large  as  right ;— gall-bladder  contains  bile ; — brain  possesses  more  consistency ; — 
testicles  more  distant  from  kidneys ; — middle  point  at  a  little  below  end  of  sternum. 

Fo3tus  of  8  months. — Length  14  to  16  inches; — weight  4  or  5  Ibs. ; — skin  covered  with 
well-marked  sebaceous  envelope ;  nails  reach  extremities  of  fingers ; — membrana  pupillaris 
becomes  invisible  during  this  month : — a  point  of  ossification  in  last  vertebra  of  sacrum ; — 
cartilage  of  inferior  extremity  of  femur  presents  no  centre  of  ossification  ; — brain  has  some 


PROPORTION  OF  SEXES.  725 

indications  of  convolutions; — testicles  descend  into  internal  ring; — middle  point  nearer  the 
umbilicus  than  the  sternum. 

Fcetus  of  9  months,  the  full  term. — Length  from  17  to  21  inches: — weight  from  5  to  9  Ibs., 
the  average  probably  about  6£  Ibs. ; — head  covered  with  hair  in  greater  or  less  quantity,  of 
from  9  to  12  lines  in  length; — skin  covered  with  sebaceous  matter,  especially  at  bends  of 
joints ; — membrana  pupillaris  no  longer  exists ; — external  auditory  meatus  still  cartilaginous  ; 
— four  portions  of  occipital  bone  remain  distinct; — os  hyoides  not  yet  ossified;  point  of  ossi- 
fication in  the  centre  of  cartilage  at  lower  extremity  of  femur ; — white  and  grey  substances 
of  brain  become  distinct; — liver  descends  to  umbilicus; — testes  have  passed  inguinal  ring, 
and  are  frequently  found  in  scrotum; — meconium  at  termination  of  large  intestine; — middle 
point  of  body  at  umbilicus,  or  a  little  below  it. 

948.  Even  at  Birth,  there  is  a  manifest  difference  in  the  physical  conditions 
of  Infants  of  different  sexes ;  for,  in  the  average  of  a  large  number,  there  is  a 
decided  preponderance  on  the  side  of  the  Males,  both  as  to  the  Length  and 
the  Weight  of  the  body. 

a.  The  Length  of  the  body  in  fifteen  new-born  infants  of  each  sex,  as  ascertained  by  Que- 
telet,*  was  as  follows : — 

Males.  Females.  Total. 

From  16  to  17  inchest  (French)                            2  4               6 

17  to  18             8  19  27 

-  18  to  19             28  18  46 

19  to  20             .....       12  8  20 

-  20  to  21             0  1               1 

From  these  observations,  the  mean  and  the  extremes  of  the  Lengths  of  the  Male  and  Female 

respectively,  were  calculated  to  be, — 

Males.  Females. 

Minimum      .         .       16  inches,  2  lines  16  inches,  2  lines 

Mean  18  6  18  li 

Maximum  19  8  20  6 

Notwithstanding  that  the  maximum  is  here  on  the  side  of  the  Female  (this  being  an  acci- 
dental result,  which  would  probably  have  been  otherwise,  had  a  larger  number  been  ex- 
amined), the  average  shows  a  difference  of  4^  lines  in  favour  of  the  Male. 

b.  The  inequality  in  the  Weight  of  the  two  is  even  more  remarkable;  the  observations  of 
M.  QueteletJ  were  made  upon  63  male  and  56  female  infants. 

Infants  weighing  from  Males.  Females.     Total. 

1  to  1$  kilog.§      .....  0  1                1 
1£  to  2 0  1               1 

2  to2i 3  7  10 

2J  to  3 13  14  27 

3  to  3i ,28  23  51 

3£to4 14  7  21 

4  to  4i         ......  5  3               8 

The  extremes  and  means  were  as  follows : — 

Males.  Females. 

Minimum           .         .         .         2-34  kilog.  1-12 

Mean         .         .         .         .         3-20  2-91 

Maximum          .         .         ,         4-50  4-25 

c.  The  average  weight  of  infants  of  both  sexes,  as  determined  by  these  inquiries,  is  3-05 
kilog.  or  6-7  Ibs. ;  and  this  corresponds  almost  exactly  with  the  statement  of  Chaussier,  whose 
observations  were  made  upon  more  than  20,000  infants.    The  mean  obtained  by  him,  with- 
out reference  to  distinction  of  sex,  was  6'75  Ibs. ;  the  maximum  being  11'3  Ibs.,  and  the  mini- 
mum 3-2  Ibs. ||     The  average  in  this  country  is  probably  rather  higher;  according  to  Dr. 
Joseph  Clarke,1T  whose  inquiries  were  made  on  60  males  and  60  females,  the  average  of 


*  Sur  L'Homme.  torn.  ii.  p.  8. 

f  The  French  inch  is  about  one-fifteenth  more  than  the  English. 
j  Op.  pit,  torn.  ii.  p.  35. 

§  The  kilogramme  is  equal  to  2  j  Ibs.  avoirdupois. 

||  These  numbers  have  been  erroneously  stated  in  many  Physiological  works ;  owing  to 
the  difference  between  the  French  and  English  pound  not  having  been  allowed  for. 
IT  Philosophical  Transactions,  vol.  Ixxvi. 

61* 


726  OF  REPRODUCTION. 

Male  children  is  7g-  Ibs.:  and  that  of  Females  6$  Ibs.  He  adds  that  children  which  at  the 
full  time  weigh  less  than  5  Ibs.  rarely  thrive ;  being  generally  feeble  in  their  actions,  and 
dying  within  a  short  time.  Several  instances  are  on  record,  of  infants  whose  weight  at  birth 
exceeded  15  Ibs.  It  appears  that  healthy  females,  living  in  the  country,  and  engaged  in 
active  but  not  over-fatiguing  occupations,  have  generally  the  largest  children ;  and  this  is 
what  might  be  expected  a  .priori  from  the  superior  activity  of  their  nutritive  functions. 

949.  Notwithstanding  .that,  in  any  ordinary  population,  there  is  a  decided 
preponderance  in  the  number  of  Females,  the  number  of  Male  births  is  con- 
siderably greater  than  that  of  females.  Taking  the  average  of  the  whole  of 
Europe,  the  proportion  is  about  106  Males  to  100  Females.  It  is  curious, 
however,  that  this  proportion  is  considerably  different  for  legitimate  and  for 
illegitimate  births ;  the  average  of  the  latter  being  only  102£  to  100,  in  the 
places  where  that  of  the  former  was  105|  to  100.  This  is  probably  to  be 
accounted  for  by  the  fact,  which  is  one  of  the  most  remarkable  contributions 
that  have  yet  been  made  by  Statistics  to  Physiology,  that  the  Sex  of  the  off- 
spring is  influenced  by  the  relative  ages  of  the  parents.  The  following  table 
expresses  the  average  results  obtained  by  M*  Hofacker*  in  Germany,  and  by 
Mr.  Sadlert  in  Britain ;  between  which  it  will  be  seen  that  there  is  a  manifest 
correspondence,  although  both  were  drawn  from  a  too.limited  series  of  observa- 
tions. The  numbers  indicate  the  proportion  of  Male  births  to  100  Females, 
under  the  several  conditions  mentioned  in  the  first  column. 

Hofacker.  Sadler. 

Father  younger  than  Mother     .          .      9O6     Father  younger  than  Mother     .         .       86-5 


Father  and  Mother  of  equal  age 
Father  older  by  1  to  6  years 
6  to  9 
9  to  18     . 
18  and  more 


90-0  Father  and  Mother  of  equal  age  .  94-8 

103-4  Father  older  by  1,  to  6  years      .  .  103-7 

124-7             .         .          6  to  11     .         .  .  126-7 

143-7             .         .        11  to  16     .         .  .  147-7 

200-0                              16  and  more  163-2 


From  this  it  appears,  that  the  more  advanced  age  of  the  Male  parent  has  a 
very  decided  influence  in  occasioning  a  preponderance  in  the  number  of  Male 
infants  ;  and  as  the  state  of  society  generally  involves  a  condition  of  this  kind 
in  regard  to  marriages,  whilst  in  the  case  of  illegitimate  children  the  same 
does  not  hold  good,  the  difference  in  the  proportional  number  of  male  births 
is  accounted  for.  We  are  not  likely  to  obtain  data  equally  satisfactory  in 
regard  to  the  influence  of  more  advanced  age  on  the  part  of  the  Female  parent ; 
as  a  difference  of  10  or  15  years  on  that  side  is  not  so  common.  If  it  exist 
to  the  same  extent,  it  is  probable  that  the  same  law  would  be  found  to  prevail 
in  regard  to  Female  children  born  under  such  circumstances,  as  has  been 
stated  with  respect  to  the  Male ; — namely,  that  the  mortality  is  greater  during 
embryonic  life  and  early  infancy,  so  that  the  preponderance  is  reduced. 

950.  There  appears  to  be,  from  the  first,  a  difference  in  the  viability  (or 
probability  of  life)  of  Male  and  Female  children ;  for,  out  of  the  total  number 
born  dead,  there  are  3  Males  to  2  Females :  this  proportion  gradually  lessens, 
however,  during  early  infancy  ;  being  about  4  to  3  during  the  first  two  months, 
and  about  4  to  5  during  the  next  three  months ;  after  which  time  the  deaths 
are  nearly  in  proportion  to  the  numbers  of  the  two  sexes  respectively,  until 
the  age  of  puberty.  The  viability  of  the  two  sexes  continues  to  increase 
during  childhood ;  and  attains  its  maximum  between  the  13th  and  14th  years. 
For  a  short  time  after  this  epoch  has  been  passed,  the  rate  of  mortality  is 
higher  in  Females  than  in  Males;  but  from  about  the  age  of  18  to  28,  the 
mortality  is  much  greater  in  Males,  being  at  its  maximum  at  25,  when  the 
viability  is  only  half  what  it  is  at  puberty.  This  fact  is  a  very  striking  one  ; 
and  shows  most  forcibly  that  the  indulgence  of  the  passions  not  only  weakens 
the  health,  but  in  a  great  number  of  instances  is  the  cause  of  a  very  premature 

*  Annales  d'Hygiene,  Oct.  1S29.  f  Law  of  Population,  vol.  ii.  p.  343. 


PROPORTION  OF  SEXES. 


727 


death.  From  the  age  of  28  to  that  of  50,  the  mortality  is  greater,  and  the 
viability  less,  on  the  side  of  the  Female ;  this  is  what  would  be  anticipated 
from  the  increased  risk,  to  which  she  is  liable  during  the  parturient  period. 
After  the  age  of  50,  the  mortality  is  nearly  the  same  for  both. 

a.  These  facts  have  been  expressed  by  Quetelet  in  a  form  which  brings  them  prominently 
before  the  eye  (Fig.  289).  The  relative  viability  of  the  Male  at  different  ages  is  represented 
by  a  curved  line;  the  elevation  of  which  indicates  its  degree,  at  the  respective  periods 
marked -along  the  base  line.  The  dotted  line  which  follows  a  different  curve,  represents 
the  viability  of  the  Female.  Starting  from  a,  the  period  of  birth,  we  arrive  at  the  maxi- 
mum of  viability  for  both  at  b  ;  from  this  point,  the  Female  curve  steadily  descends  towards 

Fig.  289. 


CL    b     70    15    20    26  30 


Diagram  representing  the  comparative  Viability  of  the  Male  and  Female  at  different  Ages. 

M,  at  first  very  rapidly,  but  afterwards  more  gradually;  whilst  the  Male  curve  does  not  de^ 
scend  quite  so  soon,  but  afterwards  falls  much  lower,  its  minimum  being  c,  which  corresponds 
with  the  age  of  25  years.  It  afterwards  ascends  to  rf,  which  is  the  maximum  of  viability 
subsequently  to  the  age  of  puberty;  this  point  is  attained  at  the  age  of  30  years,  from  which 
period,  up  to  50,  the  probability  of  life  is  greater  in  the  Male  than  in  the  Female.  In  the 
decline  of  life  there  seems  little  difference  for  the  two  sexes. 

951.  Similar  diagrams  have  been  constructed  by  Quetelet,  to  indicate  the 
relative  Heights  and  Weights  of  the  two  sexes  (Fig.  290). 

a.  In  regard  to  Height  it  may  be  observed,  that  the  increase  is  most  rapid  in  the  first 
year,  and  that  it  afterwards  diminishes  gradually;  between  the  ages  of  5  and  16  years,  the 
annual  increase  is  very  regular.     The  difference  between  the  Height  of  the  Male  and  I 
male,  which  has  been  already  stated  to  present  itself  at  birth,  continues  to  increase  during 
infancy  and  youth;  it  is  not  very  decided,  however,  until  about  the  15th  year,  after  which 
the  growth  of  the  Female  proceeds  at  a  much  diminished  rate,  whilst  that  of  the  Male  con- 
tinues in  nearly  the  same  degree,  until  about  the  age  of  19  years.     It  appears,  then,  that  the 
Female  comes  to  her  full  development  in  regard  to  Height,  earlier  than  does  the  Male.     J 
seems  probable,  from  the  observations  of  Quetelet,  that  the  full  height  of  the  Male  is  not 


728 


OF  REPRODUCTION. 


generally  attained  until  the  age  of  25  years.     At  about  the  age  of  50,  both  Male  and  Female 
undergo  a  diminution  of  their  stature,  which  continues  during  the  latter  part  of  life. 

6.  The  proportional  Weight  of  the  two  sexes  at  different  periods,  corresponds  pretty 
closely  with  their  height.  Starting  from  birth,  the  predominance  then  exhibited  by  the  Male 
gradually  increases  during  the  first  few  years ;  but  towards  the  period  of  puberty,  the  pro- 
portional weight  of  the  Female  increases ;  and  at  the  age  of  12  years,  there  is  no  difference 
between  the  two  sexes  in  this  respect.  The  weight  of  the  Male,  however,  then  increases 
much  more  rapidly  than  that  of  the  Female,  especially  between  the  ages  of  15  and  20 
years ;  after  the  latter  period,  there  is  no  considerable  increase  on  the  side  of  the  Male, 
though  his  maximum  is  not  attained  until  the  age  of  40;  and  there  is  an  absolute  diminu- 
tion on  the  part  of  the  Female,  whose  weight  remains  less  during  nearly  the  whole  period  of 
child-bearing.  After  the  termination  of  the  parturient  period,  the  weight  of  the  Female  again 
undergoes  an  increase,  and  its  maximum  is  attained  about  50.  In  old  age,  the  weight  of 
both  sexes  undergoes  a  diminution  in  nearly  the  same  degree.  The  average  Weights  of  the 
Male  and  Female,  that  have  attained  their  full  development,  are  twenty  times  those  of  the 
new-born  Infant  of  the  two  sexes  respectively.  The  Height,  on  the  other  hand,  is  about  Si- 
times  as  much. 

Fig.  290. 


70      15 


952.  The  chief  differences  in  the  Constitution  of  the  two  sexes  manifest 
themselves  during  the  period,  when  the  Generative  function  of  each  is  in  the 
greatest  vigour.  Many  of  these  distinctions  have  been  already  alluded  to ; 
but  there  are  others  of  too  great  importance  to  be  overlooked ;  and  these 
chiefly  relate  to  the  Nervous  System  and  its  functions.  There  is  no  obvious 
structural  difference  in  the  Nervous  System  of  the  two  sexes  (putting  aside 
the  local  peculiarities  of  its  distribution  to  the  organs  of  generation) ;  save  the 
inferior  size  of  the  Cerebral  Hemispheres  in  the  Female.  This  difference, 
which  is  not  observed  in  other  parts  of  the  Encephalon,  is  readily  accounted 
for  on  the  principles  formerly  stated ;  when  we  compare  the  physical  charac- 
ter of  Woman,  with  that  of  Man,  For  there  can  be  no  doubt  that — putting 
aside  the  exceptional  cases  which  now  and  then  occur — the  intellectual  pow- 
ers of  Woman  are  inferior  to  those  of  Man.  Although  her  perceptive  facul- 
ties are  more  acute,  her  capability  of  sustained  mental  exertion  is  much  less ; 
and  though  her  views  are  often  peculiarly  distinguished  by  clearness  and  deci- 
sion, they  are  generally  deficient  in  that  comprehensiveness  which  is  neces- 
sary for  their  stability.  With  less  of  the  volitional  powers  than  Man  pos- 
sesses, she  has  the  emotional  and  instinctive  in  a  much  stronger  degree.  The 
emotions  therefore  predominate;  and  more  frequently  become  the  leading 


PROPORTION  OF  SEXES.  729 

springs  of  action,  than  they  are  in  Man.  By  their  direct  influence  upon  the 
bodily  frame,  they  produce  changes  in  the  organic  functions,  which  far  sur- 
pass in  degree  anything  of  the  same  kind  that  we  ordinarily  witness  in  Man ; 
and  they  thus  not  unfrequently  occasion  symptoms  of  an  anomalous  kind, 
which  are  very  perplexing  to  the  Medical  practitioner,  but  very  interesting  to 
the  Physiological  observer.  But  they  also  act  as  powerful  motives  to  the 
Will ;  and,  when  strongly  called  forth,  produce  a  degree  of  vigour  and  deter- 
mination, which  is  very  surprising  to  those  who  have  usually  seen  the  indi- 
vidual under  a  different  aspect.  But  this  vigour,  being  due  to  the  strong 
excitement  of  the  Feelings,  and  not  to  any  inherent  strength  of  Intellect,  is 
only  sustained  during  the  persistence  of  the  motive,  and  fails  as  soon  as  it 
subsides.  The  feelings  of  Woman,  being  frequently  called  forth  by  the 
occurrences  she  witnesses  around  her,  are  naturally  more  disinterested  than 
those  of  Man;  his  energy  is  more  concentrated  upon  one  object;  and  to  this 
his  intellect  is  directed  with  an  earnestness  that  too  frequently  either  blunts 
his  feelings,  or  carries  them  along  in  the  same  channel, — thus  rendering  them 
selfish.  The  intuitive  powers  of  Woman  are  certainly  greater  than  those 
of  Man.  Her  perceptions  are  more  acute,  her  apprehension  quicker;  and 
she  has  a  remarkable  power  of  interpreting  the  feelings  of  others,  which 
gives  to  her,  not  only  a  much  more  ready  sympathy  with  these,  but  that 
power  of  guiding  her  actions  so  as  to  be  in  accordance  with  them,  which  we 
call  tact.  This  tact  bears  a  close  correspondence  with  the  adaptiveness  to 
particular  ends,  which  we  see  in  Instinctive  actions.  In  regard  to  the  infe- 
rior development  of  her  Intellectual  powers,  therefore,  and  in  the  predomi- 
nance of  the  Instinctive,  Woman  must  be  considered  as  ranking  below  Man ; 
but  in  the  superior  purity  and  elevation  of  her  Feelings,  she  is  as  highly 
raised  above  him.  Her  whole  character,  Psychical  as  well  as  Corporeal,  is 
beautifully  adapted  to  supply  what  is  deficient  in  Man;  and  to  elevate  and 
refine  those  powers,  which  might  otherwise  be  directed  to  low  and  selfish 
objects. 


APPENDIX. 


I.— ON  PHRENOLOGY. 

WITHOUT  entering  into  a  general  discussion  of  the  merits  of  the  system  of  Phrenology  at 
present  in  vogue,  which  would  be  misplaced  in  a  Treatise  like  the  present,  the  Author  feels 
it  desirable  to  express  the  opinion,  which  a  recent  careful  examination  of  the  chief  questions 
at  issue  between  Phrenologists  and  their  opponents  have  led  him  to  entertain. 

That  the  different  portions  of  the  Cerebral  mass  should  have  different  parts  to  perform  in 
that  wonderful  series  of  operations,  by  which  the  Brain  as  a  whole  becomes  the  instrument 
of  the  Mind,  does  not  seem  to  him  in  the  least  improbable.  Nor,  if  we  duly  consider  the 
general  plan  of  construction  of  the  nervous  centres  in  Vertebrated  animals,  is  it  a  legitimate 
objection  to  such  a  view,  that  there  is  no  mechanical  distinction  of  "  organs"  either  upon 
the  surface  or  in  the  interior  of  the  Cerebrum ;  for  in  the  Spinal  Cord  and  Medulla  Oblon- 
gata,  there  is  a  continuous  tract  of  grey  matter,  which  is  really  made  up  of  an  assemblage  of 
ganglia  having  dissimilar  functions,  although  there  are  no  external  indications  of  the  dis- 
tinctness of  these  ganglia.  Further,  it  appears  to  be  quite  legitimate  to  judge  of  the  com- 
parative powers  of  different  parts  of  the  Cerebrum,  or  of  the  same  portions  in  different  in- 
dividuals, by  their  comparative  sizes,-  due  allowance  being  made  for  other  circumstances  of 
difference.  And  if  the  development  of  a  particular  part  of  the  Cerebrum  were  constantly 
found  to  be  in  harmony  with  the  manifestation  of  a  certain  feature  of  psychical  character, 
there  would  be  strong  ground  for  regarding  such  a  part  as  the  instrument  of  the  mental 
operation  in  question.  The  attempt  to  establish  a  system  of  Cerebral  Physiology  by  com- 
parative observations  of  this  nature,  appears  to  the  Author,  therefore,  a  most  legitimate  one ; 
and  his  objections  to  the  present  system  of  Phrenology  are  based  only  on  the  very  imperfect 
manner  in  which  it  has  been  constructed;  the  foundations  on  which  it  rests  being  (in  his 
opinion)  of  a  very  insecure  character;  and  the  superstructure  having  been  built  up  of  the 
slightest  possible  materials.  The  following  are  the  chief  points  on  which  he  feels  called 
upon  to  express  his  dissent. 

1.  The  present  system  of  Phrenology  is  founded  only  on  comparative  observation  of  the 
psychical  character  and  cerebral  conformation  in  different  individuals  of  the  Human  species 
alone;  evidence  derived  from  Comparative  Anatomy  being  admitted  only  so  far  as  it  corre- 
sponds with  the  system  thus  constructed.     When  the  fundamental  importance  of  the  study 
of  Comparative  Anatomy  in  the  determination  of  the  functions  of  all  other  organs,  and  of 
other  parts  of  the  Nervous  System  itself,  is  duly  considered,  the  Author  cannot  regard  any 
system  of  Cerebral  Physiology  as  having  a  claim  to  a  place  in  a  scientific  treatise,  which  is 
not  founded  on  this  basis. 

2.  The  present  system  of  Phrenology  is  altogether  inconsistent  with  well-ascertained  facts, 
regarding  the  Comparative  Anatomy  and  Embryological  Development  of  the  Cerebrum.     It 
is  clearly  established  by  anatomical  research,  that  the  posterior  lobes  of  the  Cerebrum  are 
relatively  much  smaller  in  the  Quadrumana  than  they  are  in  Man,  and  that  they  disappear 
altogether  in  the  Carnivora,  not  a  vestige  of  them  being  discoverable  in  any  of  the  lower 
Mammalia ;  and  that  the  middle  lobes,  though  they  may  be  traced  in  the  lowest  of  the  Mam- 
malian Class,  are  altogether  wanting  in  Birds,  Reptiles,  and  Fishes.     The  Cerebrum  of  these 
animals,  therefore,  is  the  rudiment  of  the  anterior  lobe  only  of  that  of  Mammalia. — Further, 
it  has  been  lately  shown  by  Prof.  Retzius  (whose  researches  on  this  head  are  confirmatory 
of  those  of  Tiedemann,  at  the  same  time  being  more  full  and  precise),  that  the  development 
of  the  Cerebrum  of  the  Human  Embryo  takes  place  on  the  same  plan.     In  the  first  period, 
which  corresponds  with  the  second  and  third  months,  only  the  anterior  lobes  form;  in  the 
second  period  which  is  comprised  in  the  end  of  the  third  month,  in  the  fourth,  and  in  a 
small  portion  of  the  fifth,  the  two  middle  lobes  appear ;  and  it  is  not  until  the  latter  part  of 
the  fifth  month,  that  the  development  of  the  posterior  lobes  properly  commences.     They 
sprout,  as  it  were,  from  the  posterior  extremity  of  the  middle  lobes;  from  which  they  are 
divided,  on  the  brain  of  the  mature  foetus,  as  well  as  occasionally  in  that  of  adults,  by  a  dis- 
tinct furrow. — The  exact  mutual  confirmation  afforded  by  these  two  sources  of  knowledge, 


732  APPENDIX. 

proves  the  complete  inadmissibility  of  the  ordinary  Phrenological  interpretation  of  the  in- 
creased development  of  the  posterior  lobes  in  Man, — namely,  that  they  are  present  in  all 
Vertebrata,  but  that  they  are  pushed  backwards  in  the  higher  forms  by  the  increased  de- 
velopment of  the  anterior  portion  of  the  Cerebrum.  Now  as  the  Instincts  and  Propensities 
are  located,  according  to  the  present  system  of  Phrenology,  in  the  posterior  and  middle  lobes 
of  the  Cerebrum,  which  are  altogether  wanting  in  the  Oviparous  Classes  in  which  these  In- 
stincts and  Propensities  most  strongly  manifest  themselves,  it  would  appear  that  some  funda- 
mental error  must  exist  in  the  allocation. 

3.  The  present  system  of  Phrenology  takes  no  account  whatever  of  the  series  of  ganglionic 
masses,  which  lie  at  the  base  of  the  Cerebrum  in  Man,  and  which  are  thrown  into  the  shade 
(as  it  were)  by  its  excessive  development;  but  which  increase  in  relative  size  and  import- 
ance as  we  descend  the  scale,  until,  in  the  lower  Fishes  and  Invertebrata  generally,  they 
come  to  constitute  the  whole  Brain.     We  have  seen  that,  in  the  Cod,  the  rudiment  of  the 
Cerebrum  is  much  smaller  than  a  single  pair  of  these  ganglia, — the  Optic ;  and  as  this  rudi- 
ment does  not  possess  a  ventricle  (which  is  present  in  the  Sharks,  &c.,  dividing  the  rudiment 
of  the  hemisphere  which  arches  over  it,  from  the  corpus  striatum  which  lies  at  its  base),  it 
is  probably  to  be  regarded  as  not  really  analogous  to  any  part  of  the  Cerebrum  strictly  so 
called,  but  to  the  Corpus  Striatum,  which  (with  the  Thalamus)  constitutes  an  independent 
organ.     Thus  we  have  the  Cerebrum  entirely  disappearing  in  the  Osseous  Fishes ;  and  the 
whole  Brain  made  up  of  the  Sensory  Ganglia  and  the  Cerebellum. — In  the  Invertebrata,  not 
the  rudiment  of  a  Cerebrum  can  be  discovered;  the  cephalic  masses  of  nervous  matter  being 
made  up  of  ganglia  in  immediate  connection  with  the  organs  of  sense  and  motion.     It  is 
obvious,  therefore,  that  these  organs  must  be  of  primary  importance  as  centres  of  nervous 
action ;  and  that  the  functions  of  the  Cerebrum,  whatever  be  their  nature,  must  be  of  a  super- 
added^  and  of  a  non-essential  character. — The  view  which  the  Author  takes  of  these  pheno- 
mena will  be  found  at  large  in  the  Text.     He  regards  the  Sensory  Ganglia  as  the  seat  of 
Sensation  (each  kind  of  sensation  being  communicated  through  its  own  ganglion)  and  of 
the  simple  feelings  of  pleasure  and  pain  connected  with  those  sensations ;  and  also  as  the 
instrument  of  those  consensual  movements,  which  follow  immediately  and  necessarily  upon 
sensations.     To  this  category  he  would  refer  the  purely  Instinctive  actions,  which  are  imme- 
diately prompted  by  sensations,  which  seem  to  involve  no  idea  of  the  purpose  towards  which 
they  are  directed,  and  which  cannot  be  said  (the  idea  of  the  object  being  deficient)  to  spring 
from  a  desire  or  propensity.     Probably  all  or  nearly  all  the  actions  of  Invertebrata  and  of 
the  lower  Fishes  are  of  this  class.     The  emotions  and  propensities  of  Man  and  of  the  higher 
Mammalia,  which  form  the  chief  springs  of  action  in  them,  may  be  regarded  as  involving 
the  combined  operation  of  the  Sensory  Ganglia  and  the  Cerebrum ;  the  latter  affording  the 
ideas,-  whilst  the  former  invest  these  ideas  with  the  pleasure  or  pain,  which  gives  them  the 
form  of  passions,  desires,  or  propensities,  and  which  causes  them  to  become  the  moving 
springs  of  a  great  part  of  the  intellectual  operations,  which  are  purely  Cerebral.     The  action 
of  the  Cerebrum  in  the  passions,  emotions,  &c.,  is  limited,  therefore,  on  this  view  of  their 
nature,  to  its  instrumentality  in  furnishing  the  several  classes  of  ideas  to  which  those  emotions 
respectively  relate.     If  the  Phrenological  system  be  thus  modified,  there  will  no  longer  be 
the  same  difficulty  in  reconciling  it  with  the  facts  of  Comparative  Anatomy ;  since  in  those 
animals  which  are  unpossessed  of  the  posterior  lobes,  the  actions,  which  in  Man  and  the 
higher  Mammalia  result  from  desires  or  propensities  involving  a  distinct  idea  or  conception 
of  the  object,  may  be  purely  instinctive,  and  may  thus  be  performed  through  the  medium  of 
the  Sensory  Ganglia  alone,  without  the  participation  of  the  Cerebrum. 

4.  The  present  system  of  Phrenology  leaves  undetermined  a  very  large  proportion  of  the 
Cerebral  surface  in  Man, — probably  not  less  than  one-half;  namely  the  whole  series  of 
convolutions  covering  the  opposing  median  surfaces  of  the  hemispheres,  the  convolutions  of 
nearly  the  whole  of  the  base  of  the  Cerebrum,  and  those  of  the  fissure  of  Sylvius.     Yet 
not  the  slightest  ground  can  be  adduced  for  the  supposition  that  these  unappropriated  por- 
tions have  any  less  participation  in  the  operations  of  the  intellect,  the  exercise  of  the  moral 
feelings,  or  the  influence  of  the  animal  propensities,  than  have  the  external  and  superior 
portions  of  the  respective  lobes.     No  admission  of  the  imperfection  of  the  present  system 
of  Phrenology  can  be  a  sufficient  explanation  of  this  fact,  which  would  seem  to  indicate 
some  fundamental  error  in  the  method  employed ;  since  one  of  the  great  claims  which  is  set 
up  in  behalf  of  that  system  is  the  completeness  of  the  system  of  Psychical  philosophy  which 
it  presents  ;  so  that,  if  there  were  every  facility  for  observing  the  relative  development  of  the 
parts  of  the  Cerebral  surface  in  question,  there  would  seem  to  be  no  "organs"  left  to  distri- 
bute over  it. 

5.  If  it  be  urged,  however,  that  none  of  these  objections  are  sufficient  to  overthrow  the 
position,  now  established  by  a  long  course  of  observation,  that  a  constant  correspondence 
exists  in  Man  between  the  development  of  certain  parts  of  the  Cerebrum,  and  particular 
Psychical  characteristics,  and  that  the  present  system  must  consequently  be  true,  in  spite  of 
its  inconsistency  with  the  facts  of  Comparative  Anatomy,  it  becomes  necessary  to  inquire  in 


APPENDIX.  733 

more  detail  into  the  character  of  the  evidence  adduced  in  its  behalf. — The  following  objec- 
tions may  be  urged  upon  this  subject.  The  greater  part  of  the  observations  upon  which  the 
present  system  of  Phrenology  rests,  have  been  made  upon  crania  alone,  or  upon  casts  of 
crania;  not  upon  the  cerebrum  itself.  In  this  method  of  observation  there  are  many  falla- 
cies; especially  those  arising  from  the  indisputable  fact,  that  the  cerebrum  may  be  moulded 
in  such  a  manner  as  to  undergo  considerable  alteration  in  form,  without  any  change  in  its 
internal  structure  or  in  the  relative  development  of  its  several  parts.  And  an  extensive 
comparison  of  the  crania  of  different  nations  shows  that  their  differences  of  form  have  in 
many  instances  no  relation  whatever  to  their  psychical  character.  That  the  form  of  the  cra- 
nium is  to  a  certain  extent  independent  of  that  of  the  brain,  and  may  impress  itself  upon  its 
contents,  appears  further  from  a  comparison  between  the  cerebral  and  cranial  conformations 
of  different  species  of  animals.  It  is  found  that,  even  when  closely-allied  species  are  torn- 
pared  together,  similar  projections  of  the  cranium  may  cover  different  convolutions ;  the 
general  form  of  the  cranium  being  modified  by  its  instrumentality  in  other  functions,  espe- 
cially in  mastication,  and  by  its  position  upon  the  trunk  and  its  mode  of  muscular  connection 
with  it.  There  is  a  peculiar  uncertainty  attending  all  estimates  of  the  comparative  size  of 
the  Cerebellum,  from  inspection  of  the  exterior  of  the  cranium ;  for  the  observations  of  Prof. 
Retzius  upon  the  varieties  of  form  which  the  cranium  presents  in  different  races,  have  in- 
dicated this  fact  among  others, — that  the  position  of  the  cerebellum  may  vary  considerably, 
being  much  more  horizontal  in  one  case  and  more  vertical  in  another ;  so  that  cerebella  of 
the  same  size  may  exist  in  crania  having  very  different  amounts  of  occipital  protuberance; 
and  vice  versa. — Further,  after  dismissing  the  sources  of  error  already  mentioned,  there  yet 
remain  many,  arising  from  want  of  precision  in  the  cranioscopical  observations,  and  want  of 
opportunity  of  forming  a  correct  estimate  of  the  characters  of  the  individuals  whose  "  deve- 
lopments" have  been  examined.  The  difficulty  of  precisely  estimating  the  relative  sizes  of 
different  organs  by  any  system  of  measurement,  which  has  been  acknowledged  and  regretted 
by  candid  phrenologists,  often  leads  to  the  formation  of  very  different  inferences  from  the 
same  data,  as  the  Author  can  vouch  from  his  own  knowledge.  And  when  the  estimate  of 
the  character  has  been  formed  from  craniological  indications,  there  are  many  difficulties  in 
the  way  of  a  faithful  comparison  with  the  real  character  of  the  individual,  of  which  the 
manifestation  in  his  ostensible  conduct  can  generally  reveal  but  a  small  part.  Now  there 
can  be  little  doubt,  that  the  habit  of  attending-to  and  of  recording  coincidences  between  cere- 
bral developments  and  psychical  manifestations,  without  due  regard  to  the  cases  in  which 
there  is  no  coincidence,  has  been  far  too  prevalent  amongst  professed  phrenologists.  Unless 
the  failures  are  duly  chronicled  with  the  successes,  no  value  can  be  attached  to  any  series 
of  observations,  however  numerous  and  satisfactory.  Many  such  failures,  upon  points  in 
regard  to  which  there  could  be  no  misapprehension  or  evasion,  have  come  under  the  Author's 
knowledge ;  and  have  tended  to  prevent  his  reception  of  the  present  phrenological  system ; 
but  they  find  no  place  in  formal  treatises  on  Phrenology,  which  lead  their  readers  to  suppose 
that  the  coincidences  are  invariable.  The  connection  of  the  Sexual  propensity  with  the 
Cerebellum  has  been  usually  regarded  by  Phrenologists  as  one  of  the  best-ascertained  of  its 
whole  series  of  dogmata ;  and  yet  we  have  seen  how  little  this  determination  can  stand  the 
test  of  a  careful  scrutiny. 

Those  who  are  desirous  of  studying  the  Phrenological  system  at  present  in  vogue,  as  ex- 
pounded by  an  intelligent  and  unfettered  partisan,  may  be  referred  to  Mr.  Noble's  recent 
treatise,  entitled  "The  Brain  and  its  Physiology;"  whilst  the  objections  summed  up  in  this 
Appendix  are  stated  more  at  large  in  a  critique  on  that  work  in  the  British  and  Foreign  Me- 
dical Review,  for  October,  1846. 

II.— ON  ARTIFICIAL  SOMNAMBULISM  AND  MESMERISM. 

It  appears  to  the  Author  that  the  time  has  now  come,  when  a  tolerably  definite  opinion 
may  be  formed  regarding  a  large  number  of  the  phenomena  commonly  included  in  the  term 
"Mesmerism."  Notwithstanding  the  exposures  of  various  pretenders,  which  have  taken 
place  from  time  to  time,  there  remains  a  considerable  mass  of  phenomena,  which  cannot 
be  so  readily  disposed  of,  and  which  appear  to  him  to  have  as  just  a  title  to  the  attention  of 
the  scientific  Physiologist,  as  that  which  is  possessed  by  any  other  class  of  well-ascertained 
facts. 

Passing  over,  for  the  present,  the  inquiry  into  the  manner  in  which  these  effects  may  be 
induced,  the  Author  may  briefly  enumerate  the  principal  phenomena  which  he  regards  as 
having  been  veritably  presented  in  a  sufficient  number  of  instances,  to  entitle  them  to  be 
considered  as  genuine  and  regular  manifestations  of  the  peculiar  bodily  and  mental  condition 
under  discussion. 

1.  A  state  of  complete  Coma  or  perfect  insensibility,  analogous  in  its  mode  of  access  and 
departure  to  that  which  is  known  as  the  "  Hysteric  Coma,"  and  (like  it)  usually  distin- 
62 


734  APPENDIX. 

guishable  from  the  Coma  of  Cerebral  oppression  by  a  constant  twinkling  movement  of  the 
eyelids.  In  this  condition,  severe  surgical  operations  may  be  performed,  without  any  con- 
sciousness on  the  part  of  the  patient ;  and  it  is  not  unfrequently  found  that  the  state  of  tor- 
por extends  from  the  Cerebrum  and  Sensory  Ganglia  to  the  Medulla  Oblongata,  so  that  the 
respiratory  movements  become  seriously  interfered  with,  and  a  state  of  partial  asphyxia 
supervenes. 

2.  A  state  of  Somnambulism  or  Sleep-waking,  which  may  present  all  the  varieties  of  the 
natural  Somnambulism,  from  a  very  limited  awakening  of  the  mental  powers,  to  the  state 
of  complete  double  Consciousness  (§  500),  in  which  the  individual  manifests  all  the  ordi- 
nary powers  of  his  mind,  but  remembers  nothing  of  what  has  passed  when  restored  to  his 
natural  waking  state.     This  state  of  Somnambulism,  in  the  form  which  it  commonly  takes, 
is  characterized  by  the  facility  with  which  the  thoughts  are  directed  into  any  channel  which 
the  observer  may  desire,  by  the  principle  of  "  suggestion ;"  and  by  the  want  of  power,  on 
the  part  of  the  Somnambulist,  to  apply  the  teachings  of  ordinary  experience  to  the  correction 
of  the  erroneous  ideas  which  are  thus  made  to  occupy  the  mind.     In  these  particulars,  this 
condition  closely  corresponds  with  that  of  Dreaming;  and  differs  from  it  chiefly  in  the 
readiness  with  which  ideas  are  excited  through  the  ordinary  channels  of  sensation,  and  with 
which  the  bodily  powers  are  called  into  action  to  give  effect  to  the  ideas  thus  aroused.   The 
emotional  states  are  more  easily  brought  into  play,  than  the  purely  intellectual  operations. 
It  is  a  peculiar  characteristic  of  this  condition,  that  the  whole  attention  maybe  so  completely 
fixed  upon  one  object,  that  there  is  an  insensibility  to  all  impressions  unconnected  with  it, 
although  every  thing  which  bears  upon  it  is  fully  appreciated.     In  this  respect  there  is  a 
complete  correspondence  with  the  phenomena  of  ordinary  somnambulism ;  but  there  is  this 
difference, — that,  from  the  greater  subjection  of  the  mind  to  external  influences,  it  may  be 
more  readily  played  upon  (so  to  speak)  by  the  observer,  and  may  thus  be  exclusively  fixed 
upon  any  object  which  he  may  direct.     In  this  manner,  a  state  of  insensibility  to  pain  may 
Le  brought  about,  nearly  as  complete  as  that  which  occurs  in  the  comatose  state,  by  causing 
the  mind  to  be  strongly  and  exclusively  directed  towards  another  object.     This  condition 
finds  its  parallel  in  that  of  Reverie ;  in  which  strong  impressions  upon  the  body  may  be 
unfelt,  so  long  as  the  mind  is  engrossed  upon  some  different  train  of  thought. 

3.  A  frequent  phenomenon  of  this  condition,  and  one  which  has  its  parallel  in  Natural 
Somnambulism,  is  a  remarkable  exaltation  of  one  or  more  of  the  Senses,  so  that  the  indi- 
vidual becomes  susceptible  of  influences,  which,  in  his  natural  condition,  would  not  be  in 
the  least  perceived.     The  Author  has  referred  to  a  case  (§  532,  note)  in  which  such  an 
exaltation  of  the  sense  of  Smell  was  manifested ;  and  in  the  same  case,  as  in  many  others, 
there  was  a  similar  exaltation  of  the  sense  of  Temperature.     The  exaltation  of  the  Muscular 
Sense,  by  which  various  actions  that  ordinarily  require  the  guidance  of  vision,  are  directed 
independently  of  it,  is  a  common  phenomenon  of  the  Mesmeric  or  Artificial,  as   of  the 
Natural,  Somnambulism. 

4.  The  Muscular  system 'may  also  be  excited  to  action  in  unusual  modes,  and  with 
unusual  energy.     Notwithstanding  the  fallacy  of  many  of  the  cases  of  Cataleptic  rigidity 
which  have  been  publicly  exhibited,  the  Author  is  satisfied,  from  investigations  privately 
made,  of  the  possibility  of  artificially  inducing  this  condition.     A  slight  irritation  of  the 
muscles  themselves,  or  of  the  skin  which  covers  them, — as  by  drawing  the  points  of  the 
fingers  over  them,  or  even  wafting  currents  of  air  over  the  surface, — is  sufficient  to  excite 
the  tonic  muscular  contraction,  which  may  continue  in  sufficient  force  to  suspend  a  con- 
siderable weight,  for  a  longer  period  than  it  could  be  kept  up  by  any  conceivable  effort  of 
voluntary  power.     Further,  by  directing  the  attention  exclusively  to  any  set  of  muscles,  and 
by  impressing  the  mind  of  the  Somnambulist  with  the  facility  of  the  action  to  be  performed, 
a  very  extraordinary  degree  of  muscular  power  may  be  called  forth,  even  in  very  feeble 
individuals.     Thus  the  Author  has  seen  a  man  of  extremely  low  muscular  development  and 
small  stature,  not  only  lift  up  a  28  Ib.  weight  upon  his  little  finger,  but  even  swing  it  round 
his  head  with  the  greatest  apparent  facility, — having  been  previously  assured  that  it  was  as 
light  as  a  feather.     Upon  taking  up  the  same  weight  upon  their  own  little  fingers,  the 
Author  and  his  friends  were  very  glad  to  lay  it  down  after  raising  it  a  foot  from  the  ground  : 
and  the  subject  of  the  experiment  (a  respectable  middle-aged  man,  who  was  not  a  regular 
"  exhibitor,"  and  upon  whom  no  suspicion  of  any  kind  rested)  declined,  when  in  his  waking 
state,  even  attempting  to  lift  the  weight,  on  the  ground  that  it  would  strain  him  too  much. 

These  are  the  principal  phenomena  of  Artificial  Somnambulism,  in  regard  to  which  the 
Author  feels  his  mind  made  up.  He  does  not  see  why  any  discredit  should  be  attached  to 
them,  since  they  correspond  in  all  essential  particulars  with  those  of  states,  which  naturally 
or  spontaneously  occur  in  many  individuals,  and  which  he  has  had  opportunities  of  per- 
sonally observing,  in  cases  in  which  the  well-known  characters  of  the  parties  placed  them 
above  suspicion.  When  the  facility  with  which  the  mind  of  the  Somnambulist  is  played  on 
by  suggestions  conveyed  either  in  language  or  by  other  sensations  which  excite  associated 
ideas,  and  the  absence  of  the  corrective  power  ordinarily  supplied  by  past  experience,  are 


APPENDIX.  735 

duly  kept  in  view,  many  of  the  supposed  "  higher  phenomena"  of  Mesmerism  may  be 
accounted  for,  without  regarding  the  patient  on  the  one  hand  as  possessed  of  extraordinary 
powers  of  divination,  or  on  the  other  as  practising  a  deception.  Thus,  bearing  in  mind 
that  Somnambulism  is  an  acted  dream,  the  course  of  which  is  governed  by  external  impres- 
sions, it  is  easy  to  understand  how  the  subject  of  it  may  be  directed  by  leading  questions  to 
enter  buildings  which  he  has  never  seen,  and  to  describe  scenes  which  he  has  never  wit- 
nessed, without  any  intentional  deceit.  The  love  of  the  marvellous  so  strongly  possessed 
by  many  of  the  witnesses  of  such  exhibitions,  prompts  them  to  grasp  at  and  to  exaggerate 
the  coincidences  in  all  such  performances,  and  to  neglect  the  failures ;  and  hence  reports 
are  given  to  the  public,  which,  when  the  real  truth  of  them  is  known,  prove  to  have  been 
the  results  of  a  series  of  guesses,  the  correctness  of  which  is  in  direct  relation  to  the  amount 
of  guidance  afforded  by  the  questions  themselves.  In  like  manner  the  manifestations  of  the 
excitement  of  the  "  phrenological  organs"  seem  to  depend  upon  the  conveyance  of  a  sug- 
gestion to  the  patient,  either  through  his  knowledge  of  their  supposed  seat,  or  through'  the 
anticipations  expressed  by  the  by-standers.  Many  instances  are  recorded,  in  which  the 
intention  has  been  stated  of  exciting  one  organ,  whilst  the  finger  has  been  placed  upon  or 
pointed  at  another ;  and  the  resulting  manifestation  has  always  been  that  which  would  flow 
from  the  former.  It  does  not  hence  follow  that  intentional  deception  is  being  practised  by 
the  Somnambulist ;  since  the  condition  of  mind  already  referred  to,  causes  it  to  respond  to 
the  suggestion  which  is  most  strongly  conveyed  to  it.  Many  of  the  emotional  states  are 
readily  excitable,  by  placing  the  muscles  in  the  position  which  naturally  expresses  them ; 
thus  the  combative  tendency  may  be  called  forth  by  gently  flexing  the  fingers,  so  as  to 
double  the  fist ;  a  cheerful  hilarious  mood  may  be  induced  by  drawing  outwards  the  cor- 
ners of  the  mouth  as  in  laughter ;  and  this  may  be  exchanged  for  the  reverse  state  of  gloom 
and  ill-temper,  by  drawing  the  eyebrows  downwards  and  towards  each  other,  as  in  frown- 
ing. In  like  manner,  on  putting  the  hand  upon  the  vertex,  the  Somnambulist  draws  him- 
self up,  and  shows  the  manifestation  of  self-esteem ;  whilst  the  depression  of  the  head  into 
the  position  of  humility  calls  forth  the  corresponding  emotion.  Those  who  have  carefully 
observed  the  habits  of  infants  and  young  children,  must  perceive  the  accordance  of  these 
phenomena  with  those  which  continually  present  themselves  at  that  early  period  of  life, 
when  the  condition  of  the  mind  is  so  completely  under  the  government  of  suggestions  re- 
ceived from  without. 

In  regard  to  the  alleged  powers,  which  are  said  to  be  possessed  by  many  Somnambulists, 
of  reading  with  the  eyes  completely  covered,  or  of  discerning  words  enclosed  in  opaque 
boxes,  the  Author  need  only  here  express  his  complete  conviction  that  no  case  of  this  de- 
scription has  ever  stood  the  test  of  a  searching  investigation. 

The  modes  in  which  the  Artificial  Somnambulism  may  be  induced,  are  extremely  vari- 
ous. The  experiments  of  Mr.  Braid  have  shown,  that  one  of  the  most  effectual  is  the  con- 
tinued convergence  of  the  eyes  upon  a  bright  object,  held  at  a  small  distance  above  and  in 
front  of  them,  and  gradually  approximated  towards  them.  The  mere  steady  direction  of  the 
eyes  towards  a  distant  object,  in  persons  who  have  often  practised  the  former  method,  fre- 
quently serves  to  induce  the  state.  All  the  phenomena  described  in  the  preceding  para- 
graphs, have  been  witnessed  by  the  Author  in  individuals  thus  "  hypnotized ;"  and  he 
considers  that  this  curious  class  of  observations  cannot  be  better  prosecuted  than  by  the  em- 
ployment of  that  method.  He  is  not  yet  satisfied  that,  in  the  ordinary  "  Mesmeric  "  process, 
any  other  influence  than  this  is  really  exerted;  but  the  patient  is  sent  to  sleep  with  the 
dominant  idea  that  some  special  influence  is  exerted  by  the  Mesmerizer,  and  this  idea  affects 
all  the  subsequent  phenomena, — producing,  for  example,  in  some  cases,  insensibility  to  every- 
thing but  what  is  said  by  the  mesmerizer  or  by  an  individual  placed  by  him  en  rapport  with 
the  Somnambulist.  It  will  generally  be  found,  that  the  degree  of  this  supposed  connection 
depends  upon  the  notions  of  it  previously  formed  by  the  individual  Mesmerized.  In  the 
hypnotic  state,  there  is  an  entire  absence  of  any  such  peculiar  influence ;  the  Somnambulist 
being  equally  conscious  of  what  is  said  or  done  by  every  bystander. 

The  Author  may  refer  to  an  Article  in  the  British  and  Foreign  Medical  Review  for  April, 
1845,  as  on  the  whole  expressing  (although  not  written  by  himself)  his  opinions  upon  this 
curious  and  interesting  subject. 


INDEX. 


The  Numbers  refer  to  the  Paragraphs. 


A. 


ABEKRATION,  spherical,  535;  chromatic,  535 

Abnormal  forms  of  nutritive  process,  802 — 809 

Abortion,  929 

Abscess,  804 

Absorbent  cells,  181,  182 

vessels,  see  Lacteals,  and  Lympha- 
tics 

ABSORPTION 

Nutritive,  general  account  of,  107,  271 ;  by 
intestinal  surface,  672 — 675;  by  lacteals, 
672,  674;  by  blood-vessels,  673,  675;  by 
general  surface,  676—681  ;  by  skin,  676— 
679  ;  by  lungs,  678,  775,  776 
Interstitial,  by  lymphatics,  680, 681 ;  by  veins, 

681  & 
Of  gases  and  vapours  by  lungs,  775,  776 

Abstinence,  cases  of,  653 

Actinia,  nervous  system  of,  312,  313 

Activity,  varying,  of  nutritive  processes,  786 — 
791 

Adaptiveness  of  movements,  no  proof  of  sensa- 
tion, 306 

Addison,  Mr.,  his  observations  on  blood-cor- 
puscles referred  to,  151,  158,  159;  on  fibril- 
lation of  liquor  sanguinis,  136  ;  on  blood-ves- 
sels of  lungs,  758  ;  on  pus,  806 

Adhesion,  793,  794 

Adipose  tissue,  see  Fat-cells 

Aeration,  107  ;  see  Respiration 

Afferent  nerves,  289,  344 

Age,  influence  of,  on  pulse,  727  a ;  on  excretion 
of  carbonic  acid,  767  b  ;  on  excretion  of  urea, 
844;  on  activity  of  nutritive  processes,  786, 
812  ;  on  power  of  calorification,  893 

Air,  influence  of  respiration  on,  765 — 768 

Air-cells  of  lungs,  757,  758 

Albinoism.  80 

Albumen,  112;  composition  of,  114;  properties 
of,  113 — 115  ;  conversion  of  into  fibrine,  114, 
117,  153—158;  proportion  of  in  blood,  697, 
706;  purposes  of,  698;  diminution  of  in  blood, 
707  d;  predominance  of  in  tubercular  depo- 
sits, 878 

Albuminous  principles  of  food,  640,  857  ;  ap- 
plication of  in  the  animal  body,  642 

Albuminuria,  707  d 

Alcock,  Dr.,  his  experiments  on  nerves  of  taste, 
407 

Alcohol,  use  of  in  supporting  heat,  896  note 

Alfourous,  105 


Aliment,  causes  of  demand  for,  629—635;  see 
Food 

Alimentary  materials,  640 ;  see  Food 

Allantoin,  845  c 

Allantois,  origin  and  uses  of,  839  c 

Allen  and  Pepys,  their  researches  on  respira- 
tion, 765 

American  nations,  101 

Amphibia,  31 

Amphioxus,  110,  180;  nervous  centres  of,  425 

Anaemia,  707  c 

Andral,  M.,  on  amount  of  carbonic  acid  excret- 
ed, 767;  on  pathological  changes  in  blood, 
706,  707 

Animal  Heat,  see  Heat 

Animal  kingdom,  primary  subdivisions  of,  5 

Animal  magnetism,  Appendix  II. 

Animals,  distinguished  from  Plants,  1 — 4 

early  development  of,  3 

Anselmino,  on  solid  matters  of  cutaneous  ex- 
halation, 869 

Aplastic  deposits,  804,  807 

Aplysia,  12,  15;  nervous  system  of,  321 

Apoplexy,  decrease  of  fibrine  in,  707  c ;  death 
by,  814 

Arabian  nations,  94 

Arciform  fibres  of  medulla  oblongata,  353 

Area  pellucida,  936 

Areolar  tissue,  138,  139 

Areas,  comparative,  of  arteries,  710 

Arnott,  Dr.,  on  stammering,  619  ;  on  the  ven- 
ous circulation,  744  6 

Arteries,  distribution  of,  710;  area  of,  710; 
structure  and  properties  of,  728 — 732  ;  elas- 
ticity of,  729 ;  their  contractility,  proofs  of, 
730 ;  its  influence  in  regulating  the  circula- 
tion, 732;  their  tonicity,  731;  influence  of 
nerves  upon,  623,  732 

Articulata,  5,  16 — 19;  segmental  division  of, 
16  ;  animal  powers  of,  17  ;  nutrition  of,  18  ; 
bi-lateral  sympathy  of,  16;  respiration  and 
heat  of,  18;  nervous  system  of,  324—334 

Articulate  sounds,  612 — 619;  vowels,  613 — 
615;  consonants,  616,  617 

Articulation,  movements  of,  guided  by  sensa- 
tion, 611,  617 

Asphyxia,  nature  of,  778;  phenomena  of,  779; 
780 ;  referred  to,  738,  740,  814,  820 

Assimilation  in  Plants,  107;  in  Animals,  271, 
781 

Asthma,  spasmodic,  504,  759 

Atrophy,  789—791 


738 


INDEX. 


The  Numbers  refer  to  the  Paragraphs. 


Attention,  effects  of,  on  sensations,  519 — 521 
Auditory  ganglia,  in  Fishes,  357 ;  in  Man,  422 
Auditory  nerve,  446 ;  terminations  of,  in  ear, 

559 
Auricles  of  heart,  action  of,  718,  719 ;  capacity 

of,  723  b 

Automatic  actions,  438  a 
Azote,  absorption  and  exhalation  of,  766 ;  ex- 
cretion of,  in  urine,  819,  842—850;  respira- 
tion in,  769,  780 


B. 


BARRY,  Dr.  M.,  his  researches  on  the  blood- 
corpuscles  referred  to,  148  ;  his  embryologi- 
cal  researches  referred  to,  130,  900—918 

Barry,  Sir  D.,  his  experiments  on  the  venous 
circulation,  744  b 

Basement-membrane,  135 

Bat,  peculiar  sensibility  of,  526 

Batrachia,  31,  32;  metamorphosis  of,  32 

Beaumont,  Dr.,  his  experiments  and  observa- 
tions on  digestion,  637, 649,  657—660,  664— 
666 

Becquerel  on  the  heat  of  Plants,  889  a;  on  the 
heat  of  Animals,  891 ;  on  the  heat  of  Muscle, 
890 

Bee,  perfection  of  instinct  of,  336 ;  construction 
of  hexagonal  cell  by,  336  note ;  uneducability 
of,  429  b ;  temperature  of,  889  c 

Bell,  Sir  C.,  his  discoveries  referred  to,  344, 
349,351,376,377,433 

Bell,  Mr.  T.,  on  the  development  of  the  teeth, 
217  i  ;  on  secretion  after  death,  624 

Bellingeri,  on  the  Spinal  Cord,  -349 

Berger  and  Delaroche,  their  experiments  on 
Animal  Heat,  888 

Berber  race,  94 

Bernard,  M.  Ch.,  his  researches  on  digestion, 
658  b,  664  i,  669 

Bibra,  Von,  his  analyses  of  Bone,  196 ;  of  Teeth, 
212 

Bile,  secretion  of,  831 — 837 ;  composition  of, 
833 ;  amount  of,  834 ;  formed  from  venous 
blood,  831 ;  partly  an  excrementitious  fluid, 
836;  effects  of  non-elimination  of,  836; 
sources  of,  836 ;  purposes  of,  in  digestive 
process,  660,  670,  671,  835 

Birds,  33—41 ;  skeleton  of,  37,  38  ;  respiration 
and  heat  of,  33,  757,  889  c ;  covering  of,  36  ; 
instinctive  powers  and  intelligence  of,  39, 
479  ,  nutritive  system  in,  40;  bi-lateral  sym- 
metry in,  40 ;  development  of  young  in,  41  ; 
blood-corpuscles  of,  146  b,  149  ;  brain  of,  361 

Bischoff,  his  experiments  on  respiration,  768 

Bladder,  contraction  of,  390 

Blake,  Mr.,  his  experiments  on  the  Circulation, 
725 

Blind  persons,  acuteness  of  touch  in,  525 

Blondlot,  M.,  his  researches  on  digestion,  658 
6,  664  6 

BLOOD, 

Physical  and  vital  properties  of,  696—708 ; 
composed  of  liquor  sanguinis  and  cor- 
puscles, 696;  proportion  of  components, 
of,  in  health,  697  ;  purposes  of,  698  ;  total 
amount  of  in  body,  724 
Structure  of  Red  Corpuscles,  143,  144;  form 
of  corpuscles,  145, 146  ;  size  of  corpuscles, 


146;  chemical  constitution  of  corpuscles, 
147  ;  origin  of,  from  each  other,  148 ;  first 
production  of,  in  embryo,  149;  purposes 
of,  in  animal  economy,  150 
Colourless  corpuscles,  151,  152;  their  uses 

in  the  economy,  153 — 159 
Serum,  composition  of,  697  ;  milky,  697  e 
Coagulation  of,   699—705;   due  to  fibrine 
alone,  117,  118,  699;  an  act  of  vitality, 
118, 700, 701 ;  causes  influencing,  701,  702; 
proportions  of  serum  and  clot,  703 ;  bufiy 
coat,  causes  of,  704,  705 ;  composition  of, 
1 1 6  a ;  artificially  producible,  by  retarding 
coagulation,  699 

Pathological  changes  in,  706 — 708 ;  normal 
proportion  of  chief  constituents,  706 ;  in- 
fluence of  abstinence  and  hemorrhage, 
707 ;  increase  of  fibrine  in  inflammation, 
158,  707  a,  802;  deficiency  of  fibrine  in 
fever  and  hemorrhagic  diseases,  707  6 ;  in- 
crease of  corpuscles  in  plethora,  707  c  ; 
diminution  in  chlorosis,  anaemia,  &c.,  707 
c ;  decrease  of  albumen  in  Bright's  disease, 
707  d ;  general  depravation  of,  708 ;  imper- 
fect elaboration  of,  in  tuberculous  cachexia, 
807 

Changes  produced  in,  by  respiration,  769 — 
772;    difference  of  arterial  and    venous 
blood,  769;  excretion  of  carbonic  acid  from, 
769;  absorption  of  oxygen  by,  766  ;  gases 
extracted   from,  770 ;   change  of  colour, 
causes  of,  771,  772 ;  aeration  of,  by  gene- 
ral surface,  768 
Organization  of,  118,  700,  796 
Movement  of  through  vessels,  see  Circulation 
Blood-discs,  see  Corpuscles 
Blood-vessels,  see  Arteries,  Capillaries,  and 

Veins 

Bone,  192—207;  structure  of,  192 — 196;  form- 
ation of,  in  membrane,  197 ;  in  cartilage, 
198—200;  chemical  composition  of,  196; 
growth  of,  201 — 203 ;  regeneration  of,  204 
—207 
Bouchardat,  M.,  his  researches  on  digestion, 

670 

Bovista  giganteum,  153  a 
Bourgery,  M.,  his  observations  on  air-cells  of 

lungs,  757  a 

Bowman,  Mr.,  his  observations  on  muscular 

fibre,  226,  228,  231,  232,  590  a ;  on  mucous 

membrane,  176;  on  structure  of  the  kidney, 

839— 841 ;  on  fatty  liver,  929 

Brain,  see  Encephalon,  Cerebrum,  Cerebellum, 

&c. 
Brewster,  Sir  D.,  his  law  of  visible  direction, 

543 

Bright's  disease  of  the  Kidney,  707  d 
Brodie,  Sir  B.,  his  experiments  on  the  Par  Va- 

gum,  414,  a;  on  animal  heat,  890 
Bronchial  tubes,  contractility  of,  410,  759 
Brunner's  glands,  875 

Buchanan,  Dr.,  his  researches  on  the  blood  re- 
ferred to,  697  e 

Budd,  Dr.  W.,  his  cases  of  reflex  action  re- 
ferred  to,    365 — 369 ;    his   observations   on 
symmetrical  diseases  referred  to,  785,  882 
Buffy  coat,  704,  705 
Bulbus  arteriosus,  940,  943 
Bushmen,  70 


INDEX. 


739 


The  Numbers  refer  to  the  Paragraphs. 


C. 


CACOPLASTIC  deposits,  807 
Callus,  formation  of,  206 
Cancer,  809,  881 
Capacity  of  respiration,  764 
Capillary  vessels,  distribution  and  size  of,  219, 
220  ;  origin  of,  221,  222  ;  properties  of  their 
walls,  739  ;  absent  in  some  tissues,  220  ;  in- 
dependent   movement    of  blood    in,   733 ; 
proofs  of,  734—739 

Capillary  circulation,  733 — 742 ;  phenomena 
of,  734;  continues  after  cessation  of  heart's 
action,  735;  in  acardiac  foetus,  736;  stagna- 
tion of,  in  Asphyxia,  &c.,  738 ;  influence  of 
local  excitement  on,  737 ;  laws  regulating, 
739 — 741 ;  connection  of,  with  nervous  in- 
fluence, 742 

Carbonic  acid,  excretion  of,  749;  sources  of, 
750 — 754  ;  amount  of,  765 — 767 ;  made  sub- 
servient to  introduction  of  oxygen,  766 ; 
effected  through  the  skin,  768 ;  contained 
in  venous  blood,  770;  expiration  of,  in  hy- 
drogen, 769  ;  influence  of  on  colour  of  blood, 
771,  772;  effects  of  its  retention  in  the  sys- 
tem, 778— 780 

,  absorption  of,  by  lungs,  776 

Carnivorous  animals,  nutrition  of,  644 
Cartilage,  structure  of,  187 — 191 ;  composition 
of,  177,  a  ;  nutrition  of,  188,  191 ;  ulceration 
and  reparation  of,  191 ;  ossification  of,  198 
—200 

Catamenia,  908,  909 
Caucasian  race,  93 

Cells,  the  types  of  Organization,  259  ;  compose 
bulk  of  fabric  of  Vegetables,  106 — 109 ; 
origin  of,  122 — 124;  transformations  of, 
120, 121 

Origin  of  animal  structures  in,  110;  indi- 
vidual growth  of,  in  animals,  126,  127; 
history  of  development  of,  128—131 ; 
transformations  of,  132,  133,  223 ;  indi- 
vidual life  of,  126,  811;  continual  death 
of,  in  living  body,  108,  261,  811 ;  varying 
duration  of,  811,  812 

Functions  of,  general,  110,  126,  132,259; 
in  Absorption,  181,  182,  271,  672;  in  As- 
similation, 153,  154,  271 ;  in.  Secretion, 
174,  179,  278,  821—823;  in  Reproduc- 
tion, 174,281,902- 

Persistence  of,  in  animal  tissues,  180  ;  in 
pigment,  163,  164;  in  fat,  184;  in  shell, 
192 ;  in  epidermis  and  epithelium,  160 — 
174  ;  in  cartilage,  187 ;  in  muscle,  230 ; 
in  nerve,  245 

Replacement  of  by  Fibres,  134,  136 
Cellular  Plants,  106 
Cellular  tissue,  see  Areolar  tissue 
Cellulose,  Vegetable,  4,  111 
Cementum   of  teeth,  structure   of,  208,  211; 

composition  of,  212;  development  of,  216 
Centipede,  nervous  system  and  actions  of,  326 

—329 

Cerebellum,  340,  457—470 ;  of  Fishes,  357  ;  of 
Reptiles,  360;  of  Birds,  361 ;  of  Mammalia, 
362  ;  of  Human  embryo,  358,  359,  361;  re- 
lative dimensions  of,  457,  458,  461  ;  experi- 
ments on,  459,  460,  463;  observations  on 
size  of,  in  castrated  animals,  468,  469 ;  con- 
nection of,  with  motor  power,  459 — 465 ; 


with  sexual  instinct,  466 — 470 ;  pathological 
changes  in,  464,  465,  467;  phrenological  ac- 
count of,  470 

Cerebro-spinal  fluid,  476,  477 
Cerebrum,  340,  471 — 495;   general   structure 
of,  472—474 ;  of  Fishes,  357  ;  of  Reptiles, 
360  ;  of  Birds,  361  ;  of  Mammalia,  362;  of 
Human   embryo,    358,    359,   361  ;    general 
functions  of,  478 — 480;  relative  dimensions 
of,  481 — 484 ;  experiments  on,  485  ;  patholo- 
gical changes  in,  486  ;  connection  of,  with 
intelligence,  485—495 ;  with  the  will,  487, 
494 ;  distinct  functions  of  several  parts  of, 
Appendix  I. ;  peculiar  conditions  of,  in  sleep, 
somnambulism,  &c.,  499,  500,  Appendix  II. 
Ceruminous  glands,  872 
Chaetodon  rostratus,  490 
Change,  involved  in  idea  of  life,  254 
Cheselden's  case  of  cataract,  541 
Chimpanzee,  51 — 59 
Chlorosis,  707  c 
Chondrine,  composition  and  properties  of,  141, 

187  a 

Chorda  dorsalis,  ISO,  937 
Chordae  vocales,  603,  605,  607 
Chorea,  504  note 
Chorion,  production  of,  918;  subsequent  changes 

in,  918,  920—923 
Chossat,fiis  experiments  on  inanition,  652,  895, 

896 

Chyle,  674 ;  formation  of,  in  intestines,  660  :  ab- 
sorption of,  181, 672 ;  analysis  of,  691;  aspect 
of,  692 ;  changes  of,  in  progress  through 
lacteals,  692,  693;  globules  contained  in, 
their  nature  and  source,  155,  693 ;  their 
destination,  154 — 159,  693  ;  chyle  from  tho- 
racic duct,  693,  695;  relative  constitution 
of,  691 

Chyme,  formed  by  digestive  process,  657 — 660 
Chymification,  663 — 669;  a  chemical  action, 

667 

Cicatricula,  936 
Cilia,  171—173 
Cineritious  matter,  246 
CIRCULATION 

General  account  of,  272 ;  objects  of,  709  ; 
course  of,  in  Man,  710 ;  arterial  trunks, 
710;  capillaries,  219,  710;  veins,  710 
In  Plants,  712—714;  in  lower  Animals,  715, 

716 

Action  of  Heart,  719 — 727;  connection  of, 
with  nervous  system,  416,  576,  580, 
717;  rhythmical  movements  of,  717 — 719; 
sounds  of,  720,  721 ;  course  of  blood  in, 
722;  differences  of  two  sides,  723  ;  quan- 
tity of  blood  impelled  by,  724,  725;  force 
of  contractions,  726  ;  number  of  contrac- 
tions, 727 

Action  of  Arteries,  728—732;  their  elas- 
ticity and  contractility,  728 ;  influence  of 
their  elasticity,  729 ;  proofs  of  their  con- 
tractility, 730;  their  tonicity,  731 ;  influ- 
ence of  their  contractility,  732 
Independent  motion  in  capillaries,  733 — 
742 ;  proofs  of,  734—738 ;  stagnation  in, 
738,  740  ;  influence  of  capillaries  in  regu- 
lating amount  of  flow,  740  ;  contractility  of 
capillaries,  739;  general  principles  of  their 
action,  751 ;  influence  of  nerves  on  capil- 
lary circulation,  742 


740 


INDEX. 


The  Numbers  refer  to  the  Paragraphs. 

Motion  of  Blood  in  Veins,  743 — 745  ;  struc- 
ture and  properties  of  veins,  743  ;  causes 
of  flow  of  blood  through,  744;  influence 
of  gravity  upon,  745 

Peculiarities  of  circulation,  in  lungs,  746 ;  in 


portal  system,  685,  746  ;  in  cranium,  476, 
747;    in    erectile   tissue,   748;    in   fetus, 
early  state  of,  938 — 940  ;  subsequent  con- 
dition of,  943—944 
Disorders  of  circulation,  881 

Civilization,  influence  of,  on  development  of 
human  body,  87—90 

Clot,  of  Blood,  see  Crassamentum 

,  organization  of,  118,  119,  700, 

796 

Coagulable  lymph,  see  Liquor  Sanguinis 

Coagulation,  of  blood,  699—705;  due  to  fibrine 
alone,  117,  118,  699;  an  act  of  vitality,  118, 
700,  701 ;  circumstances  influencing,  701, 
702;  proportion  of  serum  and  clot,  703  ;  of 
chyle,  117,  693;  of  lymph,  694;  of  fibrine, 
117—119 

Coathupe,  Mr.,  his  experiments  on  respiration, 
764;  on  products  of  combustion  of  charcoal, 
776  note 

Coccochloris,  125 

Cochlea,  566 

Cockchafer,  19 

Coecilia,  31 

Coition,  act  of,  in  Male,  904  ;  in  Female,  911 

Cold,  degree  of,  endurable  by  Man,  987  ;  death 
by,  814,  895,  896  ;  means  of  producing,  in 
the  living  body,  897 ;  influence  of,  on  young 
animals,  893,  894 

Collard  de  Martigny,  his  experiments  on  re- 
spiration, 769,  774 

Colostrum,  854  a,  856 

Colour  of  Skin,  79—81  (see  Pigment-cells) 

Colourless  corpuscles  in  blood,  151—158 

Colours,  impressions  made  by,  552 ;  comple- 
mentary, 552;  deficiency  of  power  of  distin- 
guishing, 553 

Combe,  Dr.  A.,  quoted  from,  658  a,  666,  671 

Commissures  of  Brain,  474;  deficiency  of, 
474  a 

Complementary  colours,  552 

Conception,  aptitude  for,  909;  act  of,  911, 
927 

Conchifera,  nervous  system  in,  317,  318 

Concussion  of  brain,  effects  of,  580,  625 

Consciousness,  double,  500 

Consensual  movements,  335 ;  of  Articulata, 
336;  ofVertebrata,  337,  430— 436;  of  Eye- 
balls, 450—456 

Consonants,  616 

Contractility  of  Muscle,  573;  two  forms  of, 
574  ;  of  arteries,  730,  731 ;  of  Capillaries, 
739  ;  of  bronchial  tubes,  410,  759  (see  Irri- 
tability) 

Contraction  of  Muscle,  mode  of,  230,  575, 
576;  causes  of,  575,  576;  alternating  with 
relaxation,  575,577;  after  death,  578,  595— 
597  ;  dependent  on  arterial  blood,  583,  584  ; 
power  of,  the  same  at  different  degrees  of 
extension,  592;  energy  of,  in  Man,  598;  in 
Insects,  599 ;  rapidity  of,  600 

Convolutions  of  Brain,  472 

Convulsive  diseases,  502 — 504 

Cooling  power  of  cutaneous  exhalation,  897 

Cooper,  Sir  A.,  his  experiments  on  circulation 


through   cranium,  290 ;    his   researches  on 
mammary  gland  and  its  secretion,  853 

Coral,  6 

Corallines,  4 

Cornaro,  his  diet,  653 


Cornea,  structure  and  nutrition  of,  189 
Corpora  Albida,  914 

Cephaloidea,  914 

Lutea,  912-914 

Malpighiana,  of  Spleen,  683;   of  Kid- 
ney, 839  b 

Olivaria,  352,  353 

Pyramidalia,  352,  353 

Quadrigemina,  422,  436 

Restiformia,  352,  353 

Rubra,  914 

Striata,  423,  424 

Wolffiana,  26,  839  c 

Corpus  Callosum,  474 

Corpuscles,  Red,  of  Blood,  143 — 150;  struc- 
ture of,  143,  144;  form  of,  145,  146;  size  of, 
in  Mammalia,  146  a;  in  Birds,  1466;  in  Rep- 
tiles, 146  c;  in  Fishes,  146  d;  chemical  con- 
stitution of,  147;  origin  of,  148;  production 
of  in  embryo,  149;  large  in  fetus,  149;  uses 
of,  in  animal  economy,  150,  698;  proportion 
of  in  Blood,  697;  increase  of,  in  plethora, 
707  c;  diminution  of,  in  chlorosis,  707  c 

,  Colourless,  of  Blood,  151—159  ; 

characters  of,  151;  movement  of,  152;  uses 
of,  153—159 

of  Chyle,  155 
of  Lymph,  155 
of  Spleen,  6846 
of  Supra-Renal  Capsules,  686 
Cortical  Substance,  of  Brain,  472 

,  of  Kidney,  839  a 


Convulsive  diseases,  501 — 504 

Cotyledons  of  Ruminants,  921 

Coughing,  act  of,  381 

Cranium,  circulation  in,  476,  747;  forms  of  in 
different  races  of  Men,  81—87 

Crassamentum  of  Blood,  696 

Crowing  inspiration  of  infants,  504 

Crusta  petrosa  of  teeth,  208,  211,  212,  216 

Cruveilhier,  M.,  his  observations  on  heart,  718 
—722;  on  purulent  deposits,  837  a 

Crying,  act  of,  380 

Cryptogamia,  reproduction  in,  899 

Crystalline  lens,  190 

Currie,  Dr.,  case  of dysphagia  related  by,  677 

Cutaneous  follicles,  perspiratory,  868 — 870; 
sebaceous,  872 

Cuttle-fish,  nerves  of  arms  in,  322,  323;  ejec- 
tion of  ink  by,  438 

Cutis  anserina,  234 

Cyclostome  Fishes,  22 

Cylinder-epithelium,  170 


D. 


DARTOS,  contractility  of,  234 

Davy,  Dr.  J.,  his  researches  on  animal  heat, 
886 

Death,  somatic  and  molecular,  813 — 816,880; 
death  of  individual  cells,  811,  812 ;  by  as- 
phyxia, 814;  by  cold,  814,  895 ;  by  syncope, 
814;  by  necrsemia,  814;  by  retention  of  se- 
cretions, 278,  832, 842 


INDEX. 


741 


The  Numbers  refer  to  the  Paragraphs. 


Decay,  constant  in  Animal  body,  268, 632,  633, 

750  (see  Disintegration) 
Decidua,  formation  of,  919 
Decomposition,  continual,  in  living  beings,  268, 

632,  633  (see  Disintegration) 
Decussation,  of  optic  nerves,  445 
Defecation,  movements  concerned  in,  391,  392 
Degeneration,  of  nervous  structure,  263, 292 — 
296;  of  muscular  fibre,  239,  263,586;  of  ele- 
ments of  blood  into  pus,  800,  805 ;  into  tu- 
bercle, 807,  808 

Deglutition,  382 — 386;  a  reflex  action,  382, 
383  ;  nerves  concerned  in,  384,  385;  actions 
preceding,  386  a-c;  in  Polypes,  382 
Delaroche  and  Berger,  their  experiments  on 

Animal  Heat,  888 
Dental  groove,  217 
Dentine,  208;  structure  of,  210;  composition 

of,  212  ;  development  of,  213,  214 
Dermo-skeleton,20 
Despretz,  M.,  his  researches  on  animal  heat, 

892 
Devergie,  M.,  his  table  of  development  of  foetus 

at  different  ages,  947 
Diabetes,  879 

Diaphragm,  movements  of,  761 
Diathesis,  gouty,  878,  884 ;  saccharine,  879 ; 

tubercular,  878 
Diet-scale,  see  Food 
DIGESTION, 

General  account  of,  270 ;  in  lower  Animals, 
655;  alimentary  materials,  641 ;  their  re- 
spective destinations,  642 — 647;  inorganic 
substances,  648;  relative  digestibility  of 
different  kinds  of  food,  666;  importance  of 
bulk,  666 

Processes  of,  656 — 662 ;  mastication  and 
insalivation,  656 ;  deglutition,  656  ;  con- 
dition of  stomach  in,  during  health,  657  ; 
disorder  of,  658  ;  entrance  of  food  into 
stomach,  659 ;  movements  of  stomach, 
659;  expulsion  into  duodenum,  660;  pas- 
sage along  intestines,  661 ;  discharge  of 
faeces,  662 

Chemical  phenomena  of,  663 — 671 ;  compo- 
sition and  properties  of  gastric  juice,  664; 
its  chemical  action,  665,  667  ;  artificial  so- 
lution of  food,  668 ;  Wasmann's  researches 
on  pepsin,  668  ;  Bernard  and  Barreswill's 
researches,  669  ;  conversion  of  saccharine 
and  oleaginous  principles,  670,  671 
Influence  of  nerves  upon,  387,  413 — 415 
Interstitial,  according  to  Dr.  Prout,  681 
Digestive  cavity  in  lower  animals,  655  ;  origin 

and  formation  of,  937,  945 
Direction,  law  of  visible,  543 
Discs,  of  Blood,  see  Corpuscles 
Disintegration  of  Muscular  tissue,  239,  263, 

586  ;  of  Nervous  tissue,  263,  292—296 
Distance,  adaptation  of  eye  to,  536  ;  estimate 

of,  548 

Diving  animals,  778 
Dobson,  Mr.,  his  experiments  on  the  Spleen, 

685 

Domesticability  of  Animals,  39,  42 
Donne,  M.,  his  observations  on  Milk,  854  a, 

856  ;  on  temperature  in  disease,  886 
Doris,  gills  of,  755 
Dormant  Vitality,  255 
Dorsal  vessel  of  Articulata,  18 


Double  consciousness,  500 

Draper,  Professor,  on  Capillary  Circulation  713, 

741 

Dreaming,  499 
Dugong,  heart  of,  710 
Dulong,  M.,  his  researches  on  animal  heat, 

892 

Dumas,  his  analysis  of  fibrine,  114 
Duration  of  life  in  individual  parts,  810 — 812 
Dytiscus,  experiments  on,  328 
Dzondi,  on  deglutition,  656 


E. 


EAR,  general  action  of,  556;  comparative  struc- 
ture of,  557,  558;  distribution  of  auditory 
nerve  in,  559  ;  uses  of  membrana  tympani, 
563;  of  tympanic  cavity,  564;  of  labyrinth, 
565,  566  ;  of  external  ear  and  meatus,  567, 
568 

Echinodermata,  7—10;  shell  of,  192 

Educability,  of  Birds,  39,  479 ;  of  Mammalia, 
42,  480  ;  of  Man,  60 

Edwards,  Dr.,  his  experiments  on  respiration, 
769;  on  animal  heat,  888,  893,  894 

Efferent  nerves,  289,  344 

Egg,  see  Ovum 

Egg-shell,  Membrane  of,  118 

Ehrenberg,  on  limits  of  vision,  540 

Eighth  Pair  of  Nerves,  see  Glosso-pharyngeal, 
Par  Vagum,  and  Spinal  Accessory 

Ejaculatio  seminis,  372,  393,  904 

Elaboration  of  fibrine,  116, 154 — 159 

Elasticity  of  arterial  walls,  728,  729 

Elastic  tissues,  138, 139 

Electricity,  not  identical  with  nervous  power, 
297 

Embryo,  early  development  of,  915—917,  934 
— 945  ;  formation  of  germinal  mass,  935  ;  of 
germinal  membrane,  935,  936  ;  of  vertebral 
column,  937  ;  of  amnion,  938  ;  of  vascular 
area  and  umbilical  vessels,  938,  939 ;  of 
heart  and  branchial  arches,  940 ;  of  allan- 
tois,  941;  of  umbilical  cord,  941,  942;  later 
circulation  in,  943,  944 ;  influence  of  mo- 
ther on,  946  ;  table  of  development,  947 ; 
size  and  weight  of  at  birth,  948;  proportion 
of  males  and  females,  949  ;  relative  viability 
of,  950 

Embryonic  cell,  935,  936 

Embryonic  development,  of  brain,  358,  359, 
361 ;  of  cephalic  neryes,  420,  421 ;  of  Jungs, 
757  6,  c;  of  blood-corpuscles,  149  ;  of  liver, 
826  g;  of  kidney,  839  c;  of  heart,  940;  of 
circulating  apparatus,  940,  943,  944 ;  of  di- 
gestive cavity,  945 

Emissio  seminis,  372,  393 

Emotions,  influence  of  on  Intelligence  and 
Will,  440;  on  nutrition  and  secretion,  625 — 
628 

Emotional  actions,  437 — 440 

Enamel,  208;  structure  of,  209;  composition 
of,  212 ;  development  of,  215 

Endosmose,  271,  675 

Encephalon,  356  ;  comparative  anatomy  of,  357 
— 362;  weight  of,  in  proportion  to  entire 
body,  475  ;  proportions  of  different  parts, 
in  Fishes,  357—359 ;  in  Reptiles,  360  ;  in 
Birds,  361;  in  Mammalia,  362;  in  Human 


742 


INDEX. 


The  Numbers  refer  to  the  Paragraphs. 


embryo,  358,  359,  361 ;  supply  of  blood  to. 
476, 477 

Epidermic  tissues,  160 — 174;  epidermis,  161, 
162;  hair,  166— 168;  nails,  162,165;  epithe- 
lium, 169—174;  nutrition  of,  135,  161,  174; 
functions  of,  162,  174 

Epilepsy,  503 

Epithelium,  169 — 174;  the  real  secreting  struc- 
ture, 174;  cylindrical,  170;  tesselated,  170; 
ciliated,  171—173 

Erect  -vision,  543 

Erectile  tissue,  748 

Ethiopian  nations,  97 — 99 

Eustachian  tube,  uses  of,  564 

Eustachian  valve,  uses  of,  944 

Evans,  Dr.  Julian  on  the  structure  of  the  Spleen, 
683,  684 

EXCRETION, 

Objects  of,  275;  of  carbon,  275,  833  ;  of  ni- 
trogen, 276,  842;  result  of  decomposition, 
275,  81 9;  elements  of,  previously  in  blood, 
820,  832,  842 

Excretions,  outlets  of,  guarded  by  spinal  cord, 

O. '  1 

Exhalation,  in  Plants,  107;  by  lungs,  773,  774; 
influenced  by  mental  state,  774 ;  from  skin, 
870,  871 

Experiments  on  nerves,  fallacies  of,  302 — 306 

Expiration,  act  of,  761 

External  Ear,  uses  of,  567 

Exudation  corpuscles,  800,  805 

Eye,  general  action  of,  536 ;  an  optical  instru- 
ment, 536;  adaptation  of,  to  distance,  536, 
537 ;  defects  of,  538  ;  optical  powers  of,  540; 
consensual  movements  of,  450 — 456 


F. 


FACIAL  nerve,  406 

Faeces,  composition  of,  662 

Fallopian  tubes,  passage  of  Spermatozoa 
through,  911;  passage  of  ova  along,  911, 
918;  contractions  of,  produced  by  nervous 
agency,  393 

Falsetto  notes,  how  produced,  609 

Faraday,  Mr.,  optical  illusion  discovered  by, 
551 

Farre,  Dr.  A.,  discovery  of  Spermatozoa  in 
Ovum,  900 

Fat-cells,  184;  contents  of,  185;  uses  of,  186; 
formation  of,  186 

Fatty  livers,  829 

Feathers,  166 

Fecundation  in  Plants,  899;  in  Animals,  900 

Fever,  state  of  blood  in,  707  6 

Fenestra  ovalis,  557,  558 

rotunda,  558 

Fenwick,  Mr.,  his  experiments  on  absorption, 
673 

Ferments,  action  of,  in  digestion,  669 ;  in 
blood,  70S,  877 

Ferneley,  Mr.,  on  areas  of  arteries,  710  a 

Fibres,  origin  of,  118,  119,  136;  white,  138, 
140;  yellow,  138,  142;  mixture  of  in  areolar 
tissue,  138;  in  serous  and  synovial  mem- 
branes, 175;  in  mucous  membrane  and  skin, 
176,  177 

of  Muscle  and  Nerve,  see  Muscular 

Fibre,  and  Nervous  tissue 


Fibrillae,  ultimate  of  Muscle,  cellular  nature 
of,  230 

Fibrine,  composition  of,  114;  properties  of, 
114,  115;  coagulation  of,  117 — 119;  elabo- 
ration of,  117,  158,  159;  in  chyle,  693;  in 
blood,  696 — 705;  increase  of,  in  inflamma- 
tion, 158,  707  a,  802;  diminution  of,  in  fever 
and  hemorrhagic  diseases,  707  6  ;  imperfect 
elaboration  of,  in  strumous  diathesis,  807, 
878;  formed  at  expense  of  albumen,  114 — 
117;  effusion  of,  803;  organization  of,  119, 
700,  795,  796 

Fibro-cartilage,  187 

Fibrous  tissues,  simple,  138—142;  origin  of, 
118,119,136 

Fifth  Pair  of  nerves,  403,  404  ;  lingual  branch 
of,  404,  407;  development  of,  421;  influ- 
ence of,  o'n  organic  processes,  625 

Fishes,  26,  27;  skeleton  of,  26  ;  respiration  of, 
27,  755;  air-bladder  of,  27,  755;  kidneys 
of,  838,  839  c;  encephalon  of,  357,  358; 
circulation  in,  27,  716:  blood-corpuscles  of, 
146,  d 

Flourens,  M.,  his  experiments  on  the  nervous 
system,  432,  435,  436,  459 

Fluids,  absorption  of,  by  intestinal  surface, 
674,  675 ;  by  general  surface,  676,  677 ;  by 
veins,  675,  676;  by  lacteals,  674,675;  by 
lymphatics,  679 

Fly-catcher,  incubation  of,  41 

Foetus,  table  of  development  of,  947;  circula- 
tion in,  940,  943,  944;  brain  of,  compared 
with  that  of  lower  animals,  358,  359,  361 ; 
see  Embryo 

Follicles  of  Lieberkuhn,  874 

Food,  causes  of  demand  for,  629—635  ;  differ- 
ent kinds  of,  640,  648;  relative  amount  of 
azote  in  each,  647 ;  destination  of,  641 — 
646 ;  desire  for,  636—639 ;  relative  digesti- 
bility of  different  kinds  of,  666;  mechanical 
reduction  of,  656;  action  of  stomach  upon, 
657 — 659  ;  passage  of,  into  intestine,  660 ; 
passage  of,  through  intestinal  canal,  661  ; 
ejection  of  insoluble  portion  of,  662;  mode 
of  solution  of,  663—671 ;  smallest  quantity 
of,  on  which  life  can  be  supported,  653; 
greatest  quantity  that  can  be  devoured,  654; 
supply  of,  required  by  Man,  650,  651  ;  suf- 
ficiency of,  indicated  by  satiety,  649  ;  allow- 
ance of,  in  Navy,  650;  in  Milbank  Peniten- 
tiary, 651 ;  in  Edinburgh  House  of  Refuge, 
651 ;  in  Convict-ship,  651  ;  effects  of  insuf- 
ficient supply  of,  651,  652 

Form,  mode  of  acquiring  knowledge  of,  by 
touch,  523  ;  by  sight,  541,  542,  546,  547 

Fourth  pair  of  nerves,  405 

Fourth  ventricle,  346,  355 

Foville,  Dr.,  his  observations  on  brain,  486 

Freckles,  164 

Fremy,  M.,  his  analysis  of  Nervous  matter, 
249 

Frog,  metamorphoses  of,  31;  excitable  state 
of  spinal  cord  in,  401  a 

Functions,  260  ;  division  of,  into  organic  and 
animal,  261,  262;  connection  of,  263—267; 
of  Animal  life,  283—288 ;  of  Organic  life, 
268—282 

Fungous  growths,  809 


INDEX. 


743 


The  Numbers  refer  to  the  Paragraphs. 


G. 


GALL,  Dr.,  his  statements  respecting  the  Cere- 
bellum, 468 

Gall-bladder,  825  e,f 

Ganglia,  structure  of,  252,  245 — 247 

of  Special  sense  in  Vertebrata,  422 — 

425 

of  Sympathetic,  314,  342 

Gangrene,  804 

Gases,  contained  in  blood,  770;  absorption  of, 
by  lungs,  775—777 

Gasteropoda,  Nervous  System  of,  319—321 

Gastric  fluid,  composition  and  properties  of, 
664;  action  of,  665;  secretion  of,  propor- 
tional to  wants  of  the  system,  657 ;  not  de- 
pendent on  nervous  influence,  414,  415;  but 
affected  by  it,  626,  637 

Gelatine,  composition  of,  141 

,  of  cartilage,  187  a;  of  bone,  196 

Gelatinous  principles  of  food,  640;  application 
of,  in  the  animal  body,  642 

Gerber,  Prof.,  referred  to,  693  a 

Germinal  mass,  935 

membrane,  935;  serous  layer,  936; 

mucous  and  vascular  layers,  936 

spot,  905,  915 

vesicle,  905,  906,  915—917 

Gestation,  signs  of,  926;  ordinary  duration  of, 
928—930;  protracted,  931 ;  shortest  period 
of,  932 

Gills,  respiration  by,  755 

Glands,  general  structure  of,  821 — 823 

,  lymphatic,  682 

,  vascular,  683—690 

Globules,  see  Corpuscles 

Globuline,  composition  of,  147 

Glosso-pharyngeal  nerve,  functions  of,  384, 
407  ;  development  of,  420,  421 

Glycerine,  composition  and  properties  of,  185  a 

Glycicoll,  141  c 

Goodsir,  Mr.,  his  observations  on  primary 
membrane,  135;  on  the  Teeth,  217;  on 
Bone,  194;  on  ulceration  of  Cartilage,  191 ; 
on  Absorption,  181,  672;  on  Vascular 
Glands,  683;  on  Secretion,  822,  823;  on 
Milk-cells,  853  ft;  on  formation  of  Decidua, 
919  ;  on  structure  of  Placenta,  921—923 

Gouty  diathesis,  878,  884 

Graafian  follicle,  905,  912—914 

Grainger,  Mr.,  referred  to,  345,  367 

Granulation,  process  of,  799—801 

Gravity,  influence  of  on  Circulation,  745 

Greenhow,  Dr.,  his  plan  of  treating  burns, 
798 

Grey  matter  of  Nervous  system,  245,  246;  of 
Brain,  472 

Gryllotalpa,  nervous  system  of,  332 

Gulliver,  Mr.,  his  observations  on  blood-cor- 
puscles referred  to,  146,  149,  151,  156, 158; 
on  reparation  of  bone,  206 ;  on  chyle,  692 

Guy,  Dr.,  his  researches  on  the  Pulse,  727 


H. 

HABITUAL  movements,  438 

Haematine,  147 

Haematococcus,  125 

Hair,  characters  of,  in  different  human  races, 


82;  structure,  growth,  and  composition  of, 
166-168 

Hales,  Dr.,  his  experiments  on  the  circulation, 
726 

Hall,  Dr.  M.,  his  discoveries  on  the  Nervous 
system,  307,  345,  363,  365,  374,  375,  383, 
386,  392,  394,  398,  400,  505 ;  his  views  on 
muscular  irritability,  585,  589  6 

Haller,  his  doctrine  of  muscular  irritability, 
591 

Hastings,  Dr.,  his  experiments  on  capillary 
circulation,  717  a;  on  animal  heat,  890 

Haversian  canals,  193;  formation  of,  197, 199, 
201 

Hearing,  sense  of,  556 — 572 ;  physical  condi- 
tions of,  557,  560 — 562;  use  of  tympanum, 
563 ;  tympanic  cavity  and  Eustachian  tube, 
564;  chain  of  bones,  565;  labyrinth,  566; 
external  ear,  567 ;  auditory  nerve,  559 ; 
tones  produced  by  succession  of  sounds, 
569  ;  estimate  of  degree,  direction,  and  dis- 
tance of  sounds,  570;  rapidity  of  perception 
by,  compared  with  sight,  571 ;  uses  of,  in 
regulating  voice,  572,  611 

Heart,  111;  muscular  fibre  of,  234 ;  inherent 
contractility  of,  717;  rhythmical  movements 
of,  717— 719;  influence  of  nerves  on,  416, 
576,717  a-c;  sounds  of,  720,  721 ;  course 
of  blood  through,  722;  differences  of  struc- 
ture in  two  sides  of,  723 ;  difference  of 
valves,  723  c ;  quantity  of  blood  propelled 
by,  724,  725 ;  force  of  contraction  of,  726 ; 
number  of  contractions  of,  727;  various 
causes  influencing,  727  a-e ;  origin  of,  940  ; 
subsequent  development  of,  943 

Heat,  Animal,  amount  of,  developed  by  Man, 
885,  886;  in  disease,  886;  dependence  of 
on  formation  of  carbonic  acid,  889 — 892  ; 
development  of,  in  Plants,  889  a,  6;  in 
lower  animals,  889,  c;  effect  of  exercise  on, 
890  ;  partly  maintained  by  artificial  respira- 
tion, 896;  dependent  in  part  on  cutaneous 
respiration,  891 ;  chemical  theory  of,  892; 
heat  of  young  animals,  893  ;  variations  in 
power  of  generating,  at  different  seasons, 
894;  loss  of,  during  inanition,  895,  896  ;  pro- 
visions against  excess,  897 

Heat,  external,  influence  of,  on  incubation  of 
Birds,  41 ;  influence  of,  on  vital  actions  in 
general,  885;  extremes  of,  endurable  by 
Man,  887,  888;  power  of  resisting,  887, 
888,  897 

Heat,  sexual,  909 

Helmholtz,  his  observations  on  composition  of 
muscle,  238  6,  586 

Hemiopia,  545  note 

Hepatic  artery,  826  d 

cells,  183,  826 / 

duct,  826  c 

vein,  826  a,  e 

Herbivorous  animals,  nutrition  of,  645 

Hering,  experiments  of,  on  circulation,  724 

Heterologous  growths,  809,  881 

Hiccup,  act  of,  380. 

Hippuric  acid,  845  a 

Holland,  Dr.,  referred  to,  521 

Horny  matter,  composition  of,  162 

Horses,  cerebella  of,  468. 

Hottentots,  100 

Houston,  Dr.,  on  acardiac  fetus,  736 


744 


INDEX. 


The  Numbers  refer  to  the  Paragraphs. 


Hunger,  sense  of,  412,  636—638 

Hunter,  John,  on  muscular  tonicity,  593,  594; 
on  functions  of  lymphatics,  681  a,  c  ;  on  con- 
tractility of  arteries,  731 ;  on  union  by  ad- 
hesion, 794 

Hutchison,  Mr.,  on  capacity  of  respiration,  764 

Hydra,  9 ;  movements  of,  313  ;  reproduction 
of  parts  in,  ft,  792 

Hydrophobia,  502. 

Hymenoptera,  nerves  of  wings  of,  298 ;  in- 
stincts of,  336,  429 

Hypertrophy,  787,  788 

Hypoglossal  nerve,  functions  of,  418,  419  ;  de- 
velopment of,  420,  421 

Hysteria,  503 ;  remarkable  abstinence  in,  653 


I. 


IDEAS,  formation  of,  488. 

Idiots,  actions  of,  428,  474,  478,  484 

Improbability  of  Man,  60 

Inanition,  Chossat's  experiments  on,  895,  896 

Incontinence  of  urine,  401,  504 

Indo-European  nations,  95 

Indian  nations,  95 

Infants,  inferior  calorifying  power  of,  893,  932  a 

Inflammation,  increase  of  fibrine  of  blood  in, 
707  a,  802  ;  diminished  vitality  of  the- tissues 
in,  803  ;  results  of,  804—806 ;  generally  un- 
favourable to  reparation,  793,  799 — 801  ; 
prevention  of,  after  injuries,  798;  how  far 
concerned  in  deposition  of  tubercle,  808 

Ingestion  of  food,  actions  concerned  in,  382, 
656 

Insalivation,  656 

Insects,  Muscular  apparatus  of,  19  ;  strength  of, 
599;  instincts  of,  17,  429,479;  heat  deve- 
loped by,  889  c ;  nervous  system  of,  325— 
336  ;  reflex  actions  of,  328,  329  ;  consensual 
actions  of,  336;  circulation  in,  715;  respira- 
tion in,  755 

Inspiration,  act  of,  761 

Instinctive  actions,  characters  of,  428 

Instincts,  of  Articulata,  17,  336,429,479;  of 
Birds,  479  ;  of  Mammalia,  42,  480;  of  Man, 
428,  437—440,  484  ;  of  Cuttlefish,  438  ;  of  In- 
fants and  Idiots,  428,  484 

Intelligence,  of  Vertebrata,  2.3,  482  ;  of  Birds, 
479;  of  Mammalia,  480;  of  Man,  484;  gene- 
ral absence  of,  in  Invertebrata,  429  ;  seat  of, 
in  the  Cerebrum,  478 

Intercellular  passages,  218 

Intervertebral  nerves,  421 

Intestines,  peristaltic  movements  of,  388,  389; 
passage  of  food  through,  660,  661 ;  glandulse 
of,  661,  874—876 ;  secretions  of,  66],  877 

Intuitive  perceptions,  490 

Invertebrata,  general  absence  of  red  corpus- 
cles in,  150;  character  of  blood  of,  155 

Iron,  contained  in  food,  648  ;  in  blood-discs, 
147;  administration  of,  in  chlorosis,  707  c 

Irritability,  of  muscular  fibre,  see  Muscle 

lulus,  nervous  system  and  actions  of,  326,  329 


J. 


JENNINGS,  Mr., on  artificial  insufflation  of  lungs, 
760  a 


Jewish  nation,  80,  94 

Jones,  Dr.  Bence,  his  observations  on  phos- 
phatic  deposits,  295  note 

Jones,  Mr.  Wharton,  his  observations  on  blood- 
corpuscles,  152,  159  a ;  on  effects  of  inflam- 
mation, 704 ;  on  capillary  circulation,  780 


K. 


KELLIE,  Dr.,  his  experiments  on  circulation  in 
cranium,  747 

Kidneys,  general  function  of,  276,  819  ;  struc- 
ture of,  838,  839  ;  cortical  and  medullary  sub- 
stances, 839  a  ;  tubuli  uriniferi,  839  a  ;  Mal- 
pighian  bodies  in,  839  6;  circulation  in,  840; 
embryological  development  of,  839  c;  see 
Urine. 

Kiernan,  Mr.,  on  the  liver,  826,  827 

Kiesteine,  in  urine  of  pregnant  women,  859, 
926 

Knight,  Mr.,  observation  on  incubation  of  Fly- 
catcher, 41 

Kronenberg,Dr.,  on  roots  of  spinal  nerves,  304. 
344 


L. 


LACHRYMAL  gland,  865 


influence  of  nerv- 


•  secretion,  865; 
ous  system  on,  625,  626  ' 

Lacteals,  origin  and  distribution  of,  672  ;  func- 
tions of,  674,  675 

Lactic  acid,  present  in  stomach  during  diges- 
tion, 664  b ;  not  a  constituent  of  urine,  846 

Lacunae  of  bone,  193, 194 

Lamina  spiralis,  559 

Lamprey,  22 

Lane,  Mr.,  his  investigations  on  chyle,  693  a 

Language,  indication  of  affinity  of  races,  95  a 

Laryngeal  nerves,  378 

Larynx,  structure  of,  602—604  ;  action  of,  604 
—611 ;  muscles  of,  604,  605 

Laughing,  act  of,  380 

Lecanu,  M.,  his  analysis  of  blood,  697  a;  his 
observations  on  urine,  844 

Lehmann,  his  experiments  on  composition  of 
urine,  844,  849,  850 

Letellier,  M.,  his  researches  on  respiration, 
767  a 

Leuret,  M.,  his  observations  on  Cerebellum, 
468,  469 

Liebig,  Prof.,  on  digestive  process,  669 ;  on 
red  corpuscles  of  blood,  150  a;  on  compo- 
sition of  urine,  845 — 848;  on  uric  acid,  845 

Life,  idea  of,  involves  change,  254,  255  ;  dura- 
tion of,  in  individual  parts,  259,  810 — 812 

Ligaments,  structure  of,  140;  vocal,  140 

Ligamentum  nucha?,  140 

Light,  laws  of  refraction  of,  533—535  ;  rapidity 
of  perception  of,  compared  with  sound,  571 ; 
influence  of,  on  metamorphosis,  32;  effect 
of,  on  pupil,  395,  443;  influence  of,  on  pig- 
ment-cells, 164 

Lime,  an  element  of  animal  structures,  648 

Lingual  branch  of  fifth  pair,  407 

Lintott,  Mr.,  his  observations  on  the  teeth, 
217  c 

Liquor  sanguinis,  696  :  organization  of,  117 — 
119,795,796 


INDEX. 


745 


The  Numbers  refer  to  the  Paragraphs. 


Liver,  general  function  of,  275,  819 ;  univer- 
sally present  in  Animal  Kingdom,  825;  size 
and  form  of,  in  Vertebrata,  825  c,  d ;  gene- 
ral structure  of,  826;  component  cells  of, 
183,  826  /;  distribution  of  portal  vessels, 
826  6  ;  of  hepatic  artery,  826  d ;  of  hepatic 
vein,  826  a,  e;  of  hepatic  ducts,  826  c  ;  con- 
gestion of,  827  ;  cirrhosis  of,  828  ;  embryo- 
nic development  of,  826  g;  proportional 
size  of,  before  and  after  birth,  826  g,  830  ; 
secretion  of  bile  by,  831—836,  see  Bile; 
other  depurating  actions  of,  837 

Lizards,  29 

Locomotive  actions,  397 

Looped  terminations  of  Nerves,  240,  248 

Lungs,  structure  of,  in  lower  Vertebrata,  756  ; 
in  Man,  737  ;  development  of,  757  a-c  ;  ac- 
tion of,  in  respiration,  760  ;  capacity  of,  764; 
chemical  changes  in,  765 — 767 ;  exhalation 
by,  773,  774  ;  absorption  by,  775,  776 

Lymph,  composition  of,  691 ;  elaboration  of, 
682 ;  globules  in,  155,  694  ;  purposes  of,  154 
—159 

Lymph,  coagulable,  see  Liquor  Sanguinis 

Lymphatic  glands,  structure  of,  682 
gLymphatics,  distribution  of,  through  the  body, 
676 ;  function  of,  679,  680 ;  specially  con- 
cerned in  nutritive  absorption,  680,  681 


M. 


MACARTNEY,  Dr.,  his  views  on  the  reparative 
processes,  793—801 

Macleod,  Dr.,  on  first  production  of  blood-cor- 
puscles, 149  a 

Madden,  Dr.,  his  experiments  upon  absorption, 
677,  775 

Madder,  effect  of,  on  bones,  202 ;  on  teeth,  210 

Magnetism,  Animal,  Appendix  II. 

Magnus,  his  experiments  on  the  blood,  770 

Malayo-Polynesian  race,  103 

Malignant  growths,  809,  881 

Mammalia,  42—50  ;  sub-classes  of,  44 ;  skele- 
ton of,  46 ;  respiration  and  heat  of,  47,  757 ; 
subdivisions  of,  48  ;  brain  of,  362 ;  intelli- 
gence of,  42,  485 ;  blood-corpuscles  of,  146  a 

Mammary  gland,  853;  structure  of  glandulae, 
853,  a,  6 ;  development  of,  853,  c ;  structure 
of  in  male,  853  d  ;  secretion  of,  854—861 ; 
see  Milk 

Man,  characteristics  of,  51—61 ;  erect  attitude 
of,  51—57  ;  hand  of,  57  ;  other  distinctive 
characters  of,  58  ;  sensibility  and  locomotive 
power  of,  59  ;  intelligence  of,  60 ;  soul  of, 
61;  psychical  operations  in,  283 — 286;  sub- 
division of  into  races,  62,  63,  78 — 105;  com- 
mon origin  of,  91  ;  extremes  of  variation 
amongst  races  of,  72  ;  proper  food  of,  646 

Mantis,  nervous  system  of,  328 

Margarine,  composition  and  properties  of,  185  a 

Mastication,  656 

Matteucci,  his  experiments  on  Electricity,  297 

Mayer,  Prof.,  his  experiments  on  the  Spleen, 
685 

Median  nations,  95 

Medulla  Oblongata,  350  ;  structure  and  connec- 
tions of,  351 — 355  ;  ganglionic  character  of, 
355;  general  functions  of,  370,  374,  384; 
63 


centre  of  respiratory  movements,  374;  cen- 
tre of  acts  of  deglutition,  384,  385 

Medullary  matter  of  nervous  system,  structure 
of,  243,  246  ;  functions  of,  248 

Melolontha  vulgaris,  19 

Membrana  granulosa,  906,  912 

Membrana  tympani,  uses  of,  563 

Membrane,  basement  or  primary,  135  ;  fibrous, 
140;  mucous,  176 — 179;  serous  and  syno- 
vial,  175 

Membrane,  development  of  bone  in,  197 

Memory,  491 

Menstruation,  908,  909 

Metamorphosis  of  Batrachia,  &c.,  32,  630  a 

Milk,  peculiarity  of  as  alimentary  substance, 
642,  647  ;  general  composition  of,  854,  857  ; 
microscopic  characters  of,  854  a ;  constitu- 
ents of,  854  b  ;  proportion  of  constituents  in 
human  milk,  855  ;  in  milk  of  different  ani- 
mals, 858  ;  quantity  of,  860  ;  change  in  cha- 
racter of,  during  nursing,  856 ;  consequences 
of  retention  of,  859  ;  transference  of  secre- 
tion, 859  a;  foreign  substances  entering, 
861  ;  influence  of  emotions  on,  627  j  secre- 
tion of,  in  male,  853  c 

Milky  aspect  of  Chyle,  692 

serum,  697  e 

Milbank  Penitentiary,  651 

Mind,  elementary  operations  of,  487 — 495  ;  in- 
fluence of,  on  nutrition  and  secretion,  625 — 
628 

Mineral  ingredients  of  Food,  648 

Mitchell,  James,  case  of,  532 

Modelling  process,  797,  798 

Molecular  base  of  Chyle,  692 

Molecular  death,  813,  815,  816 

Mollusca,  5,  1 1 — 15 ;  deficiency  of  symmetry 
in,  11 — 13;  organs  of  locomotion  in,  13; 
organs  of  nutrition  in,  14  ;  blood  and  respira- 
tion of,  15  ;  shells  of,  192  ;  nervous  system 
in,  315 — 322 ;  circulation  in,  715 ;  respiration 
in,  755 

Mongolian  nations,  96 

Montgomery,  Dr.,  on  Corpus  luteum,  913, 914; 
on  placental  bruit,  925 

Mother,  influence  of,  on  foetus,  946 

Motions  of  Plants,  1,  230 

Motor  influence,  laws  of  propagation  of,  299 

Motor  linguae,  418,  419 

oculi,  405 

nerves,  determination  of,  300 — 303 

tract  of  Sir  C.  Bell,  351 

Mucous  layer  of  germinal  membrane,  936 

Mucous  Membrane,  176 — 179;  of  stomach, 
appearance  of,  in  health,  657;  in  disease, 
658;  intestinal,  structure  of,  661;  glandulae 
of,  in  stomach,  873  ;  in  intestines,  874 — 877 

Mucus,  properties  of,  179 

Mulder,  his  analysis  of  albumen  and  fibrine, 
114;  of  proteine  and  its  oxides,  116;  of 
gelatine,  141  a 

Mu'ller,  Prof.,  his  researches  on  vision  referred 
to,  519,537,543,  552;  on  hearing,  561,562, 
564;  on  blood,  699;  on  voice,  606—610;  on 
respiration,  769;  on  cancer,  809 

Muscular  Fibre,  223—240 ;  chemical  composi- 
tion of,  238 

Structure  of,  224,  225;  in  muscles  of  Animal 
life,  225—233 ;  arrangement  of,  in  fasci- 


746 


INDEX. 


The  Numbers  refer  to  the  Paragraphs. 


culi,  226  ;  composed  of  fibrillae,  226  ;  en- 
veloped in  sheath,  227  ;  form  and  com- 
parative dimensions  of,  228,  229 ;  structure 
of  ultimate  fTbrillse,  230 ;  state  of,  in  con- 
traction, 231,  233;  origin  of,  235,  236; 
reparation  of,  237;  supply  of  blood-vessels 
to,  239;  supply  of  nerves  to,  240;  struc- 
ture of,  in  Muscles  of  Organic  life,  234; 
development  of,  235,  236;  disintegration 
of,  from  use,  239,  263,  586 
Contractility  of,  573, 574 ;  irritability  of,  575 ; 
contraction  alternating  with  relaxation, 
576,  577;  persistence  of  after  death,  578  ; 
depressed  by  sedatives,  579;  by  violent 
nervous  impressions,  580,  581;  increased 
by  stimuli,  582;  dependent  on  arterialized 
blood,  583 — 585;  increased  by  habitual 
employment  of  particular  muscles,  587 ; 
diminished  by  want  of  action,  588 ;  in- 
fluence of  nerves  on,  589 — 591 ;  loss  of, 
from  section  of  nerves,  589  6,  c  ;  restored 
after  exhaustion,  589  d',  an  independent 
endowment,  591 ;  difference  of,  on  two 
sides  of  heart,  585}  the  same  at  different 
degrees  of  contraction,  592;  power  gene- 
rated by,  in  Man,  598  ;  in  Insects,  599 
Tonicity  of,  593 — 597 ;  effect  of  heat  and 

cold  upon,  593,  594 
Contraction  of,  after  death,  595—597 

Muscular  Contraction,  influence  of,  on  Circu- 
lation, 744  c 

Muscular  Sense,  433,  434 

Tension,  maintained  through  Spinal 

Cord,  398,  399 

Musk-deer,  blood-corpuscles  of,  146  a,  151 ; 
hair  of,  166 

Myolemma,  227,  235 

Myopia,  538 

Myxinoid  fishes,  180 

Myriapoda,  nervous  system  of,  326 ;  develop- 
ment of  head  of,  426  a 


NAILS,  162,  165 

Necraemia,  708 

Negro  races,  97 — 99 

Nerves,  origin  of,  in  ganglia,  246,247;  termi- 
nations of,  in  muscles,  239 ;  in  skin  and 
sensory  organs,  248 ;  mode  of  determining 
functions  of,  300 — 306 

Nervous  agency,  hypothesis  on  its  nature,  297; 
laws  of  its  transmission,  298,  299 ;  not  es- 
sential to  Nutrition  and  Secretion,  620,  624  ; 
influence  of,  on  organic  functions,  625 — 628 

Nervous  circle,  433 

Nervous  System,  general  functions  of,  289,  307 ; 
elementary  structure  of,  241 — 253 ;  fibrous 
matter  of,  242 — 244 ;  vesicular  matter  of,  245, 

246  ;  arrangement  of  fibres  in  ganglia,  246, 

247  ;  afferent  and  efferent  fibres  of,  289,  344  ; 
use  of  plexuses  in,  298;  isolated  course  of 
single  fibres,  298  ;  general  purposes  of,  307 
— 309;  dependence  of  its  activity  upon  supply 
of  blood,  290,  291 ;  functional  activity  of,  in- 
volves disintegration,  292 — 296;    nature  of 
changes  in,  297;  existence  of  in  lowest  Ani- 
mals, 311,   312;   general   recapitulation  of 


functions,  496 — 498;  peculiar  conditions  of, 
499 — 501  ;  pathological  states  of,  501 — 505 
Nervous  system  of  Radiata,  313,  314;  of  Mol- 
lusca,  315—323;  of  Articulata,  324—336;  of 
Vertebrata,  337—362 

Nervous  tissue,  241 — 253;  fibrous  element  of, 
242—244;  cellular  element  of,  245,  246;  re- 
lation of  two  structures  in,  246 — 248;  com- 
position of,  249;  nutrition  of,  250,  251;  first 
development  of,  252;  regeneration  of,  253; 
disintegration  of,  with  use,  292 — 296;  decay 
of,  when  not  employed,  442 
Neuro-skeleton,  20 

Newport,  Mr.,  his  observations  on  the  blood- 
corpuscles  of  Insects,  156;  on  their  nervous 
system,  325 — 330 ;  on  their  temperature, 
889  c;  on  development  of  head  of  Myria- 
poda, 426  a 

Nitrogen,  proportion  of,  in  different  articles  of 
food,   647;    exhalation  and    absorption    of, 
766;  respiration  in,  769,  780;  amount  of,  in 
blood,  770 
Nostoc,  125 

Nucleus,  124;  its  offices  and  metamorphosis, 
in  Plants,  124,  125;  in  Animals,  128—133 
Nucleus-filaments,  138  * 

NUTRITION, 

General  account  of,  273,  274,  781 ;  connec- 
tion of,  with  nervous  system,  279;  not  de- 
pendent upon  nervous  agency,  624;  but 
influenced  by  it,  624,  625 
Essential  nature  of,  782;  a  continuous  pro- 
cess of  cell  development,  782,  783;  select- 
ing power  of  individual  parts,  784,  785 
Varying  activity  of,  786—791  ;  affected  by 
age,  786 ;  hypertrophy,  787,  788  ;  atrophy, 
789—791 

Reparative  processes,  792 — 801 ;  reproduc- 
tion of  parts  in  lower  Animals,  792;  union 
by  first  intention,  793,  794;  organization 
of  liquor  sanguinis,  119,795;  organization 
of  blood,  700,  796;  modelling  process  of 
Dr.  Macartney,  797 ;  circumstances  favour- 
able to,  798 ;  granulation,  799—801 
Abnormal  forms  of  Nutritive  processes,  802 
— 809;  inflammation,  802 — 804;  suppura- 
tion, 805,  806;  tubercular  deposit,  807, 
808;  cancerous  growths,  809 
Varying  duration  of  different  parts,  810 — 
812;  limited  term  of  existence  of  cells, 
811 ;  variation  of,  with  period  of  life,  812 
Death,  or  Cessation  of  Nutrition,  813—816; 
somatic  and  molecular,  813 ;  somatic,  by 
Syncope,  814  ;  by  Asphyxia,  814;  by  Cold, 
814;  Molecular,  consequent  upon  somatic, 
815;  dependent  on  local  change,  816 


0. 


OBLIQUE  muscles  of  orbit,  451 
Oceanic  races,  102 
Octopus,  nerves  of,  298 
Odoriferous  glandulae,  872 
Odorous  matter  in  blood,  872 
Odours,  sensibility  to,  531,  532 
(Esophagus,  descent  of  food  through,  386,656 
Oleaginous  principles  of  food,  640,  641 ;  de- 
stination of,  in  Animal  body,  643 — 646,  671 


INDEX. 


747 


The  Numbers  refer  to  the  Paragraphs. 


Oleine,  composition  and  properties  of,  185  a 

Olfactory  lobes,  in  Fishes,  357—359  ;  in  Rep- 
tiles, 360;  in  Birds,  361;  in  Mammalia, 
362;  in  Man,  422 

Olfactive  nerves,  functions  of,  331 

Olivary  bodies,  350—354 

Omphalo-Meseraic  vessels,  939 

Optic  lobes,  in  Fishes,  357 — 359  ;  in  Reptiles, 
360;  in  Birds,  361  ;  in  Mammalia,  362;  in 
Human  embryo,  358,  359,  361;  in  Man, 
422  ;  functions  of,  436 

Optic  Nerve,  442 — 445  ;  an  excitor  of  motion, 
443;  decussation  of,  445;  termination  of,  in 
retina,  539 

Optic  Thalami,  423,424 

Orang  Outan  compared  with  Man,  50 — 60 

Orbicularis  muscle,  reflex  action  of,  394 

Orbit,  motor  nerves  of,  405;  muscles  of,  450, 
451 

Organic  fibres  of  Nervous  System,  244,  247, 
341 

Organization,  connection  of,  with  vital  proper- 
ties, 781  ;  incipient  in  liquor  sanguinis,  117 
— 119  ;  in  coagulable  lymph,  117,  795 

Organs  of  Sense,  their  mode  of  operation,  see 
Ear,  Eye,  &c, 

Ornithorrhyncus,  44;  mammary  gland  of,  821 

Ossification,  in  membrane,  197,  201 ;  in  carti- 
lage, 198—201 

Ostrich,  incubation  of,  41 

Otter-breed,  origination  of,  70 

Ovarium,  origin  of  ova  in,  905 — 907 ;  corpus 
luteum  in,  913,  914 

Ovisac,  907,  908 

Ovum,  component  parts  of,  905  ;  origin  of,  906, 

907;  maturation  of,  909  ;  arrival  of  sperma- 

,  tozoa  at,  900,  911 ;  discharge  of,  from  ovary, 

912;     first    changes    in,    915—918;     later 

changes  in,  934—947 

Owen,  Mr.,  on  blood-corpuscles  of  Siren,  145 
note;  on  structure  of  dentine,  210  ;  on  forma- 
tion of  dentine,  213,  214;  on  formation  of 
enamel,  215;  on  formation  of  crusta  petrosa, 
216 

Oxygen,  introduction  of,  in  respiration,  766; 
presence  of,  in  arterial  blood,  770,  771  ;  in- 
fluence of,  on  colour  of  blood,  771,  772  ; 
effect  of  respiration  of,  777 


P. 


PAGET,  Mr.  J.,  on  areas  of  arteries,  710  6 ;  on 
concentric  hypertrophy  of  heart,  597 ;  on 
absence  of  corpus  callosum,  474  a ;  on  ac- 
tion of  heart,  717 

Pancreas,  structure  of,  862  ;  secretion  of,  669, 
670,  863 

Papillae,  of  skin,  522  ;  of  tongue,  527 

Papuans,  104 

Paralysis  agitans,  381  note 

Paraplegia,  cases  of,  showing  reflex  action, 
366—369 

Parturition,  393,  928,  929 

Par  Vagum,  408 ;  the  excitor  of  respiratory 
movements,  374,  375;  influence  of,  on  pha> 
rynx,  385  ;  on  oesophagus,  386 ;  on  stomach, 
387  ;  chief  excitor  of  sense  of  hunger,  412, 


637 ;  effects  of  section  of,  on  lungs,  409 — 
411 ;  on  digestion,  412 — 415;  on  heart,  416 

Pelagian-Negro  races,  104 

Pelvis,  various  forms  of  in  different  races  of 
Men,  88 

Pepsin,  668,  669 

Perception,  488—490 

Perenni-branchiate  Batrachia,  32 

Peristaltic  movements  of  intestines,  388,  575, 
660;  independent  of  nervous  agency,  388; 
influenced  by  spinal  cord  through  sympa- 
thetic, 388,  389 

Peyerian  glands,  874,  876 

Philip,  Dr.  Wilson,  his  experiments  on  the  Par 
Vagum,  414,  415;  on  connection  of  Nervous 
System  with  heart,  717  a;  with  Capillaries, 
742  ;  on  animal  heat,  890 

Phosphorus,  an  element  of  food,  648  ;  in  pro- 
teine-compounds,  113,  114;  oxidation  of,  in 
system,  847 

Photophobia,  431 

Phrenological  doctrines  regarding  Cerebellum, 
466—470 

Phrenology,  observations  on,  Appendix  I. 

Physiology,  objects  of  the  science,  and  mode 
of  pursuing  it,  Introduction. 

Pigment-cells,  163,  164 

Piementum  nigrum,  164 

Placenta,  44  ;  formation  and  structure  of,  920 
—924 

Placental  souffle,  925 

Plants,  see  Vegetables 

Playfair,  Dr.,  his  observations  on  Milk,  855 

Plethora,  increase  of  blood-corpuscles  in, 
708  c 

Plexus  of  nerves,  use  of,  298 

Plica  Polonica,  168 

Plicae  dorsales,  937 

Pneumogastric  nerve,  see  Par  Vagum 

Poisseuille,  M.,  his  experiments  on  the  circu- 
lation, 726,  729,  730 

Polli,  Dr.,  his  observations  on  blood,  701,  702 

Polydesmus,  nervous  system  of,  326 

Polynesian  races,  103 

Polypes,  6 — 10  ;  circulation  in,  715  ;  reproduc- 
tion of  parts  in,  9,  792;  movements  of,  313 

Porrigo  favosa,  809  a 

Portal  circulation,  685,  746;  in  liver,  826, 
827  ;  in  kidneys,  839  6— 841 

Portio  dura,  406 

Posterior  roots  of  spinal  nerves,  344 

Pregnancy,  signs  of,  926  ;  see  Gestation 

Presbyopia,  538 

Prichard,  Dr.,  his  ethnographical  researches 
referred  to,  63  note,  77,  92 

Primitive  trace,  936 

Protecting  agency  of  Spinal  Cord,  394 — 396 

Proteine,  composition  and  properties  of,  116 

Proteus,  32;  blood-corpuscles  of,  146  c,  151 

Prout,  Dr.,  his  classification  of  alimentary  sub- 
stances, 640  ;  his  observations  on  secondary 
digestion,  681  ;  on  amount  of  carbonic  acid 
excreted,  767 ;  on  watery  exhalation  from 
the  lungs,  773;  on  urine,  845  rf;  on  general 
disorders  of  secretion,  883 

Puberty,  in  Male,  903;  in  Female,  908 

Pulsation  of  heart,  717 

r-  of  arteries,  729 

Pulse,  average  frequency  of,  at  different  ages, 


748 


INDEX. 


The  Numbers  refer  to  the  Paragraphs. 
727;  variations  of,  under  different  circum- 
stance^ 727  a-e ;  proportion  of  to  respira- 
tory movements,  762 

Pulse,  respiratory,  744  b 

venous,  723  c 

Pupil,  action  of,  395 

Purkinje,  optical  experiment  of,  555 

Pus,  production  of  of,  779,  800,  805,  806 

Pyramids,  anterior  and  posterior,  350 — 354 


Q- 

QUADRUMANA,  50 

Quekett,  Mr.  J.,,  his  observations  on  bone  re- 
ferred to,  194  a 

Quetelet,  M.,  his  researches  on  relative  mor- 
tality at  different  seasons,  699  c;  on  length 
and  weight  of  infants  at  birth,  948 ;  on  rela- 
(  tive  viability  of  males  and  females,  950  ;  on 
comparative  heights  of  males  and  females, 
951 . 

Quickening,  927 


R. 

RACIBORSKI,  fiis  researches  on  Conception,  909 

Radiata,  5—10;  general  structure  of,  5;  affi- 
nity with  vegetables,  6,  7 ;  symmetry  in,  8; 
reproduction  of  parts  in,  9;  nutritive  organs 
in,  10  ;  nervous  system  in,  311- — 314 

Rainey,  Mr.,  his  researches  on  structure  of 
lungs,  757 

Recti  muscles  of  orbit,  450 

Red  Corpuscles  of  Blood,  see  Corpuscles,  Red 

Reeds,  vibrating,  laws  of,  606  c 

Rees,  Dr.  G.  O.,  his  observations  on  blood-cor- 
puscles referred  to,  143,  144,  148;  on  com- 
position of  Chyle  and  Lymph,  691 ;  on  Saline 
matter  of  Blood,  697  d 

Reflex  action,  313,  363  ;  in  Mollusca,  316,  317, 
322,;  in  Articulata,  327—329,335;  in  Ver- 
tebrata,  337,  364—373 

— — ,  cases  of  in  Man,  without  sensa- 
tion, 365—370 

Regeneration  of  parts,  in  lower  Animals,  9, 
792;  of  bone,  204—207,  792;  of  nervous 
substance,  253 

Reid,  Dr.  J.,  his  researches  on  respiratory 
movements,  374,  375;  on  movements  of 
deglutition,  384—386 ;  on  movements  of  sto- 
mach, 387;  onglosso-pharyngeal  nerve,  407; 
on  pneumogastric,  408 — 416  ;  on  laryngeal 
nerves,  378,  379  ;  on  spinal  accessory,  417; 
on  muscular  contractility,  589;  on  irritabi- 
lity of  heart,  717 ;  on  Asphyxia,  723  c, 
780;  on  capillary  circulation,  740;  on  mu- 
cous membrane  of  uterus,  919  ;  on  structure 
of  placenta,  922 
Reid,  Dr.  D.  B.,  his  researches  on  respiration, 

765 

Reinforcement,  fibres  of,  326 
Reparative  processes,  792 — 801  ;  Dr.  Macart- 
ney's views  of,  793 — 801  ;  union  by  first  in- 
tention, 794 ;  process  of  organization  of 
liquor  sanguinis,  119,  795;  organization  of 
blood,  700,  796;  modelling  process,  797; 


causes  favourable  to,  798;  granulation,  799 

• — 801 


Repetition  of  parts  in  Radiata,  6 — 9 ;  in  Ar- 
ticulata, 324,  330 

REPRODUCTION,  - 

General  account  of,  281,  282,898  ;  in  Plants, 

109,  898,  899  ;  in  Animals,  900 
History  of,  in  Malej  901 — 904;  spermatic 
fluid,  867,  901  ;  evolution  of  spermatozoa, 
902  ;  power  of,  903  ;  coitus,  904 
History  of,  in  Female,  905 — 933;  general 
account  of  ovum,  905;  first  development 
of,  906,  907;  menstruation,  908,  909; 
aptitude  for  conception,  909,  910  ;  coitus, 
911;  escape  of  ovum,  912;  corpus  luteum, 
913,  914;  first  changes  in  ovum,  915 — 
917;  addition  of  chorion,  918;  formation 
of  decidua,  919  ;  formation  and  structure 
of  placenta,  920—924 ;  sound  of,  925 ;  in- 
crease of  tissue  of  uterus,  926;  quicken- 
ing, 927  ;  parturition,  928,  929;  ordinary 
duration  of  gestation,  930;  protracted  ges- 
-  tation,  931  ;  shortest  term  of  gestation, 

932 ;  superfcetation,  933 
Development  of  embryo,  see  Embryo 
Reproduction  of  lost' parts,  9,  792 

Reptiles,  28 — 32;  respiration  and  circulation 
in,  28,  756;  different  orders  of,  29,  30 ; 
connected  with  Fishes  by  Batrachia,  31, 
32;  brain  of,  360;  blood-corpuscles  of, 
145,  146  c;  lungs  of,  756 

Resistance,  sense  of,  514 

RESPIRATION, 

General  purposes  of,  749 — 754;  necessity 
for,  749 ;  in  Plants,  750 ;  in  Animals, 
generally>  751  ;  in  warm-blooded  Verte- 
brata,  752 ;  variation  in  degree  of,  753, 
754 

Structure  and  action  of  Respiratory  organs, 
in  Invertebrata,  755  ;  in  lower  Vertebrata, 
756  ;  structure  and  development  of  lungs 
in  Man,  757  ;  arrangement  of  their  blood- 
vessels, 758;  contractility  of  bronchial 
tubes,  758  ;  movements  concerned  in  ex- 
change of  air,  760,  761 ;  number  and  ex- 
tent of,  762,  763 ;  capacity  of  lungs,  764 
Chemical  phenomena,  765 — 768;  carbonic 
a,cid  exhaled,  765  ;  proportional  amount 
of  oxygen  absorbed,  766;  absolute  quan- 
tity of  carbon  set  free,  767;  variations  in, 
767  a-i ;  azote  absorbed  and  exhaled, 
766;  cutaneous  respiration,  768 
Effects  on  the  blood,  769 — 772;  carbonic 
acid  in  venous  blood,  769,  770;  exhala- 
tion of,  in  hydrogen  and  azote,  769  ;  com- 
parative analysis  of  free  gases  in  arterial 
and  venous  blood,  770;  causes  of  change 
of  colour,  771,  772 

To  be  regarded  as  an  Excretion,  275,  749  ; 
consequences  of  retention  of  carbonic 
acid,  778 — 780  ;  phenomena  of  Asphyxia, 
779  ;  its  immediate  causes,  780 
Movements  of,  760 — 763 ;  dependent  on 
Nervous  agency,  374,  375 ;  centre  of,  in 
Medulla  oblongata,  376;  nerves  concerned 
in,  374—376  ;  independent  of  will  and  of 
consciousness,  377  ;  guard  to  entrances  of 
lungs,  378,  379;  modifications  of,  379 — 
381 ;  influence  of  pain  on,  431,  763  ;  num- 


INDEX. 


749 


The  Numbers  refer  to  the  Paragraphs. 


ber  of,  762,  76.3;  share  of  lungs  and  air- 
passages  in,  759,  760;  various  influences 
affecting,  763 

Respiratory  Circulation,  710  ;  peculiarity ^>f, 
746 

Respiratory  pulse,  744  6 

Restiform  bodies,  350 — 354 

Rete  mucosum,  161 

Retina,  structure  of,  539 ;  the  recipient  of 
visual  impressions,  536 ;  inversion  of  pic- 
tures upon,  543;  persistence  of  impressions 
on,  551,  552  ;  vanishing  of  images  on,  554  ; 
visual  representation  of,  555 

Retinacula,  906,  912 

Rigor  Mortis,  232,  595— 697 

Ritchie,  Dr.,  his  researches  on  development 
of  ova,  907  ;  on  Menstruation,  909  ;  on  the 
Corpus  luteum,  914 

Robinson,  Mr.,  on  effusion  of  fibrine,  803 


8< 


SACCHARINE  principles  of  food,  640  ;  destina- 
tion of,  641,  643,  645,  670 

Saliva,  properties  of,  656,  668,  863  ;  incorpo- 
ration of  with  food,  656 

Salivary  glands,  structure  of,  862  ;  secretion 
of,  863  ;  influence  of  nervous  system  on, 
625,  626 

Saunders,  Mr.  .E.,  his  researches  upon  the 
teeth,  217  k-m 

Savart,  M.,  his  researches  upon  sound,  469  a 

Scharling,  Prof.,  his  researches  on  respiration, 
767 

Schleiden,  his  researches  on  the  development 
of  cells  in  Plants,  124 

Schwann,  his  experiments  on  muscular  con- 
traction, 592 ;  his  observations  on  cellular 
origin  of  Animal  structures,  135 

Seasons,  influence  of  on  Calorification,  894 

Sebaceous  glands,  872 

SECRETION,  general  nature  of,  275 — 278,  817  ; 
structures  adapted  for,  821—823;  essen- 
tially composed  of  cells,  821 — 823  ;  disor- 
ders of,  connected  with  nutritive  processes, 
882  ;  not  dependent  on  nervous  agency,  620, 
624  ;  influence  of  nervous  system  on,  625 — 
628 

Secretions,  amount  of,  818;  sources  of,  819  ; 
elements  of,  pre-existing  in  the  blood,  820  ; 
some  of  them  used  in  the  system,  820 ;  see 
Bile,  Urine,  Milk,  &c. 

Seguin,  on  cutaneous  exhalation,  870 

Selecting  power,  of  individual  parts,  782 — 785 

Semicircular  canals,  366 

Seminal  secretion,  867,  901,  904;  influenced 
by  state  of  feeling,  626  note 

SENSATION,  307,  308 ;  characteristic  of  Ani- 
mals, 283,  284;  why  associated  with  reflex 
actions,  371,  372;  dependent  on  Capillary 
Circulation,  290,  507,  508  ;  the  originator  o 
consensual  movements,  430— 432 ;  the.  guide 
of  voluntary  movements,  433 
Sensations,  nature  of,  506 ;  different  kinds  of 

507  ;   dependence  of  on  supply   df  blood 

508  ;  pain  or  pleasure  connected  with,  509 
influence  of  habit  on,  510 — 513  ;   special 


514,  518 ;  common,  514,  515 ;  subjective 
and  objective,  516,  518,  521  ;  transference 
of,  517  ^  influence  ofattention  on,  519 — 521 ; 
knowledge  gained  from,  487 — 490 

Sense,  Muscular,  433,  434 

Sensibility  in  different  parts,  507,  508 

Sensitive  Plant,  movements  of,  1 

Sensorium,  435 

Sensory  ganglia,  422—427  ;  functions  of,  428 
—440 

nerves,  441 — 449 ;  terminations  of,  248 

tract  of  Sir  C.  Bell,  351 

Serous  membranes,  175 

Serpents,  29 

Serres,  his  measurements  of  Cerebellum,  457  ; 
of  Cerebrum,  481 

Serum  of  blood,  696  ;  composition  of,  697 ; 
proportion  of,  to  clot,  703;  milky,  697  e 

Seventh  pair,  portio  mollis  of^  446  ;  portio 
dura  of,  406 

Sexual  instinct,  903,  909  ;  its  supposed  loca- 
tion in  the  Cerebellum,  466—470 

Sharpey,  Dr.,  his  observations  on  development 
of  bone,  197 — 201  ;  on  muscular  fibrillae, 
230,  note;  on  nerves  of  Cuttlefish,  322 ;  on 
decidua,  919 

Shell,  structure  of,  in  Echinodennata,  192  ;  in 
Mollusca,  192 

Siege  of  Landau,  946 

Sighing,  act  of,  380 

Sight,  sense  of,  see  Vision 

Simon,  Mr.,  on  Thymus  and  Thyroid  Glands, 
687,  688 

Single  vision  with  two  eyes,  545 — 547 

Siren,  32  ;  blood-corpuscles  of,  145  note 

Sixth  pair  of  nerves,  405 

Size,  mode  of  estimating  by  vision,  549 

Skin,  structure  of,  176,  177  ;  contractility  of, 
234  ;  absorbing  power  of,  676 — 679  ;  respi- 
ratory power,  of,  768  ;  exhaling  apparatus 
in,  868  ;  transpiration  from,  869—871 ;  seba- 
ceous and  ceruminous  glands  in,  872 ;  exu- 
dation from,  increased  by  heat,  897 

Skull,  forms  of,  in  different  races  of  Men,  83 
—87 

Sleep,  499 

Smell,  sense  of,  531,  532  ;  seat  of,  531  ;  con- 
ditions of,  531;  acuteness  of,  in  some  Ani- 
mals and  Men,  532 

Sneezing,  act  of,  381,  531 

Sobbing,  act  of,  380 

Solen,  nervous  system  of,  317,  318 

Somatic  death,  813,  814 

Somnambulism,  500,  Appendix  11. 

Sound,  laws  of  propagation  of,  560 — 562;  suc- 
cessive pulses  of,  569  ;  mode  of  estimating 
direction,  distance,  and  intensity  of,  570  ; 
rapidity  of  perception  of,  compared  with 
that  of  light,  571  ;  use  of  in  regulating  voice, 
572,  611 

Sounds,  articulate,  612 — 619 

,  of  heart,  720,  721 ;  of  placenta,  925 

Spasmodic  diseases,  501 — 504 

Species,  discrimination  of,  64 — 67;  variation 
within  limits  of,  68— 73 ;  distinguished  by 
physiological  and  psychological  characters, 
74—77 

Spencer,  Earl,  on  the  duration  of  gestation  in 
Cattle,  931 


750 


INDEX. 


Spermatic  fluid,  867 

Spermatozoa,  900,  901 ;  function  o'f,  900,  911, 
917;  development  of,  902 

Sphincters,  action  of,  391,  392 

Sphinx  ligustri,  Nervous  system  of,  325 

Spinal  accessory  nerve,  4i7 

Spinal  Cord  of  Vertebrata,  346—350  ;  its  com- 
parative anatomy,  346;  its  divisions,  346, 
347 ;  its  connections  with  the  nerves,  347, 
348  ;  functions  of  several  parts,  of,  349,  350; 
general  functions  of,  363 — 373  ;  absence  of 
proper  sensibility  in,  365;  protecting  agency 
of,  394 — 396;  maintenance  of  muscular  ten- 
sion through,  398,  399 ;  influence  of,  on 
heart,  717  a ;  power  of  sustaining  locomo- 
tive actions,  397  ;  pathological  conditions  of, 
400,401,501—504 

Spinal  nerves,  double  roots  of,  344 

Spinal  system,  nerves  of,  402—421 

Spleen,  structure  of,  683  ;  functions  of,  684, 
685 

Sponges,  1,  7 

Spongioles  of  Plants,  107 

Stammering,  causes  of,  617,  618 ;  treatment 
of,  619 

Star-fish,  structure  of,  8 — 10  ;  nervous  system 
of,  312,  314 

Stark,  Dr.,  his  analysis  of  Bone,  196  & 

Stearlne,  composition  and  properties  of,  185  a 

Stereoscope,  546, 547 

Stilling,  Dr.,  his  researches  on  the  Spinal 
Cord,  347 

Stomach,  presence  of,  characteristic  of  Ani- 
mals, 2;  general  characters  of,  655;  state 
of,  in  health,  657;  in  disease,  758  ;  sense  of 
hunger  referred  to,  637  ;  movements  of,  387, 
413,  659;  influenced  by  nerves,  387,  413  ; 
secretions  of,  665,  873  ;  influence  of  nerves 
on,  414,  415  ;  effects  of  blows  or*,  580,  625 

Stomato-gastric  system,  ofMollusca,  319,  ^20; 
of  Articulata,  332—334 

Strabismus,  454  a-d 

Strangury,  504 

Strings,  vibrating,  laws  of,  606  a 

Strumous  diathesis,  878  (see  Tubercle) 

Subjective  sensations,  516,  518,  521 

Suction,  act  of,  386  c 

Sudoriferous  glandulse,  868  ;  their  secretion, 
869,  870 

Sulphur,  contained  in  food,  648 ;  in  proteine- 
compounds,  113,  114;  oxidation  of,  in  sys- 
tem, 847  ... 

Superfo3tation,  933 

Suppuration,  799—801 

Supra-renal  capsules,  686 

Swimming-bladder,  27 

Symmetrical  diseases,  784,  785 

Symmetry,  radiate,  8  ;  bilateral,  of  Articulata, 
18 ;  of  Vertebrata,  25 ;  deficiency  of,  in 
Mollusca,  12 

Sympathetic  System,  peculiar  fibres  of,  244  ; 
general  structure  of,  338,  341,  342;  influ- 
ence of,  on  movements  of  intestinal  canal, 
388,  389 ;  on  ureter  and  muscular  coat  of 
bladder,  390  ;  oh  uterus  and  fallopian  tubes 
393;  on  heart  and  vessels,  416,  623,  717  6, 
730,  732;  on  duetus  choledochus,  825 /; 
on  processes  of  organic  life,  620 — 628 

Sympathies,  motor,  620—623  ;  organic,  625— 
628 


The  Numbers  refer  to  the  Paragraphs. 

Syncope,  580,  814 
Synovial  Membranes,  175 
Syro-Arabian  nations,  94 


T. 


TALIACOTIAN  operation,  253 

Taste,  nerves  of,  407,  447 

Taste,  sense  of,  527 — 530;  nerves  concerned 
in,  407,  447;  conditions  of,  528  :  partly  de- 
pendent on  smell,  529 ;  educability  of,  530  ; 
purposes  of,  529 

Teeth,  208—217;  component  tissues  of,  208 
— 216;  development  of,  in  Human  infant, 
217,  a-i  ;  a  test  of  age,  2"l7  k,  I,  m 

Temperature,  sense  of,  514,  524  ;  ordinary,  of 
the  human  body,  886  ;  extremes  of  sustain- 
able by  Man,  887,  888  ;  (see  Heat) 

Tendons,  structure  of,  140  ;  attachment  of  to 
muscle,  233 

Tenesmus,  504 

Tension  of  Muscles,  398,  399 

Tetanus,  401,  502 

Testis,  structure  of,  866  ;  development  of,  866 
6  ;  secretion  of,  867 

Tessier's  experiments  on  duration  of  gestation, 
931 

Thackrah,  Mr.,  his  observations  on  coagula- 
tion of  blood,  703 

Thalami  Optici,  423,  424 

Thaumalrope,  551 

Third  pair  of  Cranial  Nerves^Oo 

ventricle  of  Brain,  358,  359 

Thirst,  sense  of,  639 

Thorax,  movements  of,  in  respiration,  760, 
761 

Thymus  gland,  687,  688 

Thyroid  gland,  689 

Tiedemann,  his  researches  on  absorption,  675 

Tissues,  elementary,  classification  of,  187 

Todd,  Dr.,  on  mucous  membrane,  873 

Tomes,  Mr.,  his  observations  on  bone  referred 
to,  196,  203,  207 

Tongue,  papilla  of;  527;  movements  of,  418, 
419 

Tonicity  of  muscles,  593 — 597 ;  of  arteries, 
731  ;  effects  of  deficiency  of,  745 

Tortoises,  29 

Touch,  nerves  of,  448 

Touch,  sense  of,  522—826  ;  varying  acuteness 
of,  in  different  parts,  522 ;  ideas  derived  from, 
514,  523;  peculiarities  of,  524  ;  improvability 
of,  525;  modifications  of,  in  different  ani- 
mals, 526  ;  connection  of,  with  vision,  541, 
542 

Toynbee,  Mr.,  his  researches  on  non-vascular 
tissues,  187—190 

Trainers'  diet,  654 

Transudation,  824 

Travers,  Mr.,  his  observations  on  formation  of 
new  vessels,  222  ;  on  production  of  new  tis- 
sue, 795 

Trifacial  nerve,  403,  404 

Tubercula  Quadrigemina,  422,  436 


Tubercular  matter,  807, 
system  to  deposit,  878 


tendency  in  the 


Tubular  tissues,  simple,  218—222;  compound, 
223—253 


INDEX. 

The  Numbers  refer  to  the  Paragraphs. 


751 


Tunica  granulosa,  906,  912 

Turkish  race,  96 

Tunicata,  nervous  system  and  actions  of,  316 

Tympanum,  membrane  of,  563  ;  cavity  of,  564 


U. 

UMBILICAL  cord,  941,  942 

—  vesicle,  939,  941 

Unguiculated  Mammalia,  48,  49 

Ungulated  Mammalia,  48,  49 

Unity,  specific,  of  human  races,  91 

Urea,  composition  of,  844 ;  increase  of  by  ex- 
ercise, 844 

Uric  acid,  composition  of,  845 ;  pathological 
changes  in,  845  a-d 

Urine,  nature  and  purposes  of  its  secretion,  842 
— 852;  effects  of  its  retention,  8,42;  com- 
position of,  in  health,  843;  amount  of  area 
contained  in,  844;  uric  acid  in,  845;  hippu- 
ric  acid  in,  845 a;  no  lactic  acid  in,  846; 

»  saline  compounds  in,  847  ;  alkaline' or  acid 
reaction  of,  848  ;  amount  of  azotized  matter 
in,  849  ;  influence  of  diet  on,  849,  850  ;  trans- 
ference of  secretion,  851 ;  excretion  of  saline 
matter  with,  852 

Uterus,  changes  of,  preparatory  to  gestation, 
919;  increase  in  substance  during  gestation, 
926  ;  contractions  of,  how  far  dependent  on 
nervous  agency,  393,  928 


V. 

VAGUS  nerve,  see  Par  Vagum 

Valentin,  his  researches  on  Spinal  Cord,  349  ; 
on  movements  of  Stomach,  387  ;  on  the  Sym- 
pathetic, 388,  390,  393,  730 ;  on  Olfactory 
nerve,  441 ;  on  Optic  nerve,  442  ;  on  Portio 
Dura,  406  ;  ,on  Par  Vagum,  408,  416 ;  on  Spi- 
nal Accessory,  417 ;  on  Hypoglossal,  418 ; 
on  quantity  of  blood  in  system,  724 

Valves  of  heart,  actions  of,  722,  723  c ;  sounds 
produced  by,  720,  721 

Vapour,  exhalation  of,  from  lungs,  773,  774 

Variation,  extremes  of  in  species,  68—71 ;  in 
Man,  72,  73 

Varicose  nerve-tubes,  243 

Vasa  lutea,  939 

Vascular  area,  938 

— -  lamina  of  Germinal  Membrane,  936, 

938,940 

Vegetable  proximate  principles,  111 

Vegetables,  distinguished  from  Animals,  1—4; 
food  of,  2  ;  movements  of,  1,  283  ;  early  de- 
velopment of,  3;  formation  of  cells  in,  106— 
109,  120—125;  general  functions  of,  107, 
261;  circulation  in,  712 — 714;  respiration 
in,  750  ;  reproduction  in,  899 

Veins,  distribution  of,  710;  structure  of,  743; 
movement  of  blood  in,  744;  causes  of  con- 
gestion in,  745;  pulsation  in,  723  c 

Ventricles  of  heart,  contraction  of,  718—721 ; 
force  of,  726 ;  thickness  of,  723 ;  capacity  of, 
724 

Ventricles  of  brain,  third,  358:  fourth.  346, 
358 

Vertebrae,  21 ;  origin  of,  937 


Vertebral  column  in  Fishes,  26 

Vertebrata,  5,  20—25  ;  skeleton  of,  21,  22;  ex- 
tremities of,  22;  predominance  of  nervous 
system  in,  20,  23  ;  organs  of  animal  and  vege- 
tative life  in,  25;  symmetry  in,  25;  intelli- 
gence of,  23  ;  nervous  system  of,  339 — 362 

Vesicles  of  Brain  in  Embryo,  358 

Vessels,  formation  of,  in  Plants,  218;  in  Ani- 
mals, 221,  222 

Viability  of  Infant,  earliest  period  of,  932 

Vierordt,  his  researches  on  respiration,  765, 
767 

Villi  of  Mucous  Membrane,  178,  472,  473 

Visceral  system  of  nerves,  see  Sympathetic  '• 

Visible  direction,  law  of,  543 

Vision,  sense  of,  533 — 555;  optical  conditions 
of,  534—537  ;  defective,  538 ;  limits  of,  540; 
mental  conditions  of,  541 ;  connection  of, 
with  touch,  541, 542;  erect,  543;  single,  544, 
545 ;  appreciation  of  form  by,  546,  547 ;  of 
distance,  548  ;  of  size,  549;  persistence  of 
impressions,  551 ;  complementary  colours, 
552;  want  of  power  to  distinguish  colours, 
553;  vanishing  of  images,  554;  visual  per- 
ception of  retina,  555 

Vital  Action  involves  change,  254          " 

dependence  of,  on  external  stimuli, 


255,  258 

Vital  Actions,  classifications  of,  into  Functions, 
260  .  , 

Vital  forces,  256 

Vitality,  duration  of  in  individual  parts,  810 — 
812;  dormant,  255 

.of  general  system,  destroyed  by  sudden 

shock,  580,  735,  742 

Vital  properties,  256,  258  ;  retention  of,  259 

Vitelline  vessels,  939 

Vitreous  humour,  190 

Voice,  602—619  ;  conformation  of  larynx,  603 
— 605.;  sounds  resembling  produced  by 
strings,  606  a ;  by  flute-pipes,  606  b ;  by  reeds, 
606  c;  action  tof  chordae  vocales,  607;  arti- 
ficial larynx,  607 ;  pitch,  how  regulated,  608  ; 
falsetto  notes,  how,  produced,  609  ;  influence 
of  air-passages  on,  610 ;  movements  concern- 
ed in,  how  directed,  611 

Volkmann,  his  experiments  on  Muscular  con- 
traction, 576 

Voluntary  actions,  distinguished  from  automa- 
tic, 483  ;  originate  in  Cerebrum,  483,  495 

Vomiting,  505 

Vowel  sounds,  614,  615 


W. 

WAGNER, his  observations  on  blood-corpuscles, 
148, 155,  157, 159  a ;  his  account  of  develop- 
ment of  Spermatozoa,  902 
Wasmann,  his  researches  on  pepsin  668 
Waste  of  Animal  tissues,  see  Decay,  and  Dis- 
integration 

Weber,  Prof.,  his  researches  on  sensation,  522 ; 
on  absorption,  672;  on  movements  of  heart, 
717  a 

Whale,  Spermaceti,  peculiar  sensibility  of,  526 
Wheatstone,  Prof.,  his  Stereoscope,  546,  547 
White  corpuscles  of  blood,  151—159 
White  fibrous  tissue,  138—141 


752 


INDEX. 


The  ^Numbers  refer  to  the  Paragraphs.  (      ' .  , 


White  matter  of  nervous  system,  242,  243 
WiJliams,  Dr.,  on  contractility  of  bronchi,  759; 
on  Necrsemia,  708 ;  on  Inflammation,  158 ; 
on  causes  of  Venous  Congestion,  745 
Willis,  Mr.,  his  researches  on  the  Voice,  604 — 

608 
Wilson.  Mr.  Erasmus,  on  cutaneous  follicles, 

•868 

Wings  of  Insects,  interlacement  of  nerves  sup- 
of, 600 
upon  sound, 


plying,  298;  rapidity  of  motion  of,  600 
Wollaston,  Dr.,  his  observations  upon 
569  a ;  upon  hemiopia,  545  note 


YAWNING,  act  of,  390 
Yellow  fibrous  tissue,  138— 142 
Yolk,  905,  935,  939  , 
Yolk-bag,  905,  935,  939 

Young  animals,  low  calorifyirig  power  of,  893, 
932  a;  influence  of  cold  upon,  893  c 

Z. 

ZONA  pellucida,  905,  917 

Zwicky,  Dr.,  on  organization  of  thrombus,  700 


v-.     -'• 


-X-  •  '  '        • 

THE  END: V : 


•rv 


A3.I 


CATALOGUE 

OF 

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AND 

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1847. 


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Roget's  Outlines  of  Physiology,  8vo.,  516  pages. 

Todd  and  Bowman's  Physiological  Anatomy  and 
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Abercrombie  on  the  Stomach*  new  edition,  1  vol. 

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Alison's  Outlines  of  Pathology,  &c.,  1  vol.  8vo., 

420  pages. 

Berzelius  on  the  Kidneys  and  Urine,  8vo.,  180  pp. 
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Billing's  Principles,  1  vol.  Svo.,  304  pages. 
l>ird  on  Urinary  Deposits,  Svo.,  228  pages,  cuts. 
Masse's  Pathological  Anatomy,  Svo.,  379  pages. 
Hope  on  the  Heart,  by  Pennock,  a  new  edition, 

with  plates,  1'vol.  8vo.,  572  pages. 
Hughes  on  the  Lungs  and  Heart,  1  vol.  12mo., 

270  pages,  with  a  plate. 

Philip  on  Protracted  Indigestion,  Svo.,  240  pp. 
Philips  on  Scrofula,  1  vol.  8vo.,  350  pages. 
Pi  out  on  the 'Stomach  and  Renal  Diseases,  1  vol. 

8vo.,  466  pages,  colored  plates. 
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Pathological    Anatomy    of    the   Human 
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Wilson  on  the  Skin,  1  vol.  Svo.,  new  ed.,  440  pp. 
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2d  edition,  1  vol.  Svo.    Nearly  ready. 
Williams  on  the  Respiratory  Organs,  by  Clymet 

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PRACTICE  OF  MEDICINE. 
Ashwell  on  the  Diseases  of  Females,  by  Goddard, 

1  vol.  8vo.,  520  pages. 

Bartlett  on  Fevers,  new  edition,  much  enlarged; 
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Now  ready.   550  pages. 
Benedict's  Compendium  of  Chapman's  Lectures, 

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Chapman  on  Thoracic  and  Abdominal  Viscera, 

&c.,  1  vol.  8vo.,  384  pages. 
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8vo.,  450  pages. 
Colombat  de  L'Isere  on  Females,  translated  and 

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Condie  on  the  Diseases  of  Children,  2d  edition,  1 

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Churchill  on  the  Diseases  of  Females,  by  Huston, 

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Clymer  and   others  on  Fevers,  a  complete  work 

in  1  vol.  Svo.  600  pages. 

Dewees  on  Children,  9th  ed.,  1  vol.  8vo.,  548  pp. 
Dewees  on  Females,  9th  edition,  1  vol.  Svo. ,532 

pages,  with  plates. 
Dunglison's  Practice  of  Medicine,  3d  edition,  2 

vols.  8vo.,  over  1400  pages. 
Esquirol   on   Insanity,  by  Hunt,  Svo.  496  pages. 
Thomson  on  the  Sick  Room,  &c.,   1  vol.  large 

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Brodie  on  the  Joints,  1  vol.  Svo.  216  pages. 
Brodie's  Lectures  on  Surgery,  1  vol.  8vo.,  350  pp. 
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Cooper  on  the  Anatomy  and  Diseases  ofthe  Breast, 

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Fergusson's  Practical    Surgery,    1    vol.  Svo.,  2d 

edition,  640  pages,  many  cuts. 
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Harris  on  the  Maxillary  Sinus,  8vo.,  166  pp. 
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Liston's  Lectures  on  Surgery,  by  Mutter,  1  vol. 

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NOW  COMPLETE. 

THE     GREAT     SURGICAL    LIBRARY. 

A  SYSTEM  "OF  SURGERY, 

BY    J.    M.    CHELIUS, 

Doctor  in  Medicine  and  Surgery,  Public  Professor  of  General  and  Ophthalmic  Surgery,  etc.  etc.  in  the  Uni- 
versity of  Heidelberg. 

TRANSLATED  FROM  THE  GERMAN, 

AND  ACCOMPANIED  WITH  ADDITIONAL  NOTES  AIND  OBSERVATIONS, 
BY    JOHN    F.    SOUTH, 

Surgeon  to  St.  Thomas'  Hospital. 

EDITED,  WITH  REFERENCE  TO  AMERICAN  AUTHORITIES, 
BY  GEORGE  W.  NORRIS,  M.  D. 

Now  complete  in  three  large  8vo.  volumes  of  nearly  twenty-two  hundred  pages,  or  in  17  numbers,  at  50  cents. 

This  work  has  been  delayed  beyond  the  time  originally  promised  for  its  completion,  by  the  very  extensive 
additions  of  the  translator.  In  answer  to  numerous  inquiries,  the  publishers  now  have  the  pleasure  to  pre- 
sent it  in  a  perfect  state  to  the  profession,  forming  three  unusually  large  volumes,  bound  in  the  best  manner, 
and  sold  at  a  very  low  price. 

This  excellent  work  was  originally  published  in  Germany,  under  the  unpretending  title  of  "Handbook  to 
the  Author's  Lectures."  In  passing,  however,  through  six  successive  editions,  it  has  gradually  increased 
in  extent  and  importance,  until  it  now  presents  a  complete  view  of  European  Surgery  in  general,  but  more 
especially  of  English  practice,  and  it  is  acknowledged  to  be  well  fitted  to  supply  the  admitted  want  of  a  com- 
plete and  extended  system  of  Surgery  in  all  its  branches,  comprehending  both  the  principles  and  the  prac- 
tice of  this  important  branch  of  the  healing  art.  Since  Benjamin  Bell's  great  work,  first  published  in  1783, 
and  now  almost  obsolete,  no  thorough  and  extended  work  has  appeared  in  the  English  language,  occupying 
the  ground  which  this  is  so  well  calculated  to  cover. 

The  fact  of  this  work  being  carried  to  six  editions  in  Germany,  and  translated  into  no  less  than  eight  Ian- 
guages,  is  a  sufficient  evidence  of  the  ability  with  which  the  author  has  carried  out  his  arduous  design. 

This  translation  has  been  undertaken  with  the  concurrence  and  sanction  of  Professor  Chelius.  The  trans- 
.ator,  Mr.  John  F.  South,  appears  to  have  devoted  himself  to  it  with  singular  industry  and  ardor,  and  to  have 
brought  it  up  almost  to  the  very  hour  of  publication  His  notes  and  additions  are  very  numerous,  embodying 
the  results  and  opinions  of  all  the  distinguished  surgeons  of  the  day,  Continental,  English  and  American. 
The  leading  opinions  of  John  Hunter,  on  which  Modern  English  Surgery  has  been  raised,  are  set  forth  ;  the 
results  of  the  recent  microscopical  discoveries,  especially  in  reference  to  inflammation,  will  be  found  here, 
together  with  many  other  practical  observations,  placing  the  work'on  a  level  with  the  present  state  of  Sur- 
gery, and  rendering  it  peculiarly  useful,  both  to  the  student  and  practitioner. 

The  labors  of  the  English  translator  have  been  so  numerous  and  important,  that  there  is  but  little  which 
remains  to  be  supplied  by  the  American  editor.  Dr.  G.  W.  Norris  has  consented,  however,  to  superintend 
ihe  passage  of  the  workj  through  the  press,  and  supply  whatever  may  have  been  omitted  in  relation  to  the 
Surgical  Literature  of  this  country. 

The  Medical  Press  and  profession,  both  in  England  and  in  this  country,  have  joined  in 
praise  of  this  great  work.as  being  more  complete  ihan  any  other,  and  as  affording  a  complete 
library  of  reference,  equally  suited  to  the  praciitioner  and  to  the  student. 

"  We  strongly  recommend  all  surgical  practitioners  and  students,  who  have  not  yet  looked  into  this  work, 
to  provide  themselves  with  it  without  delay,  and  study  its  pages  diligently  and  deliberately." — The  Edin- 
burgh Medical  and  Surgical  Journal. 

•'Judging  from  a  single  number  only  of  this  work,  we  have  no  hesitation  in  saying  that,  if  the  remaining 
portions  correspond  at  all  with  the  first,  it  will  be  by  far  the  most  complete  and  scientific  System  of  Surgery 
in  the  English  language.  We  have,  indeed,  seen  no  work  which  so  nearly  comes  up  to  our  idea  of  what 
such  a  production  should  be,  both  as  a  practical  guide  and  as  a  work  of  reference,  as  this  ;  and  the  fact  that 
it  has  passed  through  six  editions  in  Germany,  and  been  translated  into  seven  languages,  is  sufficiently.con- 
vincing  proof  of  its  value.  It  is  methodical  and  concise,  clear  and  accurate,  omitting  all  minor  details  and 
fruitless  speculations,  it  gives  us  all  the  information  we  want  in  the  shortest  and  simplest  form." — The  New 
York  Journal  of  Medicine. 

'•  Nor  do  these  parts,  in  any  degree,  fall  short  of  their  predecessors,  in  the  copiousness  and  value  of  their 
details.  The  work  certainly  fprms  an  almost  unique  curiosity  in  medical  literature,  in  the  fact  that  the 
notes  occupy  a  larger  portion  of  the  volume  than  the  original  matter,  an  arrangement  which  is  constantly 
appearing  to  render  the  text  subsidiary  to  its  illustrations.  Still  this  singularity  of  manner  does  not  at  all 
detract  from  the  value  of  the  matter  thus  disposed." — The  London  Medical  Gazette. 

'•This  work  has  long  been  the  chief  text-book  on  Surgery  in  the  principal  schools  of  Germany,  and  the 
publication  of  five  editions  of  it  in  the  original  and  of  translations  into  no  less  than  eight  foreign  languages, 
shows  the  high  estimation  in  which  it  is  held.  As  a  systematic  work  on  Surgery  it  has  merits  of  a  high  order. 
It  is  methodical  and  concise — and  on  the  whole  clear  and  accurate.  The  most  necessary  information  is 
conveyed  in  the  shortest  and  simplest  form.  Minor  details  and  fruitless  speculations  are  avoided.  It  is  in 
fact,  essentially  a  practical  book.  This  work  was  first  published  nearly  twenty  years  ago,  and  its  solid  and 
permanent  reputation  has  no  doubt  led  Mr.  South  to  undertake  the  present  translation  of  the  latest  edition 
of  it,  which,  we  are  informed,  is  still  passing  through  the  press  in  Germany.  We  should  have  felt  at  a  loss 
to  select  any  one  better  qualified  for  the  task  than  the  translator  of  Otto's  Compendium  of  Human  and  Com- 
parative Pathological  Anatomy— a  surgeon  to  a  large  hospital  whose  industry  and  opportunities  have 
enabled  him  to  keep  pace  wjih  the  improvements  of  his  time."— The  Medico- Chirurgical  Review. 

'•  Although  Great  Britain  can  boast  of  some  of  the  most  skillful  surgeons,  both  among.her  past  and  her  present 
professors  of  that  branch  of  medical  gcience.no  work  professing  to  be  a  complete  system  of  Surgery  has  been 
published  in  the  British  dominions  since  that  of  Benjamin  Bell,  now  more  than  half  a  century  old. 

"This  omission  in  English  medical  literature  is  fully  and  satisfactorily  supplied  by  the  translation  of  Profes- 
sor Chelius's  System  of  Surgery  by  agentleman  excellently  fitted  for  the  task,  both  by  his  extensive  reading, 
and  the  opportunities  of  practical  experience  which  he  has  enjoyed  for  years  as  surgeon  to  one  of  our  largest 
metropolitan  hospitals.  The  fact  of  Professor  Chelius's  work  having  been  translated  into  seven  languages  is 
sufficient  proof  of  the  estimation  in  which  it  is  held  by  our  continental  brethren,  and  the  English  Edition, 
now  in  course  of  publication,  loses  none  of  the  value  of  the  original  from  the  treatment  received  at  the  hands 
of  its  translator.  The  notes  and  additions  of  Professor  South  are  numerous,  and  contain  the  opinions  result- 
ing from  his  vast  experience,  and  from  that  of  his  colleague." — The  Medical  Times. 

•llt  ably  maintains  the  character  formerly  given,  of  being  the 'most  learned  and  complete  systematic 
treatise  now  extant  The  descriptions  of  surgical  diseases,  and  indeed  the  whole  of  the  pathological  depart- 
ment, are  most  valuable." — The  Edinburgh  Medical  and  Surgical  Journal. 

Op*  Persons  wishing  this  work  sent  to  them  by  mail,  in  parts,  can  remit  Ten  Dollars,  for 
which  a  set  will  be  sent  by  the  publishers,  free  of  postage,  together  with  a  copy  of  "The 

Medical  News  and  Library"  for  one  year. 

j 


LEA  &  BLANCHARD'S  PUBLICATIONS. 


GHELIUS'S  SURGERY,  CONTINUED. 

The  publishers  annex  a  very  condensed  summary  of  the  contents  of  Chelius's  Surgery,  showing 
the  complete  and  systematic  manner  in  which  the  whole  subject  is  divided  and  treated. 
I.  DIVISION. — Qf  Inflammation. 

1.  Of  inflammation  in  general. 

2.  Qf  some  peculiar  kinds  of  inflammation. 

a.  Of  erysipelas  ;  6.  Of  burns  ;  c.  Of  frost- 
bite ;  d.  Of  boils  ;  e.  Of  carbuncle. 

3.  Qf  inflammation  in  some  special  organs. 

a.  Of  inflammation  of  the  tonsils  ;  b.  Of  the 

parotid  gland  ;  c.  Of  the  breasts  ;  d.  Of 

the  urethra  ;  e.  Of  the  testicle  ;  /.  Of  the 

muscles   of  the   loins;  g.  Of  the   nail 

joints  ;  h.  Of  the  joints,  viz. 
a.  Of  the  synovial  membrane  ;  b.  Of  the  car- 
tilages ;  c.  Of  the  joint-ends  of  the  bones, 

viz.,   aa.  in  the   hip-joint;   66.  in   the 

shoulder-joint ;   cc.  in   the   knee-joint ; 

and  so  on. 

II.  DIVISION. — Diseases  which  consist  in  a  dis- 

turbance of  physical  connexion. 
1.  Fresh  solutions  of  continuity. 
A.  Wounds  ;  B.  Fractures. 
n.  Old  solutions, 

A.  Which  do  not  suppurate,  viz. 

a.  False  joints  ;  6.  Hare-lip  ;  c.  Cleft  in 
the  soft  palate  ;  d.  Old  rupture  of 
the  female  perineum. 

B.  Which  do  suppurate,  viz. 
i.  Ulcers. 

1.  In  general. 

2.  In  particular. 

a.  Atonic ;  6.  Scorbutic ;  c.  Scrofulous  ; 
d.  Gouty  ;  e.  Impetiginous ;/.  Vene- 
real ;  g.  Bony  ulcers  or  caries. 
ii.  Fistulas. 

a.  Salivary  fistula  ;  6.  Biliary  fistula ;  c.  Faecal 
fistula  and  artificial  anus ;  d.  Anal  fistula ; 
e.  Urinary  fistula. 
m.  Solutions  of  continuity  by  changed  position  of 

parts. 
1.  Dislocations;  2.  Ruptures;  3.  Prolapses; 

4.  Distortions. 

IV.  Solutions  of  continuity  by  unnatural  distention. 
1.  In  the  arteries,  aneurisms ;  2.  In  the  veins, 
varices ;  3.  In  the  capillary-vascular  sys- 
tem, teleangiectasis. 

III.  DIVISION. — Diseases  dependent  on  the  unna- 

tural adhesion  of  parts. 

1.  Anchylosis  ofthe  joint-ends  of  bones  ;  2.  Grow- 
ing together  and  narrowing  of  the  aperture 
ofthe  nostrils;  3.  Unnatural  adhesion  of  the 
tongue ;  4.  Adhesion  of  the  gums  to  the 
cheeks;  5.  Narrowing  ofthe  oasophagus  ;  6. 
Closing  and  narrowing  of  the  rectum ;  7. 
Growing  together  and  narrowing  of  the  pre- 
puce ;  8.  Narrowing  and  closing  of  the  ure- 
thra; 9.  Closing  and  narrowing  of  the  vagina 
and  ofthe  mouth  ofthe  womb. 


IV.  DIVISION. — Foreign  bodies. 

1.  Foreign  bodies  introduced  externally  into  our 

organism. 

a.  Into  the  nose  ;  6.  Into  the  mouth  ;  c.  Into 
the  gullet  and  intestinal  canal ;  d.  Into 
the  wind-pipe. 

2.  Foreign  bodies  formed  in  our  organism  by  the 

retention  of  natural  products. 

A.  Retentions  in  their  proper  cavities  and 

receptacles. 

a.  Ranula ;  6.  Retention  of  urine  ;  c. 
Retention  ofthe  fetus  in  the  womb 
or  in  the  cavity  ofthe  belly,  (Caesa- 
rean  operation,  section  ofthe  pubic 
symphysis,  section  ofthe  belly.) 

B.  Extravasation  external  to  the  proper  cavi- 

ties or  receptacles. 

a.  Blood  swellings  on  the  heads  of  new- 
born children  ;  6.  HaematoceJe  ;  c. 
Collections  of  blood  in  joints. 

3.  Foreign  bodies  resulting  from  the  accumulation 

of  unnatural  secreted  fluids. 
a.  Lymphatic  swellings  ;  6.  Dropsy  of  joints  ; 
c.  Dropsy  ofthe  bursae  mucosse  ;  d.  Wa- 
ter in  the  head,  spina  bifida ;  e.  Water 
in  the  chest  and  empyema;  /.  Dropsy 
of  the  pericardium  ;  g.  Dropsy  of  the 
belly ;  h.  Dropsy  of  the  ovary ;  i.  Hy- 
drocele. 

4.  Foreign  bodies  produced  from  the  concretion  of 

secreted  fluids. 

V.  DIVISION. — Diseases  which  consist  in  the  de- 
generation of  organic  parts,  or  in  the  produc- 
tion of  new  structures. 

1.  Enlargement  ofthe  tongue;  2.  Bronchocele  ; 
3.  Enlarged  clitoris;  4.  Warts;  5.  Bunions; 
6.  Horny  growths ;  7.  Bony  growths  ;  8.  Fun- 
gus of  the  dura  mater;  9.  Fatty  swellings; 
10.  Encysted  swellings;  11.  Cartilaginous 
bodies  in  joints ;  12.  Sarcoma;  13.  Medul- 
lary fungus  ;  14.  Polypus ;  15.  Cancer. 

VI.  DIVISION. — Loss  of  organic  parts. 

1.  Organic  replacement  of  already  lost  parts,  es- 

pecially ofthe  face,  according  to  the  Taglia- 
cotian  and  Indian  methods. 

2.  Mechanical  replacement:  Application  of  arti- 

ficial limbs,  and  so  on. 

VII.  DIVISION. — Superfluity  of  organic  parts. 
VIII.  DIVISION. — Display  of  the  elementary  ma- 
nagement, of  surgical  operations. 
General  surgical  operations  :  Bleeding,  cupping, 
application  of  issues,  introduction  ofsetons, 
amputations,  resections,  and  so  on. 
.Jnd  One  Hundred  and  Seventy-five  Pages 
of  Index. 


DRUITT'S  SURGERY,    New  Edition— Now  Ready,  1847, 

THE  PRINCIPLES  AND  PRACTICE  OF  MODERN  SURGERY, 

BY    ROBERT    DRUITT,    SURGEON. 

THIRD  AMERICAN  PROM  THE  THIRD  LONDON  EDITION 
Illustrated  with  one  hundred  and  fifty-  three  wood  engravings. 

WITH  NOTES  AND  COMMENTS, 

BY  JOSHUA  B.  FLINT,  M.D.,  M.  M.,  S.  S.,  &c.  &c. 

In  One  very  neat  Octavo  Volume  of  about  Five  Hundred  and  Fifty  Pages. 

In  presenting  this  work  to  the  American  profession  for  the  third  time,  but  little  need  be  said  to  solicit  for 
it  a  continuation  of  the  favor  with  which  it  has  been  received.  The  merits  which  have  procured  it  this 
favor,  its  clearness,  conciseness,  and  its  excellent  arrangement,  will  continue  to  render  it  the  favorite  text- 
book ofthe  student  who  wishes  in  a  moderate  space  a  compend  ofthe  principles  and  practice  of  Surgery. 

"This  work  merits  our  warmest  commendations,  and  we  strongly  recommend  it  to  youug  surgeons  as  uu 
admirable  digest  of  the  principles  and  practice  of  modern  Surgery." — Medical  Gazette. 


LEA  &,  BLANCHARD'S  PUBLICATIONS. 


WOW  READY. 

KOTLE'S  MATERIA  MEDICA. 

MATERIA  MEDICA  AND  THERAPEUTICS; 

INCLUDING  THE  PREPARATIONS  OF  THE  PHARMACOPOEIAS  OF  LONDON, 
EDINBURGH,  DUBLIN,  AND  OF  THE  UNITED  STATES. 

WITH    MANY    NEW    MEDICINES. 

BY  J.  FORBES  ROYLE,  M.D,  F.  R.  S.f 

Late  of  the  Medical  Staff  in  the  Bengal  Army,  Professor  of  Materia  Medica  and  Therapeutics,  King's  Col- 
lege. London,  &c.  &c. 

EDITED  BY  JOSEPH  CARSON,  M.D., 

Professor  of  Materia  Medica  in  the  Philadelphia  College  of  Pharmacy,  &c.  &c. 

WITH  NINETY-EIGHT  ILLUSTRATIONS. 
|£J"  See  Specimen  of  the  Cuts,  but  not  of  the  faper  or  Working;  on  next  fag-t* 

In  one  large  octavo  volume  of  about  700  pages. 
Being*  one  of  the  most  beautiful  Medical  works  published  in  this  Country* 

The  want  has  been  felt  and  expressed  for  some  time,  of  a  text-book  on  Materia  Medica,  which 
should  occupy  a  place  between  the  encyclopaedic  works,  such  as  Pereira,  and  the  smaller  treatises 
which  present  but  a  meagre  outline  of  the  science.  It  has  been  the -aim  of  the  author  of  the 
present  work  to  fill  this  vacancy,  and  by  the  use  of  method  and  condensation,  he  has  been  enabled 
to  present  a  volume  to  the  student,  which  will  be  found  to  contain  what  is  necessary  in  a  complete 
and  thorough  text-book  of  the  science,  encumbered  with  few  unnecessary  details.  The  editor, 
Dr.  Carson,  has  added  whatever  was  wanted  to  adapt  it  to  the  Pharmacopeia  of  the  United  States, 
and  it  is  confidently  recommended  to  the  student  and  practitioner  of  medicine,  as  one  of  the  best 
text-books  on  the  subject,  now  before  the  profession. — Great  care  has  been  taken  in  its  mechanical 
execution. 

"  In  regard  to  the  yet  more  essential  constituent,  the  literary  portion  of  the  work,  no  one  who  is 
acquainted  with  the  former  productions  of  Dr.  Royle,  will  doubt  that  the  author  has  discharged  his 
duties  with  the  same  skill  as  the  artist.  The  work  is,  indeed,  a  most  valuable  one,  and  will  till  up 
an  important  gap  that  existed  between  Dr.  Pereira's  most  learned  and  complete  system  of  materia 
medica,  and  the  class  of  productions  at  the  other  extreme,  which  are  necessarily  imperfect  from 
their  small  extent. — British  and  Foreign  Medical  Review. 

Of  the  various  works  that  have  from  time  to  time  appeared  on  materia  medica  on  the  plan  of  the 
one  before  us,  there  is  none  more  deserving  of  commendation.  From  the  examination  which  we 
have  given,  accuracy  and  perspicuity  seem  to  characterize  it  throughout,  as  a  text  book  of  refer- 
ence to  the  student  of  medicine,  and  especially  of  pharmacy  in  its  application  to  medicine,  none 
could  be  better. 

We  think  that  every  one  who  can  afford  it  should  possess  this  excellent  work,  the  value  of  which 
has  been  greatly  enhanced  by  the  additions  of  Dr.  Carson,  than  whom  no  one  is  more  competent 
to  estimate  it  correctly,  and  to  make  such  additions  as  may  adapt  it  for  American  service. — The 
Medical  Examiner. 


BARTLETT  ON  FEVER— New  and  much  improved  edition,  now  ready, 
THE  HISTORY,  DIAGNOSIS  AND  TREATMENT 

OF  THE 

FEVERS  OF  THE   UNITED  STATES. 

BY  ELISHA  BARTLETT,  M.D., 

Professor  of  the  Theory  and  Practice  of  Medicine  in  ihe  Medical  Departmentof  Transylvania  University.  A.C. 

In  One  Octavo  Volume  of  Five  Hundred  and  Fifty  Pages,  beautifully  printed  and  strongly  bound. 

This  is  rather  a  new  work,  than  a  second  edition  of  Dr.  Bartlett's  well  known  treatise  on  Fevers. 
Besides  numerous  improvements  in  the  portion  devoted  to  Typhoid  and  Typhus  Fevers,  the  whole 
of  that  descriptive  of  Periodical  and  Yellow  Fevers,  amounting  to  about  half  the  volume,  is  addi- 
tional. The  work  is  now  what  it  purports  to  be,  a  systematic,  complete  and  methodical  treatise  on 
the  Fevers  of  the  United  States. 


NOW     READY. 

A    MANUAL    OF    TOXICOLOGY. 

BY  ALFRED   S.   TAYLOR. 
EDITED  BY  R.  E.  GRIFFITH,  M.  D.,  &c 

Jn  one  octavo  volume,  to  match  the  "Medical  Jurisprudence"  of  the  same  author. 


SPECIMEN  OF  CUTS  IN 


xmw 


0  Y  L  E  '  S    JT  3HT  no 


MATERIA  MEDICA  AND  THERAPEUTICS 


KtftS 


10  LEA  &  BLANCHARD'S  PUBLICATIONS. 

CHURCHILI/S  MIDWIFERY. 

ON  THE  THEORY  AND  "PRACTICE  OF  MIDWIFERY, 

BY  FLEETWOOD  CHURCHILL,  M.  D.,  M.R.I.  A., 

Licentiate  of  the  College  of  Physicians  in  Ireland  ;  Physician  to  the  Western  Lying- in- Hospital;  Lecturer  OB 

Midwifery,  &c.,  in  the  Richmond  Hospital  Medical  School,  &c.  &c. 

WITH   NOTES  AND  ADDITIONS, 

BY  ROBERT  HUSTON,  M.D., 

Professor  of  Materia  Medica  and  General  Therapeutics,  arid  formerly  of  Obstetrics  and  the  Disease  of  Wo- 
men and  Children  in  the  Jefferson  Medical  College  of  Philadelphia;  President  of  the  Philadelphia 

Medical  Society,  &c.  &c. 
'SECOND  AMERICAN  EDITION. 

WITH  ONE  HUNDRED  AND  TWENTY-EIGHT  It  LUSTRATIONS, 
Engraved  by   Gilbert  from  Drawings  by  Bagg  and  others. 

In  one  beautiful  octavo  volume. 

In  this  age  of  books,  when  much  is  written  in  every  department  of  the  science  of  medicine,  it  is  a  matter  of 
l»o  small  moment  to  the  student,  which  of  the  many  he  shall  choose  for  his  study  in  pupilage,  and  guide  in 
practice.  In  no  department  is  the  choice  more  difficult  than  in  that  of  midwifery  ;  many  excellent  and  truly 
valuable  treatises  in  this  department  of  medicine  have,  within  a  few  years  past,  been  written;  of  this  character 
are  those  of  Dewees,  Velpeau,  Meigs  and  R'gby,  with  due  respect  to  the  authors  of  the  works  just  cited,  we  are 
compelled  to  admit,  that  to  Mr.  Churchill  has  been  reserved  the  honorof  presenting  to  the  profession,  one  more 
particularly  adapted  to  the  want  and  use  of  students,  a  work  rich  in  statistics— clear  in  practice— and  free  in 
style— possessing  no  small  claims  to  our  confidence.— The  New  York  Journal  of  Medicine. 

WILLIAMS'  PATHOLOGY. 

NEW  AND  IMPROVED  EDITION,  BROUGHT  UP  TO  1848,  NEARLY  READY. 

PRINCIPLESHTF   MEDICINE, 

COMPRISIXS 

GENERAL  PATHOLOGY  AND  THERAPEUTICS, 

AXD  A  GENERAL  YIEW  OF 

ETIOLOGY,  NOSOLOGY,  SEMEIOLOGY,  DIAGNOSIS  AND  PROGNOSIS. 
BY  CHARLES  J.  B.  WILLIAMS,  M.D.,  F.R.S., 

Fd'ow  of  the  Royal  College  of  Physicians  &c. 
Second  American,  from  the  Second  London  Edition* 

WITH  NOTES  AND  ADDITIONS,  BY  MEREDITH  OLYMER,  M.D.,  Ac. 

In  one  volume,  octavo. 

P  E  R  E  I  R  A'S   MATERIA   M  E  D  I  C  A . 

With  nearly  Three  Hundred  Engravings  on  Wood. 

A  NEW   EDITION,  LATELY  PUBLISHED. 

THE  ELEMENTS  OF 

MATERIA  MEDICA  AND  THERAPEUTICS, 

COMPREHENDING 

THE  NATURAL  HISTORY,  PREPARATION,  PROPERTIES,  COMPO- 
SITION, EFFECTS  AND  USES  OF  MEDICINES. 
BY  JONATHAN  PEREIRA,  M.D.,  F.R.S.  AND  L.S. 

Member  of  the  Society  of  Pharmacy  of  Paris;  Examiner  in  Materia  Medica  and  Pharmacy  of  the  University 
of  London;  Lecturer  on  Materia  Medica  at  the  London  Hospital.  &c  &c. 
Second  American,  from  the  last  London  Edition,  enlarged  and  improved. 

WITH  NOTES  AND  ADDITIONS  BY  JOSEPH  CARSON,  M.D. 

In  two  volumes,  octavo,  containing  Fifteen  Hundred  very  large  pages,  illustrated  by  Two  Hundred  and 

Seventy-five  Wood-cuts. 

This  encyclopaedia  of  materia  mediea.  for  such  it  may  justly  be  entitled,  gives  the  fullest  and  most  ample  ex- 
position of  materia  mediea  and  its  associate  branches  of  any  work  hitherto  published  in  the  English  language, 
it  abounds  in  rest-arch  and  erudition:  its  statements  of  facts  are  clear  and  methodically  arranged,  while  its 
therapeutical  explanations  are  philosophical,  and  in  accordance  with  sound  clinical  experience.  It  is  equally 
adapted  as  a  text-book  for  students,  or  a  work  of  reference  for  the  advanced  practitioner,  and  no  one  can 
Consult  its  pages  without  profit.  The  editor  has  performed  his  task  with  much  ability  and  judgment.  In  thte 
first  American  edition,  he  adopted  the  Pharmacopeia  of  the  United  States,  and  the  formulas  set  forth  in  that 
standard  authority;  in  the  present  he  has  introduced  an  account  of  substances  that  have  recently  attracted  at- 
tention by  their  therapemic  employment,  together  with  the  mode  of  forming  the  characters  and  uses  of  new 
pharmaceutic  preparations,  and  the  details  of  more  elaborate  and  particular  chemical  investigations,  with 
respect  to  the  nature  of  previously  known  and  already  described  elementary  principles— all  the  important 
indigenous  medicines  of  the  United  States  heretofore  known,  are  also  described.  The  work,  however,  is  too 
well  known  to  need  any  further  remark.  We  have  no  doubt  it  will  have  a  circulation  commensurate  wilh  its 
extraordinary  merits.—  The  New  York  Journal  of  Medicine. 

•'  An  Encyclopaedia  of  knowledge  in  that  department  of  medical  science— by  the  common  consentofthe  pro- 
fession the  most  elaborate  and  scientific  Treatise  on  Materia  Medica  in  our  language."—  Western  Journal  qf 
Medicine  and  Surgery 


LEA  &  BLANCHARD'S  PUBLICATIONS.  11 

WILSON'S  ANATOMY,    New  Edition— Now  Ready,  1847, 

A  SYSTEM    OF    HUMAN  ANATOMY, 
GENERAL  AND  SPECIAL, 

BY  ERASMUS  WILSON,  M.D., 

Lecturer  on  Anatomy,  London. 
THIRD  AMERICAN  FROM  THE  LAST  LONDON  EDITION. 

EDITED  BY  P.  B.  GODDARD,  A.  M.,  M.D., 

Professor  of  Anatomy  in  the  Franklin  Medical  College  of  Philadelphia. 

WITH  TWO  HUNDRED  AND  THIRTY-FIVE  ILLUSTRATIONS  BY  GILBERT. 
In  one  beautiful  octavo  volume  of  over  SIX  HUJYltRED  IJarg-e  fag-e»t 

Strongly  Bound  and  sold  at  a  low  price. 

Since  the  publication  of  the  second  American  edition  of  this  work,  the  author  has  issued  a  new 
edition  in  London,  in  which  he  has  carefully  brought  up  his  work  to  a  level  with  the  most  advanced 
science  of  the  day.  All  the  elementary  chapters  have  been  re-written,  and  such  alterations  made 
through  the  body  of  the  work,  by  the  introduction  of  all  new  facts  of  interest,  illustrated  by  appro- 
priate engravings,  as  much  increase  its  value.  The  present  edition  is  a  careful  and  exact  reprint 
of  the  English  volume,  with  the  addition  of  such  other  illustrations  as  were  deemed  necessary  to  a 
more  complete  elucidation  of  the  text;  and  the  insertion  of  such  of  the  notes  appended  to  the  last 
American  edition  as  had  not  been  adopted  by  the  author  and  embodied  in  his  text ;  together  with 
such  additional  information  as  appeared  calculated  to  enhance  the  value  of  the  work.  It  may  also 
be  stated  that  the  utmost  care  has  been  taken  in  the  revision  of  the  letter-press,  and  in  obtaining 
clear  and  distinct  impressions  of  the  accompanying  cuts. 

It  will  thus  be  seen,  that  every  effort  has  been  used  to  render  this  text-book  worthy  of  a  con- 
tinuance of  the  great  favor  with  which  it  has  been  everywhere  received.  Professors  desirous  of 
adopting  it  for  their  classes  may  rely  on  being  always  able  to  procure  editions  brought  up  to  the 
day. 

This  book  is  well  known  for  the  beauty  and  accuracy  of  its  mechanical  execution.  The  present 
edition  is  an  improvement  over  the  last,  both  in  the  number  and  clearness  of  its  embellishments ; 
it  is  bound  in  the  best  manner  in  strong  sheep,  and  is  sold  at  a  price  which  renders  it  accessible 
to  all. 


CONDIE  ON  CHILDREN.— New  Edition,  1847. 

A  PRACTICAL~TKEATISE  ON 
THE     DISEASES     OF     CHILDREN. 

BY  D.  FRANCIS  CONDIE,  M.  D , 

Fellow  of  the  College  of  Physicians,  Member  of  the  American  Philosophical  Society,  &c. 
In  one  large  octavo  volume. 

J£j*  The  publishers  would  particularly  call  the  attention  of  the  profession  to  an  examination  of  this  book. 

In  the  preparation  of  a  new  edition  of  the  present  treatise,  every  part  of  the  work  has  been  subjected  to  a 
careful  revision;  several  portions  have  been  entirely  rewritten;  while,  throughout,  numerous  additions 
have  been  made,  comprising  all  the  more  important  facts,  in  reference  to  the  nature,  diagnosis,  and  treat- 
ment of  the  diseases  of  infancy  and  childhood,  that  have  been  developed  since  the  appearance  of  the  first 
edition.  It  is  with  some  confidence  that  the  author  presents  this  edition  as  embracing  a  full  and  connected 
view  of  the  actual  state  of  the  pathology  and  therapeutics  of  those  affections  which  most  usually  occur  be- 
tween birth  and  puberty. 

Thla  work  is  being  introduced,  as  a  text-book,  very  extensively  throughout  the  Union. 


CHURCHILL  ON  FEMALES.    New  Edition,  1847.— Now  Ready. 

THE  DISEASES~OF  FEMALES, 

INCLUDING  THOSE  OF 

PREGNANCY  AND  CHILDBED. 

BY  FLEETWOOD   CHURCHILL,  M  D., 

Author  of  "Theory  and  Practice  of  Midwifery,"  &c.  &c. 
FOURTH  AMERICAN,  FROM  THE  SECOND  LONDON  EDITION,  WITH  ILLUSTRATIONS 

EDITED,    WITH    NOTES, 
BY    ROBERT     M.      HUSTON,    M.D.,   fcc.&o. 

In  one  volume,  8vo. 

The  rapid  sale  of  three  editions  of  this  valuable  work,  stamp  it  so  emphatically  with  the  approbation  of  the 
profession  of  this  country,  that  the  publishers  in  presenting  a  fourth  deem  it  merely  necessary  to  observe, 
that  every  care  has  been  taken,  by  the  editor,  to  supply  any  deficiencies  which  may  have  existed  iu  former 
impressions,  and  to  bring  the  work  fully  up  to  the  date  of  publication. 


12  LEA   &  BLANCHARD'S  PUBLICATIONS. 

LIBRARY  OF  OPHTHALMIC  MEDICINE  AND  SURGERY. 
Brought  up  to  1847. 

A  TREATISE  ON  THE~DISEASES  OF  THE  EYE, 

BY    W.    LAWRENCE,    F.R.S., 

Surgeon  Extraordinary  to  the  Queen,  Surgeon  to  St.  Bartholomew's  Hospital,  &c.  &c. 
A    NEW    EDITION, 

With  many  Modifications  and  Additions,  and  the  Introduction  of  nearly  two  hundred  Illustrations. 

BY     ISAAC     HAYS,    M.  D., 

Surgeon  to  Wills'  Hospital,  Physician  to  the  Philadelphia  Orphan  Asylum,  &c.  Sec.     . 

In  one  very  large  octavo  volume  of  near  900  pages,  with  twelve  plates  and  numerous  wood-cuts  through 

the  text. 

This  is  among  the  largest  and  most  complete  works  on  this  interesting  and  difficult  branch  of  Medica 
Science. 

The  early  call  for  a  new  edition  of  this  work,  confirms  the  opinion  expressed  by  the  editor  of  its  great 
value,  and  has  stimulated  him  to  renewed  exertions  to  increase  its  usefulness  to  practitioners,  by  incorporat-1 
ing  in  it  the  recent  improvements  in  Ophthalmic  Practice.  In  availing  himself,  as  he  has  freely  done,  of 
the  observations  and  discoveries  of  his  fellow-laborers  in  the  same  field,  the  editor  has  endeavored  to  do  so 
with  entire  fairness,  always  awarding  to  others  what  justly  belongs  to  them.  Among  the  additions  which 
have  been  made,  may  be  noticed,— the  description?  of  several  affections  not  treated  of  in  the  original,— an 
account  of  the  catoptric  examination  of  the  eye,  and  of  its  employment  as  a  means  of  diagnosis. — one  hun- 
dred and  seventy -six  illustrations,  some  of  Hiem  from  original  drawings,— and  a  very  full  index.  There  have 
also  been  introduced  in  ihe  several  chapters  on  the  more  important  diseases,  the  results  of  the  editor's  ex- 
perience in  regard  to  their  treatment,  derived  from  more  than  a  quarter  of  a  century's  devotion  to  the  subject, 
during  all  of  which  period  he  has  been  attached  to  some  public  institution  for  the  treatment  of  diseases  of  the 
eye. 

"  We  think  there  are  few  medical  works  which  could  be  so  generally  acceptable  as  this  one  will  be  to  the 
profession  on  this  side  of  the  Atlantic.  The  want  of  a  scientific  and  comprehensive  treatise  on  Diseases 
of  the  Kye,  has  been  much  deplored  That  want  is  now  well  supplied.  The  reputation  of  Mr.  Lawrence 
as  an  Oculist  has  been  long  since  fully  established;  his  great  merit  consists  in  the  clearness  of  his  style 
and  the  very  practical  tenor  of  his  work.  The  value  of  the  present  beautiful  edition  is  greatly  enhanced, 
by  the  important  additions  made  by  the  editor.  Dr.  Hays  has,  for  nearly  a  quarter  of  a  century,  been  con- 
nected with  public  institutions  for  the  treatment  of  Diseases  of  the  Eye.  and  few  men  have  made  better  im- 
provement than  he  has,  of  such  extensive  opportunities  of  acquiring  a  thorough  knowledge  of  the  subject. 
The  wood-cuts  are  executed  with  great  accuracy  and  beauty,  and  no  man,  who  pretends  to  treat  disease* 
of  the  eye,  should  be  without  this  work."— Lancet. 


JONES  ON  THEJTYE,    Now  Ready, 

THE  PRINCIPLES~AND  PRACTICE 
OF  OPHTHALMIC  MEDICINE  AND  SURGERY. 

BY  T.  WHARTON  JONES,  F.R.S.,  &c.  &c. 

"WITH    ONE    HUNDRED    AND    TEN    ILLUSTRATIONS. 

EDITED  BY  ISAAC  HAYS,  M.D.;  &c. 

In  One  very  neat  Volume,  large  royal  I2mo.,  with  Four  Plates,  plain  or  colored,  and  Ninety- 
eight  well  executed  Wood-cuts. 

This  volume  will  be  found  to  occupy  a  place  hitherto  unfilled  in  this  department  of  medical  science. 
The  aim  of  the  author  has  been  to  produce  a  work  which  should,  in  a  moderate  compass,  be  suffi- 
cient to  serve  both  as  a  convenient  text-book  for  students  and  as  a  book  of  reference  for  practitioners, 
suitable  for  those  who  do  not  desire  to  possess  the  larger  and  encyclopaedic  treatises,  such  as 
Lawrence's.  Thus,  by  great  attention  to  conciseness  of  expression,  a  strict  adherence  to  arrange- 
ment, and  the  aid  of  numerous  pictorial  illustrations,  he  has  been  enabled  to  embody  in  it  the  prin- 
ciples of  ophthalmic  medicine,  and  to  point  out  their  practical  application  more  fully  than  has 
been  done  in  any  other  publication  of  the  same  size.  The  execution  of  the  work  will  be  found 
to  correspond  with  its  merit.  The  illustrations  have  been  engraved  and  printed  with  care,  and  the 
•whole  is  confidently  presented  as  in  every  way  worthy  the  attention  of  the  profession. 

a  We  are  confident  that  the  reader  will  find,  on  perusal,  that  the  execution  of  the  work  amply  fulfils  the 
promise  of  the  preface,  and  sustains,  in  every  point,  the  already  high  reputation  of  the  author  as  an  ophthal- 
mic surgeon,  as  well  as  a  physiologist  and  pathologist.  The  book  is  evidently  the  result  of  much  labor  and 
research,  and  has  been  written  with  the  greatest  care  and  attention  ;  it  possesses  that  best  quality  which  a 
general  work,  like  a  system,  or  manual,  can  show,  viz:— the  quality  of  having  all  the  materials  whenceso- 
ever  derived,  so  thoroughly  wrought  up.  and  digested  in  the  author's  mind,  as  to  come  forth  with  the  freshness 
and  impressiveness  of  an  original  production.  We  regret  that  we  have  received  the  book  at  so  late  a  period 
as  precludes  our  giving  more  than  a  mere  notice  of  it,  as  although  essentially  and  necessarily  a  compilation, 
it  contains  many  things  which  we  should  be  glad  to  reproduce  in  our  pages,  whether  in  the  shape  of  new 
pathological  views,  of  old  errors  corrected,  or  of  sound  principles  of  practice  in  doubiful  cases  clearly  laid 
down.  But  we  dare  say  most  of  our  readers  will  shortly  have  an  opportunity  of  seeing  these  in  their  original 
locality,  as  we  entertain  little  doubt  that  this  book  will  become  what  its  author  hoped  it  might  become,  a 
manual  for  daily  reference  and  consultation  by  the  student  and  the  general  practitioner.  The  work  is 
marked  by  thai  correctness,  clearness  and  precision  of  style  which  distinguish  all  the  productions  of  the 
learned  author." — The  British  and  Foreign  Medical  Review. 


HI  •WniWUll!  3BT  W 

Q      f    *    mL$A;&  BtLANCHARD'S  PUBLICATIONS.       -r  T  g  r        13 
NEW  AND  COMPLETE  MEDICAL  BOTANY. 

N  0  W   READ  Y. 

MEDICAlTBOTANY, 

OR,  A  DESCRIPTION  OF  ALL  THE  MORE  IMPORTANT  PLANTS  USED  IN 

MEDICINE,    AND    OF    THEIR    PROPERTIES,    USES    AND 

MODES  OF  ADMINISTRATION. 

BY  R.  EGLESFELD  GRIFFITH,  M.  D.    &c.  &c. 

In  one  large  octavo  volume. 

With  about  three  hundred  and  fifty  Illustrations  on  Wood. 
Specimens  of  the  Cuts  are  annexed,  but  not  so  well  printed  as  in  the  work,  rior  on  as  good  paper. 

This  work  is  intended  to  supply  a  want  long  felt  in  this  country,  of  some  treatise  present- 
ing correct  systematic  descriptions  of  medicinal  plants,  accompanied  by  representations  of 
the  most  important  of  them,  and  furnished  at  a  price  so  moderate  as  to  render  it  generally 
accessible  and  useful.  In  the  arrangement,  the  author  has  treated  more  fully  of  those 
plants  which  are  known  to  be  of  the  greatest  importance;  and  more  especially  of  such  as 
are  of  native  origin  ;  while  others,  rarely  used,  are  briefly  noticed,  or  mentioned  only  by 
name.  In  all  cases,  the  technical  descriptions  are  drawn  up  in  accordance  with  the  existing 
state  of  botanical  knowledge,  and  in  order  that  these  maybe  fully  appreciated,  even  by  those 
not  proficients  in  the  science,  an  Introduction  has  been  prepared,  containing  a  concise  view 
of  Vegetable  Physiology,  and  the  Anatomy  and  Chemistry  of  Plants.  Besides  this,  a  very 
copious  GLOSSARY  of  botanical  terms  has  been  appended,  together  with  a  most  complete 
INDEX,  giving  not  only  the  scientific  but  also  the  common  names  of  the  species  noticed  in 
it.  It  will  thus  be  seen  that  the  work  presents  a  view  not  only  of  the  properties  and  medical 
virtues  of  the  various  species  of  the  vegetable  world,  but  also  of  their  organization,  compo- 
sition and  classification. 

To  the  student,  who  is  really  anxious  to  study  Botany  for  those  great  purposes  which  ren- 
der it  so  necessary  for  the  advancement  of  Medical  Science,  and  who  has  been  obliged  to 
rest  satisfied  with  such  imperfect  knowledge  as  can  be  obtained  from  the  different  treatises 
on  the  Materia  Medica,  the  present  work  will  be  of  great  utility  as  a  text-book  and  guide  in 
his  researches,  as  it  presents  in  a  condensed  form,  all  that  is  at  present  known  respecting 
those  vegetable  substances  which  are  employed  to  alleviate  suffering  and  to  minister  to  the 
wants  of  man.  It  will  also  be  found  extremely  convenient  to  practitioners  through  the 
country,  who  are  anxious  to  obtain  a  knowledge  of  the  medicinal  plants  occurring  in  their 
vicinity,  and  who  are  unwilling  to  procure  the  scarce  and  high-priced  works  which  are  at 
present  the  only  ones  accessible  on  this  important  branch  of  medical  knowledge. 

Great  care  has  been  taken  to  render  the  mechanical  execution  satisfactory. 


NOW     PREPARING, 
AND    TO     BE     READY    AT    AN    EARLY    DAY, 

AN  ANALYTICAL  COMPEND  OF  THE  VARIOUS  BRANCHES  OF 

PRACTICAL  MEDICINE,  SURGERY,  ANATOMY, 

MIDWIFERY,  DISEASES  OF  WOMEN  AND  CHILDREN, 
•Jfledica  and  Therapeutic^  Physiology, 

oars  20  etna's'  .A  urn)  ' 


B¥  JOHN  NEILL,  M  D, 

Demonstrator  of  Anatomy  in  the  University  of  Pennsylvania,  and 

F.    GURNEY    SMITH,    M.D., 
Lecturer  on  Physiology  in  the  Philadelphia  Association  for  Medical  Instruction. 

To  make  one  large  royal  Duodecimo  volume,  with  numerous  Illustrations  on  Wood. 
It  is  the  intention  of  the  publishers  to  page  this  work  in  such  a  way,  that  it  can  be  done  up  in 
separate  divisions,  and  in  paper  to  go  by  mail;  no  one  division  will  cost  over  50  cents,  thus  pre- 
senting separate  MANUALS  on  the  various  branches  of  medicine,  and  at  a  very  low  price. 


NEARLY    READY. 

BURROWS  ON  DISORDERS  OF  CEREBRAL  CIRCULATION, 

AND  ON  THE  CONNECTION  BETWEEN  AFFECTIONS  OF  THE  BRAIN  AND 

DISEASES  OF  THE  HEART. 
In  one  neat  octavo  volume,  with  six  colored  plates. 


SPECIMEN  OF  THE  ILLUSTRATIONS  HI 

GRIFFITH'S   MEDICAL  BOTANY. 


LEA  &  BLANCHARD'S  PUBLICATIONS.  15 


THE  GREAT  MEDICAL  LIBRARY, 
THE  CYCLOP/EDIA  OF  PRACTICAL  MEDICINE ; 

COMPRISING  TREATISES  ON  THE 

NATURE  AND  TREATMENT  OF  DISEASES, 

MATERIA  MEDICA  AND  THERAPEUTICS, 

DISEASES  OF  WOMEN  AND  CHILDREN, 
MEDICAL  JURISPRUDENCE,  &c.  &c. 

EDITED   BT     - 

JOHN  FORBES,  M.  D.,  F.R.S., 
ALEXANDER   TWEEDIE,   M.D.,  F.R.S., 

AND 

JOHN   CONOLLY,   M.D. 

REVISED,  WITH  ADDITIONS, 

BY  ROBLEY  DUNGLISON,  M.  D. 

THIS  WORK  IS  NOW  COMPLETE,  AND  FORMS 

FOUR  LARGE  SUPER-ROYAL,  OCTAVO  VOLUMES. 

CONTAINING  THIRTY-TWO  HUNDRED  AND  FIFTY-FOUR 

UNUSUALLY  LARGE  PAGES  IN  DOUBLE  COLUMNS, 

PRINTED  ON  GOOD  PAPER,  WITH  A  NEW  AND  CLEAR  TYPE. 

THE  WHOLE  WELL  AND  STRONGLY  BOUND, 
WITH  RAISED  BANDS  AND  DOUBLE  TITLES. 
Or,  to  he  had  in  twenty-four  parts,  at  Fifty  Cents  each. 

For  a  list  of  Articles  and  Authors,  together  with  opinions  of  the  press,  see  Supplement  to  the  No- 
vember number  of  the  Medical  News  and  Library  for  1845. 

This  work  having  been  completed  and  placed  before  the  profession,  has 
been  steadily  advancing  in  favor  with  all  classes  of  physicians.  The  nu- 
merous advantages  which  it  combines,  beyond  those  of  any  other  work ;  the 
weight  which  each  article  carries  with  it,  as  being  the  production  of  some 
physician  of  acknowledged  reputation  who  has  devoted  himself  especially 
to  the  subject  confided  to  him;  the  great  diversity  of  topics  treated  of;  the 
compendiousness  with  which  everything  of  importance  is  digested  into  a 
comparatively  small  space  ;  the  manner  in  which  it  has  been  brought  up 
to  the  day,  everything  necessary  to  the  American  practitioner  having  been 
added  by  Dr.  Dunglison ;  the  neatness  of  its  mechanical  execution ;  and 
the  extremely  low  price  at  which  it  is  afforded,  combine  to  render  it  one  of 
the  most  attractive  works  now  before  the  profession.  As  a  book  for  con- 
stant and  reliable  reference,  it  presents  advantages  which  are  shared  by  no 
other  work  of  the  kind.  To  country  practitioners,  especially,  it  is  abso- 
lutely invaluable,  comprising  in  a  moderate  space,  and  trifling  cost,  the 
matter  for  which  they  would  have  to  accumulate  libraries,  when  removed 
from  public  collections.  The  steady  and  increasing  demand  with  which 
it  has  been  favored  since  its  completion,  shows  that  its  merits  have  been 
appreciated,  and  that  it  is  now  universally  considered  as  the 

LIBRARY  FOR  CONSULTATION  AND  REFERENCE. 




A  2MLA.GHM  Uk'lCElMT  ATfD  CHEAP   WORK. 

•SMITH  &  HORNER'S  ANATOMICAL  ATLAS, 

Just  Published,  Price  Five  Dollars  in  Parts. 

AN 

ANATOMICAL    ATLAS 
ILLUSTRATIVE  OF  THE  STRUCTURE  OF  THE  HUMAN  BODY. 

BY  HENRY  H.  SMITH,  M.D., 

uLlJ  Fellow  of  the  College  of  Physicians,  <f-e. 

UNDER  THE  SUPERVISION  OF 

WILLIAM  E.  HORNER,  M.D., 

Professor  of  Anatomy  in  the  University  of  Pennsylvania. 
In  One  large  Volume,  Imperial  Octavo. 

This  work  is  but  just  completed,  having  been  delayed  over  the  time  intended  by  the  great  difficulty  in  giving 
to  the  illustrations  the  desired  finish  and  perfection.  It  consists  of  five  parts,  whose  contents  are  as  follow*: 

PART     I.  The  Bones  and  Ligaments,  with  one  hundred  and  thirty  engravings. 

PART   II.  The  Muscular  and  Dermoid  Systems,  with  ninety-one  engravings. 

PART  III.  The  Organs  of  Digestion  and  Generation,  with  one  hundred  and  ninety-one  engravings. 

PART  IV.  The  Organs  of  Respiration  and  Circul-ation,  with  ninety-eight  engravings. 

PART  V.  The  Nervous  System  and  the  Senses,  with  one  hundred  and  twenty-six  engravings. 
Forming  altogether  a  complete  System  of  Anatomical  Plates,  of  nearly 

SIX   HUNDRED  AND   FIFTY   FIGURES, 

executed  in  the  best  style  of  art,  and  making  one  iarge  imperial  octavo  volume.    Those  who  do  not  want  it  in 
parts  can  have  the  work  bound  in  extra  cloth  or  sheep  at  an  extra  cost. 

This  work  possesses  novelty  both  in  the  design  and  the  execution.  It  is  the  first  attempt  to  apply  engraving 
on  wood,  on  a  large  scale,  to  the  illustration  of  human  anatomy,  and  the  beauty  of  the  parts  issued  induces  the 
publishers  to  flatter  themselves  with  the  hope  of  the  perfect  success  of  their  undertaking.  The  plan  of  the 
work  is  at  once  novel  and  convenient.  Each  page  is  perfect  in  itself,  the  references  being  immediately  under 
the  figures,  so  that  the  eye  takes  in  the  whole  at  a  glance,  and  obviates  the  necessity  of  continual  reference 
backwards  and  forwards.  The  cut?  are  selected  from  the  best  and  most  accurate  sources ;  and,  where  neces- 
sary, original  drawings  have  been  made  from  the  admirable  Anatomical  Collection  of  the  University  of  Penn 
sylyania.  It  embraces  all  the  late  beautiful  discoveries  arising  from  the  use  of  the  microscope  in  the  investi- 
gation of  tlie  minute  structure  of  the  tissues. 

In  the  getting  up  of  this  very  complete  work,  the  publishers  have  spared  neither  pains  nor  expense,  and  they 
now  present  it  to  the  profession,  with  the  full  confidence  that  it  will  be  deemed  all  that  is  wanted  in  a  scientific 
and  artistical  point  of  view,  while,  at  the  same  time,  its  very  low  price  places  it  within  the  reach  of  all. 

It  is  particularly  adapted  to  supply  the  place  of  skeletons  or  subjects,  as  the  profession  will  see  by  examining  the  list 
»f  plates 


"These  figures  are  well  selected,  and  present  a  complete  and  accurate  representation  of  that  wonderful  fabric, 
the  human  body.  The  plan  of  this  Atlas,  which  renders  it  so  peculiarly  convenient  for  the  student,  and  its 
•uperb  artistical  execution,  have  been  already  pointed  out.  We  must  congratulate  the  student  upon  the 
completion  of  this  atlas,  as  it  is  the  most  convenient  work  of  the  kind  that  lias  yet  appeared;  and,  we  must 
add,  the  very  beautiful  manner  in  which  it  is  'got  up'  is  so  creditable  to  the  country  as  to  be  flattering  to  our 
national  pride." — American  Medical  Journal. 

"This  is  an  exquisite  volume,  and  a  beautiful  specimen  of  art.  We  have  numerous  Anatomical  Atlases, 
but  we  will  venture  to  say  that  none  equal  it  in  cheapness,  and  none  surpass  it  in  faithfulness  and  spirit.  We 
strongly  recommend  to  our  friends,  both  urban  and  suburban,  the  purchase  of  this  excellent  work,  for  which 
both  editor  and  publisher  deserve  tfljb  thanks  of  the  profession." — Medical  Examiner. 

"We  would  strongly  recommend  it,  not  only  to  the  student,  but  also  to  the  working  practitioner,  who, 
although  grown  rusty  in  the  toils  of  his  harness  still  has  the  desire,  and  often  the  necessity,  of  refreshing  his 
knowledge  in  this  fundamental  part  of  the  science  of  medicine." — frew  York  Journal  of  Medicine  and  Surg. 

"  The  plan  of  this  Atlas  is  admirable,  and  its  execution  superior  to  any  thing  of  the  kind  before  published  m 
this  country.  It  is  a  real  labour-saving  affair,  and  we  regard  its  publication  as  the  greatest  boon  that  could  be 
conferred  on  the  student  of  anatomy.  It  will  be  equally  valuable  to  the  practitioner,  by  affording  him  an  easy 
means  of  recalling  the  details  learned  in  the  dissecting  room,  and  which  are  soon  forgotten." — American  Medi- 
cal Journal. 

•'  It  is  a  beautiful  as  well  as  particularly  useful  design,  which  should  be  extensively  patronized  by  physicians, 
surgeons  and  medical  students." — Boston  Med.  and  Surg.  Journal. 

"It  has  been  the  aim  of  the  author  of  the  Atlas  to  comprise  in  it  the  valuable  points  of  all  previous  works,  to 
embrace  the  latest  microscopical  observations  on  the  anatomy  of  the  tissues,  and  by  placing  it  at  a  moderate 
price  to  enable  all  to  acquire  it  who  may  need  its  assistance  in  the  dissecting  or  operating  room,  or  other  field 
of  practice." — Western  Journal  of  Med.  and  Surgery. 

''These  numbers  complete  the  series  of  this  beautiful  work,  which  fully  merits  the  praise  bestowed  upon  the 
earlier  numbers.  We  regard  all  the  engravings  as  possessing  an  accuracy  only  equalled  by  their  beauty, 
and  cordially  recommend  the  work  to  all  engaged  in  the  study  of  anatomy." — New  York  Journal  of  Medicine 
and  Surgery. 

"A  more  elegant  work  than  the  one  before  us  could  not  easily  be  placed  by  a  physician  upon  the  table  of 
his  student.1* — Wetter*  Journal  of  Medicine  and  Surgery. 

;f  We  were  much  pleased  with  Part  I,  but  the  Second  Part  gratifies  us  still  more,  both  as  regards  the  attract- 
ive nature  of  the  subject,  (The  Dennoid  and  Muscular  Systems,)  and  the  beautiful  artistical  execution  of  the 
Jlustrations.  We  have  here  delineated  the  most  accurate  microscopic  views  of  some  of  the  tissues,  as,  for 
instance,  the  cellular  and  adipose  tissues,  the  epidermis,  rete  mucosum  and  cutis  vera.  the  sebaceous  and 
r>f  rspiraiory  organs  of  the  skin,  the  perspiratory  glands  and  hairs  of  the  skin,  and  the  hair  and  nails.  Then 
fellows  ilir-  general  anatomy  of  the  muscles,  and,  lastly,  their  separate  delineations.  We  would  recommend 
this  Anatomical  Atlas  to  our  readers  in  the  very  strongest  terms."— Ntw  York  Journal  of  Medicine  and  Sur> 


LEA  &  BLANCHARD'S  PUBLICATIONS.  17 

HQRNER'S  ANATOMY, 

NEW  EDITION. 


SPECIAL  ANATOMY  AND   HISTOLOGY. 

BY  WILLIAM  E.  HORNER,  M.D., 

PROFESSOR  OF  ANATOMY  IW  THE  UNIVERSITY  OF  PENNSHVANIA,  &C.,  &C. 

Seventh  edition. 

With  many  improvements  and  additions.    In  two  octavo  volumes,  with  illustrations  on 

wood. 

This  standard  work  has  been  so  long  before  the  profession,  and  has  been  so  extensively 
used,  that,  in  announcing  thenewedition.it  is  only  necessary  to  state,  that  it  has  under- 
gone a  most  careful  revision  ;  the  author  has  introduced  many  illustrations  relating  to  Mi- 
croscopical Anatomy,  and  has  added  a  large  amount  of  text  on  those  various  points  of 
investigation  that  are  rapidly  advancing  and  attracting  so  much  attention.  This  new  edition 
has  been  arranged  to  refer  conveniently  to  the  illustrations  in  Smith  and  Horner's  Anato- 
mical Atlas. 

"The  name  of  Professor  Homer  is  a  sufficient  voucher  for  the  fidelity  and  accuracy  of 
any  work  on  anatomy,  but  if  any  further  evidence  could  be  required  of  the  value  of  the  pre- 
sent publication,  it  is  afforded  by  the  fact  of  its  having  reached  a  seventh  edition.  It  is 
altogether  unnecessary  now  to  inquire  into  the  particular  merits  of  a  work  which  has  been 
so  long  before  the  profession,  and  is  so  well  known  as  the  present  one,  but  in  announcing  a 
new  edition,  it  is  proper  to  state  that  it  has  undergone  several  modifications,  and  has  been, 
much  extended,  so  as  to  place  it  on  a  level  with  the  existing  advanced  state  of  anatomy. — 
The  histological  portion  has  been  remodelled  and  rewritten  since  the  last  edition;  numerous 
wood  cuts  have  been  introduced,  and  specific  references  are  made  throughout  the  work  to 
the  beautiful  figures  in  the  Anatomical  Atlas,  by  Dr.  H.  H.  Smith." — The  American  Medical 
Journal,  for  January,  1847. 


HORNER'SJ3ISSSCTOR. 

THE  UNITED  STATES  DISSECTOR, 

BEING  A  NEW  EDITION,  WITH  EXTENSIVE  MODIFICATIONS, 
AND  ALMOST  REWRITTEN,  OF 

"BORJVJEIP&  FKMCTICML,  MAWTOMIW 

IN  ONE  VERY  NEAT  VOLUME,  ROYAL  12MO. 
With  many  Illustrations  on  Wood. 

The  numerous  alterations  and  additions  which  this  work  has  undergone,  the  improve- 
ments which  have  been  made  in  it,  and  the  numerous  wood-cuts  which  have  been  intro- 
duced, render  it  almost  a  new  work. 

It  is  the  standard  work  for  the  Students  in  the  University  of  Pennsylvania. 

Some  such  guide-book  as  the  above  is  indispensable  to  the  student  in  the  dissecting  room, 
and  this,  prepared  by  one  of  the  most  accurate  of  our  anatomists,  may  claim  to  combine  as 
many  advantages  as  any  other  extant.  It  has  been  so  favorably  received  that  the  publish- 
ers have  issued  the  fourth  edition,  which  comes  forth  embellished  by  various  wood  cuts.— 
The  copy  for  which  we  are  indebted  to  the  publishers,  although  received  by  us  a  fortnight 
since,  gives  proof  in  its  appearance  that  it  has  already  seen  service  at  the  dissecting  table, 
where  students  have  found  it  a  valuable  guide. —  The  Western  Journal  of  Medicine  and  <Sur- 
gery. 


., 


HOPE  ON  THE  HEART.    NEW  EDITION,  JUST  PUBLISHED. 

A  TREATISE  ON  THE  DISEASES 

OF  THE  HEART  AND  GREAT  VESSELS, 

AND  ON  THE  AFFECTIONS  WHICH  MAY  BE  MISTAKEN  FOR  THEM. 

Comprising  the  author's  view  of  the  Physiology  of  the  Heart's  Action  and  Sounds  as  demonstrated  by  his  ex- 
periments on  the  Motions  and  Sounds  in  1830  and  on  the  Sounds  in  1834—5. 

BY  J.  HOPE,  M.  D.,  F.  R.  S  ,  &c.  &c. 
Second  American  from  the  third  London  edition.    With  Notes  and  a  Detail  of  Recent  Experiments. 

BY  C.  W.  PENNOCK,  M.  D.,  &c. 
In  one  octavo  volume  of  nearly  six  hundred  pages  with    thographic  plates. 


18  LEA  &  BLANCHARD'S  PUBLICATIONS. 

WORKS  BY  PROFESSOR  W.  P.  DEWEES. 

NEW    EDITIONS. 

DEWEES'S  JPJWIFERY, 

A  COMPREHENSIVE  SYSTEM  OF  MIDWIFERY. 

CHIEFLY  DESIGNED    TO  FACILITATE  THE  INQUIRIES  OF  THOSE  WHO  MAY  BE  PUR- 
SUING THIS  BRANCH  OF  STUDY. 

ILLUSTRATED  BY  OCCASIONAL  CASES  AND  MANY  ENGRAVINGS. 
Eleventh  Edition,  with  the  Author's  last  Improvements  and  Corrections. 

BY  WILLIAM  P.  DEWEES,  M.D., 

LATE  PROFESSOR  OF  MIDWIFERY  IN  THE  UNIVERSITY  OF  PENNSYLVANIA,  ETC. 

,  In  one  volume,  octavo. 

*  That  this  work,  notwithstanding  the  length  of  time  it  has  been  before  the  profession,  and  the  numerous  treat- 
ises that  have  appeared  since  it  was  written,  should  have  still  maintained  its  ground,  and  passed  to  edition  after 
edition,  is  sufficient  proof  that  in  it  the  practical  talents  of  the  author  were  fully  placed  before  the  profes- 
sion. Of  the  book  itself  it  would  be  superfluous  to  speak,  having  been  so  long  and  so  favorably  known  through- 
out the  country  as  to  have  become  identified  with  American  Obstetrical  Science. 


DEWEES  ON^  FEMALES. 

A  TREATISE  ON  THE  DISEASES  OF  FEMALES, 

BY  WILLIAM  P.  DEWEES,  M.  D.,  &c., 

LATE  PROFESSOR  OF  MIDWIFERY  IN  THE  UNIVERSITY  OF  PENNSYLVANIA,  ETC. 

NINTH  EDITION, 
With  the  Author's  last  Improvements  and  Corrections. 

In  one  octavo  volume,  with  plates. 


DEWEES    ON    CHILDREN. 

A  TREATISE  ON  THE 

PHYSICAL  AND  MEDICAL  TREATMENT  OF  CHILDREN, 

BY  WILLIAM  P.  DEWEES,  M.D., 

LATE  PROFESSOR  OF  MIDWIFERY  IN  THE  UNIVERSITY  OF  PENNSYLVANIA,  ETC.  ETC. 

NINTH    EDITION. 

In  one  volume  octavo. 

This  edition  embodies  the  notes  and  additions  prepared  by  Dr.  Dewees  before  his  death,  and  will  be  found 
much  improved. 

The  objects  of  this  work  are,  1st,  to  teach  those  who  have  the  charge  of  children,  either  as  parent  orguardian, 
the  most  approved  methods  of  securing  and  improving  their  physical  powers.  This  is  attempted  by  pointing 
out  the  duties  which  the  parent  or  the  guardian  owes  for  this  purpose,  to  this  interesting  but  helpless  class  of 
beings,  and  the  manner  by  which  their  duties  shall  be  fulfilled.  And  2d.  to  render  available  a  long  experience 
to  those  objects  of  our  affection  when  they  become  diseased.  In  attempting  this,  the  author  has  avoided  as 
much  as  possible,  "technicality,"  and  has  given,  if  he  does  not  flatter  himself. too  much  to  each  disease  of 
•which  he  treats,  its  appropriate  and  designating  characters,  with  a  fidelity  that  will  prevent  any  two  being 
confounded  together,  with  the  best  ctode  of  treating  them,  that  either  his  own  experience  or  that  of  others  has 
suggested. 

Physicians  cannot  too  strongly  recommend  the  use  of  thfs  book  in  all  families. 


ASHWELL  ON  THE  DISEASES  OF  FEMALES. 


A  PRACTICAL  TREATISE  ON  THE 

DISEASES  PECULIAR  TO  WOMEN, 

ILLUSTRATED  BY  CASES 
DERIVED    FROM    HOSPITAL   AND    PRIVATE    PRACTICE. 

BY  SAMUEL  ASHWELL,  M.  D., 

Member  of  the  Royal  College  of  Physicians;  Obstetric  Physician  and  Lecturer  to  Guy's  Hospital,  &c. 

EDITED  BY  PAUL  BECK  GODDARD,  M.  D. 

The  whole  complete  in  one  large  octavo  volume. 

"  The  most  able,  and  certainly  the  most  standard  and  practical  work  on  female  diseases  that  we 
ba?e  yet  seen." — Medico- Chirurgical  Review. 


American  practitioner,  ro  commend  it  still  more  strongly  to  the  profession,  the  publishers 
rreat  expense  in  preparing  this  edition  with  larger  type,  finer  paper,  and  stronger  binding  w 
It  is  edited  with  reference  particularly  to  American  practice,  by  Dr.  Condie;  and  with  thes 
provements,  the  price  is  still  kept  so  low  as  to  be  within  the  reach  of  all,  and  to  render  it  am< 


LEA  &  BLANCHARD'S  PUBLICATIONS.  19 

WATSON'S  PRACTICE  OF  PHYSIC. 

NEW    EDITION,    BROUGHT    UP    TO    SEPTEMBER   1847. 
LECTURES    ON    THE 

PRINCIPLES  AND  PRACTICE  OF  PHYSIC. 

DELIVERED  AT  KING'S  COLLEGE,  LONDON, 

BY  THOMAS  WATSON,  M.D.,  &c.  &c. 
Third  American,  from  the  Last  London  Edition, 

REVISED,  WITH  ADDITIONS, 

BY  D.  FRANCIS   CONDIE,  M.  D., 

Author  of  a  work  on  the  "Diseases  of  Children,"  &c. 

In  One  Octavo  Volume 

Of  nearly  ELEVEN  HUNDRED  LARGE  PAGES,  strongly  bound  with  raised  bands. 
The  rapid  sale  of  two  large  editions  of  this  work  is  an  evidence  of  its  merits,  and  of  its  general  favor  with  the 
American  practitioner.    To  commend  it  still  more  strongly  to  the  profession,  the  publishers  have  gone  to  a 

e,  finer  paper,  and  stronger  binding  with  raised  bands, 
ractice,  by  Dr.  Condie;  and  with  these  numerous  im- 
the  reach  of  all,  and  to  render  it  among  the  cheapest 

works  offered.to  the  profession.  It  has  been  received  with  the  utmost  favor  by  the  medical  press,  both  of  this 
country  and  of  England,  a  few  of  the  notices  of  which,  together  with  a  letter  from  Professor  Chapman,  are 
submitted. 

Philadelphia,  September  27th,  1844. 

^  Watson's  Practice  of  Physic,  in  my  opinion,  is  among  the  most  comprehen- 
sive works  on  the  subject  extant,  replete  with  curious  and  important  matter,  and 
written  with  great  perspicuity  and  felicity  of  manner.  As  calculated  to  do  much 
good,  I  cordially  recommend  it  to  that  portion  of  the  profession  in  this  country 
who  may  be  influenced  by  my  judgment. 

N.  CHAPMAN,  M.D., 

Professor  of  the  Practice  and  Theory  of  Medicine  in  the  University  of  Pennsylvania. 

"We  know  of  no  work  better  calculated  for  being  placed  in  the  hands  of  the  student,  and  for  a  text-book,  and 
as  such  we  are  sure  it  will  be  very  extensively  adopted.  On  every  important  point  the  author  seems  to  have 
posted  up  his  knowledge  to  the  day." — American  MedicalJournal. 

One  of  the  most  practically  useful  books  that  ever  was  presented  to  the  student — indeed  a  more  admirable 
rnmmary  of  general  and  special  pathology,  and  of  the  application  of  therapeutics  to  diseases,  we  are  free  to 
say  has  not  appeared  for  very  many  years.  The  lecturer  proceeds  through  the  whole  classification  of  human 
ills,  a  capite  ad  calcem,  showing  at  every  step  an  extensive  knowledge  of  his  subject,  with  the  ability  of  commu- 
nicating his  precise  ideas  in  a  style  remarkable  for  its  clearness  and  simplicity." — N.  Y.  Journal  of  Medi- 
cine and  Surgery. 

"  We  are  free  to  state  that  a  careful  examination  of  this  volume  has  satisfied  us  that  it  merits  all  the  com- 
mendation bestowed  on  it  in  this  country  and  at  home.  It  is  a  work  adapted  to  the  wants  of  young  practi- 
tioners, combining  as  it  does,  sound  principles  and  substantial  practice.  It  is  not  too  much  to  say  that  it  is  a 
representative  of  the  actual  state  of  medicine  as  taught  and  practised  by  the  most  eminent  physicians  of  the 
present  day,  and  as  such  we  would  advise  everyone  about  embarking  in  the  praetice  of  physic  to  provide  him- 
self with  a  copy  of It."—  Western  Journal  of  Medicine  and  Surgery. 

IVOCEL'S   PATHOLOGICAL  ANATOMY. 

THE 

PATHOLOGICAL  ANATOMY  OF  THE  HUMAN  BODY. 

BY  JULIUS  VOGEL,  M.D.,  &c. 
TRANSLATED  FROM  THE  GERMAN,  WITH  ADDITIONS, 

BY  GEORGE  E.  DAY,  M.D.;  &c. 

KUustratetJ  feg  uptoartis  of  ©rte  S^imtjreU  $lafn  anti  Colored  JSnjjrabfnas* 
In  One  neat  Octavo  Volume. 

In  our  last  number  we  gave  a  pretty  full  analysis  of  the  original  of  this  very  valuable  work,  to  which  w« 
must  refer  the  reader.  We  have  only  to  add  here  our  opinion  that  the  translator  has  performed  his  task  in  an 
excellent  manner,  and  has  enriched  the  work  with  many  valuable  additions. — The  British  and  Foreign  Meduai 
Kevieiv. 

It  is  decidedly  the  best  work  on  the  subject  of  which  it  treats  in  the  English  language,  and  Dr.  Day,  whose 
translation  is  well  executed,  has  enhanced  its  value  by  a  judicious  selection  of  the  most  important  figures  Iroa 
the  atlas,  which  are  neatly  engraved.— The  London  Medical  Gazette. 


20  LEA  &   BLANCHARD'S  PUBLICATIONS. 

A  NEW  EDITION  OP  THE  GREAT 

M  E  D  I  0  A  L_L  E  X I  0  0  H . 

A  Dictionary  of 

MEDICAL     SCIENCE, 

CONTAINING  A  CONCISE  ACCOUNT  OF  THE  VARIOUS  SUBJECTS  AND  TERMS;  WITH  THE 
FRENCH    AND   OTHER  SYNONYMES:   NOTICES   OF  CLIMATES  AND  OF  CELE- 
BRATED MINERAL  WATERS;  FORMULAE  FOR  VARIOUS  OFFICINAL 
AND  EMPIRICAL  PREPARATIONS,  &c. 

BY  ROBLEY  DUNGLISON,  M.  D., 

PROFESSOR  OF  THE  INSTITUTES  OF  MEDICINE,  ETC.  IN  JEFFEKSON  MEDICAL  COLLEGE,  PHILADELPHIA. 

Sixth  edition,  revised  and  greatly  enlarged.  In  one  royal  octavo  volume  of  over  800  very  large  pages, 
double  columns.  Strongly  bound  in  the  best  leather,  raised  bands. 

"The  most  complete  medical  dictionary  in  the  English  language."—  Western  Lancet. 

"  We  think  that  'the  author's  anxious  wish  to  render  the  work  a  satisfactory  and  desirable— if  not  indispen- 
sable— Lexicon,  m  which  the  student  may  search  without  disappointment  for  every  term  that  has  been 
legitimated  in  the  nomenclature  of  the  science,'  has  been  fully  accomplished.  Such  a  work  is  much  needed 
by  all  medical  students  and  young  physicians,  and  will  doubtless  continue  in  extensive  demand.  It  is  a 
lasting  monument  of  the  industry  and  literary  attainments  of  the  author,  who  has  long  occupied  the  highest 
rank  among  the  medical  teachers  of  America  " — The  New  Orleans  Medical  and  Surgical  Journal. 

"The  simple  announcement  of  the  fact  that  Dr.  Dunglison's  Dictionary  has  reached  a  sixth  edition,  is  almost 
as  high  praise  as  could  be  bestowed  upon  it  by  an  elaborate  notice.  It  is  one  of  those  standard  works  that  have 
been  '  weighed  in  the  balance  and  (not)  been  found  wauling  '  It  has  stood  the  test  of  experience,  and  the  fre- 
quent calls  for  new  editions,  prove  conclusively  that  it  is  held  by  the  profession  and  by  students  in  the  highest 
estimation.  The  present  edition  is  not  a  mere  reprint  of  former  ones;  the  author  has  for  some  time  been 
laboriously  engaged  in  revising  and  making  such  alterations  and  additions  as  are  required  by  the  rapid  pro- 
gress of  our  science,  and  the  introduction  of  new  terms  into  our  vocabulary.  In  proof  of  this  it  is  stated  '  that 
the  present  edition  comprises  nearly  two  thousand  five  hundred  subjects  and  terms  not  contained  in  the  last. 
Many  of  these  had  been  introduced  into  medical  terminology  in  consequence  of  the  progress  of  the  science, 
and  others  had  escaped  notice  in  previous  revisions.'  We  think  that  the  earnest  wish  of  the  author  has  been 
accomplished ;  and  that  he  has  succeeded  in  rendering  the  work  'a  satisfactory  and  desirable—  if  not  indis- 
pensable— Lexicon,  in  which  the  student  may  search,  without  disappointment,  for  every  term  that  has  been 
legitimated  in  the  nomenclature  of  the  science.'  This  desideratum  he  has  been  enabled  to  attempt  in  suc- 
cessive editions,  by  reason  of  the  work  not  being  stereotyped  ;  and  the  present  edition.certainly  offers  stronger 
claims  to  the  attention  of  the  practitioner  and  student,  than  any  of  its  predecessors.  The  work  is  got  up  in 
the  usual  good  taste  of  the  publishers,  and  we  recommend  it  in  full  confidence  to  all  who  have  not  yet  supplied 
themselves  with  so  indispensable  an  addition  to  their  libraries." — The  New  York  Journal  of  Medicine. 

A  NEW  EDITION  OF  DUNGLISON'S  HUMAN  PHYSIOLOGY, 

HUMAN   PHYSIOLOGY, 

WITH  THREE  HUNDRED  AND  SEVENTY  ILLUSTRATIONS. 
BY  ROBLEY  DUNGLISON,  M.D., 

PROFESSOR  OF  THE  INSTITUTES  OF  MEDICINE  IN  THE  JEFFERSON  MEDICAL  COLLEGE,  PHILADELPHIA,  ETC., ETC. 

Sixth  edition,  greatly  improved. — In  two  large  octavo  volumes,  containing  nearly  1350  pages. 
"  It  is  but  necessary  for  the  Author  to  say,  that  all  the  cares  that  were  bestowed  on  the  preparation  of  the 
fifth  edition  have  been  extended  to  the  sixth,  and  even  to  a  greater  amount.  Nothing  of  importance  that  has 
been  recorded  since  its  publication,  has,  he  believes,  escaped  his  attention.  Upwards  of  seventy  illustrations 
have  been  added;  and  many  of  the  former  cuts  have  been  replaced  by  others.  The  work,  he  trusts,  will  be 
found  entirely  on  a  level  with  the  existing  advanced  stale  of  physiological  science." 

In  mechanical  and  artistical  execution,  this  edition  is  far  in  advance  of  any  former  one. 
The  illustrations  have  been  subjected  to  a  thorough  revision,  many  have  been  rejected  and 
their  places  supplied  with  superior  ones,  while  numerous  new  wood-cuts  have  been  added 
wherever  perspicuity  or  novelty  seemed  to  require  them. 

.  "Those  who  have  been  accustomed  to  consult  the  former  editions  of  this  work,  know  with  how  much 
care  and  accuracy  every  fact  and  opinion  of  weight,  on  the  various  subjects  embraced  in  a  treatise  on 
Physiology,  are  collected  and  arranged,  so  as  to  present  the  latest  and  best  account  of  the  science  To  suctt 
we  need  hardly  say,  that,  in  this  respect,  the  present  edition  is  not  less  distinguished  than  those  which  have 
preceded  it.  In  the  two  years  and  a  half  which  have  elapsed  since  the  last  or  fifth  edition  appeared,  nothing 
of  consequence  that  has  been  recorded  seems  to  have  been  omitted.  Upwards  of  seventy  illustrations  have 
been  added,  and  many  of  the  former  cuts  have  been  replaced  by  others  of  better  execution.  These  mostly 
represent  the  minute  structures  as  seen  through  the  microscope  and  are  necessary  for  a  proper  comprehension 
of  the  modern  discoveries  in  this  department " — The  Medical  Examiner. 

The  "  Human  Physiology"  of  Professor  Dunglison  has  long  since  taken  rank  as  one  of  the  medical  classics 
in  our  language.  Edition  after  edition  has  been  issued,  each  more  perfect  than  the  la>t,  till  now  we  have  the 
sixth,  with  upwards  of  seventy  new  illustrations.  To  say  that  it  is  by  far  the  best  text-book  of  physiology  ever 
published  in  this  country,  is  but  echoing  the  general  voice  of  the  profession.  It  is  simple  and  concise  in  style, 
clear  in  illustration,  and  altogether  on  a  level  with  the  existing  advanced  state  of  physiological  science.  The 
additions  to  the  present  edition  are  extremely  numerous  and  valuable;  scarcely  a  fact  worth  naming  which 
has  a  bearing  upon  the  subject  seems  to  have  been  omitted.  All  t!ie  recent  writers  on  physiology,  both  in  the 
French.  German  and  English  languages,  have  been  consulted  and  freely  used,  and  the  facts  lately  revealed 
through  the  agency  of  organic  chemistry  and  the  microscope  have  received  a  due  share  of  attention.  As  it  is, 
we  cordially  recommend  the  work  as  in  the  highest  degree  indispensable  both  to  students  and  practitioners 
of  medicine. — New  York  Journal  of  Medicine. 

The  most  full  and  complete  system  of  physiology  in  our  language.—  Western  Lancet. 


LEA  &  BLANCHARD'S  PUBLICATIONS.  21 

DUNGLISON'S.  THERAPEUTICS. 

NEW  AND  MUCH   IMPROVED   EDITION. 

GENERAL  THERAPEUTICS  AND  MATERIA  MEDICA, 

With  One  Hundred  and  Twenty  Illustrations. 

ADAPTED  FOR  A  MEDICAL  TEXT-BOOK. 

BY  ROBLEY  DUNGLISON,  M.D., 

Professor  of  Institutes  of  Medicine,  &c.  in  Jefferson  Medical  College;  Late  Professor  of  Materia  Medica,  &c. 
in  the  Universities  of  Virginia  and  Maryland,  arid  in  Jefierson  Medical  College. 

Third  Edition,  Revised  and  Improved,  in  two  octavo  volumes,  well  bound. 

In  this  edition  much  improvement  will  he  found  over  the  former  ones  The  author  has  subjected  it  to  a  tho- 
rough revision,  and  has  endeavored  to  so  modify  the  work  as  to  make  it  a  more  complete  and  exact  exponent 
of  the  present  state  of  knowledge  on  the  imporiant  subjects  of  which  it  treats.  The  favor  with  which  the  former 
editions  were  received,  demanded  that  the  present  should  be  rendered  still  more  worthy  of  the  patronage  of  the 
profession,  and  this  alteration  will  be  found  not  only  in  the  matter  of  the  volumes,  but  also  in  the  numerous 
illustrations  introduced  and  the  general  improvement  in  the  appearance  of  the  work. 

''This  is  a  revised  and  improved  edition  of  the  author's  celebrated  book,  entitled  '  General  Therapeutics;'  an 
account  of  the  different  articles  of  the  Materia  Medica  having  been  incorporated  with  it.  The  work  has,  in 
fact,  been  entirely  remodelled,  so  that  it  is  now  the  most  complete  and  satisfactory  exponent  of  the  existing  state 
of  Therapeutical  Science,  within  the  moderate  limits  of  a  text-book,  of  any  hitherlo  published  What  gives  the 
work  a  superior  value,  in  our  judgment,  is  the  happy  blending  of  Therapeutics  and  Materia  Medica  a^  they  are, 
or  ought  to  be  taught  in  all  our  medical  schools;  going  no  farther  inio  the  nature  and  commercial  hisiory  of 
drugs,  than  is  indispensable  for  the  medical  student.  This  gives  to  the  treatise  a  clinical  and  practical  charac- 
ter, calculated  to  benefit  in  the  highest  degree,  both  students  and  practitioners.  We  shall  adopt  it  as  a  text- 
book for  our  classes,  while  pursuing  this  branch  of  medicine,  and  shall  be  happy  to  learn  that  it  has  been 
adopted  as  such,  in  all  of  our  medical  institutions ." — The  N.  Y.  Journal  oj  Medicine. 

"Our  junior  brethren  in  America  will  find  in  these  volumes  of  Professor  Dunglison.  a  'THESAURUS  MBDICA- 
MINUM,' more  valuable  than  a  large  purse  of  gold." — London  Mrrlico-Chir'i./rgical  Review. 

DUNGLISON  ON  NEW  REMEDIES. 

NEW  EDITION,   BROUGHT  UP  TO  OCTOBER  1846. 

NEW    REMEDIES. 

BY  ROBLEY  DUNGLISON,   M.D.,  &c.  &c. 

Fifth  edition,  with  extensive  additions.     In  one  neat  octavo  volume. 

The  numerous  valuable  therapeutical  agents  which  have  of  late  years  been  introduced  into  the  Materia 
Medica.  render  it  a  difficult  matter  for  the  practitioner  to  keep  up  with  the  advancement  of  the  science,  espe- 
cially as  the  descriptions  of  them  are  difficult  of  access,  being  scattered  so  widely  thiougn  transactions  of 
learned  societies,  journals,  monographs.  &c.  &c.  To  obviate  this  difficulty,  and  to  place  within  reach  of  the 
profession  this  important  information  in  a  compendious  form,  is  the  object  of  the  present  volume,  and  the  num- 
ber of  editions  through  which  it  has  passed  show  that  its  utility  has  not  been  underrated. 

The  author  has  taken  particular  care  that  this  edition  shall  be  completely  brought  up  to  the  present  day. — 
The  therapeutical  agents  added,  which  may  be  regarded  as  newly  introduced  into  the  Materia  Medica.  to- 
gether with  old  agents  brought  forward  with  novel  applications,  and  which  may  therefore  be  esteemed  as 
"New  Remedies,"  are  the  following:— Ben/oic  Acid,  Chromic  Acid,  Gallic  Acid.'JNilric  Acid.  Phosphate  of 
Ammonia,  Binelli  Water,  Brocchieri  Water,  Atropia  Beerberia,  Chloride  of  Carbon  (Chloroform),  Digitalia, 
Electro-Magnetism,  Ergotin,  Ox-gall,  Glycerin,  Hsemospasy,  Hcemostasis,  Hagenia  Abyssinica.  Honey  Bee, 
Protochloride  of  Mercury  and  Quinia.  lodoform,  Carbonate  of  Lithia,  Sulphate  of  Manganese,  Matico,  Double 
Iodide  of  Mercury  and  Morphia,  lodhydrate  of  Morphia,  Iodide  of  lodhydrate  of  Morphia,  Muriate  of  Mor- 
phia and  Codeia,  Naphthalin,  Piscidia  Erythrina,  Chloride  of  Lead.  Nitrate  of  Potassa.  Arseniateof  Quinia, 
Iodide  of  Quinia,  Iodide  of  Cinchonia.  Iodide  of  lodhydrate  of  Quinia,  Lactate  of  Quinia,  Pyroacetic  Acid, 
(Naphtha,  Acetone)  Hyposulphate  of  Soda.  Phosphate  of  Soda,  Iodide  of  lodhydrate  of  Strychnia,  Double  Iodide 
of  Zinc  and  Strychnia,  Double  Iodide  of  Zinc  and  Morphia,  and  Valerianate  of  Zinc. 

:  <k  A  work  like  this  is  obviously  not  suitable  for  either  critical  or  analytical  review.  It  is.  so  far  as  it  goes,  a 
dispensatory,  in  which  an  account  is  given  of  the  chemical  and  physical  properties  of  all  the  articles  recently 
added  to  the  Materia  Medica  and  their  preparations,  witlia  notice  of  the  diseases  for  which  they  are  prescribed, 
the  doses,  mode  of  administration  &c." — The  Medical  Examiner. 

THE   MEDICAL    STUDENTf 

OR  AIDS  TO  THE  STUDY  OF  MEDICINE. 

A  REVISED  AND  MODIFIED  EDITION. 

BY    ROBLEY    DUNGLISON,    M.  D. 

In  one  neat  I2mo.  volume. 


HUMAN    HEALTH: 

OR,  THE   INFLUENCE   OF  ATMOSPHERE  AND  LOCALITY.  CHANGE  OF  AIR  AND  CLIMATE, 

SEASONS,   FOOD.  CLOTHING,  BATHING   AND  MINERAL  SPRINGS,  EXERCISE, 

SLEEP,  CORPOREAL  AND  INTELLECTUAL  PURSUITS,  &c.  &c., 

ON  HEALTHY  MAN:  CONSTITUTING 

ELEMENTS    OF    HYGIENE. 

BY  ROBLEY  DUNGLISON,  M.  D. 

A  New  Edition  with  many  Modifications  and  Additions.    In  one  Volume,  8vo. 


LEA  &  BLANCHARD'S  PUBLICATIONS. 


AMEEICAN    PRACTICE    OF    MEDICINE. 

BY     PROFESSOR    DUNGLI8ON. 
THIRD  EDITION,  MUCH  IMPROVED,  NOW  READY,  BROUGHT  UP  TO  184a 

THE  PRACTICETOF  MEDICINE; 

A    TREATISE     ON 

SPECIAL  PATHOLOGY  AND  THERAPEUTICS. 

THIRD  EDITION. 

BY  ROBLEY  DUNGLISON,  M.  D. 

Professor  of  the  Institutes  of  Medicine  in  the  Jefferson  Medical  College;  Lecturer  on  Clinical  Medicine,  Sfe 

In  Two  large  Octavo  Volumes  of  over  Fourteen  Hundred  Pages. 

Since  the  publication  of  the  second  edition  of  this  work,  short  as  the  interval  has  been,  so  much 
activity  has  prevailed  in  the  advancement  of  medical  knowledge,  that  a  thorough  revision  of  it 
became  necessary.  Several  pathological  affections,  too,  had  been  omitted,  which  are  now  insert- 
ed. The  greatly  enlarged  dimensions  of  the  work  will  sufficiently  exhibit  the  amount  of  additions, 
which  might  escape  superficial  observation. 

In  preparing  the  present  edition,  the  author  has  carefully  scanned  the  various  monographs  on 
pathology  and  therapeutics,  which  have  appeared  alone  or  in  different  cyclopaediac  and  other  works, 
transactions  of  learned  societies,  and  journals.  He  has  also  availed  himself  of  the  valuable  matter 
contained  in  recent  treatises  having  a  similar  scope  with  his  own,  of  which  he  may  specify  more 
particularly  those  of  Canstatt,  Fuchs,  and  Wunderlich  of  Germany;  Valliex  and  Grisolle  of  France; 
and  Dickson  of  this  country.  The  Pathological  Anatomy  of  Vogel,  and  the  Animal  Chemistry  of 
Simon,  have  also  yielded  him  valuable  assistance.  Nothing  of  importance  that  has  been  recorded 
since  the  publication  of  the  last  edition  has,  he  believes,  escaped  his  attention;  and  altogether  he 
trusts  that  the  present  edition  will  be  regarded  as  an  adequate  exponent  of  the  existing  condition 
of  knowledge  on  the  important  departments  of  which  it  treats. 

Notwithstanding  the  numerous  and  attractive  works  which  have  of  late  been  issued  on  the  Practice  of 
Physic,  these  volumes  keep  their  place  as  a  standard  text-book  for  the  student,  and  manual  of  reference  for 
the  practitioner.  The  care  with  which  the  author  embodies  everything  of  value  from  all  sources,  the  industry 
with  which  all  discoveries  of  interest  or  importance  are  summed  up  in  succeeding  editions,  the  excellent 
order  and  system  which  is  everywhere  manifested,  and  the  clear  and  intelligible  style  in  which  his  thoughts 
are  presented,  render  his  works  universal  favorites  with  the  profession. 

"In  the  volumes  before  us,  Dr.  Dunglison  has  proved  that  his  acquaintance  with  the  present  facts  and 
doctrines,  wheresoever  originating,  is  most  extensive  and  intimate,  and  the  judgment,  skill,  and  impartiality 
•with  which  the  materials  of  the  work  have  been  collected,  weighed,  arranged,  and  exposed,  are  strikingly 
manifested  in  every  chapter.  Great  care  is  everywhere  taken  to  indicate  the  source  of  information,  and 
under  the  head  of  treatment,  formulae  of  the  most  appropriate  remedies  are  every  where  introduced.  In  con- 
clusion, we  congratulate  the  students  and  junior  practitioners  of  America  on  possessing  in  the  present 
volumes  a  work  of  standard  merit,  to  which  they  may  confidently  refer  in  their  doubts  and  difficulties." — 
Brit,  and  For.  Med.  Rev. 

"  Since  the  foregoing  observations  were  written,  we  have  received  a  second  edition  of  Dunglison's  work, 
a  sufficient  indication  of  the  high  character  it  has  already  attained  in  America,  and  justly  attained."—  Ibid. 

"In  the  short  space  of  two  years,  a  second  edition  of  Dr.  Dunglison's  Treatise  on  Special  Pathology  and 
Therapeutics  has  been  called  for,  and  is  now  before  the  public  in  the  neat  and  tasteful  dress  in  which  Lea 
&  Blanchard  issue  all  their  valuable  publications.  We  do  not  notice  the  fact  for  the  purpose  of  passing  any 
studied  eulogy  upon  this  work,  which  is  now  too  well  known  to  the  profession  to  need  the  commendation  of 
the  press. 

"  A  cursory  examination  will  satisfy  any  one,  that  great  labor  has  been  bestowed  upon  these  volumes, 
and  on  a  careful  perusal  it  will  be  seen  that  they  exhibit  the  present  state  of  our  knowledge  relative  to 
special  pathology  and  therapeutics.  The  work  is  justly  a  great  favorite  with  students  of  medicine,  whose 
exigencies  the  learned  author  seems  especially  to  have  consulted  in  its  preparation."—  Western  Jour,  of 
Med.  and  Surg. 

"  This  is  a  work  which  must  at  once  demand  a  respectful  consideration  from  the  profession,  emanating  as 
it  does  from  one  of  the  most  learned  and  indefatigable  physicians  of  our  country. 

"This  arrangement  will  recommend  itself  to  the  favorable  consideration  of  all,  for  simplicity  and  com- 
prehensiveness. We  have  no  space  to  go  into  details,  and,  therefore,  conclude  by  saying,  that  although 
isolated  defects  might  be  pointed  out,  yet  as  a  whole,  we  cheerfully  recommend  it  to  the  profession,  as 
embracing  much  important  matter  which  cannot  easily  be  obtained  from  any  other  source." —  Western  Lancet. 


WILSON    ON    THE    SKIN. 

NEW    AND    IMPROVED    EDITION,  (1847.) 

ON    DISEASE8~OF    THE    SKIN. 

BY  ERASMUS   WILSON,   F.R.S., 

AUTHOR  OF  "A  SYSTEM  OF  HUMAN  ANATOMY,"  ETC. 

SECOND  AMERICAN,  FROM  THE  SECOND  LONDON  EDITION. 
In  one  neat  octavo  volume,  extra  cloth,  of  Four  Hundred  and  Forty  Pages,  with  Eight  Steel  Plates. 

accurately  and  beautifully  colored. 

Copies  may  be  had  with  or  without  the  plates,  or  the  plates  may  be  had  separate,  neatly  and  strongly 
done  up. 

The  increase  of  this  work  by  nearly  a  hundred  pages  shows  that  this  edition  is  much  improved,  and  brought 
up  to  the  date  of  publication. 


LEA   &  BLANCHARD'S  PUBLICATIONS.  23 

BRODIE'S   SURGICAL  WORKS. 


SELECT  SURGICAL  WORKS  OF  SIR  BENJ'N  BRODIE,  BART.,  V.  F.  R.  S. 

CONTAINING  HIS 

CLINICAL   LECTURES    ON     SURGERY, 
LECTURES  ON  THE  DISEASES  OF  THE  URINARY  ORGANS, 

AND 

OBSERVATIONS    ON    THE    DISEASES    OF    THE    JOINTS. 
The  whole  in  one  neat  octavo  volume,  strongly  bound. 

ALSO, 
Eacli  of  the  above  works  to  be  had  separately,  done  up  in  cloth* 


MULLER'S  PHYSICS  AND  METEOROLOGY— Nearly  Ready, 

PRINCIPLES  OF   PHYSICS  AND  METEOROLOGY. 
BY   J.    MULLER, 

PROFESSOR  OF  PHYSICS  AT  THE  UNIVERSITY  OF  FREIBURG. 

Illustrated  with  nearly  Five  Hundred  and  Fifty  Engravings  on  Wood,  and  Two  Colored  Plates. 

In  One  Octavo  Volume. 

"The  Physics  of  Muller  is  a  work  superb,  complete,  unique;  the  greatest  want  known  to  English  Science 
eould  not  have  been  better  supplied.  The  work  is  of  surpassing  interest.  The  value  of  this  contribution  to 
the  scientific  records  of  this  country  may  be  duly  estimated  by  the  fact,  that  the  cost  of  the  original  drawings 
and  engravings  alone  has  exceeded  the  sum  of  £2000."-  Lancet,  March  1847. 


SOLLY  ON  THE  BRAIN— Nearly  Ready. 
THE  HUMAN  BRAIN:  ITS  STRUCTURE,  PHYSIOLOGY,  AND  DISEASES. 

WITH 

A  DESCRIPTION  OF  THE  TYPICAL  FORMS  OF  BRAIN  IN  THE  ANIMAL  KINGDOM, 
BY  SAMUEL  SOLLY,  F.R.S., 

Senior  Assistant-Surgeon  to  St.  Thomas'  Hospital;  and  Lecturer  on  Clinical  Surgery,  &c. 

SECOND  EDITION,  GREATLY  ENLARGED. 

One  Octavo  Volume,  with  120  Cuts. 


MILLER'S  SURGICAL  WORKS. 

THE  PRINCIPLES  OF  SURGERY. 

BY  JAMES  MILLER,  F.R.S.E.,  F.R.C.S.E., 

Professor  of  Surgery  in  the  University  of  Edinburg,  &c. 
In  one  neat  octavo  volume,  to  match  the  Author's  volume  on  "  Practice." 

"  We  feel  no  hesitation  in  expressing  our  opinion  that  it  presents  the  philosophy  of  the  science 
more  fully  and  clearly  than  any  other  work  in  the  language  with  which  we  are  acquainted."— Phi- 
ladelphia Medical  Examiner. 

LATELY   PUBLISHED. 

THE  PRACTICE  OF  SURGERY. 

BY  JAMES  MILLER, 

Professor  of  Surgery  in  the  University  of  Edinburg. 

In  one  neat  octavo  volume. 
This  work  is  printed  and  bound  to  match  the  "  Principles  of  Surgery,"  by  Professor  Miller,  lately 

issued  by  L.  &  B.    Either  volume  may  be  had  separately. 

"  This  work,  with  the  preceding  one,  forms  a  complete  text-book  of  surgery,  and  has  been  under- 
taken by  the  author  at  the  request  of  his  pupils.  Although  as  we  are  modestly  informed  in  the 
preface,  it  is  not  put  forth  in  rivalry  of  the  excellent  works  on  practical  surgery  which  already  exist, 
we  think  we  may  take  upon  ourselves  to  say,that  it  will  form  a  very  successful  and  formidable 
rival  to  most  of  them.  While  it  does  not  offer  the  same  attractive  illustrations,  with  which  some  of 
our  recent  text-books  have  been  embellished,  and  while  it  will  not,  as  indeed  is  not  its  design,  set 
aside  the  more  complete  and  elaborate  works  of  reference  which  the  profession  is  in  possession  of, 
we  have  no  hesitation  in  stating  that  the  two  volumes  form,  together,  a  more  complete  text-book 
of  surgery  than  any  one  that  has  been  heretofore  offered  to  the  student."— The  Northern  Journal 
of  Medicine. 


24  LEA  &  BLANCHARD'S  PUBLICATIONS. 

CARPENTER'S  NEW  WORK. 


A  MANUAL,  OR  ELEMENTS  OF  PHYSIOLOGY, 

MJTCLVDIJrG   PHYSIOLOGICAL    AJTJLTOMY, 

FOR  THE  USE  OF  THE  MEDICAL  STUDENT. 

BY  WILLIAM  B.  CARPENTER,  M.  D.,  F.  R.  S  , 

FTTLLEfclAN  PROFESSOR  OF  PHYSIOLOGY  IN  THE  ROYAL  INSTITUTION  OF  GREAT  BRITAIN,  ETC. 

With  one  hundred  and  eighty  illustrations.    In  one  octavo  volume  of  566  pages.    Elegantly  printed  to  match 

his  "  Principles  of  Human  Physiology." 

This  work,  though  but  a  very  short  time  published,  has  attracted  much  attention  from  all  engaged  in  teach- 
ing the  science  of  medicine,  and  has  been  adopted  as  a  text-book  by  many  schools  throughout  the  country. — 
The  clearness  and  conciseness  with  which  all  the  latest  investigations  are  enunciated  render  it  peculiarly 
well  suited  for  those  commencing  the  study  of  medicine.  It  is  profusely  illustrated  with  beautiful  wood  en- 
gravings, and  is  confidently  presented  as  among  the  best  elementary  text-books  on  Physiology  in  the  lan- 
guage. 


NEW    AND    MUCH    IMPROVED    EDITION.      NOW    READY. 

CARPENTER'S  HUMAN  PHYSIOLOGY. 

BROUGHT  UP  TO  SEPTEMBER,  1847. 

PRINCIPLES  OF  HUMAN  PHYSIOLOGY, 

WITH  THEIR  CHIEF  APPLICATIONS  TO 

PATHOLOGY,    HYGIENE,   AND    FORENSIC    MEDICINE. 
BY  WILLIAM  B.  CARPENTER,  M.  D.,  F.  R.  S.,  &c. 

Third  American,  from  a  New  and  Revised  London  Edition, 

WITH  NOTES  AND  ADDITIONS, 

BY  MEREDITH  CLYMER,  M.  D.,  &c. 

With  Three  Hundred  and  Seventeen   Wood-cut  and  other  Illustration*, 

In  one  octavo  volume,  of  over  750  closely  and  beautifully  printed  pages. 

The  character  of  the  present  work  is  too  well  known  and  established  to  need  any  commendation.  Within 
a  period  of  four  years,  it  has  passed  through  three  editions  both  in  this  country  and  Great  Britain.  It  will  be 
seen,  that  the  present  edition  has  been  essentially  modified  and  improved;  and,  besides  attentive  revision,  has 
undergone  material  alteration  in  the  arrangement. 

Many  of  the  Notes  of  the  American  Editor  to  former  editions  have  been  incorporated  by  the  Author  in  the 
text  of  the  present;  others  remain;  whilst  such  additions  have  been  made,  as  the  progress  of  the  science 
required. 

Besides  the  additions  of  the  Author,  the  Editor  has  been  enabled  to  add  numerous  illustrations;  which, 
accompanied  by  copious  references,  will,  he  trusts,  be  found  to  enhance  the  value  of  this  edition,  and  to 
peculiarly  adapt  it  to  the  Student  of  Physiology.  There  are  one  hundred  and  fifteen  more  wood-cuts  in  this 
than  in  the  third  English  edition,  and  one  hundred  and  one  more  than  in  the  last  American. 


SUPPLEMENT  TO  THE  ENCYCLOPEDIA  AMERICANA,  IIP  TO  THE  YEAR  1847. 

ENCYCLOPEDIA  AMERICANA-Supplementary  Vol. 

A  POPULAR  DICTIONARY 

OF  ARTS,  SCIENCES,  LITERATURE,  HISTORY,  POLITICS  AND 

BIOGRAPHY. 

VOL.    XIV. 

EDITED  BY  HENRY  VETHAKE,  LL.  D., 

Vice-Provost  and  Professor  of  Mathematics  in  the  University  of  Pennsylvania,  Author  of  "A  Treatise  on  Poli- 
tical Economy." 

In  One  large  Octavo  Volume  of  over  Six  Hundred  and  Fifty  double  columned  pages. 

The  numerous  subscribers  who  have  been  waiting  the  completion  of  this  volume  can  now  perfect 
their  sets,  and  all  who  want  a  Register  of  the  Events  of  the  last  Fifteen  Years,  for  the  Whole 
World,  particularly  embracing  interesting  scientific  investigations  and  discoveries,  can  obtain  this 
volume  separately,  price  Two  Dollars  uncut  in  cloth,  or  Two  Dollars  and  Fifty  Cents  in  leather, 
to  match  the  styles  in  which  the  publishers  have  been  selling  sets. 

Subscribers  in  the  large  cities  can  be  supplied  on  application  at  any  of  the  principal  bookstores  ; 
and  persons  residing  in  the  country  can  have  their  sets  matched  by  sending  a  volume  in  charge  of 
friends  visiting  the  city. 

Complete  sets  furnished  at  very  low  prices  in  various  bindings. 

"The  Conversations  Lexicon  (Encyclopaedia  Americana)  has  become  a  household  book  in  all  the  intelli- 
gent families  in  America,  and  is  undoubtedly  the  best  depository  of  biographical,  historical,  geographical  and 
political  information  of  that  kind  which  discriminating  readers  require.  There  is  in  the  present  vo!um«  much 
matter  purely  scientific,  which  was  all  the  more  acceptable  to  us  that  it  was  unexpected." — Sillimari's  Journal. 


LEA  &  BLANCHARD'S  PUBLICATIONS.  25 

FOWJVES'  CHEMISTRY  FOR  STUDENTS. 

NEW  AND  IMPROVED  EDITION,  1847. 

ELEMENTARY    CHEMISTRY. 

THEORETICAL  AND  PRACTICAL. 

BY  GEORGE  FOWNES,  PH.  D., 

Chemical  Lecturer  in  the  Middlesex  Hospital  Medical  School,  &c.  &c. 
With  Numerous  Illustrations.    Second  American  Kdition.    Kdited,  with  Additions, 

BY  ROBERT  BRIDGES,  M.D., 

Professor  of  General  and  Pharmaceutical  Chemistry  in  the  Philadelphia  College  of  Pharmacy,  &c.  &c. 

In  one  large  duodecimo  volume,  sheep  or  extra  cloth. 

Though  this  work  has  been  so  recently  published,  it  has  already  been  adopted  as  a  text-book  by  many  of  the 
Medical  Institutions  throughout  the  country.  As  a  work  for  the  first  cltlss  student,  and  as  an  introduction  to 
the  larger  systems  of  Chemistry,  such  as  Graham's,  there  has  been  but  one  opinion  expressed  concerning  it, 
and  it  may  now  be  considered  as 

THE  TEXT-BOOK  FOR.  THE  CHEJfllCJtL,  STUDEJTT. 

"  An  admirable  exposition  of  the  present  slate  of  chemical  science,  simply  and  clearly  written,  and  display- 
ing a  thorough  practical  knowledge  of  its  details,  as  well  as  a  profound  acquaintance  with  its  principles.  The 
illustrations,  and  the  whole  getting-up  of  the  book,  merit  our  highest  praise."—  British  and  Foreign  Med.  Rev, 

"  Remarkable  for  its  clearness,  and  the  most  concise  and  perspicuous  work  of  the  kind  we  have  seen,  admi- 
rably calculated  to  prepare  the  student  for  the  more  elaborate  treatises." — Pharmaceutical  Journal. 

This  work  of  Fownes,  while  not  enlarging  on  the  subject  as  much  as  Graham,  is  far  more  lucid  and  expanded, 
than  the  usual  small  introductory  works.  Persons  using  it  may  rely  upon  its  being  kept  up  to  the  day  by  fre- 
quent revisions. 

NEW    EDITION    OF   GRAHAIVVS   CHEMISTRY,    PREPARING. 

THE  ELEMENTS  OF  CHEMISTRY. 

INCLUDING  THE   APPLICATION  OF  THE  SCIENCE  TO  THE  ARTS. 
With  Numerous  Illustrations. 

BY  THOMAS  GRAHAM,  F.  R.  S.  L.  and  E.  D., 

Professor  of  Chemistry  in  University  College,  London,  &c.  &c. 

SECOND   AMERICAN.   FROM   THE   SECOND   ENGLISH  EDITION. 

WITH  NOTES  AND  ADDITIONS  BY  ROBERT  BRIDGES,  M.  D.,  &c.  &c. 

In  one  volume  octavo. 


SIMON'S    CHEMM3TRY   OF    MAN. 

ANIMAL   CHEMISTRY, 

WITH  REFERENCE  TO  THE  PHYSIOLOGY  AND  PATHOLOGY  OF  MAN. 
BY  DR.  J.  FRANZ  SIMON. 

TRANSLATED  AND   EDITED  BY 

GEORGE  E.  DAY,  M.  A.  &  L.  M.  CANTAB.,  &c. 

With  plates.    In  one  octavo  volume,  of  over  seven  hundred  pages,  sheep,  or  in  two  parts,  boards. 

This  important  work  is  now  complete  and  may  be  had  in  one  large  octavo  volume.  Those  who  obtained  the 
first  part  can  procure  the  second  separate. 

"No  treatise  on  physiological  chemistry  approaches,  in  fulness  and  accuracy  of  detail,  the  work  which 
stands  at  the  head  of  this  article.  It  is  the  production  of  a  man  of  true  German  assiduity,  who  has  added  to  his 
own  researches  the  results  of  the  labors  of  nearly  every  other  inquirer  in  this  interesting  branch  of  science— 
The  death  of  such  a  laborer,  which  is  mentioned  in  the  preface  u>  the  work  as  haying  occurred  prematurely  m 
1842,  is  indeed  a  calamity  to  science.  He  had  hardly  reached  the  middle  term  of  life,  and  yet  had  made  himself 
known  all  over  Europe,  and  in  our  country,  where  his  name  has  been  familiar  for  several  years  as  among  the 

most  successful  of  the  cultivators  of  the  Chemistry  of  Man It  is  a  vast  repository  of  facts  to  which  the 

teacher  and  student  may  refer  with  equal  satisfaction."— The  Western  Journal  of  Medicine  and  Surgery. 

"The  merits  of  the  work  are  so  universally  known  and  acknowledged,  as  to  need  no  further  commendation 
at  our  hands." — JV.  Y.  Journal  of  Medicine  and  Surgery. 

THE  CHEMISTRY  OF  THE  FOUR  SEASONS— A  NEW  WORK. 
THE  CHEMISTRY  OF  THE  FOUR  SEASONS, 

SPRING,  SUMMER,  AUTUMN  AND  WINTER. 

AN   F.SSAY  PRINCIPALLY  CONCERNING   NATURAL    PHENOMENA    ADMITTING  OF  ILLUS- 
TRATION BY  CHEMICAL  SCIENCR  AND  1LLUSTR  ATI  NO-PASSAGES  OF  SCRIPTURE. 

BY  THOMAS  GRIFFITHS, 

Professor  of  Chemistry  in  the  Medical  College  of  St.  Bartholomew's  Hospital,  &c. 

In  One  very  neat  Volume,  royal  12mo.,  of  Four  Hundred  and  Fifty  large  Pages,  extra  cloth,  iMu* 
trated  urith  numerous  Wood-cuts. 


ANSTED'S  ANCIENT   WORLD — Just  Issued. 

THE  ANCIENT  WORLD;  OR,  PICTURESQUE  SKETCHES  OF  CREATION. 

BY  T.  D.  ANSfED,  M.A.,  F.R.S.,  F.G.S.,  &c. 

PROFESSOR  OF  GEOLOGY  IN  KING'S  COLLEGE,  LONDON. 

In  One  very  neat  volume,  fine  extra  cloth,  with  about  One  Hundred  and  Fifty  Illustrations. 
The  object  of  this  work  is  to  present  to  the  general  reader  the  chief  results  of  Geological  investigation  in 
•  simple  and  comprehensive  manner.    The  author  has  avoided  all  minute  details  of  geological  formations 
and  particular  observations,  and  has  endeavored  as  far  as  possible  to  present  striking  views  of  the  wonderl 
results  of  the  science,  divested  of  its  mere  technicalities.    The  work  is  printed  in  a  handsome  manner,  wita 
numerous  illustrations,  and  forms  a  neat  volume  for  the  centre-table. 


26  LEA  &  BLANCHARD'S  PUBLICATIONS. 

LECTURES  ON  THE  OPERATIONS  OF  SURGERY, 

AND  ON 

DISEASES  AND  ACCIDENTS  REQUIRING  OPERATIONS, 

DELIVERED   AT   UNIVERSITY    COLLEGE,   LONDON. 
BY  ROBERT  LISTON,  ESQ.,  F.  R.  S.,  &c. 

EDITED,     WITH     N  U  M  E  R  O  XI  8     ALTERATIONS     AND     ADDITIONS, 

BY  T.  D.  MUTTER,  M.D., 

Professor  of  Surgery  in  the  Jefferson  Medical  College,  Philadelphia. 

In  One  Large  and  Beautifully  Printed  Octavo  Volume* 

WITH  TWO  HUNDRED  AND  SIXTEEN  ILLUSTRATIONS  ON  WOOD. 

More  than  one-third  of  this  volume  is  by  Professor  Mutter,  embodying  elaborate  treatises  on 
Plastic  Operations,  Staphyloraphy,  Club-Foot,  Diseases  of  the  Eye,  Deformities  from  Burns,  ficc.&c. 


A  SYSTEM  OF  PRACTICAL  STJRCr£F*Y. 

BY  WILLIAM  FERGUSSON,  F.  R.  S.  E. 

SECOND   AMERICAN  EDITION,   REVISED  AND  IMPROVED. 
With  Two  Hundred  and  Fifty-two  Illustrations  from  Drawings  by  Bagg,  Engraved  by  Gilbert, 

With  Notes  and  Additional  Illustrations, 

BY    GEORGE    W.    NORRIS.M.    D.,  &c. 

In  one  beautiful  octavo  volume  of  six  hundred  and  forty  large  pages. 


THE  PRINCIPLES  AND  PRACTICE  OP 

OBSTETRIC  MEDICINE  AND  SURGERY, 

IN  REFERENCE  TO  THE  PROCESS!  OF  PARTURITION. 

ILLUSTRATED  BT 
One  hundred  and  forty-eight  f/arg-e  Figure*  on  55  lithographic  Plate** 

BY  FRANCIS  H.  RAMSBOTHAM,  M.  D.,  &c. 

A  NEW  EDITION,  FROM  THE  ENLARGED  AND  REVISED  LONDON  EDITION. 

In  one  large  imperial  octavo  volume,  well  bound. 

Philadelphia,  August  6th,  1845. 
MESSRS.  LEA.  &  BLA.NCHABD. 

GENTLEMEN  :— I  have  looked  over  the  proofs  of  Ramsbothara  on  Human  Parturition,  with  its  important  im- 
provements, from  the  new  London  edition. 

This  Work  needs  no  commendation  from  me,  receiving,  as  it  does,  the  unanimous  recommendation  of  the 
British  periodical  press,  as  the  standard  work  on  Midwifery;  "chaste  in  language,  classical  in  composition, 
happy  in  point  of  arrangement,  and  abounding  in  most  interesting  illustrations." 

To  the  American  public,  therefore,  it  is  most  valuable— from  its  intrinsic  undoubted  excellence,  and  as  being 
the  best  authorized  exponent  of  British  Midwifery.  Its  circulation  will,  I  trust,  be  extensive  throughout  our 
country. 

There  is,  however,  a  portion  of  Obstetric  Science  to  which  sufficient  attention,  it  appears  to  me,  has  not  been 
paid.  Through  you,  I  have  promised  to  the  public  a  work  on  this  subject,  and  although  the  continued  occupa- 
tion of  my  time  and  thoughts  in  the  duties  of  a  teacher  and  practitioner  have  as  yet  prevented  ihe  fulfilment  of 
the  promise,  the  day,  I  trust,  is  not  distant,  when,  under  the  hope  of  being  useful,  I  shall  prepare  an  account  of 
the  MECHANISM  OF  LABOR,  illustrated  by  suitable  engravings,  which  may  be  regarded  as  an  addendum  to  the 
standard  works  of  Rams  both  am,  and  our  own  Dewees. 

Very  respectfully,  yours, 

HUGH  L.  HODGE,  M.D., 
Professor  of  Obstetrics,  SfC.  8?c.,  in  the  University  of  Pennsylvania,. 


PROFESSOR  CHAPMAN'^'  WORKS  ON  PRACTICE. 

A  COMPENDIUM  ofLECTURES  ON  THE 

THEORY   AND    PRACTICE  OF    MEDICINE. 

DELIVERED   BY  PROFESSOR  CHAPMAN  IN  THE  UNIVERSITY  OF  PENNSYL- 
VANIA.   PREPARED,  WITH   PERMISSION,  FROM  DR.  CHAPMAN'S  MA- 

NUSCRIPTS,  AND  PUBLISHED  WITH  HIS  APPROBATION, 
By  N.  D.  BENEDICT,  M.  D.    In  one  very  neat  octavo  volume. 

ftjT  This  work  contains  the  diseases  not  treated  of  in  ihe  two  following. 

LECTURES  ON  THE  MORE  IMPORTANT  DISEASES  OF  THE 

THORACIC  AND  ABDOMINAL  VISCERA. 

Delivered  in  the  University  of  Pennsylvania,  by  N.  CHAPMAN,  M.  D.,  Professor  of  the  Theory 
and  Practice  of  Medicine,  &c.    In  one  volume,  octavo. 


LECTURES  ON  THE  MORE  IMPORTANT 

ERUPTIVE  FEVERS,  HEMORRHAGES  AND  DROPSIES, 

AND  ON  GOUT  AND  RHEUMATISM, 

Delivered  in  the  University  of  Pennsylvania  by  N.  CHAPMAN,  M.  D.,  Professor  of  the  Theory 
and  Practice  of  Medicine,  &c.  &c.    In  one  neat  octavo  volume. 


LEA  &  BLANCHARD'S  PUBLICATIONS.  •        27 

A  NEW  MEDICAL  DICTIONARY. 
In  one  Volume,  large  12mo,,  now  ready,  at  a  low  price, 

A  DICTIONARY  OF 

THE    TERMS    USED    IN    MEDICINE 

AND 

THE  COLLATERAL  SCIENCES; 

BY  RICHARD  D.  HOBLYN,  A.  M.,  OXON. 
FIRST    AMERICAN,    FROM    THE    SECOND    LONDON    EDITION. 

REVISED,  WITH  NUMEROUS  ADDITIONS, 

BY  ISAAC  HAYS,  M.  D., 

Editor  of  the  American  Journal  of  the  Medical  Sciences. 

A  NEW  ANlHx)^^  FEVERS. 


FEVERS; 

THEIR  DIAGNOSIS,  PATHOLOGY  AND  TREATMENT. 

PREPARED  AND  EDITED  WITH  LARGE  ADDITIONS, 

FROM  THE  ESSAYS  ON  FEVER  IN 

TWEEDIE'S  LIBRARY  OF  PRACTICAL  MEDICINE, 
BY  MEREDITH  CLYMER,  M.  D., 

Professor  of  the  Principles  and  Practice  of  Medicine  in  Franklin  Medical  College,  Philadelphia  ; 

Consulting  Physician  to  the  Philadelphia  Hospital;  Fellow  of  the  College  of  Physicians  ,  £c.  £c. 

In  one  octavo  volume  of  600  pages. 

THE  SURGICAL  WORKS  OF  SIR  ASTLEY  COOPER. 

THE  ANATOMY  AND  SURGICAL  TREATMENT  OF 

AIBB©MHHAIL    El  IE  IB  M  HA  0 

B*  SIR  ASTLEY  COOPER,  BART. 

Edited  by  C.  ASTON  KEY,  Surgeon  to  Guy's  Hospital,  &c. 

In  one  large  imperial  8vo.  volume,  with  over  130  Lithographic  Figures. 

ON  THE  STRUCTURE  AND  DISEASES  OF  THE  TESTIS. 

Illustrated  by  120  Figures.    From  the  Second  London  Edition. 

BY  BRANSBY  B.  COOPER,  ESQ. 
AND  ALSO  ON  THE  ANATOMY  OF  THE  THYMUS  GLAND. 

Illustrated  by  fifty-seven  Figures. 
The  two  works  together  in  one  beautiful  imperial  octavo  volume,  illustrated  with  twenty-nine  plates. 

ANATOMY  AND   DISEASES  OP  THE  BREAST,  &c. 

WJIS  LARGE  AND  BEAUTIFUL  VOLUME  CONTAINS  THE  ANATOMY  OF  THE  BREAST 
THE    COMPARATIVE    ANATOMY    OF   THE    MAMMARY    GLANDS;    ILLUSTRA- 
TIONS OF  THE  DISEASES  OF  THE  BREAST  ; 

And  Twenty-five  Miscellaneous  Surgical  Papers,  now  first  published  in  a  collected  form. 

BY  SIR  ASTLEY  COOPER,  BART.,  F.  R.  S.,  &c. 
The  whole  in  one  large  imperial  octavo  volume,  illustrated  with  two  hundred  and  fifty  -two  figures.  ' 

A  TREATISE  OS  DISLOCATIONS  AND  FRACTURES  OF  THE  JOINTS. 

BY  SIR  ASTLEY  COOPER,  BART.,  F.  R.  S.,  Sergeant  Surgeon  to  the  King,  &c. 

A  New  Edition  much  enlarged  ; 

EDITED  BY  BRANSBY  COOPER,  F.  R.  S.,  Surgeon  to  Guy's  Hospital. 
With  additional  observations  from  Professor  JOHN  C.  WARREN,  of  Boston. 

Witfc  numerous  Engravings  on  Wood,  after  designs  by  Bagg,  a  Memoir  and  a  splendid  Portrait  of  Sir  Astley 

In  one  octavo  volume. 


LEA  &  BLANCHARD'S  PUBLICATIONS. 


OTHER    WORKS 

VARIOUS  DEPARTMENTS 
MEDICINE  AND  SURGERY,  . 

PUBLISHED 

BY    LEA   &   BLANC  HARD. 

AMERICAN  JOURNAL  OF  THE  MEDICAL  SCIENCES.  Edited  by  Isaac  Hays,  M.D. 
Published  quarterly  at  $5  00  per  annum. 

ANDRAL  ON  THE  BLOOD.  Pathological  Haematology ;  an  Essay  on  the  Blood  in  Dis- 
ease. Translated  by  J.  F.  Meigs  and  Alfred  Stille.  In  one  octavo  volume,  cloth. 

ARNOTT'S  PHYSICS.  The  Elements  of  Physics  in  plain  or  non-technical  language.  A 
New  Edition.  Edited  by  Isaac  Hays,  M.  D.  In  1  vol.  8vo.,  sheep,  with  176  wood-cuts. 

ABERCROMBIE  ON  THE  STOMACH.  Pathological  and  Practical  Researches  on  Dis- 
eases of  the  Stomach,  Intestinal  Canal,  &c.  Fourth  Edition.  In  1  vol.  8vo.,  sheep. 

ABERCROMBIE  ON  THE  BRAIN.  Pathological  and  Practical  Researches  on  the  Dis- 
eases of  the  Brain  and  Spinal  Cord.  A  New  Edition.  In  one  octavo  volume,  sheep. 

ALISON'S  PATHOLOGY.  Outlines  of  Pathology  and  Practice  of  Medicine.  In  three 
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BENNET'S  PRACTICAL  TREATISE  ON  INFLAMMATION,  ULCERATION  AND 
INDURATION  OF  THE  NECK  OF  THE  UTERUS.  In  one  small  12mo.  volume, 
cloth. 

BIRD  ON  URINARY  DEPOSITS.  Urinary  Deposits,  their  Diagnosis,  Pathology  and  The- 
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BERZELIUS  ON  THE  KIDNEYS  AND  URINE,  in  1  vol.  8vo.,  cloth. 

BUCKLAND'S  GEOLOGY.  Geology  and  Mineralogy,  with  reference  to  Natural  Theology. 
A  Bridgewater  Treatise.  In  two  octavo  volumes,  with  numerous  maps,  plates,  &c. 

BUDD  ON  DISEASES  OF  THE  LIVER.  In  one  octavo  volume,  sheep,  with  beautiful 
colored  plates  and  numerous  woodcuts. 

BRIDGEWATER  TREATISES.  The  whole  complete  in  7  vols.  8vo.,  containing  Roget's 
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Habits  and  Instinct  of  Animals,  1  vol.  with  plates  ;  Prouton  Chemistry;  Chalmers  on  the 
Moral  Condition  of  Man;  Whewell  on  Astronomy  ;  Bell  on  the  Hand;  Kiddon  the  Phy- 
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BRIGHAM  ON  MIND,  &c.  The  Influence  of  Mental  Excitement  and  Mental  Cultivation, 
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BILLING'S  PRINCIPLES  OF  MEDICINE.  The  First  Principles  of  Medicine.  From  the 
Fourth  London  Edition.  In  one  octavo  volume,  cloth. 

CARPENTER'S  VEGETABLE  PHYSIOLOGY.  A  Popular  Treatise  on  Vegetable  Phy- 
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CLATER'AND  SKINNER'S  FARRIER.  Every  Man  his  own  Farrier.  Containing  the 
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From  the  28th  London  Edition.  Edked  by  Skinner.  In  one  12mo.  volume,  cloth. 

CLATER  AND  YOUATT'S  CATTLE  DOCTOR.  Every  Man  his  own  Cattle  Doctor. 
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Skinner.  With  Wood-cuts.  In  one  volume,  12mo. 

DURLACHER  ON  CORNS,  BUNIONS,  &c.  A  Treatise  on  Corns,  Bunions,  the  Dis- 
eases of  Nails,  and  the  General  Management  of  the  Feet.  In  one  12mo.  volume,  cloth. 

ELLIOTSON'S  MESMERIC  .CASES.    In  one  octavo  pamphlet. 

ELLIS'  FORMULARY.  The  Medical  Formulary,  being  a  collection  of  Prescriptions  de- 
rived from  the  Writings  and  Practice  of  the  most  eminent  Physicians  of  America  and 
Europe.  To  which  is  added  an  Appendix,  containing  the  usual  Dietetic  Preparations 
'  and  Antidotes  for  Poisons.  By  Benjamin  Ellis,  M.  D.  Eighth  Edition,  with  extensive 
Alterations  and  Additions.  By  Samuel  George  Morton,  M.  D.  In  one  neat  8vo.  volume. 

ESQUIROL  ON  INSANITY.  Mental  Maladies,  Considered  in  Relation  to  Medicine,  Hy- 
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GUTHRIE  ON  THE  BLADDER,  &c.  The  Anatomy  of  the  Bladder  and  Urethra,  and 
the  Treatment  of  the  Obstructions  to  which  those  passages  are  liable.  In  1  vol.  8vo. 

HARRIS  ON  MAXILLARY  SINUS.  Dissertation  on  the  Diseases  of  the  Maxillary  Sinus. 
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HUGHES  ON  THE  LUNGS  AND  HEART.    Clinical  Introduction  to  the  Practice  of 


LEA   &  BLANCHARD'S  PUBLICATIONS.  29 

Auscultation,  and  other  Modes  of  Physical  Diagnosis,  intended  to  simplify  the  study  of 
the  Diseases  of  the  Heart  and  Lungs.  By  H.  M.  Hughes,  M.D.,  &c.  "in  one  12mo. 
volume,  with  a  plate. 

BASSE'S  PATHOLOGICAL  ANATOMY.  An  Anatomical  Description  of  the  Diseases 
of  the  Organs  of  Circulation  and  Respiration.  Translated  and  Edited  by  Swaine.  In 
one  octavo  volume. 

INTRODUCTION  TO  PRACTICAL  ORGANIC  CHEMISTRY;  based  on  the  Works  of 
Brande.  Liebig  and,  others.  In  1  volume,  18mo.,  paper,  price  25  cents. 

INTRODUCTION  TO  VEGETABLE  PHYSIOLOGY.  With  reference  to  the  Works  of 
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KIRBY  ON  ANIMALS.  The  History,  Habits  and  Instinct  of  Animals.  A  Bridgewater 
Treatise.  In  one  large  volume,  8vo.,  with  plates. 

KIRBY  AND  SPENCE'S  ENTOMOLOGY.  An  Introduction  to  Entomology  ;  or  Elements 
of  the  Natural  History  of  Insects;  comprising  an  Account  of  Noxious  and  Useful 
Insects,  of  their  Metamorphosis,  Food,  Stratagems,  Habitations,  Societies,  Motions, 
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LAWRENCE  ON  RUPTURES.  A  Treatise  on  Ruptures,  from  the  fifth  London  Edition. 
In  one  octavo  volume,  sheep. 

MAN'S  POWER  OVER  HIMSELF  TO  PREVENT  OR  CONTROL  INSANITY.  One 
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MAURY'S  DENTAL  SURGERY.  A  Treatise  on  the  Dental  Art,  Founded  on  Actual  Ex- 
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J.  B.  Savier.  In  1  octavo  volume,  sheep. 

MULLER'S  PHYSIOLOGY.  Elements  of  Physiology.  Translated  by  Wm.  Bayly,  M.  D., 
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PRACTICAL  ORGANIC  CHEMISTRY.     18mo.,  sewed,  price  25  cents. 

PROUT  ON  THE  STOMACH.  On  the  Nature  and  Treatment  of  Stomach  and  Renal 
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POPULAR  MEDICINE,  BY  COATES.    In  one  octavo  volume,  sheep,  with  Wood-cuts. 

PHILIP  ON  INDIGESTION.    A  Treatise  on  Protracted  Indigestion.    In  1  vol.,  8vo. 

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30  LEA  &  BLANCHARD'S  PUBLICATIONS. 

A  TREATISE  ON  THE  DISEASES  OF  FEMALES," 

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Diseases  of  Females,  fyc.  SfC. 
TRANSLATED,  WITH  MANY  NOTES  AND  ADDITIONS, 

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LANDRETH'S  JOHNSON'S_GARDENERS'  DICTIONARY. 

JUST  READY. 

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CONTENTS    OF    THE 

AMERICAN  JOURNAL  OF  THE  MEDICAL  SCIENCES, 

For  *fprtf,  1847. 

MEMOIRS  AND  CASES. — Art.  I.  History  of  seven  cases  of  Pseudo-membranous  Laryngitis,  or  True  Croup. 
By  J.  F.  Meigs,  M.  D.  II.  Poisonous  Properties  of  the  Sulphate  of  Quinine.  By  VVm.  O.Baldwin,  M.  D.  III. 
Removal  of  the  Superior  Maxilla  for  a  tumour  of  the  antrum;  Apparent  cure.  Return  of  the  disease.  Second 
operation.  Sequel.  By  J.  Marion  Sims,  M.  D.  [With  a  wood-cut]  IV.  Laceration  of  the  Perineum.  By  John 
P.  Mettauer,  M.  D.  V.  Report  of  Cases  treated  in  Cincinnati  Commercial  Hospital.  By  John  P.  Harrison, 
M.  D.  VI.  Surgical  Cases.  By  Geo.  C.  Blackman,  M.  D.  [With  a  wood-cut.]  VII.  Cases  of  Paralysis 
peculiar  to  the  Insane.  By  Pliny  Earle,  M.  D.  VIII.  Contributions  to  Pathology ;  being  a  Report  of  Fatal 
Cases  taken  from  the  records  of  the  U.  S.  Naval  Hospital,  New  York.  By  W.  S.  W.  Ruschenberger,  M.  D. 
IX.  Case  of  Hydrops  Pericardii  suddenly  formed,  with  Remarks.  By  S.  Jackson,  M.  D.  X.  Case  of  Tuber- 
cles in  the  pericardium,  vena  cava,  columnse  carnese,  pleura,  lungs,  liver,  &c.,  with  Meningitis.  By  J.  D. 
Trask.  M.  D.  XI.  On  letting  Blood  from  the  Jugular  in  the  Diseases  of  Children.  By  Charles  C.  Hildreth, 
M.D. 

REVIEW.— XII.  Lectures  on  Subjects  connected  with  Clinical  Medicine ;  comprising  Diseases  of  ttee 
Heart.  By  P.  M.  Latham,  M.  D. 

BIBLIOGRAPHICAL  NOTICES. — XIII.  Green  on  Diseases  of  the  Air  Passages.  XIV.  Condie  on  the  Diseases  of 
Children.  Second  edition.  XV.  Royle's  Materia  Medica  and  Therapeutics.  Edited  by  Carson.  XVI.  Vogel's 
Pathological  Anatomy  of  the  Human  Body.  Translated,  with  additions,  by  George  E.  Day.  XVII.  Trans- 
actions of  the  College  of  Physicians  of  Philadelphia.  From  September  to  November,  1846,  inclusive. 
XVIII.  Wharton  Jones  on  the  Principles  and  Practice  of  Ophthalmic  Medicine  and  Surgery.  Edited  by 
Isaac  Hays,  M.  D.  XIX.  Wood  on  the  Practice  of  Medicine.  XX.  Wernher's  Manual  of  General  and 
Special  Surgery.  XXI.  Baumgarten's  Surgical  Almanac  for  the  years  1&44  and  1845.  XXII.  Wilson's 
System  of  Human  Anatomy,  General  and  Special.  Third  American  from  the  third  London  edition.  Edited 
by  Paul  B  Goddard,  M.  D.  XXIII.  Von  Behr's  Handbook  of  Human  Anatomy,  General,  Special  and 
Topographical.  Translated  by  John  Birkett 


LEA  &  BLANCH ARD'S  PUBLICATIONS.  31 

Contents  of  the  Medical  Journal  Continued. 
QUARTERLY    RETROSPECT, 

A  SUMMARY  OF  THE  IMPROVEMENTS  AND  DISCOVERIES  IN  THE  MEDICAL  SCIENCES 

FOREIGN  INTELLIGENCE—  ANATOMY  AND  PHYSIOLOGY—!.  Quelcett  on  Intimate  Structure  of  Bone.  2.  Meckel 
on  Process  of  Secretion.  3.  Blondloton  the  Properties  of  the  Bile.  4.  Bainbriggeon  Supplementary  Spleen, 
death  from  the  patient  being  placed  in  the  supine  position.  5.  Robinson  on  the  Nature  and  Source  of  the 
contents  of  the  Fcetal  Stomach.  6.  Prof.  Bischoffon  ihe  Absorption  of  Narcotic  Poisons  by  the  Lymphatics. 

MATERIA  MEDICA  AND  PHARMACY.— 7.  Battley  on  Syrup  of  Iodide  and  Chloride  of  Iron.  8.  Ricord  on  Bro- 
mide of  Potassium  as  a  substitute  for  the  Iodide.  9.  Voillemier  on  Santonine.  10.  Guibourt  on  the  changes 
of  composition  which  the  Tincture  of  Iodine  undergoes  in  keeping.  11.  Melion  on  the  Action  of  the  Acetate 
of  Morphia  on  Children. 

MEDICAL  PATHOLOGY  AND  THERAPEUTICS  AND  PRACTICAL  MEDICINE.— 12.  Bennett  on  Anormal  Nutrition 
and  Diseases  of  the  Blood.  13.  Rostan  on  Acute  Spinal  Myelitis.  14.  Rostan  on  Curability  of  Hypertrophy 
of  the  Heart.  15.  CVisp  on  Rupture  of  the  left  Ventricle  of  the  Heart.  16.  Francis  on  Aneurism  of  the  Basi- 
lar  Artery.  17.  Lombard's  Observations  on  Sudden  deaths,  probably  dependent  on  Diseases  of  the  Heart 
and  large  Blood-vessels.  18.  Carson  on  Obliteration  of  the  Vena  Cava  Descendens.  19.  Thompson  on 
Treatment  of  Chronic  Bronchitis  and  Bronchial  Asthma.  20.  Miihlbauer's  Microscopic  Researches  on  the 
Absorption  of  Pus.  21.  Briquet  on  Mercurial  Ointment  in  Variola.  22.  Bell  on  Rupture  of  Lateral  Sinus  of 
Dura  Mater.  23.  Watts  on  Tubercles  in  Bones.  24.  Gendrin  on  Hysterical  Affections.  25.  Cottereau's 
Remedy  for  Toothache.  26.  Prof  Trousseau  on  Anatomy  of  Pneumonia  in  Infants.  27.  Volz  on  Hooping 
Cough  an  Exanthemata.  28.  Crisp  on  Infantile  Pleurisy.  29.  Youl  on  Abscess  of  the  Brain  in  a  Child.  30. 
Trousseau  on  the  Employment  of  Nux  Vomica  in  the  Treatment  of  St.  Vitus'  Dance. 

SURGICAL  PATHOLOGY  AND  THERAPEUTICS  AND  OPERATIVE  SURGERY. — 31.  Prof.  Syme  on  Amputation  at 
the  Shoulder  Joint  for  Axillary  Aneurism.  32.  Whipple  on  Amputation  at  the  Hip  Joint.  33.  Prof.  Ehr- 
mann on  Successful  Extirpation  of  a  Polypous  Tumour  of  the  Larynx.  34.  Bellingham  on  Compression  in 
Aneurism.  35.  Orr's  Case  of  Tracheotomy.  36.  Holmes  Coote  on  Cancer  of  the  Breast  in  the  Male.  37. 
Moore  on  Gunshot  wound  of  the  Lung,  where  the  ball  lodged  fifty  years.  38.  On  the  Employment  of  Iodide 
of  Potassium  in  the  Treatment  of  Syphilis.  39.  Application  ofice  in  the  treatmentof  injuries.  40.  Lenoiron 
Ununited  Fracture  successfully  treated  by  Acupuncturation.  41.  Prof.  Syme  on  Amputation  of  the  Thigh. 
42.  Curling's  Case  of  Fatal  Internal  Strangulation  caused  by  a  cord  prolonged  from  a  Diverticulum  of  the 
Ileum.  43.  Golding  Bird  and  John  Hilton  on  Case  of  Internal  Strangulation  of  Intestine  relieved  by  Opera- 
tion. 44.  Fergussonon  Strangulated  Congenital  Hernia  in  an  infant  seventeen  days  old,  requiring  opera- 
tion. 45.  Guersant,  Jr.,  on  Surgical  Treatment  of  Croup.  46.  Geoghegan  on  Partial  Amputation  of  the  Foot. 
47.  Report  of  a  Committee  of  the  Surgical  Society  of  Ireland,  relative  to  the  use  and  effects  of  Sulphuric 
Ether. 

OPHTHALMOLOGY.— 48.  Prof.  Jacob  on  Foreign  Bodies  in  the  Eye.  49.  Dixon's  Remarkable  Case  of  Injury 
of  the  Eye.  50.  Szokahkion  Obscurations  of  the  Cornea  in  their  Histological  relations  with  reference  to  the 
Practice  of  Ophthalmic  Surgery.  51.  Berncastle  on  Amauro  sis  from  Hydatid  Cyst  in  the  Brain. 


MIDWIFERY.— 52.  Robiguet  on  Remarkable  case  of  spontaneous  rupture  of  the  Uterus  during  labour — Re- 
Chaptois*  Case  of  Vaginal  Entero-hysterocele  reduced  by  taxis,  and  maintained  in  place 


covery.    53.  Le 


by  the  introduction  of  sponges  in  the  Vagina.  54.  Kuhne  on  Rupture  of  the  Uterus— abdominal  section — 
recovery.  55.  Czajewski  on  Wound  of  the  Gravid  Uterus — premature  delivery — peritonitis— recovery.  56. 
Bennett  on  Inflammatory  Ulceration  of  the  Cervix  Uteri  during  Pregnancy,  and  on  its  Influence  as  a  Cause 
of  Abortion.  57.  Caesarian  Operation  performed  by  Mr.  Skey,  at  St.  Bartholomew's  Hospital,  the  patient 
being  rendered  insensible  by  ether.  58.  Pochhammer  on  Congenital  protrusion  of  the  Liver  through  the 
umbilical  ring.  59.  Caesarian  Section.  60.  Roux  on  Lacerated  Perineum.  61.  Depaul  on  Asphyxia  neona- 
toruin.  62.  Klencke  on  Diet  in  Infancy. 

MEDICAL  JURISPRUDENCE  AND  TOXICOLOGY.— 63.  Taylor  on  Contested  identity  determined  by  the  teeth. 
64.  Blake  on  Poisons.  65.  Delirium  Tremens  in  an  Infant.  66.  Hamilton  on  the  Echites  Suberecta.  67. 
Dupasquier  on  Vapours  of  Phosphorus,  Lucifer  Matches.  68.  Thompson  on  the  mode  of  testing  the  presence 
of  minute  quantities  of  Alcohol.  69.  Invalidity  of  a  Contract  made  by  a  Lunatic.  70.  Procuring  of  Abortion. 
71.  Lepage's  Case  of  Poisoning  by  Arsenic  relieved  by  the  use  of  Magnesia.  72.  Sale  of  Poisonous  Sub- 
stances. 

MEDICAL  EDUCATION.— 73.  The  Edinburgh  Statutes  regarding  the  Degree.  74.  Medical  Organization  in 
Spain. 

FOREIGN  CORRESPONDENCE.— Letters  to  the  Editor  from  London.  Sulphuric  Ether  in  Surgical  Operations 
at  Vienna. 

AMERICAN  INTELLIGENCE— ORIGINAL  COMMUNICATIONS.— Parfcmon's  Anatomical  Anomaly.  Tyler"1*  Ante- 
version  of  the  Womb  with  adhesion  of  Os  Uteri  to  body  of  4th  Lumbar  Vertebra,  &c. 

DOMESTIC  SUMMARY  — Beck  on  Effects  of  Mercury  on  the  Young  Subject.  Brainard  on  Amputation  for 
Scrofulous  Diseases  of  the  Joints.  Baker  on  Case  of  Vicarious  Menstruation  from  an  Ulcer  on  the  right 
Mamma.  Allen  on  Singular  case  of  laceration  of  the  Broad  Ligaments.  McLean  on  Blindness  caused  by 
the  use  of  Sulphate  of  Quinine.  Harrison's  Speculations  on  the  Cause  of  Yellow  Fever.  Herrickon  Foreign 
Bodies  in  the  Organs  and  Tissues  of  the  Body.  Swett  on  Case  of  Empyema  in  which  the  operation  for  Para- 
centesis  Thoracis  failed  from  a  cause  not  generally  noticed.  M'Pheeters  on  Rheumatism,  with  Hypertrophy 
of  both  eyes.  Draper  on  the  Cause  of  the  Circulation  of  the  Blood.  Little  on  Ischuria  Renalis.  Hogan  on 
Strychnine  in  Chorea.  Deaderick  on  Excision  of  the  Inferior  Maxillary  Bone  for  Osteo-Sarcoma.  Cain  on 
Imperforate  Prepuce.  Couper  on  Medical  Schools  of  the  United  States.  Warren  on  Inhalation  of  Ether. 
Burwell  on  Absence  of  one  Kidney.  Brainard  on  Dislocation  of  the  Elbow.  Gilman  on  Presentation  of 
the  shoulder,— prolapsed  Cord,— cord  not  pulsating,  yet  child  born  alive.  National  Medical  Convention. 
Delegates  to  National  Medical  Convention.  Arrangements  for  the  Meeting  of  the  National  Medical  Con- 
vention. Resignation  of  Professor  Warren.  New  Medical  Books. 

LEA    &  BLANCHARD,   Philadelphia. 

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Philadelphia,  May,  1847 


33  LEA  &  BLANCHARD'S  PUBLICATIONS. 

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ONE    GIVEN    GRATIS. 
THE 

AMERICAN  JOURNAL  OF  THE  MEDICAL  SCIENCES, 

EDITED  BY  ISAAC  HAYS,  M.  D., 

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RETROSPECT   AND  ABSTRACT 

OF  THE  PROGRESS  OF  THE  MEDICAL  SCIENCES, 

CAREFULLY  COLLECTED  FROM  ALL  THE 
FOREIGN    AND    DOMESTIC    JOURNALS. 

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of  GREAT  BRITAIN,  FRANCE,  GERMANY,  DENMARK,  ITALY,  the  EAST  INDIES,  &c.,  beside* 

ALL  THE  AMERICAN    JOURNALS: 

And  especial  attention  will  be  given  to  make  it  as  complete  a  digest  as  possible,  of  all  the 

IMPROVEMENTS  AND  DISCOVERIES  IN  MEDICAL  SCIENCE. 
Besides  this,  subscribers  have  the  advantage  of 

THE    XVZONTHljir    NEWS, 

Which  furnishes  the  lighter  and  floating  information,  and  embraces  important  books  for 

The   Library  Department. 

The  work  now  passing  through  its  columns  is 

TODD   AND   BOWMAN'S 
PHYSIOLOGICAL  ANATOMY  AND  PHYSIOLOGY  OF  MAN, 

WITH  NUMEROUS  LARGE  AND  BEAUTIFUL  WOOD-CUT!!. 

Each  work  in  the  Library  is  regularly  paged,  so  as  to  be  bound  separately. 


|C29c 
1847 


Carpenter,  W.B.    65113 
Principles  of  human 
iology-   3d  American- 
ed. 


